Good Afternoon:
There is actually a storm "out there" today, this Wednesday afternoon. Temperatures are falling towards chilly levels, and they won't recover until Shabbat afternoon. However, they will begin a steep climb into late next week, which will have many folks saying: "there ain't no more winter here." In a sense, they would be correct. As noted, the break-up of the polar vortex has broken our string of rainy weeks and chilly weather, and we've been for the most part under the influence of high pressures ridges, which have and will bring warm southerly breezes.
However, they say the bigger the wave the bigger they break. While technically true, we're referring to winter wave patterns rather than summer wave patterns (when the only thing breaking are waves on the beach). The timing for this "breaking" atmospheric wave should be the end of next week and/or early the following week. It's not really a breaking wave, but rather the possible arrival of a deep and cold trough of air following the "ridge" in the wave pattern that could turn us back towards winter, at least for a few days. In a sense, the stronger the ridge, the stronger the trough on its backside.
Ever since the break-up of the polar vortex, things just haven't been the same for me. Besides the loss of popularity and interest in the weather (let alone myself), strange things have been happening (at least to me). It started out not so innocently enough with a missing (green) sweatshirt. This is a sweatshirt I never take off outside of the house, yet it is not to be found anywhere at all. At the same time, an old (for cleaning) skirt of my wife's disappeared. These events were followed by numerous pieces of silverware dropping from plates, bowls, etc, culminating the other night in the screams of a glass cup shattering on the floor. Today a wind-blown Kippa went sailing from head only to land in the only puddle of water around (and leftover cleaning water at that). I can understand the other things happening, but the last shouldn't happen to me. It got so bad I sent my (brave) daughter to the basement to see if there was some malicious person conducting some electromagnetic wave bending experiments. Come to think of it, I never heard back from her.
And then there's the question of whether to take an antibiotic for a sinus infection. From what my doctor tell's me: "real men don't take antibiotics." (If you're a feminist, then real women don't take them either). Rather than the question being: how long do you wait, you begin to wonder if you've got what it takes to save the world from the over-prescription of antibiotics. If you don't, you might feel better, but you'll definitely feel guilty. Everyone you see seems to say: "if you just waited another miserable day you would have been better on your own."
We all know that the over-prescription of antibiotics has led to an increase in resistance to antibiotics, if not a complete insensitivity to them among our most dangerous "superbugs." However, there is another reason that we should treat the bacteria within us (or micro-biome) with greater respect. It turns out that our diet (if not the antibiotics we take) affects the microbiome composition in our small intestine (https://www.nytimes.com/2019/01/28/health/microbiome-brain-behavior-dementia.html?). These bacteria don't just help us digest last night's "veggie burger," they are able to send signals through the nerve endings of our intestines all the way to our brains. These signals have been shown to influence brain development, and even the development of brain disease, perhaps even Alzheimer's, depending on your diet.
So, when you ask yourself if you're a "real" man (or women), don't forget to ask yourself who's really calling the shots. Or, when they say you "feel it in your gut," we should consider taking this literally.
Barry Lynn
Wednesday, January 30, 2019
Thursday, January 24, 2019
Weather It Is (Quick Changes)
Good Evening:
There are quick changes in store for us. However, when all is said and done it may simply be more "sound" than fury. Temperatures several hundred meters above our mountain tops are falling into tonight, and then rising into Shabbat, and then falling into Monday, and then rising into Wednesday, and then falling into Friday. If you're not feeling a bit of vertigo, then I am.
Both storms next week may bring periods of rain, but then again, they may not.
Why the uncertainty? The break up of the polar vortex into spinning vortices has led to an injection of artic air energy into our mid-latitude atmospheric system, creating difficulties for global forecast models as they peer into the future.
People keep telling my wife that they heard it is going to snow. I am not really sure why they are saying this, but the same thing happened last time it snowed -- someone, somewhere, is starting rumours and like feathers on the wind they get blown here and there.
While some folks were spreading rumours, I was sitting "Shiva" for a lost sister. She was actually lost to me years ago, as she suffered some calamity while growing in my mother's womb. There was no obvious reason why this happened or even what happened, but the result was that I was born into the world as a "make-up" baby. So, in someway I owe my life to her lack of life -- she was alive, but she didn't have the opportunity to live.
Quite frankly, I found it strange to sit shiva for someone I really didn't know. Yet, the people who visited (and I thank them for doing so) were quite understanding and encouraging. I went from feeling that I was committing "Shiva Fraud" to doing something meaningful for both my second sister and myself, and hopefully my parents as well.
I have to say that when I experience the kindness of my fellow citizens I really feel better about being here, and perhaps I can have more patience for those who seem to live in their own world -- whether they are cutting in front at the border control point or cutting you off on the road. My guess is that the number of good folks far out weight the bad ones, but the acts of kindness often occur far from the public eye.
Here's hoping for better news and as someone said: my sister Nancy has been saved from further suffering. It's true, but I wish that it would never have been.
But, then who would write this column?
Barry Lynn
There are quick changes in store for us. However, when all is said and done it may simply be more "sound" than fury. Temperatures several hundred meters above our mountain tops are falling into tonight, and then rising into Shabbat, and then falling into Monday, and then rising into Wednesday, and then falling into Friday. If you're not feeling a bit of vertigo, then I am.
Both storms next week may bring periods of rain, but then again, they may not.
Why the uncertainty? The break up of the polar vortex into spinning vortices has led to an injection of artic air energy into our mid-latitude atmospheric system, creating difficulties for global forecast models as they peer into the future.
People keep telling my wife that they heard it is going to snow. I am not really sure why they are saying this, but the same thing happened last time it snowed -- someone, somewhere, is starting rumours and like feathers on the wind they get blown here and there.
While some folks were spreading rumours, I was sitting "Shiva" for a lost sister. She was actually lost to me years ago, as she suffered some calamity while growing in my mother's womb. There was no obvious reason why this happened or even what happened, but the result was that I was born into the world as a "make-up" baby. So, in someway I owe my life to her lack of life -- she was alive, but she didn't have the opportunity to live.
Quite frankly, I found it strange to sit shiva for someone I really didn't know. Yet, the people who visited (and I thank them for doing so) were quite understanding and encouraging. I went from feeling that I was committing "Shiva Fraud" to doing something meaningful for both my second sister and myself, and hopefully my parents as well.
I have to say that when I experience the kindness of my fellow citizens I really feel better about being here, and perhaps I can have more patience for those who seem to live in their own world -- whether they are cutting in front at the border control point or cutting you off on the road. My guess is that the number of good folks far out weight the bad ones, but the acts of kindness often occur far from the public eye.
Here's hoping for better news and as someone said: my sister Nancy has been saved from further suffering. It's true, but I wish that it would never have been.
But, then who would write this column?
Barry Lynn
Thursday, January 17, 2019
Weather It Is (What's Ahead?)
Good Afternoon:
In a season of frequent rains and storms, last night's storm was a storm to remember. If not the wind (Severe Gale), then the rain (flooding), if not the rain then the thunder and hail, and if not the rain and hail, then it was the brightness of the snow as lightning lit up the sky (in thunder snow). For those who are wondering, there was a light covering in Jerusalem to anywhere from 8 to 15+ cm in Gush Etzion.
It was a week of nail-biting temperatures, as the models first indicated that the coldest air of the decade would freeze our toes off, but in the end we were left with the question: would it snow? Both Jerusalemites and Gush-Etzion-ites can answer: yes it did.
Almost as if to say: "I'm worn out," the temperatures will climb wearily from the low single digits to the middle single digits over a week's of time. There will be -- actually -- an absence of weather, and your weather man (or women) can take a well needed break.
The weather may not really be tired, but the polar vortex is splitting, which cause ripple effects in our winter wave pattern that has brought all these storms (and a rainy winter, so far).
Looking at the long range forecast, there is the potential for a return to colder weather, but perhaps not until the week after next. This will seem like a long time for those who have gotten used to winter like winters past.
Barry Lynn
P.S. I've uploaded some pictures before (with dust in the clouds) and during the storm. Here's a link to our snow (nighttime) video: https://www.youtube.com/watch?v=9yXY2wt54Lc
In a season of frequent rains and storms, last night's storm was a storm to remember. If not the wind (Severe Gale), then the rain (flooding), if not the rain then the thunder and hail, and if not the rain and hail, then it was the brightness of the snow as lightning lit up the sky (in thunder snow). For those who are wondering, there was a light covering in Jerusalem to anywhere from 8 to 15+ cm in Gush Etzion.
It was a week of nail-biting temperatures, as the models first indicated that the coldest air of the decade would freeze our toes off, but in the end we were left with the question: would it snow? Both Jerusalemites and Gush-Etzion-ites can answer: yes it did.
Almost as if to say: "I'm worn out," the temperatures will climb wearily from the low single digits to the middle single digits over a week's of time. There will be -- actually -- an absence of weather, and your weather man (or women) can take a well needed break.
The weather may not really be tired, but the polar vortex is splitting, which cause ripple effects in our winter wave pattern that has brought all these storms (and a rainy winter, so far).
Looking at the long range forecast, there is the potential for a return to colder weather, but perhaps not until the week after next. This will seem like a long time for those who have gotten used to winter like winters past.
Barry Lynn
P.S. I've uploaded some pictures before (with dust in the clouds) and during the storm. Here's a link to our snow (nighttime) video: https://www.youtube.com/watch?v=9yXY2wt54Lc
Wednesday, January 16, 2019
Weather It Is (Winter Storm Warning)
Good Evening:
Our update based on the 6 UTC GFS showed snow in Gush Etzion extending from Hebron to Efrat, while the latest update using GFS 12 UTC extends a light accumulation into Jerusalem.
Forecast amounts are also larger in Gush Etzion, with between 15 to 20 cm forecast.
The totals will depend on the intensity of the cluster of thunderstorms as they move eastward during the next few hours (see below).
Forecast snow amounts included, as well as snap-shot from the Israeli Total Lightning Network (ITLN). The green shading is a depiction of radar reflectivity based on lightning intensity ("PulseRad").
Our update based on the 6 UTC GFS showed snow in Gush Etzion extending from Hebron to Efrat, while the latest update using GFS 12 UTC extends a light accumulation into Jerusalem.
Forecast amounts are also larger in Gush Etzion, with between 15 to 20 cm forecast.
The totals will depend on the intensity of the cluster of thunderstorms as they move eastward during the next few hours (see below).
Forecast snow amounts included, as well as snap-shot from the Israeli Total Lightning Network (ITLN). The green shading is a depiction of radar reflectivity based on lightning intensity ("PulseRad").
Weather It Is (Storm Update)
Good Morning:
There have been some small changes to the forecast.
Keep in mind that the severe winds combined with precipitation, including snow, should lower visibility, perhaps creating "white-out" conditions as the evening progresses.
However, because the lowest level cold air is moving in more from the west than north, the surface temperatures will be hard pressed to reach freezing. Snow will mostly melt in Jerusalem. The percentage chances for snow are based on our ensemble forecast.
Between 3 this afternoon and 5 this afternoon rain should arrive in Jerusalem and then mix with graupel (ice) and a bit of snow as the sky darkens. Temperatures will drop by several degrees from about 8 or 9 degrees Celcius to about 2 or 3 degrees depending on elevation (750 m to 850 m, respectively). Rain, graupel, and some snow should continue until about 8 P.M, when temperatures are forecast to turn colder. The chance of snow is 30%. From 8 until 11 P.M, there are indications that a heavier downburst of precipitation combined with evaporative cooling of the surface layer will lead to the formation of an isothermal layer. During this time, the mixture should become predominately snow and accumulate on colder surfaces (like cars and/or sidewalks). However, if the snow briefly sticks it should quickly melt. The chance of snow is 60%. The precipitation should taper to light rain (or a rain/snow mixture) towards midnight.
In Gush Etzion, temperatures should be a degree or two colder, and there is a greater likelihood that snow will accumulate. The chance of snow between 5 PM and 8 PM, is 60 to 70%. The chance of snow between 8 and 11 P.M is 100%. However, the accumulation will be very elevation dependent; the forecast shows the snow melting in lower areas like Efrat, while accumulating in surrounding areas several centimeters. Of course, half to 1 degree variation in temperatures will affect the accumulation, and this is within the range of model error.
Otherwise...
Gale force winds will become a "Severe Gale" late this evening and night, with winds exceeding 41 knots both along the central to southern coasts and inland to the central mountains (75 to 88 km/h). There is a chance that winds will exceed 48 knots, approaching 100 km/h (especially along the coastal areas and in the mountainous areas).
Our ensemble shows that the heaviest precipitation should fall in the central mountains, including Jerusalem from 17 IST until 23 IST, when temperatures in the lower, middle, and upper atmosphere should be at their coldest. The heavy precipitation should be accompanied by frequent lightning and hail and smaller ice.
Be well, and stay safe.
Barry Lynn
There have been some small changes to the forecast.
Keep in mind that the severe winds combined with precipitation, including snow, should lower visibility, perhaps creating "white-out" conditions as the evening progresses.
However, because the lowest level cold air is moving in more from the west than north, the surface temperatures will be hard pressed to reach freezing. Snow will mostly melt in Jerusalem. The percentage chances for snow are based on our ensemble forecast.
Between 3 this afternoon and 5 this afternoon rain should arrive in Jerusalem and then mix with graupel (ice) and a bit of snow as the sky darkens. Temperatures will drop by several degrees from about 8 or 9 degrees Celcius to about 2 or 3 degrees depending on elevation (750 m to 850 m, respectively). Rain, graupel, and some snow should continue until about 8 P.M, when temperatures are forecast to turn colder. The chance of snow is 30%. From 8 until 11 P.M, there are indications that a heavier downburst of precipitation combined with evaporative cooling of the surface layer will lead to the formation of an isothermal layer. During this time, the mixture should become predominately snow and accumulate on colder surfaces (like cars and/or sidewalks). However, if the snow briefly sticks it should quickly melt. The chance of snow is 60%. The precipitation should taper to light rain (or a rain/snow mixture) towards midnight.
In Gush Etzion, temperatures should be a degree or two colder, and there is a greater likelihood that snow will accumulate. The chance of snow between 5 PM and 8 PM, is 60 to 70%. The chance of snow between 8 and 11 P.M is 100%. However, the accumulation will be very elevation dependent; the forecast shows the snow melting in lower areas like Efrat, while accumulating in surrounding areas several centimeters. Of course, half to 1 degree variation in temperatures will affect the accumulation, and this is within the range of model error.
Otherwise...
Gale force winds will become a "Severe Gale" late this evening and night, with winds exceeding 41 knots both along the central to southern coasts and inland to the central mountains (75 to 88 km/h). There is a chance that winds will exceed 48 knots, approaching 100 km/h (especially along the coastal areas and in the mountainous areas).
Our ensemble shows that the heaviest precipitation should fall in the central mountains, including Jerusalem from 17 IST until 23 IST, when temperatures in the lower, middle, and upper atmosphere should be at their coldest. The heavy precipitation should be accompanied by frequent lightning and hail and smaller ice.
Be well, and stay safe.
Barry Lynn
Tuesday, January 15, 2019
Weather It Is (Evening Update)
Good Evening:
The forecast arrival of our severe winter storm is unchanged.
Gale force winds will become a "Severe Gale" late tomorrow evening and night, with winds exceeding 41 knots both along the central to southern coasts and inland to the central mountains (75 to 88 km/h). There is a chance that winds will exceed 48 knots, approaching 100 km/h (especially along the coastal areas and in the mountainous areas).
Our ensemble shows that the heaviest precipitation should fall in the central mountains, including Jerusalem from 17 IST until 23 IST, when temperatures in the lower, middle, and upper atmosphere should be at their coldest. The heavy precipitation should be accompanied by frequent lightning and hail and smaller ice.
Our deterministic highest resolution WRF forecast indicates that snow should arrive in Jerusalem and Gush Etzion after 1700 IST, but accumulate only in Gush Etzion 5 to 15 cm, depending on elevation.
The atmospheric temperatures are on average cold enough for snow at lower, middle, and upper levels for the highest mountainous areas, but surface temperatures remain too warm in Jerusalem for snow accumulation. Checking our ensemble forecast, we don't see enough variability in temperatures to consider that snow will accumulate were our coldest forecasts to verify.
Still, where there's snow in the air, there's hope that a heavy burst will whiten the ground.
Have a good night -- updates planned for tomorrow morning.
Barry Lynn
The forecast arrival of our severe winter storm is unchanged.
Gale force winds will become a "Severe Gale" late tomorrow evening and night, with winds exceeding 41 knots both along the central to southern coasts and inland to the central mountains (75 to 88 km/h). There is a chance that winds will exceed 48 knots, approaching 100 km/h (especially along the coastal areas and in the mountainous areas).
Our ensemble shows that the heaviest precipitation should fall in the central mountains, including Jerusalem from 17 IST until 23 IST, when temperatures in the lower, middle, and upper atmosphere should be at their coldest. The heavy precipitation should be accompanied by frequent lightning and hail and smaller ice.
Our deterministic highest resolution WRF forecast indicates that snow should arrive in Jerusalem and Gush Etzion after 1700 IST, but accumulate only in Gush Etzion 5 to 15 cm, depending on elevation.
The atmospheric temperatures are on average cold enough for snow at lower, middle, and upper levels for the highest mountainous areas, but surface temperatures remain too warm in Jerusalem for snow accumulation. Checking our ensemble forecast, we don't see enough variability in temperatures to consider that snow will accumulate were our coldest forecasts to verify.
Still, where there's snow in the air, there's hope that a heavy burst will whiten the ground.
Have a good night -- updates planned for tomorrow morning.
Barry Lynn
Weather It Is (A Storm Arrives)
Good Afternoon:
My daughter had one simple observation: it's too warm to snow. My wife called downstairs -- she thought it was suppose to snow today, Tuesday.
If my immediate family is confused, then I can well imagine the confusion among readers of this blog.
Moreover, this blog maybe over taken some news related to colder temperatures recently forecast.
Here's the summary:
1) Gale Warning for coastal and mountain areas.
2) Flood Risk in mountain/valley and northern areas.
3) Winter Storm Warning for the Golan Wednesday and Wednesday Night.
4) Winter Storm Warning for Gush Etzion for late Wednesday and Night, for 5 to 10 cm of snow.
5) Winter Storm Watch for Jerusalem.
I received an interesting explanation for why the lower atmosphere is not as cold as originally forecast. Simply put, the position of high and low pressure systems over Europe are somewhat displaced from their previous forecast position, shunting off to the east some of our previously mentioned extreme cold.
Nevertheless, we're not out of the woods yet. Currently, our forecast shows 5 to 10 cm of snow for Gush Etzion, with mixed snow, ice, and rain in Jerusalem. The strongest precipitation should fall in Jerusalem in the late afternoon and evening, and in Gush Etzion in the evening hours as the coldest air arrives both aloft and in the lower atmosphere.
Snow and ice, rather than just ice and rain should arrive in the evening hours, and continue past midnight. Forecast temperatures are a couple of degrees above freezing in Jerusalem, and a degree colder in Gush Etzion (depending on elevation). Hence, the snow is more likely to accumulate in Gush Etzion in the very late afternoon and evening (where 5 to 10 cm is forecast) compared to Jerusalem where only a coating may occur early in the evening (but melt very quickly).
The precipitation should last until morning, and will probably turn back to rain or a very wet snow in Gush Etzion by morning.
Based on an examination of global ensemble forecasts, the range of possible error suggests that there is a 20% chance of several centimetres of snow in Jerusalem. Currently, though, our highest resolution forecast based on the GFS newest version does not show an accumulation of snow in
Jerusalem. This could change with the next update, as the synoptic conditions are more favorable for snow in Jerusalem.
Elsewhere, a light coating of snow is forecast in the higher mountains surrounding Sefad. The lower Golan is forecast to have 10 to 15 cm, while the upper Golan should have up to half a meter.
Barry Lynn
My daughter had one simple observation: it's too warm to snow. My wife called downstairs -- she thought it was suppose to snow today, Tuesday.
If my immediate family is confused, then I can well imagine the confusion among readers of this blog.
Moreover, this blog maybe over taken some news related to colder temperatures recently forecast.
Here's the summary:
1) Gale Warning for coastal and mountain areas.
2) Flood Risk in mountain/valley and northern areas.
3) Winter Storm Warning for the Golan Wednesday and Wednesday Night.
4) Winter Storm Warning for Gush Etzion for late Wednesday and Night, for 5 to 10 cm of snow.
5) Winter Storm Watch for Jerusalem.
I received an interesting explanation for why the lower atmosphere is not as cold as originally forecast. Simply put, the position of high and low pressure systems over Europe are somewhat displaced from their previous forecast position, shunting off to the east some of our previously mentioned extreme cold.
Nevertheless, we're not out of the woods yet. Currently, our forecast shows 5 to 10 cm of snow for Gush Etzion, with mixed snow, ice, and rain in Jerusalem. The strongest precipitation should fall in Jerusalem in the late afternoon and evening, and in Gush Etzion in the evening hours as the coldest air arrives both aloft and in the lower atmosphere.
Snow and ice, rather than just ice and rain should arrive in the evening hours, and continue past midnight. Forecast temperatures are a couple of degrees above freezing in Jerusalem, and a degree colder in Gush Etzion (depending on elevation). Hence, the snow is more likely to accumulate in Gush Etzion in the very late afternoon and evening (where 5 to 10 cm is forecast) compared to Jerusalem where only a coating may occur early in the evening (but melt very quickly).
The precipitation should last until morning, and will probably turn back to rain or a very wet snow in Gush Etzion by morning.
Based on an examination of global ensemble forecasts, the range of possible error suggests that there is a 20% chance of several centimetres of snow in Jerusalem. Currently, though, our highest resolution forecast based on the GFS newest version does not show an accumulation of snow in
Jerusalem. This could change with the next update, as the synoptic conditions are more favorable for snow in Jerusalem.
Elsewhere, a light coating of snow is forecast in the higher mountains surrounding Sefad. The lower Golan is forecast to have 10 to 15 cm, while the upper Golan should have up to half a meter.
Barry Lynn
Monday, January 14, 2019
Weather It Is (A Storm Arrives And Then What?)
Good Evening:
Highlights:
Winter Storm Warning for the Hermon and Golan for Wednesday into Thursday.
High Wind Warning for Gale Force Winds.
Flood Risk from south-central Israel to northern Israel (with the heaviest rain occurring as one moves northward).
Winter Storm Watch for Gush Etzion and the Highest peaks around Jerusalem.
I am writing late because I spent the afternoon trying to find the last "Who" in "Whoville" who might be keeping quiet. The one who might the tip the balance in favor of those who want snow versus those who don't. I didn't find him (or her).
Hence, there is quite a conundrum. The forecast has changed quite substantially within the last couple of days. Instead of extreme cold in the lower levels and relatively mild temperatures aloft, the forecast is showing "snow" cold in the lower levels and extreme cold in the upper levels. This makes it less likely that temperatures will be cold enough for accumulating snow in Jerusalem. Snow, though, is still likely in the higher elevation of the Galilee and hills surrounding Sefad.
Moreover, there are large forecast differences between the new version of the Global Forecast System (GFS) and its old version (still in operational use). The new GFS produces a deep, wintertime trough over the eastern Mediterranean, similar to the ECMWF and Canadian model. So, in the discussion below, we're relying on the new GFS and our downscaled Weather Forecasting and Research (WRF) model based on it, rather than the old GFS.
The extreme cold in the upper levels is conducive to the production of "thunder-snow," which often leads to a snow accumulation when combined with cold lower atmospheric temperatures. However, our high resolution forecast is again showing that surface temperatures will remain above freezing in a saturated surface layer. This means -- again -- that snow will melt with the exception at the highest elevations of Gush Etzion. Folks even in Jerusalem should see snow, especially from noon Wednesday to about midnight Wednesday night, but it maybe hard pressed to stick around. Regardless, expect there to be elevation dependent icy conditions anytime during the height of the storm. Heavy rain and/or blowing snow could reduce visibility to only several meters.
In a previous blog I wrote that there are things we know and things we don't know. One of them was could one rely on the Global Ensemble Forecast System (GEFS) model forecasts after the individual forecasts converged to a tightly clustered group. In our case, we were wondering whether after the different forecast members of the ensemble converged to produce greater certainty would they as a "close-knit" group deviate from their previous forecast of extreme cold. The answer is in, and they have deviated. As noted, the upper levels have cooled off significantly from their previously shown values, but the lower levels have warmed up significantly. Whether this indicates a problem with model physic and numerical integration (or simply that the distribution of possible forecasts is not wide enough) is still an unknown.
What I hope to find out after a bit of research I am engaged in now is what is the probability that a forecast that is tightly clustered will occur as previously forecast some days in advance. This is on going research, and there is no clear answer yet. In other words, there are forecast probabilities and then there is the probability that the mean of the forecast will be within a certain range.
At the moment, no significant storms are shown for next week, which is a big change from the past several weeks.
Barry Lynn
Highlights:
Winter Storm Warning for the Hermon and Golan for Wednesday into Thursday.
High Wind Warning for Gale Force Winds.
Flood Risk from south-central Israel to northern Israel (with the heaviest rain occurring as one moves northward).
Winter Storm Watch for Gush Etzion and the Highest peaks around Jerusalem.
I am writing late because I spent the afternoon trying to find the last "Who" in "Whoville" who might be keeping quiet. The one who might the tip the balance in favor of those who want snow versus those who don't. I didn't find him (or her).
Hence, there is quite a conundrum. The forecast has changed quite substantially within the last couple of days. Instead of extreme cold in the lower levels and relatively mild temperatures aloft, the forecast is showing "snow" cold in the lower levels and extreme cold in the upper levels. This makes it less likely that temperatures will be cold enough for accumulating snow in Jerusalem. Snow, though, is still likely in the higher elevation of the Galilee and hills surrounding Sefad.
Moreover, there are large forecast differences between the new version of the Global Forecast System (GFS) and its old version (still in operational use). The new GFS produces a deep, wintertime trough over the eastern Mediterranean, similar to the ECMWF and Canadian model. So, in the discussion below, we're relying on the new GFS and our downscaled Weather Forecasting and Research (WRF) model based on it, rather than the old GFS.
The extreme cold in the upper levels is conducive to the production of "thunder-snow," which often leads to a snow accumulation when combined with cold lower atmospheric temperatures. However, our high resolution forecast is again showing that surface temperatures will remain above freezing in a saturated surface layer. This means -- again -- that snow will melt with the exception at the highest elevations of Gush Etzion. Folks even in Jerusalem should see snow, especially from noon Wednesday to about midnight Wednesday night, but it maybe hard pressed to stick around. Regardless, expect there to be elevation dependent icy conditions anytime during the height of the storm. Heavy rain and/or blowing snow could reduce visibility to only several meters.
In a previous blog I wrote that there are things we know and things we don't know. One of them was could one rely on the Global Ensemble Forecast System (GEFS) model forecasts after the individual forecasts converged to a tightly clustered group. In our case, we were wondering whether after the different forecast members of the ensemble converged to produce greater certainty would they as a "close-knit" group deviate from their previous forecast of extreme cold. The answer is in, and they have deviated. As noted, the upper levels have cooled off significantly from their previously shown values, but the lower levels have warmed up significantly. Whether this indicates a problem with model physic and numerical integration (or simply that the distribution of possible forecasts is not wide enough) is still an unknown.
What I hope to find out after a bit of research I am engaged in now is what is the probability that a forecast that is tightly clustered will occur as previously forecast some days in advance. This is on going research, and there is no clear answer yet. In other words, there are forecast probabilities and then there is the probability that the mean of the forecast will be within a certain range.
At the moment, no significant storms are shown for next week, which is a big change from the past several weeks.
Barry Lynn
Sunday, January 13, 2019
Weather It Is (Two Storms/One Snowy)
Good Afternoon:
There are two storms on the way: the first will bring liquid precipitation to all but the Hermon (where 30 to 50 cm of snow will fall). This will also bring strong winds. The second has a high probability to be the coldest storm in this decade, but it will be a fast mover, and snow amounts will depend on important details still to unfold. It will also bring gale force winds.
If one follows the travails of the Global Forecast System's model (GFS) , then one notes that it is a warm "outlier" among the GFS ensembles (the "GEFS"). WRF high resolution forecasts based on the GFS have forecast a light to moderate snow in Jerusalem (and more in Gush Etzion) to actually no snow in Jerusalem during our upcoming storm. However, both the GEFS and European model (the "ECMWF" ensemble) have been trending towards colder temperatures, which would bring more snow to the central mountains.
A positive (or cold) trend does not mean that the trend will continue until it snows (a lot), but rather that the initial conditions and their spread now encompass more cold and snowy forecasts. This means that the more we know about the upcoming weather, the more it "looks like" snow (as more forecasts end up producing colder temperatures and plenty of precipitation) despite using initial conditions that deviate from what our observations tell us.
Right now, about 30% of the forecasts (6/20) show a brief period of moderate to heavy snow in the afternoon/evening, which could leave Jerusalem without anything more than slush. Thirty-five percent of the forecasts (7/20) suggest a moderate accumulation (5 to 10 cm) in Jerusalem from Wednesday afternoon into Thursday night. Another 35% of the forecasts suggest a heavier snow that will last into early Thursday morning (not to mention the one forecast that prolongs snow into Thursday afternoon -- a 5% chance). Along with the heavier snowfalls are extended hours of colder surface temperatures below freezing.
So, the chance for accumulating snow in Jerusalem is 70% -- assuming that the probabilities truly represent the possible range of initial conditions valid for the observed set of conditions (measured with satellite, radiosondes, airplanes, profilers, and surface stations).
The snow and freezing temperatures are most likely to arrive in the central mountains late Wednesday morning and will probably be a mixture of ice-pellets and snow, which will likely cause a quick icing of the roads. Combined with the winds and snow, blizzard conditions are certainly possible, if not likely during periods of heavy snow
At this time, we should stress that there is still a 35% chance of just slush in Jerusalem. The next 12 to 24 hours should provide us with enough information to know where we'll be in the distribution, or where snowflakes will fall and stick.
Barry Lynn
There are two storms on the way: the first will bring liquid precipitation to all but the Hermon (where 30 to 50 cm of snow will fall). This will also bring strong winds. The second has a high probability to be the coldest storm in this decade, but it will be a fast mover, and snow amounts will depend on important details still to unfold. It will also bring gale force winds.
If one follows the travails of the Global Forecast System's model (GFS) , then one notes that it is a warm "outlier" among the GFS ensembles (the "GEFS"). WRF high resolution forecasts based on the GFS have forecast a light to moderate snow in Jerusalem (and more in Gush Etzion) to actually no snow in Jerusalem during our upcoming storm. However, both the GEFS and European model (the "ECMWF" ensemble) have been trending towards colder temperatures, which would bring more snow to the central mountains.
A positive (or cold) trend does not mean that the trend will continue until it snows (a lot), but rather that the initial conditions and their spread now encompass more cold and snowy forecasts. This means that the more we know about the upcoming weather, the more it "looks like" snow (as more forecasts end up producing colder temperatures and plenty of precipitation) despite using initial conditions that deviate from what our observations tell us.
Right now, about 30% of the forecasts (6/20) show a brief period of moderate to heavy snow in the afternoon/evening, which could leave Jerusalem without anything more than slush. Thirty-five percent of the forecasts (7/20) suggest a moderate accumulation (5 to 10 cm) in Jerusalem from Wednesday afternoon into Thursday night. Another 35% of the forecasts suggest a heavier snow that will last into early Thursday morning (not to mention the one forecast that prolongs snow into Thursday afternoon -- a 5% chance). Along with the heavier snowfalls are extended hours of colder surface temperatures below freezing.
So, the chance for accumulating snow in Jerusalem is 70% -- assuming that the probabilities truly represent the possible range of initial conditions valid for the observed set of conditions (measured with satellite, radiosondes, airplanes, profilers, and surface stations).
The snow and freezing temperatures are most likely to arrive in the central mountains late Wednesday morning and will probably be a mixture of ice-pellets and snow, which will likely cause a quick icing of the roads. Combined with the winds and snow, blizzard conditions are certainly possible, if not likely during periods of heavy snow
At this time, we should stress that there is still a 35% chance of just slush in Jerusalem. The next 12 to 24 hours should provide us with enough information to know where we'll be in the distribution, or where snowflakes will fall and stick.
Barry Lynn
Saturday, January 12, 2019
Weather It Is (Stormy, Windy, and Snowy)
Good Evening:
The coldest weather of the year -- if not the decade -- is on the way.
But, first, a storm will approach from the west and bring us strong winds and rain from Sunday evening into Tuesday, with the highest amounts of rain falling along the coastal areas and mountains of the north (with snow on the Hermon).
All ensemble models agree that the coldest weather in years will then arrive Wednesday afternoon along with gale force winds, and rain changing to snow and lasting into Thursday. The storm will be taking an unusual path southeastward from the Scandinavian region, rather than a more southerly track from western Siberia. This will allow the storm to pick up plenty of moisture on the way. Our high resolution forecast shows that temperatures should be at zero or below over most of the central mountain areas. The temperatures at 850 mb should be close to -5 Celsius, and -15 Celsius at 700 mb. These values are much colder than any storms in the last decade, which will insure a dry, accumulating snow.
There is a greater than 90% chance that the second storm (the snowstorm) should arrive on Wednesday. What is unclear is just how far southward the upper level trough will approach. The further south, the greater the snow rates should be and the lower the snow elevation levels. Right now, several centimeters are predicted in Jerusalem, while greater than 10 cm in Gush Etzion. But, these are probably conservative values.
In other words, the details need to be "ironed out," but it already seems like someone already left the freezer door open.
Barry Lynn
The coldest weather of the year -- if not the decade -- is on the way.
But, first, a storm will approach from the west and bring us strong winds and rain from Sunday evening into Tuesday, with the highest amounts of rain falling along the coastal areas and mountains of the north (with snow on the Hermon).
All ensemble models agree that the coldest weather in years will then arrive Wednesday afternoon along with gale force winds, and rain changing to snow and lasting into Thursday. The storm will be taking an unusual path southeastward from the Scandinavian region, rather than a more southerly track from western Siberia. This will allow the storm to pick up plenty of moisture on the way. Our high resolution forecast shows that temperatures should be at zero or below over most of the central mountain areas. The temperatures at 850 mb should be close to -5 Celsius, and -15 Celsius at 700 mb. These values are much colder than any storms in the last decade, which will insure a dry, accumulating snow.
There is a greater than 90% chance that the second storm (the snowstorm) should arrive on Wednesday. What is unclear is just how far southward the upper level trough will approach. The further south, the greater the snow rates should be and the lower the snow elevation levels. Right now, several centimeters are predicted in Jerusalem, while greater than 10 cm in Gush Etzion. But, these are probably conservative values.
In other words, the details need to be "ironed out," but it already seems like someone already left the freezer door open.
Barry Lynn
Friday, January 11, 2019
Weather It Is (Looming Storms)
Good Afternoon:
"But sometimes the forecast really is, maybe it will snow, but maybe it will just rain. And then we wake up to sand all over our cars. And then I remember, sand is also precipitation."
That about sums up how I felt last week. It did snow Sunday night, but all we had to show for it was sand the next morning. Ironically, the dry air associated with the dust/sand enabled the surface cooling that brought the snow to Gush Etzion. This was followed by a storm that was full of snow, but not where it mattered (where we live at the surface, unless you were on the Golan).
So, when we can finally say that there is something to be excited about, where the forecast should (or is that will) be how much snpw accumulates (in Jerusalem) rather than if, then we might begin to feel that the prelude was worth it.
Many times in the past, our snowstorms have arrived via the Siberian Express, dropping Siberian cold almost directly into the far eastern Mediterranean. However, Wednesday's storm should follow on the heels of our next storm arriving on Sunday with heavy rain and wind (and snow on the Hermon). It should shoot in on a southeasterly vector from an unusual location (think Sweden and Finland) passing just west of Cyprus and make a bee-line towards our area. The extremely cold air should pick up plenty of moisture, but because it will be unusually cold it should also bring snow. It will also be fast moving so the extreme cold associated with it will last just a couple of days (into Friday), but the trajectory over the sea should maximize precipitation potential.
Regarding the cold, the probability is about 75%, while the likelihood of an accumulating snow is at 60%.
Stay tuned!
Barry Lynn
"But sometimes the forecast really is, maybe it will snow, but maybe it will just rain. And then we wake up to sand all over our cars. And then I remember, sand is also precipitation."
That about sums up how I felt last week. It did snow Sunday night, but all we had to show for it was sand the next morning. Ironically, the dry air associated with the dust/sand enabled the surface cooling that brought the snow to Gush Etzion. This was followed by a storm that was full of snow, but not where it mattered (where we live at the surface, unless you were on the Golan).
So, when we can finally say that there is something to be excited about, where the forecast should (or is that will) be how much snpw accumulates (in Jerusalem) rather than if, then we might begin to feel that the prelude was worth it.
Many times in the past, our snowstorms have arrived via the Siberian Express, dropping Siberian cold almost directly into the far eastern Mediterranean. However, Wednesday's storm should follow on the heels of our next storm arriving on Sunday with heavy rain and wind (and snow on the Hermon). It should shoot in on a southeasterly vector from an unusual location (think Sweden and Finland) passing just west of Cyprus and make a bee-line towards our area. The extremely cold air should pick up plenty of moisture, but because it will be unusually cold it should also bring snow. It will also be fast moving so the extreme cold associated with it will last just a couple of days (into Friday), but the trajectory over the sea should maximize precipitation potential.
Regarding the cold, the probability is about 75%, while the likelihood of an accumulating snow is at 60%.
Stay tuned!
Barry Lynn
Thursday, January 10, 2019
Weather It Is (A Looming Storm)
Good Afternoon:
At the risk of anthropomorphizing the weather, one might take umbrage at the bit of irony exercised during our last two storms. In the first storm, temperatures several hundred meters off the ground (at 850 mb) were just below zero, while in the second storm they were about 2 degrees Celsius below zero. Yet, snow and ice accumulated in Gush Etzion during the first storm, but did not during the second. Moreover, the first storm brought about 5 mm of liquid equivalent (melted) rain to Gush Etzion, while the second brought close to 35 mm.
The difference between the two storms was a strong temperature inversion above 700 mb in the second, and not the first, which limited evaporational cooling of the air layer between 850 mb and the surface several hundred meters below. Just to note, it's not the mixing of air from the colder 850 mb layer (that just generally redistributes the air with height as sinking air warms and rising air cools), but the physical processes related to evaporation and condensation. Evaporation of droplets cools the air, and the melting of snow can also cool the air. So, while it was amply possible to freeze ice cubes on the Hermon (at 850 mb and higher), those below were left with just cold drinks. Further, they suffered the indignity of watching snowflakes melt either on the way down or when they reached the ground, and I can tell you it is not a pleasant sight to see or to hear (the screams of thousands of melting snowflakes) -- or maybe that was just me sighing.
I could also mention that actual temperatures were about 1 degree warmer at the surface than forecast. Had the opposite occurred, the snow probably would have accumulated.
The problem with the above two sentences is that it is short on actionable information. True actionable information is given through forecast probabilities. When the probability of a weather event is greater than the cost (protection against the event) to loss (losses occurring if no protection is taken) then preventive efforts should be made. If not, then, no action should be taken. That could be as simple as leaving early or deciding to put snowplows on standby.
We actually run a high resolution ensemble forecast in order to more accurately assess forecast probabilities. From these forecasts we can say how probable is it that rainfall will exceed 50 mm, for example, or winds will exceed 75 km /h, etc. However, the grid spacing of these ensembles is not fine enough to see the probability of snow accumulation in the Jerusalem area in storms where surface temperatures are forecast to be very close to freezing.
Hence, we're left with saying: if our highest resolution (single) forecast is accurate, this will happen. But, to offer guesses about what might happen if the temperature will be 1 degree Celsius colder is really just speculation (and I've decided to no longer spectulate!).
Anyway, next week offers the possibility that our ensemble may in fact be useful at forecasting snow amounts, since there is about a 30% chance that temperatures will be far enough below zero to imply that what will be important will be how much snow, not if it will snow.
But, first, it's going to warm up quite a bit through Shabbat, before temperatures fall sharply into early next week and rain returns with snow on the Hermon. The storm following about a week from now is the one that could have meteorologists most excited. It also has the greatest chance this year of bringing snow to Jerusalem.
Barry Lynn
At the risk of anthropomorphizing the weather, one might take umbrage at the bit of irony exercised during our last two storms. In the first storm, temperatures several hundred meters off the ground (at 850 mb) were just below zero, while in the second storm they were about 2 degrees Celsius below zero. Yet, snow and ice accumulated in Gush Etzion during the first storm, but did not during the second. Moreover, the first storm brought about 5 mm of liquid equivalent (melted) rain to Gush Etzion, while the second brought close to 35 mm.
The difference between the two storms was a strong temperature inversion above 700 mb in the second, and not the first, which limited evaporational cooling of the air layer between 850 mb and the surface several hundred meters below. Just to note, it's not the mixing of air from the colder 850 mb layer (that just generally redistributes the air with height as sinking air warms and rising air cools), but the physical processes related to evaporation and condensation. Evaporation of droplets cools the air, and the melting of snow can also cool the air. So, while it was amply possible to freeze ice cubes on the Hermon (at 850 mb and higher), those below were left with just cold drinks. Further, they suffered the indignity of watching snowflakes melt either on the way down or when they reached the ground, and I can tell you it is not a pleasant sight to see or to hear (the screams of thousands of melting snowflakes) -- or maybe that was just me sighing.
I could also mention that actual temperatures were about 1 degree warmer at the surface than forecast. Had the opposite occurred, the snow probably would have accumulated.
The problem with the above two sentences is that it is short on actionable information. True actionable information is given through forecast probabilities. When the probability of a weather event is greater than the cost (protection against the event) to loss (losses occurring if no protection is taken) then preventive efforts should be made. If not, then, no action should be taken. That could be as simple as leaving early or deciding to put snowplows on standby.
We actually run a high resolution ensemble forecast in order to more accurately assess forecast probabilities. From these forecasts we can say how probable is it that rainfall will exceed 50 mm, for example, or winds will exceed 75 km /h, etc. However, the grid spacing of these ensembles is not fine enough to see the probability of snow accumulation in the Jerusalem area in storms where surface temperatures are forecast to be very close to freezing.
Hence, we're left with saying: if our highest resolution (single) forecast is accurate, this will happen. But, to offer guesses about what might happen if the temperature will be 1 degree Celsius colder is really just speculation (and I've decided to no longer spectulate!).
Anyway, next week offers the possibility that our ensemble may in fact be useful at forecasting snow amounts, since there is about a 30% chance that temperatures will be far enough below zero to imply that what will be important will be how much snow, not if it will snow.
But, first, it's going to warm up quite a bit through Shabbat, before temperatures fall sharply into early next week and rain returns with snow on the Hermon. The storm following about a week from now is the one that could have meteorologists most excited. It also has the greatest chance this year of bringing snow to Jerusalem.
Barry Lynn
Tuesday, January 8, 2019
Weather It Is (Winter Storm Update)
Good Afternoon:
The forecast remains as was previously stated for Har Harmon, the Golan, and coastal area Warnings are repeated here.
Winter Storm Warning for the Hermon and Golan.
Winter Storm Warning for higher mountains outside of Sefad for 5 to 10 cm of snow/ice beginning Tuesday afternoon and lasting into Wednesday morning.
Gale Warning for coastal and mountain areas from Tuesday afternoon into Wednesday Morning.
Potential for flooding from Netanya to Haifa, and eastward toward Sefad, including the Jordan Valley on Tuesday and Tuesday night.
Jerusalem: Rain mixing with ice pellets and wet snow towards midnight, but temperatures should remain above freezing. Little or no accumulation of snow expected.
Gush Etzion and Higher Elevations Around Jerusalem: Potential for 5 to 10 cm of ice and snow, depending on elevation. Rain, ice, and snow in the evening hours, changing to ice and wet snow towards mid-night (rain in the lowest elevations). After a lessening of precipitation, the morning hours should see a period of ice and snow return to Gush Etzion.
The latest forecasts are in, and they leave much uncertain. However, the upper level temperatures are forecast to be around -25 C, which are warmer than temperatures typically associated with snow in Jerusalem. With warmer temperatures aloft, any cooling in lower levels must occur do to mechanical mixing or evaporative cooling, and there isn't enough forecast cooling to change the rain to an accumulating snow in Jerusalem.
However, at higher elevations, temperatures are cooler than in Jerusalem itself (about 1 degree Celsius for each 100 m). Moreover, precipitation is forecast to be heavier south of Jerusalem towards morning, which should add to the potential for snow in Gush Etzion.
Forecasters would much prefer a "clear-cut" situation. The key is mixing from the 850 mb level. Such mixing is not forecast in high enough magnitude to bring snow to Jerusalem, while there is greater "hope" that there will be enough cold air seeping to the surface in Gush Etzion to bring a covering of snow. On the other hand, 1 degree can make all the difference, and we won't know which way that one degree goes (up or down) until the morning.
I'd much rather be able to make this forecast in hindsight.
Barry Lynn
The forecast remains as was previously stated for Har Harmon, the Golan, and coastal area Warnings are repeated here.
Winter Storm Warning for the Hermon and Golan.
Winter Storm Warning for higher mountains outside of Sefad for 5 to 10 cm of snow/ice beginning Tuesday afternoon and lasting into Wednesday morning.
Gale Warning for coastal and mountain areas from Tuesday afternoon into Wednesday Morning.
Potential for flooding from Netanya to Haifa, and eastward toward Sefad, including the Jordan Valley on Tuesday and Tuesday night.
Jerusalem: Rain mixing with ice pellets and wet snow towards midnight, but temperatures should remain above freezing. Little or no accumulation of snow expected.
Gush Etzion and Higher Elevations Around Jerusalem: Potential for 5 to 10 cm of ice and snow, depending on elevation. Rain, ice, and snow in the evening hours, changing to ice and wet snow towards mid-night (rain in the lowest elevations). After a lessening of precipitation, the morning hours should see a period of ice and snow return to Gush Etzion.
The latest forecasts are in, and they leave much uncertain. However, the upper level temperatures are forecast to be around -25 C, which are warmer than temperatures typically associated with snow in Jerusalem. With warmer temperatures aloft, any cooling in lower levels must occur do to mechanical mixing or evaporative cooling, and there isn't enough forecast cooling to change the rain to an accumulating snow in Jerusalem.
However, at higher elevations, temperatures are cooler than in Jerusalem itself (about 1 degree Celsius for each 100 m). Moreover, precipitation is forecast to be heavier south of Jerusalem towards morning, which should add to the potential for snow in Gush Etzion.
Forecasters would much prefer a "clear-cut" situation. The key is mixing from the 850 mb level. Such mixing is not forecast in high enough magnitude to bring snow to Jerusalem, while there is greater "hope" that there will be enough cold air seeping to the surface in Gush Etzion to bring a covering of snow. On the other hand, 1 degree can make all the difference, and we won't know which way that one degree goes (up or down) until the morning.
I'd much rather be able to make this forecast in hindsight.
Barry Lynn
Monday, January 7, 2019
Weather It Is (Cold and Wintry/Snow)
Good Evening:
A "Warning" means that conditions are expected.
A "Watch" means that there is potential for, but no certainty.
Winter Storm Watch for the Jerusalem area (snow and cold) for Tuesday night into Wednesday morning.
Winter Storm Warning for the Hermon and Golan.
Winter Storm Watch for Sefad for 5 to 10 cm of snow/ice beginning Tuesday afternoon and lasting into Wednesday morning.
Gale Warning for coastal and mountain areas from Tuesday afternoon into Wednesday Morning.
Potential for flooding from Netanya to Haifa, and eastward toward Sefad, including the Jordan Valley on Tuesday and Tuesday night.
On Sunday night snow fell and accumulated (lightly) in the higher elevations of Gush Etzion, while snow accumulated on cars elsewhere. Heavy snow fell on the Golan. The cold temperatures in the Jerusalem area were well forecast by our high resolution model, with these models correctly predicting a near iso-thermal layer from 850 mb to the surface.
However, the precipitation amounts were smaller than forecast. As pointed by Yaakov Consor, winds were southwesterly ahead of the storm. As in the past, this has caused a delay in the precipitation reaching the central area, and also reduced overall amounts compared to forecast amounts. What is it about the southwesterly winds that causes an error in the forecast precipitation amounts? Based on our research, the most likely reason is a lack of sensitivity to high concentrations of dust, which creates a lot of small drops, delaying the formation of large, precipitating "hydrometeors."
In Sunday night's storm, temperatures were very cold at 500 mb, and marginally cold enough at 700 and 850 mb for snow in the central mountains. In the storm arriving tomorrow/Tuesday night, temperatures will be 1 to 2 degrees colder at both pressure levels -- yet there is little talk about snow tomorrow night. Moreover, as pointed out by Mr. Consor, winds will be swinging around from the northwest, which provides greater confidence in the the stream of moisture and precipitation forecast over the central mountains.
So, why is there little talk of snow? The first reason is that many people believe that that temperatures should be close to minus 30 C at 500 mb for there to be snow in Jerusalem, and until now temperatures were forecast to be warmer than minus 25 degrees Celsius. Very cold temperatures at 500 mb indicate a potential for stronger precipitation and more mixing of cold air downward. Warmer temperatures aloft would slow the mixing of colder air towards the surface, delaying (or preventing ) any change over of rain to snow.
However, the latest forecast shows better phasing of the 500 mb trough with the lower level storm, which is associated now with a range of temperatures between -25 Celsius and -27 Celcius. This could create heavier periods of precipitation, which would enhance mixing of colder air to the ground. Moreover, the strong westerly, upslope (the mountain) winds should enhance mixing of lower level cold, and the precipitation is suppose to last from early evening until the morning hours, providing time for colder air to seep downwards.
The very cold temperatures are expected to last until Friday morning, when there will be a sharp warm up to even spring-like temperatures that should last a few days, before winter and another storm return early next week.
Will there be a snow accumulation in Jerusalem? We know that the global forecast models are certain about the cold at the lower levels and middle levels, but less certain about the southern extent of the upper level trough and its associated cold air. This lack of certainty combined with the difficulty of predicting lower level mixing lowers the confidence we have for an accumulating snow. Still, the cold temperatures should create dangerous/icy travelling conditions at the higher elevations surrounding Jerusalem and in Gush Etzion, which will last into the morning hours.
Based on the high resolution model's forecast of precipitation amounts, and associated snow and ice amounts, the potential exists for 3 to 5 cm of snow and ice in Jerusalem, 5 to 10 cm in the higher areas outside of Jerusalem, and 10 to 15 cm in the highest areas of Gush Etzion.
Will we reach the potential? Very difficult to say with any certainty.
Barry Lynn
A "Warning" means that conditions are expected.
A "Watch" means that there is potential for, but no certainty.
Winter Storm Watch for the Jerusalem area (snow and cold) for Tuesday night into Wednesday morning.
Winter Storm Warning for the Hermon and Golan.
Winter Storm Watch for Sefad for 5 to 10 cm of snow/ice beginning Tuesday afternoon and lasting into Wednesday morning.
Gale Warning for coastal and mountain areas from Tuesday afternoon into Wednesday Morning.
Potential for flooding from Netanya to Haifa, and eastward toward Sefad, including the Jordan Valley on Tuesday and Tuesday night.
On Sunday night snow fell and accumulated (lightly) in the higher elevations of Gush Etzion, while snow accumulated on cars elsewhere. Heavy snow fell on the Golan. The cold temperatures in the Jerusalem area were well forecast by our high resolution model, with these models correctly predicting a near iso-thermal layer from 850 mb to the surface.
However, the precipitation amounts were smaller than forecast. As pointed by Yaakov Consor, winds were southwesterly ahead of the storm. As in the past, this has caused a delay in the precipitation reaching the central area, and also reduced overall amounts compared to forecast amounts. What is it about the southwesterly winds that causes an error in the forecast precipitation amounts? Based on our research, the most likely reason is a lack of sensitivity to high concentrations of dust, which creates a lot of small drops, delaying the formation of large, precipitating "hydrometeors."
In Sunday night's storm, temperatures were very cold at 500 mb, and marginally cold enough at 700 and 850 mb for snow in the central mountains. In the storm arriving tomorrow/Tuesday night, temperatures will be 1 to 2 degrees colder at both pressure levels -- yet there is little talk about snow tomorrow night. Moreover, as pointed out by Mr. Consor, winds will be swinging around from the northwest, which provides greater confidence in the the stream of moisture and precipitation forecast over the central mountains.
So, why is there little talk of snow? The first reason is that many people believe that that temperatures should be close to minus 30 C at 500 mb for there to be snow in Jerusalem, and until now temperatures were forecast to be warmer than minus 25 degrees Celsius. Very cold temperatures at 500 mb indicate a potential for stronger precipitation and more mixing of cold air downward. Warmer temperatures aloft would slow the mixing of colder air towards the surface, delaying (or preventing ) any change over of rain to snow.
However, the latest forecast shows better phasing of the 500 mb trough with the lower level storm, which is associated now with a range of temperatures between -25 Celsius and -27 Celcius. This could create heavier periods of precipitation, which would enhance mixing of colder air to the ground. Moreover, the strong westerly, upslope (the mountain) winds should enhance mixing of lower level cold, and the precipitation is suppose to last from early evening until the morning hours, providing time for colder air to seep downwards.
The very cold temperatures are expected to last until Friday morning, when there will be a sharp warm up to even spring-like temperatures that should last a few days, before winter and another storm return early next week.
Will there be a snow accumulation in Jerusalem? We know that the global forecast models are certain about the cold at the lower levels and middle levels, but less certain about the southern extent of the upper level trough and its associated cold air. This lack of certainty combined with the difficulty of predicting lower level mixing lowers the confidence we have for an accumulating snow. Still, the cold temperatures should create dangerous/icy travelling conditions at the higher elevations surrounding Jerusalem and in Gush Etzion, which will last into the morning hours.
Based on the high resolution model's forecast of precipitation amounts, and associated snow and ice amounts, the potential exists for 3 to 5 cm of snow and ice in Jerusalem, 5 to 10 cm in the higher areas outside of Jerusalem, and 10 to 15 cm in the highest areas of Gush Etzion.
Will we reach the potential? Very difficult to say with any certainty.
Barry Lynn
Sunday, January 6, 2019
Weather It Is (Wintery Weather)
Good Evening:
Heavy precipitation is moving into coastal areas and will make its way to the central mountains later this evening, lasting into early morning.
Meanwhile, heavy snow will fall on the Golan. Heavy rain along the coast with gale force winds.
The latest model forecast shows a near isothermal layer from 850 mb stretching down to the surface in Gush Etzion. Since temperatures are below freezing at 850 mb, there should be a very late evening burst of snow and ice that will probably coat the ground in Gush Etzion and the very highest hills around Jerusalem.
In Jerusalem itself, the isothermal layer develops after midnight, and doesn't quite extend to the freezing level at 850 mb -- so temperatures remain above freezing. Still, wet snow and ice is predicted in Jerusalem, and it could coat colder surfaces before quickly melting when the precipitation slackens.
Have a good night!
Barry Lynn
Heavy precipitation is moving into coastal areas and will make its way to the central mountains later this evening, lasting into early morning.
Meanwhile, heavy snow will fall on the Golan. Heavy rain along the coast with gale force winds.
The latest model forecast shows a near isothermal layer from 850 mb stretching down to the surface in Gush Etzion. Since temperatures are below freezing at 850 mb, there should be a very late evening burst of snow and ice that will probably coat the ground in Gush Etzion and the very highest hills around Jerusalem.
In Jerusalem itself, the isothermal layer develops after midnight, and doesn't quite extend to the freezing level at 850 mb -- so temperatures remain above freezing. Still, wet snow and ice is predicted in Jerusalem, and it could coat colder surfaces before quickly melting when the precipitation slackens.
Have a good night!
Barry Lynn
Saturday, January 5, 2019
Weather It Is (Winter Weather Warning)
Good Evening:
Highlights: Winter Storm Warning for Har Hermon Sunday and Sunday Night (into Monday), for 50 to 100 cm of snow. Winter Storm Warning for the Golan for Sunday Night, for up to 20 cm of snow.
Winter Weather Warning for the area of Safed and Jerusalem (north and southern hills). Sunday evening and night, mixed rain, snow, and ice is expected with a coating of ice possible during heavier precipitation periods (but the ice should melt in above freezing temperatures). A light snow accumulation is also possible on mountains north of Jerusalem.
Heavy Rain is expected along the coastal areas, with 25 to 50 mm, and 50 to 75 mm in the far north (outside of the Hermon and Golan).
Strong and gale force winds expected during Sunday and Sunday night in many locations.
Possibility of snow in higher elevations of the central mountains Tuesday night into Wednesday morning.
Discussion: Very cold air is poised to move in at upper levels (500 mb) Sunday evening. This will trigger heavy precipitation, and would normally would bring snow to Jerusalem. However, the middle levels of the atmosphere are only marginally cold enough for snow, and temperatures near the surface should be 2 to 3 Celcius. This mean that there can be some ice in heavier precipitation, and rain mixed with snow (most likely between late evening hours until midnight), but a snow accumulation is (currently) very unlikely in Jerusalem.
However, the forecasts are showing colder air at lower and middle levels arriving Tuesday night, along with heavier precipitation. There is also an indication of additional phasing at upper levels. If everything comes "together," there could be a wet snow in Jerusalem Tuesday night into early morning.
We plan further updates as the storm(s) progress.
Barry Lynn
Highlights: Winter Storm Warning for Har Hermon Sunday and Sunday Night (into Monday), for 50 to 100 cm of snow. Winter Storm Warning for the Golan for Sunday Night, for up to 20 cm of snow.
Winter Weather Warning for the area of Safed and Jerusalem (north and southern hills). Sunday evening and night, mixed rain, snow, and ice is expected with a coating of ice possible during heavier precipitation periods (but the ice should melt in above freezing temperatures). A light snow accumulation is also possible on mountains north of Jerusalem.
Heavy Rain is expected along the coastal areas, with 25 to 50 mm, and 50 to 75 mm in the far north (outside of the Hermon and Golan).
Strong and gale force winds expected during Sunday and Sunday night in many locations.
Possibility of snow in higher elevations of the central mountains Tuesday night into Wednesday morning.
Discussion: Very cold air is poised to move in at upper levels (500 mb) Sunday evening. This will trigger heavy precipitation, and would normally would bring snow to Jerusalem. However, the middle levels of the atmosphere are only marginally cold enough for snow, and temperatures near the surface should be 2 to 3 Celcius. This mean that there can be some ice in heavier precipitation, and rain mixed with snow (most likely between late evening hours until midnight), but a snow accumulation is (currently) very unlikely in Jerusalem.
However, the forecasts are showing colder air at lower and middle levels arriving Tuesday night, along with heavier precipitation. There is also an indication of additional phasing at upper levels. If everything comes "together," there could be a wet snow in Jerusalem Tuesday night into early morning.
We plan further updates as the storm(s) progress.
Barry Lynn
Wednesday, January 2, 2019
Weather It Is (One Storm Arrives, And Then Snow?)
Good Evening:
Right on schedule, our lightning detection network has identified a long line of thunderstorms arriving at our coast line. The map shows a radar depiction of the storms ("PulseRad") derived from the lightning data.
The storms are occurring along a frontal zone ahead of a low pressure area moving into Turkey. Very cold temperatures aloft will mean that hail should occur with these thunderstorms, while cold temperatures near the surface mean that ice ("cubes") could coat the ground tonight into tomorrow.
It will be followed by a brief warm-up, and then by a stronger storm developing just west of Cyprus. Just where this storm develops (just east of Cyprus is better) will determine the elevation at which snow falls on Sunday into Monday. The further east it develops, the colder the temperatures at the surface will be (as cold air moving over the sea absorbs heat from the Mediterranean Sea).
Right now, temperatures at upper levels should be cold enough for convective precipitation, which when combined with temperatures at middle levels just cold enough for good snow growth, means that this storm will give it a good try to bring snow to Jerusalem.
The problem is that any snowflake making the plunge towards earth will encounter temperatures near the surface that will probably be above freezing (with 850 mb temperatures possibly from just above freezing to a degree or so below). Basically, this is not a good situation to be in if you're a snowflake, and many of them may simply choose to stay aloft in the clouds, instead of taking the risk of melting on the way down.
Hence, we'll have to wait and see our high resolution forecasts in order to be able to know at what elevations snow might accumulate on the ground (if any, in our area).
Until then, we can't say if there will just be rain and mixed snow, or wet snow that might coat the highest elevations.
It might also be of interest to note that about 30% of our forecasts are predicting that the mid-week period will bring even colder weather. This could occur as cold air wraps behind our early next week's storm and possibly moves directly south into our area, with minimal moderation from warm sea-surface temperatures.
Barry Lynn
Right on schedule, our lightning detection network has identified a long line of thunderstorms arriving at our coast line. The map shows a radar depiction of the storms ("PulseRad") derived from the lightning data.
The storms are occurring along a frontal zone ahead of a low pressure area moving into Turkey. Very cold temperatures aloft will mean that hail should occur with these thunderstorms, while cold temperatures near the surface mean that ice ("cubes") could coat the ground tonight into tomorrow.
It will be followed by a brief warm-up, and then by a stronger storm developing just west of Cyprus. Just where this storm develops (just east of Cyprus is better) will determine the elevation at which snow falls on Sunday into Monday. The further east it develops, the colder the temperatures at the surface will be (as cold air moving over the sea absorbs heat from the Mediterranean Sea).
Right now, temperatures at upper levels should be cold enough for convective precipitation, which when combined with temperatures at middle levels just cold enough for good snow growth, means that this storm will give it a good try to bring snow to Jerusalem.
The problem is that any snowflake making the plunge towards earth will encounter temperatures near the surface that will probably be above freezing (with 850 mb temperatures possibly from just above freezing to a degree or so below). Basically, this is not a good situation to be in if you're a snowflake, and many of them may simply choose to stay aloft in the clouds, instead of taking the risk of melting on the way down.
Hence, we'll have to wait and see our high resolution forecasts in order to be able to know at what elevations snow might accumulate on the ground (if any, in our area).
Until then, we can't say if there will just be rain and mixed snow, or wet snow that might coat the highest elevations.
It might also be of interest to note that about 30% of our forecasts are predicting that the mid-week period will bring even colder weather. This could occur as cold air wraps behind our early next week's storm and possibly moves directly south into our area, with minimal moderation from warm sea-surface temperatures.
Barry Lynn
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