Saturday, December 31, 2016

Weather It Is (Winter Sticks Around)

Good Evening:

There is much "action" on the horizon.  Most encouraging is the waviness of the upper level (500 mb) pattern, where two waves will pass by on Monday and Tuesday night. The second will be colder than the first, and it might lead to some snow showers Tuesday night.

Looking at the lower atmospheric levels, there is some humidity, but temperatures should stay above freezing, so any snow showers should just melt.

The cold temperatures should moderate on Wednesday into the end of the week, but we see indications that early next week might turn quite cold, bringing back a chance of snow.  This storm (the third in our series) shows possible phasing between the lower and upper levels, which would bring lots of precipitation, wind, and snow.

We seem to be seeing a lot "opportunities" (~30% chances) for snow this year on the forecast maps.  If the global model has predictability beyond five days, then one of these weeks it will snow.

It was noted by a fellow blogger at "Jerusalem Snow" that the Climate Forecast Systems Model shows a cold January in store for us.  This is a change from what it showed in its three month outlook prior.

Barry Lynn

Friday, December 30, 2016

Weather It Is (Cold, But Not Much Else)

Good Afternoon:

Some light rain is expected from late tonight into late afternoon/evening Shabbat.

The rain will arrive with a strong chill, and there could be some wet snowflakes mixed in with the rain.

The cold should continue into Wednesday, with another chance of rain Monday Night/Tuesday.

Otherwise, the cold and the rain should take a break until the end of the week after next.

Shabbat Shalom/Chanukah Samaech,

Barry Lynn

Thursday, December 29, 2016

Weather It Is (Storm Update)

Good Morning:

For the last few days, the forecasts from the global ensemble have minimized the possibility of a snowstorm for us this Shabbat and early next week.

True, they continue to show a period of precipitation from Shabbat into Tuesday.  However, none of the forecasts show enough cold at the lower levels to provide the background conditions for a good snow. Instead, the real cold is suppose to move north to south over Greece. Moreover, as the storm system moves east it is suppose to weaken, providing us with only a glancing blow.

About 30% of the ensemble members hold back the arrival of the upper level support for this storm system until about Tuesday morning. These actually forecast a colder outcome at upper levels.  If they verify, there could be a period of wet snow about Tuesday morning.

Nevertheless, the weather pattern is more wintry than not, and the period of Shabbat through Tuesday will be chilly with temperatures struggling to rise through the single digits (much above zero) throughout the period. In fact, it won't warm up until the middle of next week.

On another note: I watched Secretary Kerry's speech last night.  It was an impassioned speech, and heartfelt.  He correctly noted that the Israeli building of towns in areas that might become land as part of a future Palestinian state is not consistent with the "idea" of an independent Palestinian state. He also made some good points about the potential benefits of a thriving Palestinian democracy for Palestinians themselves. He also noted the need for Israel to provide more land for the growth of Palestinian towns.

However, he skirted the most obvious reasons why a peace agreement has failed to materialize: the very people who we are suppose to negotiate with are the very same who support terrorism (e.g, in the media, religious institutions, and schools), and find the idea of a Jewish state anathema. So, when he talks about making known the United States disapproval of such activities, he is speaking to the very same people who find all of these activities perfectly acceptable, encourage them, and whose ultimate goal is not the continued existence of Israel, but its demise.

In other words, there is no one to speak to on the other side, and there is a fundamental and existential difference between building homes (they can be removed) and a world view that precludes the existence or acceptance of the State of Israel (in any form).

No less important: the idea that the international community together with the Palestinians will guarantee or insure our security against threats is laughable (just look across any of our borders).

Moreover, the idea that peace between us and the Palestinians will lead mitigate the threat from Iran, Hizbollah, Syria, ISIS, and Hamas is false.

Finally, it is Israeli overall control of the area that enables Palestinians to access modern roads, health care, and even the modern economy. One might also note that the Palestinian State (that exists in some form even now) is in no way a democracy, and would -- if left on its own -- become an Iranian protectorate.

Barry Lynn

Monday, December 26, 2016

Weather It Is (Winter Continues)

Good Evening:

We're expecting a strong rain system to move in tonight and tomorrow (Tuesday).  It should bring between 25 to 50 mm of rain across the coastal areas and into the central mountains.  More than 50 mm of rain is expected in the area of Haifa and northward. The storm should bring strong winds.

After light showers on Wednesday, another storm should arrive on Thursday with another round of rain. Through it all, temperatures should remain on the chilly side.

Friday night should see the arrival of another storm, with temperatures aloft becoming cold enough for snow.  However, a long fetch over the sea may warm lower atmospheric temperatures enough to limit snow accumulations.  The highest accumulations should be in the highest elevations around Jerusalem and the north.

As for amounts: anything we can write now is just guessing.  We need to wait until our high resolution forecasts come into play within three days of this possible snow event.

Otherwise, the maximum winds will be either strong or gale force, but not hurricane force winds as indicated by some of the ensemble forecasts the other day.

The cold weather with the next system should last into early next week.

Barry Lynn

Saturday, December 24, 2016

Weather It Is (Heavy Rain/Snow?)

Good Evening:

Not too long ago, it was legal to burn the Jewish people in gas ovens.  Now, it is illegal for Jews to live in Eretz Israel...

A series of winter storms will impact our region from tonight through the week. Each will come with strong upper level support, which means that we should expect heavy rain and thunderstorms (with hail, graupel).  More than 100 mm of rain are predicted in the Tel-Aviv area within the next day and a half. Winds will be strong late tonight, possibly gale force on Tuesday morning, and there is a chance for storm-force (more than gale), and even hurricane force winds at end of the week.

There is a 10% chance of wet snow with the rain on Tuesday morning.

As for the end of the week, Friday will see the onset of the most severe storm of the winter, with very heavy rain expected.  At the moment, it looks like the storm will be approaching from the west, which means that the sea-surface temperatures will likely warm the cold in the lower atmosphere.  This means wet-snow, rain, or rain mixed with snow, where any snow accumulation amounts will depend highly on elevation.

At the moment, it is too soon to predict if snow will accumulate, but the storm has the potential to be the most severe this year, as well in several years (December 2010).

Barry Lynn


Friday, December 23, 2016

Weather It Is (Yes or No)

Good Afternoon:

Today a streak of rain should fall from southwest to northeast across southern Israel.  The rain is associated with middle and upper level moisture. The rain amounts at any hour should not be significant, but the total amounts may lead to some stream runoff.  Like the rain the other day, it may leave a bit of dust on the windshield.

Otherwise, late Saturday should see the arrival of a more significant storm forming over Cyprus (the "Cyprus Low").  Rain with this storm should be heaviest in the center and central mountains, and possibly last into Monday, with another round on Tuesday.

These weather events, although significant in their own right, pale in the shadow of the next. All eyes remain glued to the end of the month calendar period where a significantly cold and wet feature remains present in the deterministic models and ensemble means.  Such is the potential strength of the end of the year storm that we can clearly see its imprint on the upper level winds (as represented by the absolute vorticity) within a sharp and mean looking upper level trough.

We're about a week away, and we can be hopeful that the end of this week will shed more light on what will happen at the end of next.

Shabbat Shalom,

Barry Lynn

Wednesday, December 21, 2016

Weather It Is (Winter)

Good Afternoon:

After taking a back seat to fall (some might even thought spring temperatures) winter has arrived.

There is a chill in the air and there are frequent periods of rain.

Looking at today's weather map, we see strong winds tonight as an upper level disturbance passes by to our northwest.  This should bring a period of rain along the NW coast.

By Shabbat, temperatures will fall again, and a heavier rain should arrive (again with strong winds). The storm system that will bring the next bout of winter weather can be clearly seen on the GEFS mean maps (on our site) in both cold upper air temperatures and strong vorticity advection. Temperatures in the upper atmosphere will below - 25 C, but temperatures in the middle and lower atmosphere will be relatively warm (for snow, meaning rain). The storm is actually passing over the sea after heading down south from past western Turkey, so this will ameliorate the low level cold normally associated with type of system.  Still, this type of scenario is good for producing thunderstorms and graupel.  The inclement weather should last into Sunday.

Then all eyes will turn (perhaps all eyes have already turned) to the monster of a system being noted on multiple forecast models and in the GEFS.  The GEFS shows about a 30% chance of real winter cold and snow at the end of the month, but the fact that the European model and the deterministic GFS continue to show this feature (and coupled with a strong NAO) gives us a bit more hope than our typical maybe it will snow comment.

Of course, anyone who has seen the new movie "Rogue 1" can't help from having a bit of hope.

Sincerely,

Barry Lynn


Monday, December 19, 2016

Weather It Is (Heavy Rain Arrives)

Good Evening:

The "burst" of rain has arrived.  Still expecting temperatures to fall to zero 0 tonight in the higher elevations with rain possibly mixing with snow, or becoming wet snow (with no accumulation -- likely).

We heard thunder a few minutes ago.  The thunderstorms associated with the approach of the cold air appear on the map below, with EN's "Pulse-Rad" (radar) overlaid.

Weather It Is (Unsettled and Cold)

Good Afternoon:

The latest forecasts show a burst of precipitation arriving in the late afternoon/evening to central coastal areas, and the mountains of Jerusalem and Gush Etzion.  Temperatures at 850 mb should be below 0 during tonight, so rain could end as a period of wet snow or rain/snow mixture.  Due to uncertainty in the forecast temperatures, it would be a mistake to speak about any snow accumulation with any confidence -- other than to say it is unlikely.

Looking further ahead: the global ensemble forecast continues to oscillate between various forecast outcomes. The previous forecast had a near 100% chance of rain for Shabbat, early next week.  Now, however, rain may arrive as early as Thursday.

The chance of snow on Thursday is just 10%, while it is a bit higher for the end of the week.

I think I will mention to NCEP that the global ensemble (GEFS) seems to be having a hard time producing consistent forecasts this year.

Barry Lynn


Sunday, December 18, 2016

Weather It Is (Stormy Weather, Snow?)

Good Morning:

Highlights

1) A period of rain and wind moving north to south today.

2) Late afternoon/evening rain along the center coast and rain/snow in the central mountains (Monday evening)

3) A larger and potentially more significant storm at the end of the week.

The forecasts from the GEFS (global ensemble) have been what one might term unreliable, perhaps beset by poor model initialization.  On its behalf, the type of weather that leads to our more winter-like/snowy weather originates in areas of the globe (the polar regions) that have fewer observations, so the model has to make "educated" guesses about the weather conditions there.

In any case, our high resolution forecast for today shows a cold front moving north to south today, bringing with it a period of rain as it passes (dissipating south of Gush Etzion).

What we see is that tomorrow's weather will bring another shot of even colder air.  The GEFS still shows temperatures just below freezing sat 850 mb, with some temperatures at 500 mb as low as -29 C.  Our high resolution model shows precipitation from this system, but temperature forecasts from it depend on which member of the ensemble we use, so it doesn't really tell us if it will snow. The mean ensemble forecast is close to -25 C, but some temperatures are forecast to be as high as -22 C.  For it to snow in the central mountains, the actual temperatures need to be on the cold side of the forecast range.  Let's say that there are equal probabilities of moderate rain, rain/snow, and snow tomorrow evening.

After a break of a couple of days, the forecasts show a much stronger system arriving, with precipitation from Thursday into Shabbat (and gale force winds).  This system shows many of the forecasts clustering on temperatures that will bring a rain/snow mix with some cold enough for snow.

Keeping in mind that it snows one or two times a year here (at best -- except in 1991/92 when it snowed multiple times even at elevations as low as 300 mb), perhaps the odds favor that this storm will be at best just some wet snow mixed with rain.

Shavua Tov,

Barry Lynn


Friday, December 16, 2016

Weather It Is (Change In The Forecast)

Good Afternoon:

There have been some strong, localized storms in the coastal areas, and rain from central Israel (Tel-Aviv) and northward will persist into Shabbat.

Otherwise, model forecast have swung back a bit towards winter, after being strongly committed to winter at the beginning of the coming week, only to recently build a ridge of higher pressure in the eastern Mediterranean instead.  Now, however, the European model and subsequently the GFS (and its ensembles) are indicating that winter (with heavy rain) will return on Sunday, and then Monday brings a good chance of rain, and even a 15% chance of snow.

What is a 15% chance of snow?  Why is he telling us this?  Strictly speaking, about 3 of the 20 (15%) of the ensemble members show the possibility of the middle and upper atmosphere supporting snow in the higher elevations on Monday. However, all the forecasts show temperatures near or below freezing in the lower atmosphere. Moreover, the strength of the building trough in the eastern Mediterranean is still uncertain, as there is still some divergence in the forecasts, and the trend is towards colder weather.

It depends in part on how the low over Spain develops, and where it moves, and more recent forecasts show it relatively weaker and further west, which means it should interfere less with the building of the trough in our area.

If all this sounds a bit like hand waving, it is -- because the global forecasts lack the information and resolution to forecast specifics more than 3 or 4 days in advance.  They are usually good (but not so good recently) at forecasting trends and general outlooks, but we need more information than this to forecast snow here because out temperatures during snowfall events are so close to freezing.

That's why we don't run our high resolution models more than a few days.  However, keep in mind that within about three days, our high resolution forecasts usually have good enough information from the global models and the grid resolution to be pretty accurate, which is reflected in the comments we receive from viewers of the site (thank you).

Moreover, with our lightning network in place, we can now run rapid updates of our forecasts that provide high short-term accuracy to predicting severe storms.

Shabbat Shalom,

Barry Lynn

Tuesday, December 13, 2016

Weather It Is (Extreme Winds, Heavy Rain, Extreme Cold)

Good Evening:

Warnings: Heavy Rain, Gale Force Winds, Chill

Our high resolution forecasts and ensembles show heavy rain should sweep down from the northwest tonight, producing > 25 mm in 3 h in locations along the central coast, and between 50 to 100 mm of rain by Friday over large areas of the country (with the exception of the far south),

The GEFS (global ensemble) shows a strong storm spinning up over Cyprus tonight and moving eastward inland by Friday.  The strong low pressure area is associated with very strong upper level support (vorticity advection).  Moreover, the ensemble shows high humidity levels even up to 500 mb, especially tonight when the heaviest rain is expected.

The rain will be accompanied by chilly temperatures. In fact, temperatures are just cold enough for snow at lower levels, but upper levels (500 mb) do not support snow formation.  However, with the chill, there may be some ice.

The winds should peak tomorrow afternoon at Gale force or even strong Gale.

The chill will moderate briefly, but the global ensemble is indicating that temperatures will fall below freezing in the higher elevations on Sunday and stay there into Tuesday morning.

The ensemble shows extremely cold temperatures at 700 mb, and some forecast members indicates similarly intense temperatures at 500 mb.

At the moment, though, the humidity profile shows saturated conditions in the lower levels, but less
than saturated conditions at 700 mb.  This means that a large precipitation (snow) event is currently not likely.

The mean ensemble maps (on our web site: https:\\weather-it-is-israel.com) show a broad area of cold approaching from the northeast, as well as a diffuse vorticity field.  This may simply reflect the uncertainty in the forecast, but also that this will be mainly an extremely cold event with snow showers.

Stay tuned.

Barry Lynn


Monday, December 12, 2016

Weather It Is (One Storm And Then A Jerusalem Snow Storm?)

Good Afternoon:

We're waiting for forecast updates.

However, our upcoming severe wind and heavy rain storm may be followed by extreme cold and heavy snow (in the mountainous areas, and even down to a few hundred meters of elevation) early next week.

Barry Lynn


December 12th, 2016

Today’s note is based on some e-mail correspondence that I received.  One of the correspondents prefers to remain anonymous, while the other (Jonathan Hoffman) contributed much of the material on the AO and NAO that follows below.

Basically, we often look for atmospheric “connections” between large-scale patterns we can measure, and the weather that eventually impacts our region – in this case with a potential large snowstorm.



For example: the following shows the forecast GEFS ensemble 850 mb temperatures for the next two weeks.  The ensemble of temperatures indicates that there is a high probability that it will be very cold, and even extremely cold.  If you combine this information with other information from the same forecast, you can infer that we may have a significant snow storm in about a week's time.


Jame Gleick is credited with the following:
Big whorls have little whorls
Which feed on their velocity,
And little whorls have lesser whorls
And so on to viscosity.”

In between the large atmospheric whirls, there are smaller wave patterns, which contain within them the stormy weather systems that impact our weather, and may bring our first significant snow in two years.

In this vein, I received an e-mail from an anonymous writer who wrote:

“A huge uncertainty in the teleconnections forecasts, especially after the 16th has been gradually resolved, it seems, in favor of a strongly rising AO  (Figure 1).  The NAO forecast is less certain, as forecast divergence still exists after 16th.

“The stratospheric PV (Fig. 3; Polar Vortex) is forecast to make a strong recovery. A lobe of it may pass close by, around the 24th, according to GEFS (Figure 4).

“What does this portend for the weather in our area? And, of course, everyone wants to know – ‘how does that affect our snow chances?’"

As noted by Mr. Hoffman: “Statistically speaking, Israel is more likely to receive cold air troughs with the polar jet when the NAO and/or AO are positive.” Such polar outbreaks increase our chances for snow. He correctly, I think, attributes this to what might be called an “open highway” in the streams of air that move across our globe.  “The polar jet is more easily able to flow north across the [Eastern United States and Atlantic Ocean] because it is not ramming into circular domes of air in the North Atlantic and Arctic regions.” One important factor, in other words,  is that storms that start on the northeast USA coast should have a clear path across the Atlantic ocean until they often come to “rest” in the area of Greenland, which then encourages a ridge (a bend to the north in the river of air) to form over the UK and western Europe, with a corresponding trough (bend to the south) of cold Russian air extending southwestward into the eastern Mediterranean. This, he notes “is more likely to happen with a +NAO and/or +AO.”

In contrast, if the AO and NAO were negative, storms would be less likely to move into Greenland.  The Jet Stream (streamers of high winds in the upper atmosphere) and storm within it would forced to stay south of that region thanks to the “dome”of cold air that has moved southward off the poles in association with the measured   negative NAO and/or -AO. Instead, storms would likely pass over the Atlantic Ocean, under the dome, and enter western Europe in a way that would start the European ridge further east such that it might even go over Israel. This would then send abnormally warm air into our region, killing the chances for snow.


Or, the trough would form over central Europe, directing typically wet, but not particularly cold air masses into our region.

Mr. Hoffman provides a couple of examples from recent forecasts for this week (starting December 11th, 2016). He notes the position of the polar and southern jet streams in Fig. 5 and the temperature anomalies associated with them. One notes how the polar jet bends northward over Europe, creating a ridge, and then comes downward with a trough close to Israel. This causes relative warming over Europe and relative cooling over Israel (and nearby countries). Note, also the southern Jet stream depicted here, which can funnel storms moving eastward across the Mediterranean into the trough, spinning up a potent storm in the base of the polar trough (just to our northwest).

Figure 6 shows more clearly the influence of a low pressure system and the NAO for creating this overall pattern. He points out that the low-pressure storm system is placed in the north Atlantic, a bit west of the UK, close to Greenland, and that a ridge forms over western Europe before dipping down as a trough over the eastern Mediterranean.

A similar storm situation, but stronger and better defined, may bring us our first significant snow in two years.










Sunday, December 11, 2016

Weather It Is (Gale Force Winds)

Good Afternoon:

Weather forecast accuracy has improved greatly since I started weather forecasting years ago, and the last few years have seen improvements still.

However, it is apparent that a lack of good information (weather data) in areas that really influence our weather (like the far northern latitudes, and perhaps the oceans) has set some sort of limit on our ability to peer over the horizon (from one week to the next).

For instance, last week we saw chances of snow for these coming days rise and fall, and finally fall again.  As new information enters the system, it should probably rise (and keep rising), or reach a peak and then fall and keep falling at some point in the advanced forecast.  This seems to occur about 5 or 6 days out.  We would like a few more days to be able to confidently look into next week.

This week's coming storm should produce heavy rain and gale force winds from Tuesday into Wednesday.  It may even get cold enough at the surface to freeze a few locations, but chances are small (other than on the Hermon where snow should fall again).

Yesterday's forecast showed that next week would most likely warm up a bit. There was even a larger chance that it would warm up a lot compared to more colder, winter-like temperatures.

Today's forecast is quite different, with about a 40% chance of our first snow of the season coming early next week.

However, there is a fine line here between just plain cold with some wet snow and really cold with an accumulating snow.  And, of course, for those who don't like winter weather -- there is a 40% chance it will be just wet, and even a 20% chance it won't rain at all (the warm and dry scenario).

I plan to provide an update later today or tomorrow.  Hopefully, there will be enough information in the model to indicate which scenario is more likely.

Barry Lynn

Friday, December 9, 2016

Weather It Is (Wet)

Good Afternoon:

Next week's storm has been in the news.

However, the latest Global Ensemble Forecast System run suggests that rain is likely on Tuesday into Thursday (with strong winds), but that the real cold air will stay to our north.

There is a 15% chance that temperatures will fall off to freezing or below after the storm passes, but the next chance for something really cold (and snowy) isn't until the week after next, and chances are not very high.

So, we're in for a period of typical winter weather: cold and rainy from time to time.

Shabbat Shalom,

Barry Lynn

Wednesday, December 7, 2016

Weather It Is (When I Was A Kid)

Good Morning:

When I was a kid I used to like to talk about the weather.  So, one might wonder why I haven't been speaking about the weather for the last week.  I really wanted to say something, but as Joe Friday of "Dragnet" might have said: "give us the facts, Ma'am," which is not the same as "just the facts, Ma'am."  The first implies uncertainty, while the second implies certainty (and we're not).

Also, my mother used to complain when I provided more than just a cursory appraisal of the next storm, as she too wanted just the facts.  After all, I had given her some rather useful hats and other sundries to keep her warm, and I am sure that she wouldn't have wanted to arrive at school with the wrong ones, and then have to explain that her child really didn't have the facts, or at least the right ones.

So, that is where we are:  I want to say it, and I want to write it, but the forecast models we have are not capable enough to predict the next two weeks. If they were, then the possibility of our next snow storm would not come and go even on the 10 day forecast. I mean, if there was a 20% chance of a mid-December snow storm a few days ago, and then no chance, and now its back, this indicates that the global forecast models just don't have enough information (or physics capability) to forecast this far in advance.

So, the facts are the GEFS 12 UTC forecast model is indicating that mid-December just might bring a very early snowfall to even the Jerusalem area.

The probabilities are about 25%, which theoretically means that three-quarters of the time we write this blog it won't snow then.  On the other hand,  since the forecast models are somewhat data sparse in the areas where the real cold originates from, the possibility of snow may really be higher.

We will see in the next few days whether we should get excited enough to hope for the details to show themselves in our higher resolution forecasts.  If they do, I plan to produce some longer higher range higher resolution forecasts than currently on the site, to give an advanced look at just what may be.

Send your thoughts and/or comments or numerical weather forecast tidbits as you see fit.

Barry Lynn