Friday, February 27, 2015

Weather It Is (Uncertainty)

Good Afternoon:

We're actually pretty sure that it is going to get cooler as Erev Shabbat turns into Shabbat day.  However, we're pretty uncertain what the cooler, if not chilly air will lead to.

We see a broad ridge of warm air forming over the eastern Atlantic and pushing its way into western Europe. At the same time, the northern Jet Stream will become very active and winter like.  Some of the cold-air energy should merge with a southern Jet Stream trough and bring the possibility of rain on Tuesday and Wednesday of the coming week.

Yet, even though this is clear, there is a lot of uncertainty in just how strong this feature will be or how much of the cold air it will tap on its way across the Mediterranean.  A stronger trough and there will be more rain with possibly strong winds.

While it may warm up a bit on Thursday and Friday from the Wednesday chill, we see a general turning of the winds to the northwest.  Yesterday's GFS showed a sharp ridge forming over central Europe and cold air diving into our area on Shabbat of next week and the week after.  Such a scenario would bring us wet snow or even snow.  Today's GFS rounds off the ridge a bit and the coldest air stays a bit north of our area.

The GFS ensemble shows a 20% chance that the ridge will sharpen and the trough deepen enough to return us to a snowy winter. Otherwise, there is the likelihood of rain next Shabbat or early next week with cool or chilly temperatures.

Shabbat Shalom,

Barry Lynn

Thursday, February 26, 2015

Weather It Is (Strange Motions)


Good Afternoon:

Highlight:

A warm day, followed by cooler weather next week, and a chance of snow early the week after next.

When people see me they make strange cutting motions with their hands (about waist high).  They also shake their heads -- perhaps in an ominous way. Are they asking, or are they telling me (no more snow, bring on the spring!)?

There are even those who choose to apply blame even when none is deserved.

http://www.timesofisrael.com/false-israel-drowns-gaza-claims-sweep-internet/

The weather will be warming up, but it won't feel toasty.  True, it will be pleasant, but it will last just one day (into Friday Evening), and then the temperature will start downwards again on Shabbat.

In fact, as Purim comes around an area of low pressure should approach from the west.  It may not be a particularly strong area of low pressure, but it could bring a period (or periods) of light to moderate rain.  It should be cold enough for some snow on the Hermon.

Looking further ahead to Shabbat and early the following week.  We still see a 15 to 20% chance that this period could turn quite cold and perhaps even snowy.  Of course, like last time, there is an 80% chance that nothing will come of this, but rain.

Barry Lynn

Wednesday, February 25, 2015

Weather It Is (Palestinian Black Mail/Purim Snowmen)


Good Morning:

It is extremely satisfying to read in the papers that a jury in Manhattan ruled against the Palestinian Liberation Organization and Palestinian Authority.  They basically convicted these organizations of murder.

http://www.timesofisrael.com/the-11-families-at-the-heart-of-the-landmark-palestinian-terror-trial/

Of course, the list of plaintiffs is only a small sample.  The stories of others murdered by Palestinians cast a dark pall over my feelings: for example: the husband and wife blown up outside a building after learning that the wife was pregnant with twins.  Nearly entire families murdered in Gazaand and Itimar.  A father murdered on his way to Passover Sedar (he was not the only target).  A young lady murdered in Gush Etzion, residents of my town. A Passover Sedar blown up, buses... These are select people and selected areas, but the Palestinians have been an equal opportunity people, not discriminating by place, time, or person (man, women, children).

Moreover, they continue to blackmail us:  unless we agree to all of their "peace" terms, they will sue us in International Court -- even though these terms sign our death warrant and make false assumptions about international law itself.  They don't pay their electricity bills and expect us to continue to provide free electricity or they will riot.  We need to provide food, electricity, and building materials to Gaza, or they will shoot missiles now rather than later (after they have used these materials to build tunnels under the border).

Moreover, the proclaim a state that has no borders and can't even come close to balancing its budget!  It almost seems that the only thing they (as in the leadership and that percentage of the population that supports them) take seriously is their efforts to rid the world of us -- everything else is commentary.

Enough of this.  Perhaps we need to let them implode (or explode),  and hope that "survival of the fittest" will see a moderate voice emerge.

Regarding our weather, it is really a mishmash.  Or rather, the circulation pattern is a mishmash of relatively small waves.  One of those waves will approach us in the next few days and bring steadily increasing temperatures.  In fact, it will be about 10 to 15 C warmer than it has been. But then by late Shabbat the wave will pass through and it will be as cold as it was, and possibly not as cold as it will be.

By Purim time, we see a greater possibility of rain.  At the moment, we can't tell how serious a rain and we can't tell just how cold it will get.  There is still about a 20% chance of wet snow in one of these more rainy episodes.  But, before we start dressing up like snowmen we should first wait and see which way the wind blows: wetter, or wetter and cold.

Barry Lynn

Tuesday, February 24, 2015

Weather It Is (A Little Training Helps)

Good Morning:


Good Morning;

"If you don't know how to use the rag [without cleaning it beforehand], use wipes"

"When I come up, don't be in my way -- be finished with whatever you have to do."

The other day I saw my wife replacing the windshield wiper of my car; I'd already tried.

When young women are dating, they ask whether the "Bochur" is a promising Rabbi, a doctor, lawyer, or maybe an aspiring artist.  They never imagine that the talents they think their future hubby to possess will never pass through the door of their home!  They don't imagine that their future husbands won't be able to change a light bulk (seen the  new LEDs?) or do simple time management out of the office.

And it is for this reason I write this blog.  It gives me a chance to explain to the women folk just the way things are -- so they can be a little more understanding.  After all, we never expect our dog to do much more than bark and wag his/her tail -- should there really be higher expectations for husbands? Not without training, of course!

(Of course, men might consider to be more appreciative of their wives, but this, perhaps, is the subject of a future blog.)

I also write this blog because I like to give its readers not only useful information, but some knowledge about the physical processes that come together to make our weather.

For instance, there will be scattered showers in our area during the next few days.

Looking ahead, we see a trough trying to build in eastern Europe, eventually extending down into the eastern Mediterranean.  It will do so as a ridge noses its way into central Europe.  The combination of the trough and ridge will enhance the southerly flow of air from the cold reaches of the north.  Hence, the two systems acting together could make for an unusually cold Purim as cold Siberian air heads southward.

At the moment, there is not anything we can definitely say other than with the exception of a day or two of more spring-like warmth, the temperatures will remain winter-cool/cold.  How cold, we'll let you know.

Barry Lynn




Monday, February 23, 2015

Weather It Is (February 20/21st Storm Testimonial)

Around midnight we had the 3rd and final wave that hit us and the stuff the clouds threw at us was wild.  It seemed to be, at one time, a combination of hail, large grapple and snow. Man, it sounded like our house was being hit by a barrage of snowballs. Big chunks of stuff struck our windows, stuff that was too soft to be hail but too big to be snowflakes. These were snowy clumps that fell out of the sky such that I have never seen nor heard of.  What was that? Monster grapple?

Also the lightning that we had on erev Shabbat was of an intensity and frequency and overall duration of the waves of storm that came in that neither my wife nor I have experienced in our 34 years of living in Gush Etzion.

That was quite a storm, one of which will be hard to forget.

P.S. The storm continued as such until morning.

Sunday, February 22, 2015

Weather It Is (That 20 Year Itch)

Good Afternoon:

Every Purim we talk about it. Finally, I have it on good authority that it snows not every Purim -- but every 20 years on Purim.  So, it snows on Purim at least once a generation.  This is better than skipping a generation but not as good as I was led to believe by my wife (and others).

In the meantime, I am getting complaints about leftover snow.  For those who have had enough, the forecast is indicating a chance of rain on Tuesday and Wednesday.  An area of low pressure should move across the Mediterranean, picking up moisture as it goes -- until it crashes on to our shores. This just might wash away the snow, where the sun hasn't melted it already.

The areas of low pressure will actually be weakening as it makes its way our way because the atmospheric energy associated with the northern Jet Stream is shifting to the west.  In fact, during the next week it will shift so far west it will be in the northern Atlantic.

Even so, the forecast shows a weak trough redeveloping in the eastern Mediterranean with a weak ridge in central Europe.  This will keep things somewhat cool around here, as air flows southwestward from cold Siberia.

Getting back to our Purim forecast: the GFS ensemble shows some instability in the 500 mb circulation pattern, indicating a possible merging of the northern and southern Jet Streams. At the moment, there is a 15% chance of snow on Purim. Of course, there is an 85% chance of something else, but we're all optimists here.

Barry Lynn


Saturday, February 21, 2015

Weather It Is (Two Storms, Different Outcomes)

Good Evening:

The last time the Jewish people experienced a hail storm like Friday night's, they were in the desert of Egypt and they didn't worry about the power being knocked off in a burst of lightning. Perhaps, then, it is a bit ironic that this prelude to leaving Egypt, and coming to the "promised" land -- was simply another prelude for a hail and lightning show.

One can probably describe the two halves of our recent storm as "polar opposites." The first half brought heavy snow (19/20 of February), while the second half brought continuous hail (20/21 of February).  In the first, the snow fell like a whisper; in the second, the hail fell like a percussion band (and the thunder to go with it sounded like a bass drum).

The first half was associated with extremely cold upper air temperatures and below freezing surface temperatures.  The second was also associated with cold upper air temperatures, although not as cold as during the snow part of our storm.  Temperatures at the ground were also warmer in the second hail storm, and a relatively mild and moist middle layer meant two things: the atmosphere was very unstable (conducive to thunderstorms) and that there was lot of riming of snow particles to produce graupel (what we're loosely calling hail here).

Most importantly, the collision of graupel and ice/snow particles in the presence of liquid water produces lightning, and there was a lot of lightning in the second part of our storm.

In fact, the second storm was remarkable for the duration of the hail, numerous and repeating thunderstorms, and for the fact that the hail accumulated on the ground throughout the night, even though the temperature never fell below 2 C (here in Efrat).  Had surface temperatures been a bit colder, we might have awoken to 20 cm of hail (really graupel that looks like snow-ice cubes).  Instead, as the hail melted, it was continuously replenished.

The top figure below show Jerusalem forecast rain accumulations ("rain-accu"), snow accumulations, and hail accumulations from the snow storm, while the bottom figure shows the same from the hail storm. The rain-accu is the sum of any rain, snow, and/or hail that falls.  We also show the forecast snow height (what we usually refer to as snow amounts or accumulation).  The snow height is what we have after snow falls and some of it melts.

During the snow part of our storm, the snow height was quite high (surface temperatures were very near of below freezing).  Moreover, the snow accumulation was about four times the hail accumulation. In contrast, the second storm produced almost four times the amount of hail versus snow accumulation. Moreover, there was plenty of water "left-over" to cause lightning in the presence of snow and ice/graupel particles.

In our early blog on Friday, we mentioned that the second storm would accumulate only light amounts.  What we didn't mention was that this light accumulation would mask such dramatic atmospheric processes leading to tremendous hail and lightning.

Like we did after the January snow-storm, we have modified our forecast output to more clearly show the types of precipitation reaching the ground, so that we can better convey the message we all need to hear to improve weather preparation and safety.

Barry Lynn

Weather It Is (Roads Will Freeze Over)

Good evening:

Our surface temperature forecast shows that the air temperature will drop to about 1 or 2 C, but that surface temperatures (including roads) will be cold enough to freeze slush and water. This will happen on roads that have an open sky to radiate their heat into the night, and will be most prevalent in higher elevations.

Hence, travel tomorrow morning should probably be delayed until the sun warms the streets (around 8 A.M).

Barry Lynn

Friday, February 20, 2015

Weather It Is (Thunders-Snow/Hail)

Good Evening:

Periodic thunderstorms with hail and snow will accumulate 2 to 5 cm in areas of Jerusalem, Gush Etzion, and Sefad.  The hail can cause roads to become locally slippery, and in higher elevations the roads may develop a layer of icy slush.

This weather situation will continue until early morning, as temperatures hover just above freezing in most places.

Barry Lynn

Weather It Is (Winter Storm Noon: Update)

Good late morning/afternoon:

The precipitation with this storm has moved south, and after 10 to 12 inches of snow (25 to 30 cm) one might be tempted to say: enough! On the other hand, those who saw snow even at relatively low elevations probably wouldn't mind some more.

Yet, the break in the precipitation will allow for temperatures to rise two to three degrees, and the rise in temperatures will make any further snowfall accumulation hard to come by.  Moreover, temperatures at 500 mb will be warming about 5 C, while temperatures at 700 mb and 850 mb tack on a couple of degrees of warmth. The result will be that atmospheric temperatures become marginal for snow.

Where does this leave us with this afternoon's late precipitation? It means that areas of high elevations should receive some wet-snow, and that snow could accumulate after midnight as the lower atmosphere cools a bit.  It will be a "close-call" as they say.

Har Hermon: 20 cm
Golan: 5 cm
Sefad: Bet-Jann 5 cm
Jerusalem area: just mixed rain/snow -- just slush if that.
Gush Etzion: light accumulation at night.

There may be icing in the high elevation of the center and north Saturday night.

Warming on Sunday and Monday, with rain (snow on the Hermon) on Tuesday/Wednesday possible.

Shabbat Shalom,

Barry Lynn


Weather It Is (Friday Morning's Winter Storm Warning)

Good Morning:

Our latest 12 UTC and 18 UTC forecasts restored the heavier amounts of precipitation (somewhat "lost" in the 6 UTC run).

The forecast snow amounts remain fairly consistent from the previous values given.

The temperatures are zero or below in Jerusalem and the surrounding area, as well in the environs of Sefad.  They are expected to rise slightly in mid-to-late morning, which may hold down accumulations a bit (as previously noted) except in the highest parts of Jerusalem.

Our model shows that about about 50% of the precipitation forecast will convert to snow accumulation in Gush Etzion (and Sefad), while about 25% elsewhere.  These percentages are very temperature dependent and a small change in surface temperatures downward would bump up the total snow amounts in some neighbourhoods of Jerusalem (we just don't forecast this yet).

It is worth mentioning that our 12 UTC 4 km ensemble gives a burst of precipitation between 8 AM and 11 AM, which could bring 8 to 16 cm more of snow on top of what we'll have up to then.  The probabilities range from about 60% in Jerusalem to 100% in Gush Etzion (Efrat Southward).  If this strong surge occurs, it could also add several centimetres of snow to the amounts shown below.

In summary, our current forecasts have the snow transitioning to a "wetter" snow in the Jerusalem area around mid-morning, but not until noon/early-afternoon in Gush Etzion.  This accounts -- for the most part -- for differences in forecast snow amounts.

Here they are:

Snow accumulations are valid until 2 P.M tomorrow.

Hermon: 65 cm
Golan: 25-35 cm
Gush Etzion: 30-40 cm
Jerusalem: 20-25 cm, including about 15-20 cm in the Old City.
Bet-El/Har Bracha: 15-20 cm
Sefad: 10 to 20 cm.
Ramat Bet-Shemesh, Kefar Giladi: up to 5 cm.

Another round of precipitation is expected later in the afternoon into Shabbat morning. It will probably be mixed rain and snow, wet snow, and just snow, depending on elevation.

Barry Lynn

Thursday, February 19, 2015

Weather It Is (Evening Update)

Good Evening:

Forecast temperatures are consistent with past forecast output.

The 4 km ensemble and 1.3km forecasts still show the heaviest precipitation to fall from about 02:00 in the morning to about 11:00 AM. We still show warming morning and afternoon temperatures.  If this occurs, snow amounts will be closer to what we predicted compared to other forecasters.

Also, precipitation amounts are bit lower than previous forecasts. I tend to believe, though, that the 06 GMT update is not quite as accurate as the others (as there are fewer airplane observations over Europe).

Good night,

Barry

Weather It Is (The Right Decision?)

Good Evening:

I was asked on the Josh Hasten radio show whether the Moatza made the right decision in closing schools today.

In retrospect, it was a mistake closing school. Even so, they made the right decision.

One must keep in mind that they followed their forecasters advice, advice that they most likely pay for.  In this respect, they had no choice but to close school.

I like to think (and I believe that others will bear witness to my statement) that we provide the most accurate weather forecasts in the country. We do this through both forecast model development and by using these models at very high resolution to more accurately forecast local weather variations.  We also run an ensemble forecast that provides us with probability that the weather will produce certain threshold amounts of precipitation and/or temperature.

Even so, we are not 100% accurate, nor is their weather forecaster 100% wrong (probably far from it). Hence, the correct approach is to weigh both forecasts and decide whether the risk and potential loss outweighs the cost of taking a particular action/or not.

Regarding tomorrow's forecast: Meteotech and others are predicting heavy snow throughout the day tomorrow (Friday). Our forecast shows that the temperatures should warm in the late morning (here), mid-morning in Jerusalem, keeping accumulations from approaching the 50 cm predicted by them. In fact, the 6 GMT forecast produces a bit less snow for us (and Jerusalem) -- simply by lowering the total precipitation amounts.  However, our 6 GMT forecast is generally less accurate than the other time slots.  We'll see "who" is correct tomorrow.  In either case, most will probably prepare for what is most likely, but also have plans for what might be.

Barry Lynn


Weather It Is (Differences: between January to February's Snow Storm)

Good Afternoon:

Here are some important differences between tonight's predicted snowstorm and last January's storm.

1) Temperatures from the surface to the upper atmosphere are 1 to 1.5 C colder than in the January storm.

2) Predicted amounts of precipitation are about twice in this storm compared to January's.

3) Our high resolution model predicts temperatures at freezing or just below in Jerusalem (compared to 1 to 2 C above).

4) Our highest resolution model predicts on average 20 cm of snow in Jerusalem compared to 5 cm in the previous storm.

5) The heaviest snow should fall (outside of the Golan where it is already snowing) in the Jerusalem area, including the mountains (e.g., Har Bracha) immediately north of Jerusalem and the area of Gush Etzion.

Barry Lynn

Weather It Is (Noon Update)

Good Afternoon:

Winter Storm Warning:

Snow beginning in the late afternoon/evening, except in the Golan (where snow begins around noon).

Accumulating snow begins in Gush Etzion around 5 P.M.
Accumulating snow begins in Jerusalem between 9 and 11 P.M
Accumulating snow begins in Sefad between 6 and 8 PM.

Moderate snow if expected to begin after 9 P.M.  Heavy snow is expected to fall at the rate of 5 cm/h from about midnight until 6 A.M.  Chance of snow 100%.

Temperatures fall below freezing between 9-11 P.M in  the areas of Jerusalem and Sefad.  They remain below freezing until mid-morning.  Wet snow or rain and wet snow continues from mid-morning on into the afternoon on Friday.

Snow accumulations are valid until 10 A.M tomorrow.

Hermon: 50 cm
Golan: 25 cm
Gush Etzion: 25-30 cm
Jerusalem: 15-25 cm, including about 15-20 cm in the Old City.
Bet-El/Har Bracha: 15-20 cm
Sefad: 5 to 15 cm.
Ramat Bet-Shemesh, Kefar Giladi: up to 5 cm.

Possible freezing of roads Saturday evening/night.

Barry Lynn

Weather It Is (Update for Gush Etzion)

Good Morning:

Our forecast model shows that temperatures will reach a high of 4 C today, and remain about 4 C until about 2 P.M.

At 2 P.M, the temperatures should fall to about 2 C as rain intensifies.  

Between 2 and 3 P.M, it should begin to snow about 1 cm per hour until early evening.  However, temperatures won't begin to fall further until about 7 P.M.  Heavy snow should arrive after 9 P.M as temperatures fall below freezing and continue until tomorrow morning.

In other words, it should be too warm to accumulate significantly until evening.  True, there might be some snow on colder surfaces, but it shouldn't "stick" in any serious manner until tonight.

Tonight, the snow will fall at a rate of 6 cm per hour, which is greater than 2 inches per hour for several hours. 

We will update this forecast, God willing, around noon.

Barry Lynn

Weather It Is (Winter Storm Warning/FLood Warnings)

Good Morning:

A major winter storm will affect the entire country from Thursday morning into Friday night.
As per my last post, temperatures are cold enough to support the development of heavy snow, with snow possible down to elevations of 350 m.

Unlike the last storm, which affected the areas north of Jerusalem with heavy rain and snow, this storm will affect the entire country.  Heavy rain, heavy snow, gale force winds, and dust.

Our 1.3 km forecasts extend out to Friday morning 8 A.M.  We see accumulating snow continuing in the Jerusalem area until about then.  The late morning update will tell us how much warming is expected with the moist air arriving off the Mediterranean and if any accumulation will continue beyond this hour.

Here are he specific warnings and advisories.

Winter Storm Warning for Gush Etzion from 2 P.M Thursday onwards through Friday morning.
Winter Storm Warning for Jerusalem area from 8 P.M onwards through Friday morning.
Snow Advisory for area of Sefad from 6 PM until Friday morning.
Golan: Winter storm warning from mid-day through Friday night.
Snow Advisory for areas down to 350 m, including Ramat Beit Shemesh, Kefar Giladi for tonight after 9 P.M.

Here are the latest snow forecast totals.

Hermon: 50 cm
Golan: 25 cm
Gush Etzion: 25 cm
Jerusalem: 10-20 cm, including about 15 cm in the Old City.
Bet-El/Har Bracha: 15-20 cm
Sefad: 5 to 15 cm.
Ramat Bet-Shemesh, Kefar Giladi: up to 5 cm.

Wind Advisories: 
Coastal areas: gale force winds (60 km/h) with higher gusts from noon onwards until Friday morning.
Inland: strong winds (40 to 50 km/h) with higher gusts from afternoon until Friday morning.

Flood Advisories:
Jordan and Dead Sea Valleys: from afternoon Thursday in Shabbat.
Northern Negev and Arava down to Eilat:  (25 to 50 mm of rain will fall southward to Mitzpe Rimon; 5 to 25 mm south of this line).
Localized flooding in coastal cities due to 25 to 50 mm of rain from Thursday afternoon.
Localized flooding in cities in the north due to rains > 50 mm.

Lightning: with convective storms, including thundersnow.

Dust advisories: for Negev and Arava until Friday noon.




Wednesday, February 18, 2015

Weather It Is (Winter Storm Warning: Noon Update)

Good Afternoon:

The latest high resolution model forecast now extends until midnight Friday.  The following snow and rain forecasts represents the latest forecast information from the 4 km forecast model.

To understand the forecasts below, it is important to note that the latest synoptic scale pattern has changed for the colder.  Average minimum temperatures are down to -31 C in the Jerusalem area at 500 mb, -14  C at 700 mb, and -3 C at 850 mb.  Moreover, more precipitation is predicted to fall than the last update in the Jerusalem area. This means that the snow should fall a bit heavier and for a few more hours in the morning on Friday than in the previous forecast expectation.

The snow forecast has also evolved to favor the center of the country at the expense of the area of Sefad and the Golan. The reason for this is that the precipitation amounts in the center are suppose to be about twice those in the north.

Here are the latest snow forecast totals.

Hermon: 50 cm
Golan: 25 cm
Gush Etzion: 25 cm
Jerusalem: 10-20 cm, including about 15 cm in the Old City.
Bet-El/Har Bracha: 15-20 cm
Sefad: 5 to 15 cm.

If nothing significant changes in the forecast synoptic pattern, then these values are conservative snowfall projections because they are from the 4 km versus the 1.3 km gridded forecast.  However, changes in the forecast synoptic pattern can, as noted, change the forecast snow amount irrespective of any impacts of changing the grid resolution to 1.3 km within 36 hours of the event. Yet, all of the 500 mb temperatures are now below -30 C, with some as low as -33 C, so the potential for changes in the forecast snow amounts because of changes in the synoptic pattern is somewhat less than the previous forecasts. 

Regarding the forecast for Friday night, there is a 10% chance that another surge of cold air will enter the system, extending snowfall into this period.

Additional note: the area of potential flooding will extend through Gaza eastward to Beer-Sheva, where 50 to 100 mm of rain will likely fall.

Barry Lynn

Weather It Is (Winter Storm Warning)

Good Morning:

Highlights:

Snow: Most snow should fall in Gush Etzion and the Golan. Rising temperatures should reduce snow accumulation in Jerusalem on Friday morning.

Winds: Gale force winds along the coast late Thursday afternoon into Friday.

Rain: Heavy rain inland Thursday night and Friday, leading to city flooding in the north and possibly in coastal areas, Jordan Valley, and Dead Sea Basin.

Dust: Heavy Dust from Jerusalem southward tomorrow morning.  High dust concentrations in the desert Thursday night and Friday.

The discrepancy between the US Global and European models has been resolved, and the US Global model (both deterministically and as an ensemble) came out ahead.  This might be a bit disappointing to snow lovers, who were hoping that this storm would rival the three day storm  of December 2013 (even in Jerusalem). On the other hand, if one sets his/her sights on the snow of Boston (or closer to home: Har Hermon), no one would ever be satisfied.  One can even go back to 1992 where the snow was hip high (and this from a relatively tall person).  Nevertheless, the snow is coming and it should accumulate.

The authors of this article from the Times of Israel keep repeating this statement:

Last week, forecasters predicted a heavy snowfall throughout the country, but the storm brought heavy rain, dust storms and gale force winds to most of Israel instead.

Read more:
 Israel braces for major winter storm | The Times of Israel http://www.timesofisrael.com/israel-braces-for-major-winter-storm/#ixzz3S42D3dGw 

But, this is simply wrong.  We repeated over and over again that last week's storm would arrive from the west.  As the storm would be resident over the sea for quite a while, the sea would warm the lower atmosphere, making it most likely that a wet snow would fall only in the highest elevations, but the Golan (where "real" snow fell"). We also pointed out that the marginal temperatures would result in a high melting rate. True, the path over the sea would bring lots of moisture, but for snow to accumulate it must remain a couple of degrees below zero in the lower atmosphere or be exceptionally cold aloft (at 500 mb).  We didn't see these conditions with this storm.

In fact, the forecast for heavy rain, exceptionally strong winds, and heavy dust concentrations was very accurate, including the prevalence of dust, not rain in the Jerusalem area.

This storm, in contrast, will arrive from a much more northerly direction and this will help to maximize the cold air available to this storm to produce snow. 

The cold air at lower levels will arrive towards evening, while the coldest air at highest levels should arrive from midnight to noon on Friday.  As the coldest air arrives aloft, the lower atmosphere will warm slightly as moisture flows in off the sea.  It's here that the forecast gets complicated. 

It will be exceptionally cold aloft from mid-night Thursday to Friday morning (in fact, the mean ensemble 500 mb temperatures are about -30 C in the Jerusalem area, with a range of -28 C to -34 C).  While a period of heavy snow even in Jerusalem is likely late night, there is the possibility that warming temperatures Friday morning will hold down further snow accumulations in the Jerusalem area on Friday morning, and more rain than snow is expected in the afternoon because of continued warming of surface temperatures.  

Unless anything changes in the atmospheric pattern (i.e., there is another injection of cold air), the snow should taper to light to moderate rain in many places sometime Friday afternoon and night, and end as showers on Shabbat.  

In most place, snow should begin to fall in the late afternoon or evening, depending on elevation. Here are the expected snowfall amounts from the 4 km forecast through 8 IST Friday morning. These numbers are conservative numbers, as they arrive via our 4 km forecast.

Hermon: 50 cm
Golan: 25 cm
Gush Etzion: 15 to 25 cm
Jerusalem: 5-10 cm
Bet-El/Har Bracha: 10-15 cm
Sefad: 5 to 15 cm.

Otherwise: 

Gale force wind expected late Thursday afternoon along the coast into Friday morning. Strong winds elsewhere.

Precipitation amounts: 25 to 50 mm along the coast, 50 to 100 mm inland.

Flood Potential in many locations from Thursday night onwards, including the Jordan and Dead Sea Valleys.

High dust concentrations from he southern Jerusalem area southwards from Thursday morning, with high dust concentrations sinking southward to the desert areas during the storm

Barry Lynn




Tuesday, February 17, 2015

Weather It Is (Snow Advisory)

Good Afternoon:

The latest forecasts continue to converge around a snow event for the center of the country.  Hence, we've issued a "snow-advisory," which may be upgraded to a "winter-storm-warning" Wednesday afternoon for Thursday afternoon into Friday.

Our latest high resolution forecasts show rain or mixed wet-snow/rain Thursday morning becoming snow on Thursday afternoon in Gush Etzion and Sefad, and snow Thursday evening in Jerusalem.  All snow is expected on the Golan on Thursday and Thursday night.

Here are predicted snow amounts from our 4 km 36-72 hour forecast.

Effective until 0200 IST Friday morning.

Jerusalem: 2 - 5 cm
Gush Etzion 5 to 10 cm
Hermon 40 cm
Higher elevations of Golan 10-25 cm

These amounts are conservative values because they come from the 4 km forecast, which resolves well, but not "completely" the altitude of the topography.  Our 1.3 km forecast will be available Wednesday Evening for Thursday afternoon/night.

For the rest of Thursday night and Friday morning, accumulating snow is expected in all areas.  However, beyond Friday afternoon there is some model disagreement about whether a continuing, accumulating snow will occur in all areas into Shabbat, or only in the Golan.

Along the coast, expect around 25 mm of rain by 0200 IST Friday morning.

Winds will be around 60 km/h along the coast Thursday afternoon/evening (with higher gusts), and 40 to 60 km/h in the inland mountain areas.

Expect heavy dust concentrations on Thursday from about Beer-Sheva southward.

Barry Lynn




Monday, February 16, 2015

Weather It Is (Winter Storm Watch)

Good Afternoon:

Quote of the day: "Boston has gotten more snow in three weeks than Chicago has ever gotten in an entire winter." (JC, Boston.)

In the last three weeks, Boston has had more than 100 inches of snow (or about 3 meters worth).  We've add 12 inches out here in Gush Etzion.

In our neck of the woods, the forecasts are trending towards a snow event beginning sometime Thursday, extending into late Friday, and possibly lasting into Shabbat.

Temperatures at 850 mb and 700 mb are indicating that we'll be 1 to 2 degrees colder than we were in the January snow/non-snow event, and much colder than we were in the storm of last week that brought mostly wet snow to many locations in the north.  The difference is that last week's storm came from the west over the sea, while this storm should arrive from a more northerly direction. The probability of a wet snow is 80%, and the probability of a dryer, more accumulating snow is 40%.

At the 500 mb level, where cold temperatures are an indication of the potential for heavier, convective snow,  there is a 30% chance that we'll have periods of heavy snow in thunderstorms.

In order to accumulate a lot of snow in the area of Jerusalem, we need the colder forecasts to verify. Otherwise, periods of snow might fall and melt quickly. We've probably already reached the point where we can be reasonably sure of at least a wet, accumulating snow in the area of Gush Etzion and Sefad. The question in these areas is whether it will be more like the snow of Wednesday night/Thursday (wet) or more like Friday evening's dry, fluffy (quickly accumulating) snow.

Otherwise, we'll wait until Wednesday to change the Winter Storm Watch into a Winter Storm Warning and provide more exact numbers about expected accumulation.

Elsewhere, snow will fall on the Hermon and Golan.  At the moment, 25 to 50 mm of rain are expected along the coastal areas and inland hills.

Barry Lynn

Weather It Is (Winter Storm Watch/Men Learn Slowly)

Good Morning:

Had she her choice, we would be living at the beach (at least in summer).  Had I my choice, we would be living on the Golan (in the winter).  In the meantime, we have to deal with more mundane issues -- like the kitchen.  (More on the weather later.)

Did you know that my son was mad at me for not mentioning that it would rain yesterday? It is not enough to help with his homework, I have to be his weatherman too!

Have you noticed that no matter how early a husband goes up to use the "parents" bathroom, it is never too soon for the wife?

Anyway, for years I have been off and on in the kitchen -- especially on Fridays before Shabbat.  Why?  I like chemistry and I like to eat (I also like good smells).  For years, I have also been an "irritant."  It is not anything that I particularly do, but rather that it is hard to finish and clean up before the wife's turn on Friday to cook.

So, it was with utter amazement I learned a lesson -- 15 years in the making).  It happened one week that I had to switch my cooking time to Thursday, and Friday the sun shone and made the kitchen counters sparkle.  What a day -- a day of relaxation, happiness, and plain thankfulness (for being out of the way).  So, after 15 years, I made Thursday my cooking day.

Then it happened:  when my wife saw me so relaxed on Friday she asked herself why she could not also benefit from cooking on Thursday, and once again the mess became a mess at the wrong "time."  My wife, in contrast, learns things much more quickly than I.

So it was that the renovator came and built us a new kitchen in a small closet downstairs.  As he was leaving, he pointed out that he was glad that we did this early because most folks wait until Peach to put their Passover kitchen in...

This week, I am holding my weather cards close to my weather vest.  I don't want to raise expectations and I don't want my son to be mad at me.  So, I will only say that it may not be Boston, but it may be a winter wonderland come the end of the week. In fact, there has been a lot of model consistency (on the European side) pointing towards a storm entering from the north with plenty of cold air to make it snow, even in Jerusalem.  Otherwise, the US Global Ensemble is moving in the same direction. How much of a winter wonderland?  More on this, hopefully. later this afternoon.

Barry Lynn


Sunday, February 15, 2015

Weather It Is (Winter Storm Watch)

Good Afternoon:

While it hasn't always been wet, there have been at least a few opportunities for snow in the higher elevations of the country, and that has been snow or wet snow in the north.

We are again faced with another opportunity for snow in the higher elevations of the country, including Jerusalem.

Assuming that our ensemble models faithfully represent the potential variability in the weather, then when we say that there is a 30% chance of snow, then it should snow at least 30% of the times we say this.

The (weather) problem for those of us living in Israel is that our opportunities are often quite limited. For example, if we had just one opportunity a year, we would expect snow three times every 10 years.  This is a long time to wait!

Yet, this year has been different (as noted above) than those of the past as our opportunities seem to be more frequent and we're able to actually get a stronger indication for the accuracy of our models (especially factoring in the last few years).  The results are pretty favorable.

So, here it goes: we see a 60% chance of unseasonably cold weather (temperatures near zero) from late Wednesday into Shabbat.  This would likely produce a period of light snow, possibly coating the ground in Jerusalem with several centimetres of snow in the areas of Gush Etzion, Sefad, and the Golan.

We see a 25% chance for extreme cold and for a major snowstorm that will (possibly) end our winter on a very white(dry snow) note.

Otherwise, periods of rain should overspread the country with possibly strong winds during this period.

Barry Lynn

Saturday, February 14, 2015

Weather It Is (Crying Wolf!)

Good Evening:

Snow wise, there has been a lot of disappointment this year for those of us living in the area of the central mountains.  The phrase: "crying wolf" is one that might be ascribed to us meteorological folks.   Even if the storm did pretty much what it was predicted (closer to its arrival) -- there was a lot of hype with this storm.   Moreover, grazing the Jerusalem area with some snow showers while dumping a lot of slush in the Galilee mountains was quite disappointing for those who dream of a snow like that of December 2013.

Yet, when I saw the dancing of raindrops on the roof windows and the streets below, I felt a moment of satisfaction.  For, its not enough to just talk the walk, or walk the talk, one has to bring the merchandise, and so we did -- the rain to wash away dirt from the stones of Jerusalem.  Having one good forecast under my covers, I slept the sleep of the tired, the sleep of the spent, the sleep of the weatherman who has had a hard week!  One who knows that every word he says will be parsed twice -- and a third time if things don't work out as hoped.  It's a very hard life, but the thrill of catching the big one makes it all worthwhile (as well as providing a little helpful advice from time to time).

Before I get to the important stuff, here is a quick primer on predicting snow.

1) Identify from the global forecasts possible conditions for snow in the higher elevations of Jerusalem, etc.   It's not enough to be wet, it must also be unusually cold.  Or, it's not enough to be unusually cold, it must be wet (as I keep telling my son).

2) Use the global forecast ensembles to assess the probability of the storm occurring -- so far this winter, we're doing great in this regard.

3) Once we get within three days, use our high resolution forecasts to see just how wet and just how cold, and to see just how much snow is predicted to accumulate.  These models have been excellent.

4) Within a day, use our highest resolution forecasts to refine our snow even more.

5) Use our high resolution ensemble to asses the probability that snow amounts might exceed certain values.

An example:  In the last storm, we saw from the global models that it would generally be very wet, but not quite cold enough for a good snow.  As we got closer, we saw that the storm's heavy precipitation would skip Jerusalem, bring slush to the Galilee mountains, and that indeed it would be too warm for heavy snow, except in the Golan.  The day of, we saw that the Jerusalem area would get some snow (it did snow briefly out here), but the chance of any accumulation of was only 50% -- and even this was just an indication of the potential for heavier shower of snow (that didn't  happen).

Another example: in the previous January  storm, we relied too much on the general picture, and didn't really put enough credence in the fact that our high resolution models showed the night before and day of the storm that temperatures would be cold enough for snow, but not for a really high accumulation.

Lastly, in the December 2013  storm, we could see the cold and the wet well in advance.  Then a day or so before, we used our high resolution model to confirm that indeed there would be a heavy snow accumulation.

Which leaves us with the mid-week storm that looks like it could be more like the December storm of of 2013 than the snow/non-snow storms of January/Feb 2015. Right now, the forecasts have a split personality: about 1/3 to half of them show a very intense storm impacting us mid-week, while the other half do not.  The ones that do show snow predict a phasing of the northern and southern streams and the arrival of the storm from almost due north.  This will maximize the impact of the storm's cold air on us.

By the way, the European model is also "crying wolf."  It also shows a good possibility of a major snow storm for our area.   This just in from a serious weather hobbyist in Jerusalem: "From my eye: the Euro has a trough that develops first over the next couple of days thanks to the current high that moves over Europe. This trough isn't deep enough at the beginning of the week, but then another surge of cold air fills it in directly from Russia and a storm develops at the bottoms of the trough. This storm then plunges downward toward Israel and gets cut off but still retains some of the incredible cold. As a result, from Thursday to Saturday, the Euro brings in 500's that get below -30 and 850's [mb temperatures]  that get close to -5 c all coupled with a slow moving storm that could potentially bring a lot of snow to Jerusalem."

Before we cry too loudly, though, let's take a look at the forecast tomorrow morning.

Barry Lynn


Friday, February 13, 2015

Weather It Is (Winter Storm Update)

Good Morning:

Highlights:

1) High Wind Warning coastal areas (south to north): Winds 50 to 60 km/h until evening. Central mountains and Galilee, Golan: 40 to 50 km/h. Higher gusts in all locations. 

2) Heavy rain from Netanya to northern Israel, with continued flooding along coastal areas, inland towns, and Jordan Valley.

3) Snow on the highest peaks of the Galill  and Golan. 

Our winter storm will eventually wind down, but not until more rain and some snow falls (at the highest elevations of the Galil) and Golan.

The storm continues to bring very high winds as well and some small amounts of rain to the center mountains later this afternoon/night.

The storm should wind down on Shabbat as it moves away, but it will be replaced by moisture from the Atlantic Ocean, moving across Africa. This will bring rain across the south on Sunday, which will eventually overspread the entire country. Flooding is a possibility in the southern areas on Sunday/Monday.

The trough of low pressure and colder air should redevelop next week.  We know it will be cold, but we don't know just how strong this system will be yet. 

Shabbat Shalom,


Barry Lynn

Thursday, February 12, 2015

Weather It Is (A Breather, Of Sorts!)

Good Afternoon:

I look out the window and I see winter-like (cold) clouds, full of ice. True, they are not very deep clouds, but with the wind and relative cold, it does seem like winter. The winds seem to be taking a breather, as the trees sway back and forth, but not with the same wild abandon as last night.

The wife comes home in her Eddie Bauer winter coat.  I ask: "cold out there?"  "Not really," she says.  She never wanted winter back and she is doing her best to ignore it.

However, even the stout-hearted will eventually start to notice.  Fortunately, the heavy dust is gone and the remaining dust is slowly slipping out of our borders (for the most part).  But, heavy rain will continue in the north.  Slightly warming temperatures will change the snow to rain in the area of Safed, leaving only the higher areas with the Golan (and Hermon) with continuing snow accumulations.  All of this should end late tonight or tomorrow morning (but return late Shabbat as rain except on the Hermon).

For us in the center, we should have light to moderate rain late Friday to wash away some of the dust.
This storm is also a cold one, especially at the higher levels of the atmosphere (e.g., 500 mb), but the surface temperatures will probably be too warm for snow.  Instead, there may be some ice/graupel.

Looking ahead, winter stays with us until mid-next week. It's at that point a decision will have to be made as high pressure reasserts itself over central Europe.  Will the northern branch of the jet stream couple with the southern branch of the jet stream as unseasonably cold air streams southward around this high?  Or, will winter putter along, or possibly warm as spring approaches?  The best chance is for puttering, but there is a 25% chance of something more serious.

Shabbat Shalom,

Barry Lynn

Wednesday, February 11, 2015

Weather It Is (Feb. 11: A Quick Update)

Good Afternoon:

There has been very little change in the model forecast output during the last day. other than to add or subtract a bit of precipitation from the Jerusalem area.

The IMS radar shows intense bands of precipitation inland from Netanya northward along the Israel coast. The band is just off shore of Tel-Aviv and will be impacting this city with heavy rain and strong winds quite soon.

The radar shows some bands of precipitation over the northern Arava south of Beer-Sheva. There are also bands of precipitation off the coast of Ashdod.

The forecast continues to show the heavy precipitation and very strong winds over the northern half of the country with heavy dust south of the precipitation cut-off.  However, the forecast also shows some of the precipitation making its way into the Jerusalem area within a few hours.  When these bands of precipitation arrive, they could whiten the ground and add a slushy layer to the streets.

Whether the convection from Tel-Aviv South is an omen for heavier precipitation in Jerusalem and vicinity will need to wait for another forecast or for reality to intrude and write its own history.

Barry Lynn

Weather It Is (I Hope He's Right?)

Good Morning:

In general, the forecast from yesterday remains unchanged -- except for some of the details about snow amounts.

A massive and intense storm will impact the country today into early next week.  The storm will bring with it very high winds, heavy rains, lightning, and snow in the higher elevations.  After the initial period of precipitation, the storm will receive additional cold air ("energy") and continue to produce precipitation into Shabbat.  General instability (cold air at upper levels) will remain into next week.

The latest forecasts indicate slightly warmer temperatures up in the north. Hence, snowfall amounts at elevations in the area of Sefad may reduced somewhat from previous estimates. A degree here or there will make a huge difference in amounts.  For instance, the Old City of Sefat is predicted to accumulate around 10 cm, but up in Beit Jann there will be between 25 to 50 cm by Wednesday afternoon.  This (in Beit Jann)  is about 40% of the precipitation converted to actual snow accumulation, compared to 75% in the storm of December 2013. This is not to imply that roads will not become snow covered, but there will be a lot of effort (on the storm's part) to accumulate snow, but relatively lower snow totals.

In the Jerusalem area, our highest resolution model still shows a sharp cut-off to the precipitation shield, lowering potential snow amounts in this area. Ironically, folks often worry about the forecast being correct, while here they might sort of wish that the forecast will be wrong -- or at least off a bit.

Yet, our 4 km ensemble indicates a slight shift southward of the precipitation, even as far south as Efrat (but not Hebron).  The probability of > 1 mm of precipitation is 100% in the Jerusalem/Gush Etzion area, while there is a 50% chance of > 10 mm in the center area of Gush Etzion.  This corresponds to 5 to 10 cm of snow in the Efrat, Alon Shavut, Kefar Etzion area, with a coating of snow possible in Jerusalem. The best chance for the snow in the Jerusalem area is the mid-afternoon to evening time.

The precipitation in the Jerusalem area should retreat to the north by around midnight.  Because of the relatively warm temperatures, the snow on the ground (if any) will have a hard time sticking around.  The storm will continue to rage in areas north of Jerusalem, while rain or possibly snow will return to the Jerusalem area Thursday night, and continue as rain or wet snow/rain during Shabbat.

Otherwise, a dust storm will continue to rage in the south -- south of the southern extent of the precipitation.

Barry Lynn

Tuesday, February 10, 2015

Weather It Is (At War with the Weather: A Storm of Massive Impact)

Good Evening:

One struggles to find the right words to describe the potential impact of the storm that will affect us in the next few days.

It has been the case that in times of war those living in one part of the country may be somewhat oblivious to what is happening elsewhere.  If that missile wasn't in my backyard -- its out of sight out of mind. Of course, this isn't entirely true as we're all affected one way or another by what happens to our fellow citizens.  Of course, we all felt the last war with Hamas (the third since we were promised  -- mistakenly --  "peace in our time" if we only left Gaza).

In the next few days, the country will feel like it is at war -- with the weather.  From extremely heavy rain along the coastal regions with gale force or higher winds, to the heavy snow in the mountains of the Galilee and Golan, to the dust storms in the south -- it will simply be unbearable for many. The solution: to stay indoors and away from danger.

Even though the storm will start in the north tonight, the strongest impulse will arrive from noon time in the north to late afternoon in the center coastal areas.  When the 500 mb trough (with vorticity maximum) arrives it will trigger rainfall rates of 60 mm per hour in some locations.  In the higher elevations of the north snow should quickly accumulate and bring (with the wind) travel to a standstill -- immediately.  Snowfall rates will continue throughout the following 24 hours at rates of 4 to 8 cm per hour in the highest areas, with total accumulations depending on elevation (i.e., melting vs snowfall).  In the Golan, expect 50 to 100 cm of snow, and 1 to 2 meters on Mount Hermon.  In the Galilee mountains, up to 50 cm or higher, with 10-25 cm of wet snow in the area of Sefad.

The headwaters of the inland rivers will quickly fill with water and present the potential for massive river rises in a very short time -- adding to flood risk from local drainage overloads.  Do not try to drive through quickly moving streams of water or across flooded roads.

Last November, the area from Ashquelon to Jerusalem was treated to between 100 and 150 mm of rain.  This time, it looks like the city will be on the southern fringes of the precipitation shield of this  storm, along the confluence of northwesterly moist winds rotating around the storm and the dry desert winds from the southwest.  Hence, Beit-El may receive 10 to 25 cm of snow while Jerusalem gets none, and Gush Etzion gets 5 to 10 cm.  It all depends on where this confluence line sets up.

Regarding temperatures in the Jerusalem center of the country: the greatest potential for snow is Wednesday afternoon into Thursday morning, with the late afternoon/evening being the most probable.  Another round of precipitation should arrive Wednesday afternoon and possibly change to snow during Thursday night into Friday morning.

Just like real wars, the war of the storm will linger for quite a while -- as the atmospheric pattern will remain unusually cold in the eastern Mediterranean for the next two weeks.

We'll be monitoring the forecast and bring along any new information about snow amounts and possible changes to the storm track.  Tomorrow morning, we'll have snow forecasts from our highest resolution model, and we'll be better able to see just how much of the rain accumulates as snow.

Barry Lynn

Weather It Is (Winter Storm Warning)

Good Afternoon:

The latest winter storm has arrived.  It has the potential to be more severe than the last one because precipitation amounts are about two to three times more than the event of January 8-10th.  However, temperatures are a bit warmer, so expect mostly wet snow accumulations (except on the Hermon) at the higher elevations.

Here are the highlights.

1) Extremely strong winds.
a) Northern Coast: 60 km/h today with higher gusts through Wednesday.
b) Central and Southern Coasts: 50 to 60 km/h today and 60 km/h winds Wednesday with higher guests.
c) Inland areas: 50 km/h with higher gusts today and Wednesday.

2) Rain Amounts.
a) Northern Coast and north: Rain begins tonight 100 to 200 mm by 00 UTC 13 February.
b) Central Coast: Rain begins Wednesday mid-day and accumulates 50 to 100 mm by 00 UTC 13 February.
c) Inland areas: areas inland of central and northern coastal areas: 100 to 200 ml by 00 UTC 13 February.

3) Expect city and flooding in Jordan Valley.

4) Snow in the north (based on our 4 km 36 to 72 hour forecast).
a) On the Hermon snow begins around mid-night and accumulates at a rate of 4 to 8 cm/h for about 24 hours (until afternoon Wednesday).
b) Golan: snow begins around mid-night and accumulates at a rate of 2 to 4 cm/h.
c) Sefad and surroundings: snow begins late night and accumulates at a rate of 1 to 4 cm/h, depending strongly on elevation.  Late Wednesday, snow may accumulate even in Sefad at about 3 or 4 cm/h.

Total snow accumulations:
i) Hermon: 1 to 2 meters.
ii) Golan 50 cm to 100 cm.
iii) Sefad: 10 to 25 cm, with higher altitude areas of 50 cm or more.

(these numbers may update as we get within range of our 1.3 km forecast).

5) Dust: Dust storms throughout the country through tonight, confined to south of the advancing front on Wednesday (to remain south of Jerusalem).

6) Lightning: expect frequent lightning with the advancing front tonight in the north, spreading to the center on Wednesday afternoon.

7) Jerusalem:

Jerusalem is forecast to be on the southern edge of this storm. For instance, Beit-El is predicted to get 10 to 25 cm of snow with 80 mm of precipitation total. Jerusalem is predicted to get 30 mm of precipitation with no snow accumulation.  Depending on the exact path of the 500 mb trough, the heavy precipitation line could change, so this will have to be watched. Otherwise, expect 5 to 10 cm of snow in the higher areas around Jerusalem, including Gush Etzion --  Wednesday Evening and night. Again, these amounts could be subject to change depending on the storm track.

Another reinforcing shot of cold air should arrive Thursday night, Friday morning, which could bring another period of wet snow.  Rain or rain/wet snow is possible on Shabbat.

8) Potential for divergent results:

Wednesday and Wednesday night:  The surface and 850 mb temperatures are marginal for snow accumulation: hence, snow accumulations will be very highly dependent on elevation.  Also, 500 mb temperatures, while quite cold, still have a 3 degree Celsius range within the GFS ensemble Wednesday night.  Colder temperatures will bring heavier precipitation and higher snow accumulations. Also, a slight shift in storm track could raise or lower snow amounts quite substantially in the Jerusalem area.

Friday morning: temperatures are again marginal for snow in many areas.  Small differences could make a big difference in snow amounts, and the GFS ensemble does show a 1 to 2 C range of temperatures at 850, 700 mb, and 500 mb.

Rain amounts and wind: Very confident.


Barry Lynn


Monday, February 9, 2015

Weather It Is (Disgruntled, and Rightfully So -- Yet...)

Good Afternoon:

Dust Storm Warning: Tuesday will see very high dust concentrations throughout the country.  Tuesday night, the high dust concentrations will be pushed southward as the cold front enters, and be confined to the areas south of Jerusalem on Wednesday.  In the areas south of the confluence zone, dust concentrations will remain very high (e.g., in Beer-Sheva, Arad, and southward).

This rest of this conversation concerns the forecast for Jerusalem.  There are no changes to forecasts elsewhere.

People are disgruntled.  At various times during the last week it appeared favourable not only for snow in the north, but for the center as well.  Then, yesterday, the highest resolution (single/deterministic) forecast indicated that the storm -- although fierce -- would only graze the Jerusalem center area.  Thus, it was necessary to  to downplay the potential for snow in the center.

Yet, the GFS ensemble shows that there is still a lot of variability in the forecast development of the 500 mb wave pattern.  Temperatures Wednesday evening on average are forecast to be near -27 C, but could be as cold as -30 C (or as warm as -22 C). In contrast, the 700 mb and 850 mb temperatures are pretty much holding within a narrow range.  Hence, the eventual details of the storm (in terms of precipitation amounts and snow elevations) depend on the evolution of the 500 mb wave pattern and are still subject to change.

Also, if you look at the forecast precipitation amounts for the center they remain quite high. Given that the GFS ensemble data is a grid size of 100 X 100 km, we don't expect the model to forecast sharp gradients in precipitation (like we wrote about earlier).  However, what this tells us is that the potential for heavier precipitation to occur in the center is still there -- it just depends on how much the storm deviates from its current forecast path -- something that can happen even a couple days in advance when the variability in the 500 mb pattern is so high.

In summary: this forecast is not yet written, or rather history is not yet written.

Friday will bring another chance for snow, but only a chance.

Barry Lynn

Weather It Is (Severe Storm Update)



Summary and Conclusions:

1a) Severe Wind Warning for central and northern coastal regions from mid afternoon Tuesday until Wednesday night.  Sustained winds of 60 to 80 km/h with higher gusts (close to 100 -- 110 km/h).

1b) Inland Wind Warning: Inland winds (Sefad, Jerusalem, Golan) will be between 40 to 60 km/h (with some higher gusts).

2) Heavy rainfall from Tel-Aviv eastward to the Hermon.

By 20 IST Wednesday Evening:

Tel Aviv, Netanya, and Haifa: 25-50 cm

Inland areas: 50-100 cm.

3a) Area of Sefad, Galilee peaks: Potential for heavy, heavy snow.  However, accumulations may be limited to be between 10 and 25 cm because of melting. Snowfall amounts will be highly elevation dependent. 

3b) The same area will have extreme rainfall, with > 100 ml. 

3c) Flooding potential in cities and in Jordan Valley Wednesday into Thursday morning.

3d) Expect lightning in convective storms along the coast and inland areas.

4) Golan and Hermon:  Expect 25 to 50 cm of snow by 20 IST Wednesday evening.

The storm will continue on Thursday with more snow on Golan and Hermon, and possible in Sefad on Friday morning.

5) Jerusalem:  Because of an atmospheric confluence zone, Jerusalem should be spared the heaviest precipitation. There is only a chance of snow Wednesday evening and Friday morning. Otherwise, rain. We'll monitor the storm for any movement further south.

Barry Lynn

Weather It Is (Winter Storm Warning for Center Cancelled)

Good Morning:

Winter Storm Warning for the Center cancelled.  Strong winds still expected.

We can now see some of the details about this storm.

If you live in the northern Mountains, including Sefad and possibly Yad Binyamin, you're in for a lot of precipitation, and quite possibly a lot of snow.  In fact, we show 10 -25 cm of snow in many locations in the north, and 50 - 100 cm in Hermon.

However, it now appears that the storm may only graze the center of the country. While heavy precipitation should arrive from the northwest late Tuesday night, and spread to the south towards Tel-Aviv during the day, the storm now looks to have a sharp cutoff between the heaviest precipitation and the lighter precipitation on its southeast flank.  This is the confluence zone between winds from the northwest and those from the southwest.

While there may be a period of snow Wednesday evening into Wednesday night in the center, temperatures will probably warm up enough towards morning to turn the snow to rain.  Rain or wet snow/rain will continue into Shabbat.

Only a turn to the south would bring the storm into areas central and south, and this is not expected at this time.

Barry Lynn

Sunday, February 8, 2015

Weather It Is (Snow Expectations: Winter Storm Warning)


Good Evening:

A Winter Storm Warning for Gush Etzion and Safed.  A Winter Storm Watch for Jerusalem.


(Here are the snow expectations for areas outside of the Golan. In the Golan, just expect more of what is written below, and on the Hermon more than a meter of snow should fall).


Folks have been asking for more specific information.  Here it is:

Becoming very windy Tuesday afternoon: In fact, the winds will likely gust enough to cause damage.  Expect heavy rain (most likely during the night) as the cold air moves in off the sea.

Temperatures will plummet towards freezing by Tuesday morning.  Expect wet snow and possibly heavy snow on Wednesday into Thursday afternoon.  In Jerusalem, expect more rain than snow, except for Wednesday evening when snow may accumulate in Jerusalem as well.

As Thursday progresses, temperatures will remain cool aloft, but moist air off the sea may cause the lower atmosphere to warm enough to change the snow to very wet snow/rain, or just rain.  

The rain or wet snow will probably continue into Shabbat.

Next week looks to be chilly -- not a good time to make holes in your outside walls.

As for accumulation amounts: accumulation is likely but I have to wait a day or two more to be more specific.  

Barry Lynn