Saturday, January 30, 2016

Weather It Is (Oh, For Simplicity)

Good Evening:

Oh, I how long for the simple days of yesterday.  Then, one could track a storm moving across the southern United States.  One could also watch a mass of cold air diving south, and then wait for the not too distant development of a low pressure area along the North Carolina Coast.  With a little luck, we were in for a big snowstorm, and we always got more -- as we lived just north over the mountains beyond the New York State Thruway on the eastern side of the Hudson River.

Here, we get wind of a storm sometimes two weeks in advance, but then the storm disappears off the maps only to reappear a few days later.  Then, we finally get some assurance that it's coming, but then it arrives with a whisper and not a shovelful of snow.

Last week I drove from the Rimon neighbourhood in Efrat in a blinding snowstorm (elevation 939 m) around the corner, down the road, around the park to my home (elevation 891 m).  Where was the snow, I wondered?  The Efrat neighbourhood of Zayit Shemen -- actually the same elevation -- had a couple of inches of snow (5 cm) one morning, when we had just half an inch (1 cm).

Residents of the area describe 10 centimetres of snow at Carmei Tzur (960 m and about 10 km down the road), while others describe heavy snow in Alon Shavut, but no accumulation was seen in Efrat (other than a dusting) Wednesday evening.

Oh, how I long for the days when forecasting was simpler.

Looking ahead: we did get a glimpse for a chance of rain this coming Tuesday, and maybe a more serious storm the following week. But, now, the chances are just 10%.

For those of  you who like warm weather, Wednesday and Thursday will be quite mild.

What will follow? Let's see if the maps change again -- but it will at least turn cooler with a chance of rain showers by Shabbat and the following week.

Barry Lynn



Friday, January 29, 2016

Weather It Is (A Brief Summary)

Good Morning:

A weak trough of lower pressure will move southward along the coast today, bringing a chance of showers along the immediate coastline.

Temperatures will warm up until Monday, and the cool off on Tuesday with a 25% chance of showers.

Temperatures will then warm substantially from Wednesday through Friday.

Shabbat should start a cool down, which will be followed by a possible period of colder and stormy weather.

Shabbat Shalom,

Barry Lynn

Thursday, January 28, 2016

Weather It Is (Extreme Cold, A Recap, and A Forward Look)

Good Morning:

As shown below, it's minus two degrees celcius here in Efrat. This means any standing water has frozen on roads making for extremely hazardous driving (and walking) conditions.  The IMS map below shows that most of the country is about as cold as it gets, although there are those who will remember colder! Don't expect the temperatures to warm up quickly, as the cold is being sustained by a cold influx of air from the north.

Areas in Jerusalem should move above freezing a bit after 8 A.M.  In Gush Etzion not until around 9 A.M.

There is news in the weather world.  People are speaking about the Polar Vortex breaking down. What this means is that the mass of very cold air over the north poles is displaced elsewhere.  While some are talking about a good chunk of this air freezing the eastern US, others are speaking about part of it breaking off and freezing Europe.

The unexpected movement of this mass of cold air has possibly altered our forecast.  There is a 25% chance of rain in early February, which is still supposed to be followed by a mild spell for several days. However, the second week may be stormy, and there are some indications of a return to colder weather.

When forecasters see the onset of unusually cold weather at lower levels of the atmosphere, as well as in the middle and upper atmosphere, they think big snow-storm.  Given the initial forecasts for precipitation amounts, it seemed like a good possibility.  But then it was brought to my attention my concerned weather-buffs, that there was going to be a potential problem with the "phasing" between the northern and southern Jet streams.  Others noted the sudden lack of precipitation amounts in the forecast during the mid-week period. In the end, the second half of our storm was basically a lot of huff and puff, but without the moisture energy to sustain prolonged snowfall.  (Rain did fall heavily in bands of moisture streamers, though, especially in the south.)

True, it did snow on four days in a row, but the kind of heavy/icy snow shown in the video came only in a snow-squall on the last day (Wednesday afternoon, see below), leaving a quick 2 centimeters of ice.  It was followed by an hour of light to moderate snow, but heavy snow is needed to make for an accumulation.

True, places in the higher elevations (like Gush Etzion) saw anywhere from 5 to 10 centimeters, but I had the feeling that snow was something I could sense, and even glimpse, but never really put my hands on.  It was there, and then it was gone.

Overall, forecasters did quite well predicting the evolution of the storm, especially once it became apparent Motzei Shabbat/Sunday that something was amiss.  The exception, ironically, was right here in my backyard, where snow amounts were over-forecast at the beginning of the storm (Sunday night and Monday). Still it did snow, but like I wrote earlier: location and elevation meant whether one woke up to a winter scene or not.

We've got a month to go -- let's make the best of it.

Oh: everytime I start to think that maybe we've made some progress fighting Palestinian terrorism, they come and murder again.  I find myself thinking: don't these people have any shame?

Barry Lynn




Wednesday, January 27, 2016

Weather It Is (Cold and Snow (in Gush Etzion))

Good Afternoon:

Light rain has developed in advance of an upper level trough.  It will be followed by the coldest weather of the year by Thursday morning.

The cold will last into Friday morning.

The highest resolution model is predicting that a few centimetres of snow will accumulate in the higher elevations, most likely in Gush Etzion.  Our ensemble indicates that the probability of heavy(snow producing) precipitation is 60%.  The amount of accumulation will depend strongly on localised differences in elevation and location relative to the strongest snow showers.

Temperatures should fall below freezing in the late afternoon -- so roads may become icy.

Temperatures will moderate by Shabbat and rise steadily until mid next week.  At that point, spring might appear to have sprung as there is an 80% chance that temperatures will warm up significantly and stay that way until a storm possibly approaches two weeks from now.

Barry Lynn


Weather It Is (Dangerous, icy Conditions/Extreme Cold -- note)

Good Morning:

7 A.M update.


A brief update.

Another upper level trough will approach the area today, squeezing out light precipitation in the form of light snow in the higher elevations.

Ice on the roads! Temperatures in many areas are zero or below.  There are two factors contributing to icing of the roads. i) yesterday evening's snow/slush and rain (wet roads), and this morning's fog.  Fog will freeze into clear ice on the roads when temperatures are freezing or below.

While the upper level trough will arrive this afternoon, the most severe cold at lower levels will occur Thursday morning, with temperatures a degree or two below this morning's lows. Moreover, with clear skies in some locations, temperatures will be even lower.

Drive with caution!

Barry Lynn

Tuesday, January 26, 2016

Weather It Is (Special Weather Statement) -- update

Good Evening:

**Our highest resolution forecast model shows a period of snow this evening in Jerusalem and surrounding areas.  A rough estimate of snow is 2 to 5 cm, depending on elevation.**

Tonight's cold will be intense, with temperature most likely below zero in many hilly/mountainous areas.

Moreover, there are two large areas of precipitation shown on radar about to move into the central mountain area, including Jerusalem.

While one is hesitant to forecast snow amounts from radar, a period of snow appears likely and it will -- when combined with falling temperatures -- create dangerous travelling conditions in the Jerusalem area.

While this is not certain, a warning appears justified.

Barry Lynn

Weather It Is (Cold and Snow Warning: update)

Good Morning:

An additional note:

Radar shows a broad band of precipitation stretching from Jerusalem, Gush Etzion back to the sea coast.  Light snow is falling in Gush Etzion.

The GFS ensemble shows a possible range of outcomes for convective precipitation amounts, which is why I mentioned that snow could fall heavily enough to cause icy and snow covered conditions.  However, it might now -- keep the former in mind, though, when evaluating your travel plans.

Barry Lynn

An added note:

The latest GFS data shows that about 10 mm of total precipitation should fall in the Jerusalem area in the next six hours, followed by another 4 mm.

Since temperatures will be cold enough for snow, this would bring an accumulation of several centimetres.

Considering our past situation, scepticism is needed, but this is the only time the GFS has been consistently been predicting more significant amounts during this second half of the storm. As I wrote below, this is a convective situation and a quick burst (lasting an hour or so) could accumulate snow quickly.

Previous discussion...

Where there's cold there's snow -- something forecasters in our part of the world pretty much go by. Certainly temperatures are cold enough for snow from now until Wednesday afternoon, and they will actually get colder.

Moreover, since 1950 there were 15 periods with three days of cold in Jerusalem below 6 C, and all but two of them had at least 5 cm of snow.

In fact, intense cold should last into Thursday morning, although by Wednesday afternoon the cold aloft will be dissipating.

So, where's the snow? First, the forecast model has correctly predicted the heavier precipitation amounts from Gaza to Beer Sheva, and lighter amounts in Jerusalem.  However, it over predicted the duration and intensity in Gush Etzion.  Precipitation has been more intermittent than forecast, so snow amounts were less than forecast.

As I mentioned, this is an unusual situation.  There hasn't been a strong coupling between the southern and northern Jet Streams, meaning that we've got the northern cold without the southern moisture.  In fact, the cold were getting at lower levels is more reminiscent of very cold mornings with clear skies.

So, were overlaying periods of instability that arise because of the very cold temperatures (i.e., showers forming over the ocean) and move inland on westerly winds over a relatively dry lower layer associated with northeasterly winds in the lowest levels.

The influence of the mixture of different weather regimes on precipitation amounts has been difficult for the model to predict. (It's also the reason I felt very unsure about the forecast, even today, when it could snow more than predicted -- which is not very much.)

Such is the weather -- it's not simple nor easy to forecast.

Still, because of the cold and possible snow showers travel is not advised -- especially tonight.


Here's a picture of snow in Efrat this morning.

Barry Lynn

Monday, January 25, 2016

Weather It Is (Evening Update)

Good Evening:

Winter Storm Warning.

Periods of snow occurred today with a light accumulation in the Jerusalem/Gush Etzion area.

Radar shows a build up of precipitation west of the Jerusalem Gush Etzion north to south corridor, so snow should be beginning soon.

Cold is forecast through Friday morning, with extremely low temperatures.

Forecast snow amounts are now about 10 centimeters in Gush Etzion, with about 5 centimeters in higher  locations of Jerusalem.

However, this is an intense and focused storm with the potential to produce localised higher amounts, but also lower amounts in forecast areas.

Some of the global forecast models show precipitation occurring into Wednesday.  Once it gets cold (and it's getting cold right now), the snow will stick and cause very icy conditions.

Barry Lynn

Weather It Is (Afternoon Update)

Good Afternoon:

Winter Storm Warning for Snow and Extreme Cold

The morning WRF (high resolution model) update (from 0  UTC GFS data) suggests that the highest amounts of snow should fall in the Gush Etzion area this afternoon and night (up to 20 cm).  Amounts of 5 cm or less are predicted for the Jerusalem area, with higher amounts on mountain peaks surrounding.

The  0/6 UTC GFS is still showing a large precipitation amount with the onset of the coldest air at 500 mb early tomorrow morning into early afternoon.  However, our highest resolution model doesn't show this to the same extent.

If the overnight values verify correctly, the GFS and its ensemble shows the potential for various amounts of convective precipitation during the morning hours on Tuesday.  Somewhat colder temperatures are also seen than previously forecast.  Hence, there could be higher amounts of snow in the Jerusalem area than the WRF  (high resolution model) predicts with its last update.

The amount of precipitation on Tuesday into Wednesday night will depend upon the formation of a small low pressure system just off our coast.  The GFS ensemble is suggesting southeasterly winds, which could wrap around moisture off the Mediterranean and into the central areas.  The WRF spins this low pressure just off the central coast.  If the position is a bit more to the north, then snow amounts will be higher than forecast late Tuesday morning into Wednesday evening.

Any precipitation (even light) late Tuesday afternoon into Wednesday afternoon will cause a fluffy accumulation.  Roads will be quite icy as temperatures fall to or below freezing from late this afternoon onward (outside of Jerusalem), and at night in snow in Jerusalem.

Because of the potentially cold temperatures Tuesday and Wednesday night, slush on roads and running water on roads will freeze into ice, making for extremely hazardous conditions.

A clarification. The IMS web site suggests a prolonged period of snow in Jerusalem, but they are, apparently, only predicting light amounts overall.

The cold will last into Friday.

Barry Lynn

Weather It Is (A little bit of snow in Gush Etzion)

Good Morning:

We had some periods of snow, with temperatures at 1 C and a slushy accumulation.

The latest forecast looks more snowy than the last, with more prolonged precipitation.  An update will be given later.

Weather It Is (אזהרת חורף הסערה)

בוקר טוב
אזהרת סערת חורף לקור קיצוני ושלג / קרח אפשרי.
היו לנו דיווחים על הצטברויות  של שלג בהרים הגבוהים של גוש עציון, כוללים קריית ארבע. כמו כן , גם באפרת, זו הייתה  כמות השלג שחזינו.
הקושי  בחיזוי כמויות שלג , נוגע לטמפרטורות החזויות  עליהן  להיות בדיוק מעל ההקפאה לאורך כל היום (עכשיו, זה 1 C כאן באפרת). משמעות הדבר היא  : כי שלג חייב ליפול מהר יותר מאשר הוא נמס, וזה מאוד מקשה לאלגוריתמי  לחזות משטחי שלג . התחזית הנוכחית שלנו מראה 17 סנטימטרים בגוש עציון עד מחר בבוקר, אבל רק כמה סנטימטרים בירושלים.
עם זאת, יש גורמים  שמסבכים את חיזוי השלג  ולכן זה מאוד קשה.
ראשית, טמפרטורות ב 850 ו 700 MB ייפלו על  פי מה שמתואר היום (כ -2 C ו- C -12), שזה  נוח יותר לשלג, וטמפרטורות ייפלו על פי המתואר בלילה ב 850 MB הלילה. יותר מכך הטמפרטורות תיפול על ידי כמעט 5 C ב 500 MB, הן יגיעו  לטמפרטורות אידיאליות לשלג בגבהים גבוהים יותר, כולל ירושלים, כך זה יישאר עד כמעט יום רביעי בערב. הירידה בטמפרטורות ב 500 MB גם פותחת את הדלת לשלג הסעה עם ברק, כתחילתה של השוקת העליונה הרמה תביא סטייה באוויר והיווצרות עמוקה של עננים.
שנית, הסכום הגבוה ביותר של משקעים כמו הסעה צפוי יום שלישי בבוקר, אבל טמפרטורות עם הזרם של לחות תעלה קצת ב850 MB.
שלישית, נראה שיש בעיה עם מופע של זרמי סילון הצפוניים והדרומיים .לפיכך, למרות שזה יהיה קר מאוד מיום שלישי אחר הצהריים, ביום רביעי אחר הצהריים תתכן חוסר לחות משמעותית, ולצמצום כמויות שלג פוטנציאליים.
עם זאת, התחזיות שלנו מראות טמפרטורות בשעות  אחר הצהריים המאוחרים נופלות לסימן ההקפאה, ובמהלך פרקי שלג אולי 2-3 מעלות מתחת.
לסיכום, צבירת שלג היא הסיכוי הטוב ביותר באזור גוש עציון וסביבה גבהים גבוהים יותר סביב ירושלים, וכבישים בהחלט יהפכו  למצב קיפאון  אחר הצהריים / ערב מאוחר (עם שלג אפשרי בכבישים בפרצים כבדים שלג אחר הצהריים). שלג בסבירות הגבוהה ביותר בערב ומחר בבוקר בירושלים, אבל התחזיות שלנו לא מראים הצטברות כבדה שם.


זכור, כי הטמפרטורות תהיה קרות מאוד וכי התנאים סינופטית נקבעים לסערת שלג גדולה - נתון האזהרות שציינתי.


השירות המטאורולוגי הישראלי הוא חיובי למדי לשלג, אפילו בירושלים. לאוהבי שלג מסביב, אולי הם יהיו נכונים.


בצד שלי, אני כבר לשים על המגפיים שלי, כובע צמר אדום, ואני אפילו אתחלתי את המחשב שלי. האם זה יהיה מספיק, אני לא יודע. לפעמים, מטאורולוג הוא לא בהכרח טוב יותר ממה שאתה של מי שקורא את הטור הזה.


בארי לין

Weather It Is (Winter Storm Warning)

Good Morning:

Winter Storm Warning for Extreme Cold and Possible Snow/Ice.

We've had reports of a light accumulation of snow in the higher hills of Gush Etzion, including Kiryat Arba.  However, here in Efrat, this was the extent of our snow (picture below).

The difficulty is forecasting snow amounts pertains to the forecast temperatures being just above freezing throughout the day (right now, it is 1 C here in Efrat).  This means that snow must fall faster than it melts, and this is very hard for surface snow algorithms to predict. Our current forecast shows 17 cm in Gush Etzion by tomorrow morning, but only a couple of centimetres in Jerusalem.

However, there are complicating factors which are making this snow prediction very hard.

First, temperatures at 850 and 700 mb will fall by a degree today (to about -2 C and -12 C), which is more favourable for snow, and temperatures will fall by another degree at 850 mb tonight. More importantly temperatures will fall by almost 5 C at 500 mb, reaching ideal temperatures for snow in the higher elevations, including Jerusalem, and stay this way until almost Wednesday Evening. The decrease in temperatures at 500 mb also opens the door for convective snow with lightning, as the onset of the upper level trough will bring divergence aloft and deep formation of clouds.

Second, the highest amount of convective-like precipitation is predicted Tuesday morning, but temperatures with the influx of moisture will rise a bit at 850 mb.

Third, there seems to be an issue with phasing of the northern and southern Jet streams (at pointed out as well by in interested reader).  Hence, even though it will be intensely cold from Tuesday afternoon, in Wednesday afternoon there may be a lack of significant moisture, reducing potential snow amounts.

Yet, our forecasts show temperatures in the late afternoon falling to the freezing mark, and during snow episodes possibly a two to three degrees below.

In summary, accumulating snow is most likely in the area of Gush Etzion and surrounding higher elevations around Jerusalem, and roads will definitely become icy late afternoon/evening (with possible snow on roads in heavier snow bursts this afternoon).  Snow in most likely in Jerusalem tonight and tomorrow morning, but our forecasts don't show a heavy accumulation there.

Keep in mind, that the temperatures will be extremely cold and that the synoptic conditions are set for a major snow storm -- given the caveats I mentioned.

The Israeli Meteorological Service is quite favourable for snow, even in Jerusalem.  For snow lovers around, perhaps they'll be correct.

On my end, I've put on my boots, red wool hat, and I  even rebooted my computer.  Will it be enough, I don't know.  Sometimes, the meteorologist is not necessarily better off than you who reads this column.

Barry Lynn




Sunday, January 24, 2016

Weather It Is (Storm Update)

Good Afternoon:

Winter Storm Warning.

Heavy snow possible on Tuesday/Tuesday night for Jerusalem and surrounding areas.

The first part of our storm is proceeding as forecast.

In fact, a coating of snow is possible tonight in Jerusalem and several centimeters in higher locations surrounding the city and Gush Etzion. Light snow amounts are expected in the city of Sefad.

With regard to forecasting the second part of this event, there is a major difficulty.  While temperatures are going to turn frigid, we have the unusual situation where the lower atmosphere (850 mb) will somewhat disconnect from the 700 mb and 500 mb levels.

The 850 mb level will bring intense code from Tuesday afternoon into Thursday morning (and temperatures may not rise above freezing until Thursday night or even Friday morning). The 700 mb and 500 mb levels will bring in two periods of very cold air, Tuesday and Thursday mornings.  The cold air will bring a "kink" in the isobars, indicating the potential for strong upward motion as a "vorticity" maximum moves through.

However, because of the disconnect between the 850 mb and other levels, moisture will become more confining.  Yet, our 12 km WRF shows continuing high 700 mb humidities Tuesday night from about Sefad southward to Mitzpe Ramon.  If this verifies, then the potential for heavy snow Tuesday and Tuesday night will more likely be realised in Jerusalem and surrounding areas.

The global models do not show very much precipitation occurring after Tuesday evening.  However, they don't have the grid resolution to be able to predict small scale, but potentially very high snow producing convective clouds from Tuesday night into Wednesday afternoon.

Our high resolution model is showing more precipitation than the global models, but we are hesitant to spell out accumulation amounts until we get closer to the time of interest.  The temperatures will be cold, but without the added focus of our high resolution model were just guessing.

In the meantime, heavy rain continues with gale force winds in many locations.  Late this afternoon snow accumulates several centimetres or more in high areas around Jerusalem, including Gush Etzion. Jerusalem will see a coating of snow as well after midnight.

Barry Lynn

Saturday, January 23, 2016

Weather It Is (אזהרת חורף הסערה)

ערב טוב
סערת חורף גדולה תשפיע על האזור שלנו בימים הקרובים.
אזהרות להצפה, רוחות עזות, אבק כבד (בדרום), ושלג כבד.
חשוב לדעת :
i)  בירושלים :  צפוי שלג כבד מיום  שני  בלילה  עד ליום רביעי  בערב . סיכוי של (75%)  .
ii) גשמים כבדים   צפויים - רק בשני ימים הקרובים 50 עד 100 מ"מ ירדו  לאורך  ההרים המרכזיים, 25 עד 50 מ"מ במקומות  אחרים עם שלג בחרמון.
iii) מיום שלישי עד יום חמישי בבוקר: שוב כמויות כבדות של גשם.
iv) שלג אפשרי בגוש עציון, המקיף את הגבעות,   כמה  סנטימטרים  לפני יום שני בלילה.
v) רוחות עזות בכל רחבי הארץ.
vi) אבק בדרום.
באופן כללי מדובר על :
טמפרטורות יורדות בכל הרמות קריטיות של האוויר: 850 MB, 700 MB, 500 MB ו.
8 בבוקר יום ראשון בבוקר זה, טמפרטורות ב 500 MB תגיע לכ -25 C, C -10 ב 700 MB, ו0 C ב 850 MB. עלינו  לעצור שם, זה יהיה רק סערה רטובה אחרת - אבל זה לא הסוף יוסיף להיות יותר קר.
טמפרטורות ב 850 ו 700 MB ימשיכו לרדת במהלך היום מראש של שוקת 500 MB באופן משמעותי.
מחצות על שתי / שלישי בבוקר הטמפרטורות ב 500 MB תצנח ותביא אתה כמות משקעים משמעותית עם שלג כבד באזורים ההרריים.
יש סיכוי של 75% שטמפרטורות ב500 MB תהיה -30 C. או מתחת וזה אומר סופות שלג ורעמים ביחד . אולי התמשכות על פני זמן ארוך 36-42 שעות (מיום השנייה בלילה), ולא תסתיים עד יום רביעי בערב. הקור  יהיה ברמות נמוכות יותר, יתר על כן, יימשך זמן רב עוד יותר וטמפרטורות עשויות שלא לעלות מעל קיפאון עד יום שישי בבוקר.
ממוצאי שבת ועד יום שני בלילה (לפני הגעתו של האירוע "הגדול"), תהיה 50 עד 100 מ"מ של גשם לאורך הרי המרכז, עם אזורים רחבים 25 עד 50 מ"מ מכסה ואפילו 10 עד 25 מ"מ המשתרע לכל הדרך למטה להר רמון. משמעות הדבר הוא שפע של מים לנהר וזרימת זרם - ברמות גבוהות - אפילו לפני תחילת אירוע השלג המשמעותי.
לגבי כמויות הצטברות שלג אפשריות בהרי המרכז. יש סיכוי של 15% ששלג נמוך  יכסה מחר בבוקר את הקרקע בירושלים. אחרת, שלג רטוב ביום ראשון בבוקר מוקדם מן הנמנע שבגוש עציון ישובו ירידות של שלג במהלך היום .מוצגות במודל ברזולוציה הגבוה ביותר שלנו כדי לייצר כמה סנטימטרים של שלג. עם זאת, טמפרטורות תהיה בעיקר מעל לאפס, כך תנאים אלה לא צריכים להוות  כבישים חלקלקים מדי. יום ראשון בלילה, המודל ברזולוציה הגבוהה מציג כמויות שלג גבוהות בגוש עציון ובהרים שמצפון לירושלים. טמפרטורות ייפלו בסמוך להקפאה כך שכל  הכבישים יהיו מכוסים בשלג וקרח.
בירושלים, יש התחלה של הצטברות שלג קלה בלילה. עם זאת, טמפרטורות לא נופלות  עד לקיפאון עד יום שני בלילה מתישהו, כך לא צריכה להיות בעיה לנסוע בעיר.
בהרי הצפון, שלג גם יצטבר בכמויות מתונות, עם כמויות כבדות על החרמון והגולן. כמויות שלג קלות מוצגות בצפת.
רוחות חזקות עד יום ראשון בלילה.

אבק: לא יהיה אבק כבד באזורים הדרומיים שימשכו לתוך יום שני בבוקר.
בארי לין

Weather It Is (Winter Storm Warning)

Good Evening:

A major winter storm will impact our area over the next several days.

Warnings for flooding, gale force winds, heavy dust (south), and  heavy snow.

Already, temperatures are falling at all the critical levels of the atmosphere: 850 mb, 700 mb, and 500 mb.

About 8 A.M this Sunday morning, temperatures at 500 mb will reach about -25 C, -10 C at 700 mb, and 0 C at 850 mb.  Were we to stop there, this would just be another wet storm -- but we won't.

Temperatures at 850 and 700 mb will continue to drop during the day in advance of a more significant 500 mb trough.

From about midnight Monday/Tuesday morning the temperatures at 500 mb will plummet and herald a significant precipitation event, with heavy snow affecting mountainous areas.

There is a 75% chance that temperatures at 500 mb will be -30C or below and this means thundersnow storms, possibly extending over a period 36 to 42 hours long (from Monday night), and not ending until Wednesday evening.  The cold at lower levels, moreover, will last even longer and temperatures may not rise above freezing until Friday morning.

From Saturday night until Monday night (prior to the arrival of the "big" event), there will be 50 to 100 mm of rain along the central mountain spline, with 25 to 50 mm covering wide areas and even 10 to 25 mm extending all the way down to the Ramon crater.  This means plenty of water for river and stream flow -- at high levels -- even before the onset of the major snow event.

Regarding possible snow accumulation amounts in the central mountains. There is a 15% chance that snow will briefly cover the ground tomorrow morning in Jerusalem. Otherwise, wet snow in the early Sunday morning is quite possible in Gush Etzion where periods of snow during the day are shown on our highest resolution model to produce a few centimetres of snow.  However, temperatures will be mostly above freezing, so conditions should not become too slippery. Sunday night, the high resolution model shows higher snow amounts in Gush Etzion and mountains north of Jerusalem. Temperatures will fall close to freezing so roads could become snow covered and icy.

In Jerusalem, there is the beginning of a light snow accumulation at night.  However, temperatures don't fall close to freezing until sometime Monday night, so travel in the city should not be a problem.

In the northern mountains, snow will also accumulate moderate amounts, with heavy amounts on the Hermon and Golan.  Light snow amounts are shown in Safed.

Winds: Becoming Gale force until Sunday night.

Dust: There will be heavy dust in southern areas continuing into Monday morning.

Barry Lynn






Friday, January 22, 2016

Weather It Is (Hebrew Translation of Yesterday)


בתחזית האחרונה ביותר עדיין קיימת אי-וודאות גדולה, בעיקר בימים שני ושלישי.
אבל, קודם נטפל בהמשך היום עד יום ראשון.
אנחנו בסוף החורף עם טמפרטורות מתונות. הלילה נראה כמה משבי רוח וצינה תחל להגיע ולהתמקם  בסביבתנו.
ממטרי גשם יחלו להגיע בשישי בערב (לאורך החוף) וימשיכו לסירוגין במהלך השבת. בשבת הרוח תתגבר ותתחזק כאשר הסערה עצמה תגיע בראשון בבוקר.
שלג יצטבר באיטיות בחרמון.
אנסמבל המודלים הגלובלי עדיין מראה מספר אפשרויות לגבי כמות המשקעים, אבל הפוטנציאל עדיין רב (ותלוי בהיקף ההתקררות, בין היתר, ב500 מ"ב). אומדן כמות הגשם החזויה מהמודל בעל הרזולוציה הגבוהה שלנו, מראה שיותר מ100 מ"מ גשם יירדו בהרבה מקומות מיום שבת ועד חמישי הבא.
כרגע, הטמפרטורה החזויה למוצאי שבת ובוקר יום ראשון מעידות על כיסוי של שלג רטוב בגוש עציון, בפסגות הגבוהות סביב ירושלים ובפסגות הרי הגליל. לא כמו בסערות הקודמות, בהן הטמפרטורות החלו לעלות בבוקר, הטמפרטורה תישאר נמוכה ביום ראשון. יש סיכוי של 15% ששלג יצטבר גם בירושלים.
לאחר התחממות קלה וחולפת ב500 מ"ב מאוחר ביום ראשון, הטמפרטורות צפויות לרדת ביום שני. התחזית הממוצעת לטמפרטורות ב500 מ"ב בין ימים שני ורביעי היא בערך 27-  מעלות צלזיוס. אולם, ממוצע יכול להטעות בגלל השונות הגדולה בין המודלים השונים של אנסמבל המודלים. יש סיכוי של 30% לפרץ של שלג כבד במהלך ימים אלו אם הטמפרטורה תגיע ל-30 מעלות צלזיוס.
בהסתמך על המידע האחרון, אני מעריך שיש סיכוי רב לשלג רטוב בירושלים והפסגות סביבה, אבל רק 30% שהוא יצטבר. בגוש עציון ואזורים גבוהים דומים, הסיכוי למחזורי שלג והצטברות מגיע כבר ל50%.
למרות שהסיכוי לארוע שלג רציני בירושלים הוא נמוך, הפוטנציאל קיים בהסתמך על הטמפרטורות הקרות החזויות בחלק ממודלי האנסמבל ושפע המשקעים החזוי.
אנחנו יודעים יותר מאשר ידענו לפני מספר ימים, אבל נקווה לתחזית ברורה יותר מחר (וכמובן שבמצואי השבת).
ברי לין

Weather It Is (Winter Weather Warning; Winter Storm Watch)

Good Afternoon:


"Ya can talk, ya can talk, ya can bicker, ya can talk, ya can bicker, bicker, bicker, ya can talk, ya can talk...,"

"The piper pays him! Yes sir, yes sir, yes sir, yes sir.."

"But he doesn't know the territory!"
We're only a day or so away from our first major winter storm -- and it may go down in the record books as a major snowstorm as well.

Because its Shabbat Eve, I won't belabour the point, but I can say that there has been a lot of talk, disagreement (bickering), and more talk, and we're all hoping to get "paid" in the end with a "good forecast."  And yet, even after all that is is hard to know the "territory."

 This is shaping up to be a tough, tough call, and when the going gets tough I fall back to the high resolution model -- but it extends only out to Sunday afternoon.  Still, the global ensemble (GEFS)  and longer rain GFS are showing copious amounts of moisture (rain) and a deepening winter chill coinciding with the heaviest rain.

Here's what we know.

Through Sunday afternoon:

Rain amounts: generally 25 to 50 mm, with higher amounts in the far north and possibly along the Askelon Jerusalem corridor. 

Winds: winds rising on Shabbat to Gale force by Sunday afternoon before decreasing into Monday.

Snow: Snow on the Hermon Shabbat and Sunday, and in the northern mountains, (mixed rain/snow) Jerusalem, and Gush Etzion late Saturday night into Sunday morning. There is a 20% of accumulating snow in Jerusalem, while a coating of snow is predicted in higher areas surrounding it.  The high resolution model is predicting around 5 cm in the Gush Etzion area. 

Dust: Heavy dust south of Beer Sheva, especially late Shabbat through Sunday.

Extended forecast:

Temperatures at 850 and 700 mb will remain around -1.5 and -11.5 throughout Sunday into Monday, but temperatures at 500 mb will rise to to around -23 C.  From Monday afternoon until Wednesday afternoon the mean temperatures at 500 mb will fall progressively to close to -29 C.  

While the mean 850 mb temperatures don't change much, there is a 60/40 chance that they will also cool progressively below the mean. At the same time, there is a 25% chance that there will be even greater cooling at 500 mb than the mean temperatures.  

Interestingly, the 700 mb level temperatures do not show much variability, and the simplest explanation is that a massive moisture flux will produce heavy wet snow from Monday afternoon until Wednesday Evening, with the cold near the surface lasting into Thursday and possibly Friday.

So, here's where we leave it for Monday into Thursday:

Expect gusty winds, heavy, heavy rain (in the coastal plain, Kinneret basin (> 100 mm, possibly 200 mm)), and wet snow in the northern mountains (of course on the Hermon and Golan), and higher areas surrounding Jerusalem, and Gush Etzion.  Expect flooding rains in the Jordanian and Dead Sea Valleys.

However, there is the opportunity for an historic, heavy, wet snow that bring all traffic and travel to a standstill for several days.

More, God willing, after Shabbat.

Shabbat Shalom,

Barry 

Thursday, January 21, 2016

Weather It Is (New Development)

Good Evening:

The latest global ensemble forecast is leans more strongly towards a snowy weather event.

Hopefully, tomorrow's blog will confirm this.

Barry Lynn

Weather It Is (עברית תרגום)

ערב טוב,
לכם או לחבריכם יש אולי ספקות אבל לא אליכם אני מתכוון. אני מתכוון לספקות של מודלי חיזוי מזג האוויר.
היו הרבה תחזיות מושלגות בעברנו, ובעברנו אני מתכוון רק אתמול בלילה או אפילו הבוקר.
בתחזית מושלגת, אפיק חזק המגיע לאזורינו מוקדם ביום ראשון מביא עמו גשם רב וצניחה תלולה בטמפרטורות – כאשר גשם יכול בקלות להשתנות לשלג. אחרי הפוגה קלה, אוויר קר במיוחד זורם דרומה שוב ומקרר אותנו אפילו יותר – כל הדרך עד יום רביעי. זוהי תחזית מושלגת מאוד.
בתחזית הלא מושלגת: אפיק חזק מגיע לאזורינו ביום ראשון אבל הוא לא לגמרי ממשיך עד הסוף. הטמפרטורות הקרות ברמת לחץ 500 מ”ב מגיעות לפני האוויר הקר בשכבות האטמוספירה התחתונות ואח”כ עוזבות מוקדם מדי. לאחר מכן, לפני שהסופה השנייה מגיעה, האוויר הקר ממשיך יותר מדי מזרחה. התוצאה במקרה זה: קצת שלג רטוב, אולי, ואז מספר ימים רטובים וקרים בלבד – ללא שלג (מלבד בחרמון).
אם מישהו יסתכל רק במודלים העיקריים: ה GFS, EURO, GEM וכ'ו, הוא יראה סופת שלגים באופק בחלק ממודלים אלו, בחלק ממחזור החיזוי שלהם ואפילו יותר מפעם אחת ואז ללא שלג כלל.
בדומה, אם מישהו יסתכל על אנסמבל של חיזויים – כמו של אתמול בלילה – הוא יראה כמה ימים של מזג האוויר קפוא ( 80% סיכוי). אולם, האנסמבל הבא אחריו מציע תחילתה של סופה (עם אפשרות לשלג), ואז 50% סיכוי לסופה נוספת.
אם זה גורם לכם להרגיש יותר טוב, בעיה זו מטרידה גם את החזאים המנסים לחזות את הסופה הבאה בחוף המזרחי של ארה”ב (רק עוד שלושה ימים). הם עדיין לא יודעים אם תהיה סערה או רק שלג רטוב בניו יורק, גשם בלונג איילנד ואבק בפרברים הקרים.
מה שאומר שפשוט יש יותר מדי משתנים לא ידועים על מנת לומר משהו על מזג האוויר של השבוע הבא.
יש יותר מדי אינטרקציות שמתרחשות באזורים שאין עליהם מספיק מידע כדי להבין את מאפייני הזרימה (כנראה שיש בעיה בלחזות גם אותם). אם אני צריך למצע את תחזיות האנסמבלים ותחזיות המודלים היחידנים, הייתי אומר שיש סיכוי של35% לשלג בירושלים, ןסיכוי של 50% לשלג בגוש עציון ובגליל העליון.
האם השלג ייחל כבר בראשון בבוקר?
הישארו קשובים.
ברי לין.
      1. הרבה ספק אך קצת בהירות

ערב טוב,
לכם או לחבריכם יש אולי ספקות אבל לא אליכם אני מתכוון. אני מתכוון לספקות של מודלי חיזוי מזג האוויר.
היו הרבה תחזיות מושלגות בעברנו, ובעברנו אני מתכוון רק אתמול בלילה או אפילו הבוקר.

בתחזית מושלגת, אפיק חזק המגיע לאזורינו מוקדם ביום ראשון מביא עמו גשם רב וצניחה תלולה בטמפרטורות – כאשר גשם יכול בקלות להשתנות לשלג. אחרי הפוגה קלה, אוויר קר במיוחד זורם דרומה שוב ומקרר אותנו אפילו יותר – כל הדרך עד יום רביעי. זוהי תחזית מושלגת מאוד.
בתחזית הלא מושלגת: אפיק חזק מגיע לאזורינו ביום ראשון אבל הוא לא לגמרי ממשיך עד הסוף. הטמפרטורות הקרות ברמת לחץ 500 מ”ב מגיעות לפני האוויר הקר בשכבות האטמוספירה התחתונות ואח”כ עוזבות מוקדם מדי. לאחר מכן, לפני שהסופה השנייה מגיעה, האוויר הקר ממשיך יותר מדי מזרחה. התוצאה במקרה זה: קצת שלג רטוב, אולי, ואז מספר ימים רטובים וקרים בלבד – ללא שלג (מלבד בחרמון).
אם מישהו יסתכל רק במודלים העיקריים: ה GFS, EURO, GEM וכ'ו, הוא יראה סופת שלגים באופק בחלק ממודלים אלו, בחלק ממחזור החיזוי שלהם ואפילו יותר מפעם אחת ואז ללא שלג כלל.
בדומה, אם מישהו יסתכל על אנסמבל של חיזויים – כמו של אתמול בלילה – הוא יראה כמה ימים של מזג האוויר קפוא ( 80% סיכוי). אולם, האנסמבל הבא אחריו מציע תחילתה של סופה (עם אפשרות לשלג), ואז 50% סיכוי לסופה נוספת.
אם זה גורם לכם להרגיש יותר טוב, בעיה זו מטרידה גם את החזאים המנסים לחזות את הסופה הבאה בחוף המזרחי של ארה”ב (רק עוד שלושה ימים). הם עדיין לא יודעים אם תהיה סערה או רק שלג רטוב בניו יורק, גשם בלונג איילנד ואבק בפרברים הקרים.
מה שאומר שפשוט יש יותר מדי משתנים לא ידועים על מנת לומר משהו על מזג האוויר של השבוע הבא.
יש יותר מדי אינטרקציות שמתרחשות באזורים שאין עליהם מספיק מידע כדי להבין את מאפייני הזרימה (כנראה שיש בעיה בלחזות גם אותם). אם אני צריך למצע את תחזיות האנסמבלים ותחזיות המודלים היחידנים, הייתי אומר שיש סיכוי של35% לשלג בירושלים, ןסיכוי של 50% לשלג בגוש עציון ובגליל העליון.


האם השלג ייחל כבר בראשון בבוקר?
הישארו קשובים.

ברי לין.


Weather It Is (Winter Storm Watch)

Good Afternoon:

The latest forecasts still show a lot of uncertainty, especially from Monday into Thursday.

But, first let's deal with the rest of the day through Sunday.

We're at the end of our mild winter temperatures.  Tonight will see some gusty winds and chill begin to settle in over our country and surroundings.

Rain showers should arrive Friday evening (along the sea coast) and continue off and on through Shabbat.  On Shabbat, winds will increase in intensity and they will reach gale force Sunday morning.
Snow will accumulate lightly on the Hermon.

The Global Ensemble still shows a range of possible rainfall amounts, but the potential is quite large (and will depend on the extent of cooling -- in part -- at 500 mb).  Extrapolating to forecast amounts from our high resolution models suggests that greater than 100 mm will fall in many locations from Shabbat into possibly next Thursday.

Right now, forecast temperatures for late Saturday night and Sunday morning could produce a coating of wet snow in Gush Etzion and the higher peaks surrounding Jerusalem and the mountain peaks of the Galilee. Unlike the previous storm when temperatures will warm by morning, temperatures may not warm during the day Sunday. There is a 15% chance that it will snow and accumulate in Jerusalem too.

After a brief warm-up at 500 mb late Sunday, temperatures should fall into Monday.  The average forecast 500 mb temperatures for Monday into Wednesday are about -27C.  However, averages are a bit deceiving because of the large variability among ensemble members.  There is a 30% chance for burst of heavy snow during the period as temperatures may fall as low as -30 C.

Based on the latest data, I would estimate that there is a high probability of wet snow in Jerusalem and surrounding Jerusalem peaks, but only a 30% chance that it will accumulate.  In Gush Etzion and other similarly high areas, the probability of periods of snow are very high and accumulation at 50%.

Although the chances are low for a heavy snow event in Jerusalem: the potential exists given the cold temperatures displayed on some of the ensemble members and the copious amounts of precipitation.

We know more than we did a few days ago, but we're hoping for even greater clarity tomorrow (and certainly Motzei Shabbat).

Barry Lynn

Wednesday, January 20, 2016

Weather It Is (A Lot Of Confusion And Some Clarity)

Good Evening:

You might be confused, or your friends might be confused, but it's not you or them I am speaking about.  I am speaking about the forecast models.

There have been some very snowy forecasts in our past -- and by past I mean just last night, or even this morning.

In the snowy forecast, a strong trough arrives early Sunday bring heavy rain and rapidly cooling temperatures -- and rain changes quickly to snow. After a slight let up, extremely cold air streams southward again and we chill down even more -- all the way until Wednesday.  This is a very snowy forecast.

In the non-snowy forecast: a strong trough arrives early Sunday, but it doesn't quite get going. The 500 mb really cold temperatures arrive before the cold air in the lower atmosphere, and then exits too soon. Then, before the second storm arrives the main area of cold air swings too far east.  The result: some wet snow, maybe, and then several days of just wet, cold, and nasty weather -- but no snow (except on the Hermon).

If one looks at just the main models, for example: the GFS, EURO, GEM, etc, one will see a snowstorm on the near horizon in some of these models, in some part of their forecast cycle, and even more than once in a row, and then no-snow at all.

Likewise, if one looks at the ensemble forecasts -- like the one late night -- one sees several days of frigid cold weather (80% chance).  However, the next ensemble run suggests an initial storm (possibly snow), and then a 50% chance of additional snowstorm.

If it makes you feel any better, there is a similar problem facing the forecasters who are forecasting the next storm on the east coast (just three days away).  The still don't know if there will be a blizzard or just some wet snow in NYC, rain on Long Island, and dusting in the cooler suburbs.

What this means is that there simply are still too many unknowns to really say much about next week's weather.  There are simply too many interactions happening in areas where there isn't enough data to properly resolve these circulation features (there may also be problems predicting them as well). If one were to average the ensembles and average the individual models, I'd put the probability at about 35% for snow in Jerusalem, and 50% in Gush Etzion and the upper Galilee.

Will it snow as early as Sunday morning?  Stay tuned.

Barry Lynn

Tuesday, January 19, 2016

Weather It Is (A Lot Of Talk)

Good Afternoon:

People say it smells like snow.  People say that all the models show it will snow.  People are saying a lot.

While it is true that the global ensemble forecast (GEFS) shows that temperatures will be below 0 for four days next week, and that temperatures at 700 mb will be below -11 C (with possibly as low as - 14 C), the 500 mb forecast temperatures show only a 15% chance of heavy snow. On the other hand, this looks like to be a very wet system, much wetter than the present storm.

Speaking of the present storm, we're looking for rain to move southward this afternoon into the Jerusalem area and spread south to Beer-Sheva.  Total rainfall amounts will be between 25 to 50 mm in the north (north of Lake Kinneret), 10 - 25 mm southward to Jerusalem, and 5 to 10 mm south (again) to Beer-Sheva.  Snow of 10 to 25 cm on the Hermon.

If one is wondering where did the previously heavier forecast rains go, one might answer that they were passed into next week's storm.

As mentioned, everyone is talking but those who say "yes" it will snow and snow a lot are not really paying attention to probabilities, nor to the fact that snow amounts are very sensitive to elevation in the central areas.

Certainly, there is much to be excited about: next week will be very wet, cold, and a severe gale is a good possibility (with "Storm" force gusts).  Otherwise, let's wait a bit on predicting accumulating snow.

Barry Lynn

Monday, January 18, 2016

Weather It Is (Stormy, Chilly, -- A Break -- Then Winter Storm)

Good Afternoon:

The dust has settled over us and there is nothing but do but wait for the coming rains to wash it away.

The rain is expected to arrive tonight in the northwest (with snow on the Hermon), enter Tel-Aviv in the early morning, pass through Jerusalem around noon,  and then make its way southward to Beer-Sheva by mid to late afternoon.

Off and on rain should continue in the center area until Wednesday noon.

Total amounts should be generally 10 to 25 mm,  with 25 to 50 mm east of Tel-Aviv and in the Golan. Snow amounts on the Golan are suppose to be around 30 cm.

Very strong, gale-force winds expected into Tuesday afternoon.

Looking ahead: the cold air remains in place until Thursday morning.  Temperatures will then warm up until the end of Shabbat when a very strong winter storm should arrive from the northwest.

Right now, it appears that Sunday through Wednesday offers the possibility of an extended period of snow.  Still, while we see greater model convergence at 850 (75%) and 700 mb (about 50%), we're still waiting for the 500 mb forecast to come better into focus.

In summary, rather unpleasant dusty and then rainy weather in the immediate future (with gale-force winds), chilly, a break, and then a winter storm loops quite possibly (but not certainly) on next week's horizon.

If you've got any pyjamas with penguins, polar bears, or even snowflakes, now is a good time to lend some encouragement.

Barry Lynn


Sunday, January 17, 2016

Weather It Is (Heavy Rain, Cold, Gale Winds, Dust, and Snow on the Hermon:)

Good Afternoon

The music plays and the Beatles sing: "Come together right now over me."  Yet, it seems like the Rolling Stones: "I can't get no satisfaction" seems to rule the day.

We've been watching a stormy situation develop for quite a while.  We mentioned the word snow as a possibility for quite a while now, but here's what we see (and there's no snow in our very immediate future).

Cold:  Today is the last of the warm days for quite a while.  Then, the temperatures will drop through Monday into Tuesday.  Cold temperatures will then crawl through the week into Thursday.  Temperatures will be near freezing in the central areas, and below freezing up north on the Golan/Hermon, where snow will fall.

Heavy Rain:  50 to 100 mm of rain are expected by mid-day Tuesday in the north and coastal areas.  There will be 25 to 50 mm of rain in the Kinneret basin.  Rain will proceed slowly north to south beginning Monday night and reaching the central mountains around noon on Tuesday, with 10 to 25 mm.  More rain is expected Tuesday afternoon into Wednesday.

Gale Force Winds:  Winds will begin to shriek Monday evening and reach peak values most likely Tuesday Morning.  They will remain gusty and quite strong into Tuesday night. Higher gusts will also occur.

Snow: Heavy snow on the Hermon (50 to 100 cm) with lighter amounts in surrounding areas of the Golan.

Dust: Heavy dust will develop tomorrow, especially in the coastal areas. The clean-air/dust line will then move slowly southward over Monday night and be south of Jerusalem on Tuesday afternoon.  High dust levels will remain through the afternoon in the southern regions.

The cold air, rain, wind, snow, and dust is courtesy of a strong trough of low pressure centered north of Turkey with an extension into the eastern Mediterranean. The storm is approaching from the west, which is why the air mass associated with it is most likely to be too warm for any snow in the higher elevations of the Galilee and central mountains.

However, the mass of frigid air is expected to remain fairly stationary over the next 10 days or so while higher pressure pushes slowly eastward into western Europe.

Small wave perturbations will rotate southeastward along the interface.  The global ensemble (GEFS) is predicting a 25% chance that one of these will position itself far enough eastward (coupling) within the trough to finally push temperatures below freezing anywhere from late week into next week.

For snow to fall and "stick" in the Jerusalem area we need extremely cold temperatures aloft (close to -30 C; 500 mb), very cold temperatures in the middle atmosphere (-12 C; 700 mb), and a few degrees below freezing temperatures at 850 mb (just 1500 m above sea-level).  We need all of these factors to come together simultaneously.

Some of us hope that we'll eventually come together as a nation ("The People of Israel).  Others, will be happy if just our weather can cooperate.

Regardless, may we all be blessed to find "satisfaction."

Barry Lynn




Saturday, January 16, 2016

Weather It Is (Glasses Anyone?)

A note: Dust levels will increase tonight and tomorrow and possibly become very heavy on Monday into Tuesday morning, especially in western areas.


Good Evening and Shavua Tov,

Donning a superior pair of multifocal lenses, we can now see ahead until next Thursday -- and snow is not in the forecast.

The initial surge of cold air will arrive fairly far to our west and the storm will weaken as it moves eastward. Still, we expect quite chilly temperatures to arrive Monday evening and bottom out Tuesday morning.  Temperatures at 850 mb will actually be close to freezing, but relatively warm air above this layer will preclude any snow from falling in the central and Galilee mountains. With the cold air will arrive rain, perhaps heavy rain, with heavy snow on the Hermon.

The inclement weather will last into Thursday, and then the forecast is blurred by many different possibilities, including even colder winter air or just normal winter chill.

There is a 15% chance of snow from Thursday onward  (in accordance with the latest "Euro" forecast) while there is a 40% chance of rain from Thursday to the end of the following week.

So, winter continues, but the ingredients have not yet come together to produce heavy snow in the central mountains, including Jerusalem. 

My apologies. 

Barry

Thursday, January 14, 2016

Weather It Is (What We Know)

Good Evening:

A bit of winter chill is upon us, and light rain has dotted the landscape.

The chill will last until about noon tomorrow, when temperatures will climb until Sunday evening.

They will plummet on Monday to close to freezing. Rain is possible Monday night and more likely on Tuesday.

Beyond this time, there has been unusually large variance in the model forecasts, from model time to model time, from model to model, and within ensemble members.

If a strong ridge (rather massive high) builds over western and central Europe, our snow chances increase.  If not, just rain.

That's it in a nutshell,

Shabbat Shalom,

Barry Lynn

Wednesday, January 13, 2016

Weather It Is (Potential For Heavy Rain (Snow))

Good Evening:


The latest long term weather forecast from the National Weather Service (Uptown, NY) reads (for Thursday through Tuesday): "Models are in good agreement with the overall H5 Patte RN across North America through the period... with timing and amplitude differences starting to become apparent this weekend..."

In other words, they are admitting that they really don't know what's going to happen just a few days from now, although they are willing to guess -- despite all the advanced technology at their disposal.


If you take a look at our 850 mb temperature forecast for the next few days you'll see a rollercoaster ride as a cold front begins its passage tonight with a chance of light rain showers on Thursday afternoon/night.

We'll then ascend to relatively milder temperatures on Shabbat and Sunday, and then crash down on Monday to close to freezing.


The following few days could be very rainy.  We're also getting indications from the 500 mb temperature graph  (now about 30%) that there could be heavy snow. The problem is that the previous global ensemble forecast did not show what the latest (0600 GMT) now shows, and given the uncertainty in the weather upstream (over the eastern US), it is hard to know whether the next forecast ensemble will be reassuring or not.

So, that's where we leave it -- with a
touch of optimism tinged by the reality that we're in a very unusual weather pattern that can't decide just how unusual it wants to be.

Barry Lynn

Tuesday, January 12, 2016

Weather It Is (It's In The Cards Or Not!)

Good Evening:

The weather will warm up to mild levels before a dry cold front air arrives Thursday and Friday.  The temperatures will then warm right back up (and then some) until Sunday afternoon -- before winter makes its return.

One might argue that it's in the cards, or a bit of luck -- however our weather turns out. Right now, we see the potential for a very wet storm next week -- covering a good part of the country.  We see a 40% chance that temperatures will approach freezing, and about a 30% chance that temperatures will be cold enough for snow in the middle atmosphere.  However, we're not seeing real cold temperatures at 500 mb, just yet -- or rather there is a 10% chance that temperatures will be cold enough to cause convective (heavy) snow.

Predicting the  weather is not like predicting the orbits of the planets.  Their orbits can be described by a set of equations with solutions that can be calculated.  The weather, on the other hand, is described by a set of non-linear equations that have no exact solution.  Moreover, we never know the exact initial conditions of the atmosphere (it's state now), so we must approximate that too.  This is the reason that we use ensemble forecasts (multiple forecasts) so we can see just how strong the "signal" we're trying to predict is -- when most of the ensemble members cluster around a particular forecast event we have greater confidence in their outcome.

Right now, we have very low confidence.

For those who resist the idea that all is random chance, or that life is more than a deck of cards...

It might interest some to know that one of our prayers speaks about both the orbits of the planets and  predicting the weather (thank you to an interested person for this tidbit), and contrasts them.

For instance, Psalm 148: "Praise, sun and moon; praise him, all bright stars.  Praise him. the most Exalted of the heavens. and the waters that are above the heavens.  Let them praise the name of Hashem, for he commanded and they were created. And he established them forever and ever, he issued a decree that will not change.

Contrast this with: Praise Hashem from the earth....  Fire and hail, snow and vapour, stormy wind, fulfilling his word.

Enough said.

Barry Lynn

Monday, January 11, 2016

Weather It Is (The Clock Ticks)

Good Evening:


The good thing about uncertainty is that just about anything is possible. For instance, as a storm develops near Greece on Saturday it will move quickly across the Mediterranean. As high pressure develops to its northwest, it will help direct frigid winter air into the storm's circulation.

Should we freeze the fishes, we're less likely to freeze our raindrops.  B y "we," I mean the processes of mother nature, and not us who feel like we're following an unfolding drama. If the cold air is injected further eastward, we'll have a better chance for snow.

In any case, from Monday onwards next week looks to be periodically quite wet.

The combination of a strong negative Arctic Oscillation coupled with a strongly negative North Atlantic Oscillation coupled with a very active El-Nino is playing havoc with our forecast models.  What this means is that the processes that might possibly indicate long range changes in our weather are being very poorly sampled (as the first two indices in this list indicate strong perturbations in the arctic circulation).

For instance, earlier today the GFS showed a massive area of cold air over the eastern United States speeding eastward and bumping our developing storm further eastward than previous forecast (good for us). Six hours later the impact of the same massive cold was not nearly as dramatically forecast.

The result is that single (deterministic) forecast runs change both the intensity, the direction from which it arrives, and the position of next weeks storm, while the ensembles refuse to reach a consensus.

As you probably know: timing and delivery is pretty much everything in show business and this drama won't be better sketched out until some of the energy (cold-air) moves into a better location (where planes fly, balloons are launch, and there enough people to note its passing).

Barry Lynn