Sunday, December 18, 2016

Weather It Is (Stormy Weather, Snow?)

Good Morning:


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

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

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

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

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

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

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

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

Shavua Tov,

Barry Lynn

No comments:

Post a Comment

Note: Only a member of this blog may post a comment.