Wednesday, February 4, 2015

Weather It Is (Greater Proportion)

Good Morning:

Location, location is everything, and so it is with the weather.

In our case, I mean the location of the area of higher heights (often in conjunction with higher pressure) and the relative location of lower heights (low pressure).  The area of higher heights is referred to as a ridge, while the area of lower heights is referred to as a trough (see map below). Alternatively, think of the area of the ridge as a "mound" of relatively warm air, while the area of the trough is a "valley" of colder air.

The height (map below) of the 850 mb level above sea level is a measure of the temperature of the atmosphere.  The lower heights are associated with colder air (blues and purples, while the higher heights (greens, yellows, etc) are associated with warmer air.  The air flows counter clockwise around the trough and clockwise around the ridge.  The position of these two systems in the map below facilitates the flow of Siberian air southward into our region.  In terms of the potential snow amounts, the more time the cold air over the sea, the more the sea warms the lower air mass, and the less potential for snow.  (From

The previous forecast from the GFS model had the storm moving in further from the west, and hence warmer surface temperatures, and less potential for snow.  The ensemble was also somewhat less optimistic about the potential for snow -- although I mentioned in my last blog that this is a complex weather situation that still needs to be resolved by the forecast model ensemble.

This morning, we are again more optimistic about potential for snow amounts anywhere from Tuesday into Shabbat.  Both the deterministic (GFS) and its ensemble shows a somewhat more eastward track to the storm system (less time over the sea).

Even though we must wait possibly a few days more to more confidently forecast next week's storm,
Here is what we know:

1) The storm will be a very wet one, with potential two to three times more total precipitation amounts than our last big (January storm).  The chance of rain is 100%. The total amount of precipitation will be similar to the amounts received in last December's big snow storm.

2) There is a 20% chance of extremely high winds --  mostly likely on Tuesday February 10th.

3) There is a 35% chance of snow sometime during these four days.

4) There is still a 20% chance of extremely high snow amounts in the higher elevations of the center and Galilee, as well as the Golan.

5) The Hermon will probably have more than 1 meter of snow.

How much snow will fall elsewhere? It depends on just what proportion of precipitation falls as snow (and can accumulate).  In the center during our last storm, this was about 10 to 20% of the total amounts. It is still far to early to be more definitive, and far too early for our high resolution forecast model to give a more exact idea of just how much precipitation will fall as snow.  So, the potential is there, but we cannot say anything more definitive than this.

Barry Lynn

No comments:

Post a Comment

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