WEATHER: Still A Chance For Snow?

March 11, 2019

Illustration: Spring Flowers and Snow by George Hodan [CC0 Public Domain]

 

Highlights: Springlike weather until Tuesday evening, then a winter-chill returns.

 

I believe that it was a week's past that I wrote last. Quite frankly, I've been busy involved in my research, but I might mention that the weather wore me out.

 

Unlike last winter, we've had numerous "chances" appearing for snow this winter. By this I mean that some fraction of the global ensemble forecasts have shown cold and wet enough weather for snow in the Jerusalem area. In fact, there was a light snow in Jerusalem, and there was a light snow and heavier (but relatively brief) snow in Gush Etzion.

 

The question is whether the chances for snow over the winter reflect just how many times it did snow. For instance, if 30% of the forecasts indicate snow over the winter, and this happens 10 times, then it should snow three times. Quite possibly, the models are what we call "over-dispersive," meaning that the chances for snow exceed actuality.

 

Alternatively, one might worry that a weather forecaster that "likes" snow might be over-dispersive him or herself. Perhaps he or she "plays-up" the chances for snow? One might just as well mention that there is a 70% chance of rain, but most folks find it more interesting to hear that there is a 30% chance of snow. One could even mention that historically it snows less often than the indicated chances, so perhaps the forecaster and the  model are both over-dispersive.

 

The good news is that the long range forecasts have been incredibly accurate, predicting 10 days in advance large changes in our weather. The "bad-news" is that some of us end up disappointed when winter rains rather than winter snows arrive on our doorstep.

 

Our latest forecasts indicate that there will be periods of warmer weather interrupted by chillier weather during this week. There is a 50/50 chance that it will become very warm or possibly revert back to chillier showers and colder weather.  During the last few days, some forecasts have even shown winter-like cold and heavier rain.

 

Right now, the warmer weather should last into Tuesday evening, but a more winter-like chill should return mid-week. This seems of high certainty.

 

And, ironically, there is a chance of snow. We'll see.

 

Jerusalem forecast (click here for updated national forecasts):

Image credit: The Jerusalem Herald

 

Dr. Lynn is a lecturer at The Hebrew University of Jerusalem, Earth Sciences Department. He is also CEO of Weather It Is, LTD, a company that specializes in reducing weather risk. Click here to read more of this writer’s work in The Jerusalem Herald.

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בס"ד

...הָרִימִי בַכֹּחַ קוֹלֵךְ מְבַשֶּׂרֶת יְרוּשָׁלִָם הָרִימִי אַל תִּירָאִי אִמְרִי לְעָרֵי יְהוּדָה הִנֵּה אֱלֹקֵיכֶם! (ישעיה  מ:ט)

...Raise your voice with strength, herald of Jerusalem; raise it, do not be afraid; say to the cities of Judah, "Here is your G-d!"

(Isaiah 40:9)

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