• Dr. Barry Lynn

Israel’s ‘Mild’ Storm Compared to US ‘Bomb Cyclone’

Satellite Image Credit: Courtesy NASA Earth Observatory

After last week’s storm, temperatures should moderate until Wednesday evening. Winds will switch from a northerly to southerly direction, and the relatively humidity should drop. However, a cold front should arrive Wednesday night, and it will usher in cooler and moister air. This initial push of cool air should bring a chance of showers Wednesday night. At the moment, a more substantial rain should arrive motzei Shabbat. This will be the result of a storm moving along the southern coast of the Mediterranean and then by Cyprus. However, this storm may pass to far north, which would lead to generally lower rain amounts that the past storm. Last week's storm was a severe one, complete with heavy rain, gale force winds, hail, lightning and thunder, as well as high waves. Trees fell down, roads were flooded, and there were quite a number of lightning strikes, some that knocked out power (there were actually about 2500 strikes, about 300 more lightning strikes in this storm than is average for the month of January). Some of you may have noticed that there was dust before the arrival of the rain. The presence of dust often increases the intensity of rain in a humid environment. High dust concentration leads to the formation of small drops, which ascend above the freezing level. These drops can then freeze (releasing heat as they do so). The increase in heat leads to stronger updrafts, and the mixing of water and ice, which produces hail as well as thunder and lightning. There was also the news of the storm along the east coast of the United States. It underwent what is termed "explosive cyclogenesis," where the central pressure fell 24 mb in 24 hour or less. The central pressure in our storm here in Israel fell about 8 mb in 16 hours, or about 1/2 mb per hour. So, even though the effects of our storm were severe, the intensity change was only about half of the storm that affected the east coast (especially the mid-Atlantic states). The reason for this is that our storm developed near Cyprus, and then moved eastward over land. When it moved over land, it lost its supply of moisture. In contrast, the US east coast storm stayed over water as it developed, allowing for continued flow of moisture into its circulation, and continued development. Stay tuned for more news on our upcoming storm!

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.

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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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