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Storms in Poltava (Jul.13)

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Author Topic: Storms in Poltava (Jul.13)  (Read 76 times)
Roman White
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Poltava, Ukraine

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« on: July 13, 2009, 12:59:02 pm »

Today the weather is absolutely the same as on Jul.09 - it was cloudy with some breaks before noon, and during the early afternoon a strong gust front moved from south across Poltava. Circa 15 minutes ago I had noticed a very nasty-looking cloud in S...

(I'm sorry for excessively cropped photo - it was hard to stay in front of the open window in the weather like that...)

...very soon I observed cloud patches in zenith moving with a crazy speed... strong gusts had reached my house, breaking some trees and shaking the roof a bit. Currently there is powerful thunderstorm still in action with intense downpour and there possibly some hail occured for a moment.

ESTOFEX had forecasted 'level 1' alert for today:

A level 1 was issued for the Smolensk-Moscow Upland, the Central Russian Upland, the central Ukraine, parts of the Black Sea and north-central Turkey mainly for excessive rainfall, large hail and severe winds.

Monday at 0600 UTC... the mid/upper-level flow across Europe features a longwave trough stretching from southern Sweden across Belarus and the Balkwan States to western Turkey. As a shortwave over northern Poland moves northeastward, a cyclone over eastern Latvia is expected to deepen as it moves northward into Finland.
The southern end of the longwave trough should gradually evolve into a cut-off low over the Black sea. Upstream... a ridge over southern Europe moves slowly eastward. A strong southwesterly jet is present between this ridge and an a trough centered near 20 W. In the lower troposphere warm air is advected northward across the western Mediterranean, E France, and the Alps.


Central Russia upland, Eastern Belarus, Ukraine, Black Sea...

A still weakening short-wave trough with NE-wards moving cold front will continue to produce severe weather over these areas. Storms should initiate in the early afternoon hours along the trailing cold front. There, deep-layer shear near 20 m/s should overlap with moderate instability near 1000 J/kg, so that storms should be able organize into multicells and a few discrete supercells. Given the almost parallel flow relative to the shear vector, early clustering is expected and few linear MCS clusters will likely form.

Across the north-central Ukraine, locally enhanced helicity of 200-300 m2/s2 is expected to develop per GFS. This will enhance the threat of low-level rotation in storms. A few tornadoes may thus occur in this area. But the main threat is mostly large hail ealy in the afternoon, when storms are still more isolated. Later, clustering of the storms suggest that locally excessive rainfalls with flash floods may occur given the slow moving storms and high PWAT values. Additionally, some isolated damaging winds will be possible. The storm activity will diminish during the late evening and overnight.

Ukrainian meteocentre:
During the day of Jul.13 thunderstorms, possibly with hail and gusts 15-22 m/s will occure all over Ukraine; in N, central, S regions and Crimea excessive rainfall in possible.
« Last Edit: July 14, 2009, 09:48:47 am by Roman White » Report Spam   Logged

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