De atmosfeer staat op ontploffen #241 - Buien in aantocht

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Op zaterdag 24 mei 2008 18:50 schreef MissHobje het volgende:
Wtf dinsdag staat er 24/28 en woensdag 22/27 wow wel iets van 50 a 60% kans regen en zon 50 a 30% !

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Op zaterdag 24 mei 2008 17:41 schreef ItaloDancer het volgende:
GFS heeft tot eind vd week nog neerslagkansen, EC is wat slechter... hopelijk komt het gewoon in de vorm van sneeuw

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Op zondag 25 mei 2008 08:31 schreef appelsientje het volgende:
Brrr het is meteen een stuk kouder... *rilt*

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Op zondag 25 mei 2008 16:18 schreef i2Them2 het volgende:
Toch wat leuke buitjes in het zuiden.

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Op zondag 25 mei 2008 16:39 schreef OA het volgende:
7 uur zon, 0 mm regen, 20 graden.... Ja, gaat goed met die voorspelling...

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Op zondag 25 mei 2008 17:23 schreef i2Them2 het volgende:

[..]

0 uur zon, 2 mm regen, 14 graden... Ja, gaat goed met die voorspelling...

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Op zondag 25 mei 2008 17:38 schreef ItaloDancer het volgende:
Als je het raam open hebt staan tenminste, wat ik dus heb.

Tevens quattro.

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Op zondag 25 mei 2008 16:18 schreef i2Them2 het volgende:
Toch wat leuke buitjes in het zuiden.

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Op zondag 25 mei 2008 18:07 schreef IkWilbert het volgende:
Hier wat gemiezer in het oosten des landes.

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Op zondag 25 mei 2008 19:58 schreef aloa het volgende:
Het ziet er wel heftig uit voor woensdag.

wetterzentrale

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Op zondag 25 mei 2008 19:58 schreef aloa het volgende:
Het ziet er wel heftig uit voor woensdag.

wetterzentrale

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Op zondag 25 mei 2008 22:09 schreef aloa het volgende:

[..]

bekijk deze dan even:

woensdag 09.00
woensdag 12.00

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Op zondag 25 mei 2008 22:46 schreef ItaloDancer het volgende:
+2 uur.

En cape /= onweer.

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Extended Forecast
Valid: Tue 27 May 2008 06:00 to Wed 28 May 2008 06:00 UTC
Issued: Sun 25 May 2008 20:25
Forecaster: GROENEMEIJER
SYNOPSIS

East of the large-scale trough over the Bay of Biscay and Iberia a shortwave trough moves northward from the western Mediterranean Sea to central France. This shortwave is embedded in a strong southerly jet with speeds of 30-35 m/s at 500 hPa. A surface low is projected to move from near the Balearic Islands to Brittany.

DISCUSSION

Level 1 and 2 areas...

Widespread convective precipitation is expected over NE Spain and SE France in an area of upward vertical motion ahead of the aforementioned low pressure centre. Those embedded storms will probably be elevated, but steep lapse rates and strong low-level winds could still produce isolated severe hail and strong to severe gusts.

A warm front is expected to stretch from the Pyrenees to the Benelux countries. On its warm side dry air is advected northwestward out of the Alpine region into France. The evolution of the preciptation and cloudiness across southern France is hard to forecast, but per GFS this should shift northwestward to western France in concert with the frontal zone. This may leave an area in its wake where the sun has opportunity to heat the boundary layer. This could potentially create some surface-based instability in a region with large low level hodographs (300 m2/s2 SRH) and create a threat of strong tornadoes. In case low-level instability remains too limited for surface-based tornadic storms, they will still be likely to produce rather widespread severe gusts, given the already strong 25 m/s wind speeds at 850 hPa. Possibly, enough forcing will be available for a well-defined squall-line to move northward more or less across the area indicated as level 2.

An open question is to what extent storms will form further north along the warm front across NW france and the Benelux countries. It is not unthinkable that, during the late afternoon and evening, some storms develop there also. Given the high storm-relative helicity that is forecast, these may develop into supercells with a threat of hail, damaging gusts and tornadoes as well. Currently, our best estimate is that surface-based storms will mostly be restricted to central and W-central France until early evening, but that NW France the Benelux and possibly SE England will be affected by organized storms overnight.

Low storm coverage is forecast across NE France, Germany, Switzerland and NW Italy. But, as more than 1000 J/kg CAPE, steep mid-level lapse rates and moderate deep-layer shear are expected, storms could easily produce large hail and strong downdrafts, so that a level 1 appears to be warranted for this area also.

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Op maandag 26 mei 2008 15:24 schreef IkWilbert het volgende:
estofex.org heeft een update voor vandaag.

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DISCUSSION

Belgium, Netherlands, NW Germany, N-central France

The extent of cloudiness associated with a partly stratifrom/partly convective rain zone associated with a diffuse cold front extending in N/S direction across France has been much less than anticpated. Widespread clearings have formed to the north of this area across Belgium, N France and NE France south of a west-east oriented warm front across Belgium.

Visible satellite imagery shows towering cumulus developing across Belgium and the French région Nord. There and later elsewhere, isolated storms are expected to form. Up to 1000 J/kg of CAPE would be available to those storms, that develop in an environment of rather strong deep-layer wind shear of 20-30 m/s and high storm-relative helicity. As a result, they may develop into supercells capable of producing some large hail, and strong winds. Tornadoes are not ruled out either. A preferred location may be the warm front across Belgium that extends into the German Rhineland.