mercredi 24 septembre 2014

European Storm Forecast Experiment

Storm Forecast
Storm Forecast
Valid: Wed 24 Sep 2014 06:00 to Thu 25 Sep 2014 06:00 UTC
Issued: Wed 24 Sep 2014 06:23
Forecaster: PUCIK
A level 2 was issued for extreme E Tunisia and SW Sicily mainly for very large hail, severe wind gusts and excessive precipitation.

A level 1 was issued for much of the western Mediterranean, SE Spain, Sardegna, SW Italy mainly for large hail, severe wind gusts and excessive precipitation.


A complex synoptic-scale setup evolved over Europe. When looking at the satellite loops, one immediately notices unseasonably deep low pressure system over extreme Eastern Ukraine. With pressure reading of 979 hPa and intense gradient, it is very likely that just south of the core, wind gusts have exceeded 30 m/s. To the west, situation looks more calm. Still, a pronounced trough filled with cold mid-tropospheric airmass is making its way from UK towards BENELUX and Germany. Its base is stretching all the way towards Iberia, slowly progressing eastwards and weakening.

As of 05 UTC, abundant DMC activity is already observed over the western half of the Mediterranean. This will also be the region of most interest regarding severe DMC for today.


... SE Spain through Balearic, Tyrrhenian Sea, N. Africa ...

00 UTC soundings from Dar-El-Beida and Trappani reveal presence of EML, while towards the north, lapse rates are not as pronounced (e.g. Mallorca or Decimonnanu soundings). It is likely that with an approach of the trough, lapse rates will be advected a bit more to the north than is the current situation. Combined with moist airmass over the sea surface, moderate CAPE values are simulated, with values on the order of 1000 - 2000 J/kg. Degree of wind shear will increase towards the south, where stronger southwesterly flow is observed. Generally speaking, DLS values should easily reach over 15 m/s over much of an area, so that supercells and well-organised multicells will be possible, capable of large hail and severe wind gusts.

CI will be at first tied to the lingerning, ill-defined frontal boundary, but will spread southwards towards the night hours. Models simulate possiblity of one or two MCS formation. The most likely location will be between Tunisia and Sicily after Thursday 00 UTC, where explosive environment is simulated, featuring CAPE above 2000 J/kg, along with more than 25 m/s of DLS. In case that storms attain supercellular characteristic, besides the MCS form, very large hail will be likely. With MCS, excessive precipitation and damaging wind gusts may be expected as the primary threats. 

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