samedi 12 avril 2014

European Storm Forecast Experiment

Storm Forecast
Storm Forecast
Valid: Sun 13 Apr 2014 06:00 to Mon 14 Apr 2014 06:00 UTC
Issued: Sun 13 Apr 2014 01:08
Forecaster: VAN DER VELDE
A level 1 was issued for southern Denmark and northern Germany for a chance of severe wind gusts and tornadoes.


High pressure builds over the Iberian Peninsula while a broad trough is in place over southeastern Europe. Shortwave troughs move over Italy, Greece, western Black Sea area and Ukraine. Slight CAPE (<200 J/kg) allows some thunderstorms mainly over Italy and eastern Bulgaria in the afternoon. In Bulgaria deep layer shear is strong but will not be likely to lead to stable updrafts with the poor instability.
After 00Z a shortwave trough with a strong dynamic tropopause lowering digs into the Denmark/Germany area with strong vertical motions where slight CAPE will be present due to strong lapse rates. The cold front structure is well developed at mid levels and not at low levels, with significant differential low-level theta-w advection indicative of strong linear destabilization. A linear storm system is likely to form, the strong wind field will allow convective gusts over 20 m/s and the 0-1 km shear of 15-20 m/s allows tornadoes and bow echoes with severe gusts. A clear left jet exit with a gradient of 0-6 km shear vectors from 15-35 m/s highlights a potentially widespread risk of severe gusts. A non-supportive factor is the apparent lack of surface-based parcels at night in the GFS model and deep layer shear may be offset in the north south direction from CAPE.
The unusually high shear, a solid MUCAPE and forcing would potentially need a level 2 for widespread gusts and an isolated tornado but some uncertainty about CAPE and the estimate of 20-25 m/s convective gust strength suggest a level 1 may be sufficient.

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