Storm Forecast
Valid: Fri 22 Apr 2011 06:00 to Sat 23 Apr 2011 06:00 UTC
Issued: Thu 21 Apr 2011 19:01
Forecaster: TUSCHY

A level 1 was issued for N-Algeria mainly for severe wind gusts and large hail.

SYNOPSIS

Blocking pattern persists over Europe with broad high pressure area in place. An upper trough is placed over far W-Europe and a wave train of depressions affects far N-Europe.

DISCUSSION

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Weak pressure/geopotential height gradients cover most parts of Europe which approve quite widespread development mainly along mountainous areas and atop regionally maximized PBL moisture pools. Mid-tropospheric temperatures at or below -20 °C allow mid-level lapse rates to remain steep enough for some low-end CAPE (100 to 500 J/kg MLCAPE). Main inhibiting factor for more robust CAPE fields will be limited moisture content within lower troposphere, which fosters diurnal PBL mixing. Thunderstorm coverage will be maximized over Spain and N-Algeria, whereas thunderstorms over W-central Europe will be very isolated/short-lived.

Shear remains weak at best, so pulsating thunderstorms with strong wind gusts and marginal hail will be the main risk. Thunderstorms gradually decay after sunset.

A level 1 was introduced over N-Algeria, where DLS of 20 m/s assists in organized thunderstorms with large hail/severe wind gusts all day long.

Persistent influx of moist air from the W-Mediterranean along the leading edge of a quasi-stationary upper low over Spain assists in an heavy rainfall risk over NE-Spain mainly during the first part of the forecast period. However, no level will be issued due to limited thunderstorm activity despite local rainfall amounts, matching our level 1 criterion