Storm Forecast
Valid: Sun 29 Mar 2015 06:00 to Mon 30 Mar 2015 06:00 UTC
Issued: Sun 29 Mar 2015 00:14
Forecaster: TASZAREK

A level 1 was issued for British Isles, Benelux, N France, SW Germany mainly for the severe wind gusts of convective origin and in lesser extent for tornadoes

A level 1 was issued for W and S coast of Turkey for waterspouts

SYNOPSIS

Weather in Europe will be mainly driven by the low over Iceland and two highs over Russia and Azores. Extensive cold high over E Europe will provide dry weather over most of the N and E Europe inhibiting convection. Developed in warm air mass Azores High will also inhibit convective activity in most of the SW Europe. The best conditions for the thunderstorms are expected over E Mediterranean and Turkey where the top of the long-wave and weakening cutoff will provide favorable conditions for convection in low sheared environment. Within deep low over NW Europe shortwave trough will push cold and relatively dry air masses of polar origin into W Europe and the thunderstorms in the highly sheared environment are plausible. The main Jet streak will extend in the forecast period from N Atlantic to Benelux.

DISCUSSION

... British Isles, Benelux, N France, SW Germany ...

Within the shortwave trough the advection of cold air of polar origin and thus the cold front is expected to pass trough Ireland, S Great Britain, Benelux, N France and SW Germany. CAPE is forecast to be marginal (100-200 J/kg) but it will occur in the highly sheared environment. Although free convective layer will be shallow, both very high 0-6 (40-50 m/s) and 0-3km (20-25 m/s) vertical wind shear indicate that convection may organize into linear feature and create risk for the severe wind gusts of convective origin. Significant mid and low level air flow according to NWP data may provide convective gusts up to 25-30 m/s, if convection will be involved, it is possible that these gusts may be even stronger. Increased LLS exceeding 15 m/s, 0-1km SRH ~ 150 m2/s2 overlapping with marginal instability and favorable QG-forcing create also risk for the significant tornado occurrence. Certainty to the lightning activity is decreased mainly due to relatively warm cloud tops, shallow free convective layer and low thermodynamic instability. Therefore only 15% probability for the lightning is issued. The highest threat for the severe weather occurrence and linearly organized storms will fall on British Isles between 0900 and 1500Z

... N and S coast of Turkey ...

The environment of marginal vertical wind shear, increased low level lapse rate, weak air flow in low and mid levels, rich boundary-layer moisture, instability up to 400-600 J/kg and favorable QG-forcing on the right side of the cutoff will provide good conditions for waterspouts, especially over S Turkish coast. The highest threat for their occurrence is expected from the morning hours up to late afternoon.