Storm Forecast
Valid: Thu 26 Nov 2009 06:00 to Fri 27 Nov 2009 06:00 UTC
Issued: Wed 25 Nov 2009 19:16
Forecaster: GATZEN

SYNOPSIS

A broad long-wave trough is present over north-western Europe. A mid-lvel jet extends along its periphery from the Bay of Biscay to western Russia. At low levels, a cold front is expected to enter the west Mediterranean Sea during the period. While low-level shallow cold air advection will lead to mostly stable lapse rates in the range of the cold front, deeper instability is forecast underneath the broad trough over north-western Europe. Stable conditions are indicated over most of south-eastern Europe in the range of high pressure.

DISCUSSION

North-western Europe

Convectively mixed polar air masses are present in the range of the long-wave trough. While the low-levels may evolve inversions over the land, some low-level buoyancy is likely across the rather warm sea surface. Showers are forecast that will affect a braod region including portions of the coasts. Best potential of deep moist convection is forecast in the range of a trough axis that moves eastward over The Channel region late in the period. Rather strong QG forcing is likely to the north of a mid-level jet streak, and latest model output indicates low-level warm air advection ahead of the trough axis that may result in decreasing low-level buoyancy. The formation of clouds with embedded convection is expected that may be accompagnied by thunder. Although the low-level vertical wind shear is about 10 m/s in the lowest kilometre, severe wind gusts or tonadoes seem to be unlikely at this time given rather weak low-level buoyancy and low-level veering profiles.