Storm Forecast
Valid: Thu 04 Feb 2010 06:00 to Fri 05 Feb 2010 06:00 UTC
Issued: Wed 03 Feb 2010 21:43
Forecaster: GATZEN

SYNOPSIS

The northern and eastern portions of Europe are covered by low geopotential that yields a north-westerly mid-level flow from the North Sea to the east Mediterranean. A dry boundary-layer is present to the east of this jet as well as over the Balkans and Central Europe, where a ridge amplifies during the period. Further west, a trough enters the Bay of Biscay, and a very strong mid-level jet expands into the Iberian Peninsula and western Mediterranean during the period.

DISCUSSION

Iberia and Bay of Biscay

Latest models indicate a subtropical low pressure system moving across south-eastern Spain ahead of the approaching jet streak and the associated short-wave trough. Consequently, a stable boundary-layer is predicted over Iberia due to low-level northerly winds below the very moist subtropical air, and rather intense stratiform precipitation may occur before the system weakens rapidly over the west Mediterranean. In the wake of the trough, the strong mid-level jet streak will lead to upward vertical motion across the Bay o Biscay region, where a rather deep polar air mass will spread eastward. Low-level moisture will be limited as westerly winds are expected to advect rather dry air into the Bay of Biscay, and best potential for thunderstorms seem to exist over the southern and western portions of the Bay of Biscay region. Weak vertical wind shear will be not supportive for organized convection over most places, but some thunderstorms may organize along the southern and western portions where the vertical wind shear in the lowest 6 km will become stronger. Along the cold front that will cross the Bay of Biscay ahead of the trough, at least shallow instability may develop given the moist low-level air mass and steepening lapse rates. A narrow line with embedded convection may develop along the cold front, while thunderstorms are not forecast due to the warm equilibrium level.