Storm Forecast
Valid: Wed 24 Mar 2010 06:00 to Thu 25 Mar 2010 06:00 UTC
Issued: Tue 23 Mar 2010 22:18
Forecaster: PUCIK

SYNOPSIS

One of the main features influencing the weather will be a ridge, building over Central Europe and stretching to Scandinavia, moving slowly to east. To the south of the ridge, a shallow pool of low geopotentials will be centered over the Southeast Mediterranean. An active and developing depression will reach Iberia by Thursday morning, forming in the nose of the mid and upper level jet-streak. At the surface a high pressure system will setlle over Eastern Europe while Western Europe will be under a large system of lows. A deepening low will influence the weather over Southwestern Europe from Wednesday evening on.

DISCUSSION

...Southern and Central Spain...

A low end instability built up is forecast by GFS model during the day time heating with MLCAPE values simulated at approximately 500 J/kg, but the depth of unstable layer should stay rather shallow. ECMWF is even less optimistic with only spotty areas of CAPE above 100 J/kg. Vertical wind profile should be favorable for a well organised convection with wind shear over 15 or 20 m/s in the lowest 0-3 to 0-6 km. Convection will be initiated by a surface convergence, but at the moment it does not seem that any strong synoptic factor will compensate for the small degree of instability. Regarding the simulation of convective precipitation, GFS is the most optimistic also in this characteristic while WRF does produce only isolated spots of precip. A small chance exists, that few storms might in favorable shear become strong multicells or supercells and produce large hail or severe wind gusts. Due to the uncertainities regarding thunderstorm coverage and the extent of the CAPE, no level is issued at the moment, though an update might become necessary.

...Portugal, Northwestern Spain...

An active weather pattern with a sharp short wave trough and a left exit region of mid-level jet-streak providing a favorable forcing will prevail over the area during Wednesday night and Thursday morning. An indirect circulation associated with the jet-streak will lead to the development of a low level jet ahead of the cold front. Very favorable conditions regarding the forcing and wind shear will not materialize however into well organised deep moist convection, due to the non-existent instability. Models predict only a stratiform rain shield with convection starting behind the cold front in neutral forcing. More favorable conditions for severe convection in this region might start just after Thursday 06 UTC and will be covered in the next storm forecast.