Storm Forecast
Valid: Wed 31 Mar 2010 06:00 to Thu 01 Apr 2010 06:00 UTC
Issued: Tue 30 Mar 2010 23:46
Forecaster: PUCIK

SYNOPSIS

The main feature will be a large cyclonic vortex centered over the Northern Sea/Scotland and will only slightly change its position during the course of the forecast period. At its southern flank, a westerly jet-stream will cover most of the Mediterranean. Associated with the surface low and an attendant trough, a wavy frontal system will progress across Central and Southeastern Europe. To the northeast a ridge will stretch over Russia with stable conditions in this region. Large fields of banded showers or very weak thunderstorms are expected in the western quadrant of the low, over the Atlantic.

DISCUSSION

...Southern France to Northern Italy ...

Moderate to strong deep layer shear is forecast over these regions, while they are placed on the borderline of the mid and upper level jet. Models predict only meager instability development with CAPE values reaching up to several hundreds J/kg, partly due to the low moisture presence. Moreover, good synoptic scale forcing seems to be missing altogether with even Q-vector divergence and downward motion predicted for both of these regions at noon to afternoon hours (apart from the eastern half of Northern Italy). It seems that scattered showers or thunderstorms might form in this post-frontal situation, but only very few of them might be able to become well organised and produce severe weather. Therefore, no Level is introduced albeit an update might become necessary later on.

...Serbia, Western Bulgaria and Romania...

Ahead of the surface trough and the frontal system, a slight destabilisation is forecast across this region as mid and upper-levels cool with values of MLCAPE probably staying around 500 J/kg with local enhancements possible. Slight to moderate wind shear is forecast with values mostly up to 15 m/s in 0-6 km(increasing to the south), suggesting that mostly multicellular convection will occur. First of the detrimental factors is the lack of large scale forcing or a strong focused mesoscale lift apart from the frontal system itself that should reach the area by late afternoon/evening. Initiation is questionable as for example WRF produces only very little convective precipitation before 15 UTC, while GFS and ECMWF are more optimistic. Moreover, low moisture content will also limit the intensity of the storms. At the moment it seems that mostly sub-severe hail or wind gusts might occur with storms, but coverage of severe will be probably too little to match a Level 1. An update might be issued during the day if conditions prove to be more favorable.