Storm Forecast
Valid: Wed 19 May 2010 06:00 to Thu 20 May 2010 06:00 UTC
Issued: Wed 19 May 2010 04:06
Forecaster: ESTOFEX

SYNOPSIS

At midlevels of troposphere, the most prominent feature will be a large cut off low with two separate centers covering most of Southern and Eastern Europe. One of the centers will be placed over Ukraine, with very little movement during the day. Another one will rapidly rotate around the base of the large-scale trough, embedded in a jet-streak, in the extents of the Western and Central Mediterranean. Strong synoptic scale forcing is simulated with this feature. To the west a ridge will strech from western Iberia to Scandinavia.

At the surface a large, but shallow surface low will encompass most of the Eastern, Central Europe and the Central Mediterranean. A high pressure system will form over Western Europe. Most of Europe will be under cool maritime polar airmass with prevailing northerly to northeasterly flow.

DISCUSSION

... Baltic states...

Models are quite consistent in developing a bullseye of instability over this region with MLCAPE values possibly exceeding 1000 J/kg during the diurnal heating. Storms will likely form along the local convergence zones with no concentrated lift from synoptic scale feature. With storms forming with very little vertical wind shear, they will be very probably of pulse nature with chaotic multicellular clusters possible as well. Despite the lack of organisation and weak lapse rates, very slim chances will exist for the strongest cells to produce marginally severe hail. With slow movement of the cells, some areas might receive high amounts of rainfall albeit not expected to reach the severe criteria.

...Corsica, Sardegna, Southern half of Italy, Sicily, Ionian Sea

As the aforementioned cut-off low rotates around the base of the trough, strong jet-streak is expected to encircle its southern flank with windspeeds up to 35 m/s at 500 hPa level. Strong forcing, as suggested by IPV values and Q-vectors convergence will be observed due to the strong DCVA and high values of PV. At the moment it looks that only marginal instability will build over the region with MLCAPEs in order of hundreds of J/kg. Moreover, the highest amounts of CAPE will probably not overlap with the enhanced wind shear values (up to 25 m/s in 0-6 km layer) in most of the regions except for Eastern Siciliy and the Ionian Sea. In this region, thunderstorm initiation might be an issue, as suggested by GFS, NMM and WRF models, which are breaking out only sporadic spots of precipitation. Even though slight chance exists that a well organised storm would produce marginally severe hail in this area, due to the questions regarding the storm initiation, no Level is introduced attm.