Storm Forecast
Valid: Fri 28 Mar 2008 06:00 to Sat 29 Mar 2008 06:00 UTC
Issued: Thu 27 Mar 2008 18:11
Forecaster: TUSCHY

SYNOPSIS

Flow becomes more zonal over the N-Atlantic, remaining more disturbed over Europe. A weakening upper-level trough lines out over SE Europe while ridging over central Europe progresses notheastwards. Airmass, affecting most parts of Europe is cold and stable and therefore improper for convective activity.
Main focus for enhanced convection arises over NW Europe due to a NE-ward racing trough axis and under the upper-level low over SE Europe.

DISCUSSION

... Ionian Sea, Aegean Sea, parts of the Adriatic Sea and Crete...

Atmosphere becomes unstable as cool and well mixed airmass overspreads the 15-16°C warm Mediterranean ( SSTs west and south of Greece ) and numerous thunderstorms will evolve. Shear stays weak and despite slim LL CAPE release there is a risk of an isolated waterspout as numerous convergence zones cross the area.

At the moment we believe that a cluster of thunderstorms will develop north of Crete during the early morning hours, progressing constantly towards the east / northeast as a persistent and well defined 15-20m/s LLJ points northwards into the area of interest. This cluster of showers / thunderstorms should undergo weakening during the evening hours as surface depression slides southwards.
Weak thermal ridging in this area should limit instability release at lowest levels but very low LCLs and 0-1km helicity signals partially at or above 150m^2/s^2 are present and overlap so there is the risk of an isolated funnel / tornado/ waterspout report over southeastern Greece and the central Aegean Sea. Forecast soundings from eastern Greece reveal that the early evening time-frame will be the best time for deep convection although run-to-run consistency for this event is not that high.

There exists a risk for flash flooding if convective precipitation extends well inland over eastern Greece and western Turkey.

...Ireland and United Kingdom...

A cold front crosses the area from the west during the morning and midday hours. There are indications that some low-end elevated instability could be released during the cold front passage but very slim values should preclude any large hail risks. Well mixed postfrontal airmass is characterized by meager LL moisture content and rapidly cooling mid-levels. The possibility for deep convection and hence the chance for an isolated thunderstorm arises along the west-coast of UK during the afternoon hours where LL moisture is the best but shear/ instability signals are too weak for an organized thunderstorm risk. No highlighted area was issued due to expected very isolated thunderstorm coverage.