Storm Forecast
Valid: Mon 23 Feb 2009 06:00 to Tue 24 Feb 2009 06:00 UTC
Issued: Sun 22 Feb 2009 15:32
Forecaster: TUSCHY

SYNOPSIS and DISCUSSION

The blocking strength index remains augmented over the far eastern Atlantic at least for the following days and for sure for the next 24 hours. Hence there are no major changes compared to the past few days regarding the pressure constellation over Europe. A stout high pressure area persists over the far eastern Atlantic with strong CAA downstream of this feature. The airmass, which is available, remains dry and chilly with no existing severe weather risk.

Where those short-lived/weak thunderstorms finally evolve is somehow tough to determine as most parameters remain just marginal supportive for thunderstorms. There is a broad swath, running from Slovenia and the N-Adriatic Sea to the Tyrrhenian Sea all the way down to Malta and then eastwards to the Aegean Sea where at least sporadic lightning could occur.

I) Aegean Sea and Crete

Already during the morning hours, a cold front approaches Crete from the west and a few thunderstorms will likely evolve. Gusty winds and marginal hail are possible with DLS in the order of 10-15m/s and low-end instability. Another round of storms is possible during the evening and early night hours, as a weak back-bent occlusion draws near from the north. Again, marginal hail and strong wind gusts are possible.

A very low-end waterspout risk exists over the SW-Aegean Sea, where background flow is weak and some LL instability is forecast. The risk diminishes after sunset.

II) Malta NW-wards

A moisture gradient sets-up during the day and a weak/elongated surface depression slowly consolidates during the evening and night hours SW of Sicily. EL temperatures are very warm, so despite a constant increase in shower activity, thunderstorms look less likely . Conditions just become more supportive during the morning hours (Tuesday), as EL temperature drop down to -10°C so we went ahead and issued a general thunderstorm area for that time frame.

III) N-Tyrrhenian Sea, N-Adriatic Sea and Slovenia/Croatia

Surface cold front gets blocked by the rough terrain over E-Austria unlike mid-level CAA, so low-end instability release indeed looks reasonable over Slovenia/Croatia as some LL moisture is still present. EL temperatures are not impressive, but at least cold enough for shallow/isolated deep convection. A few daytime driven thunderstorms are possible with marginal hail and strong wind gusts. A very isolated thunderstorm event is also possible east of Corsica after 18Z.