Storm Forecast
Valid: Sat 17 Nov 2007 06:00 to Sun 18 Nov 2007 06:00 UTC
Issued: Fri 16 Nov 2007 20:45
Forecaster: DAHL

SYNOPSIS

Feature of main interest this period will be the slowly eastward progressing upper low over the central Mediterranean. This feature is being accompanied by a moderately strong surface low, with an attendant cold front stretching from the NW Ionian Sea southwestward at the beginning of the period. As the front moves eastward, a peripheral upper vort max is simulated to overspread the front, resulting in renewed cyclogenesis along it over the N Aegean Sea late Saturday night. Plume of steep mid-level lapse rates will persist in the pre-frontal environment, along with locally 10 g/kg ML moisture. This could maintain peak MLCAPEs on the order of 1500 J/kg ahead of and along the front. In its wake, deep polar air is overspreading the relatively warm sea waters, resulting in simulated low-level lapse rates in excess of 30K/km.

DISCUSSION

... Ionian Sea ... Greece ... Aegean Sea ... extreme W Turkey ...

Focus for potentially severe convective
evolution exists along and ahead of the cold front overspreading the Ionian Sea, Greece, and the Aegean Sea until early Sunday. DLS should be well in excess of 20 m/s, with LLS locally greater than 10 m/s per latest GFS run. Given this kinematic setup and anticipated strong thermodynamic fields, a substantial threat for severe thunderstorms should exist. Strongest evolution should occur in the evening hours when DCVA-related lift overspreads the region. Expect evolution of one or more large MCSs with imbedded mesocyclones. Severe wind gusts, large hail and tornadoes could occur with this system, with the threat persisting well into the night.

... Tyrrhenian Sea ... Ionian Sea ...

Some threat for severe weather also exists in the post-frontal air mass in association with comparatively shallow convection. It seems that steepest lapse rates (30K/km over the N Mediterranean) will not be topped by deep instability, but 20 K/km LL lapse rates should still be present where sufficiently deep convection occurs. This suggests that some waterspout threat exists, assuming the presence of misovortices that will be encountered by the convective clouds. Steepest lapse rates are simulated over the N Tyrrhenian Sea early Sunday morning with up to 30 K/km.