Storm Forecast
Valid: Fri 28 Dec 2012 06:00 to Sat 29 Dec 2012 06:00 UTC
Issued: Thu 27 Dec 2012 19:50
Forecaster: DAHL

A level 1was issued mainly for severe wind gusts and to a lesser extent for large hail and tornadoes across the Tyrrhenian Sea ... Sicily ... and the southern Ionian Sea.

SYNOPSIS

A high-amplitude upper pattern will exist over Europe on Friday, with an upper ridge axis moving from the British Isels into central Europe during the period. The trough to the west of this ridge will likewise make some eastward progress while maintaining a vast and rather intense surface low-pressure region which will start affecting western and central Europe early on Friday. The trough east oft he upper ridge will dig into the Ionian Sea where it will close off into an upper cut-off low. This development is accompanied by comparatively weak surface cyclogenesis over the central Mediterranean. This latter feature will be the focus for convective development this period.

DISCUSSION

... Tyrrhenian Sea ... Sicily ... southern Ionian Sea ...

Weak CAPE is expected to develop ahead of he Mediterranean upper trough, which should lead to gradually increasing thunderstorm activity through the period. CAPE will be seasonably weak, but DLS will increase from some 15-20 m/s to more than 25 m/s in the evning and overnight hours. This should allow storms to organize into line segments, capable of isolated marginally severe wind gusts, and possibly some hail. Given rather steep low-level lapse rates, a brief tornado or two cannot be discounted either, though the low-level shear magnitude over the sea should be rather modest.

... Greece ...

Strong orographic lift should support the development of an excessive rainfall event over Greece, starting late in the period, though the exact timing will depend on the position of the Mediterranean low-pressure system, the details of which are not entirely agreed upon by the different models. Given the orographically-dominated nature of this rain event, as well as uncertainties in the timing, will not include it in a LVL1 area at this time.