Storm Forecast
Valid: Thu 03 Dec 2009 06:00 to Fri 04 Dec 2009 06:00 UTC
Issued: Wed 02 Dec 2009 19:44
Forecaster: GATZEN

A level 1 has been issued for the Aegean mainly for waterspouts.

SYNOPSIS

Rather low geopotential is present over Europe and the polar jet stretches from the western British Isles to the Iberian Peninsula and further across the southern Mediterranean. Rather stable conditions are forecast across most of the continent due to cold and dry low-level air masses.

DISCUSSION

Western Europe

Strong mid-level jet streaks will affect western Europe in the wake of two short-wave troughs propagating south-eastwards, while cold air advection of rather dry low-level air is expected to limit instability sufficiently to suppress deep moist convection over most places. Best potential seems to exist across the Bay of Biscay, where some instability may be present in the range of the trough axis in the morning hours given rather moist low-level air masses and moist-neutral lapse rates, but increasing mid-level warm air advection in the wake of the trough axis will likely lead to stabilization during the day.

West Mediterranean Sea

Ahead of the southern short-wave trough, a tongue of rather moist low-level air mass spreads north-eastward across the west Mediterranean Sea. Underneath the axis of the approaching short-wave trough, mid-level air is expected to cool, while the low-level air mass will stay rather warm and moist due to the warm sea surface. Limiting factor will be the increasing advection of dry and cool air masses that may suppress convection in the wake of the low-level cold front. A few storms may develop, though. Given the weak vertical wind shear in the lower levels of the troposphere, storm organization is not likely and severe convection is not expected.

Aegean, southern Turkey

In the range of the center of a cut-off low over the Aegean steep lapse rates are forecast. Given the warm sea surface and moisture pooling in the range of low-level convergence lines, mostly uncapped CAPE in the order of 300 J/kg seems to be likely in the morning hours over the Aegean Sea. Together with weak vertical wind shear, showers and thunderstorms may be capable of producing waterspouts. While the trough moves north-eastward, the chance of waterspouts is expected to decrease gradually while the threat spreads into southern Turkey.