Storm Forecast
Valid: Thu 27 Nov 2014 06:00 to Fri 28 Nov 2014 06:00 UTC
Issued: Thu 27 Nov 2014 05:15
Forecaster: GATZEN

A level 1 was issued for southern France and north-western Italy mainly for excessive precipitation.

A level 1 was issued for southern Spain and north-western Morocco mainly for excessive precipitation.

SYNOPSIS / DISCUSSION

A long-wave trough extends across eastern Europe, where dry air masses limit the chance of any convective storm. The upstream ridge across western Europe is associated with warmer and moist low-level air masses. This moist air overlaps with steep lapse rates across parts of the Mediterranean and west of Iberia due to the warm sea surface and relatively cold mid-level air, leading to CAPE. Main focus is a mid-level short-wave trough moving across Italy in the morning hours, leading to ongoing storms that spread into the Adriatic and Greece area.

From the west, convective activity can temporarily weaken due to weak mid-level ridging. However, the approaching short-wave trough from the Iberian Peninsula will be associated with steepening lapse rates from the west again, leading to increasing convective activity spreading from the Iberian area across the west Mediterranean in the afternoon.

Storms are forecast to become better organized as vertical wind shear is increasing gradually east of the approaching trough. Back-building storms may develop initially over the Iberian area, later especially across the north Mediterranean region where excessive precipitation may occur. Additionally, the low-level southerly jet ahead of the trough leads to strong low-level vertical wind shear of more than 10 m/s near the coasts. This can support mesocyclones capable of producing tornadoes. The overall threat is limited and spreads from the Morocco/Iberia area towards the north Mediterranean.