Storm Forecast
Valid: Sun 11 Nov 2007 11:00 to Mon 12 Nov 2007 06:00 UTC
Issued: Sun 11 Nov 2007 10:46
Forecaster: DAHL

SYNOPSIS

An intense upper longwave trough over central Europe will remain the dominant feature this period ... which will be slightly deformed by perturbations orbiting about its periphery. A frontal wave associated with one such perturbation is now present over N Germany ... and in its wake, deep polar air is advected southwards. Ahead of this feature, some warm advection is expected to take place over the Adriatic-Sea region, which could result in weak instability over this region late in the period.

DISCUSSION

... North Sea ... N Germany ...

It seems that isolated lightning may occur along with comparatively shallow polar-air convection that advects from the North Sea into N Germany. Band of rather strong shear magnitude should surround the region of deepest convective mixing -- rather than being collocated with it -- and given limited low-level mesoscale forcing for ascent, the storms should in general remain weakly organized. However, strong background gradient flow could locally be augmented by downward momentum transfer. Also, strong low-level shear suggests that a brief funnel/tornado or two may occur, but severe threat is too low for a categorical outlook.

... Adriatic and Ionian Sea ...

Isolated, quite shallow, thunderstorms could develop over the Adriatic and Ionian Sea late in the period as a result of low-level wam advection and increasing large-scale ascent. Depth of the cells is expected to be shallower than 500 hPa, and degree of charge separation is uncertain. However, climatology suggests that even quite shallow/warm CBs tend to be electrified in this region at this time of year.