Storm Forecast
Valid: Mon 19 Nov 2007 06:00 to Tue 20 Nov 2007 06:00 UTC
Issued: Sun 18 Nov 2007 20:17
Forecaster: GROENEMEIJER

SYNOPSIS

Monday at 06:00 UTC... a large vertically-stacked pressure area is located over the southwestern British Isles and is expected to move a bit westward during the forecast period. Gradually a poleward fluc of warm air is expected to become established east of a frontal zone stretching from western Iberia into France and northern Germany. Downstream, a ridge along an axis from Tunisia to Poland strengthens. A second major low presure area over central Greece is expected to move to southwestern Turkey. In its vicinity and to its south, scattered thunderstorms are expected.

DISCUSSION

Southwestern Iberia...

A stable frontal wave is initially located about 500 km west of southern Portugal and moves rapidly northeastward, reaching western France on Tuesday morning, when a second wave moves into Iberia. In vicinity of the waves strong low-level jets develop on the front's warm side with velocities around 25 m/s. The low level flow advects warm, moist and slightly unstable air off the Atlantic Ocean towards the Iberian Peninsula, that reaches the Iberian coast starting Monday late afternoon.
The strong shear suggests that embedded thunderstorms will likely include linearly organized lines and possibly a few mescyclones with an attendant threat of strong to severe winds, perhaps some large hail and a low tornado threat. The storms are expected to persist into the next forecast period.