CONVECTIVE FORECAST
VALID 06Z FRI 22/08 - 06Z SAT 23/08 2003
ISSUED: 21/08 21:24Z
FORECASTER: GATZEN

There is a slight risk of severe thunderstorms forecast across Eastern and northern Spain, western Mediterranean

General thunderstorms are forecast across parts of the Mediterranean, parts of eastern Europe

SYNOPSIS

The southern European flow pattern is dominated by an upper short-wave trough over Iberian Peninsula. East of this feature ... the mid-tropospheric geopotential is forecast to rise due to WAA. Weak long-wave trough is situated over the eastern Mediterranean, and some vort-maxima travel around its periphery. Northern European flow regime is characterized by a zonal flow and embebbed short waves.

DISCUSSION

...Iberian Peninsula, western Mediterranean...
Upper short-wave trough axis will remain over western Iberian Peninsula, yielding a southwesterly flow over western Mediterranean. Well-mixed warm airmass originating from the Atlas mountains will spread northward above the 850hPa-level. At lower levels ... northeasterly winds and warm/ moist Mediterranean airmass will remain east of a convergence line over the Iberian Peninsula. Soundings indicate well-defined capping inversion and more than 1000 J/kg CAPE over eastern Iberian Peninsula and western Mediterranean. ATTM, storms have formed over central and eastern Spain and should weaken slowly. On Friday ... storms should form over eastern and central Spain. Convectively mixing will reduce CAPE over some places, and clouds could inhibit insolation. However ... large CAPE values should be possible during the day, especially over eastern Spain/ western Mediterranean, where insolation is forecast to be strongest and steep lapse rates will be most likely. Moderate vertical shear could support thunderstorm organization over the eastern and northern part of the affected area. Multicells and supercells will possibly form. If supercells develop ... large hail and severe wind gusts should be the main severe threat. However ... tornados are not ruled out ATTM if orographically enhanced low-level shear will be present.

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