CONVECTIVE FORECAST
VALID Thu 01 Sep 07:00 - Fri 02 Sep 06:00 2005 (UTC)
ISSUED: 01 Sep 07:44 (UTC)
FORECASTER: GATZEN

SYNOPSIS

Blocking high has developed over central Europe, ridging into Scandinavia. Upper troughs are present over western Russia and northeastern Atlantic. At the eastern flank of Atlantic long-wave trough ... strong upper jet affects western Europe. Short-wave troughs that are present at the base of the long-wave trough will affect western Europe today. Over eastern Mediterranean ... weakening upper trough merges to eastern long-wave trough. At lower levels ... tongue of high THETA-E stretches from eastern Iberian Peninsula to southern France, western Alps, Benelux, and North Sea region. Cold airmass spreads into British Isles, northern France, and western North Sea during the day. CAA is also expected from eastern Scandinavia to Poland and further to Black Sea region.

DISCUSSION

...Eastern Spain to southern France, western Alps, western Germany ...
Tongue of warm and unstable airmass will be present in the range of a convergence/surface cold front today. Latest soundings show steep mid-level lapse rates and rather rich low-level moisture. CAPE up to 1000+ J/kg may be possible in response to diurnal insolation. Rather strong capping inversion is expected in the morning hours ... limiting chance for initiation. During the day ... quite strong short-wave trough travels eastward over France and northern Iberian Peninsula, providing QG forcing. Thunderstorms are forecast to develop over northern and eastern Iberian Peninsula as well as over southern France and western Alpine region. Further north ... several vort-maxima embedded in the southerly flow will affect western Germany, Benelux, and North Sea region. At the surface ... cold front/convergence line is expected to propagate eastward into central Germany. Thunderstorms are forecast to develop along this low-level convergence and should spread northeastward. Although low-level winds will be easterly over most of the affected region ... southerly jet seems to be too weak for strong DLS ... and chance for organized convection seems to be quite low. A few severe events are expected from northeastern Spain to southern France and western Alps, as well as over western and northwestern Germany. Isolated large hail and intense precipitation/local flash flooding should be the most significant threat.

...Channel region, southern North Sea ...
Rather strong upper vort-max affects southern North Sea late in the period. Expect that cold maritime airmass will be characterized by steep low-level lapse rates and some CAPE ... showers and thunderstorms may form. Thunderstorms that form will have a potential of being organized given strong (20+ m/s) DLS in the range of the upper vort-max. Multicells and bowing lines may form ... capbale of producing severe wind gusts and probably a tornado.

...Southern Greece...
Warm and slightly unstable airmass is present over eastern Mediterranean in the range of upper short-wave trough. However ... strong capping inversion is expected to inhibit convection. Over southern Greece ... diurnal insolation/orographic support may lead to initiation during the afternoon. If a thunderstorm will develop ... it may be severe given strong DLS. Initiation is not expected ATTM.

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