Convective Forecast
 

CONVECTIVE FORECAST
VALID 06Z SAT 23/10 - 06Z SUN 24/10 2004
ISSUED: 22/10 19:33Z
FORECASTER: DAHL

General thunderstorms are forecast across E Spain ... Italy ... the Balkans.

SYNOPSIS

Large upper trough over the Atlantic is progged to move slowly southeastwards ... resulting in backing upper flow/ridging over W and central Europe. Small vort max in this strong SWLY flow is FCST to support a frontal wave expected over the S British Isles by Saturday late afternoon/evening. Weak vort max is expected affect Italy ... the Adriatic Sea and the W Balkans on Saturday. At low levels ... complex elongated low pressure system is covering the E Atlantic and parts of N Europe ... yielding deep SSWLY low-level flow extending from the SW into the NE European States.

DISCUSSION

...S British Isles...
Only feature aiding in providing potential severe TSTM environment should be the small and fast vort max and the accompanying wave cyclone expected to reach the S British Isles in the afternoon/evening hours. Again CAPE will be the main concern. The warm-sector air mass has allowed for isolated lightning over the Atlantic on Friday afternoon/evening ... and chances exist that it will continue to do so on Saturday. Models do show weak signals in the CAPE fields ... but allover chances that widespread TSTMS will develop appear to be quite low ATTM. If reasonably deep convection forms ... vigorous shear could promote an isolated severe TSTM event or two ... but confidence is limited and will thus not issue TSTM or severe outlook ATTM.

...Mediterranean regions and the Balkans...
Air mass over the W Mediterranean appears to become increasingly capped ... and weakly unstable ... as steep lapse rates are overspreading the region ... limiting the TSTM threat. Best chances appear to exist over E Spain ahead of weak vort max. Farther east ... capping should be somewhat weaker ... and large-scale forcing for UVV's should be somewhat stronger ... which could promote scattered TSTMS. Weak CAPE and weak shear suggest that severe TSTM threat will be quite low.

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