CONVECTIVE FORECAST
VALID 12Z SUN 10/08 - 06Z MON 11/08 2003
ISSUED: 10/08 12:08Z
FORECASTER: DAHL

There is a slight risk of severe thunderstorms forecast across the UK.

General thunderstorms are forecast across SW ... S ... central and E Europe.

SYNOPSIS

Large-scale setup remains largly unchanged ... with two quasistationary upper long-wave troughs over the E Atlantic and over E Europe, respectively ... and an upper longwave ridge in between over central parts of Europe.

DISCUSSION

...eastern British Isles...
Camborne (S UK) and BOLAM 850 hPa theta-e fields indicate that an (slightly elevated) steep lapse rates are being advected into the profrontal environment. Elevated TSTMS are currently ongoing amidst theta-e advection regime over central parts of the UK and over the N sea ... while the SE parts are experiencing unimpeded insolation ... pushing temps into the mid/upper 30s. High SFC dewpoints (locally higher than 20°C) are in the process of being mixed out ... and thermodynamic profiles should resemble those across the rest of central and SW Europe towards the afternoon ... small CAPEs and a deep dry-adiabatically mixed subcloud layer. As fast moving vort max crosses the British Isles late tonight ... widespread TSTMS should be initiated during the next few hours. In addition to the downburst threat owing to the dry environment ... increasing deep-layer shear (50+ knots late in the evening) could promote lines of TSTMS with bowing segments and an isolated supercell or two ... with primary threats being damaging wind gusts and possibly a few large-hail events. Suspected weak capping and expected widespread convective development may limit allover severe threat somewhat. Formation of a slightly elevated MCS is anticipated late in the evening/night which should slowly decay over the north sea.

...east-central Europe...
Along and in the wake of a cold front curving from Scandinavia across Poland into Russia ... rathere shallow TSTMS are present ahead of vort max at the W periphery of the E European upper trough. Though instability is quite meager ... deep-layer shear of 50+ knots will likely promote strong outflow winds and possibly some hail as a few rotating updraft may occur. Weak thermodynamic dupport precludes a SLGT ATTM.

...southwest ... south ... central Europe...
Another round of scattered diurnal high-based TSTMS is expected over central and SW Europe in weakly-capped and weakly unstable air. Isolated/brief downbursts are possible along with small hail ... but too isolated to warant a slight risk.

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