CONVECTIVE FORECAST - UPDATE
VALID Sun 19 Jun 15:00 - Mon 20 Jun 06:00 2005 (UTC)
ISSUED: 19 Jun 15:06 (UTC)
FORECASTER: Dahl

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

SYNOPSIS

Not too much of a change expected ... E European/Russian upper low will remain in place trough Sunday ... as will be central European upper ridge and the Atlantic upper low. Peripheral vort maxima are progged to affect the NW parts of the British Isles and may be one focus for convective development. At low levels ... quiescent conditions persist across the SRN parts of Europe ... with two SFC lows present over W Russia and the east Atlantic ... and a weakening SFC high in between over central Europe.

DISCUSSION

...Amendment Discussion British Isles...
Strong insolation has allowed SFC temperatures to climb into the upper 20's C. Several TSTMS have initiated along SFC boundary stretching across the UK ... and are expected to increase in coverage over the next few hours as large-scale ascent overspreads the region. Shear should be sufficient for a few severe TSTMS ... capable of producing large hail and severe straight-line winds. About 13 m/s 900 hPa SWLY flow has been revealed by Albermarle 12Z ascent ... with 5 m/s SELY SFC flow ... and despite other soundings indicating somewhat weaker low-level shear profile ... mesocyclones that form may develop low-level rotation with an attendant tornado threat especially late in the evening hours when LCL heights decrease.

Maximum of UVM is expected to reach the UK late Sunday night/early Monday morning. Uncertainty exists whether mesoscale ascent along the front will continue to support TSTM development once insolation ceases. As large-scale UVM should gradually increase during the next hours ... TSTMS could be sustained with upscale growth into one or more MCSs ... with peak activity around midnight. Re-development of TSTMS may occur towards early Monday morning ... with somewhat lesser severe threat given weaker thermodynamic fields. However ... isolated severe may still occur also with this activity.

...other areas...
Refer to convective forecast from 18 Jun 19:25 (UTC).

#