Storm Forecast
Valid: Mon 12 Jun 2006 06:00 to Tue 13 Jun 2006 06:00 UTC
Issued: Sun 11 Jun 2006 20:38
Forecaster: GROENEMEIJER

SYNOPSIS

Monday at 06:00 UTC... an elongated ridge should stretch from eastern Spain to Scandinavia. West of the ridge, a SSWly flow advects warm air northward. Over southern Italy a closed low is expected. An elongated trough extends from the Komi region over Moscow to the western Ukraine.

DISCUSSION

Britain...

A cold front that forms the western edge of the warm tongue is expected to stretch initially from western Scotland to Cornwall and progress slowly eastward over Britain during the day. It is likely that a prefrontal convergence forms. With 28 degree temperatures and 18 degree dew point temperatures expected, about 1500 J/kg SBCAPE or 500-800 J/kg MLCAPE should become available. A couple of storms will likely form along the convergence line. Some will likely become well-organized multicell storms given that about 15 m/s deep-layer bulk shear is expected. Severe wind gusts appear quite likely, primarily across northern and central England where low-level winds are strongest... around 20 m/s at 850 hPa. The development of a progressive bowing system is however small as the initiating boundary and shear vector are oriented roughly parallel and forcing for upward motion is only moderate. Some flash flood threat will exist as the NNEward-moving storm systems will tend to back-build in SSWly direction, causing some areas to be affected by many individual storm cells.
Finally, the storms may produce some large hail locally, although the moderate mid-level lapse rates may reduce that threat somewhat.

northwestern France

Models indicate that storms may well form ahead of the front across northwestern France as well. Here, wind shear and thereby the severe threat are somewhat lower. A few isolated severe events cannot be ruled out however.

Portugal, western Spain

A few 100's of J/kg of weakly-capped CAPE are expected to form in the area. Scattered convective storms should form during the day. Given inverted-V-like forecast soundings, isolated strong downbursts are possible, possibly approaching severe levels in places.

western Balkans, Adriatic, southern Italy...

Low LCL and LFC heights and weak low-level flow suggest that there is a relatively high threat of weak spout-type tornadoes/waterspouts with the storms occurring in those areas.