Storm Forecast
Valid: Thu 03 Apr 2008 06:00 to Fri 04 Apr 2008 06:00 UTC
Issued: Wed 02 Apr 2008 21:09
Forecaster: GATZEN

SYNOPSIS

High over Iberian Peninsula and Bay of Biscay ridges into British Isles and North Sea. This ridge connects to Scandinavian/Russian high pressure as central European polar trough cuts off into south-eastern Europe and north Mediterranean. A strong upper jet streak will move southward over western Germany reaching central Mediterranean during the period. Downstream, short-wave troughs over east Mediterranean move eastward providing QG forcing. At the end of the period, a strong westerly flow is expected over east Mediterranean. At low levels, warm and moist air mass is present over east Mediterranean, while cold air spreads into central Mediterranean. Warm and stable air is present over Iberian Peninsula.

DISCUSSION

Southern Adriatic to Aegean

Main focus of expected convective activity will be the in range of a strong upper jet streak that curves around the developing cut-off trough. It will likely provide strong QG forcing as rather warm low-level air mass will remain in the range of the trough axis. At mid-levels, models indicate -25°C at the 500 hPa level. This will likely result in CAPE over the affected region, and latest soundings indicate steep lapse rates at low and mid levels over northern Italy on WED.

Current thinking is that showers and thunderstorms will go on in the range of the short-wave trough axis, spreading eastward on THU. Over the sea surface, convection may be weaker as diurnal heating will be weak. Thunderstorms may merge into clusters given quite strong QG forcing. Best potential for organized convection is expected in the southern area of the trough, where deep layer vertical wind shear will be strong. Bowing lines and isolated mesocycones may form, capable of producing strong to severe wind gusts, isolated large hail, and tornadoes. Limiting factors will be relatively poor veering profiles and low-level vertical wind shear.