Storm Forecast
Valid: Wed 23 Apr 2008 06:00 to Thu 24 Apr 2008 06:00 UTC
Issued: Tue 22 Apr 2008 21:35
Forecaster: GATZEN

SYNOPSIS

Polar jet forms an omega over Europe, with a blocking high centred over southern Scandinavia and two troughs situated over northern Atlantic and northern Balkans/Black Sea region. The omega will slowly propagate eastward during the period. At lower levels, rather cool air mass is present over most of Europe, while remaining very warm air mass over south-eastern Europe will be pushed eastwards by a cold front associated with the eastern trough. Where diurnal heating is strong, low-level mixing is easily achieved. Deep moist convection is expected especially in the range of cold mid-level air mass, where higher convective equilibrium is present.

DISCUSSION

Romania, Bulgaria

Relatively warm and moist low-level air mass is present over Romania and Bulgaria to the south of propagating cold front Ukraine. During the period, axis of upper level trough will enter the region, while low-level cold front will cross Romania. In the range of the warm air mass, relatively steep lapse rates will be present, and given some diurnal heating and low level dew point around 8°C, expect that CAPE will likely develop. Showers and thunderstorms are forecast given at least weak low-level convergence over the central regions of Romania and Bulgaria. Thunderstorms that form are expected to move eastward, while chance for severe convection is rather low given decreasing vertical wind shear. Isolated large hail may be possible with stronger cells, though. The chance for tornadoes is only low given weak vertical wind shear, but locally strong low-level buoyancy may favour an isolated event. Convection is forecast to die during the night hours given weak QG forcing and rapidly decreasing CAPE due to dry low-level air mass spreading southward.

Northern Ireland

Ahead of the Atlantic trough, a strong mid-level jet curves northward reaching Ireland during the day. At lower levels, weak cyclogenesis is forecast along a frontal boundary moving into Ireland. Ahead of this frontal boundary, a warm and moist air mass is forecast to enter Ireland. Amount of instability seems to be the most critical ingredient for severe convection. Low-level moisture is forecast to be rather rich as dewpoints may reach around 10°C. Mid-level cold air will also be present, but low-level lapse rates may be stable initially given cold sea surface temperature. As a consequence, severe convection may not form even with moderate QG forcing and moderate vertical wind shear. Where strong low-level buoyancy may develop, tornadoes may be possible given favourable vertical wind shear.



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