Storm Forecast
Valid: Mon 04 Apr 2011 06:00 to Tue 05 Apr 2011 06:00 UTC
Issued: Sun 03 Apr 2011 16:42
Forecaster: SCHLENCZEK
A level 1 was issued for northern Ireland and Scotland mainly for damaging wind gusts and tornadoes.
SYNOPSIS
Numerous shortwave troughs move across western and northwestern Europe and lead to unsettled conditions. High pressure is building over central Europe while an upper cut-off low is present over the western Atlas mountains. Another cut-off over Turkey and the eastern Mediterranean should be associated with some thunderstorm activity as low-end instability is in place. Cold air convection may develop over S Scandinavia during the day. Later in the period, the British Isles will be affected by some showers and thunderstorms which are associated with a strong low pressure system south of Iceland.
DISCUSSION
...N Ireland, Scotland...
The cold front of a strong low pressure system should reach the British Isles in the late evening hours. Some few hundred J/kg CAPE should be present and besides strong forcing from the upper trough, very intense 0-1 km and 0-3 km shear is forecast. Given 30 - 35 m/s background winds at 700 hPa, severe wind gusts in excess of 25 m/s are likely to occur, locally even more than 32 m/s. Enhanced 300 - 500 mē/sē SRH3 combined with strong LL shear may suggest a tornado threat as well. As the gradient wind is also rather strong and the convective contribution to the gust intensity is probably not that high, a threat level 1 is issued in this situation.
...S Scandinavia...
An upper trough located over S Norway on Monday morning leads to a few hundred J/kg CAPE over the Norwegian Sea and northern North Sea. Deep layer shear is quite weak, only locally more than 10 m/s, which should preclude severe weather. During the evening, instability vanishes and convective activity should diminish.
...S Iberian Peninsula, N Maghreb States...
Some instability is forecast in an environment with weak vertical shear and an absence of forcing. This may lead to a few showers and thunderstorms which are likely non-severe. During the first half of the forecast period, CIN is quite high and only isolated thunderstorms can be expected.
...E Mediterranean, Turkey, Cyprus...
A few hundred J/kg CAPE should be created during the day, leading to briefly organized showers and thunderstorms. Deep layer shear should be less than 10 m/s and severe weather should be unlikely. An isolated large hail event cannot be discounted but a threat level is not warranted.
