TORRO TORNADO WATCH 2009/007
A TORNADO WATCH has been issued at 23:20GMT on Saturday 31st October 2009
Valid from/until: 0430-1600GMT on Sunday 1st November 2009 for the following regions:
Parts of (see map)
England & Wales
S Scotland
Isle of Man
Channel Islands
Eastern Eire
THREATS
Tornadoes and wind gusts of up to 70mph; isolated CG lightning.
Rapidly developing Atlantic depression will move NNE late tonight and through tomorrow, the most likely track is through the Irish Sea into S Scotland. Close to the storm's centre, a marked dry intrusion/frontal fracture may allow some convection to develop, in a highly sheared environment. Marked low-level shear brings the risk of isolated tornadoes - in addition, wind gusts of 60mph are possible, perhaps 70mph in places. There is a small risk that a sting-jet may develop, enhancing the wind risk.
To the south of the depression, a well-marked cold front will surge eastwards...this is likely to split, so rather intense precip, perhaps with lightning, could develop ahead of the surface front, althoug rather stable/saturated low-level air ahead of the front would limit the risk of convective gusts. The surface front looks fairly likely to be marked by a line of forced convection. Strong low-level shear ahead of this means that misocyclones may develop along this front, bringing a risk of locally damaging winds, and perhaps isolated tornadoes. At this stage it is not clear whether this convection will be deep enough for lightning.
Even at this late stage, the track of the depression is stil rather uncertain. This forecast may well be updated/amended in the morning, as the situation develops.
Forecaster: RPK.
