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Possible Stormy Spell 13th to 19th Nov

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Author Topic: Possible Stormy Spell 13th to 19th Nov  (Read 3760 times)
Martin Mc Kenna
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Maghera, N. Ireland

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« Reply #45 on: November 14, 2009, 07:17:37 pm »

Outlook for Sunday from Tony Gilbert....

6pm Sat

Slight Risk of Thunderstorms perimeter regions of the UK 00Z-15Z

Slight Risk of Brief Tornado South & SE coastal regions UK 00Z-09Z

Further troughing expected to bring convective showers to coastal regions across the UK overnight and into Sunday. Deep upper trough expands to surround much of the UK increasing lapse rates. Particularly so close to relatively mild Sea Surface Temps are blown inland. Upper jet stream axis remains to the south of the UK but will influence winds enough for a time during early morning to trigger the potential for some stronger convective activity within a strong upper Positive Vorticity Max. If we look at the low level shear vertical wind profiles we can see the low end scale of brief tornado genesis for the south coast, SE and eastern coast of E.Anglia for a period 00Z-09Z. The risk will transport from west of the risk box to the eastern sector steadily through this period. Risk of tornadoes remains glued to 'coastal convergence' specifically. The risk for low level vorticity looks strong and may be ingested into and strong convective cell making landfall.

Restriction ATM for tornado geneses would seem that potential instability may not be realised as the dry tongue moves too slowly behind the surface trough.

Some uncertainties for the remainder of Sunday given limited moisture and the potential for advected mild sea air to move inland. The GFS are currently having trouble developing precip for this reason. In many ways this scenario could in fact deliver some spectacular isolated cb's as John mentioned, with hail and marginal thunder activity for a time.

The shear conditions for the remainder of Sunday will remain borderline to updraft/ downdraft separation. So probably not good to underestimate what the outlook could deliver at this point.

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