martinastro
Martin Mc Kenna
Global Moderator
Hero Member
Posts: 5182
Maghera, N. Ireland
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« Reply #15 on: December 07, 2009, 11:24:17 pm » |
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Or maybe not, this was posted by Matt from the UKWW....
-3C 850 mb Wet Potential Temps across the E and SE for a time next Tues/Wed if you believe ECMWF 12z, blasting down from the NE (exceptionally cold air floods SW out of NW Russia across E Scandinavia a day or two before, and warms slightly as it heads SW). However, as Paul says it is mainly Europe that is affected thereafter, as upstream developments (over NE USA and E Atlantic) would eventually favour a 'toppling' warm ridge across the UK by the end of next week, rather than a prolonged easterly flow.
So, chance of a couple of cold easterly incursions. The first this Sat and a second, potentially much colder one the following Tues/Wed with something briefly less cold in between as a low slides SSE down the N Sea and brings a shot of Atlantic air with it. Growing confidence on the intial one (should lead to a frosty weekend over S and E areas at least) but still moderate/low confidence on the 2nd IMO.
Thereafter, quite tricky to pin down exactly what will happen but this will hinge on factors such as the upstream pattern over the USA/Canada and E Atlantic and whether the flow will remain strongly meridional here or not. Unless the jet stream is forced south under the block by deep trough in the eastern/central Atlantic, a more zonal flow to our west will not favour prolonged blocking. GFS 12z, IMO, is more than likely going OTT and should be taken with a pinch of salt at this stage!
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