Lrf Update - Friday 16 July 2010
Entry posted by johnholmes
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If you look at my post from last week I suggested that a spell of 7-10 days unsettled weather was likely before it settled down by the end of the month.
The generally unsettled pattern has occurred and will likely last for a few days yet.
However I stick by the suggestion I posted that surface high pressure will become the dominant factor by the end of this month.
On the synoptic scale the 500mb anomaly charts, all 3 versions, have slowly come round to the idea of an upper ridge developing SW of the UK, part of the Azores surface high. This will edge into the UK by the end of the month and into the first week of August. It is likely to keep the south-north divide going but perhaps more SW-NE this time. How far the surface high centre beneath the upper ridge will edge east is far from certain. The major wave lengths suggest that it will be a very slow process. This MAY lead to home grown heat developing as a result for the southern areas, England and Wales and parts of eastern Scotland perhaps. Northern Ireland is less clear probably staying in the more unsettled area most of the period. With a surface high setting up then winds should not feature much other than the occasional fresh to strong in the far North West as weather systems run up the western edge of the ridge. I’m not at all sure about thundery rainfall on its SW’ern flank this far out. It is a possibility if the ridge gets east of about 5 East.
Other factors, QBO, ENSO, AO, NAO etc all seem to me to support something along these lines.
So a more summery spell looking likely for much of the southern half of the UK, and possibly less unsettled for the far North West, certainly than recently.
The proof of the pudding as they say, so I’ll look again, next week, probably be Sunday before I can get round to doing another update.
The generally unsettled pattern has occurred and will likely last for a few days yet.
However I stick by the suggestion I posted that surface high pressure will become the dominant factor by the end of this month.
On the synoptic scale the 500mb anomaly charts, all 3 versions, have slowly come round to the idea of an upper ridge developing SW of the UK, part of the Azores surface high. This will edge into the UK by the end of the month and into the first week of August. It is likely to keep the south-north divide going but perhaps more SW-NE this time. How far the surface high centre beneath the upper ridge will edge east is far from certain. The major wave lengths suggest that it will be a very slow process. This MAY lead to home grown heat developing as a result for the southern areas, England and Wales and parts of eastern Scotland perhaps. Northern Ireland is less clear probably staying in the more unsettled area most of the period. With a surface high setting up then winds should not feature much other than the occasional fresh to strong in the far North West as weather systems run up the western edge of the ridge. I’m not at all sure about thundery rainfall on its SW’ern flank this far out. It is a possibility if the ridge gets east of about 5 East.
Other factors, QBO, ENSO, AO, NAO etc all seem to me to support something along these lines.
So a more summery spell looking likely for much of the southern half of the UK, and possibly less unsettled for the far North West, certainly than recently.
The proof of the pudding as they say, so I’ll look again, next week, probably be Sunday before I can get round to doing another update.
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