Overall, September has proven pretty successful in terms of drier and more settled across much of the UK and as pointed out back in late August, there will be spells of unsettled but the emphasis should be largely on higher heights than that of the June-August period.
Brief Ocean-Atmosphere Overview
Interestingly the cool theme continues from summer into autumn’s first month across Ireland and the UK. September marks the 5th straight below normal month temperature wise, directly linked to cold water extending from the central North Atlantic to Ireland. Following a warm, dry March and April, the trend kicked off in May with the coolest since 1996 and it’s been cool ever since, despite the record hot open to July. The continent on the other hand has been warm or record warm throughout the past 3-5 months, linked directly to warmer than normal water as well as the influence of El Nino.
June-August temperature anomaly
However, during September, SSTA’s ( sea surface temperature anomalies) are now changing north and south.
September so far… 5th straight below normal month for UK.
What’s different is that while waters are warming around Scandinavia, their cooling off Iberia, hence cooler in France and Spain with much more unsettled conditions, warmer in Scandinavia where ridging has been dominant in recent weeks. The reversal of high heights to the north and low heights further south has helped flip SSTA’s and air temperature anomalies around.
Current SSTA’s.
Change in last 7 days. Note the cooling west of Portugal and warming across the North Atlantic as well as around the UK.
As we head for mid autumn (seasonal shift begins) and it’s watching this carefully that helps foresee pattern changes as the season progresses from one to the other. colder than normal down over Spain and France and the warmer than normal up across Scandinavia, though waters are now warmer than normal around particularly N Scandinavia.
How’s October Looking?
With ocean cooling and warming in opposite areas to summer and atmospheric seasonal shift, I suspect the first half of October to be drier than normal from Spain to Scotland with below normal temperatures extending from central Spain up to England and warmer than normal from Scotland into Scandinavia extending west into Ireland but possibly change comes through the second half of the month with a turn to wetter.
CFSv2 500mb heights for October
CFSv2 2 metre temperature anomaly
CFSv2 Precipitation anomaly
CFSv2 weekly breakdown!
500mb height anomaly
CFSv2 2 metre temperature anomaly
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