August retrospective
A second consecutive above average month. While nowhere near as warm as July this August has been a very decent summer month with plenty of warm and sunny weather. This will be the warmest August in the CET area since 2004. The CET for the 1st is likely to be the warmest since 19 July 2006 and could be warmer than all but one other day in the hot 2006 summer.
Looking ahead to September
We may have a reasonably warm start to September but then there is a fair amount of uncertainty in the models so difficult to say what might happen after day 4.
Please place your September CET predictions in this thread. The deadline for entries with no penalty is 23:59 on 31 August. Late entries will be accepted up to 23:59 on 2 September but are subject to a penalty of 0.2C per day for the purposes of the annual competition.
September historic data summary
Here is the usual rundown of historic data for previous years.
Last year we saw the first significantly below average September since 1994 with a CET of just 13.0C. Generally September has been a very warm month with a record CET of 16.8C in 2006. But the September CET has exceeded 15C only once since 2006.
Long run averages:
1971-2000: 13.7C
1981-2010: 14.0C
1988-2012: 14.1C
Here is a chart of the September CET since 1961 with a 10 year moving average
Here are some details of what the models and forecasters generally are saying at the moment.
GEFS
http://www.wetterzentrale.de/pics/MT8_London_ens.png
http://www.wetterzentrale.de/pics/MT8_Manchester_ens.png
A warm start but then a lot of scatter with the GEFS mean around average.
ECM ensembles (De Bilt)
http://www.knmi.nl/exp/pluim/vijftiendaagse/index.php
Generally average with just a couple of warm days near the beginning of the month. But a lot of scatter with a few very warm solutions.
Weatheronline
http://www.weatheronline.co.uk/cgi-app/reports?MENU=Month-ahead
Out of date but suggests there could be plenty of warm weather in September with some cooler interludes.
Met office
http://www.metoffice.gov.uk/publicsector/contingency-planners
Contingency planners forecast not yet available but should be available very soon
http://www.metoffice.gov.uk/public/weather/forecast/london#?tab=regionalForecast&map=SignificantWeather&locId=352409&zoom=8&lon=-0.12&lat=51.51&fcTime=1377680400
30 day forecast - overall looks fairly average for September
Pattern matching (just for fun)
Looking at years since 1900 with a summer CET of 15.9C to 16.7C and an August CET of 16C to 17.6C there are 10 matches. Three years have a September CET within +-0.5C of the 1971-2000 mean, one year is more than 0.5C below the mean, 5 years are between 0.6C and 1.5C above the mean and one year is more than 1.5C above the mean.
So a slight bias here towards an above average month.
Edited by moderator
29 August 2013 19:31:36
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