June retrospective
June is likely to end up as yet another below average month but not by too much. This could be the third June in a row to finish in the 13's. Prior to that we only had three June's below 14C in a 20 year period.
Here is a quote from my pattern matching summary in the June thread "The pattern matching suggests a June CET somewhere between 13.5C and 14.1C is the most likely scenario". Good call there by the pattern matching this month. The CET will probably finish in the middle of that range.
Looking ahead to July
There are encouraging signs that after a somewhat indifferent first week of July (although still with some warmer spells) we could see the first sustained period of warm weather in the second week of July. The outlook is definitely the most promising I have seen so far this year in terms of seeing a warmer than average month. However, the pattern matching (see the end of this post) suggests some caution is needed. There is no recent precedent for a July CET of 17C or more against the backdrop of a cold Spring and indifferent June.
Please place your July CET predictions in this thread. The deadline for entries with no penalty is 23:59 on 30 June. Late entries will be accepted up to 23:59 on 2 July but are subject to a penalty of 0.2C per day for the purposes of the annual competition.
July historic data summary
Here is the usual rundown of historic data for previous years.
Only one of the past 6 July's has been above average and that was 2010 when we just sneaked over 17C. Both 2011 and 2012 were dismal with mid to low 15's. 2011 at 15.2C was the equal coldest July since 1988. July 2006 was the last very warm July with 19.7C.
Long run averages:
1971-2000: 16.5CInsert/Edit Embedded Media
1981-2010: 16.7C
1988-2012: 16.6C
Here is a chart of the July 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
The sine wave pattern for the first week suggests unsettled weather with warmer and cooler spells alternating. Good agreement on above average conditions for the second week. The question is can this be sustained into the second half of the month?
ECM ensembles (De Bilt)
http://www.knmi.nl/exp/pluim/vijftiendaagse/index.php
The mean is fairly steady for the whole run. Nothing better than average conditions generally.
Weatheronline
The forecast is way out of date so not even worth posting.
Met office
http://www.metoffice.gov.uk/media/pdf/8/d/A3-plots-temp-JAS.pdf
3 month contingency planners forecast for June to August suggests a very average month with the range of options almost exactly in line with the long run average per the graph. The same goes for the 3 month period to September. However the text suggests a slightly greater chance of below average rather than above average conditions. Weak La Nina conditions are possible in the coming months.
http://www.metoffice.gov.uk/public/weather/forecast/?tab=regionalForecast
30 day forecast - turning warmer in the south during week two after an average start. Second half of the month generally average although some warm periods in the south at times.
Pattern matching (just for fun)
I have looked at the following matching conditions since 1900 - May / June CET 11.4C to 12.7C combined with Apr - June CET of 10.2C to 10.9C and June CET of 13.2C to 14.2C. There are 11 matching years including 2012.
6 years had a July CET between 16.0C and 16.9C. Only 2 were above the 1971-2000 mean of 16.5C. 3 years had a July CET between 15.0C and 15.9C and 2 years had a July CET between 14C and 14.9C. The coldest was 1954 with 14.2C and the warmest 1969 with 16.8C.
For those of you keeping an eye on how 2013 compares to 1962 well 1962 is also a matching year which saw a July CET of just 15.1C. I doubt it will be that cold this year.
So the pattern matching suggests about a roughly 50% chance of the July CET being within 0.5C of the mean and a 50% chance of being more than 0.5C below the mean.
Based on the current model output I think we are likely to be in the first category where the CET finishes in the 16's. Best guess at this stage would be something between 16.2C and 16.8C.
Edited by moderator
12 August 2013 08:39:16
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