September 2015 CET forecasts

[The PIT]

Sunny Sheffield 12.2C the final figure coldest since 1986 unless there's a heatwave overnight.

[Stargazer]

Definitely seems like we've just had a cool month here - and the provisional MetO anomaly maps show that our area hasn't been particularly dry or sunny either.  As PIT says the month has been notable for its lack of variation - seems like endless days of 16-18 maximum/8-10 minimum or thereabouts here.  The highest we achieved was 21.6C and we haven't reached 20C since the 11th.  Must be the lowest maximum temperature in September here for many years.

Edited October 1, 2015 by Stargazer

[summer blizzard]

I've loved this month personally. There's been a notable lack of humidity, cool nights, plenty of sun and the current high pressure has been more akin to those we get in March than our usual humid pressure builds this late.

[Costa Del Fal]

I've loved this month personally. There's been a notable lack of humidity, cool nights, plenty of sun and the current high pressure has been more akin to those we get in March than our usual humid pressure builds this late.

Humidity is rarely a problem in this country at this time of year anyway? I really fail to see how it can ever be such an inconvenience by now really.

[BornFromTheVoid]

Not all the daily data have been corrected, the 25th isn't in the final data set yet, but from the corrections so far it looks like 12.6C or 12.7C will be the final figure.

 

It will be 12.6C if the correction for the 25th is a drop of at least -0.5C, anything else should result in a final value of 12.7C.

[Lettucing Gutted]

Maybe he means

 

humidity = cloudy high ?

Even clean highs can be humid.  Remember Julys 2006 and 2013 and Septembers 2006 and 2011 and 2014?

[J10]

Not all the daily data have been corrected, the 25th isn't in the final data set yet, but from the corrections so far it looks like 12.6C or 12.7C will be the final figure.

 

It will be 12.6C if the correction for the 25th is a drop of at least -0.5C, anything else should result in a final value of 12.7C.

 

I will compile the scores over the weekend, assuming the CET comes out tomorrow.

[summer blizzard]

Humidity is rarely a problem in this country at this time of year anyway? I really fail to see how it can ever be such an inconvenience by now really.

It may not get much above 25C but most September settled spells tend to be pretty humid even when sunny. I don't like humidity at all when warm.

[Don]

I wonder if September will be the last colder than average month of 2015?  The latest signs seem to be that the rest of Autumn and early Winter are likely to be generally mild and damp.

[Summer Sun]

September confirmed as 12.6c

 

http://www.metoffice.gov.uk/hadobs/hadcet/cet_info_mean.html

[Weather-history]

Minimum wise, it looks as though it was the coolest September since 1986.

[cheese]

Even clean highs can be humid.  Remember Julys 2006 and 2013 and Septembers 2006 and 2011 and 2014?

July 2006 wasn't humid at all. I remember the hottest days around 31-32C having dew points around 12-13C, so on the dry side if anything. High humidity is not conductive to hot weather - that's why the hottest weather anywhere in the world occurs when/where it is dry.

 

Heathrow, 18 July 2006: http://www.ogimet.com/cgi-bin/gsynres?ind=03772〈=en&decoded=yes&ndays=2&ano=2006&mes=07&day=18&hora=23

 

Notice how low the dew points are?

 

19 July: http://www.ogimet.com/cgi-bin/gsynres?ind=03772〈=en&decoded=yes&ndays=2&ano=2006&mes=07&day=19&hora=23

 

Even drier - dew point of 8C with 35C temps!

 

So no, humidity is rarely a problem in the UK when it's actually properly hot - though there are exceptions.

Edited October 2, 2015 by cheese

[mulzy]

July 2006 wasn't humid at all. I remember the hottest days around 31-32C having dew points around 12-13C, so on the dry side if anything. High humidity is not conductive to hot weather - that's why the hottest weather anywhere in the world occurs when/where it is dry.

 

Heathrow, 18 July 2006: http://www.ogimet.com/cgi-bin/gsynres?ind=03772〈=en&decoded=yes&ndays=2&ano=2006&mes=07&day=18&hora=23

 

Notice how low the dew points are?

 

19 July: http://www.ogimet.com/cgi-bin/gsynres?ind=03772〈=en&decoded=yes&ndays=2&ano=2006&mes=07&day=19&hora=23

 

Even drier - dew point of 8C with 35C temps!

 

So no, humidity is rarely a problem in the UK when it's actually properly hot - though there are exceptions.

 

Indeed.

 

Has it ever been exceptionally humid in the UK during the summer months? (cf. tropical regions - Singapore, Sri Lanka etc.)

[BornFromTheVoid]

A few graphs for the month:

 

Daily CET before and after corrections

 

 

Just the corrections

 

 

September 2015 compared to the recent average and extremes over the entire record

 

[damianslaw]

A break from the norm then, most Septembers over the last 30 years have been average or significantly above. The year so far is balancing out to be nearly bang on the 61-90 average, so a cool year so far relative to recent period 81-10 period. I do wonder when the met will start using the 81-10 average?

[Relativistic]

A break from the norm then, most Septembers over the last 30 years have been average or significantly above. The year so far is balancing out to be nearly bang on the 61-90 average, so a cool year so far relative to recent period 81-10 period. I do wonder when the met will start using the 81-10 average?

 

I think the WMO recommends using the 61-90 average until 2021, so that the 61-90 average is used for 30 years, then the 81-10 average is used for another 30 years, etc.

[J10]

Results just calculated, based on the 12.6c confirmed value.

 

Monthly (and Seasonal)

2 players got it spot on, seabreeze86 Godber 1

These are 1 and 2 in the Seasonal comp with 22nov10blast in 3rd

 

Overall the top 3 is

1. summer blizzard

2. BornFromTheVoid (up from 5th)

3. coldest winter

 

Full Details

Sept 2015 CET.pdf

Sept 2015 CET.xls

 

Any problems let me know (politely)

 

Stat Zone

 

Baseline (1981-2010)      14.0 Actual CET      12.6 Average Entry      13.6 Difference -      1.0 Correlation -    0.30

 

With the negative correlation showing that earlier entries did worse, with initial entries doing the worst by a margin. (the same as last month)

On average, people went for cooler than average, however as it was so cool, the actual results was colder than most thought.

Edited October 3, 2015 by J10