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Roger J Smith

September 2018 C.E.T. forecast contest and optional EWP forecast contest

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September CET averages and extremes

... all values since 1981 are shown, colour coded for warmest, middle and coolest thirds of the 37 years.

 

22.6 ... warmest day (2nd, 1906)

21.4 ... warmest day in second half (21st, 2006)

16.8 ... warmest September (2006)

16.6 ... second warmest (1729)

16.3 ... third warmest (tied 1865 and 1949)

16.0 ... fifth warmest (1795, 2016)

15.6 ... 1999

15.2 ... 2005

15.1 ... 2011, 2014

14.9 ... 1998, 2004

14.7 ... 1989, 1991, 2000

14.6 ... 1985

14.5 ... 1981

14.4 ... 2002

14.3  ... average 2001-2017 and 2003

14.2 ... average 1991-2017 and 1982, 1997, 2009

14.1 ... average 1988-2017

14.0 ... average 1981-2010 and 1986-2015

13.8 ... 2007, 2010

13.7 ... average 1971-2000, 1983, 1984, 1995, 2013

13.6 ... average 1961-1990, 1987, 1996

13.5 ... average 1701-1800, 1901-2000, 2008, 2017

13.4 ... 1992, 2001

13.3 ... average 1659-2017

13.2 ... 1988, 1990

13.1 ... average 1801-1900

13.0 ..  2012

12.7 ... 1994

12.6 ... average 1659-1700, 2015

12.4 ... 1993

11.3 ... coldest since 1952 and tied 14th coldest (1986)

10.7 ... coldest recent September and sixth coldest (1952)

10.6 ... fifth coldest (1703)

10.5 ... coldest (four tied, 1674,1675,1694,1807)

 6.7 ... coldest days in first half (13th and 14th, 1807)

 4.9 ... coldest day (28th, 1824)

____________________________________________________________________

Enter by the end of Friday, 31 August without penalty, or with increasing late penalties to end of Monday, 3rd September.

============================================================================

(add your EWP forecast if you wish, to the CET entry) ...

... data from 1910 to 2017 from NCIC of UKMO, data from 1766 to 2017 from Hadley. Forecasts are scored on both when they are made available. Averages are NCIC only.

 

186.4 mm __ wettest (NCIC) 1910-2017 in 1918 (this was 189.8 in Hadley)*

141.0 mm __ wettest (NCIC) 1981-2017 in 1981 (this was 139.9 in Hadley)

 74.7 mm __ average (NCIC) 1981-2010

 71.1 mm __ average (NCIC) 1988-2017

 15.4 mm __ driest (NCIC) 1981-2017 in 2014.

 _8.4 mm __ driest (NCIC) 1910-2017 in 1959

 _8.0 mm __ driest (Hadley) 1766-2017 also in 1959**

_________________________________________________

* 1797 and 1799 were almost as wet in the Hadley series at 185.4 mm and 186.8 mm.

** second driest in Hadley series since 1766 was 9.5 mm in 1865.

Enter the EWP contest entries on same deadlines as CET with three-hour extensions so 0300h 1st is the no-penalty cutoff time and 0300h 4th is the absolute cutoff. 

 

 

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The curse of the "Summer Of Hell" continues...  19C  :(  Last sub 11C September in 1952.  Last sub 12C September in 1986.  Last sub 13C September in 2015.  Winter 2018/2019 is over before its even started.

200mm from monsoons and Atlantic garbage.

Edited by Lettucing Gutted

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All one can do at this stage is guess really, but really more of a hopecast for me. 

I will go for 15.0°C, so a mild September, with 127% of the normal sunshine and more high pressure. 

Rain I'll go for 65% of the average.

@Lettucing Gutted Atlantic dominated summer months are generally cooler and cloudier than average..

Edited by CheeseAndOnionCrisps

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In terms of the CET pattern i think a toned down version of this month is likely with a more settled opening third giving way to summer finally ending around the 5th-10th. Unlike this month though as the polar vortex gathers strength and the thermal gradient continues to increase i think that the second half will be less sparing. 

I'll go for an average 14C (though we might sneak under) and though i don't participate in the rainfall competition i do suspect that we get a wetter than average month as the Atlantic kicks into gear. 

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@CheeseAndOnionCrisps  Not all summer and autumn Atlantic months are cold.  In fact some have been warm or very warm.  Examples are September 2002, September 2004, September 2006 and September 2011, August 2000, August 2002 and August 2004, July 2010 and July 2017.  All of these months were dominated by unsettled warm and humid Maritime Tropical Atlantic Systems due to a Warm Zonality jet or the UK being in the eastern side of the Mid-Atlantic Trough.  Even in months were most of the UK is stuck under hot and dry Continental Tropical air, at least northwestern Scotland is often stuck under Maritime Tropical West/Southwesterlies.

Edited by Lettucing Gutted

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3 hours ago, Lettucing Gutted said:

@CheeseAndOnionCrisps  Not all summer and autumn Atlantic months are cold.  In fact some have been warm or very warm.  Examples are September 2002, September 2004, September 2006 and September 2011, August 2000, August 2002 and August 2004, July 2010 and July 2017.  All of these months were dominated by unsettled warm and humid Maritime Tropical Atlantic Systems due to a Warm Zonality jet or the UK being in the eastern side of the Mid-Atlantic Trough.  Even in months were most of the UK is stuck under hot and dry Continental Tropical air, at least northwestern Scotland is often stuck under Maritime Tropical West/Southwesterlies.

Well the good news for you is that September has about a 0% chance of recording an average temperature of 19°C, now or any time in the near future. Any month as far above average as that would need to have a lot of hot southerlies, not coming off the Atlantic but from the Mediterranean at the least. Atlantic months in autumn can be milder than average (usually Oct/Nov though), but SW'ly winds will not cause major heatwaves of the sort you're talking about with these wild guesses. A lot of thunderstorms woud be required to produce the 200mm of rain. Atlantic with frontal systems wouldn't allow for such sustained higher than average heatwave conditions. The only 4 months in history to record a CET of 19+°C did not suffer from "Monsoons and Atlantic garbage".

Edited by CheeseAndOnionCrisps

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14 minutes ago, CheeseAndOnionCrisps said:

Well the good news for you is that September has about a 0% chance of recording an average temperature of 19°C, now or any time in the near future. Any month as far above average as that would need to have a lot of hot southerlies, not coming off the Atlantic but from the Mediterranean at the least. Atlantic months in autumn can be milder than average (usually Oct/Nov though), but SW'ly winds will not cause major heatwaves of the sort you're talking about with these wild guesses. A lot of thunderstorms woud be required to produce the 200mm of rain. Atlantic with frontal systems wouldn't allow for such sustained higher than average heatwave conditions. The only 4 months in history to record a CET of 19+°C did not suffer from "Monsoons and Atlantic garbage".

Yeah, and I thought he was crazy for going for 9°C in December 2015...

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On 21/08/2018 at 12:43, Relativistic said:

Yeah, and I thought he was crazy for going for 9°C in December 2015...

A 19°C September isn't technically impossible, it is exceptionally unlikely - and my point was that it will certainly not have "200mm of Atlantic Monsoons". 

December is a different story entirely - sustained advected tropical maritime winds in December can create very high temperature anomalies compared to what the same synoptics would produce in September. That said, December 2015 was the first such month in 350 years of records. Could be that long before a repeat of the month. The Atlantic's effect in winter is to keep the UK milder than further inland areas, and vice versa in warmer, summer season months, where it has a more moderating effect. This is basic common knowledge. Hence why, as I said, a 19°C September requires a lot of hot southerly winds, not "Atlantic Monsoons".

Edited by Paul

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On 21/08/2018 at 12:48, CheeseAndOnionCrisps said:

A 19°C September isn't technically impossible, it is exceptionally unlikely - and my point was that it will certainly not have "200mm of Atlantic Monsoons". 

December is a different story entirely - sustained advected tropical maritime winds in December can create very high temperature anomalies compared to what the same synoptics would produce in September. That said, December 2015 was the first such month in 350 years of records. Could be that long before a repeat of the month. The Atlantic's effect in winter is to keep the UK milder than further inland areas, and vice versa in warmer, summer season months, where it has a more moderating effect. This is basic common knowledge. Hence why, as I said, a 19°C September requires a lot of hot southerly winds, not "Atlantic Monsoons".

I'm fully aware of what you're saying, so I'm not going to argue with you, other than to say that Craig is not an idiot. His crazy punts have been a custom on this forum for years and you're taking them far too seriously.

Edited by Paul

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LG is the reason I went for median instead of mean for our contest consensus values, just in case he goes to three or four digits.

My early suspicion is that September will be cool and very wet, but I will check in around the 31st with a possibly different idea. 

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I'd say continuing a bit warmer than average but not exceptional. Let's say 14.8 and 67mm.

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6 hours ago, Roger J Smith said:

LG is the reason I went for median instead of mean for our contest consensus values, just in case he goes to three or four digits.

My early suspicion is that September will be cool and very wet, but I will check in around the 31st with a possibly different idea. 

I hope your early suspicion is correct!

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I think I'll go for a relatively cool September in recent times 13.4

Rain fall around 95mm.

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14.9c and 52mm

A fairly dry and warm month, in the end the conditions will either revolve around settled conditions or more zonal set up. 

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Hopefully a very warm September to keep the coldies at bay for another month or 2. It's always a bad sign when they start crawling out of the woodwork again.

Edited by cheese

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