This thread is for all comments, discussion, and analysis of temperatures in the UK during August, with particular emphasis on the Central England Temperature (CET), for the simple reason that it is the longest-running temperature series in the world with over 360 years of data. But you can comment on any interesting temperature statistics or data from across the UK, including your own backyard.  

For those taking part in the competition, all CET predictions for August should be sent directly to me via the forum private message system. Please do not post them directly into the thread.   

Historic CET summary for August

1981-2010 (30 years) 16.41C

1991-2020 (30 years) 16.52C 

2001-2020 (last 20 years) 16.47C 

Last year August was very warm at 17.9C. Warmest since 2003. The coldest August in recent times was 2014 with just 14.9C.

Here is a chart of the August CET for all years since 1961  

Direct link to a larger version of the chart

Current model output     

The first 10 days look very cool. After that maybe something warmer but a lot of scatter and the ENS mean is only giving average T2m temperatures.

GEFS

https://www.wetterzentrale.de/de/show_diagrams.php?geoid=49069&model=gfs&var=2&run=99&lid=ENS&bw=

https://www.wetterzentrale.de/de/show_diagrams.php?geoid=49069&model=gfs&var=5&run=99&lid=ENS&bw=

ECM (de Bilt) looks similar with maybe something warmer by the end of week 2.

http://www.knmi.nl/exp/pluim/Data/PLUIM_06260_NWT.png

Met Office contingency planners outlook  

https://www.metoffice.gov.uk/binaries/content/assets/metofficegovuk/pdf/business/public-sector/civil-contingency/3moutlook-aso-v1.pdf

Very strong signal for a hot month (50% probability) with 45% chance of something nearer average. Given the first 10 days of the month looks like being below average, if we do end up with a hot month, the second two-thirds would need to be very hot indeed. Interesting! Also increased likelihood of thunderstorms, presumably due to the hot conditions. Summer may just be on pause.

Thank You, GW My choice is in.

No Met Office Hadley  figure until Tuesday

Metcheck        14.0c     Anomaly     -2.03c

Netweather     15.72c   Anomaly     -0.48c

Peasedown St John  13.78c  Anomaly  -2.52c. 

Not off to a steamy start: 15.8C provisional to 1st (-0.2C). 

No doubt it's lower than that, and it's cooler today.

Bit of an awkward time for the models at the moment. EPS have slowly been increasing support for a noteworthy warm and dry spell mid-month but with with more of a southern UK focus than July's 'main event'.

Yet we've yet to see an ECM run really go for it, while GFS, having been so keen up until yesterday's 12z run, has really gone off it since.

EPS still have a lot of scatter, something which given my CET estimate low confidence this month. I dared to go for an above-average month despite the cool opening week or so, due to a combination of the trend noted above, GFS' sheer persistence at the time (how classic that it's had a change of heart since!), and the Met Office supporting the general idea as part of a generally warm or very warm second half to the month.

Longer-term, the ensembles are even more scattered. Everything from a heatwave to unseasonably cool & unsettled again is represented:

If I was making the CET estimate this evening, it would be closer to the long-term average, due to the lack of continued trend in favour of the warmer outcome persisting beyond the 2nd half of next week.

This uncertainty can be traced back to a 'mini-cycle' of big tropical thunderstorm activity in the Pacific Ocean conflicting with a general drift into a setup befitting of a La Nina event (which is expected to become fully established during the autumn). The models can't figure out how much the former will temporarily (for a week or two) override the latter, so to speak.

Met Office Hadley      15.05c        Anomaly       -0.5c provisional to 2nd

Metcheck                   14.07          Anomaly      2.16c

Netweather                15.55c        Anomaly       0.65c

Peasedown St John   13.64c       Anomaly       -2.66c.  

If this August manages a simple 16C it will extend the already longest run of consecutive 16+ summer CETs in the entire CET record. 2016-20 has already beaten the runners up (2003-6 and 1778-81, the latter being slightly lacking in having no 17C seasons in that run).

We just need that warm spell to materialise across England at least.

Forecast models continue to be very inconsistent regarding the mid-month period. Pretty much 50/50 between warm and near-average scenarios in the EPS for example, sadly only about half the warm ones are mainly dry as well.

Longer-term, they've started to explore the possibility that the MJO propagates east across Indonesia during the 2nd half of this month. If that occurred, it would mimic what happened in the middle of July and give the weather pattern a far more concerted push in favour of a very warm or hot, settled spell of weather, probably taking shape by the final week of the month.

So, for those who like me have gone at least 0.5°C above average, this may be a case of looking for the CET to head in the opposite direction to the norm during the 2nd half of the month (i.e. up rather than down), unless mid-month turns out very warm or hot after all.

Met Office Hadley          15.4c       Anomaly       -0.7c provisional to 3rd

Metcheck                       14.35c     Anomaly       -1.87c

Netweather                    15.57c     Anomaly       -0.63c

Peasedown St John      14.08c     Anomaly       -2.22c.     

Forecast models continue to be very inconsistent regarding the mid-month period. Pretty much 50/50 between warm and near-average scenarios in the EPS for example, sadly only about half the warm ones are mainly dry as well.

Longer-term, they've started to explore the possibility that the MJO propagates east across Indonesia during the 2nd half of this month. If that occurred, it would mimic what happened in the middle of July and give the weather pattern a far more concerted push in favour of a very warm or hot, settled spell of weather, probably taking shape by the final week of the month.

So, for those who like me have gone at least 0.5°C above average, this may be a case of looking for the CET to head in the opposite direction to the norm during the 2nd half of the month (i.e. up rather than down), unless mid-month turns out very warm or hot after all.

When I looked at the models about 2 hours after submitting my prediction, I felt I'd gone too high. Importantly, night temperatures have dropped considerably now which can sometimes be a bigger influence on the CET than warm days. I think the westerly bias of the CET locations will also favour a below average CET this month. Wish I'd realised that on July 31st!  

 

When I looked at the models about 2 hours after submitting my prediction, I felt I'd gone too high. Importantly, night temperatures have dropped considerably now which can sometimes be a bigger influence on the CET than warm days. I think the westerly bias of the CET locations will also favour a below average CET this month. Wish I'd realised that on July 31st!  

I don’t know what you’ve gone for but my thinking is around average by mid month and a warm second half. Perhaps hot at times. So best wait see what develops before too much hand-wringing?

I decided to have a bit of a risky punt this month and go for a reasonably below average month.

So far, it's actually not looking too bad as the average day time temps have been coupled with some cool nights. The real test will be how warm it gets for the middle third of the month and whether there's a sustained improvement temps wise or a cooler last third. The 12z GFS op would be interesting in that regard with the cool plunge towards the end probably leading to some notably cold nights and that'd really help to offset the warmer interlude.

The ECM ens IMBY were, as SC mentions above, split longer term so some encouragement there for me too.

Given my lowly table position even if I luck out with my guess this month it's not going to do too much for me

When I looked at the models about 2 hours after submitting my prediction, I felt I'd gone too high. Importantly, night temperatures have dropped considerably now which can sometimes be a bigger influence on the CET than warm days. I think the westerly bias of the CET locations will also favour a below average CET this month. Wish I'd realised that on July 31st!  

Yes the drop of night temps was annoying, usually GFS is a bit on the low side but the opening days of this month have proven a rare exception.

Milder nights starting with the next one, though. Not all that cool by day either, so things could be worse.

Next week and beyond remains near evenly split in the model guidance, as Hippydave has noted. Maybe the slightest of shifts in favour of a warm outcome by the 12z suite - but that trend will need to continue tomorrow for any confidence to be gained.

Overall, the middle third of August is proving to be one of the least predictable periods of weather I can recall!

In fact, with MJO projections continuing to trend toward it propagating readily toward Indonesia, I daresay a warmer second half than first may soon become a higher confidence prediction than what happens next week... just need to resolve whether there's any stalling over the Indian Ocean first, which would raise the likelihood of week 3 of August instead seeing a cool spell of some sort before it warms up (potentially a lot) in the final week.

Met Office Hadley        15.7c       Anomaly     -0.4c provisional to 5th

Metcheck                     15.14c     Anomaly     -1.98c

Netweather                   16.0c      Anomaly     -0.21c

Peasedown St john      14.96c    Anomaly      -1.15c.

Met Office Hadley        16.0c      Anomaly      -0.1c provisional to 6th

Metcheck                     15.23c    Anomaly      -0.99c

Netweather                  15.14c    Anomaly      -0.06c

Peasedown St John     15.8c     Anomaly      -1.0c.     

Met Office Hadley      16.0c      Anomaly     0.0c. provisional to 7th

Metcheck                   15.39c    Anomaly     -0.95c

Netweather                16.8c      Anomaly     -0.12c

Peasedown St John    15.01c    Anomaly    -1.29c.  

Here is the latest tracker for August. A cold first 9 nine days but then temperatures then return to around average. That said, it is largely minimum temperatures that keep the CET up. Maximum temperatures remain disappointing.

Chart 1

Chart 2

Here are the predictions for August

Table 1

Interesting spread.

FI continues to be all over the place, so it really is up in the air how the second half of August will pan out.

But at this point I'd rather be where I punted at than where Duncan McAlister is at.

Unfortunately.