August CET

[Thundersquall]

Has August ever had average nearly 4C colder than July?

[summer blizzard]

According to Phillip Eden, the current CET is 16.5C, which is 0.3C above the monthly average.

As far as i am aware, we need a August CET of 16.1C in order for the biggest July/August CET difference to be achieved.

[Stratos Ferric]

Has August ever had average nearly 4C colder than July?

3.6 is the largest gap, and 0.3 the mean. The standard deviation on the population is 1.2, which puts this year around 3SDs above the mean. If this population had a normal distribution (arguably it cannot be treated as normal, though it might nearly be normal), this would equate to a probability of 0.3% overall, and half this in the positive tail. In layman's terms, the return period for this size of positive gap is around 500 years! Quite exceptional.

[summer blizzard]

3.6 is the largest gap, and 0.3 the mean. The standard deviation on the population is 1.2, which puts this year around 3SDs above the mean. If this population had a normal distribution (arguably it cannot be treated as normal, though it might nearly be normal), this would equate to a probability of 0.3% overall, and half this in the positive tail. In layman's terms, the return period for this size of positive gap is around 500 years! Quite exceptional.

Wow, i did not realise that there was such a large return date.

According to Phillip Eden, the current CET is 16.5C.

I have just been looking at the CET statistics on www.climate-uk.com, and it amazes me that despite the cool weather, the period 15th July to 15th August had a CET of 19.1C.

Mr Data, what is the biggest CET drop from the mid July to Mid August and mid August to mid September period??

[Weather-history]

Mr Data, what is the biggest CET drop from the mid July to Mid August and mid August to mid September period??

You don't ask for much

Mid Jul-mid Aug 1995 to mid Aug-mid Sep 1995 was a big drop between those periods

That period in 1803 was an even bigger drop, I think about 3.6C or around that

Anything above that then it is very close to being probably the record.

[Thundery wintry showers]

Wow, i did not realise that there was such a large return date.

According to Phillip Eden, the current CET is 16.5C.

I have just been looking at the CET statistics on www.climate-uk.com, and it amazes me that despite the cool weather, the period 15th July to 15th August had a CET of 19.1C.

Mr Data, what is the biggest CET drop from the mid July to Mid August and mid August to mid September period??

I think the second half of July 2006 was somewhat hotter than the first, so the first half of August wouldn't have had to be particularly warm to reach a mean of 19.1C.

[Tom D]

at this late stage in the month, i think the CET is gonna be 15.8

[Stratos Ferric]

at this late stage in the month, i think the CET is gonna be 15.8

Unless you're aware of an asteroid about to slam into us I suggest you need to go and check your maths! Once we're within five days of the end of any month the average for the month as a whole is rarely going to change by more than 0.1 or 0.2C. A drop of 0.7C from now, as you're suggesting, would require every day to come in at around 12C; with maxima around 18-20 that would require minima around 6-4C. It's not going to happen! I still suspect my projection earlier in the week is on the mark, and the higher end of the range at that in all probability.

[Weather-history]

Interestingly, the last 20 days (11th-30th August) have averaged slightly below the 1971-2000 average

http://www.climate-uk.com/page2.html

Its going to be one of the biggest collapses in terms of sunshine and CET between July and August on record.

Manchester average maximum

July 25.5C

Aug 19.1C (up to 30th)

Average mean

July: 19.64C

Aug: 15.8C

Edited August 31, 2006 by Mr_Data

[Michael Fishermans Friend]

According to Phillip Eden, the current CET is 16.5C, which is 0.3C above the monthly average.

As far as i am aware, we need a August CET of 16.1C in order for the biggest July/August CET difference to be achieved.

It really still is a struggle to get a month with a noteably colder than average CET! despite all the unsettled conditions. Alot of the talk recently is about what a difference there has been between July and August temps wise, but is this really a surprise considering just how hot July was? It would be far more of an eye opener if we were to have a near normal CET month followed by one with a considerably lower CET. I know this has been asked before but are we capable of getting a cold month??

[Bham Chris]

It really still is a struggle to get a month with a noteably colder than average CET! despite all the unsettled conditions. Alot of the talk recently is about what a difference there has been between July and August temps wise, but is this really a surprise considering just how hot July was? It would be far more of an eye opener if we were to have a near normal CET month followed by one with a considerably lower CET. I know this has been asked before but are we capable of getting a cold month??

My answer is that is unlikely at the moment but remember back to March and it was set to be a well below average month but was spoiled by the warmer last week so we're not incapable.

[summer blizzard]

Phillip Eden has the monthly CET at 16.3C, which is 0.1C above average, however last year, he had the CET as 16.4C and the Hadley CET was 16.2C, therefore we should expect the Hadley CET to be slightly below average.

[Weather-history]

Alot of the talk recently is about what a difference there has been between July and August temps wise, but is this really a surprise considering just how hot July was?

Actually it was, it is unusual for August to be at odds with other two summer months

Only 4 other summers where a warm June and a warm July (both above at least by 1.0C the 1971-2000 average) were followed by an August that was not much above the (1971-2000 average).

1733, 1762, 1794, 1818

Edited September 1, 2006 by Mr_Data

[Anti-Mild]

It really still is a struggle to get a month with a noteably colder than average CET! despite all the unsettled conditions. Alot of the talk recently is about what a difference there has been between July and August temps wise, but is this really a surprise considering just how hot July was? It would be far more of an eye opener if we were to have a near normal CET month followed by one with a considerably lower CET. I know this has been asked before but are we capable of getting a cold month??

I reckon if July hadn't been so hot then this August may well have been in the mid to low 15c bracket in terms of CET. All the hot air pumped Northwards throughout the early part of the summer will have modified our temperatures in August.

[Michael Fishermans Friend]

Actually it was, it is unusual for August to be at odds with other two summer months

Only 4 other summers where a warm June and a warm July (both above at least by 1.0C the 1971-2000 average) were followed by an August that was not much above the (1971-2000 average).

1733, 1762, 1794, 1818

Yes while that might be a note worthy point, it doesn't really equate to anything - surely there are many permutations waiting to be broken. Although were there any patterns with the fore-mentioned summers??

[Stratos Ferric]

Actually it was, it is unusual for August to be at odds with other two summer months

Only 4 other summers where a warm June and a warm July (both above at least by 1.0C the 1971-2000 average) were followed by an August that was not much above the (1971-2000 average).

1733, 1762, 1794, 1818

Before Daniel doesn't spot it, I shall say that this is all the proof that we need to show that our climate has suddenly lurched back to that of the end of the little ice age. A winter of armageddon, as desribed by Sian Lloyd the other evening, is looming.

I reckon if July hadn't been so hot then this August may well have been in the mid to low 15c bracket in terms of CET. All the hot air pumped Northwards throughout the early part of the summer will have modified our temperatures in August.

That's a bit like saying that if my mother had married my uncle not my Dad my dad would be my uncle. She didn't! At the end of the day the statistics go in the book as a record of what happened, not what might have happened had circumstances been completely different. You might equally say that had July's warmth continued then this summer would have been the hottest ever. It didn't, it wasn't.

[Weather-history]

Yes while that might be a note worthy point, it doesn't really equate to anything - surely there are many permutations waiting to be broken. Although were there any patterns with the fore-mentioned summers??

Well one odd thing, is that 3 of those 4 summers were preceded by an April that recorded a CET of 10 or more and there are only 17 Aprils that have recorded a CET of 10 or more.

[Stratos Ferric]

Well one odd thing, is that 3 of those 4 summers were preceded by an April that recorded a CET of 10 or more and there are only 17 Aprils that have recorded a CET of 10 or more.

At this rate we'll be finding hidden codes, prophecying doomsday, hidden in the CET series before much longer.

[Guest Mike W]

It a very small point but using the Manley series 16.3 is average on the 71 -00 average [Manley average], yet on the Climate UK site it stated as being 0.1 above the 71-00, is this becasue it's using the Hadley 30 year average. I may have August wrong, but I'm pretty cetain that it's 16.3, I know tht it 16.2 on the Hadley you see, this why I confused. Jan: 4.2, Feb: 4.3, Mar: 6.2, Apr: 8.1, May: 11.4, Jun: 14.1, Aug: 16.5, Aug: 16.3, Sep: 13.7, Oct: 10.4, Nov: 6.9, Dec: 5.0, Annual: 9.76

Edited September 1, 2006 by Mike W

[Dawlish]

Mmmm, there's been a few posts like this recently, leading to some spectacularly early ramping about sudden cooling, a cold winter ahead etc. etc. It's interesting, given that even you are acknowledging that August is going to turn out around average, that people are spotting a sudden cooling, rather than a view that things are simply returning to normal. Yes, things are cooler than they were in July, but then July WAS the hottest month on record.

I uncork it time and over, but the first tutor I ever had at college was one of the preminent climatologists not just in the UK, but in the world, and I vaguely recall asking him in one early tutorial what he made of a recent run of weather. He smiled and simply said "well, what I always say is that things average out in the end". Whilst being a statement of the bleeding obvious, it's a telling point that we sometimes overlook; a sustained run of weather (say more than a month) of any type is highly unusual in these parts, be that blocked or mobile. Furthermore, after a sustained run outside of average, there usually follows a correction later - witness recent rainfall after a long dry period.

Well said SF, but corrections are only likely to occur if the underlying variables remain constant. In the case of UK climate since 1985(ish) a forcing variable has moved the goalposts.

The really amazing thing about this August has been the fact that it has ended up above the Manley CET despite some cool synoptics, the like of which have not been seen in the UK August climate for well over 100 years. In other words, given the combination of a marked northerly element to August's weather and marked cyclonicity, this August ought to have been much cooler than it was.

I post this as a bit of a farewell on here, but thanks very much for the PMs welcoming me back! This is copied from a post of mine on UKww, commenting on an excellent article by Philip Eden on there.

"We know, through Philip's work with multiple regression of the two variables, that this August's CET, produced by that combination of Northerlies and cyclonicity is the most exceptional ever (It ranks 1 of 134). We also know that a hindcast of the two would produce a mean CET of 14.4C, based on all the Augusts he has included in his study (134 years). From this, we can see that there is only a 1 in 200 chance (approx) of this happening by chance in any one winter (16.5C being about 2.6S from the mean). Thus, with a 99.5% certainty, we can say that this CET would not normally happen with these synoptics, today, or in the past. I chose "30+ years ago" as this was before the establishment of a warming trend in the UK, so yes; I believe, with a 99.5% accuracy, we can say that this would not have happened, 30+ years ago, given the synoptics we have had this August.

The debate and our thoughts should be as to why - I really do think the maths speak for themselves - and I don't blame Philip at all for not commenting on what forced this exceptional difference from the CET that might have been expected, given those synoptics. I'll stick my neck out and propose that these Northerly airstreams are now warmer than we have ever been used to in Britain, as the Arctic and the seas over which they pass are warmer than we have known for well over a century, at least. It is changing our winter climate and it is changing our summer climate. Dead interesting it is too - as is the stats!

The other think that I would extrapolate from this is that it is much more likely to happen again, than at any time in the recorded past, if we accept that our climate has been changed by GW."

This August really has been unusual - not just in the change from July, but in the fact that the change from July was not even more marked!

Paul

[Guest Mike W]

The thing is, is that 16.3 is average on the Manley whereas 16.2 is average on the Hadley. But Phillip Eden will need to confirm this as it he who is continuing the Manley series and thank goodness someone is. It would be great to see him put the Manley 30 year average on his site for 71-00 and possbily even 61-90. The reason I ask is min and max Hadley version on his CET tracker instead of the Manley version.

Edited September 1, 2006 by Mike W

[Stratos Ferric]

I have to say that I think that that is one of the most fantastic pieces I've seen posted on N-w ever Hats of to PE for the analysis. My reading at a scan is essentially that in other times August's synoptics would have produced a far lower CET. Let's assume Philip's analysis stands up to scrutiny (my only muse would be, and this goes back to the point I was making earlier to Noggin, that this month to me has been more westerly than northerly, but in this regard I know and trust Philip's method for "measuring" this, and it is robust) then what we have here is another example of a point TWS and I have repeatedly pondered on, i.e. air masses are getting warmer.

If this is the case then the argument we occasionally toss about on here during winter near misses / winters generally viz: "if the synoptics had been right it would have been colder" is eroded even further. The hypothesis is starting to emerge clearly at the horizon, if not yet over it, that the baseline has shifted; it's not synoptics that matter if there's too much air-mass modification going on.

Your last line is bang on the money, and reminds of precisely the same comment I made last winter and the one before; not that it had been cold when it was, but that it wasn't as cold as it ought to have been at those time. But perhaps that's me being selective in my observations.

Cracking analysis nonetheless.

Edited September 1, 2006 by Stratos Ferric

[Michael Fishermans Friend]

Dawlish I think your post is spot on! - alot of people should take note of the points you have made.

[MP-R]

Mine is 18.5C

[Thundery wintry showers]

One issue with this August, which was clear from scrutiny of the 850hPa temperatures, is that much of Scandinavia was unusually warm, and that during the second week in particular our northerlies were sucking warmer air in from Scandinavia (a typical summer northerly would produce 850hPa values of around 2 to 5C, with the 0C line penetrating towards northern Scotland, but in this case we kept getting pulses of 10C air spreading south in the northerly flow).

This cannot be explained entirely synoptically, as what usually happens is that even if Scandinavia is anomalously warm, you get cold air from around 75N (around or below 0C at the 850hPa level) mixing with the warmer air over Scandinavia, and bringing 850hPa values no higher than 5C southwards. The key is that while the pole was if anything slightly cooler than normal, those "greens" (850hPa values below 0C) have been further north than usual- so we needed a longer drag northerly than usual to bring in the sub-0C air to mix with the 10C air.

It may sound complicated, so I will provide a comparison between the August 2006 northerlies and a more "normal" summer northerly.

http://www.wetterzentrale.de/archive/2006/...00220060802.png

http://www.wetterzentrale.de/archive/2000/...00220000710.png

Notice the greater amount of "green" at relatively southerly latitudes in the latter case.