The Warmest September ever recorded?

[West is Best]

We are getting very close to seeing one of the oldest records tumble. The highest recorded CET for September occurred in 1729 at 16.6C. At present, with 36 hours to go, Philip Eden has the CET figure on 16.8C http://www.climate-uk.com/graphs/0609.htm

Philip has commented that his Hadley emulation suggests they are 0.1C higher than him i.e. currently at 16.9C.

After another very mild night last night it now looks to me almost certain that this long-established record is about to fall. In a year of remarkable contrasts, but particularly a summer of warm records falling, this September record is arguably going to be the most remarkable. I think it merits a separate thread (rather than being lost in a routine CET discussion), and no doubt in due course the headline writers on Net-Weather, other fora and the newspapers will pitch in. We don't have to go down the Daily Express 'Winter will be the new summer' route, but even so this is an extraordinary September.

[Dawlish]

We are getting very close to seeing one of the oldest records tumble. The highest recorded CET for September occurred in 1729 at 16.6C. At present, with 36 hours to go, Philip Eden has the CET figure on 16.8C http://www.climate-uk.com/graphs/0609.htm

Philip has commented that his Hadley emulation suggests they are 0.1C higher than him i.e. currently at 16.9C.

After another very mild night last night it now looks to me almost certain that this long-established record is about to fall. In a year of remarkable contrasts, but particularly a summer of warm records falling, this September record is arguably going to be the most remarkable. I think it merits a separate thread (rather than being lost in a routine CET discussion), and no doubt in due course the headline writers on Net-Weather, other fora and the newspapers will pitch in. We don't have to go down the Daily Express 'Winter will be the new summer' route, but even so this is an extraordinary September.

Rats! B)

[Bottesford]

It certainly has been special. No chilly days or nights, trees & flowers still in full bloom, insect infestation, plenty of winter whiners wishing it away... B)

The only real sign of autumn has been the ever shortening days & lowering Sun that is now getting close to eye level for most of the day.

September- the fourth month of summer!

[gobbyash]

Wow, that is impressive.

Thanks for letting me know.

gobbyash

[Weather-history]

Using Philip's Manley series, its going to be the first year ever where 4 months have recorded a CET of 16.0 and greater. Thats a quarter of the year having an average over 16.0C. In 1998, there wasn't even one.

Its going to be the warmest June-Sept and May-Sept period ever recorded. First time that September has been warmer than August since 1985

September 2006 is going be less than a half degree cooler than the warmest June of the 20th Century, 1976 (CET 17.0C)

The last time September was the second warmest month of the year was 1985

[Gray-Wolf]

I think the forming El-Nino and its effects on this years Hurricane tracks can be thanked for some of the overnight mildness and daytime highs as the re-curves do tend to drag up lots of TM air. I take it todays instability/precipitation are a return of Helenes remnants having a second bite at the cherry after circulating around our impressive LP out to the west (ot the WV loop would suggest that the air mass at least has)

[West is Best]

Using Philip's Manley series, its going to be the first year ever where 4 months have recorded a CET of 16.0 and greater. Thats a quarter of the year having an average over 16.0C. In 1998, there wasn't even one.

Its going to be the warmest June-Sept and May-Sept period ever recorded. First time that September has been warmer than August since 1985

September 2006 is going be less than a half degree cooler than the warmest June of the 20th Century, 1976 (CET 17.0C)

The last time September was the second warmest month of the year was 1985

That's a truly amazing batch of stats Kevin ...

[Anti-Mild]

So that's us getting 2 record high months out of 3 which makes August all the more remarkable!

[su rui ke]

At this very late stage, it still looks like it's too close to call as to whether the (Manley) record will be broken or 'only' equalled. What do people think - 16.6 or 16.7 as a final figure? It doesn't look like any other outcome is possible now.

[West is Best]

It doesn't look like any other outcome is possible now.

16.8C?

Last night was very mild again, and temps today are pushing on fast. Tonight may be cooler, but we're in a south-westerly flow still so I just can't see much correction to be honest. You would need an overall CET mean for tonight and tomorrow of around 12C to peg it back to 16.6C - and I just can't see that or anything like it in the charts.

So that's us getting 2 record high months out of 3 which makes August all the more remarkable!

In what way though? August was still average.

[Weather-history]

.

In what way though? August was still average.

I made this point before, that a warm September would increase the oddity of August sandwiched between two well above average months. August itself was nothing out of the ordinary but it looks a right cuckoo in the nest between the July and the September now.

19 Sep 2006, 12:48 PM Post #156

An exceptional September is going to increase the oddity of August 2006, sandwiched between the exceptional July and September. It is going to look a real cuckoo in the nest

It would be interesting to see the synoptics of September 2006 and compare that with July and August 2006.

Edited September 29, 2006 by Mr_Data

[su rui ke]

West, I was going by an earlier GFS run which showed widespread minima of around 10C tonight. Obviously if tonight's minima are lower than last night's, tomorrow's maxima will need to be correspondingly higher to hold the figure steady. Do you think tomorrow is likely to be warm enough for that?

It's sometimes difficult to get a feel for what's happening at this distance, especially when thing's could come down to a few hundredths of a degree!

[Dawlish]

So that's us getting 2 record high months out of 3 which makes August all the more remarkable!

It does, you are right. Perhaps the most remarkable month of the summer was August.

The synoptics of the 3 very warm months should have produced warm months. With those synoptics, they would have produced warm months back in the 1960s, 1880s, 1740s or whenever. They would not have produced quite the kind of warmth that they have in 2006, however; the evidence for that is that in 350 years (ish) of recording, similar synoptics are almost bound to have happened and are almost bound to have produced the warmer months, but never as warm as 2 out of those 3 in the same year.

But August......

August was hugely anomalous. Ok, in the record books, it will not get a mention. In 10 years time, no-one will look back at a CET average of just over 16 and give it any significance whatsoever, but in many ways, August was the most special of all the 4 (definitely 4, Kevin's super stats show that quite clearly) summer months because it should have been far colder than it actually was. With that combination of Northerlies and cyclonicity, the CET for August "should" have been colder. Sandwiched in even an average summer, pre-1985, that combination, ranking 1st out of 134 years (after Philip Eden's excellent analysis, on here) ought, I would suggest, to have produced a CET down in the low 13s; verging on record-breakingly cool for August.

It is hard to come up with a more plausible reason for August ending up above the long-term manley CET average, than the fact that our changed, warmer, climate simply does not allow those kind of CET values in the UK, today.

That bodes ill for the ones forecasting a very cold winter. Even with a combination of good old "cold pooling", blocked high pressure over Scandinavia and Easterlies - the perfect set-up for a very cold winter scenario - my question would be; if GW continues, is it really possible to achieve a winter monthly negative CET again this century? Is it even possible to achieve a winter monthly CET of less than 2.0C this century? Jan 1991 was the last time and lesta_snow (great to have your level of interest and knowledge at your age, attaboy!) may go a lifetime without seeing a single (full) winter month with a CET of <2.0 if this warming trend continues.

Paul

Edited September 29, 2006 by Dawlish

[su rui ke]

Looking at Weatheronline, temperatures are already close to what the GFS suggested today's maxima would be, so perhaps 16.8C is still possible after all! It would be nice to break the record properly and not just scrape in by 0.1C!

Edited September 29, 2006 by su rui ke

[Weather-history]

August was hugely anomalous. Ok, in the record books, it will not get a mention. In 10 years time, no-one will look back at a CET average of just over 16 and give it any significance whatsoever, but in many ways, August was the most special of all the 4 (definitely 4, Kevin's super stats show that quite clearly) summer months because it should have been far colder than it actually was. With that combination of Northerlies and cyclonicity, the CET for August "should" have been colder. Sandwiched in even an average summer, pre-1985, that combination, ranking 1st out of 134 years (after Philip Eden's excellent analysis, on here) ought, I would suggest, to have produced a CET down in the low 13s; verging on record-breakingly cold.

It is hard to come up with a more plausible reason for August ending up above the long-term manley CET average, than the fact that our changed, warmer, climate simply does not allow those kind of CET values in the UK, today.

As I pointed before these are never clear cut.

For instance, August 1950 is the most southerly August in Philip's lists and yet it had a CET of 15.6, it ought to have been "warmer" than it was.

None of the very warm Septembers are in the top 3 most southerly Septembers and yet logic tells you they should be

The second most northerly January is 1981 and yet it had a CET of 4.9

There are other examples

[Dawlish]

Looking at Weatheronline, temperatures are already close to what the GFS suggested today's maxima would be, so perhaps 16.8C is still possible after all! It would be nice to break the record properly and not just scrape in by 0.1C!

Yes, I agree, it would. It is always exciting when a record falls - especially one that has lasted so long! I just hope the record falls properly, on all measures and we don't have the messing about that followed July. Was is, or wasn't it? It wasn't by Manley, it was by Hadley. I hope it stays at 16.8 too, even though it will cost me virtual tipples!

Paul

[Andy Bown]

Thr previous three Septembers I've recorded temperatures have had means of around 15c. As of yesterday morning this month's mean was 16.94c! So almost 2c higher than average .

As in August though, there have been many days with maxxes of 20-22c and mins of 11-14c. Might have to do a split of those numbers again and correlate the two months together.

[Dawlish]

As I pointed before these are never clear cut.

For instance, August 1950 is the most southerly August in Philip's lists and yet it had a CET of 15.6, it ought to have been "warmer" than it was.

None of the very warm Septembers are in the top 3 most southerly Septembers and yet logic tells you they should be

The second most northerly January is 1981 and yet it had a CET of 4.9

There are other examples

hi Kevin,

I know, I understand and good point; but, to be fair, Philip's analysis pointed to a combination of wind direction and cyclonicity, which to which, he applied multiple regression to further his analysis. It wasn't just months with the most Northerly element that he was comparing.

Interesting to speculate though about comparisons to past synoptics; though it is just speculation!

Paul

[Mr Sleet]

hi Kevin,

I know, I understand and good point; but, to be fair, Philip's analysis pointed to a combination of wind direction and cyclonicity, which to which, he applied multiple regression to further his analysis. It wasn't just months with the most Northerly element that he was comparing.

Interesting to speculate though about comparisons to past synoptics; though it is just speculation!

Paul

We've already been there and done that. Just saying it is northerly is not good enough. Where was the source of the air ? How long was the northerly track ?If you look back you can see that the northerly source was not far north at all . With respect to Philip, that analysis is interesting but not too much should be read into it.

Examples :

[Thundery wintry showers]

While it's hard to dispute the notion that a warmer globe means less chance of cold synoptics producing very cold weather, August doesn't necessarily show that significantly below average CETs are impossible. March 2006 had an anomaly of about -3C relative to 1971-2000, and -2 to -2.5C relative to 1961-90, for the period 1-23 March, before the exceptionally mild end shaved a lot off the cold anomaly. In Oslo the month was a good 3-4C below even the 1961-90 average.

Synoptics were not "ideal" for cold weather during the 2005/06 winter quarter either- rather, we tended to have a high over Eastern Scandinavia, cold easterly winds for eastern Europe, and southerlies in the west of Europe.

In August 2006, there was an unusual dominance of northerly and north-westerly winds, but as some others have mentioned, the northerly was rarely from an especially cold source (usually originating over southern Scandinavia, which in itself was about 3C above the long-term normal). That cannot explain all of the discrepancy, but it can explain some of it.

This September has indeed been remarkable for its warmth. I expect the synoptic mean charts to show a strong southerly bias in the mean airflow; the NOAA's "30-day running mean sea level pressure" charts are usually fairly accurate and show a strong anomalous low to the west, and high to the east. Similar to July, though probably more cyclonic.

[Dawlish]

We've already been there and done that. Just saying it is northerly is not good enough. Where was the source of the air ? How long was the northerly track ?If you look back you can see that the northerly source was not far north at all . With respect to Philip, that analysis is interesting but not too much should be read into it.

Examples :

Thought you might say that Mr S, but my thoughts remain the same - there is no way to tell what the sources of other years were. They could be from an even more Southerly source and the analysis effectively takes into account the various northerly sources, by the large (134) dataset.

Paul

[Guest Mike W]

Minor point Dawlish but it's February 1991 at 1.5 which was the last below 2 CEt not January 1991. But I agree with you about Auust but I don't think it would have been a low 13 CET, I think in terms Summer you too knock of 0.7 - 1.2 at least to maybe 2 at the most to get what the CET may have finished at 20+ years ago or even pre clean laws. Just thinking that if we started the clean air laws at tthe start of the 20th the famous winters of 47 and 63 would not have happened or 78/79 or Decembver 81 etc. We would have reached 400ppm CO2 about 20+ years ago easy. I think we may also have had 5 10.** in a row by the 1970's.

[Dawlish]

We should deal with what is in front of us .

Tamara

Nicely written reply Snowp, but, with resepect, you delude yourself. What is in front of us is a Global Warming trend, with no evidence whatsoever that it is likely to end in the foreseeable future and though you would love to think we won't be and somehow we will have colder winters, on the back of the coldest winter for 9 years (wow!),the UK will not be immune.

Paul

[shuggee]

Can we stick to topic please - namely the potentially record breaking September CET. There are plenty of other threads to chop and change your opinions in.

Many thanks.

[West is Best]

West, I was going by an earlier GFS run which showed widespread minima of around 10C tonight. Obviously if tonight's minima are lower than last night's, tomorrow's maxima will need to be correspondingly higher to hold the figure steady. Do you think tomorrow is likely to be warm enough for that?

It's sometimes difficult to get a feel for what's happening at this distance, especially when thing's could come down to a few hundredths of a degree!

I agree with this. However, maxima today are comfortably high enough to hold the figure (I've already seen a 21C). So it'll be down to tonight. Even if the overall CET was 10C tonight we'd need to see maxima of only around 14C for the record to be equalled rather than beaten ... if my calculations are right! I can't see it happening. Even with a potential drop in temps the 850hPa charts don't support a dramatic fall-off tomorrow - in fact temps in the range 18-20C are more than likely.

Although it might be nice to get a 16.8C, 16.7C will still take the record! And given that Hadley is allegedly 0.1C higher than Manley, even if Philip's dropped to 16.6C (unlikely) the record would still fall.