October 2007 CET

[Stu_London]

Well we shall see. We're not even half way through the month yet and a marked cooldown is about to start. Ironically the less potency behind the northerly is likely to cause the CET to drop further if only because the high is now projected over us for several days. We're going to see some sharply cool minima, and much lower maxima. From Tuesday onwards the CET is likely to plummet.

It's worth bearing in mind that entire Octobers have come in the 7's and 8's before now, so estimating a drop from 13C to 10C between first and second half end is not as outlandish as it may seem - it's more than possible and depends, bien sur, on the synoptics. At the moment I don't know about the final week, but I do think a second northerly incursion is possible. The kind being shown on the 0z is just a FI tease, but you never know. I would put the odds of getting to average at around 10%, but I might sharply revise those odds upwards.

Don't forget Richard that the probability can rise as clarity improves and the outlook comes into focus. This week could be interesting as we should have falling days from Wednesday to Sunday. At the moment people are talking about temps being around 15C, however I would be amazed if the CET area averaged more than about 11 or 12 on those days. Coupled with nights between 0 and 3 then a drop of similar proportions to that seen in the third week of September is entirely possible. Add uncertainties about fog and the effect on maxima and we could be almost back to average 7 days from now.

The 0z northerly is interesting as it is the first run including any of the ensembles to bring -10hpa air across mainland UK this season - therefore likely to be an outlier.

[Stu_London]

The 0z northerly is interesting as it is the first run including any of the ensembles to bring -10hpa air across mainland UK this season - therefore likely to be an outlier.

However if it did verify then the last 4 days of the month would have a CET of 7.5, 3.5, 3.5, 4.5. If we were stood at 11.5C on the 27th, that would translate to 10.6C by the month end.

Not saying it will happen, but it does leave the door open to an average month, just.

[The PIT]

We should see a drop and as ever the clue will be whether the skies clear or not. Recent years cloud has tended to build in preventing the overnight temps from falling away. Hopefully that trend has stopped for a while.

[Kentish Man]

Hadley shows another slight rise today taking the CET to 12.8C (Oct 1 -14) which is 1.1C above the rolling mean.

Edited October 15, 2007 by Kentish Man

[Terminal Moraine]

However if it did verify then the last 4 days of the month would have a CET of 7.5, 3.5, 3.5, 4.5. If we were stood at 11.5C on the 27th, that would translate to 10.6C by the month end.

Not saying it will happen, but it does leave the door open to an average month, just.

My word I do hope so. I'm beginning to suffer the slightest frisson of doubt that my punt of 10.6c will be rather on the low side by the end of the month. All is not yet lost by any means and I remain cautiously optimistic.

T.M

[The PIT]

My word I do hope so. I'm beginning to suffer the slightest frisson of doubt that my punt of 10.6c will be rather on the low side by the end of the month. All is not yet lost by any means and I remain cautiously optimistic.

T.M

Nah it'll be 11.5C

[Stratos Ferric]

...It's worth bearing in mind that entire Octobers have come in the 7's and 8's before now, so estimating a drop from 13C to 10C between first and second half end is not as outlandish as it may seem - it's more than possible and depends, bien sur, on the synoptics. ...

I think we've taken the latter into account though WiB. For all intents and purposes H2 needs to come in at 7C to get below 10 overall.

It might have happened before across entire months, but I suspect somebody called George was on the throne at the time.

[West is Best]

I think we've taken the latter into account though WiB. For all intents and purposes H2 needs to come in at 7C to get below 10 overall.

It might have happened before across entire months, but I suspect somebody called George was on the throne at the time.

7's for the whole month as recently as 1992 and 1974.

Unlikely, I grant you, but to think the cooler second half couldn't tuck in a 7C would be way wide of the mark. Would be interesting to know how often something below 8C has been recorded for the final 2 weeks since 1900.

[Stratos Ferric]

... Coupled with nights between 0 and 3 then a drop of similar proportions to that seen in the third week of September is entirely possible. Add uncertainties about fog and the effect on maxima and we could be almost back to average 7 days from now.

...

Depends what we mean by 'almost' I guess, but to get down to running mean in a week's time would need daily averages below about 6 between now and then; one or two days might just about nudge that, but several - tomorrow included - are a lot warmer.

I suspect that GFS is underplaying the daytime maxes; we shall see.

Overall runs look slightly cooler than the w/e projections, but they've been bouncing around a lot recently.

[Stu_London]

Depends what we mean by 'almost' I guess, but to get down to running mean in a week's time would need daily averages below about 6 between now and then; one or two days might just about nudge that, but several - tomorrow included - are a lot warmer.

I suspect that GFS is underplaying the daytime maxes; we shall see.

Overall runs look slightly cooler than the w/e projections, but they've been bouncing around a lot recently.

I suspect its the maxes that will be the deciding factor.

[eddie]

7's for the whole month as recently as 1992 and 1974.

Unlikely, I grant you, but to think the cooler second half couldn't tuck in a 7C would be way wide of the mark. Would be interesting to know how often something below 8C has been recorded for the final 2 weeks since 1900.

Less than 8C for the 2nd half of October has been recorded 19 times since 1900 but, and it's a big but, only 2 times in cases where the first half of the month has been warmer than 12.5C (1916 and 1920).

Since 1900 we have never got below 10.4C from a first half CET > 12.5C.

[Stratos Ferric]

Less than 8C for the 2nd half of October has been recorded 19 times since 1900 but, and it's a big but, only 2 times in cases where the first half of the month has been warmer than 12.5C (1916 and 1920).

Since 1900 we have never got below 10.4C from a first half CET > 12.5C.

Good data Eddie.

I think tonight's GFS is the most plausible looking run we've seen for a while; it has the typical sort of progression we've come to expect nowadays. Cold air held slightly north or pushed E; HP close to the S. Certainly if that came off I think 11-11.5 would still look a good bet, perhaps higher - back to cloudy, breezy nights!

[Osbourne One-Nil]

Looks like I'm going to be close, assuming we all agree to use just my records, because halfway through the month, Great Asby's average temperature stands at 10.9c. But this is against a 10yr average of 8.0c and a low in 2003 of 6.7c. I don't remember that being a particularly cold October, but I guess it must have been.

[Weather-history]

Less than 8C for the 2nd half of October has been recorded 19 times since 1900 but, and it's a big but, only 2 times in cases where the first half of the month has been warmer than 12.5C (1916 and 1920).

Since 1900 we have never got below 10.4C from a first half CET > 12.5C.

One October that just misses it is October 1926

First half: 12.4

Second half: 4.0

[reef]

Second half: 4.0

Thats some quite amazing cold for the second half of October. Many winter months in recent years have failed to match that. From the archive charts it looks like the Greenland high was in residence for the entire period, bringing northerlies and heavy snow on the back of southerly tracking depressions. All very tasty.

From Trevor Harley's site:

A cold month overall (CET 8.1C). The month started off nice and warm (23.5C at Worksop on the 4th), with a thundery breakdown on the 5-6th. It was then wet and windy. The month turned much colder from the 14th with frosts, and snow fell almost daily from the 19th. There was sleet on the 21st as far south as the Isle of Wight. Gales and heavy ran on the 24-25th; about 125 mm of rain near Keswick. Further snow on the 28th gave 5cm in London (Hampstead). At Harrogate there was morning snow cover for three consecutive days. Snow was a foot deep at Dalnaspidal near Perth on the 28th. It was -10.5C at Braemar on the 27th, and snow eventually reached a depth of 30 cm over the Perthshire hills. Apparently the severe weather was blamed on the sun: either on the auroral display of the 14-15th, or on sunspot activity.

[Roger J Smith]

Mr Data, close enough there I think, that must have been a nasty shock with no coal available perhaps (don't remember the exact details of that strike, it was during my younger days) ...

By the way, I spy with Eye in the Sky, something beginning with e.

[West is Best]

One October that just misses it is October 1926

First half: 12.4

Second half: 4.0

Blimey!!! :o Great data Kevin, although surely that does make the overall below 10.4C? That would have made the overall figure c. 8.2C, which is well below average.

Interesting to see the Hadobs CET drop already - I'd expected another day before that happened. 12.8C at the midpoint, always bearing in mind that's a provisional figure.

[Stu_London]

Blimey!!! :o Great data Kevin, although surely that does make the overall below 10.4C? That would have made the overall figure c. 8.2C, which is well below average.

Interesting to see the Hadobs CET drop already - I'd expected another day before that happened. 12.8C at the midpoint, always bearing in mind that's a provisional figure.

If the last few months are anything to go by then we magically lose between 0.1C-0.3C on the last day from the provisional.

It's a shame the models are a bit all over the place, I was rather hopeful that you might call below average (only so you could go into battle with SF - that was most entertaining last month!)

[West is Best]

It's a shame the models are a bit all over the place, I was rather hopeful that you might call below average (only so you could go into battle with SF - that was most entertaining last month!)

LOL! I know. I don't dare Stu. They just don't look convincing enough. Mind you, could see a really big tail off for a week or so. That final week is key to whether we get into the 10's ...

[Stu_London]

LOL! I know. I don't dare Stu. They just don't look convincing enough. Mind you, could see a really big tail off for a week or so. That final week is key to whether we get into the 10's ...

The ensembles have got progressively cooler as this week has gone on. There is no, above average period after this weeks drop is done with (and ground temps are likely to be supressed anyway), then there is a big falloff after the 23rd with a below average outrun right to the end.

I will update my projected outrun tomorrow night based on tomorrows 12z output but unless there is a turnaround I can see a 10.? being the prediction.

[Stratos Ferric]

Blimey!!! :o Great data Kevin, although surely that does make the overall below 10.4C? That would have made the overall figure c. 8.2C, which is well below average.

Interesting to see the Hadobs CET drop already - I'd expected another day before that happened. 12.8C at the midpoint, always bearing in mind that's a provisional figure.

Not like you to get ahead of yourself WiB. The page I'm looking at for Hadley is still only reporting to Sunday: Monday's likely rise isn't factored in yet!

Why are we getting excited about data from 1451, or whenever? That's as far away from today's climate as is the climate of Venus.

LOL! I know. I don't dare Stu. They just don't look convincing enough. Mind you, could see a really big tail off for a week or so. That final week is key to whether we get into the 10's ...

WiB, I will eat you if those charts are anywhere near outturn reality. The models persist in looking for cold, which is a continuation of the occasional autumnal flirt to date, and there might be something in the trend, but I don't buy that detail.

[Optimus Prime]

The period 17th-22nd does looks very cool indeed with a mean temperature of 7.6c. By the 22nd the CET should be around 11.5c (only 0.9c above normal)

It does look as if the current trend is a continuing cool one, very autumnal. At this stage I would expect the CET to finish around 10.5c.

Does look like it's quite similar to October 1987 in being the first half was about as warm as this one, but much colder second. That Octobers finished on a chilly 9.7c

[SP1986]

Yes but what does that tell you about modern day climate: That while you can get cold spells the months still stay above average (even if only by 0.1C)

I think theres more for people to be pessimistic about than optimistic, looking at it in that way.

[West is Best]

The models persist in looking for cold,

I'm sure I saw you once chastise someone for hypostasising weather charts SF? :o

If they are 'looking' for cold, it's probably because the patterns are unusual I think, at least relatively so to recent years.

OP's bid for a 10.5C outturn is bold indeed, but by no means out of the realms of possibility.

[Stu_London]

Yes but what does that tell you about modern day climate: That while you can get cold spells the months still stay above average (even if only by 0.1C)

I think theres more for people to be pessimistic about than optimistic, looking at it in that way.

I think the summer just gone proved we can still have below average months - whether that is likely to be replicated over this autumn/winter is a matter of debate and opinion