September 2010 Cet

[summer blizzard]

http://hadobs.metoffice.com/hadcet/cet_info_mean.html

CET has risen to 15.6C.

Mr Data will have however the massive drop has been delayed again although I have little faith in projected temps by the GFS as there's been some really odd ones that far out.

The drop begins on the 15th, with a well below average isotherm.

http://www.wetterzentrale.de/pics/Rtavn962.png

[damianslaw]

Could be on course for a month of two very contrasting halves CET wise - with a warm first half cancelled out by a cold second half. Every likelihood the final CET will be very close to the average.

[summer blizzard]

Massive rise yesterday to 15.9C, probably due to the minima on saturday night.

[Optimus Prime]

Yep the year to 11th September is still running below average though (-0.05c) looks like it will turn much cooler next week.

[The PIT]

Interesting Country file forecast temperatures staying around normal by day although cool by night after Wednesday. I just think they're being slightly optimistic over the day time temps. Time will tell.

[Lettucing Gutted]

Interesting Country file forecast temperatures staying around normal by day although cool by night after Wednesday. I just think they're being slightly optimistic over the day time temps. Time will tell.

Indeed there even showing 19-20C in the southern quarter of the UK despite long draw cyclonic Northwesterly winds.

[The watcher]

Well seen as the change comes about on the 15th (my birthday) I shall blow out the candles and wish for a sub 14c month...or 13.5c *cough cough*

[damianslaw]

Interesting Country file forecast temperatures staying around normal by day although cool by night after Wednesday. I just think they're being slightly optimistic over the day time temps. Time will tell.

Often the countryfile forecasts show temps at a higher level than they will be - quite often the BBC downgrades temps closer in the reliable timeframe. Very rarely do the temps they show for Thursday and Friday verify, alas under the predicted north/north westerly airstream later next week I can't see London hitting much more than 18 degrees even if there are good sunny breaks. Also remember the temps are for city and town centres and often don't reflect what will happen in smaller towns and rural areas - something particularly notable when it comes to nightime minima. I often knock one or two degrees off what they show as a more likely figure - indeed there forecasts seem to be based on a london bias, almost to the point that they use the london temp as the base figure on which to predict everywhere else.

I must say though they have improved somewhat in the past year or so, they were especially good during the past winter.

[The PIT]

Often the countryfile forecasts show temps at a higher level than they will be - quite often the BBC downgrades temps closer in the reliable timeframe. Very rarely do the temps they show for Thursday and Friday verify, alas under the predicted north/north westerly airstream later next week I can't see London hitting much more than 18 degrees even if there are good sunny breaks. Also remember the temps are for city and town centres and often don't reflect what will happen in smaller towns and rural areas - something particularly notable when it comes to nightime minima. I often knock one or two degrees off what they show as a more likely figure - indeed there forecasts seem to be based on a london bias, almost to the point that they use the london temp as the base figure on which to predict everywhere else.

I must say though they have improved somewhat in the past year or so, they were especially good during the past winter.

I was looking at the 850's they certainly didn't support 19 - 20 and the GFS highs would be more realistic. However tonight is going to warm so expect a big bump in CET. Mins expected to be around 15C to 16C.

[Stu_London]

I think slight falls for yesterday and today will be offset by a rise tomorrow courtesy of the aforementioned upcoming mild night.

Thereafter, it looks like a plunge. Wednesday to Sunday will all be falling days. Friday and Saturday have potential to be sub 10C days, although I suspect GFS might be underdoing the temps a little bit. Even so, I expect us to be sub 15C by the 19th (GFS 00z actually suggests the period 15th to 19th will average about 10.7C, bringing the CET to 14.5C)

After this date, the latest GFS (which is something a warm outlier) stablises things - the ensemble mean which keeps below average until the end of the month, would probably see us go to sub 14C and maybe slightly beyond.

Autumn and spring months are always difficult to predict as the pace of change can be suprising. Until the period after the 19th comes into focus, it will be difficult to nail down with any confidence a final figure, however I still have a hunch we will be around the 14C mark.

[BornFromTheVoid]

Some surprisingly mild weather the last few days, though I think we could be down to 15.6C before tonights mild temps cause the last upward motion in the CET for the foreseeable future. The CET is already so high I reckon that it will only add on 0.1C.

Will have a better idea by the update today, but I still think we'll be at 15.5C by the time the CET reaches the 15th!

[BornFromTheVoid]

15.7C to the 12th.

http://hadobs.metoffice.com/hadcet/cet_info_mean.html

Yesterday was just 14.3C, lowest of the month so far. Minimum for today is down as 11.3C, and maxima look to be around 18C so a chance of dropping back to 15.6C by tomorrow.

The CET minimum for tonight looks like being just over 15C, so we will probably be at 15.7C by the 14th.

Things then turn very cool with daily CET values dropping back to levels not seen since perhaps May. The GFS 06z would have us at 15.5C by the 15th, 15.0C by the 17th and 14.6C by the 19th.

I'd say at this stage, 14.4C-14.8C by the 20th, and as a very early guess at the final CET, somewhere between 13.5C and 14.5C I reckon!

[Thundery wintry showers]

Often the countryfile forecasts show temps at a higher level than they will be - quite often the BBC downgrades temps closer in the reliable timeframe. Very rarely do the temps they show for Thursday and Friday verify, alas under the predicted north/north westerly airstream later next week I can't see London hitting much more than 18 degrees even if there are good sunny breaks. Also remember the temps are for city and town centres and often don't reflect what will happen in smaller towns and rural areas - something particularly notable when it comes to nightime minima. I often knock one or two degrees off what they show as a more likely figure - indeed there forecasts seem to be based on a london bias, almost to the point that they use the london temp as the base figure on which to predict everywhere else.

I must say though they have improved somewhat in the past year or so, they were especially good during the past winter.

Last winter was rather odd- I agree that the BBC's temperature predictions during that cold spell from 17 December to 15 January were very good, but then when that northerly cropped up on 29-31 January, the Countryfile forecast on the 24th January went back to old habits, giving a northerly for the end of the week accompanied by snow showers and maxima ranging from 5C in Scotland to 8C in south-west England.

I remember many of us commenting at the time that while snow showers and maxima of 5-8C is quite a common combination from spring northerlies, it's a big stretch to get it at the end of January with the sun still being weak at that time of year. It has been known on rare occasions in February (13th February 2005 for example) but nonetheless, it probably won't surprise many people to hear that Cleadon's maxima on those three days were 2.7, 2.2 and 3.5, a good 3C down on what the BBC had forecast.

[reef]

Last winter was rather odd- I agree that the BBC's temperature predictions during that cold spell from 17 December to 15 January were very good, but then when that northerly cropped up on 29-31 January, the Countryfile forecast on the 24th January went back to old habits, giving a northerly for the end of the week accompanied by snow showers and maxima ranging from 5C in Scotland to 8C in south-west England.

I remember many of us commenting at the time that while snow showers and maxima of 5-8C is quite a common combination from spring northerlies, it's a big stretch to get it at the end of January with the sun still being weak at that time of year. It has been known on rare occasions in February (13th February 2005 for example) but nonetheless, it probably won't surprise many people to hear that Cleadon's maxima on those three days were 2.7, 2.2 and 3.5, a good 3C down on what the BBC had forecast.

I remember that well, here a little further south the maxima were 2.8C, 2.2C and 2.2C. A northerly of similar potency also gave a max of just 6.8C on 8th April 2005, with the BBC predicting 11C at the time - that was when the sun was rather stronger too.

[damianslaw]

I remember that well, here a little further south the maxima were 2.8C, 2.2C and 2.2C. A northerly of similar potency also gave a max of just 6.8C on 8th April 2005, with the BBC predicting 11C at the time - that was when the sun was rather stronger too.

In a northerly airflow the BBC always seem to struggle with getting predictions for air temps right. They are still predicting high teen maxima for much of england and wales later this week, in reality expect mid teen temps at best away from the sheltered heat island of London.

One thing to remember is the temps shown are maxima, in northerly airstreams high maxima is often not retained for a lengthy period and under cloud and more especially showers temps often take a tumble. You may only see the maxima for a few short minutes when the rest of the day stays a good one or two degrees below this figure. Maxima temps in northerly airstreams are thus very misleading and as we know at night under clearing skies temperatures really take a tumble.

Back to the CET - increasingly looking like the mild first half will be cancelled out by a cool if not rather cold second half, however, it will be quite a tall order I feel for a below average CET final figure, the mild nights this month have seen to that.

[summer blizzard]

Models are in agreement that the main cool spell will last until the 20th before a return to average temperatures. Should we avoid a mild spell untill the end of the month, a CET outurn between 14.2C and 14.7C is likely in my opinion.

[BornFromTheVoid]

The 18z is quite cool and would have us at about 14.3C by the 21st. Most of the ensembles are cooler still, so the milder spell after the 21st ain't quite guaranteed methinks.

[The PIT]

I expect the CET to be 15.8C up the 13th as it was very mild overnight with the highest temp occurring overnight.

[frostyjoe]

The 18z is quite cool and would have us at about 14.3C by the 21st. Most of the ensembles are cooler still, so the milder spell after the 21st ain't quite guaranteed methinks.

Where do you get this data from? Expecting temps not to get above 12c today as the showers are forming very quickly and look very heavy , would love first (officual) 12c max.

[Gavin P]

ECM and GFS indicate a very warm spell setting up again next week. Pretty much rules out a sub 14c finish. At this rate we'll be lucky to get a sub 15c finish as well.

Don't mid admitting I got the pattern completely wrong for this September. Thought it was going to be cool and wet and its ending up warm and dry.

[Stu_London]

I expect the CET to be 15.8C up the 13th as it was very mild overnight with the highest temp occurring overnight.

Yes but that was on the 14th

CET will be 15.6 or 15.7 to 13th

might get back up to 15.8 on the 14th, but more likely 15.7C

pedantic rant over.....

00z brings a quite mild period in for the last 3rd of the month - If it comes to fruition getting below 14.5C will be difficult

[Milhouse]

the 00z brings Indian summer conditions for a while which would almost return the CET to the current level by the 23rd. However it does seem to be at the extreme end of things. A change to warmer/more unsettled conditions looks likely though early next week after a cool and quiet weekend.

[Stu_London]

the 00z brings Indian summer conditions for a while which would almost return the CET to the current level by the 23rd. However it does seem to be at the extreme end of things. A change to warmer/more unsettled conditions looks likely though early next week after a cool and quiet weekend.

I don't think we will get back to the current level.

Despite the impressive looking 850s, the actual CET for the period 21st to 23rd would probably be no higher than 17C over the 3 days. Assuming we were 14.5 at the 20th, that would only take us back to 14.8C or maybe 14.9C. A cooldown thereafter would still leave the door open for sub 14C (just!).

Anyway it's all conjecture at this point as both the warm up and cool down are very much in the realms of FI

[Thundery wintry showers]

The northerly seems to be downgrading with every run- I noted that 2 and 3 days ago we were looking at four or five cool bright showery days on the trot, and now, it looks like most southern areas will only get one or two such days. It will still be pretty potent, but probably turning warmer already by Sunday or Monday.

[Gavin P]

Whilst the northerly does get cut off by Saturday, I think ECM and MetO keep us pretty cool out to T144, with some particularly cool nights looking likely. GFS is much keener to bring warmer air back over the weekend, but I'd be inclined to go with the Euro's on this one.

CET dropped to 15.6 yesterday;

http://hadobs.metoffice.com/hadcet/cet_info_mean.html

Edited September 14, 2010 by Gavin P