Annual Cet - 2010

[Thundery wintry showers]

Very interesting stats, thanks for those!

The largest correlations are for Feb-Mar and Jul-Aug. The Jul-Aug one doesn't surprise me, reflecting the tendency for patterns to "lock in" during July and then persist for much of the rest of the summer. But Feb-Mar does come as a surprise- clearly, weather patterns that "lock in" during February also have an above average tendency to continue into March.

[Weather-history]

APR to MAY .106

. However, April to May has much less persistence than any other adjacent monthly sets, which suggests it is the prime time of the year for regime change to occur. .

Something that always struck me how often a really cool April was then followed by a warm May giving as much as 7C difference between the two for the CET.

[kold weather]

Looking increasingly probable that March will come in below average, which will obviously help to further increase the anomalies needed by the other months. Starting to look likely we will have to get some very impressive warmth in the second half to get even close to the 10 year average of the CET, and it seems we have a real shot at going decently sub 10C...

[Stu_London]

CET 07/03/09-06/03/10 - 9.84C

If March comes in at 6C, April at 8C and May at 11C (all around average) the CET in running will be 9.52C by end of May.

The rolling CET has dipped a bit more

CET 12/03/09-11/03/10 - 9.78C

Cant remember what the rolling CET got down to last year - we must be getting quite close I would think.

[Stu_London]

Just worked it out

Rolling CET 15/02/08-14/02/09 - 9.47C

Gives us something to aim at!

[kold weather]

Well the last 20 days of March were fairly mild so we should continue to shave off little bits of the rolling CET in the next few weeks unless things do become much milder and that should continue into April hopefully to some extent. I'm guessing we won't be far off.

However our greatest shot may well come in the Autumn, esp given the decently above October and the very above November, get either of those months below average (esp November) and it'd probably do the job unless we have a rather warm summer.

[summer blizzard]

Given the cold start to the year and last years record Autumn i do think that we will come in below last year, so long as we don't get a hot summer.

In terms of my expectations, we are currently seeing the stratospheric anomolies which indicate the final warming is on its way essentialy meaning that with a -QBO in place, the Polar Vortex is likely to collapse within the next month.

In terms of our summer prospects, that is down to the QBO and ENSO combination, our current situation is that we have a El Nino event which has now peaked, and assuming we don't get a record high or low event, a easterly QBO which will peak between April and November.

If we are to see a good summer, we need to keep the El Nino going for as long as we can, and see the QBO peak as fast as possible, because until we lose the easterly QBO and as long as the ENSO event weakens, we are going to see a neutral to negative AO signal preventing a real sustained hot month, once either of these factors change, we see a neutral to positive AO signal and provided it happens soon, its game on for a hot summer.

[lukemc]

Hi,

Is a neutral to negative AO/NAO signal in the summer more likley to result in a poor or washout summer? Did the summer of 2007 have a negative AO/NAO signal? I thought that was mainly a result of a La Nina pattern resulting in a more southerly tracking jet. Is a negative AO likley to result in a southerly tracking jet in the summer. Is it also likely to suppress the possibility of Azores ridging leaving us prone to more cooler/unsettled incursions?

Luke

[AderynCoch]

Hi,

Is a neutral to negative AO/NAO signal in the summer more likley to result in a poor or washout summer? Did the summer of 2007 have a negative AO/NAO signal? I thought that was mainly a result of a La Nina pattern resulting in a more southerly tracking jet. Is a negative AO likley to result in a southerly tracking jet in the summer. Is it also likely to suppress the possibility of Azores ridging leaving us prone to more cooler/unsettled incursions?

Luke

A negative AO basically means the supression of westerly winds off the Atlantic, so in summer this should favour warmer, more settled weather (though hardly guaranteeing a barbecue summer).

Summer 2007 saw the jet stream tracking right over us - and we got royally soaked as a result.

[BornFromTheVoid]

As far as I can see, the closest match to this year so far is 1803. It had a January of 1.8C, February 3.4C, March of 6.3C and an April of 9.1C, which I imagine won't be far off what we get this month.

The most noteworthy thing from that year was a very cold Autumn with September 11.4C(-2.3), October 9.3C(-1.1), November 5C(-1.9) and a warm July at 17.6C. The year ended up at 9.05C anyway.

Edited April 21, 2010 by NaDamantaSam

[AderynCoch]

edit - never mind...

[reef]

As long as April finishes below 9.4C (pretty much guaranteed now), we'll have a running 12 month mean below 9.74C and therefore below the 1971-2000 average. May and June had 1.5 cumulative degrees between them last year aswell, so if those come in around average then we stand a small chance of beating the running 12 month low of 9.54C set in February last year. That would make it the coldest 12 month period since February 1997.

[Stu_London]

As long as April finishes below 9.4C (pretty much guaranteed now), we'll have a running 12 month mean below 9.74C and therefore below the 1971-2000 average. May and June had 1.5 cumulative degrees between them last year aswell, so if those come in around average then we stand a small chance of beating the running 12 month low of 9.54C set in February last year. That would make it the coldest 12 month period since February 1997.

9.47C - 15/02/08-14/02/09

[reef]

9.47C - 15/02/08-14/02/09

You're correct of course, but you know full well I was talking about full months.

[Eugene]

The GFS ensembles indicate a cold first half to May reef so that should help alot with beating that 12 month running low of 9.54C, we need don't need any largely above average prolonged periods between now and end of June.

[Weather-history]

The coolest first quarter (Jan to Apr) to a year since 1987

[kold weather]

Not bad Mr.Data, though no doubt Jan and Feb did all the hard work in that respect!

Anyway still every chance of going sub 10C and a real chance if May comes in average or below of having the coldest year since 1996. Of course a very warm season could yet easily blow that out of the water but for now its still very possible....

By the way if we can get 9.9 for the year, then we'd have just gone through the 'coolest' 3 year period since 1991-1993...however it'd still be above the 71-00 average....unless something extreme happened....

[Optimus Prime]

Mean Min;

1987 January - April 1.5c

2010 January - April 1.3c

Mean Minima for May 1987 was 5.8c. 0.2 cooler then April Minima of the same year

[Stu_London]

01/05/09-30/04/10 - 9.69C

Looks like this could fall significantly during the first half of May, perhaps into the 9.5s for a while.

Not sure last years low of 9.47C can be breached - would need May to stay cold throughout.

[Stu_London]

12/05/09-11/05/10 - 9.62C

Some more drops over the next 2-3 days, then things are less certain.

An average summer and autumn could see the rolling CET down towards 9. Unthinkable a couple of years ago.

[Gavin P]

Nevermind a CET in the 9's. I'd still not rule out a sub 9c CET from here.

[Eugene]

Me neither gavin, i feel the very dry Spring is really a bad omen for the summer ahead, we've seen so many times how very dry springs lead to wet summers, i'm a great believer in the balancing out theory so we will make up for all the very dry conditions soon and summer is soon.

The next week could be one of the warmest and driest spells of the May to September period IMO

[Cheshire Freeze]

Me neither gavin, i feel the very dry Spring is really a bad omen for the summer ahead, we've seen so many times how very dry springs lead to wet summers, i'm a great believer in the balancing out theory so we will make up for all the very dry conditions soon and summer is soon.

The next week could be one of the warmest and driest spells of the May to September period IMO

I feel the same Eugene. Just posted over on TWO a response to the article in the Daily Mail which talks about how we are going to experience a long hot summer hitting temps of 38.5C. I think we'll struggle to push 32C TBH. September likely to be a wet month by my reckoning.

Aaron

[Don]

Me neither gavin, i feel the very dry Spring is really a bad omen for the summer ahead, we've seen so many times how very dry springs lead to wet summers, i'm a great believer in the balancing out theory so we will make up for all the very dry conditions soon and summer is soon.

The next week could be one of the warmest and driest spells of the May to September period IMO :o

Whilst I agree that this dry Spring could well be a bad omen for the Summer, there could of course be an exception to the rule as I think that Spring 2003 was dry and we all know what followed! However, I wouldn't want a Summer as hot as 2003 or 2006.

[snowlover2009]

i can understand why you are worried that we might get a wet summer, but the last 2 wet summers produced 2 cold winters , but 2007 which was the wettest didnt. i know its not the same, but still. we had 3 dry springs 2007, 08 and 09, maybe 2010 with pot look we may get away with it. like i said, summer 2007, gave us a very mild winter, 08/2009 and 2009/10 gave us a cold winter.

But if the theory is right, dry springs equalling to a wet summer, i would be sincerely worried as IMO this spring has been way dryer than that of 2007 and look what happened.

But looking at the charts for later FI form gfs and ecm for a example, the atlantic is starting to pick up a little more and the blocking is declining more and more. Look at ecm 216, then the 240 charts....

i dont know if that is good sign or a good summer, but i think it is very early.