April CET

[damianslaw]

This has been mentioned earlier in the thread- they are actually few and far between and major turnarounds are even less common, certainly in recent times.

April 1981 surely delivered a much colder second half than first. The period between 20-27th was notably cold with widespread snow in places thanks to very cold northerly/north easterly airstream.

[Gavin P]

The first half of April 1981 was the warmest for 20 years. The second half was the coldest on record;

http://www.personal.dundee.ac.uk/~taharley/1981_weather.htm

[damianslaw]

The first half of April 1981 was the warmest for 20 years. The second half was the coldest on record;

http://www.personal.dundee.ac.uk/~taharley/1981_weather.htm

What an unusual month it was - a major major switcharound mid month. Not many like it. Would be interested to know ENSO background to the switch to significant cold after early warmth in the month. Was there a strat warming event? Did the vortex implode? Was it a weak neutral ENSO?

[summer blizzard]

CET to the 13th should certainly be above 12C, perhaps a record breaking first half.

What is the record for the first half of April?

[Weather-history]

The first half of April 1981 was the warmest for 20 years. The second half was the coldest on record;

http://www.personal.dundee.ac.uk/~taharley/1981_weather.htm

The second half of April 1908 was colder than 1981, that had a CET of about 5.6C

The first week of April 1926 had a CET of 12.6C

[Thundery wintry showers]

Must have been a rare slip-up in Philip Eden's 1995 book "Weatherwise" (a book packed with statistical information and records) as I think that's where Trevor Harley most likely got his stat from- the quote from the book is "but the second half was the coldest since before 1900".

[chionomaniac]

What an unusual month it was - a major major switcharound mid month. Not many like it. Would be interested to know ENSO background to the switch to significant cold after early warmth in the month. Was there a strat warming event? Did the vortex implode? Was it a weak neutral ENSO?

There was a SSW on 3rd March 1981 - classic 6 week delay? Perhaps we should be looking more towards May for a low CET.

http://www.appmath.columbia.edu/ssws/index.php

Edited April 4, 2011 by chionomaniac

[summer blizzard]

There was a SSW on 3rd March 1981 - classic 6 week delay? Perhaps we should be looking more towards May for a low CET.

http://www.appmath.columbia.edu/ssws/index.php

I always thought that the pattern from a stratospheric warming in general was round a 20 day delay followed by around a 20 day build of heights (longer is warming is sustained).

I actually think that Mid May could be very wet.

CET is 11.6C to the 3rd.

[Roger J Smith]

Here's a very dramatic case of a mid-month reversal. April 1778 was at record pace with 10.9 by the 13th, then never had another day with mean above 10 and finished at 8.2 C.

[BornFromTheVoid]

10.6C to the 4th

http://www.metoffice.gov.uk/hadobs/hadcet/cet_info_mean.html

Yesterday was 7.7C. Todays minimum is 7.6C and maxima will probably be around 14.5C so should remain close to 10.6C by tomorrows update. Looking ahead with the 06z GFS we should be at

11.3C to the 6th

11.2C to the 8th

11.4C to the 10th

11.6C to the 12th.

[Milhouse]

Anyone know what the average April CET up to the 12th is? I'd say its about 7.6c so going by the 06z we'd still be 4c above average by the 12th so it would take a significantly colder second half just to return us to 1c above average.

[summer blizzard]

The period 13th-19th looks fairly cool so that should knock the CET back a bit however if the heat were to return, we could well see 2007 challeneged.

Could somebody post where we were in 2007 at different stages (say 5th, 10th, 15th, ect...)?

[AderynCoch]

Could somebody post where we were in 2007 at different stages (say 5th, 10th, 15th, ect...)?

5th = 8.1

10th = 8.9

15th = 10.1

20th = 10.3

25th = 10.9

30th = 11.2

One big upward slope.

[reef]

Hadley is 10.7C to the 5th. Yesterday came in at 11.0C.

A big nudge upwards tomorrow as today's min is down as 10.9C and many areas breached 20C.

[damianslaw]

Unusually I can see the CET peaking this month by the 12th, with a gradual cooldown during the middle of the month and a rapid cooldown later in the month. Doubt we will eclipse 2007, indeed that month didn't see the real warmth get going until about the 10th, this month it has started earlier and in April it is exceptionally rare to see such warmth hold out from start to finish.

[Scorcher]

Unusually I can see the CET peaking this month by the 12th, with a gradual cooldown during the middle of the month and a rapid cooldown later in the month. Doubt we will eclipse 2007, indeed that month didn't see the real warmth get going until about the 10th, this month it has started earlier and in April it is exceptionally rare to see such warmth hold out from start to finish.

This is all just presumption though, no doubt we will see a cooldown mid-month but no guarantees about what will happen after that- for all we know right now it could warm up again.

[summer blizzard]

Unusually I can see the CET peaking this month by the 12th, with a gradual cooldown during the middle of the month and a rapid cooldown later in the month. Doubt we will eclipse 2007, indeed that month didn't see the real warmth get going until about the 10th, this month it has started earlier and in April it is exceptionally rare to see such warmth hold out from start to finish.

While it is unusual to see warmth hold out from start to finish, i am sceptical as to whether there are any real factors supporting a sustained cooldown.

http://ds.data.jma.go.jp/tcc/tcc/products/clisys/STRAT/html_e/pole30_n.html

While the stratosphere has warmed it is still below average and given the 20 day lag, it may be the very end of the month or even early May before we see a sustained pressure build over Greenland. With the stratosphere as is and angular momentum rising as La Nina weakens and +QBO conditions persist the stratosphere could well work against any cold signal in that we may see a short burst of pressure before the ridge collapses over us and the Jet energises. In essence, any build of pressure could send the ridge east of the UK promoting heat if the signal is not sustained.

http://www.wetterzentrale.de/pics/MT8_London_ens.png

Good ensemble agreement that the CET will fall from the 13th-19th however it is up for grabs afterward.

5th = 8.1

10th = 8.9

15th = 10.1

20th = 10.3

25th = 10.9

30th = 11.2

One big upward slope.

5th = 8.1 (10.7C in 2011)

10th = 8.9 (Likely to be above 11.5C in 2011)

15th = 10.1 (Likely to beat)

20th = 10.3 (Could well be very close)

25th = 10.9

30th = 11.2

Looks like the last ten days will be the effective deciders. I would however be suprised if we do not see a 10C+ finish.

[Eugene]

Looking like some very warm CET forecasts by people on here could be crashed and burned if current model output is correct, i'm thinking now the excellent start to spring has been deceiving us and it will be the best spell of weather for months hope im wrong.

Edited April 7, 2011 by Eugene

[reef]

Hadley is 11.5C to the 6th after yesterday came in at an impressive 15.5C.

Already a mean of 7.3C is required in the remaining 24 days just to reach the 1971-2000 average.

[Milhouse]

Hadley is 11.5C to the 6th after yesterday came in at an impressive 15.5C.

Already a mean of 7.3C is required in the remaining 24 days just to reach the 1971-2000 average.

I recall quite a few days in late June/early July last year didnt come in much higher than 15.5C. Just goes to show how remarkably warm the 6th was. It was both the high daytime maxes and high mins that contributed to such a figure.

Edited April 8, 2011 by Milhouse

[reef]

Another increase today. We're now on 11.6C to the 7th. Yesterday was warm again at 12.5C.

Its certainly going to be an exceptionally warm first 10 days of the month. Current figures would suggest 11.7-12.0C by then.

[hugogo]

Yesterday's 15.5 is makes it the warmes 6th of april since 1772 and daily records began at the CET. It also makes it the 2dn warmest day since at least 1772 for the 10 first days of april, just behind 1946's 15.6 on the 4th of that year!

Warmest days and daily records since 1772 for CET:

4/4/1946: 15.5 degrees.

11/4/1869: 16.0

14/4/1869: 16.1

15/4/1945: 16.3

16/4/1945: 17.0

20/4/1893: 16.6

21/4/1893: 16.1

23/4/1873: 15.9.

25/4/1821: 15.9.

26/4/1928L 16.1.

27/4/1866: 16.6.

28/4/1775: 16.9.

29/4/1775: 19.7.

30/4/1775: 17.4.

It should be noted that even some days at the end of the month have never seen such warm weather [22nd, 24th for example], with the warmest 22nd of april being at 14.3 in 1786 and the warmest 24th staying at 15.3 in 2007.

Closer to this period of year [beginning of april], warmest days on record are usually in the 13 degrees, with 8th being only at 12.5 degrees in 1798! This does seem extremely likely to fall today.

Impressive.

[Milhouse]

Dont forget last night was rather cool so that will offset the high maxima.

[reef]

Another small increase to 11.7C, with the 8th coming in at 12.2C.

Although the minima was slightly cooler than previous days, the max came in at 19.1C.

[reef]

Another small increase to 11.8C to the 9th. Perhaps another rise to 11.9C on tomorrow's update before things start to cool down.

A mean of 6.5C is now required just to reach the 1971-2000 average in the remaining 21 days, or 11.0C to beat the record set in 2007.