This thread is for all comments, discussion and analysis of temperatures in the UK during April, with particular emphasis on the Central England Temperature (CET), for the simple reason that it is the longest running temperature series in the world with over 360 years of data. But you can comment on any interesting temperature statistics or data from across the UK, including your own back yard.

March has been another very warm month although not quite reaching 8C due to some cold nights. April is looking like starting rather chilly but hopefully that will not last too long.

For those taking part in the competition all CET predictions for April should be sent directly to me via the forum private message system. Do not post them directly into the thread.

The deadline for predictions this month is 2359 on Tuesday evening (2 April). 

Now on to some data for April:

Historic CET summary for April

1971-2000 8.1C (30 years)

1981-2010 8.5C (30 years)

1999-2018 9.0C (last 20 years 

Last April was very warm with a CET of 9.8C. We have had some cold April's recently with 7.2C in 2012, 7.5C in 2013 and 7.5C in 2016. Prior to 2012 there had not been a CET lower than 7.7C in April since 1989.

Here is a chart of the April CET for all years since 1961:

Direct link to larger version of the chart

Latest model output - 12z 1 March

GFS (12z) - a chilly start but turning gradually milder

http://www.wetterzentrale.de/de/show_diagrams.php?geoid=49069&model=gfs&var=2&run=00&lid=ENS&bw=

GEM (12z) - more scatter than the GFS but similar trends

http://www.wetterzentrale.de/de/show_diagrams.php?model=gem&var=2&geoid=49069&lid=ENS&bw=

Multi Op - fairly good agreement on a cold snap followed by a return to milder conditions

http://www.wetterzentrale.de/de/show_diagrams.php?model=multi&var=2&geoid=49069&lid=OP&bw=

The ECM ENS T2m temperatures for De Bilt show quite a lot of scatter but a definite gradual warming trend from the end of the first week of April. 

http://cdn.knmi.nl/knmi/map/page/weer/waarschuwingen_verwachtingen/ensemble/detail/ensemble-verwachtingen-detail10.png

Met Office contingency planners outlook 

https://www.metoffice.gov.uk/binaries/content/assets/mohippo/pdf/public-sector/forecast-temp-amj-v2.pdf

Shows a signal for higher than average probability of above average temperatures for the next 3 months

Temperature analogues

Last month's analogue signal was very strong for a warm March and that has proved to be correct.

This month we have a slightly split signal.

If we look at Aprils following a very warm February and March we find the following matches since 1945 with the related April CET

1945 10.1C, 1961 10.0C, 1990 8.0C, 1997 9.0C, 1998 7.7C, 2000 7.8C, 2002 9.3C, 2017 8.9C

So of 8 years we have 5 that are very warm (8.9C or higher) and 3 that are close to the 1971-2000 average (7.7-8.0C).

The closest match to 2019 is 1961 with a January CET of 3.9C, February of 6.9C and March of 8.2C.

Long range models are mostly hinting at a warmer second half of April. 

First look at March temperature tracker 

After a cold start the temperature should be back above average by the middle of the month.

GW you have a full inbox, i just tried to PM you my Prediction

Sorry now sorted

Really interesting indications for the first half of this month, with major HLB dominating the scene while focused N or NE of the UK. 

It looks unusually chilly Tue-Fri next week but it may then turn milder from the east. After that, there's a fine balance between warmer air from south of east and colder air from north of east, this probably being interrupted or broken down by the third week of the month by broad Atlantic troughs out to the west - though these may prove hesitant to move right across the UK given the El Nino base state.

Hard to have much confidence in either cool or warm conditions dominating while the easterly type regime is in place. Good luck everyone! 

For what it's worth, some GFS runs prior to today were giving me CET estimates to the midpoint of the month in the high 5s or low 6s, more than 2*C below the LTA! 

Big shift away from that today but is it a true one or just a swing?

No Hadley Met office.

Metcheck         6.11c     Anomaly   -1.91c

Netweather      7.51c     Anomaly   -0.6c

Mean Of My 10   6.49c.  Difference  -2.76c.       

Met Office Hadley         8.1c.      Anomaly      1.2c. Provisional to 2nd.

Metcheck                      5.21c     Anomaly      -2.81c

Netweather                   6.5cc     Anomaly       -1.61c.

Mean of My 10 Stations 6.11c.   Difference    -3.14c.   Using A 6-Year Average.

Have posted full stations  on the March Temperature Analysis as a BLOOPER

Uh... 8.1*C?

That's a long way above what the modelling was indicating for 1st-2nd (6.5 to 7.0*C).

Will be interesting to see how GW's stats compare. Even down this way, my local mean is only 7.7*C for 1st-2nd having dropped from a healthy 9.5*C on the opening day.

Last night I had a min of -3.0*C here which is a local date record for the 21st Century. Pea-sized hail from a shower yesterday evening was frozen hard and coated with a heavy frost - quite the wintry scene for April!

Looking ahead, the models continue to advertise a lot of HLB and often in locations that bring unusually low temps to the UK, either by night, by day, or by both. Some variations in timing with ECM markedly milder than GFS for this coming Sun-Mon (due to it not bringing an upper cold pool and trough across - an ongoing big disagreement with GFS there!) but chillier for the following Wed-Fri.

Seeing subzero mins and maximums of only 7 or 8*C from that model for that last period down here strikes me as highly unusual for largely dry conditions in mid-April; usually it takes a lot of cloud and precipitation to keep the temps that low by day.

For my CET estimate, I've banked on the El Nino background pulling through once the HLB regime relaxes - a risky double assumption! - to build Euro-UK ridges and recover temps to a little above the LTA. Let's see how that goes...   .

Uh... 8.1*C?

That's a long way above what the modelling was indicating for 1st-2nd (6.5 to 7.0*C).

Will be interesting to see how GW's stats compare. Even down this way, my local mean is only 7.7*C for 1st-2nd having dropped from a healthy 9.5*C on the opening day.

 

Last night I had a min of -3.0*C here which is a local date record for the 21st Century. Pea-sized hail from a shower yesterday evening was frozen hard and coated with a heavy frost - quite the wintry scene for April!

Looking ahead, the models continue to advertise a lot of HLB and often in locations that bring unusually low temps to the UK, either by night, by day, or by both. Some variations in timing with ECM markedly milder than GFS for this coming Sun-Mon (due to it not bringing an upper cold pool and trough across - an ongoing big disagreement with GFS there!) but chillier for the following Wed-Fri.

Seeing subzero mins and maximums of only 7 or 8*C from that model for that last period down here strikes me as highly unusual for largely dry conditions in mid-April; usually it takes a lot of cloud and precipitation to keep the temps that low by day.

 

For my CET estimate, I've banked on the El Nino background pulling through once the HLB regime relaxes - a risky double assumption! - to build Euro-UK ridges and recover temps to a little above the LTA. Let's see how that goes...   .

Given how cold it is just now, I felt that I had to check the Hadley website itself just in case this was another of Arty's famous typos but that was shown not to be the case this time.

 

Given how cold it is just now, I felt that I had to check the Hadley website itself just in case this was another of Arty's famous typos but that was shown not to be the case this time.

 

On the met office website 8.1c (+1.2) is to the 1st

 

Given how cold it is just now, I felt that I had to check the Hadley website itself just in case this was another of Arty's famous typos but that was shown not to be the case this time.

 

On the met office website 8.1c (+1.2) is to the 1st

My calculations for the 1st have a figure of 7.14C so the Hadley figure is about 1C too high. Not that uncommon for individual days to be 1C or more wrong on the original Hadley provisional data.

My CET mean for the 2nd is just 5.7C and for today it is 3.8C. 

So the overall mean up to the 3rd is just 5.56C.

 

My calculations for the 1st have a figure of 7.14C so the Hadley figure is about 1C too high. Not that uncommon for individual days to be 1C or more wrong on the original Hadley provisional data.

My CET mean for the 2nd is just 5.7C and for today it is 3.8C. 

So the overall mean up to the 3rd is just 5.56C.

I can therefore see from that, why there are downward corrections at the end of nearly every month in order to allow for that.

I'm starting to regret going high already!

Met Office Hadley          7.4c.      Anomaly      0.7c.    Provisional to 2nd.

Metcheck                        4.49c.    Anomaly     -3.49c.  Updated Hourly.

Netweather                     5.59c.    Anomaly      -2.5c.   Updated Hourly

Mean of my 10 stations  5.88c.   Difference   -3.37c.  Using a 6-Year Average.

Met Office Hadley      6.2c      Anomaly    -0.2c. Provisional to 3rd.

Metcheck                   4.80c    Anomaly    -3.22c

Netweather                5.44c    Anomaly    -2.67c.

Mean of my 10           6.21c    Difference  -3.04c.    

Met Office Hadley          6.2c.       Anomaly       -0.1c.  Provisional To  5th.

Metcheck                       5.40c      Anomaly       -2.62c

Netweather                    6.11c      Anomaly       -2.0c

Mean of my 10 stations   6.78c.     Difference     -2.47c.   

Here are the predictions for April. Quite a few people going for temperatures well above 9C. There are strong signs that despite the rather cool start to the month, the second half of April could be a lot warmer.

Direct link to full sized table

Here is the latest April CET tracker. Expecting the CET to be above 9C by the end of week 3.

A very large downward adjustment looks likely this month (or at least so far - that may not hold for the whole month). Often the downward adjustment is larger in cold conditions that in warm conditions. I think that is because the data used for the provisional numbers comes partly from some coastal stations which tend to remain warmer due to the influence off the sea when it is colder inland.