April Cet

[Weather-history]

Philip Eden has the CET as 6.6C (-1.3C) up to the 15th

http://www.climate.uk.co.uk/

Philip's anomaly for me gives the true feel of the month as that value takes into account all the recent warm Aprils, its based on the 1981-2010 average as opposed to Hadley which is still using a 30 year average that is 22 years out of date, the first year of that average was over 50 years ago!

It was only 0.1C warmer than the first half of January 2012 for Philip's value.

Edited April 17, 2012 by Mr_Data

[Kentish Man]

Met Office Hadley is on 6.8C (Jan 1 - 16). This is 0.4C lower than the running 1961-90 mean.

However I agree with Mr Data's point above that in general it is ludicrous to use such an outdated average for comparison purposes even if as it happens the 1961/90 mean for April is identical to the whole CET series average.

Edited April 17, 2012 by Kentish Man

[damianslaw]

Suspect there will be a marked reduction in the CET by the months end - not quite the same scale as Feb, but the current value seems to high for me, minima have been unestimated.

[Thundery wintry showers]

There is a chance of the value being pushed up towards the 8C mark by a warm last week of the month though, as the prevailing trough drifts out into the Atlantic allowing southerlies in- it's certainly been a trend in recent years for Aprils that are generally cool until the 20th to then feature a bout of southerly winds. 1998, 2000 and 2008 were all good examples of this.

Re. the use of 30-year averages it all depends on the purpose of the analysis. I don't see much wrong with persisting with the 1961-90 average in a long-term climatological analysis (although for those purposes I'd argue that a longer-term average like 1951-2000 would make more sense), but when giving a sense of how current weather compares with the recent 'average' it is a lot harder to justify.

The World Meteorological Organisation are partly to blame there as they have a policy of sticking with 30-year averages that they shift forward every 30 years, rather than every 10 years.

[summer blizzard]

6.9C to the 17th.

[reef]

Its worth noting that the remaining 14 days only need a mean temp of 8.6C for this to be the coldest April since 1989 and 8.2C to be 1.0C below the 1981-2010 average.

The models suggest this both of these are very likely at the moment.

[BornFromTheVoid]

I noticed that we're yet to record day averaging 10C or above this April.

Does anyone know if many past Aprils have failed to achieve a daily mean of 10C or higher?

[reef]

I noticed that we're yet to record day averaging 10C or above this April.

Does anyone know if many past Aprils have failed to achieve a daily mean of 10C or higher?

The last time was 1986. The highest daily mean that month was 9.1C on the 27th. In fact, it took until May 1st to record a double digit day that year!

April 1989 came close with every day being in single figures except the 1st, which was exactly 10.0C.

Meanwhile Hadley is on 7.0C to the 18th. Yesterday was 7.3C.

[Weather-history]

The last time was 1986. The highest daily mean that month was 9.1C on the 27th. In fact, it took until May 1st to record a double digit day that year!

The first double digit CET daily mean for 1973 wasn't until ...the 4th of May.

As far as I'm aware, the Aprils of 1782, 1799, 1809, 1812, 1869, 1879, 1925, 1941, 1973 and 1986 didn't record a single double digit CET daily mean.

Edited April 19, 2012 by Mr_Data

[virtualsphere]

Very early days yet, but what is the biggest CET difference between two consecutive Aprils? With the record high being set last year, if the current set-up continues we might be in with a shot of breaking it.

1798 = 10.4

1799 = 5.4

A difference of 5.0C. We'd need to finish lower than 6.8C this year to break that particular record, which is a bit of a stretch but at this stage still doable nevertheless.

Surprisingly we're still in with a chance of breaking this record, although it looks to be very close at this stage. If we are going to beat it, this is the year to do it after the record breaking April last year!

[damianslaw]

Can't see the CET changing much in the coming days, maxes often in the 10-11 range and mins in the 4-5 range giving means between 6.5 and 8 degrees, so perhaps a slight rise can be expected by this time next week at best, perhaps 7.5 degrees.

Upper most limit for the CET 8 degrees, lowest probably around 6.7-6.8 degrees, finishing mark probably mid- low 7's I imagine, say 7.4 degrees, taking into account downward correction, small chance we could still come in below 7 degrees, but highly doubt we will beat 1989, but very likely to end up seeing the coldest April since 1989.

[summer blizzard]

7C to the 20th.

[Summer Sun]

7.0 to the 21st, -0.5 below average

[Lettucing Gutted]

It looks like this year could see the biggest decrease in mean monthly temperature from March to April since 1989.

[Kentish Man]

It looks like this year could see the biggest decrease in mean monthly temperature from March to April since 1989.

What was the decrease that year?

Meanwhile the Met Office Hadley reports the CET has edged slightly upwards to 7.1C (Apr 1 - 22)

[Stargazer]

Hadley shows 7.5 in March 1989 and 6.6 in April. I believe the last time April was colder than March was 1998 (if I recall correctly April 1998 was a miserable month with severe flooding in parts of the Midlands).

[Roger J Smith]

The complete list of Aprils that were colder than March or any other preceding month (back to December) can be found in post 101 of this thread. You're right about 1989 and 1998.

I just looked at the CET for second half of April and the coldest in the series is 4.5 C in 1808, in recent decades, 6.2 C in 1973. Then I changed the filter to the last ten days and the coldest there was 4.5 C in 1808 and in recent decades, 5.8 C in 1973.

The last time that 21-30 April averaged below 10.0 C was 2001 with 7.8 C. Other cold years since 1973 were 1977, 1981 and 1983.

The latest subzero day was -0.2 C on 19th in 1772.

Some particularly cold days in late April were 29th in 1856 which averaged 0.7 C, and 24th in 1908 at 0.5 C ... nothing that extreme in recent years, the coldest I could find since a 3.2 in 1989 was 3.5 C on the 19th in 1995.

Edited April 24, 2012 by Roger J Smith

[AderynCoch]

Depends what you mean by "recent years" but there was also late April 1981 with a second half of 6.2C, a last ten days of 5.8C and the period 23rd-26th averaging just 3.4C.

I make the second half of April 1808 to come out at 4.5C.

[DAVID SNOW]

7.1 to the 23rd,could be at about 8 by months end,maybe a final figure after corrections of 7.6?

[Weather-history]

Looks like it was the coolest St George's day since 1991 for the CET

[BornFromTheVoid]

Minimum today is 4.6C while maxima should be around 11C, so an increase to 7.2C likely tomorrow.

After that with the 06z GFS

7.1C to the 25th (6.8]

7.2C to the 26th (9.4)

7.3C to the 27th (8.9)

7.3C to the 28th (8.9)

7.5C to the 29th (11.3)

7.7C to the 30th (12.9)

7.2C to 7.6C the likely figure after corrections

Edited April 24, 2012 by BornFromTheVoid

[damianslaw]

Tomorrow is likely to bring suppressed maxima to the CET zone, much like yesterday as we see the influence of leaden grey skies and a cold wind, though temps may recover later in the day in southern part of the zone once the front moves north.

It is now looking less likely this month will come in sub 7 degrees, mainly because of minima over the next 6 nights which won't get too low thanks to cloud cover. Still believe we could end up close to 7 degrees with downward correction. A good bet at this stage is a finishing figure inbetween the 7.2 - 7.5 degree range, a colder than normal month but not exceptionally so. If we were about to see the influence of high pressure from the north, then this month would most likely have been colder than 1989 with some very cold nights.

[Scorcher]

If we were about to see the influence of high pressure from the north, then this month would most likely have been colder than 1989 with some very cold nights.

The thing is it has been a month of homogeneously cool weather with very little exceptionally cold weather- frosts have been few and far between in many areas, especially since mid month. Equally one could say had we had a spell of southerly winds, this month would have ended up average or above.

[Lettucing Gutted]

7.1 to the 23rd,could be at about 8 by months end,maybe a final figure after corrections of 7.6?

It is now looking less likely this month will come in sub 7 degrees, mainly because of minima over the next 6 nights which won't get too low thanks to cloud cover.

Indeed unfortunately it looks like another particularly cold April will be blown out of the water thanks to blowtorch nights in the last week ala Aprils 1991, 1994, 1996, 1998, 2000 and 2008.

The thing is it has been a month of homogeneously cool weather with very little exceptionally cold weather- frosts have been few and far between in many areas, especially since mid month. Equally one could say had we had a spell of southerly winds, this month would have ended up average or above.

It will be ironic if people experienced less frosts in the relatively "cool" April 2012 than the blowtorch April 2011. Edited April 26, 2012 by Craig Evans

[damianslaw]

Indeed unfortunately it looks like another particularly cold April will be blown out of the water thanks to blowtorch nights in the last week ala Aprils 1991, 1994, 1996, 1998, 2000 and 2008.

It will be ironic if people experienced less frosts in the relatively "cool" April 2012 than the blowtorch April 2011.

Northern half of the country has experienced quite a few ground frosts this month and at least a couple of air frosts. Mins have been preety low much of the month - less so the last week, but many night at or around the 2-4 degree mark.