April CET

[North-Easterly Blast]

My point is that last winter proved that cold winters are not extinct, that northerly blocking is still possible. You can apply that same arguement to April.

And as Optimus Prime has mentioned, December has somewhat bucked the trend of a warming in the months. Whilst other months have been registering very mild after very mild month, very mild Decembers in the last 21 years have been very few. Why has December struggled and yet October, November January and February within that period did so with ease?

This is quite strange, and in the last 20 years December has been largely close to the long term average overall, as opposed to most if not all other months in the year showing a significant warming trend. In each of the decades of the 1990s and 2000s three Decembers managed to be at least 1*C below the 1961-90 average. This was actually a bucking of the trend of mild Decembers that had largely dominated the 1970s and 1980s.

December was generally very cold in the 1960s, then very mild in the 1970s and 1980s, then overall close to average in the 1990s and 2000s.

January and February have been a bit like December in delayed fashion. Overall January and February were generally very cold during the 1977-1987 period, then abruptly changed during the late 1980s (a bit like how December did at the turn of the 60s to the 70s), then Jan and Feb were very mild in the 1990s and 2000s, immediately following a cold to very cold run from the late 70s to the mid 80s. (in a similar fashion as to how December was very mild in the 70s and 80s after a very cold run in the 60s)

I'm starting to wonder whether we can see a decently mild December again (above 7.0c)

There were only four Decembers in the 1900s with a CET above 7.0*C, 1900, 1934, 1974 and 1988. 7.0*C+ really is extremely mild for December. Really anything above 6.5*C is very mild for December I would say, so in 2006 (6.5) we did see something approaching a very mild December. But you are dead right, in the 1990s and 2000s we really have seen some extraordinarily mild Januarys and Februarys as opposed to notably mild Decembers.

[Optimus Prime]

December by decade

2000s 4.7c

1990s 4.6c

1980s 5.2c

1970s 5.3c

1960s 3.5c

1950s 5.0c

1940s 4.8c

1930c 4.4c

1920s 4.5c

1910s 5.1c

1900s 4.3

I agree we're about average for December for the last two Decades. Decembers are usually 0.9c warmer then January and February. A very mild January or February would be 5.8c or above. So that means for December above 6.7c or above is very mild. It happened every decade aside from the 1960s, 1990s and 2000s in the last 110 years.

[North-Easterly Blast]

December by decade

2000s 4.7c

1990s 4.6c

1980s 5.2c

1970s 5.3c

1960s 3.5c

1950s 5.0c

1940s 4.8c

1930c 4.4c

1920s 4.5c

1910s 5.1c

1900s 4.3

I agree we're about average for December for the last two Decades. Decembers are usually 0.9c warmer then January and February. A very mild January or February would be 5.8c or above. So that means for December above 6.7c or above is very mild. It happened every decade aside from the 1960s, 1990s and 2000s in the last 110 years.

December actually did become warmer during the 1900s compared to the 1700s and 1800s. In those centuries the average for December was 4.0 and 4.1*C respectively. Whereas in the 1900s it was 4.6*C.

The reason largely why Decembers are on average warmer than January and February is down to the fact that sustained cold seems to be possible for longer in Jan and Feb, and also cold sources are often colder then. Look at famously cold months like Jan 1963 / Feb 1947, 1895 / Jan 1940 etc. We have never achieved a December CET lower than -0.8*C. Take Jan 2010 also (1.4). Getting a December CET this low would still be difficult, as during December and especially the first half our cold sources are rarely cold enough.

[damianslaw]

Is this the April CET thread or the Dec CET thread, recent posts would seem to suggest the latter..

Back to topic, the CET is likely to nudge close to 9 degrees as we see some particularly mild CET in the next three days and then only a slight cool down in the last two.

[Summer of 95]

Looking back on earlier decades, there were quite a number of cold Aprils that were at least 0.5*C below the 1961-90 average:

1980s 3 1983, 1986, 1989

1970s 4 1970, 1973, 1977, 1978

1960s 2 1966, 1969

1950s 4 1951, 1953, 1956, 1958

1940s 1 1941

1930s 2 1932, 1936

1920s 3 1922, 1924, 1929

1910s 3 1910, 1917, 1918

1900s 4 1903, 1905, 1906, 1908

So in all the decades of the 1900s, bar the 90s, the majority managed two or three cold Aprils, two decades managed four and even the very warm 1940s still managed one cold April. So it is so staggering that neither the 1990s or 2000s have managed even one cold April. So it really is a pattern that has dissappeared from our weather in recent years compared to something that was by no means unusual. So looking at the absence of cold Aprils now for over two decades it makes you wonder if it will happen again.

Another major change has been the lack of snowfall in recent Aprils. I do believe that the Aprils 2002, 2003, 2004, 2005, 2007 and 2009 all passed without any snow falling at lower levels at least in the whole of the UK, and I do not think that there have been any instance of any snow falling at low levels in this present April, 2010. Whereas in the 90s the Aprils of 1991, 1994, 1996, 1998 and 1999 saw snow fall at fairly low levels at times and a covering in places. In the 1980s I believe that all Aprils but 1984 and 1987 did see snow fall to reasonably low levels at times.

To summarize it in the past the majority of Aprils would normally at least on occasion see snow fall to low levels in the UK with on higher levels at least a proper covering at some stage. Whereas over the last ten years it appears to have become much more the exception rather than the norm.

Not 2003 or 2005- both had 1 day of snow falling here. In 2003 it was just before that mid-month heatwave so quite a turnaround.

2007(and 2010) could well have ended up snowless even if it was 5C cooler, simply because it was so dry. 2004 was surely the least wintry April of the lot- not only was it totally snowless virtually everywhere despite being quite wet; it was also virtually free of frost unlike 2007 and 2010.

[AderynCoch]

Manley still only 8.2C up to the 25th. Hadley was running slightly higher last time the site was up, but with only a few days left I think the ceiling is 9C.

[Optimus Prime]

April 2007 was the most snowless April. No snow was recorded anywhere all month.

[Thundery wintry showers]

The biggest change with April, to my mind, has been an increase in the number of completely snowless Aprils across lowland Britain. If I remember rightly the Aprils of 2002, 2004, 2007 and 2009 all passed by without a flake of sleet or snow falling anywhere in mainland Britain at low levels (though some of the Scottish islands might have had some). None of the Aprils of the 1990s managed this- 1993 and 1997 came very close, but they both had localised snowfalls over certain areas of the country in the first few days.

I don't know how North-Easterly Blast appeared to miss that post- I omitted 2003 and 2005 for a very good reason. I didn't see any sleet or snow in Cleadon at any poiont during April 2003 but I'm aware that some other parts of the country had some from a weak easterly in the second week. A brief 24-hour northerly on the 8th April 2005 was cold enough to deliver widespread sleet and snow showers across the country.

And yes, April 2004 really sticks out for its lack of frost across the country, mainly owing to a combination of warmth and cloud cover. There was a northerly outbreak in the first week but it was quite feeble, plus our side of the Arctic was anomalously warm at the time, and so temperaturs barely fell below the long-term average. April 2009 in Tyneside was also frost-free and remarkable for homogeneity rather than any outstanding warm spells, in stark contrast to Aprils 2003 and 2007 which had very pronounced warm spells.

[reef]

I don't know how North-Easterly Blast appeared to miss that post- I omitted 2003 and 2005 for a very good reason. I didn't see any sleet or snow in Cleadon at any poiont during April 2003 but I'm aware that some other parts of the country had some from a weak easterly in the second week. A brief 24-hour northerly on the 8th April 2005 was cold enough to deliver widespread sleet and snow showers across the country.

And yes, April 2004 really sticks out for its lack of frost across the country, mainly owing to a combination of warmth and cloud cover. There was a northerly outbreak in the first week but it was quite feeble, plus our side of the Arctic was anomalously warm at the time, and so temperaturs barely fell below the long-term average. April 2009 in Tyneside was also frost-free and remarkable for homogeneity rather than any outstanding warm spells, in stark contrast to Aprils 2003 and 2007 which had very pronounced warm spells.

I actually had a frost here in April 2004, albeit just - with a min of -0.2C on the 9th.

Since 1983, the following years have seen frostless Aprils here: 1987, 1988, 1991, 1992, 1993, 1994, 2001, 2002, 2007, 2009, 2010.

With regards to sleet/snow falling, 1987, 1993, 1996, 1997, 2002, 2003, 2004, 2007, 2009 and 2010 so far have all had nothing here in the same time period.

Milder, more snowless and frostless Aprils have gradually become more common in the last decade. No doubt, due to the fact that every single year has been above average in temperature since 1991, except 2001.

[Optimus Prime]

I seewm to remember light snow in April 2003 with a temperature of 7.0c. It didn't really settle but it was light, proper snow. 4cm fell in 2008. No snow in 2001 despite it being near normal. Major snow event in April 1989, about 7cm. Aprils of the 80s were certainly cold and snowy in general.

[The PIT]

What's happened to the met office Hadley page??? Still seems to be down.

Well according to old Philip it's 8.2C o.2C above normal.

[damianslaw]

I actually had a frost here in April 2004, albeit just - with a min of -0.2C on the 9th.

Since 1983, the following years have seen frostless Aprils here: 1987, 1988, 1991, 1992, 1993, 1994, 2001, 2002, 2007, 2009, 2010.

With regards to sleet/snow falling, 1987, 1993, 1996, 1997, 2002, 2003, 2004, 2007, 2009 and 2010 so far have all had nothing here in the same time period.

Milder, more snowless and frostless Aprils have gradually become more common in the last decade. No doubt, due to the fact that every single year has been above average in temperature since 1991, except 2001.

Surprised you haven't managed a frost this month. Its been a notably frosty month in many inland parts especially in the north and in Scotland.

Minima this month has been fairly low with many 1's, 2's and 3's..

[Thundery wintry showers]

It doesn't really surprise me- Reef's location appears notably frost-free, more so than Cleadon, presumably due to coastal proximity with possibly a bit of urban heat island effect thrown in. Thus if the country as a whole has a succession of nights that are cool but not remarkably so, such coastal areas will often remain frost-free.

Edited April 26, 2010 by Thundery wintry showers

[reef]

It doesn't really surprise me- Reef's location appears notably frost-free, more so than Cleadon, presumably due to coastal proximity with possibly a bit of urban heat island effect thrown in. Thus if the country as a whole has a succession of nights that are cool but not remarkably so, such coastal areas will often remain frost-free.

Yes, thats pretty much the case. Theres never been an air frost here after 26th April since at least 1982 and by this time of the year the average min is around 6C. What has been notable this month as you mention is the extensive number of cool nights (minima of 1-4C) but no very cold ones - so much so my average min is still below the 1971-2000 mean for now. Theres not too much of a UHI effect, but being 8 miles by crow from the North Sea and a couple of miles from the wider part of the Humber make frosts very difficult to achieve unless circumstances are exceptional. The following Metoffice chart shows it nicely:

http://www.metoffice.gov.uk/climate/uk/averages/7100_1km/AirFrost_Average_1971-2000_17.gif

Im almost sure there would have been a frost in early May 1979 (on 7th May 1997 I recorded a min of 0.3C), but this is as extreme as a temperature of above 31C in summer - something that has only happened once in the same time period (34C in August 1990, the next warmest is 30.9C in August 2003).

[SteveB]

Finally the Hadley link is working,

8.6c to the 26th, 0.9c

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

[SteveB]

8.9c to the 28th, 1.1c

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

[reef]

Its looking like we'll end up with another warm, dry and sunny April - much like 2007, 2009 and 2010. The level of sunshine is particularly notable, being just 20 hours under the record.

[damianslaw]

8.9c to the 28th, 1.1c

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

Could well finish with 9 degrees, today will probably have added at least 0.1 degrees to the CET perhaps 0.2 degrees, and tomorrow looks fairly mild, unadjusted figure 9.1 or 9.2 degrees with downward correction to 9 degrees. Have to say it has been the past couple of days which have made a huge difference, adding at least 0.5 degrees to the CET.

[Snowstorm1]

Could well finish with 9 degrees, today will probably have added at least 0.1 degrees to the CET perhaps 0.2 degrees, and tomorrow looks fairly mild, unadjusted figure 9.1 or 9.2 degrees with downward correction to 9 degrees. Have to say it has been the past couple of days which have made a huge difference, adding at least 0.5 degrees to the CET.

My guess of 8.8C is going to be a little bit out then oh well

[SteveB]

9.1c to the 29th, 1.2c

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

9.1c to the 29th, 1.2c

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

[Don]

Our run of below average months has come to an end. However, May is looking like it could be on the cool side.

[Eugene]

Just to prove you shouldnt always judge a month by its CET, apart from a few days earlier this week it hasn't felt that warm at all though, on my walks in the countryside this April my memories have been of cold mornings and cool easterly/northerly winds only the sun's strength making it feel pleasant from mid morning onwards.

[J10]

Just to let everyone know, I will be doing the figures over this weekend and they should be done by Monday.

[LomondSnowstorm]

Well done Shuggee - looks like you're exactly right!

Can't be too upset though - my 8.9C certainly isn't far off.

[DAVID SNOW]

Well done Shuggee - looks like you're exactly right!

Can't be too upset though - my 8.9C certainly isn't far off.

Nah, rounded down to 9.0