North-Easterly Blast
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Metwatch Out of interest, as well as for February, are you able to post a pressure anomaly chart for the whole of winter 2023-24 (December to February period) ?
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reef The cold 1961-90 average February CET of 3.8 contained two sub zero CETs, and four additional sub 2*C CETs. The 1971-2000 average was 4.2*C, which was down to containing only one sub zero CET and three additional sub 2*C CETs. The 1981-2010 average was 4.4, which had one sub zero CET and two additional sub 2 CETs. The 1991-2020 February average CET is 4.9, which had no sub zero CETs and down to only one sub 2 CET. Now February 1991 has dropped out of the 30 year rolling average, it is now in the 5s. It just goes to show that to achieve a 30 year average CET for any winter month under 4*C, you probably need it to contain five or six sub 2 CETs, and at least one sub zero CET.
When a winter month is down to having no sub 2*C CETs within a 30 year period let alone sub zero CETs, it then becomes difficult to achieve a 30 year average even under 5*C. February has basically never been a notably cold month since 1991, and come to think of it, January has only been a notably cold month on one occasion (2010), since 1987.
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Snowyowl9 For a winter ending in 3/4, I think that winter 1953-54 had quite a major cold spell around late January and early February, and there was another fairly cold spell around late February into early March I think.
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It is the 30th anniversary of February 1994. I am very surprised to think that the month was colder for the CET than all except three or four Februarys of the last 30 years (the month was also colder for the CET than all but four or five Januarys of the last 37 years) and yet very few people appear to remember it. I am especially puzzled that it is not often talked about, in that the month actually did bring close to a two week cold esterly spell in the middle to latter half with some good snowfalls for eastern and central parts of the country.
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The PIT In recent times after mild Decembers the rest of the winter has never got colder, but further back in the past there are various years where the rest of the winter has actually turned much colder after a mild December. A few of these that I can think of are 1900-01 (Dec 7.2 Jan 3.5 Feb 2.3), 1918-19 (Dec 6.9, Jan 2.9, Feb 1.9), 1953-54 (Dec 6.9, Jan 2.9, Feb 2.6), 1954-55 (Dec 6.8, Jan 2.6, Feb 1.2). Back in the 1800s other examples could be 1857-58 (Dec 7.3, Jan 3.4, Feb 1.8), 1852-53 (Dec 7.7, Jan 5.1, Feb 0.6), 1843-44 (Dec 7.4, Jan 3.8, Feb 1.6), 1842-43 (Dec 7.2, Jan 4.0, Feb 1.9).
The most recent examples that I could think of for winters that had a pretty mild December followed by a much colder rest of the winter is 1985-86 (Dec 6.3, Jan 3.5, Feb -1.1) and 1986-87 (Dec 6.2, Jan 0.8, Feb 3.6).
Although there have been very mild Decembers where the rest of the winter has remained mild, like 1988-89, and occasional very mild Decembers with the rest of the winter turning less mild but not cold, like 2015-16, and to some extent 1974-75, as the February of that winter fell back closer to average though not cold, though that said March 1975 was below average, particularly with quite a cold spell later on in that month that did deliver some snow to some parts of the country.
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WYorksWeather In late winter and early spring, -5 850hpa's may produce snowfall to the higher elevations of the UK, but for low levels nothing more than short lived snow coverings and more likely a wintry mix of sleet and rain.
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LadyofthestormI do not think that March 2010 was exactly cold after about the first ten days, and I do not think April was.
I do not recall much in the way of cold weather or snow, in March 2021 either, though April 2021 was a notably cold and frosty month, the coldest since 1986, and the first significantly below average April since 1989.
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Penrith Snow Although not the same drop as 1983 I can think of a few other years that had a February that was considerably colder than a mild December and January (winter 1931-32, Dec 5.3, Jan 6.3, Feb 2.9, winter 1929-30, Dec 5.8, Jan 5.6, Feb 2.5, winter 1872-73, Dec 5.3, Jan 5.2, Feb 1.8). A more recent example to a some extent of a winter with a colder February compared to December and January could be 1993-94, with Dec 5.5, Jan 5.3, Feb 3.2). Although not fitted neatly into calendar months, the warmest January on record in 1916 (CET 7.5), was followed by a mid-February to mid-March period with a CET of 2.5 (still a 5*C drop from January to the mid Feb to mid Mar period, like the calendar month of Feb 1983 was from Jan 1983.
I have had a look at really cold Februarys (CET sub 2*C), and most of them have happened in winters that did have a significant cold spell at some point in the earlier part of the winter, though not all of the sub 2*C CET Februarys have been in winters where the earlier part of the winter has been continuously cold. Therefore I conclude that there is certainly good evidence to suggest that if there has not been any significant cold spells in December or January, then it has always been very unlikely for seriously cold conditions to develop in February that are certainly enough to bring the CET under 2*C. On top of this, I also looked at the overall temperatures for the period from the Septembers prior to the cold sub 2*C February CETs. My findings concluded that the majority of our really cold Februarys (sub 2*C CET) were preceded by a September to January (five month period) that was close to average, not warm like the most recent September to January period has been.
Though that said, in the past after other winters with a very mild December and January, not all Februarys have been super mild like this year; some of them have been closer to average.
Given the fact that the earlier part of this winter had not brought any significant cold spells (other than very short lived cold snaps), and especially given the overall temperature profile since last September as described above, I thought that it would never bode well for any serious cold to develop in February. Although I never on the other hand thought that it was a guarantee that it would be super mild like it has been and since January 21st as well. It has basically been one short cold snap last month abruptly falling apart on January 20th and then we have faced a month's worth of weather close to rivalling the warmest 28 or 31 day CET period on record in January and February.
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I believe that today could have the warmest daily CET mean for any February day on record. I believe that the all time record for that is 12.8 on February 4th 2004. With the daily maxima for all three stations likely to average close to 15.5 or maybe a touch higher, minima looked to be close to 11*C, so a daily CET for today in the 13s is inevitable.
The CET for the 28 days from January 21st to February 17th is very likely to reach 7.9 (the overall figure for Feb 1779), so a 28 day period within January and February this year will go down as a spell to rival Feb 1779, and up to next Tuesday 20th, the 31 day running CET could get very close to 8*C, which is the all time record for any 31 day period within January and February.
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Regardless of what the last third of this month holds for us, one thing is certain, is that the 28 day period ending on this Saturday February 17th, is likely to record a CET very close to the all time 7.9 record for the calendar month of February.
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Weather-history In recent times only Marches 2013 and 2018 were below average, and before that in 2006 and 2001. There were a few others that could now be considered in between the older averages and the more modern average. It is a huge increase to consider that the 1961-90 average March CET is 5.7, and the 1991-2020 average March CET is 6.7.
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BlueSkies_do_I_see It is often difficult to give an accurate forecast for temperatures more than around five to seven days in advance, as the further ahead you look, the less accurate forecasting charts become, so consequently temperature forecasts are then not accurately predictable.
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Penrith Snow I do not think that at any point this winter any forecasting model ever pointed to a 1979 revisit. Remember for its general weather pattern, winter 1978-79 was in some ways a bit similar to 1962-63, though only that the depth of cold was not as severe. No model this winter ever suggested that anything on 1979 lines was ever likely.
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Roger J SmithMany thanks for all your hard work in looking through the daily CET data from 1772 to assess all this; it must have taken many hours. With the CET for the last 23 days standing at 7.6 or thereabouts, and with more mild weather to come over the next week, the spell January 21st to February 20th this year will at least be one of the warmest 31 day CET periods on record in January and February, and it could even get close to the all time record in 2002.
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TillyS The all time February CET record is 7.9, set way back in 1779. This is actually one of if not the oldest all time monthly record in the CET I believe.
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Met4Cast I am not sure that it is clear that there is any link between a cool September CET and the sort of winter that follows, whereas if the September CET is close to average, there does not appear to be any trend in the sort of winter that follows. It is really clear that only warm Septembers have an effect on the following winter, in that a high September CET is nearly always followed by mild winter, and it is very rare to get much in the way of cold weather in a winter that follows a high September CET.
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Met4Cast The warm September = mild winter relationship is a bit like how many years ago the UK Met used to use SST anomalies in May to predict the following winter's NAO. If SST anomalies in May showed a tripole of warm / cold / warm anomalies in the north Atlantic during May then the UK Met used to predict a negative NAO in the following winter. I do not know why May was chosen, but there must have been some correlation that SST anomaly patterns in May are more likely to repeat themselves in the following winter.
Going back to the warm September / mild winter relationship - for a high September CET, it would normally be the result of high pressure centered over Central Europe and low pressure areas stalling to the west of the UK - it must be that when this pattern occurs in September that northern blocking is unlikely to establish itself in the following winter, and low pressure areas stalling out west are more likely to be followed by low pressure areas tracking SW-NE in the following winter. The warm September = mild winter correlation looks like one of the things that are a bit like the May SST anomaly pattern being more likely to repeat itself in the following winter.
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WYorksWeather Yes we are definitely on course for one of the warmest first halves of February on record as listed in the post that Roger J Smith posted. With the immediate forecast for another week still mild, we look on course for one of the warmest 31 day CET periods on record in January and February from January 21st until February 20th. The record is 8.0 from 2002 as in Roger J Smith's post, and when you factor in that the CET for the last 23 days is around 7.6 or something, we look to come very close to an all time record.
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Weather-history August 2012 was slightly above average for the CET, and had quite a warm spell mid-month, though the month was still often unsettled though not as wet as June and July. Summer 2012 had a cool and wet June and July, but then turned warmer in August; whereas summer 2014 was the opposite, that was generally warm in June and July but turned cool in August.
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Mike Poole And in recent times in as much of a fashion as this year, the warm September = mild winter correlation also well and truly worked after Septembers 2021, 2016, 2006 and 1999. On top of that, winter 2005-06, given the pattern that set up that winter, and the fact that the really cold air never quite made it to the UK, could have been an outcome that was contributed to by a fairly warm September (15.2 in 2005).
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Kasim Awan Is the current number of 6*C+ CET Februarys in the last 13 years a record for such a period?
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Weather-history Well after previous very warm Septembers (CET 15.5 and above) I think that all the following winters were mild. Now looking at Septembers with CETs over 15*C the only times that I can think of where the warm September = mild winter correlation did not work too well, are Sep 1958 (15.1) that did go on to produce a cold January in between average conditions in the rest of the winter, and Sep 1961 had a CET of 15.2 that did go on to produce a significant cold spell in December which lasted into early January, and there was again another significant cold spell in late February and through most of March, though it did get milder in between these two cold spells. I can also think of Sep 1929 (15.3 CET) that did go on to produce a cold February though the winter was largely mild before that. Other than that, I can think of "not a lot" from a cold perspective in any previous winter following any September above 15*C CET.
Records show a fairly equal mix of colder and milder winters following a September that is cool or average CETwise, but the records certainly show that it has always been very rare to get colder winter weather after an anomalously high September CET. I think that the further above average the September CET is, the worse it bodes for cold conditions in the following winter, and other than the above examples, I think that the warm September = mild winter correlation appears to have almost always previously worked, barring those few exceptions above.
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Drifter Or rather looks like the nightmarish mild Januarys of 2007, 2008 or 2020.
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Derecho I do not think that it is clear that there is any trend between October or November as to the sort of winter that follows, or it is certainly far less clear cut than the warm September = mild winter theory.
March 2024 C.E.T. and EWP forecast contests
in Spring Weather Discussion
Posted
Roger J Smith In your list of warm February to March periods, 2018 is listed. That is definitely incorrect, as 2018 definitely did not have a warm February to March period. Both February and March of that year were below average (on the 1961-90 scale as well), so 2018 is definitely a hot summer that was not preceded by a warm February to March period.