North-Easterly Blast

Please keep on topic. This thread is to do with the possibility that this winter may go pear shaped, I mean do a 96-97 or 01-02, start off with a rather cold December and then be a zonal Bartlett disaster in Jan and Feb, not for discussing totally very mild winters like 88-89, 89-90, 97-98, 06-07 etc.

It has been raised by a number of people that December will be OK and give us the coldest weather of the winter this year, but then the months of January and February will be nothing but a real stinker of flat jet zonal Bartlett dross, so I am questioing whether this winter is likely to go pear shaped? Hear are some previous examples: 2001-02: This was totally and utterly unforgettable. December 2001 was mainly anticyclonic and cold with frequent frosts but little snow for most areas and a particularly cold frosty spell began late in the month and continued into the New Year, but it all went horribly wrong and the rest of the winter and early spring were a zonal Bartlett disaster. 1996-97: Another pear shaped winter only five years earlier, and one of the most pear shaped winters on record (see below for the other) After a cold second half to November, December was cold and mostly dry, and dominated by cold, easterly weather with some snow at the end of the month and a particularly cold spell then lasted until 10th January 1997, but it all went belly up after Jan 11th and February and March were very mild and dominated by persistent flat jet zonal Bartlett conditions. This winter would have been a pretty good winter but the awful mild Bartletty February spoilt it. 1944-45: This was, with 1996-97, the other of the most pear shaped winters on record; December was mixed to begin with, but then saw a cold, frosty foggy spell later on and this led into a very cold January, with frequent snow and severe frosts, but by the end of January it all went horribly wrong, and February and March were very mild, and very similar to Feb and Mar 1997, and this winter in fact featured the largest rise in the CET from January to February in the entire 348 year long record. You could also say that winter 1981-82 went pear shaped, as the really cold weather was over by mid January, and February wasn't much to write home about, although at least it wasn't as mild as 1997 or 2002 and did feature some colder weather after mid-month. Some organisations including the Met Office seem to be suggesting that this winter will likely do a 2001-02. I am not so bothered about persistently cold weather during December as long as it is cold over Christmas as in December more things happen and you are busier getting ready for Christmas, whereas in January and February I find it awful not having any cold weather to look forward to, like in years such as 2002, when life is much quieter and Christmas is out of the way. It is difficult to pin it down to La Nina bringing pear shaped winters, or even very mild ones, as winters 1996-97 and 2001-02 were not La Nina winters, they saw neutral ENSO conditions. One thing worth mentioning is that winters 1954-55 and 1955-56 were moderate La Nina winters and were cold overall especially during February. Also by the way winter 1995-96 was also a weak la Nina winter, and a weak to moderate La Nina was in place during 1984-85 and 1985-86, so it is not entirely true that La Nina conditions are bad news for our winter. A moderate to strong La Nina coincided with a very mild winter in 1988-89, and also pretty mild winters in the late 90s, but neutral ENSO winters still brought stinkers in 1989-90 and 2001-02. I would love to hear anyones thoughts on whether this winter will be another one to join the above list of pear shaped winters (01-02, 96-97, 44-45 etc). We had two in a short space of time in the last 11 years, and when you look at the CET list pear shaped winters of the 44-45, 96-97 and 01-02 type have never been that common.

December is the winter month that, since 1988, has not warmed or altered much from what it was for the whole of the 1900s, we had two pretty cold Decembers in 1995 and 1996. Many Decembers of the 1960s were pretty cold but apart from one off years such as 1950 and 1981 no other decade in the 1900s saw Decembers much colder than most Decembers in the last 20 years. Although Januarys 1991, 1997 and 2001 were quite cold none of them saw any real major cold spells and significant snowfall, plus late Jan 1996 saw a cold easterly and snowfall in the east, we have to go back to 1987 and 1985 to find a truly cold wintry January or any prolonged major wintry spell during January. We did have a truly cold wintry February in 1991, and Febs 1994 and 1996 were pretty cold overall with a number of snowfalls, and there have also been some less severe wintry spells and some snow in the Febs of 2001, 2004 and 2005, so February has done slightly better than January but many Februarys of recent times have also been real stinkers especially late 90s and 2002. It would be great to see a prolonged wintry spell in either January or February. Feb 2005 came close but it lacked any real cold and lasting snow cover.

One thing worth mentioning is that the cold winter of 1995-96 was a very weak La Nina winter, and the winters of 1954-55 and 1955-56 were moderate La Nina winters, and they were cold overall especially during February. I know that the very mild 1988-89 winter was a strong La Nina winter, but the very mild 1989-90 winter saw a neutral ENSO phase. It is also worth pointing out that the winter of 2001-02 that saw prolonged unusual mild spells in Jan and Feb was also a neutral ENSO winter. So with the ENSO status of all these winters mentioned, it is difficult to see any correlation of how La Nina conditions influence the British Winter. Yes, we have had one disaster in 1988-89 with a strong La Nina, but we have also had disasters in 1989-90 and 2001-02 with a neutral ENSO phase. It does not take a brave call of the Met Office to predict a warmer winter than the 71-00 average, as that is what most winters since 1988 have been, but I see from the top two paragraphs of this post that it is difficult to see that moderate to strong La Nina winters encourage prolonged mild spells. Another thing worth considering is that the weather patterns this autumn have been much different to the patterns that have often occurred in recent years. October was the driest for 12 years, and a big change from the wet Octobers of recent years. September did not feature the heatwaves / Euro High that has been the case in many recent years. November also looks likely to end up with a CET close to the long term average, and also the summer this year was cooler than in many of the last 20 years. So, all this does give some hope that the weather patterns this winter may differ from recent years, although it may not be a particularly cold winter, it may be at least colder than recent years.

Many thanks for your comments and information to this thread, thundery wintry showers. It is rather odd how snowless Novembers 1989-1992 were, despite them not being exactly mild and featuring NW'ly cyclonic spells at times. Thundery wintry showers or anyone else correct me if I am wrong. In the 1980s, Novembers 1981, 1983, 1984, 1986, 1987 were all snowless I believe. The 1970s did not see much in the way of notable cold spells and snow in November, despite only two of them (1970, 1978) being above average CETwise. Nov 1978 after a very mild first three weeks was very chilly in the final week with frosts and fog but no snow. I do not know of any Novembers in the 1970s that saw noteworthy snowfall. From the charts I can see that Nov 1977 featured many cold N / NW'ly spells after mid-month, and did this month actually see any snow? I do not know myself what snowfall was like this month. The final week of Nov 1973 was very chilly and frosty but no snow. The main question I am asking, is what 1970s Novembers did, and when, see snowfall? Many Novembers of the 1960s were certainly on the cold side. As mentioned above the Novembers of 1962, 1965 and 1969 were all cold Novembers and all produced significant snow events. There was also a northerly in the final three days of Nov 1964 that gave some snowfall to places. Novs 1966 and 1967 were also pretty cold (1*C+ below average CET) but I am not sure what snowfall was like in either of those two. Going back to the 1950s those Novembers, apart from the notably cold one in 1952, were not brilliant for cold spells and snow either. There were however, a few cold foggy spells in those Novs such as in 1958.

The Nov 2001 event that you mention was a similar pattern to Nov 2004, where a generally mild month produced a short lived northerly. Going back to Nov 1990 the final ten days were also quite chilly and the charts around the 23rd / 24th Nov 1990 also look rather similar to this last Sunday's Nov 18th 2007, and a number of places saw falling snow and a negligible cover in a few places. Thundery wintry showers; was there any snow anywhere from a similar setup in November 1990?

Well after a failed Greenland HP block around the 10th of this month and another attempt at a Greenland HP block this weekend that at least looks likely to fail for a sufficiently full blown northerly blast to give a significant late November cold spell, I am starting a thread of November cold snaps / snowfalls of the past. The Novembers so far this decade (the 2000s) have had relatively few significant cold spells and snowfalls, only the second half of Nov 2005 stands out as providing a significant cold spell with frosts and a decent northerly with snow in places on the 25th and 28th of that month, and also Nov 2004, although a mild month overall produced a short lived cold northerly with slight snowfalls across the north Midlands on the 18th. Correct me if I am wrong but the Novembers from 1997-2003 were all snowless I believe. In the 1990s Novs 1993 and 1996 were pretty good for cold spells and snow, but the rest of the 90s Novembers were poor. Nov 1993 gave a notably cold easterly for the time of year from the 20th onwards with some snow in many areas on the 21st, 22nd and 24th. Nov 1996 featured a cold second half with a week's spell of cold northerlies from the 18th - 23rd and a polar low that gave heavy snow across the NW Midlands and Staffs, and the Yorkshire Pennines on the 19th, and a transistional snow event on the 24th before it turned to rain. Is it true that the Novembers from 1989-1992 were snowless, even though they were not exactly mild. Nov 1989 was cold, frosty and anticyclonic late on, Nov 1990 was rather cold from the 20th and unsettled at times, and I do not know if that Nov produced any snow at all, does anyone know if it did? The 1980s, apart from 1985 were not brilliant for cold November spells despite having much colder winters overall. Nov 1985 was notably cold with northerlies / easterlies and frosts and snow at times. Late Nov 1980 also gave a cold northerly with snow in places. The 1970s, although most Novs that decade were not especially mild gave relatively little cold and snow in November. Although Nov 1978 was very mild until the 24th the last week was very chilly with severe frosts and fog. Nov 1977 also gave some cold northerly spells and a little snow after mid-month, and the final few days of Nov 1973 were cold with severe frosts. We really have to go back to the 1960s to find a run of cold Novembers. Five Novs that decade were greater than 1*C below average. Nov 1965 was notably cold with snowy spells. Nov 1962 was cold from around mid-month onwards with frosts and a fairly widespread snowfall around the 18th. Nov 1969 was also cold and a pretty snowy month with the last week particularly cold with snow as far south as the Midlands on the 16th/17th and more snow on the 25th and 28th/29th.

You missed out 1997 Kevin. That December had a warmer second half than the first, first half 5.7, second half 5.9. To work it out in a 31 day month I input the first 15 daily CETs plus half of the daily CET of the 16th of the month and divide the total by 15.5. I use the same method for the second half of the month by averaging the CETs for the 17th-31st plus half of the figure for the 16th. An example is if the daily CET for the 16th is 5.0, then I input 2.5. I think 1969 is wrong. If I am aware the first half of Dec 1969 is 3.9 and the second half 2.6. Correct me if I am wrong.

A question for Kevin Bradshaw; December is another transistional month where in the majority of years the second half will be colder than the first, like Sep/Oct/Nov. I would be grateful if you could post a list of years where December had a warmer second half than the first half? I can start this list off myself that I know all five consecutive Decembers from 1987-1991 had a warmer second half than the first, and before that 1980, 1982 and 1983, and since 1991, 1997 and 2002 had a warmer second half.

Hadley have put down October 2007 as having a CET of 10.88*C, or 10.9 rounded up. By that figure, in the last 100 years, there were 24 warmer Octobers, of which 19 of these happened in the last 50 years, highlighting the warming trend of October since the 1950s, and that it began 30 years before the other months of the year. There were also two Octobers which had the same CET as 2007, and the other 74 were colder. In the entire 348 year CET record there were only 50 warmer Octobers, still of which 19 of these happened in the last 50 years, and there were only 31 warmer Octobers than 2007 in the first 300 years of the CET record, so October 2007 was definitely still a warm one by historical standards, even though it was only 0.3*C and 0.5*C above the 1961-90 and 1971-2000 averages respectively. Oct 2007 was however just over a full degree warmer than the long term mean for the first half of the 1900s. All these facts underline the warming trend seen in October since the 1950s very sharply.

Kevin (Mr Data); Back in the spring you wrote a list of years where the second halves of March, April and May were colder than the first half. Logic suggests that in most years the second half of October should be colder than the first half. I do not know of the last time that October had a warmer second half than the first half, although 2004 and 2005 came very close. I would be grateful if you could post a list of years where October had a warmer second half than the first.

Well Hadley have confirmed as 13.8*C for the September 2007 CET. Certainly not what you would call a cool September, but one comfort is that it bucked the trend of recent years a bit. Philip Eden points out that it was the fourth most northerly September in 135 years of records, and yet it still ended up a shade above average for the CET, so post 1997 Stage 2 GW UK is well and truly still with us IMO. Sep 2007 should have had, given the synoptics, a far lower CET than it actually had. Logic would have suggested that it should have been a proper cool September at least like 1993 (12.4) or even 1986 (11.3), but yet again it wasn't and failed to produce the negative anomalies in the CET that it ought to have done. August 2007, despite having frequent northerly winds and being the third or fourth most northerly on record should have been cooler than it actually was, like the 14.6 in 1993 or possibly cooler still, but it wasn't. Anyone thinking or saying that the last three months are a break in the post 1997 GW UK is deluding themselves when the synoptics of Aug and Sep 2007 should have produced much cooler CETs than they actually did, so it still seems in this issue that it looks almost impossible that we will ever get a winter like 1995-96 let alone a truly severe one.

I wouldn't exactly call this year as looking like 2006 in reverse. 2006 only had a rather cool first quarter to the year, and in late March mild weather came along and was consistently above average from April onwards, so the first half of 2006 was far from cool. 2007 has seen a very warm first half, and the warmest first third to a year on record, and July and August have been rather cool, but September isn't exactly going the same way so far, we have got to the 19th and the CET is about 1*C above the long term mean so far, and there is now very little chance of a below average CET for September, and it will take a pretty cool spell with some cool nights in particular like Monday night of this week to enable us to achieve a close to average CET this month. It yet remains to be seen as to what the final quarter of this year (Oct-Dec) will bring, and no-one can accurately predict this in detail in advance, but I agree with you that in May it looked as though 11*C+ was certain for the 2007 Annual CET, but after a relatively cool summer it is not looking a realistic possibility that 11*C will be hit.

There is certainly a correlation between warm Septembers and mild winters, especially in the modern day. It was certainly true for the 1900s and up to present that a warm September certainly increased the chance of the forthcoming winter being milder than average. Here we go: Septembers of 14.5 or greater and the following winter CET since 1900: 2006: 16.8 Winter 06-07: 6.4 2005: 15.2 Winter 05-06: 4.2 2004: 14.9 Winter 04-05: 5.2 2000: 14.7 Winter 00-01: 4.5 1999: 15.6 Winter 99-00: 5.4 1998: 14.9 Winter 98-99: 5.4 1991: 14.7 Winter 91-92: 4.6 1989: 14.7 Winter 89-90: 6.2 1985: 14.6 Winter 85-86: 2.9 1981: 14.5 Winter 81-82: 2.6 1980: 14.7 Winter 80-81: 4.5 1961: 15.2 Winter 61-62: 3.5 1959: 14.9 Winter 59-60: 4.6 1958: 15.1 Winter 58-59: 3.5 1949: 16.3 Winter 49-50: 5.1 1947: 14.9 Winter 47-48: 5.1 1941: 14.5 Winter 41-42: 2.2 1934: 14.6 Winter 34-35: 6.1 1933: 14.9 Winter 33-34: 3.2 1929: 15.3 Winter 29-30: 4.6 There were 20 14.5*C+ Septembers in the last 100 years, and four of them have led to cold winters, and two others slightly below average. The other 14 warm Septembers all led to mild winters, or average at best. Also before anyone mentions the warm September = mild winter theory not working in 1981 and 1985 I will point out that those two Septembers were not entirely in the same mould as recent warm Septembers. Sep 1981 was also a very wet September, and certainly not the warm anticylonic type of recent years, and Sep 1985 had a much warmer second half than the first half, and indeed the last time that September had a warmer second half compared to the first half, whereas most recent Septembers have often seen warm or even hot dry weather in the first half. There is certainly a correlation in the modern day between a warm September and a cold winter. Whatever the summer weather pattern has been in the last ten years, whether it be very hot (2003, 2006) or reasonably warm and dry (1999, 2005), or warm and wet (2004), or rather cool and wet (1998, 2007), we just get stuck in a rut of a warm and anticyclonic September.

Looks like the modern post 1997 UK climate is showing its ugly faces again, with the GFS and most other models showing warm high pressure glued slap bang over the UK until this time next week at least, and the next seven days' forecast is warm. We just do not seem to be able to achieve a CET below 14*C in September any more, and we have not had a wetter than average September since 2000. September has become one of the main months of the year to be affected by UK Climate Change over the last ten years, and warm high pressure has just become the default September setting. We have cracked one trend this year, and August has finally broken the trend of recent years of never being able to record a CET below 16*C, and September just needs to buck the trend. A return to cooler and wetter Septembers will more than likely lead to a switch back to a climatological pattern that leads to colder winters. As long as Septembers continue warm and dry like recent years it is difficult to see a cold winter in the UK, or the winter patterns to deverge away from the patterns of recent winters.

Hadley have released their official August CET. It is 15.42*C or 15.4 rounded down. To be accurate last year, Aug 2006, was 16.06*C, or 16.1 rounded up. I am in doubt as to whether 15.4 is a possible mistake and as to whether it was that cool, as they had it at 15.7 on the provisional figures up to yesterday. If Hadley's Aug 2007 15.4 verifies, then it makes the CET for summer 2007 as 15.23*C, or 15.25*C to be exact, and the coolest summer since 1998, and summer 2007 is therefore below average on the 61-90 scale as well as the 71-00 scale. Since 1988 only the summers of 1993 and 1998 were cooler than 2007. Summer 2007 just reminds us of how cool many summers were in the 1960s, 1970s and 1980s. Between 1960 and 1974 there was not even a single warm summer (16C+ CET), and most summers of those 15 years were cool, with only 1967 and 1969 being slightly above average. After the very warm summers of 1975 and 1976 had passed there began another run of cool summers from 1977-1981 (all sub 15*C CET), then a blip again with warm to very warm summers in 1983 and 1984, then it turned cool again with another four cool summers on the trot from 1985-1988, then from 1989 onwards many summers have been above average with partiularly warm summers in 1995, 2003 and 2006, and 1989 and 1997 were warm too, and only 1993 and 1998 bringing summers that were below average, and now 2007. Summing it all up, in all the decades of the 1960s, 1970s and 1980s, the chances of getting a cool summer was far greater than getting a cold winter, as in actual fact the 1960s winters, apart from 1962-63, were not that remarkably cold, although 68-69 was pretty good. From 1970 onwards the only cold winters were 1978-79, 1981-82, 1984-85 and 1985-86, and only 76-77 and 86-87 that were below average at all.

Yes, Kevin I know about your point, especially as January 1981 was one of the most northerly Januarys on record but it still ended up above average at 4.9; but when you look at that month's charts properly you see that the northerlies often came from round the northern flank of a displaced Azores High (which is still a fairly mild source in the winter) and rarely from within the Arctic Circle. So, most of January 1981 synoptics were certainly not cold. On the other hand, we have had a few months in recent years that should have been far colder than they actually were. February 2005 had frequent northerlies and then a full blown easterly in the last week or so but it still ended up a shade above average at 4.3, and Feb 2005 synoptics should have produced a much colder month, and given the synoptics I would have expected the Feb 2005 CET to have been a cold one, more like the 2.5 in Feb 1996. August 2006 had north or north-westerlies for most of the month but its CET was close to average at 16.1, and those synoptics should have produced a much cooler month (although not quite the 13.7 like Aug 1986 as the northerlies were never from far north). Now August 2007, despite being the fourth most northerly on record still had a CET not much below average at 15.65, and given the synoptics it should have been as cool as 1993 (14.6) at least. Nov 2005 actually did give us some hope, as the second half was around 3.5 below average, and so did March 2006, which up to the 23rd the CET was running at only just above 3*C, and only the warm south / south-westerly synoptics of the last week made the CET less outstandingly low. July 2007 didn't do so bad CETwise for the synoptics, frequent low pressures and no or very few anticyclonic / S / SE'ly types, and ended up 1*C below average (with few spells of low pressures pulling into Scandy and dragging down proper northerly flows) but in Aug 2007 cool synoptics have failed to deliver a truly cool CET, when Aug 2007 synoptics were really as cool as Aug 1993 synoptics, which that month featured frequent anticyclones to the west of Ireland and northerly spells just like 2007.

Philip Eden has confirmed the August 2007 CET as 15.65*C. He also states that it was the equal fourth most northerly August in 135 years of records, and another striking aspect from this eveidence is that it still managed a CET only very slightly below the long term average, so post 1988 / 1997 GW UK is still with us IMO. Logic would say that the fourth most northerly August on rcord should have produced a cooler monthly CET than it did, indeed a good 1C to 1.5C cooler, but it didn't. So anyone who says that summer 2007 is a break away from Stage 2 post 1997 UK warming is wrong when August 2007 synoptics are looked at. When I look at the MSLP chart for August 2007 I would have expected an August at least as cool as 1993 (14.6) or even cooler. Had August 2007 synoptics occurred 20 to 30 years ago then they would have almost certainly produced an August CET in the mid 14s.

The modern UK climate will really be showing its ugly face if we do not get a below average August or at the very least a close to average month. Looking back at the CET list there is a bit of a link / correlation that a cool July (15.5 or below) is often followed by a cool August, or an average one at the most. Cool Julys (15.5 or below) are rarely followed by an August that is above average at all. Since World War Two, only in 2000 has a cool July been followed by an August that was above average at all. Prior to this we have to go back to 1942 (through 18 cool Julys) to find an above average August after a cool July.

The July 2007 Hadley CET was actually 15.23*C, or 15.2 rounded down. July 1993 was exactly 15.20*C. So July 2007 is actually the coolest since 1993, not quite the joint coolest since 1988 with 1993.

Interesting stats there Kevin; I will broaden the information and state the number of below both 71-00 and 61-90 for each month since Stage 2 UK warming began in Jan/Feb 1997: 61-90 71-00 January 1 1 2001 February 1 2 2006 (2003) March 2 2 2001 2006 April 3 3 1998 2000 2001 May 0 0 June 2 1 (1997) 1999 July 5 5 1998 2000 2002 2004 2007 August 0 3 (1998 1999 2006) September 1 1 2001 October 5 4 (2004) 1997 2000 2002 2003 November 2 2 1998 2005 December 2 4 2001 2005 (1999 2003) Years below only one scale of averages are shown in brackets, and it should be noted that June and October actually showed a cooling trend from 61-90 to 71-00. Despite the 1960s being a very cold decade overall, Octobers tended to be on the warm side, and there were no really cool Junes in the 1960s. Below here are the averages for each month in the "modern" climate after Stage 2 warming began in February 1997: Jan 5.1 Feb 5.4 Mar 7.0 Apr 9.0 May 12.2 June 14.9 July 16.7 Aug 16.9 Sep 14.8 Oct 11.1 Nov 7.5 Dec 5.2 From the above, it is true that July is the month that has warmed by the second least amount since 1997, with December the month that has shown the least warming from long term averages. February has shown the most warming, with September in second place.

Not sure that I would rate Julys 2006 and 2007 as contrasting months to the same degree as August 1911 and 1912 were; July 2007 is certainly not going to be anywhere near record breaking cool for July, and not record breakingly wet either, and July 2006 although the hottest on record either, was dry yes but not exceptionally so at 41mm. In fact July 1999 was a drier month than July 2006, and believe it or not the Julys of 1977 and 1979 were drier months than July 2006 even though they were average to slighly below CETwise.

For around the past three years Kevin Bradshaw has been writing reviews on the UK's major past weather events, including a database of reviews on TWO, and many reviews and reports on the Historic Weather section of this forum, and also on the UK WeatherWorld Past Weather section. Recent months have included Kevin writing reviews / special reports on the severe winters of 1946-47, 1962-63 and 1978-79, and also the notable cold spells in 1985, 1986, 1987, 1991, 1995-96 and many more, and a most recent review on the cool summer of 1954. In all of these reviews he has written a detailed summary of the weather events together with selected historic charts from the days of the coldest spells of the above winters, and the CETs for the coldest periods of each of those winters. As we all know that the 12 months from May 2006 to April 2007 was the warmest ever 12 month period in the CET series with a CET mean of 11.63*C, hugely beating the old record of 11.07*C set in Nov 1994 to Oct 1995; and given that exactly this time last year we were nearing the end of the first highlight of the above record 12 month period, the hottest July and hottest ever calendar month on record, I would be most grateful if Kevin Bradshaw would be willing to write a similar review / special report on the May 06 - April 07 record warm 12 month period, to place in the Historic Weather section of this forum, set out in a similar way to the reviews of the severe winters such as 1978-79, the cool summer of 1954 etc, with selected charts from the warmest spells of the last 12 months like last July's heatwave, the very warm spells in Sep and Oct last year, the very mild spells last winter, and the very warm spells in April. The report should also detail that we saw July, September and April set new records on the CET, and October and January were also near record months, and also the whole autumn set a new CET record and that the other three seasons also were in the top five warmest ever. An even more notable point could be that the report details that August 2006 still ended up with a CET close to average despite having northerly winds over the UK for most of the month, when the synoptics should have produced a much cooler month! A review / special report written by Kevin Bradshaw on the record warm 12 months from May 2006 - April 2007 similar to his other reports on major past UK weather events would be a great addition to this forum's Historic Weather section, as this (the UK's warmest year ever in 348 years of records, by a huge margin of 0.5*C!) has now become one of the most major events in the UK's weather history equally as much as the exceptional winter of 1962-63.

Throughout the last 100 years, after the 18 warm Septembers with CETs of 14.5 or greater, there was only one that was followed by a particularly cold winter (1985-86), and only two other occasions where a warm 14.5+ September was followed by a winter that was below average at all (1958-59 and 1961-62). All the other 15 warm Septembers were followed by mild winters, or average at best. So by this measure it is the truth that a warm September decreases the chance of the following winter being colder than average, and increases the chance of it being milder than average. Whereas it is difficult to see any correlation the other way round (a cool September increasing the chance of the following winter being colder than average), it does not always work this way round. Whilst it is not uncommon to see a mild winter after a cool September, it is very rare to see a cold winter after a warm September.

Kevin; It will be less meaningful to talk about Julys and Augusts having a cooler second half than the first as these months should be fairly static all the way through. Whereas March-June should more often have a warmer second half than the first. So what have we seen this year; A cooler second half of March than the first half, for the first time since 2000. A cooler second half of June than the first half. A cooler first half of May than the second half of April, for the first time since 1996. It must take you hours to work out past months that saw quirks in the CET between each half, Kevin.