North-Easterly Blast

The May CET of 11.9 that has just been published is actually 11.87 rounded up. So May 2007 was actually 0.3*C below the average for the modern day post 1997 average, about average by the warmed post 1988 average, but still 0.6*C above average by the long term 30 year 1971-2000 standards.

As June is still a transitional month as regards temperature, and the end of the month should be expected to be warmer than the start, I have a question for Kevin B (Mr Data), as to the years in the past where Junes had a cooler second half compared to the first half? I believe last year was one, and 2004 certainly was, and 1997.

Stratos Ferric; This May has been very unsettled but hardly what I would call coolish. The May CET is likely to be around 12.0*C, which is about average for a post 1997 May, but still 0.7*C above par by the long term 30 year 71-00 average, so this May has been nothing that can even be reasonably described as cool by recent standards!

There have been two major wet periods this month - one around mid-month and another one this last week, but only one was cool. The unsettled spell during mid-month was associated with air of a mainly tropical maritime origin due to winds mainly from the south/south-west, and no northerly from a cold source, and so the mid May wet spell was not cool, and in fact overnight temps remained largely above average. Whereas the unsettled spell this last week was cool, as it was started by a NW'ly and then a low pressure crossed southern UK and dragged northerlies across the UK from reasonably far up north, (although not exactly way up into the Arctic) and so this last week's wet spell was cool, and in fact according to the daily CETs it has seen some of the lowest daily CETs in the final week of May in any year in recent decades, only years such as 1975, 1962 and 1936 have seen significantly cooler spells in late May than this last week according to the Daily CET Data list.

January's warming trend also began in 1988, along with February and March, April warmed to a lesser degree in the 1990s but did not join the "bandwagon" until around 2002. May also joined the bandwagon around 1998 (although there were warm Mays in 1989, 90, 92 there was a run of average to cool Mays from 1993-97). June showed no warming trend until 2003. July and August are less easy to pin down, but there was some easing up from 1989 onwards. September showed no warming trend until around 1997. November showed no warming trend until around 1994 (although there was a run of mild Novembers in the early to mid 1980s). October and December are the two months that in actual fact joined the warming bandwagon before the annual CET warming trend started in 1988 (though the warmth of the post 1997 era is far more marked and consistent than the relatively modest warmth of the 88-96 era). October joined the same warming bandwagon back in the late 1950s (around 1957-1959) and December joined the warming bandwagon around the early 1970s, with a run of mild Decembers in the 1970s and 1980s and in fact a slight easing back since then.

Nick H; You have missed one out. Between 61-90 and 71-00 October showed a cooling trend of 0.2*C. This is due to the fact that despite the 1960s being the coldest decade since the 1880s overall, the Octobers of that decade tended to be on the warm side. It is true to say that until 2003 June showed no sign of a warming trend, indeed with a run of mostly average Junes throughout the 1990s and up to 2002. The last four years are showing signs that June possibly joined the warming bandwagon in 2003. If this coming June comes in above 15*C, and certainly if it is anything like last year or 2003, then we can certainly say that June joined the warm bandwagon in 2003, but if June does manage to be a closer to average month and at least come in below 15*C, then we can possibly say that it has not developed a warming trend. Despite the lack of really warm Junes in the 1990s, it is true to say that we have not had a proper below average June (more than 0.5*C below) since 1991, which that was in fact one of the coolest Junes on record. There were two notably cool Junes back in 1972 and 1977, and those of 1985 and 1987 were quite a bit below average, and June 1990 was also relatively cool.

Craig Evans; how can you say that this month feels cool; the CET is currently 11.9*C, above average already, just fairly typical so far by Mays of recent years. In relative terms this month is still not like August 2006. which was a month close to the long term average overall but relatively cool by recent August standards. This May so far is still not even cool by the standards of recent years.

Thanks Kevin once again for information on years that produced Mays with a second half cooler than the first half. To re-cap once again for all the spring months I would also be grateful if you could post again the years which produced a March with a second half colder than the first half and years that produced an April with a second half colder than the first half, as this information seems to have disappeared from the forum now.

Kevin B (Mr Data); Would it be possible to list the years where Mays had a cooler second half compared to the first half? You did this for March and April. For a start, last May had a cooler second half than the first and so did May 2000. Another point of question of mine now is with all this rain we are having now and the fact that last May was very wet has May now joined the "wetter trend" bandwagon like October has done over recent years. There has only been one instance of two consecutive Mays recording 100mm or greater of rain, and if this May does record over 100mm, then it goes to show May is showing a wetter trend like October is.

It is now getting to the time of the year where northern parts of the UK at least do not get properly dark at night and these areas are actually a lingering twilight. For it to go properly dark, the sun has to fall 12* below the horizon. When the sun is between 0* and 4* below, it is Civil Twilight, referred to as the time when the sun is below the horizon but outdoor activities can still be performed with adequate light. When the sun is 4* to 8* below the horizon, it is Nautical Twilight. This is when objects and the outlines of buildings and trees can be seen, but it is dark for practical purposes, and too dark to see to do outdoor activities. It is actually still possible to read a newspaper outside in this type of twilight. When the sun is between 8* and 12* below the horizon, the only light that is visible is sky illumination, and the twilight can be seen in the north-western sky around this time. It takes the sun to go 12* below the horizon for the sky to go completely dark and be free from twilight. Parts of the UK north of the Middlesbrough area are in the 54.5* N zone, so areas north of this see twilight all night at the time of the summer solstice. In the Shetland islands, around 61* North, there is enough twilight to read a newspaper by at 1am in the morning.

What is even worse with this month's setup is that northern France and Germany have been far warmer than Spain and most of the Mediterranean, a warm pool of 10+850hpa air has been floating around the northern France / Germany area all month, with hardly any 10+850hpa air anywhere else further north from Africa. This month has just seen almost persistent high pressure sat over Central Europe propped up there by a semi-permanent Iberian trough / low over Spain. Highs over the UK have attempted to retrogress to form a Greenland High on two occasions this month, but shortwave low pressure areas have prevented it. We were also stuck in a pattern of a permanent anticyclone over Central Europe (Euro High) held up by an Iberian trough for two solid months in June / July of last year.

A high pressure moving north to cover the British Isles is therefore not a Bartlett High. These Azores ridges will give warm dry conditions in summer and frequent fogs in winter, sometimes with temperature inversions such as in the 1991-92 winter and in early February 2006 and in December 2006. Also what is the current situation with stratospheric warming / cooling? Has there ever been significant stratospheric warming / cooling events before in the past in years gone by?

Many thanks for quoting dates when a summer Bartlett High occurred. I started this thread to question why we hardly ever see weather charts in the summer months that resemble / look virtually the same as the Bartlett winter charts of 1988-89, Jan/Feb 1990, Feb 1998, Jan/Feb 2002 and Jan 2007. In winter in the UK, well nowadays and for the last twenty years a Bartlett High and an Icelandic low and SW'lies across the UK has become a familiar chart, but does anyone else know of any more that occurred in the summer. I find it so strange as to why it is rare to see a weather chart in the summer months that show a Bartlett High / Icelandic low and SW'lies over the UK. I mean to say that weather charts in the summer months often feature an Azores ridge across the UK, weak lows to the north and to the south of it, or a more meridonal Atlantic flow with lows over the UK rather than a flat jet and a Bartlett High. Why is this? In the past cooler than average summer months such as the very cool wet July of 1988, have often been characterized by "cold zonal" looking charts, and a meridonal Atlantic flow, similar to the "cold zonal" setup in January 1984, but why is it that summer months are rarely charcterized by "mild zonality" and a Bartlett High and SW-NE tracking lows across the UK, similar to the setups of last winter 06-07, and the very mild winters of 88-89, 89-90 and 97-98.

Gavin P; July 1993 wasn't that bad a month was it. It was nowhere near as awful as July 1988. At least July 1993 although cool overall it wasn't excessively wet overall with rainfall overall similar to July 2002 or even a bit less. It featured a warm spell at the start, but it then became much cooler and changeable but there were some fine days at times. It is something of note that when you look at the CETs of Julys 1978 and 1980, and the rainfall as well and the general weather pattern, these two Julys had much less rain than July 1988, those cool Julys were certainly not as awful as July 1988 as there were some spells of fine, quite sunny but cool weather at times. CETs do not always tell the tale on how awful a summer month is. Julys 1978 and 1980 may have had similar CETs to July 1988 but July 88 was a far wetter month. Even more so, look at August 2004 rainfall (156mm), this even exceeded the rainfall of July 1988 (139mm), and the coolm summer months of July / August 1978, July 1980, July, August 1993 were all much drier months than the warm August of 2004. I share the same feelings as you about September, I would love to see a cool wet September like 1993, or even a September like 1995, as I am just sick to death of how warm September has been over the last ten years. There is certainly some truth that a cool wet September, although not guaranteed, does increase the chances of the following winter being cold, as opposed to the sorts of Septembers we have had since the mid 90s.

By variable springs in the 1990s the spring of 1995 was a great example. Although not particularly cold overall, that spring featured frequent northerly outbreaks in April and May and even cold polar maritime zonality in March. Switch Arounds, as Kevin (Mr Data) describes them, where there is a change from spring warmth to winter cold in a few days, featured on many occasions that spring, and it is true to say that those synoptics and the Switch Around scenario are another type of weather that has dissappeared in recent years. It does create interest some of the time, but only so far, to have months recording above or well above average temperatures, but it is boring to death month after month. I have to say that I am sick to death of the current weather pattern we are in now, high pressure glued to the east of the UK giving dry and unseasonably warm weather that is at times more like the summer months. I just find it so difficult to live without more variety than this. It is spring, let's have some switch around scenarios which give great interest weatherwise. Yes, the 1990s did still have some variety weatherwise to get excited about, there was a pretty cold winter in 1995-96, and a severe Feb 1991, and some pretty good varied springs such as 1995, a not really cold winter overall in 1993-94 that still featured some cold snowy spells. Whereas this decade, the 2000s, just seems the most boring decade to write about weatherwise. Another month of interest is April 1998, which featured heavy rains and floods, then an Easter cold spell with frosts and snow in many areas. April 1999, although quite warm overall, still managed a cold northerly outbreak with frosts and snow in places mid-month. May 1997 is another varied month that featured a heatwave at the start with 25*C in many areas then a cold northerly outbreak with even snow in some areas. Whereas, most of the springs this decade have had almost nothing of interest to write about or look forward to, just almost weather dead is the way I would describe them, as have most years all the year round much of the time.

It is also true to say that, very similar to the summer Azores High ridge over the UK, that setup does also occur in winter too. Last December was an example of when a displaced winter Azores High became a mid-latitude ridge over the UK. The winters of 1991-92 and 1992-93 were characterized by a mid-Atlantic Azores ridge displaced NE over the UK with the jet in a zonal position to the north of the UK. Months also like January 2001 and February 2003 featured the Euro High.

Last autumn was dominated by tropical maritime air rather than tropical continental air. The first half of September was mostly tropical continental as the source of the air was from the Mediterranean, whereas from mid September onwards it was tropical maritime as the air was mainly from SW'lies originating from the sub tropical Atlantic.

I think you have got it wrong that we got an almost record June, it was 15.9*C, over 2*C below the record and a full degree behind the warmest of the 1900s in 1976. You also forgot to mention that we got the 4th warmest October on record, and the 5th warmest January on record. 5th warmest summer on record Warmest autumn on record, by a whopping 0.8*C. 5th warmest winter on record Warmest April on record, by even almost a full degree which looks likely. What will ever trigger a trend to some cooler conditions for the UK, no I am not saying that a return to pre 1988 weather is likely to happen well not for many years anyway, as this does look highly unlikely given the patterns that have prevailed for the last ten years in particular, but at least what will trigger a trend for the warm synoptics of the last year to abate their grip?

Looking at charts, a Bartlett High only seems to develop during the winter months. To help anyone understand what I mean I would refer to a Bartlett as a high pressure area that sits over France, Spain or the Bay of Biscay, no further north than the north of France. You only seem to see these patterns develop in the winter months, and you never see a Bartlett in the summer months. Does anyone know why this is? The closest you possibly get to a summer Bartlett with a chart in the summer months resembling a winter Bartlett High is when ridges of high pressure cross southern UK in between lows moving east across the UK giving the north / south split, of rain for the north but drier further south. On the other hand, many people confuse a Bartlett with a Euro High. To explain the difference I would refer to a Euro High as a high pressure area that sits over central or eastern Europe with possibly a ridge over the UK. As Bartletts only seem to develop in the winter, a Euro High seems to be able to develop at any time of the year. A Euro High with a ridge over the UK is what brought the heatwaves of August 2003, July 2006, and of summer 1995. A Euro High has also been largely responsible for much of the warmth of this April. With increased solar radiation by this time of the year, the persistence of the Euro High this month has allowed very warm conditions to build up over the UK and Central Europe. Whereas these type of Euro Highs do occur during the winter months too, such as in late December 1992, February 1993, mid January 2001, February 2003 and this type of pattern also brought the cold temperature inversion of early February 2006. Can anyone explain the reason why only the winter months see Bartlett Highs, whereas any time of the year see Euro Highs?

Through the second half of the 20th Century we have seen two notably severe winters (1962-63 and 1978-79) the first of these was to rival anything as cold as we saw in the Little Ice Age! So, it was possible for cold synoptics to sustain themselves. Only in two winters in the last ten years (2000-01 and 2005-06); neither of those ever featured a Bartlett and / or constant depressions running through the GIN corridor, although the synoptics were never anything that could deliver anything special or prolonged in terms of cold. Again in Feb 2005 easterly synoptics developed although unfortunately at a time when Europe was not that cold, although mid Feb - mid March 2005 still managed a CET that was even 2*C below the 1971-2000 average for that period. If only the subtropical high pressure belt would die or shut down then the UK and much of Europe as well would become much colder, as synoptics would then be able to drive colder air to these areas. How can man's activities have affected the evolvement of weather patterns? Logic would tell me that on average the same weather patterns of the last 100 years and more would still occur today with the charts on average looking the same, with northerlies and easterlies of the same frequency, but even the cold synoptics would deliver much warmer temps than they used to, rather than seeing Bartlett after Bartlett or high pressure glued to the UK or over Eastern or Central Europe. We have even seen this month two attempts at a Greenland High, around the 3rd/4th and 18th/19th, yet on both occasions the block has been unable to establish itself over Greenland due to small low pressure features in the area and so we have been just left with the high pressure moving back to be glued to the UK or Europe, and the Easter northerly went into Scandinavia. If man's activities have warmed the planet, I would have expected that both this month's failed northerlies to still have materialised but still get temps well into double figures, not that man's activites would prevent the synoptics from developing, as you have got to have synoptics like a Bartlett / Euro High before the UK can become warmer. The UK cannot become warmer before those synoptics develop.

The most traditional summer weather pattern is low pressures passing northern UK with ridges of high pressure passing across the south, giving the typical pattern of short settled spells with temps into the low 20s followed by rain or showers as a low pressure passes and then another short settled spell. What happened in July 2006 is that persistent high pressure was often over Scandinavia or Central and eastern Europe and slow moving lows stalled out west, giving a prolonged hot south to south-easterly flow over the UK. The same is true in August 2003 with frequent slow moving anticyclones over or just to the east of the UK, and also in the summer of 1995, as opposed to the traditional summer weather pattern described above.

Are you sure that you do not mean to say that winter 2005-06 was not a particularly cold one because 1995-96 was, and yes 1996 was a cool year. I do not know what you mean when you now start discussing Nov / Dec 2005 relating it to 1995-96.

The shorter lived late Dec 2005 easterly was pretty cold and it did give two ice days to a number of places, and was in fact colder than the much longer lasting and good setup of what should be a cold easterly in late Feb 2005; the mid March 2006 easterly was cold by March standards with some places getting an ice day on the 12th, and even the short lived easterly on 8th / 9th Feb 2007 certainly wasn't that bad, as when looking at charts it dosen't look a particularly cold one; a number of places managed to stay below 0*C on these two days. So in actual fact we have had short lived colder easterlies since the good easterly setup in late Feb 2005.

The truth goes that the period mid-Nov 2005 to mid-April 2006 delivered a colder period that was unusually cold for the last ten years but by no means a 1995-96 winter level of coldness. The only other period that we have had since the mid 90s that was anything comparable to Nov 2005-April 2006 was mid-Dec 2000 to April 2001 when again mild weather was pretty rare during that period, and even in late Jan 2006 we came very close to getting something special in a freeze up when Europe became very cold and we also were close to something special with the "Kettley High" scenario in early Feb 2001 but neither came off and we ended up with just average winters, but by recent years' standards were quite cold. For the 20th Century, 1962 and 1963 were 1740 / 1879 esque years. Nowhere near on the same scale but you know what I mean. More recently, 1996 was the 1962 / 1963 esque year just on a lesser scale. So, help needed. Is the UK warming now Stage Three, or is the last 12 months just an 1879 esque year at the opposite (warm) extreme? Surely it must be possible that it is.

I have to say especially after the last year now I am getting tired of all these persistent warm weather patterns and week after week being characterised by the current pattern, and I am just ready for a change to a wider variety of weather with a better variety of weather charts in the model watching. Goodness knows what the April CET will end up at now, it could well end up almost a degree above the previous record holder. With all this I am now beginning to think if the UK's warming has moved into Stage Three since around this time last year, with just runaway warming and month after month being chartacterised by almost the same pattern almost week after week without a break. I mean to say that although up until 1988 there was no sign of a warming trend in the UK which is when the warming process became first noticed, and UK warming definitely moved into Stage Two in 1997 as the post 1997 warming trend is greater than the modest warming of the 1988-1996 era. One would have thought when looking at the fact that 1879 could end up a full two degrees below the long term average well for since the Little Ice Age anyway, one would think again that a yearly period with annual means 2*C above average was possible, and when you look at the weather patterns that have prevailed in the UK for the last ten years, a 12 month period like we have just had looked bound to happen at some point, but one would think that the UK would go through one off warm periods and they relax their grip. Such as before 1988 an annual CET above 10*C was a once or twice a decade occurrence on average rather than the norm, now well above 10*C has become the norm during recent years. Although I am now, given this month's weather patterns and that the CET looks set to break the old record by a long way (last July and September were only marginally above the old record) I am wondering if the UK's warming has now moved into Stage Three and a similar vein to the last year will persist for another decade or two. The facts are that over the last 12 months the UK has been a full degree warmer than the standards of the last ten years. What will ever trigger a trend for a change in the surface pressure patterns and synoptics for a change to cooler conditions and at the very least, for the current warmth of the last 12 months to relax its grip? When you consider how much synoptics that affect British Weather have varied in the past it only takes the flick of some factor or "driver" of the synoptics for different weather patterns to develop. Synoptics do not only affect British Temperatures, they also affect rainfall as well. In actual fact since October 2004 most months have recorded rainfall in the EWR series below the long term average. Why was 2000 such a wet year, in particular the autumn? Because the synoptics were frequent slow moving low pressures over the UK; the same is true for the last 12 month's temperatures; the last 12 months have been dominated by winds from a southerly quarter almost throughout with few and very short lived spells of northerlies.