acbrixton

On the basis of the 18z output it looks as if we may be at, say, 15.4-15.7 at the 2/3 mark. Upper 16s look like the upper realistic eventual value (16.8 would require 19.0-19.3 for the final third) and low 15s for the lower realistic end of month value. At a guess I would go for 15.8-16.2 at this stage. Anything above 17 would be near impossible if we are at mid 15s by 20th July. regards ACB

SC have you any recent data to back up the assertion that Shetland has cooled in the last few years please? regards ACB

JH/GP many thanks for the explanations. JH: I had a quick look at the link and it seemed to me useful. regards ACB

John thanks for the update. Would you please set out the mechanism by which ex-hurricane 'Bertha' might intensify the -NAO signal? Doubtless some excitedly await the August CFS Christmas synoptic update for signs of 'upgrades/downgrades'... regards ACB

Pit, I think that Stu's reference was to London 850's and not 2m temperatures: the average 850 is about 9. regards ACB

Stewfox: 1. The amount of ice in Hudson Bay is not abnormaly high for late June but is rather lower than the 1979-2000 average [see Cryosphere Today]. 2. From what I can gather Hudson Bay is almost ice free , on average, between mid August and early October [see CT]. 3. It is one thing to ask about average ice extent/melting but quite another to describe the Asian ice on that map as being in the "far south of Asia". If you had bothered to consult an atlas you would see that the areas referred to (the Sea of Okhotsk and Shelakhov Bay) are at approx. 54-63 degrees north. They are generally ice free from early July to late September. [again see CT]. 4. 'Ice free' means that for a given area for a period each year there will either be no ice or a negligible amount of ice. It would follow that 'ordinary' shipping (i.e. not ice breakers) would be able to use routes in that area during the 'ice free period'. 5. When an area is free of ice for part of a year it does not necessarily mean that it will be free of ice in subsequent summers. However once old/multi-year ice melts it can only be replaced the next winter by thinner/weaker single year ice which is more susceptible to melting than old/multi-year ice in the following summer. If, for example, an area of single year ice experiences a particularly cold/cloudy summer it may not melt (or may melt to a lesser extent than would be expected). However as ice reflects incoming sunlight/heat whilst open water tends to absorb (the 'albedo effect') then that warmer water will tend to increase melting of nearby ice and delay refreezing and tend to lead to thinner winter ice. this is cited as an example of 'positive feedback'. There are other factors at play, of course, such as surface wind patterns and ocean currents. 6. On average NH minima are reached in the first two weeks of September. 7. As to when the Arctic Ocean will be essentially ice free during summer no-one knows: I have seen estimates ranging from 2013 to 2080, although recent estimates have tended to go for a date sooner than later. regards ACB

Roo, agree absolutely! VP, your last post demonstrates neatly why your departure from these threads would be a loss. Please reconsider... regards ACB

16.1 please for me. regards ACB

Well that would mark a departure from the pattern of recent years in the south east: frost in March not January and snowfall in March and April but rarely in winter. regards ACB

Paul whilst I can readily understand that this area is probably the most burdensome to moderate (save for model discussions in winter where a model indicates a vague possibility of snow), and whilst I agree with Paul (member no.2) that discussions tend to wards circularity and entrenched positions I think that this discussion is important for the reasons given by Devonian. I rarely post on Climate Change because I know too little and feel that I have nothing useful to contribute. However by reading the more intelligent posts and in particular links to abstracts of technical papers I am rather less ignorant than before (and less doctrinaire as to AGW). By debating, however imperfect, the protagonists should at least understand their own position better and might be able to test that position against those with contrary views. An attempt was made by the saintly/gentlemanly/ever patient and courteous P3 (where is he now?) to draw together some common ground between the two camps. He failed and no-one else is likely to suceed. One simple suggestion to improve the tone: avoid childish/inflammatory terms such as 'warmist' or 'deniers' in favour of supporters/opponents of AGW theory? regards ACB

Quite so. However last summer's warmth acted on an ice pack that had a rather higher proportion of thicker multi-year ice than is present this summer. It would follow, therefore (all other things being equal), first that a repetition of last summer's warmth would lead to a significantly lower minimum this year than last year, secondly that for this year's minimum to equal last year would not require such anomolous warmth. On the evidence so far it looks highly likely that the minimum will be below that of 2006, the second lowest minimum after 2007, and probable that it will approach that of 2007. regards ACB Not sure that I fully appreciate the point of the link: it cites a study purporting to show through dendrochonology that summers in northern 'Fennoscandia' were warmer than now at four points in the last 1500 years. Those findings may well be credible/academically respectable. However first they cover a small part of Arctic Scandinavia and not the Arctic region as a whole; secondly Arctic Scandinavia is very largely ice-free all year round; thirdly even if the findings were applicable to the entire Arctic region they would be irrelevant to the present discussion as to recent trends in ice minima in general and the prospects for this year in particular.

Bluecon, the NSIDC have now updated the graph (see BBC News Online) and as at mid June it is clear that the amount of Arctic sea ice is at a similar level to mid June last year meaning that so far this year there has been an increased melt rate compared to last year. From the graph it is clear that last year the rate of melt increased significantly in the 6 weeks from mid June to late July. It will be interesting to see how things stand at the end of July this year. So far the data appears to support those who have argued that the colder conditions in the Arctic last winter leading to an increase in both aggregate ice cover and the proportion of single year ice would not prevent a summer loss at least comparable to last year. regards ACB

John presumably that was taken from the LWC which, of course, is a 'non-standard' site? That would explain why it was omitted from the MO monthly summaries and thus the 30.1c recorded in Norfolk on the same day stands as the 'record' for the entire summer? regards ACB

The 1961-90 mean CET for June is 14.2, the 1971-2000 mean is 14.1. The England Mean Temperature Series (commenced 1914) for 1961-1990 is 13.6, the England and Wales Mean Temperature Series (commenced 1961) for 1961-1990 is also 13.6. The BBC monthly summaries (from the MO) now use the England Mean Temperature Series but summaries for earlier years have used the England and Wales Series and the 1961-1990 CET! regards ACB

Not so...see my post on another thread: " 4 Jun 2008, 03:07 AM Post #81 Nimbostratus Group: Members Posts: 668 Joined: 31-December 04 From: Brixton, South London Member No.: 2,453 QUOTE (Scorcher @ 4 Jun 2008, 01:53 AM) I read on this site: http://www.personal.dundee.ac.uk/~taharley/2007_weather.htm that 30.1C was reached at Terrington St. Clement in Norfolk on August 5th 2007, although I have no idea whether that is a standard site or not. Scorcher thanks for that. Having checked with the MO monthly summary you and Mr Harley are correct. Apologies. Strangely Philip Eden records the mighest maximum as 29.7c at Coningsby and Holbeach whereas the BBC monthly summary (prepared by the MO) states (with irritating sloppiness) "London, Cambridge, Holbeach and Coningsby all recorded temperatures around 30 °C on 5th." and "It was hot, dry and sunny on the 5th with temperatures around 30 °C in London, Cambridge, Holbeach and Coningsby." regards ACB" regards ACB

Roger was very decent in his suggested clemency; sadly I have only my own forgetfullness to blame! Re SF well he placed a May CET punt and I sent a pm to him recently, unanswered, so I do not know. It would be unfortunate if we were to have lost such a distinguished, if intellectually severe, member. regards ACB

Whoever suggested that I should not be penalised? regards ACB

Scorcher thanks for that. Having checked with the MO monthly summary you and Mr Harley are correct. Apologies. Strangely Philip Eden records the mighest maximum as 29.7c at Coningsby and Holbeach whereas the BBC monthly summary (prepared by the MO) states (with irritating sloppiness) "London, Cambridge, Holbeach and Coningsby all recorded temperatures around 30 °C on 5th." and "It was hot, dry and sunny on the 5th with temperatures around 30 °C in London, Cambridge, Holbeach and Coningsby." regards ACB

Ah well it all depends upon whether you accept the one recording of 30c last year as valid. That reading was from the London Weather Centre which the Met Office classify as a 'non-standard site' i.e. its exposure does not meet the MO's own criteria (the recording instruments are located on an asphalt roof). Thus there is a strong argument for disregarding that reading in which case 2007 joins 1993 and 1981. regards ACB

Taken from the BBC News website... I am broadly persuaded by the arguments of the IPCC and I certianly do not agree that prelates should not engage in matters of this world. However this sort of intellectual sloppiness and dishonesty only serves to weaken the respectable arguments of those persuaded that AGW plays a part in climate change but degrades the Anglican Church. I despair. "People who fail to tackle climate change are acting like an Austrian man who locked his daughter in a cellar for 24 years, an Anglican bishop has said. The Bishop of Stafford, Gordon Mursell, wrote in a parish letter that not confronting global warming meant people were "as guilty as" Josef Fritzl. It meant future generations would be left in a futureless world, he said. Mr Mursell added he was not accusing people of being child abusers but shocking analogies were needed. In a letter featured in parish magazines in the Diocese of Lichfield, the bishop wrote: "Josef Fritzl represents merely the most extreme form of a very common philosophy of life: I will do what makes me happy, and if that causes others to suffer, hard luck. I am simply trying to use an analogy to get people to wake up to the consequences of what we are failing to do "In fact you could argue that, by our refusal to face the truth about climate change, we are as guilty as he is - we are in effect locking our children and grandchildren into a world with no future and throwing away the key." " regards ACB

Greenwich_1971.doc Roger, a few thoughts on this... 1. During August there is a marked reduction in the length of daylight and the height of the sun above the horizon: for London daylight declines from 15h 23m to 13h 36m and the height of the sun at solar noon declines from 56.4 to 46.9; this alone would account for a tendency for the hottest spells in August to occur earlier rather than later in the month. 2. SSTs reach a maximum of about 17.5-18c in the central/eastern Channel and southern North Sea by late August but are only about 1c less at the beginning of the month. Furthermore as most of our hottest weather comes from a direction between south and east-southeast the impact of SSTs is limited. 3. I would have thought that the main impact of hurricane activity is to intensify Atlantic depressions to our west and north west. 4. There is a marked difference in the nature of August weather between the north west and south east of the UK. I attach (courtesy of the UKMO) data for Greenwich and Aldergrove for 1971-2000. Note that whilst at Greenwich August is the sunniest month it is the 5th sunniest month at Aldergrove and that whilst August has the second lowest number of wet days at Greenwich Aldergrove has the 7th lowest number of wet days. In terms of rainfall totals Greenwich has the 6th lowest whilst Aldergrove has the 7th lowest total: my guess is that taking into account Greenwich's sunshine and wet days that this relatively high rainfall figure is primarily due to convective rather than frontal activity. My guess is that this indicates an increase in the number and intensity of Atlantic depressions throughout August the direct effects felt primarily to the north west. I suspect that there is, however, an indirect effect in the south east. I assume that most (not all) of out hottest weather occurs when there is persistent low pressure to the west of Ireland and high pressure to our east. The increase in frontal activity to the north west would reduce the chances of that synoptic set-up and would suggest that the south and south east would benefit more from ridging of the Azores high than high pressure to the east. 5. Finally even in the south east the awakening of the Atlantic, evident throughout August in the north west, will start to have a direct effect by the end of August as shown by data for September for Greenwich. regards ACB

15.2 for me please. regards ACB

Yes John that would make sense, although one might expect the MO forecasters 'seconded' to the BBC to be no less accurate. A possible explanation for the BBC News Online errors might be the apparent manner in which the daily BBC summaries are (sometimes?) drafted. If you look at the updated daily summaries between about 10.30 and 11 pm you may somtimes see a draft of the summary consisting of the text but excluding the day's data at the end of the summary. Within about 30 mins to one hour the daily data are added to complete the summary. It may be that the break in drafting/concentration (to check/collate theata from the MO?) increases the liklihood of error. regards ACB

BF many thanks. I am ashamed to say that I had not heard of Kelvin waves before... regards ACB

Nick, yes that is a plausible explanation. Strangely the BBC News Online daily weather summaries give Wisley on 25.4c as the warmest station on Wednesday. regards ACB