[Would you like a 'hunt for cold' model thread?]

As a cold fan I would feel more comfortable with a cold hunt thread.  Perhaps there could also be mild/heat hunt thread too?

[February 2015 CET forecasts]

Rest in pieces 'winter' 2014/2015!  8C    Last sub -1C, last sub 0C and last sub 1C February in 1986.  Last sub 2C February in 1991.  Last sub 3C February in 2010.  Last sub 3.5C February in 2013.

[THIRTY YEARS OF GLOBAL COOLING CAUSED BY A "GRAND SOLAR MINIMUM"]

Just one point if no moderate/strong El Niño shows soon the AMO will go negative meaning Arctic ice expansion past Svalbard.

One of the two theories will fail and it will be known within next 10 to 20 years.

I think the chances are judging by how far gone things have got in the last 30 years (especially with rainforest destruction and arctic ice melt and further increases in greenhouse gases), that even if the AMO goes negative it will merely just slow the next stage of global warming or at best delay it or reverse it for a few decades, similar to the 1940s-1970s temporary cooling but perhaps bottoming out at a higher baseline.  The extent and magnitude as well as longevity of any cooling effect from the Cold AMO phase and solar minimum will also be dependent on the phasing with cold La Nina favoured (on multi decadal timescales) ENSO and PDO phases and a cooler Indian Ocean.

[Absolute Worst Case Scenario?]

Thanks Knocker that was very interesting and informative stuff.  That means that we need to watch out for changes in the amount and rate of chemical weathering to determine the likelihood of any long lasting major runaway greenhouse effect or even just shorter lived and modest runaway warming events.  That also means that going the other way in the period of 55000000 through 3000000 years ago, the development of major mountain chains such as the Tibetan Plateau/Himalayas and the Rockies and Andes with their associated rainfall driven chemical weathering breaking down CO2 in concert with the formation of the current continental and ocean configuration must have been fundamental in the transition from the long trans Permian-Pliocene Greenhouse period to the Quaternary Icehouse period.

[Absolute Worst Case Scenario?]

Call me paranoid but the rapid increase in greenhouse gases along with the rapid increase in global temperatures over the last 30 years but even more so over the last 6 years has now got me seriously contemplating, just what would the absolute worst case scenario be from Anthropogenic Global Warming?

 

If us humans become so greedy and/or energy thirsty that every molecule of greenhouse gas (such as carbon dioxide, methane and water vapour) gets lofted into the atmosphere whether it's via deliberate means such as drilling and mining for fossil fuels and then burning 'em, and deliberate burning/clearing of the rainforests and other forests, or/and "accidental" means such as positive feedback mechanisms to the initial AGW such as "natural" rain forest/other forest fires, rainforest/other forest death from heat stress, heat loving bacteria breaking down organic matter, increased water vapour (also a very powerful greenhouse) from warming rivers, seas and oceans, methane (also a very powerful greenhouse gas) released by melting permafrost and ice sheets and the Clathrate (aka Methane Hydrates) Gun mechanism, just how hot will Earth become?

 

Will Earth become as hot or even hotter than Venus with average global temperatures of 400C through 500C?  Could Earth singlehandedly due to us mere humans become not just the hottest planet in the universe but extremely hot with average global temperatures in the 500C through 1000C range?  Theoretically if virtually the whole troposphere averages much above 100C (the boiling point of water), then such extreme greenhouse heating would be virtually permanent because every molecule of water from the land and oceans will be permanently lofted into the atmosphere as water vapour and remain so since the air will be "too hot" for clouds and rain to form and wash it out.

[January 2015 CET forecasts]

Early on yes but I feel this month too will struggle to be below average. 

I think we can already rule out a below average month.  Once the near record/record warm days have been fed in to the monthly CET data, we will be looking at a "record warm month or not" situation again unfortunately.

[January 2015 CET forecasts]



It is indeed outstanding how these mild records keep toppling with barely a murmur from the Netweather audience.

I think the lack of "murmurs" here is merely due to the fact that these mild/heat records have become so common over the last 25 years or so that it is just not surprising or exciting anymore.  I'd imagine there would be more surprise and excitement if the cold of December 2010/March 2013/July 1965/October 1974 calibre made a sudden unexpected comeback.

[Why do deep Lows favour moving to NW of UK?]

Deep lows usually sweep or stall to the Northwest of the UK because of the steep temperature gradient which exists between the very cold Labrador Current and the frigid Greenland Ice sheet and the warm North Atlantic Current.  This is reinforced by the deep Cold Air Advection within the prevailing frigid Polar Vortex/Trough over Greenland and the deep Warm Air Advection within the warm upper level ridges associated with the Azores High and/or Bartlett High.  This temperature gradient extends throughout the troposphere and often extends through the GIN Corridor aka "Greenland Iceland Norway Corridor" in association with a powerful upper level southwesterly Jetstream.

 

 

Cant answer that question, but the deep lows in February 2014 certainly did not track to the North West, they ploughed straight into the UK.

The deep lows in winter 2013-2014 ploughed through the UK due to the main southwesterly Jetstream being displaced further south than usual due to the upper level Greenland Polar Vortex/Trough and associated deep Cold Air Advection extending all the way down the eastern seaboard of Canada and the U.S.

[Is 2014 set to become the year the 'Naturals' flipped?]

Well if this is right, then that means that Blast From The Past was wrong about the so called "La Nina Perturbation Phase" (which started apparently in February 2007) lasting 36 years.

[The 30 year anniversary of the winter of 1985.]

Despite being right on the south coast, Portsmouth can do surprisingly well for snow as long as the air is cold enough for a very deep layer.  I remember watching one of Gavin Partridge's historic videos which showed Portsmouth covered in deep now at the end of April 1908!

[January 2015 CET forecasts]

Good stuff. To add to that, using the 1700-2000 average, the last time we had a 10 year period where we had more below than above average months was back in 1922-1931.

I am very surprised that even the cool rocking 1960s had less cool months than that modest period.  I think that 1922-1931 (more so 1920-1929) period is very unusual.  Although this was a cool/cold period for April, June, August, September, November and December, this was an early period for warm Januaries, warm Februaries and warm Marches.

 

 

Defining a Cold Month Year as in the top 25 coldest months for Man CET since 1700.....to qualify for this a January would need to have a mean CET of 0.4C

Looks very much like it's not going to happen this year.....but the last time we got a Cold Month Year for January was in 1979 which is a wait of 35 years, only the 49 year wait for a cold July has been longer! In contrast there were five in the 11 years 1820 to 1830!

That said it's not the longest wait we've experienced.... in the 100 years between 1839 and 1939 there were only three such January's with 1879 bringing a 41 year wait to an end and 1940 bringing a 45 year wait to an end,

Here's a list of the how many years we've waited for the last Cold Month with the number of corresponding Warm months we've had in that period....only December of all the months has had no Warm months since the last Cold one!

I think the lack of "proper cold" months in the UK, especially in the April through November period is down to a number of reasons:-

1)  There is generally less range between the hottest and coldest months as well as less range between the coldest months and any average in the non-winter period which in turn is mainly due to

 

2)  The reduced availability or horizontal volume of very cold air (on average) to be tapped in the non-winter months which has been exacerbated in the last 30 years by

 

3)  The warming of the Arctic and the North Atlantic with the associated loss of Sea Ice needed to generate very cold air over the North Pole and/or Greenland for the UK.  This is less important in the actual winter months and March since very cold air can still be generated over Eurasia in lieu of the warmer Arctic hence the very cold December 2010 and March 2013.  However with the absence of a sustained and widespread volume of proper wintry cold air over Eurasia even in a "very cold" Eurasian summer, a cold northern North Atlantic and a cold North Pole and/or cold Greenland is then required for very cold non-winter months in the UK.  This means that with a warm North Atlantic and a warm North Pole and/or warm Greenland, very cold months in the April through November period in the UK will be virtually impossible or at least very hard to achieve.

 

4)  In concert with the above there has also been increased dominance and increased intensity of Maritime Tropical and Continental Tropical airmasses and reduced potency and reduced dominance of Maritime Polar and Continental Polar/Arctic airmasses in the April through November period as well as the December through March period.

[January 2015 CET forecasts]

I think we'll go into the freezer in the second half of the month hence my guess of 3.2C.

This is going just great the drinks are on me.

I still think we will plunge into the freezer I do not see a GH but a Scandi high circa 15-20th January. MJO looks to be turning more favourable later in the month (phase 6) increasing the likelihood of blocking.

I'll drink to that

The drinks are all on me!

[December 2014 CET forecasts (start of 2014/15 contest year)]

A notable statistic indeed, a year virtually devoid of any period of below average CET values for any lengthy period. Only August produced a spell of such weather. Is it any coincidence I wonder it has come on the back of solar cycle peak activity, 1990 being another case in point?

This solar maximum was weaker than the super solar maximum from the last cycle.  I think the record warmth in the UK in 2014 is more likely due to an La Nina>El Nino transition combined with exceptionally warm airmass source regions especially the North Atlantic and tropics.  The globe has also had its warmest year on record.  August was merely cool due to ex Hurricane Bertha taking that unusual diving track over the UK and setting up that deep and stagnant upper level trough.  Without Bertha I am sure we would have had no cold months whatsoever in 2014.

[An Unusual August and September?]

However, at a bit of a stretch, it could be related to the AMO. Results from a Met Office conference, which you can read here, suggests that a +ve AMO can promote mild/cool, wet summer. Other studies also link the +ve AMO with more -ve NAO winter values and more extreme winters in western Europe (example here and here.)

That is very surprising.  I always thought, and many others here and elsewhere have said that the AMO is positively correlated with the NAO, not negatively correlated with it.  More logically any link between the "cool August and mild September" combo and cold winters must surely be due to enhanced and frequent blocking features with the associated highly amplified and unstable main westerly Jetstream?

[December 2014 CET forecasts (start of 2014/15 contest year)]

Seems likely that a finish of between 5.5 and 6.2C is likely before corrections, then 5.1 to 6.2C after corrections.

Another naff end to another very naff year.

[Greenland High vs Scandinavian High or Both]

It is indeed a very complicated picture, Gibby.  Some of our classic winter months have the Scandinavian High waxing and waning all month.  February 1956 is a classic example.  This month had a Greenland High all month along with a Scandi High but the Scandinavian High kept waxing and waning.  However because the main westerly Jetstream was always on a southerly track from the eastern U.S, across the North Atlantic and into southern Europe with the Greenland High always remaining strong, the cold lasted the whole month as Northerly and Easterly winds repeatedly alternated with each other.

[Ever Had Snow from the South?]

It's a real struggle to get widespread snow from a direct westerly, and it's even harder to get it from a southerly or south-westerly, because the implication is that the arctic air has had to travel over the Atlantic at low latitudes before getting to here.

You forgot about this Cold Zonality classic from January 1984.

http://www.wetterzentrale.de/pics/archive/ra/1984/Rrea00119840115.gif

http://www.wetterzentrale.de/pics/archive/ra/1984/Rrea00219840115.gif

[The Stages Of Current UK Warming]

Since we have all but seen through the warmest year on record in 2014, only 3 years after the 2nd (2011) and only 8 after the previous 1st (2006), I have revisited "North Easterly Blast's" summery of the stages of current UK Warming from 2006 with the 8 years since added in.

 

Using http://www.metoffice.gov.uk/hadobs/hadcet/cetml1659on.dat for reference the stages of the current UK Warming trend in the exact order so far are as follows:-

 

-Stage 1.  This stage lasted from October 1987 through January 1997.  It may seem odd saying that the current UK warming trend began with the cool October 1987 instead of the mild December 1987 but October 1987 contained the first of a regular series of devastating Mid-Latitude Cyclones.  These severe synoptic scale storms have been an all too regular feature of the warming trend since 1987 including but not limited to the Burns Day Storm of January 1990, the Christmas Eve Storm of 1997, the Boxing Day Storm of 1998 and the storm on 19th January 2007.

 

However apart from the increasing frequency of severe synoptic scale storms this stage of UK Warming was otherwise very erratic and on average small with very warm years like 1989, 1990, 1994 and 1995 offset by much cooler years or year long periods such as December 1990 through November 1991, July 1993 through June 1994 and December 1995 through January 1997.  In the latter example, 1996 was our last cool calendar year in between 1987 and 2010.  Our last dramatic and potent cold front passage occurred in this initial warming stage on 9th July 1993 which heralded a consistently cold and at times very cold July through November period in 1993.  Our only single potent and extreme cold snap in between 1987 and 2009 occurred over Christmas and New Year 1995/1996.

 

On the seasonal level springs and autumns were mundane and mild apart from the very mild springs of 1989, 1990 and 1992 and the very mild autumns of 1994 and 1995.  The mild/very mild autumns were offset by the cold but unremarkable autumns of 1992 and 1993 which were our last proper cold autumns.  The spring warming trend has temporarily halted by the cold but unremarkable spring 1996 which was our last cold spring in between 1986 and 2013.  Summers warm in this period but remained changeable with the very warm summers of 1989, 1990, 1994 and 1995 offset by the more normal but still warm summers of 1991, 1992 and 1996 and the cold summers of 1988 and 1993 which were our last cold summers in between 1987 and 2011.  Winters were also warm but still changeable with the very mild winters of 1988/1989, 1989/1990, 1992/1993 and 1994/1995 offset by the more normal but still unremarkable winters of 1993/1994 and 1996/1997 and the cold but unremarkable winters of 1990/1991 and 1995/1996.  1990/1991 and 1995/1996 were our last cold winters until winter 2008/2009.

 

-Stage 2.  This stage lasted from February 1997 through March 2006.

 

-Stage 3.  This stage lasted from April 2006 through June 2007.

 

-Stage 2.  We descended back down to stage 2 from July 2007 through November 2008.

 

-Stage 1.  We descended back down to stage 1 from December 2008 through December 2010.

 

-Stage 3.  We jumped back up to stage 3 from January 2011 through March 2012.

 

-Stage 1.  We plunged back down to stage 1 from April 2012 through June 2013.

 

-Stage 3.  We have jumped back up to stage 3 from July 2013 through December 2014.

 

 

Are we near Stage 4?

 

In my opinion when the annual CET in a calender year reaches or breaches 11C we will have reached stage 4 of UK Warming.  Although this has not happened yet for a calender year there have been some year long periods reaching and breaching 11C over the last 20 years.  The first occasion which was November 1994 through October 1995 oddly enough occurred during the otherwise stage 1 period of UK Warming and was bookended by the much cooler years of 1993 and 1996.  The second occasion occurred from May 2006 through 2007 and the third occasion from December 2013 through November 2014.

[Boring months]

I have now added November and December 2014 to the rest of 2014 in my "forgettable months" dustbin.

[January 2015 CET forecasts]

On ‎19‎/‎12‎/‎2014 at 15:50, SteveB said:

I don't think we are going to see deep cold, but maybe fleeting cold snaps

 

3.1c please.

Even this would be a lovely improvement over these last 4 rubbish winter months.  Alas on the other hand...

 

A new year but same old mild rubbish yet again...  8C    Last sub -3.0C January in 1795.  Last sub -2.0C and -1.0C January in 1963.  Last sub 0C January in 1979.  Last sub 1C January in 1987.  Last sub 2C, last sub 3C and last sub 3.5C January in 2010.

[December 2014 CET forecasts (start of 2014/15 contest year)]

Pretty sure it will end up above 6c now (my 4c guess way out)!

and it won't take much on top of that for 2014 to reach and breach the dreaded 11C.  All this with a cold August.  It's frightening to think that if those warm/hot August forecasts had come off along with only a few record breaking CETs (like in 2006), we would be staring down the barrel of a 12C-13C year.

[December 2014 CET forecasts (start of 2014/15 contest year)]

The last three Christmas periods have been notably mild though, 2011 and 2012 notably so, in stark contrast to 2009 and 2010.

December has completely changed in the last 4 years.  After the very cold December 2010 had gone, the December CET has been flying since then.  It seems that after oddly being the only cooling month in the 1990 through 2010 period December has finally joined all the other months in the relentless UK warming trend with perhaps only August now dropping off the warming bandwagon.

[December 2014 CET forecasts (start of 2014/15 contest year)]

A very mild day, no doubt, but I'll eat my hat if it's as warm as the 12z GFS parallel suggests.

At this rate it will only be a matter of time before 20C and over days appear in winter.  We only just missed 20C in February 1998.

[December 2014 CET forecasts (start of 2014/15 contest year)]

Conflicted. On the one hand i want cold weather and do still think a CET near or below average stands a good chance (well done Netweather forecast range) but on the other this coming pattern puts me right into the fray.

and so the broken record of the post June 2013 mild train carries on despite the best efforts of the very -OPI.

[December 2014 CET forecasts (start of 2014/15 contest year)]

So even at the halfway point it will still be up in the air whether December 2014 finishes as a cold month, average month or a mild month which will single handedly determine if 2014 becomes the warmest year on record.  Still this situation is quite different from most months this year (apart from August) in that the halfway point question had been not if but how mild the month will finish.