In Depth Model Discussion, Analysis and Summaries

[Duane S.]

Could somebody provide me with the best place to view the current (10 & 30 hPa) Stratosphere temps please. I have inexplicably lost my bookmark to it.

[Guest North Sea Snow Convection]

Could somebody provide me with the best place to view the current (10 & 30 hPa) Stratosphere temps please. I have inexplicably lost my bookmark to it.

Here you go

http://strat-www.met.fu-berlin.de/cgi-bin/times?plot=temps&alert=1

[Thundery wintry showers]

Regarding talk about a warm February I'm not sure that Glacier Point's analysis conclusively suggests one, though there are certainly hints at the possibility with a chance of a more "default" El Nino pattern setting up. And of course there's the question of how warm, and warm in what sort of way. For example the cold December/January of 1981/82 were followed by a warm February with no lowland snow whatsoever, but the warm February of 1966 (again referring back to the 1965/66 analogue) still managed to produce a snowy easterly outbreak for many northern and eastern districts.

The solution progged for the middle part of the month- high pressure around Iceland- could well be quite snowy for some eastern and southern districts due to the easterly winds on the southern flank of the high as well as potential for systems to try to push up from the SW. It would be dry in the north and west though. I think January 1963 often featured that kind of setup as well, though I don't expect it to be anything like as cold as January 1963 was as there will be less extreme low 850s around.

[kold weather]

With GP's last post I also am quite interested in the pattern from the 10-15th onwards, its a real mess with regards to the transition from what is currently a very good upper pattern to one that could easily blowtorch in Feb so to speak, I seem to recall seeing a winter that had a similar pattern with a severe Jan then a very mild Feb...indeed a similar pattern likely occured in 81-82 and probably also in 96-97.

For now though as GP has stated things look rather interesting. The high should topple from Greenland BUT the angle of the PV at least to 240hrs will stop the high from slipping too far SE and importantly with the GWO/MJO towards that period likely to be heading back towards a very favorable phase we could well I really think we will see the models suggest soon a rebuild of a eastern -ve NAO bout and as GP said I expect the upper high to try to develop northwards.

The exacts of the wind flow will depend rather strongly on what the PV does, we have as southerly jet so IF the PV ends up near Canada as the GFS has been suggesting then SE wind mass seems most likely, if we end up with it over Scandinavia then a mixture of SE/E and also northerly shots seem probable.

This month IMO is setting up to be our greatest shot at a severe winter month (sub 1.5C) since the warm phase of the Atlantic kicked in during 1995...

[Glacier Point]

sorry john my stupidity! of course what i meant is mid - late janruary still on for severe cold as originally predicted?

I'm still very keen on this period being the zenith of our cold pattern Geoff as it will probably coincide with the MJO and GWO both entering a favourable phase for blocking to our immediate north allowing the jet to pass directly underneath.

The posts above pretty much capture this discussion about where we go from now to the end of the month and beyond. Of particular interest in the medium term is the depth of the surface cold given upper air values / thicknesses well, well below average for a sustained 6-12 day period and still, anticyclonic / col type conditions. The only variable missing is snow cover but the coming night time minima are going to be the real news story. Places such as Benson, Pershore, Great Malvern and Shawbury are worth keeping an eye on in this respect.

As per Ian and Darren's posts - some potentially very warm phases of weather into February as the whole pattern becomes very unstable with blocking collapsing with wedges of cold air being shifted around the mid latitudes bumping into sub-tropical airmasses.

[Snowaddict]

I'm still very keen on this period being the zenith of our cold pattern Geoff as it will probably coincide with the MJO and GWO both entering a favourable phase for blocking to our immediate north allowing the jet to pass directly underneath.

The posts above pretty much capture this discussion about where we go from now to the end of the month and beyond. Of particular interest in the medium term is the depth of the surface cold given upper air values / thicknesses well, well below average for a sustained 6-12 day period and still, anticyclonic / col type conditions. The only variable missing is snow cover but the coming night time minima are going to be the real news story. Places such as Benson, Pershore, Great Malvern and Shawbury are worth keeping an eye on in this respect.

As per Ian and Darren's posts - some potentially very warm phases of weather into February as the whole pattern becomes very unstable with blocking collapsing with wedges of cold air being shifted around the mid latitudes bumping into sub-tropical airmasses.

Thanks again GP for the fantastic updates and to JH above also.

So basically, if I'm understanding it correctly, you are expecting an overall winter pattern being the reverse of what we would usually expect in light of El Nino conditions. That is a cold December and January with a mild, even warm February..

Do you expect any potential for renewed blocking and cold in February or for a fairly consistent mild or very mild pattern?

SA

[Don]

GP's thoughts of a possible warm February are obviously disappointing. However, Winter's with all 3 months below average have been quite rare for sometime. Although saying that, last year came pretty close with only the unexpected barmy 2nd half of Feb scuppering it, but as far as I can tell, none of the cold Winter's of the 1980's had all 3 months below average. However, with the exception of 1981, December's were the mild months, with 1985 and 86 being very mild and I would rather have a mild December than a mild February, but obviously beggars can't be choosers! So, if we are to have a cold January, perhaps we shouldn't be too dispondant regarding a milder February. What I wouldn't want to happen though is for this Winter to go the route of 1996/97. That really was a classic pear shape! I agree that we should look forward to the short and medium term ATM and make the most of it!

[chionomaniac]

Thanks again GP for the fantastic updates and to JH above also.

So basically, if I'm understanding it correctly, you are expecting an overall winter pattern being the reverse of what we would usually expect in light of El Nino conditions. That is a cold December and January with a mild, even warm February..

Do you expect any potential for renewed blocking and cold in February or for a fairly consistent mild or very mild pattern?

SA

It does look like we are getting a topsy turvy winter to the one that we could have expected, but I guess we would have bitten winter's hand off to get this pattern for winter in the Autumn. Even though the stratospheric outlook certainly gives the impression that a milder February will be the form horse as Tamara says we cannot rule out the possibility of a MMW during January which really will put the cat amongst the pigeons. Funny enough, MMWs do seem to occur quite readily when the stratosphere is exceedingly cold.

[beng]

It does look like we are getting a topsy turvy winter to the one that we could have expected, but I guess we would have bitten winter's hand off to get this pattern for winter in the Autumn. Even though the stratospheric outlook certainly gives the impression that a milder February will be the form horse as Tamara says we cannot rule out the possibility of a MMW during January which really will put the cat amongst the pigeons. Funny enough, MMWs do seem to occur quite readily when the stratosphere is exceedingly cold.

I agree - I suspect that given the southern jet around the N Hemipshere, as soon as the days get a bit longer (say another couple of weeks from now) then that additional snow cover (I'm assuming there is - don't have time to check) is going to be reflecting sunlight and increasing ozone levels in the stratosphere; I wouldn't rule out a Feb freeze yet. Colder than average El Nino winters normally keep the best weather (depending upon your perspective) to Feb.

[Eugene]

I agree - I suspect that given the southern jet around the N Hemipshere, as soon as the days get a bit longer (say another couple of weeks from now) then that additional snow cover (I'm assuming there is - don't have time to check) is going to be reflecting sunlight and increasing ozone levels in the stratosphere; I wouldn't rule out a Feb freeze yet. Colder than average El Nino winters normally keep the best weather (depending upon your perspective) to Feb.

Yes i agree, i would be very surprised to see a warm February(worst case scenario would be a slightly above average Feb IMO) after a cold to very cold January, i don't think you can underestimate the effects all that deep cold in europe will have on us going into February and as we all know Feb is usually the most anticyclonic month of the winter, i see Feb 2010 having a similar pattern to 1963.

I think the year overall for the UK will be colder than we are used to, if we get a cold winter which we have a very good chance of usually spring is below average too as a cold winter usually gives cold ground temps and colder than average sea temps around the UK giving a lag to the already slow spring UK warm up.

[Rollo]

Having been around in feb 63' I can tell you that one of the american long range forecasts was for Feb to be a mild month but whilst they were wrong I would advise you to ignore what GP says at your peril. He has ,as we know got it so right thus far.

[Duane S.]

Here you go

http://strat-www.met.fu-berlin.de/cgi-bin/times?plot=temps&alert=1

Cheers!

[mushymanrob]

please dont moan if february is warm... 2 cold months, often very cold and snowy, are much better then what we have had in recent years. id like a warm february, and spring.

[johnholmes]

IF it becomes as cold as the predictions seem to show Mushy I suspect that you will not be alone in wanting an early start to some spring warmth!

[Thundery wintry showers]

Significantly milder for February looks a pretty safe bet, but "mild and snowless" is more tricky. If I'm reading it correctly, Glacier Point's analysis suggests increased mobility in February with pools of mild and cold air shifting around the Northern Hemisphere- and that doesn't rule out the possibility of one or two of those cold pools temporarily affecting the British Isles. There was an easterly in mid February 1966 in an otherwise mild month, and I mentioned in the general Model Output Discussion that early to mid January 1985 had similar synoptics to what we're seeing on the models, followed by a temporary warm-up and then another easterly in mid February.

Indeed, I think if January turns out similar to 1985, many people will be blase about, and some fed up with, the prolonged cold snowy weather that would result, and most would not begrudge a warm February. I certainly won't be moaning if we get a warm February (and indeed if we get a warm spring afterwards).

On the other hand, I have a request of my own to the masses: please don't moan if February and spring 2010 turns out to be anything less than completely snowless and homogeneously warm. I know Mushy fondly recalls February and spring 1982, but it could become very hostile on here if we get a repeat of the first week of May 1982 (northerly winds and wintry showers) even if most of the rest of the spring is warm and sunny, as it was in 1982. Tolerance all around please, regardless of what the weather does.

[Bristawl Si]

"Indeed, I think if January turns out similar to 1985, many people will be blase about, and some fed up with, the prolonged cold snowy weather that would result, and most would not begrudge a warm February. I certainly won't be moaning if we get a warm February (and indeed if we get a warm spring afterwards)."

I think this is a fair comment TWS. At the mo here in the West looks predominately dry. I'm not convinced we'll get much snow here and i've known winters past which were regarded as generally mild produce more snow events.

Yes, i know there's another couple of months of winter left, but i've known cold, dry winters before and sometimes things of a snowy nature do NOT develop. In fact some model runs are beginning to hint at a HP sitting slap bang over the UK in 10 days time.

This winter is shaping into more of a north/east event - something not uncommon in UK winter terms. Putting my IMBY hat on we require 'threats' from the SW, but i know that doesn't please the purists on here who see those types of LP attacks as a threat to prolonged cold.

The synoptics may be the best in years, but the true worth, for many on here, will be if they eventually produce more widespread snow. I'm one of those spoilt by the experience of the winters between 78 and 87, when we had some severe blizzard events. So my expectations are set high.

[VillagePlank]

I didn't know where to put this, so it's ended up here - please feel free to move Mr & Mrs Moderator ... but can you let me know where it should go, please if you do ...

This is to do with statistical CET Analysis, and attempting to extrapolate such analysis forward.

If one takes the whole CET set of 2009 and performs a correlation analysis then the closest ten years are as follows:

(where r is correlation (0..1) and it's domain, for this set is 0.861 .. 0.995)

Rank, Year, r

1 1663 0.995

2 1766 0.994

3 1681 0.994

4 1979 0.993

5 1695 0.993

6 1665 0.991

7 1838 0.990

8 1959 0.990

9 1942 0.989

10 1886 0.989

Using the two that appear the closest in time to present day, 1959, and 1942 ...

1960 had an almost spot on average January of 3.8C, an above average February, but a super-above average March.

1943 heralded a very warm year - one of the first >10C CET years, I think.

However, this analysis is probably better dealt with by comparison to the previous months CET (in this case December) since correlation simply measures the fit of the ups and downs and not the magnitude, so, therefore:

• Jan, 1943 is 1.8C lower
  
• Jan, 1960 is 2.2C lower
  

A pattern does seem to emerge. A dip in CET comparitavely between December and January followed by a huge hike in temperatures from February onwards.

And that's the technical analogue forecast

EDIT: 1985 is ranked 66th

EDIT2: Is it worth doing a CET correlation/analysis thread (say for previous 12/18/24 months?) Would anyone actually be interested in such an undertaking?

EDIT3: Just noticed I missed 1979 - damn that old Speckled Hen .... Jan, 1980 had a CET 3.6 lower than Dec 1979, followed by a very warm February, and a reasonable March.

Edited January 2, 2010 by VillagePlank

[johnholmes]

an interesting post VP

tends to fit with most others ideas of January and possibly those who have ventured into February.

[Weather-history]

Using the two that appear the closest in time to present day, 1959, and 1942 ...

1960 had an almost spot on average January of 3.8C, an above average February, but a super-above average March.

1943 heralded a very warm year - one of the first >10C CET years, I think.

However, this analysis is probably better dealt with by comparison to the previous months CET (in this case December) since correlation simply measures the fit of the ups and downs and not the magnitude, so, therefore:

• Jan, 1943 is 1.8C lower
  
• Jan, 1960 is 2.2C lower
  

A pattern does seem to emerge. A dip in CET comparitavely between December and January followed by a huge hike in temperatures from February onwards.

Having said that the Decembers of 1942 and 1959 were very mild, December 2009 was about 3.0C cooler, so those Decembers started from higher starting bases.

Also the February 1960 was only 0.3C warmer than the January, so there was no real hike in the CET value in this case.

[VillagePlank]

Having said that the Decembers of 1942 and 1959 were very mild, December 2009 was about 3.0C cooler, so those Decembers started from higher starting bases.

Also the February 1960 was only 0.3C warmer than the January, so there was no real hike in the CET value in this case.

Yep - this analysis looks at changes, and changes in rates of direction of the CET, not absolute values. Over the last 4 or so months, 1979 has repeatedly come up - maybe there's something in it.

Sorry about vagueness a bit too much today.

Edited January 2, 2010 by VillagePlank

[Thundery wintry showers]

February 1960 had a very mild beginning and end, but a 10 day long cold snowy spell in the north:

http://www.wetterzentrale.de/archive/ra/1960/Rrea00119600212.gif

http://www.wetterzentrale.de/archive/ra/1960/Rrea00119600217.gif

[VillagePlank]

February 1960 had a very mild beginning and end, but a 10 day long cold snowy spell in the north:

http://www.wetterzentrale.de/archive/ra/1960/Rrea00119600212.gif

http://www.wetterzentrale.de/archive/ra/1960/Rrea00119600217.gif

Yes, the monthly CET is misleading: such that smaller cold spells are almost always misplaced by higher CET values. In that respect the CET is actually a good indicator of local climate, but a poor indicator of weather, unless you go to the extremes - ie a very low CET says something, and a very high CET says something.

Still, 1979 seems to be the analogue. (there is a huge amount of caveats, here, and I promise I will write them up when I am less enebriated)

Edited January 2, 2010 by VillagePlank

[Glacier Point]

Overall and relative angular momentum continue to reflect a classic 'El Nino wane' period where we see a slight decrease in angular momentum tied to tropical convection transferring into the Indian Ocean.

Interestingly, the GWO is in phase 0-1 and will likely undergo shallow orbit through phases 1-2-3-4. This mirrors the GWO during January 1987.

http://www.esrl.noaa.gov/psd/map/images/gcm/gwo_40d.gif

http://www.esrl.noaa.gov/psd/map/clim/gwo.data.txt

The highly amplified pattern in the Pacific is a key indicator of angular momentum decreasing and booting up the northern arm of the jet.

However, there is a strong pulse of westerly winds across large parts of the Pacific through 30-40N. This will probably result in a shearing off of the poleward eddies across 50N+ leaving the jet stream to flow flat and low. This will starve the northern arm of energy leaving the eddy programmed over Iceland - Scandinavia with no where to go but slowly retrogress back noth west and boot up the southern arm of the jet.

Those westerly winds are now appearing on water vapour satellite imagery and tendency in relative angular momentum:

http://www.esrl.noaa.gov/psd/map/images/reanalysis/aam_total/glcalctend.sig.90day.gif

What this means is that the sub-tropical jet is going to become re-charged leaving little flow to the north allowing a re-emergence of the blocking structures between Greenland and Iceland around 12-14th January.

Model guidance tools for day 10 do look consistent with this:

GFS ensemble mean height anomaly:

http://raleighwx.easternuswx.com/models/gfsensemble/12zGFSEnsembles500mbHeightAnomalyNH240.gif

GEM ensemble mean height anomaly:

http://raleighwx.easternuswx.com/models/cmcensemble/12zGGEMEnsembles500mbHeightAnomalyNH240.gif

That is a very strong signal for a day 10 anomaly centred towards Iceland at this stage and 850 hPa temperatures between 8 and 4 degrees below normal. Put that together with the synoptic pattern with lots of energy flowing underneath the UK, there is a high potential for snow with the main threat coming in from the south-west and south.

By t300, the ensemble means persist the blocking structures. With the anticpiated evolution of the MJO and GWO heading through phases 4-5-6, there is no where for the blocking to go but southern Greenland.

[The PIT]

Still going for a warm feb GP ????

[Thundery wintry showers]

Looking closely at GP's projections, that perhaps suggests something slightly less cold from the E or NE towards midmonth as the supply of very cold upper air gets cut off (though still probably sub zero towards the SE) and then a possible reload from the north? If that comes off, the evolution to milder weather that I went for in my monthly forecast would most likely end up delayed by another week or so and leave us in with a real chance of a sub 2C CET, let alone sub 3C.