Model Output Discussion:

[TEITS]

GEFS Parallel control run goes for an interesting set up which many in S England will hope verifies.

At first an intial burst of E,lys.

http://91.121.94.83/modeles/gensp/run/gens-0-1-126.png?0

Followed by LP tracking to the S bringing a snow event to S England.

http://91.121.94.83/modeles/gensp/run/gens-0-1-180.png?0

However the NOGAPS/GEM want to take the LP further N so obviously the risk of a snow event moves further N.

[nick sussex]

I woke up this morning with a sense of trepidation, so I thought I'd look at the smaller models first, picking the GME I thought oh no! Moved onto the GEM and NOGAPS, which didn't impress me too much but then found the salvation of the big 3!

To a certain extent theres a bit more uncertainty in how the pattern will set up but consistency with the big 3 that the Atlantic won't win, I notice this morning that the nuisance shortwave near Iceland has been weakened and disappears quite quickly, this then makes it a simpler route to colder conditions with the GFS leading the way in terms of cold, it drops the shortwave sw out of Norway and delivers the quickest change to colder conditions, its how the models handle this shortwave that will determine how quickly the colder conditions arrive.

The ECM looks a bit messy and doesn't sink the shortwave sw and the UKMO does but slower to do this. For those looking for a longer cold spell the ECM is actually an upgrade from last night with more energy in the southern arm of the jet, the UKMO at 144hrs is pretty similar in pattern to the ECM with another shortwave likely to eject off the main trough to the west at 144hrs.

IMO for you guys in the UK its very hard to complain about any of the big 3 output because they look cold with snow chances and given some of the horror output of a few days back are a major switch. For me I think I may see a few flakes down here at some point but am quite thankful that some of the mild mush together with a horrid foehn effect for the Pyrenees has disappeared so I 'm just quite relieved!

Edited February 4, 2010 by nick sussex

[Nick F]

Now we have general agreement between EC/GFS/UKMO on a block developing in the vicinity of Iceland, next we need to see what happens to the deep cold pool over Scandinavia - ECM takes it more south with NE backing N'erly winds, while GFS brings it SW with more of a NE'rly. 00z GEM by the way looks rather different from the big three, so not sure I'd buy that evolution!

[MisfitDog3]

I am not at all convinced by the severity or length of this (currently) forecast cold spell. There is still a lot of spread and some fairly major movement on some models over reasonably short period of time! I would be happier with a closer consensus in the short/medium scope as well. Not at all picky am I?! Arf!

With only the detail to be sorted out?! Yowzah..is that tempting fate or what? Plenty more to come from the models I think. Take your seatbelt off at your peril!

[nick sussex]

The ECM and GFS show good agreement on the upstream pattern and both have Omega blocks in the Atlantic!

http://www.meteo.psu.edu/~gadomski/ECMWF_0z/hgtcomp.html

[TEITS]

I am not at all convinced by the severity or length of this (currently) forecast cold spell.

No and the frustrating part is we probably won't know how the models handle the SW over Scandi until its within the +48/+60 timeframe.

A case of swings and roundabouts this morning because whilst the ECM is slower in bringing in the NE/E,ly due to the S. The longer term trend of the ECM is far better than yesterdays 12Z.

Lets also remember what happened during the last cold spell in Jan. All week prior to the cold spell my location looked very well placed to see the action. However the occluded front never made it to my location due to stalling just to the N. We then had very little notice of the massive snow event that affected S regions as this suddenly appeared on the NAE.

So whilst we continue to follow the models to get a general idea of the trend. The detail will not be sorted until it becomes in range of the NAE/NMM models.

Edited February 4, 2010 by THE EYE IN THE SKY

[nick sussex]

Upstream NOAA don't like the GEM operational run this morning which is a good thing as that was out of kilter with the ECM/GFS/UKMO.

THIS RELATIONSHIP SUPPORTS THE FASTER TREND IN

OPERATIONAL ECMWF RUNS OVER THE PAST DAY AND RECOMMENDS LEANING

AWAY FROM THE SLOWER SOLNS OF THE GUIDANCE SPREAD SUCH AS THE 00Z

CANADIAN.

Full discussions here:

http://www.hpc.ncep.noaa.gov/preepd/preepd.html

[cooling climate]

I just posted this in the stratosphere thread. If the forcast is correct then this

offers a lot of support to perhaps a prolonged very cold spell of weather to come.

Very encouraging signs from the ECM stratosphere forcasts this morning which ties in with the

blocking to the north being shown on the ECM synoptics charts.

http://strat-www.met...0&forecast=f192

Below is the chart for the 400K isentropic chart (roughly 50,000 feet) and you can see a

very favorably split vortex.

http://strat-www.met...0&forecast=f192

Also various levels of the stratosphere showing negative (easterly) wind anomalies.

Below is the forcast chart for the 10hpa level at day 8.

http://strat-www.met...0&forecast=f192

[The Weather Dragon]

Total 'big 3' model agreement at 120 - no searching for a cold spell in FI & a knighthood for Jay Wynne

Edited February 4, 2010 by Jonathan Evans

[TEITS]

ECM mean has dropped a couple of degrees.

http://www.knmi.nl/exp/pluim/vijftiendaagse/Data/15DAAGSE_06260_NWT.png

Still some scatter but far more runs towards cold than yesterdays 12Z. Also the OP was bang on the mean closely followed by the control.

[nick sussex]

ECM mean has dropped a couple of degrees.

http://www.knmi.nl/exp/pluim/vijftiendaagse/Data/15DAAGSE_06260_NWT.png

Still some scatter but far more runs towards cold than yesterdays 12Z. Also the OP was bang on the mean closely followed by the control.

Yes good to see that, I'm always happier when the operational and control runs are close together. Here comes the GFS 06hrs run, lets hope for the good trend to continue, still a bit nervous given the last week but I'll be happier once we get through this evenings model runs without any more drama.

[cooling climate]

Its not much but everything a touch further west on the 06z GFS run so far.

This also seems to be a trend to me which will help bring in the colder air

quicker, although as Teits and others have said the interest lies in what

happens to the troughing over Scandinavia for both cold and snow.

[sandstorm2]

Good agreement from three of the big models, and it is the third run where this has happened (stretching the truth a bit)out to +120, it looks like becoming cold again with the atlantic retreating with a bloody nose. Not sur about snow but that is in the fine detail.

SS2

[chionomaniac]

One thing on the models yesterday afternoon that I found odd was the way they dropped

heights quickly to the north bring back a +AO. This to me does not fit at all with the signals

from the stratosphere (SSW) and downward propagating easterly winds etc.

The bulk of the easterly winds are actually being forecast to being held in the stratosphere, cc, with positive anomalies being held from 70ºN-90ºN in the troposphere. However, significantly there appears to be an area of negative mean zonal wind anomalies held in the troposphere between 50-60ºN. Right where we need them.

[Southender]

Looking good at +96

[cooling climate]

The bulk of the easterly winds are actually being forecast to being held in the stratosphere, cc, with positive anomalies being held from 70ºN-90ºN in the troposphere. However, significantly there appears to be an area of negative mean zonal wind anomalies held in the troposphere between 50-60ºN. Right where we need them.

Morning chionomaniac, according to this chart they are propagating down just fine.

Certainly as good of better than the propagation in December. Negative winds showing

up at the 100hpa level on the ECM stratosphere charts.

http://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/gif_files/time_pres_UGRD_ANOM_JFM_NH_2010.gif

[Eugene]

Yes looking slightly better than 00Z so far

http://www.wetterzentrale.de/pics/Rtavn1141.png

Atlantic looking in a very sad state indeed and out powered by blocking to the north and east again, love it :lol:

[Southender]

Here it comes, -5's maybe reaching us a tad earlier and further SW too?...

Edited February 4, 2010 by LeighShrimper

[TEITS]

06Z continues to prog the SW (cold pool) in a SW direction. This is supported by the GEFS also.

http://www.wetterzentrale.de/pics/Rtavn1381.png

Need this to be confirmed by the other models though.

[Southender]

Nice!

-10's over a large swathe of the country.

Edited February 4, 2010 by LeighShrimper

[cooling climate]

Plenty of convection showing on this run for the eastern half of the country which makes

sense of course if the troughing (shortwave ) moves southwestward towards us.

This run could very well be better than the 0z by the looks of things.

I can imagine Steve sitting there calculating the snow totals for east Anglia and

the southeast.

Edited February 4, 2010 by cooling climate

[Southender]

Much better run than the 00z.

Cold pool further SW.

As mentioned above plenty of snow showers packing into the Eastern side and right across the Mids.

Edited February 4, 2010 by LeighShrimper

[Southender]

This is how the high res part (+180) finishes.

[Eugene]

Blo*dy hell, the eastern side of the country would be plastered with snow here

http://www.wetterzentrale.de/pics/Rtavn1801.png

[TEITS]

Well an excellent run for E parts in particular E Midlands/E Anglia/Lincs. Im sure those who benefit from a thames streamer will be hoping for a ENE/E,ly rather than a NE,ly. Still these details will continue changing until +0.