Model Output Discussion

[Methuselah]

A new thread, peeps...

Previous:

[Frosty.]

We can now add the GEM 00z to the ever growing list of models showing an Arctic blast, a real peach of a run which would deliver blizzard conditions and N'ly gales to the north & east and with reload potential too.

[Ben_Cambs]

Very impressive ECM this morning, I think at the moment it is pick of the bunch for the Arctic Blast. Hopefully some sort of agreement from all the models today!

[Shunter]

Will be interesting to see the NOAA discussion this morning to see what has triggered this colder development. Its across all models so synoptically something has changed or has widespread agreement/confirmation ( fairly early ) in the run.

[Polar Continental]

A slightly colder run from the 0z GFS this morning, All 4 major models now go for a northerly of slightly varying intensity.

Though at this stage, no really cold air being thrown in to the mix –5c to -8c uppers for a time over most of the country, maybe –10c 850’s getting in to Scotland for a time.

The Gem, possibly the best, though there is not a lot between them really.

If I was to pick one from the bunch, then it would be the GEM, as it keeps the cold going up to T240 and then looks like it could throw an easterly.

Edited January 24, 2010 by Polar Continental

[tinybill]

Will be interesting to see the NOAA discussion this morning to see what has triggered this colder development. Its across all models so synoptically something has changed or has widespread agreement/confirmation ( fairly early ) in the run.

something changed over night big time!!!

[Weather-history]

It looks potentially a load, reload to me. A northerly followed by a topple possibly followed by another northerly.

Edited January 24, 2010 by Mr_Data

[tinybill]

something changed over night big time!!!

wot can i say

[Glacier Point]

something changed over night big time!!!

Yes, this --->

http://cawcr.gov.au/bmrc/clfor/cfstaff/matw/maproom/OLR/m.3d.html

Tropical convection just east of the Dateline.

And this ---->

More or less instantaneous downwelling from the warming stratosphere.

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

The GFS ensemble mean is keen to maintain heights to the NW, even days 11-15 show a positive anomaly close to southern Greenland:

http://raleighwx.easternuswx.com/models/gfsensemble/00zENS11-15day500mbHeightAnomalyNH.gif

Probably over-doing it on today's evidence but does emphasise that this unlikely to see a rapid decay to the ridge to the north-west.

[bluearmy]

cant work out why anyone is surprised by the 00z's. looks pretty consistent to me. with us likely to be on the edge of cold/less cold, we will see the ebbs and flows from the nwp. by the way, disturbances running south look to have warm sectors and you remember how complex that was the past two cold spells, with colder uppers entrenched.

chio will be chuffed to see the immediate downwelling. he does feel that an ssw can often have a short sharp initial effect followed by a more lengthy reversal a few weeks later.

Edited January 24, 2010 by bluearmy

[Mr.Plow]

So one full set of runs point to a colder outcome. (Is that including the ensembles?)

Presumably it could all still change next run? Or does the model agreement inspire much more confidence.

One thing about the models this year is the upgrading of cold closer to the time, feels like the (polar)opposite of previous years.

I think the 06Z GFS and all of the 12z models are going to be awaited with crossed fingers this morning.

[Frosty.]

Yes, this --->

http://cawcr.gov.au/bmrc/clfor/cfstaff/matw/maproom/OLR/m.3d.html

Tropical convection just east of the Dateline.

And this ---->

More or less instantaneous downwelling from the warming stratosphere.

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

The GFS ensemble mean is keen to maintain heights to the NW, even days 11-15 show a positive anomaly close to southern Greenland:

http://raleighwx.easternuswx.com/models/gfsensemble/00zENS11-15day500mbHeightAnomalyNH.gif

Probably over-doing it on today's evidence but does emphasise that this unlikely to see a rapid decay to the ridge to the north-west.

This should all make for an interesting countryfile forecast and meto update today with such amazing cross model agreement for an Arctic Blast, I also think this fits in with Fred's prediction too. If these or similar charts verified then we will be looking at a spell every bit as severe as the recent one but of shorter duration of course.

[Shunter]

NOAA early comments here......

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

[John Snow]

Looks like the severest snow of the winter for especially the northern half of Britain towards the end of next week with possibly feet of the stuff over the northern hills with drifting in gale force winds

What a shocking turnaround this morning.

[nick sussex]

NOAA early comments here......

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

Looking at their comments they suggest the eastern USA trough to breakdown and weaken, we basically want that trough to hold as long as possible as that keeps the block further north, once the trough weakens we're likely to see a ridge of high pressure coming out of that region which then helps our high to topple.

[TEITS]

Well I have to admit to being amazed at the model output this morning. I have no problem in admitting that I could of got this entirely wrong, although that wouldn't be a first.

What im amazed at isn't so much the strength of the N,ly but the length of this and what follows after. As you know i've been saying what the models have been progging never happens and this always results in a 48hr N,ly followed by a toppler. However the sinking HP with LP tracking to the N of the UK isn't being suggested by the GFS.

As an example look at the SLP mean for Iceland. Now if we we're to see a sinking HP with deep LP systems tracking to the N you would expect the SLP mean for Iceland to be around 990-1000mb. However as you can see the mean is 1020mb!

http://charts.netweather.tv/ensimages/ens.20100124/00/prmslReyjavic.png

We can also see this in how cold the ensembles are for Cambs with the mean never rising above -5C.

http://charts.netweather.tv/ensimages/ens.20100124/00/t850Cambridgeshire.png

So beyond the N,ly there is the chance of N,ly reloads.

[john mac]

Looking at their comments they suggest the eastern USA trough to breakdown and weaken, we basically want that trough to hold as long as possible as that keeps the block further north, once the trough weakens we're likely to see a ridge of high pressure coming out of that region which then helps our high to topple.

So its not looking that good for us then, the models look great but we should only take them at face value. The last thing we want is for the high to sit over us, mind you id rather that than raging swesterlies.

[derrylynne]

Looking at their comments they suggest the eastern USA trough to breakdown and weaken, we basically want that trough to hold as long as possible as that keeps the block further north, once the trough weakens we're likely to see a ridge of high pressure coming out of that region which then helps our high to topple.

I always find it amazing to read often statements such as ' we basically want'. Nothing to do with the charts as are. Basically want depends on which side the fence you are - mild or cold - so does not apply to we want. I would basically want a Bartlett high as that would bring mild into the 50's F temperatures as I like warmth and small heating bills.

However onto the model charts and there is nothing warm about the charts, and nothing has been shown that could be classed as warm. With the cold air so close the the UK a cold outbreak is always going to be likely - and indeed it does look as though we will be getting a cold northerly with snow for many in the near time span. Nothing to indicate a cold spell such as we have had, and I would be surprised to see such a long cold outbreak although we could get a short but more intense cold spell during February - something solar techniques show - but of course nothing to do with the charts at the moment. A lot of talk of February delivering colder and more snow in that month of late? Really - if my memory serves me right February for quite a while has been a warmer month than January - and my weather station records bear that one out. This is not what is termed a 'even larger teapot' - the charts are the kind of charts that were often what we were seeing in the 60's and 70's - but it has to be remembered that even though we suffered severe blizzards and cold spells in them times - apart from 1962/3 there were quite often mild rainly spells mixed in with these..

[cooling climate]

Much better agreement this morning on a potent northerly later in the week and I still

believe the breakdown shown by the GFS and ECM is premature.

With the tendency for northern blocking to increase (-AO ) and the splitting and weakening

of the vortices's an extended cold, very cold wintry spell looks on the cards to me.

The MMW and northern blocking will dictate the pattern enhanced by favorable MJO and

convection around the date line.

The UKMO northern hemisphere charts show the very likely continuation of a very cold

pattern for Europe and the UK.

[Cecil Hogmanay Melchett]

Yes, this --->

http://cawcr.gov.au/bmrc/clfor/cfstaff/matw/maproom/OLR/m.3d.html

Tropical convection just east of the Dateline.

And this ---->

More or less instantaneous downwelling from the warming stratosphere.

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

The GFS ensemble mean is keen to maintain heights to the NW, even days 11-15 show a positive anomaly close to southern Greenland:

http://raleighwx.easternuswx.com/models/gfsensemble/00zENS11-15day500mbHeightAnomalyNH.gif

Probably over-doing it on today's evidence but does emphasise that this unlikely to see a rapid decay to the ridge to the north-west.

Nice update chief, Certainly its beginning to look like maybe a 3 or even 4 day Northerly is on the cards.

Stu,why do you think we are seeing instant downwelling?I was under the impression downwelling takes weeks or even months?

Anyway,gfs is better today and the ens look to have flipped to cold right out until the end.

[KTtom]

Everything a little further NW on this run so far, expect a decent upgrade on the initial northerly.

[nick sussex]

So its not looking that good for us then, the models look great but we should only take them at face value. The last thing we want is for the high to sit over us, mind you id rather that than raging swesterlies.

No the models are fine, the eastern USA trough was always likely to breakdown once the western USA ridge weakened. In terms of the northerly the trend is good and the gfs 06hrs run is likely to be an upgrade given the early signs.

After the high topples is still the area of uncertainty,given the teleconnections we might keep this far enough north to stay on the cold side, overall things are looking much more positive this morning.

[Cecil Hogmanay Melchett]

We won't be seeing anything like that. The GFS is synoptically highly unlikely; Low pressure would develop off S Greenland and topple the High. Many northerlies of this type over the years have seen maximas in the 7 to 9 range for coastal Southern areas particularly. I'm still favouring a quick toppling and a mild early Feb.

Im kind of with you ian,i have never known a mid atalntic high produce anything other than a toppler in all the years of watching NWP.

Still,lets not prejudge anyoutcome.GP update suggests the effects of the warm startosphere might be already starting!

[BLOWERS]

So its not looking that good for us then, the models look great but we should only take them at face value. The last thing we want is for the high to sit over us, mind you id rather that than raging swesterlies.

Maybe that explains (the 'face value' bit) why the 06Z GFS has almost as much pink on it - from later today and through Monday - as the old British Empire maps. Yet, bizarrely, BBC radio and TV forecasts this morning don't even HINT at any snow for England! I did hear 'chance of wet snow on the Scottish mountains', but how can the two be so contradictory? Is the current set-up REALLY so hard to work out? Maybe it is...

[john mac]

No the models are fine, the eastern USA trough was always likely to breakdown once the western USA ridge weakened. In terms of the northerly the trend is good and the gfs 06hrs run is likely to be an upgrade given the early signs.

After the high topples is still the area of uncertainty,given the teleconnections we might keep this far enough north to stay on the cold side, overall things are looking much more positive this morning.

Thanks very much for that Nick, just wanted to check with you before i started getting my hopes up.