Model Output Discussion 13/11/12 18Z onwards

[bluearmy]

Trend from the 00z is to take more energy into the southern arm. All positive stuff for surface cold but can we get to upper cold ?

[Frosty.]

The Gfs 00z op run shows a wintry end to the month with a Northerly, not the first time the gfs is showing an arctic spell for late november into early next month and it's usually pretty good at spotting cold outbreaks in FI. However, a lot of things have to fall into place first, this weekend will turn cooler as heavy rain clears east and followed by sunshine and showers, wintry showers on northern hills, a frost saturday night then sunday looks fine and chilly with another frost sunday night, the north and west turns unsettled and windier next week, the south and east is less unsettled and gradually turning milder again, a brief colder and showery nw'ly is followed by a big pressure rise with a spell of frosty and foggy weather but then the high pulls west and a deepening low introduces a wintry blast later.

[Ian Brown]

Trend from the 00z is to take more energy into the southern arm. All positive stuff for surface cold but can we get to upper cold ?

I would say no based on the output this morning. The modelling is trending towards a mid-latitude HP of some description beyond T200, I think the only way to win from there if retrogression to Greenland can take place which the GFS OP shows in the deepest reaches of FI.

It's a long way from Nov 2010 which of course was pretty exceptional, but it could be a lot worse.

[Severe Siberian icy blast]

I would say no based on the output this morning. The modelling is trending towards a mid-latitude HP of some description beyond T200, I think the only way to win from there if retrogression to Greenland can take place which the GFS OP shows in the deepest reaches of FI.

It's a long way from Nov 2010 which of course was pretty exceptional, but it could be a lot worse.

Thanks ian

[Frosty.]

The first thing to say is that the 0z from GFS, after showing some milder OP runs has gone full circle and is now a cool/cold outlier (in FI running about 5c below the mean):

Yes but the 6z and 12z have been showing an arctic spell later this month and now the 00z is, I think there is some confidence gathering for a colder end to the month. If the next alternative is cool/cold zonal, not a bad 2nd prize really. I can't see much mild weather in the next few weeks.

Edited November 15, 2012 by Frosty039

[Gibby]

Good morning. Here is the latest look at the 00zs from GFS, UKMO,GEM and ECM for today Thursday Noveember 15th 2012.

All models show a similar pattern through the next 7 days. The current quiet and merky conditions will continue for the next 24 hours before a Southerly flow develops ahead of a cold front moving in from the West later tomorrow. A band of rain will move East overnight tomorrow and on Saturday morning, heavy in places. Over Saturday as the front exits East colder and clearer conditions follow with some wintry showers in the NW for a time. After a frost on Saturday night for most as a ridge moves East through Sunday winds freshen from the SW markedly early next week. All models then support several days of fresh to strong SW winds and spells of rain mixed with colder and showery weather up until the middle of next week.

GFS then takes Low pressure gently East over Northern Britain dragging colder polar maritime air South over the UK turning rain or showers wintry over Northern high ground later in the week. Over the weekend a High pressure area moves into the UK bringing cold and sunny conditions with very frosty nights. Fog as well becomes a common feature of the UK for a while into the new week before the end of the run sees High pressure pull away West opening the floodgates to a very cold Northerly flow with showers or longer spells of rain, sleet or snow (some appreciable) in many places to end the run.

The GFS Ensembles shows the operational as expected as being a cold outlier. The general trend is for uppers to steadily cool over the coming two weeks with the chance of rather chilly weather developing by the end of the run with perhaps less in the way of rain following next week's wet weather.

The Jet Stream shows the arm relevant to the UK currently running East just to the North of Britain sinking South over next week with the main thrust moving East over France and Spain before splitting North and South over Europe.

UKMO at 144hrs shows Low pressure South of Iceland with a strong SW flow turning Westerly through the day as a cold front crosses East next Wednesday. Rain in association with the trough would cross the UK followed by colder weather with sunshine and showers in the West.

GEM shows a dominant and monster Low pressure over the North Atlantic by day 10 with continuing changeable and often wet conditions under troughs crossing East with just short transient ridges bringing cooler and more showery conditions in between.

ECM shows Low pressure to the NW at day 6 gradually moving Eastwards with a cold pool developing over the UK as the thrust of Low pressure slips South to end the run to the South of the UK. Then as High pressure ridges from the North Atlantic across the far North to Europe Southern areas remain unsettled as a cold Easterly flow develops with some cold, raw and cloudy conditions likely while the North trends brighter and colder.

In Summary next week looks a fairly wet affair with Low pressure out to the NW spawning new disturbances which run NE through the course of the week bringing spells of rain and some colder showery inerludes too. As we move into week 2 it looks like a trend to colder conditions is likely from the NW with Low pressure moving East as well as sinking SE with pressure rising behind to the west and North. By the end of it's run GFS shows us a cold and unsettled look, a pattern which covers all of NW Europe at Day 15. A direct attack of cold from the East is looking quite unlikely now as the High to the East is pushed gently further East in week 2 by the Eastwards movement of the trough over the UK. What is possible imo is a trend towards a UK High similar to what is shown by GFS and hinted at by ECM at day 10 in the days that follow leading to UK borne cold weather with frost and fog major players in the weather experienced over the UK.

[Nick F]

Trend from the 00z is to take more energy into the southern arm. All positive stuff for surface cold but can we get to upper cold ?

Given the block to the east doesn't look to shift much, keeping cold pooling way to the north and the northeast, it doesn't look too hopeful right now. Heights still progged to be rather too low at high latitudes.

Indeed a cool continental flow with overnight frosts and perhaps some inversions best to expect if we get an easterly as the Atlantic trough undercuts.

Edited November 15, 2012 by Nick F

[AWD]

This secondary depression looks like it could bring some strong winds to southern & western facing coast during Sunday & Monday;

http://www.wetterzentrale.de/pics/brack4.gif

http://cdn.nwstatic.co.uk/gfsimages/gfs.20121115/00/102/airpressure.png

http://cdn.nwstatic.co.uk/gfsimages/gfs.20121115/00/102/ukwind.png

Edited November 15, 2012 by AWD

[Glacier Point]

I wouldn't worry about cold source Nick.

Another very consistent NAEFS 00z, in tune with 12z and CPC prognostic developing moderate level anomalous ridge over southern Greenland / North Atlantic week 2 and dropping the longwave trough to our south as heights build to the north. Given the excited state of the NAO this year, ridge to our NW should be sharp enough to draw down Arctic air source into Scandinavia.

Edited November 15, 2012 by Glacier Point

[Barry12]

I wouldn't worry about cold source Nick.

Another very consistent NAEFS 00z, in tune with 12z and CPC prognostic developing moderate level anomalous ridge over southern Greenland / North Atlantic week 2 and dropping the longwave trough to our south as heights build to the north. Given the excited state of the NAO this year, ridge to our NW should be sharp enough to draw down Arctic air source into Scandinavia.

Hi GP

It's looking good for a beast from the east, models very consistent.

Edited November 15, 2012 by Barry95

[SMU]

http://www.knmi.nl/e...agse/index.html

A very good trend now developing in the ECM suite- the mean dropping out to 4C at the end- with a few sub zero runs. Which cannot be Northerlies-

Difficult times for the models with the a sharp modality change across the NH, we will end up with HP over Scandi & another ridge towards Greenland,

Another day or 2 though before we get into the UKMO et al- what high pressure will be the first to the Winning post!

S

Edited November 15, 2012 by Steve Murr

[Nick F]

I wouldn't worry about cold source Nick.

Another very consistent NAEFS 00z, in tune with 12z and CPC prognostic developing moderate level anomalous ridge over southern Greenland / North Atlantic week 2 and dropping the longwave trough to our south as heights build to the north. Given the excited state of the NAO this year, ridge to our NW should be sharp enough to draw down Arctic air source into Scandinavia.

Looking at the 00z ECM ensemble mean at T+240 - there is emphasis on digging a negatively-tilted trough SE across western Europe - which would certainly point to height rises to the NE, though it's too far off for me to feel confident that everything will then fall into place to get an easterly delivering deep cold. Many more runs needed.

Edited November 15, 2012 by Nick F

[Frosty.]

How about a Northerly instead? the gfs has been showing an arctic spell on and off for end of month and it would be more potent by late november, the ecm 00z easterly is not cold because europe is dominated by mild yellow T850's.

[johnholmes]

In my view, others will differ, I still believe the first upper ridge will be to the NW not the NE or E.

[Nick F]

How about a Northerly instead? the gfs has been showing an arctic spell on and off for end of month and it would be more potent by late november, the ecm 00z easterly is not cold because europe is dominated by mild yellow T850's.

Well that would certainly be a safer and more reliable route for deep cold by then, but reliant on the eastern block relaxing its grip and allowing troughing to move in across Scandi - which is not totally out the question looking at the 00z GEFS H500 mean .

Edited November 15, 2012 by Nick F

[Frosty.]

In my view, others will differ, I still believe the first upper ridge will be to the NW not the NE or E.

Meaning we are more likely to get a Northerly than an Easterly?

[UV-RAY]

Meaning we are more likely to get a Northerly than an Easterly?

I would agree with John too me any blocking looks likely to be to our NW, so any cold will be from a N/NE direction I would have thought.

[Bristawl Si]

I would agree with John too me any blocking looks likely to be to our NW, so any cold will be from a N/NE direction I would have thought.

GP's been v bullish and consistent with his view in the last week or so - i'll stick with his view.

[Frosty.]

I would agree with John too me any blocking looks likely to be to our NW, so any cold will be from a N/NE direction I would have thought.

I would be happy with the result from the Gfs 00z, an easterly is a waste of time if there is nothing cold to tap into, the arctic route is guaranteed cold so hopefully the gfs will keep showing it occasionally, it's a good trend spotter despite it's flaws.

[Buzz]

How about a Northerly instead? the gfs has been showing an arctic spell on and off for end of month and it would be more potent by late november, the ecm 00z easterly is not cold because europe is dominated by mild yellow T850's.

I keep seeing people say this, but it doesn't matter if the easterly is allowed to establish itself - get the easterly first and the cold will filter through to Europe then the UK within a few days.

Edited November 15, 2012 by Buzz

[EML Network]

I don't really know what to make of this set up, High pressure seems to extend well into Russia, all the way through Europe, exits through Spain and then ridges underneath that Low to our West all the way into Canada.

I can't help but feel that if this set up remains, then were going to be stuck in a pattern with Low pressure stalling out West, with no where to go and we end up in no mans land once again...I'm not expert enough to know what happens after that, but there doesn't look like very much cold to our East to tap into, Eastern Europe seems remarkably mild for the end of November.... or am I reading this all wrong ????

[johnholmes]

Meaning we are more likely to get a Northerly than an Easterly?

yes Frosty that is my current belief based on the 500mb anomaly charts and factors like AO, NAO MJO etc, not that the latter 3 are all that supportive at the moment! For early December, which is about where day 20 would be then links further out such as the Stratosphere are going to have negligible effect in my view whatever they show in the current actuals or their forecasts. Mind you that is my view and some will probably disagree with that.

I spend a fairly large amount of time looking at the various anomaly charts, every day and do feel they offer a pretty reliable guid out to about day 16 possibly extrapolating them to around day 20. 12 months of daily watching and checking shows about a 70% success rate in the 10-16 day time frame.

That success is at 500mb-what happens in the 18,000 feet below that is not necessarily going to be as close but the guidance is there.

Edited November 15, 2012 by johnholmes

[Frosty.]

I keep seeing people say this, but ut doesn't matter if the easterly is allowed to establish itself - get the easterly first and the cold will filter through to Europe then the UK within a few days.

Yes Buzz, it's only my opinion but the ecm 00z at T+240 left me feeling very underwhelmed, even if we got an easterly then, we might lose it before any cold sourced air could reach us, a northerly at this time of year is a sure fire cold snap or spell so i'm hoping for something similar to the gfs 00z, the ecm easterly is a toothless waste of time unless it upgades significantly.

[Tom Montalbano]

I think part of the problem is upstream over the Eastern U.S, watching run from NH perspective and the pattern is stagnant with high over S.E.States.

Last few frames suggest trough forming over E.Seaboard, this should change the pattern for us.

That persistant upper ridge Aleutian/Kamchatka still going strong.

Regards,

Tom.

[Nick F]

yes Frosty that is my current belief based on the 500mb anomaly charts and factors like AO, NAO MJO etc, not that the latter 3 are all that supportive at the moment! For early December, which is about where day 20 would be then links further out such as the Stratosphere are going to have negligible effect in my view whatever they show in the current actuals or their forecasts. Mind you that is my view and some will probably disagree with that.

I spend a fairly large amount of time looking at the various anomaly charts, every day and do feel they offer a pretty reliable guid out to about day 16 possibly extrapolating them to around day 20. 12 months of daily watching and checking shows about a 70% success rate in the 10-16 day time frame.

That success is at 500mb-what happens in the 18,000 feet below that is not necessarily going to be as close but the guidance is there.

John, I feel your current belief for height rises to the NW is as equally as valid as the belief of those going for height rises to the N/NE. One thing which is becoming more sure, is that the stagnant long-wave pattern this side of the northern hemisphere looks to finally be on the move by the month's end. Whether it is the long wave disrupting and digging SE into W Europe allowing height rises to the NE or the whole wave edges east of the UK to allow height rises to the NW.

Edited November 15, 2012 by Nick F