Model Output Discussions 18z 31/01/2016

[chris55]

As Ian said the other day if the front stalls and fizzles in situ then some lowland snow into Thursday is a possibility.

GFS does exactly this on the 00z

 

[Radiating Dendrite]

To be honest I just don't see it. The showers currently affecting East Anglia are prominently rain and that's in a cold NE airflow.

I think the peak district may see snow; but low lying central areas will surely be rain. Looking at how this winter has panned out I don't expect any surprises. 

[Polar Maritime]

GFS 00z take on Wednesday snow risk..

The GFS also maintains some cold 'wintry' Pm shots into the run from the weekend.

[coldcomfort]

16 minutes ago, Radiating Dendrite said:

To be honest I just don't see it. The showers currently affecting East Anglia are prominently rain and that's in a cold NE airflow.

I think the peak district may see snow; but low lying central areas will surely be rain. Looking at how this winter has panned out I don't expect any surprises. 

Have to agree, the slightly better speed and orientation of the front on the overnight runs does hold out at least a little hope, but frankly I just can't get over enthusiastic about an hour or two of wet snow, which even if it it did settle would quickly get smashed up by the returning Atlantic on Thu-Fri. I guess the amount of interest in midweeks potential event underlines just what a shocking winter this has been for cold and who knows, 10 years down the line we may see similar kinds of excitement over an impending ground frost! Roll on spring now imo. 

Edited February 15, 2016 by coldcomfort

[Gustywind]

17 minutes ago, Radiating Dendrite said:

To be honest I just don't see it. The showers currently affecting East Anglia are prominently rain and that's in a cold NE airflow.

I think the peak district may see snow; but low lying central areas will surely be rain. Looking at how this winter has panned out I don't expect any surprises. 

Edited February 15, 2016 by Gustywind
Presumably that's due to the North Sea though isn't it and the above average temps? That won't be a factor on Weds/Thurs. I remember in Jan 10 ((I think), the east seeing rain off an easterly with colder 850s than now due to the North Sea.

[IDO]

The hi res models have the front(s) stalling as well and it looks like the NW, Wales and W. Midlands are the sweet spots:

Arpege - T44 T80: NMM:

Rain initially and as the fronts die in situ turning more wintry, but looking like mostly light by then, maybe the snizzle variety, with your height above sea level  also being a factor. Still subject to change of course.

Further into the GFS run around D11 onwards there looks to be WAA heading to the Arctic (op and control) so that may get interesting late Feb:

op:  control:Op 850s

Again the axis of cold from the x-flow favours East US and Asia, and we will have to benefit from the PM flows coming off the extreme cold of the conus. Typical of the last few years, just relying on stalling fronts, PM shots and Storms (Frank) to get anything wintry. See how that will develop...

 

 

[shaky]

Upgrades this morning regarding snow midweek!!remember nick sussex mentioning yesterday that if a low could develop near the channel and isle of man then that would be good as we drag in maybe slightly colder dew points!!well guess what ecm has gone and done that at 72 hours and arpege has pretty much looked the same for the last 3 runs!!infact it keeps backing that front further west to such an extent it just about reaches eastern parts of east anglia!!

[fergieweather]

12 hours ago, Karl. said:

i hope March can put this dreadful winter to shame with some snowy spells!...im hoping those GloSea5 members keep showing colder outcomes!

 

During the weekend, GloSea5 trended away from an anticyclonic outcome for early March. However, given MJO cycling through phases 6-7, UKMO assessments continue to offer caveat of "slightly increased chance of blocked/colder conditions" turn of month-early March; i.e. outcome *may* run contra to majority of current ENS from GloSea and EC Monthly (which are either statistically indistinct from climatology or have broadly zonal background signals into 1st half of March). 

Edited February 15, 2016 by fergieweather

[nick sussex]

8 minutes ago, fergieweather said:

During the weekend, GloSea5 trended away from an anticyclonic outcome for early March. However, given MJO cycling through phases 6-7, UKMO assessments continue to offer caveat of "slightly increased chance of blocked/colder conditions" turn of month-early March; i.e. outcome *may* run contra to majority of current ENS from GloSea and EC Monthly (which have broadly zonal background signals into 1st half of March).

Thanks for the update Ian.  I think its a difficult forecast for the UKMO because balancing out the El Nino versus MJO and how much the former modifies the signal. I suspect if some blocking does show up it won't be picked up a long way in advance.

[fergieweather]

Just now, nick sussex said:

Thanks for the update Ian.  I think its a difficult forecast for the UKMO because balancing out the El Nino versus MJO and how much the former modifies the signal. I suspect if some blocking does show up it won't be picked up a long way in advance.

Agreed. And there's enough nearer-term forecasting difficulty to ponder by midweek in any case....!

[feb1991blizzard]

19 minutes ago, fergieweather said:

During the weekend, GloSea5 trended away from an anticyclonic outcome for early March. However, given MJO cycling through phases 6-7, UKMO assessments continue to offer caveat of "slightly increased chance of blocked/colder conditions" turn of month-early March; i.e. outcome *may* run contra to majority of current ENS from GloSea and EC Monthly (which have broadly zonal background signals into 1st half of March). 

Given the current stratosphere forecasts, if it were to be zonal, one would perhaps expect zonality of the colder variety with the Jet on a NW-SE axis with the threat of brief blocking phases by way of an Atlantic ridge.

[Frosty.]

Definite upgrade in snow potential through the midweek period across most of England and Wales on the Gfs 00z op, initially rain but as colder air digs in from the west the main slow moving rain zone becomes more wintry with snow to increasingly lower levels as the front slowly edges southeastwards...good luck fellow coldies!

[nick sussex]

3 minutes ago, fergieweather said:

Agreed. And there's enough nearer-term forecasting difficulty to ponder by midweek in any case....!

Yes I've just seen the UKMO fax charts!   The T72 and T84hrs are particularly interesting for members in here, the shallow low which forms in the Channel and very slow movement east of the fronts. I can't remember the last time I saw this type of set up. Its very unusual and I can imagine a bit of a problem to nail down the detail for the UKMO.

[fergieweather]

6 minutes ago, nick sussex said:

Yes I've just seen the UKMO fax charts!   The T72 and T84hrs are particularly interesting for members in here, the shallow low which forms in the Channel and very slow movement east of the fronts. I can't remember the last time I saw this type of set up. Its very unusual and I can imagine a bit of a problem to nail down the detail for the UKMO.

Yup. Equally, the W'ward shift in snow signal overnight (eg 00z EC, which progs more southern reach of snow risk especially Midlands/E Wales/approx down to M4 and across to Chilterns). Either way, PPN rate will be critical component given sensitivity in this set-up to PPN phase. A key point here is to distinguish between the now moderate likelihood of some areas further south in England seeing snow *falling* versus settling. Likelihood of latter currently looks much lower in HRes accumulation products: mostly above 200m but generally patchy/slight in nature. Tricky all-round. 

[nick sussex]

11 minutes ago, fergieweather said:

Yup. Equally, the W'ward shift in snow signal overnight (eg 00z EC, which progs more southern reach of snow risk especially Midlands/E Wales/approx down to M4 and across to Chilterns). Either way, PPN rate will be critical component given sensitivity in this set-up to PPN phase. A key point here is to distinguish between the now moderate likelihood of some areas further south in England seeing snow *falling* versus settling. Likelihood of latter currently looks much lower in HRes accumulation products: mostly above 200m but generally patchy/slight in nature. Tricky all-round.

Yes I think PPN rates will be important but whats interesting is the waves forming along the front. It could be that some heavier precip develops and that shallow low formation in the Channel could add a bit more energy into the front.  Even though this is only 3 days away theres too much uncertainty for the UKMO to give a detailed forecast.

Quite unusual to see a front which is effecting such a large area from Svalbard to southern Spain:

Edited February 15, 2016 by nick sussex

[Summer Sun]

Big changes by the weekend still on show as we swap the colder air for something much milder

Then like was shown yesterday temps drop back down as we move into W/C 22nd

[Gibby]

HERE IS MY LATEST ANALYSIS USING DATA SUPPLIED BY THE NWP OUTPUT COVERING 5 OF THE WORLDS MOST POWERFUL WEATHER COMPUTERS ISSUED AT 09:00 ON MONDAY FEB 15TH 2016

THE CURRENT GENERAL SITUATION   A ridge of High pressure will move slowly East across the UK today and tonight eliminating the cold Northerly flow over the East. A trough of Low pressure will then advance slowly ESE across Scotland and Northern Ireland later tonight and tomorrow in a strengthening SSW flow.

http://www.wetterzentrale.de/pics/Rtavn001.gif

CURRENT SNOW FORECAST AND FREEZING LEVEL OVER THE UK The freezing level across the British Isles is currently fairly universal at or around 2000ft across the UK. Snow showers in the Northeast will reduce through the day. Freezing levels will rise across Scotland and Northern Ireland tomorrow as rain and hill snow moves in from the WNW.

http://www.snow-forecast.com/maps/dynamic/uk

http://www.natice.noaa.gov/pub/ims/ims_gif/DATA/cursnow.gif

MODELS-2 WEEK HEADLINE  Some rain or showers at times with snow over hills. Temperatures mostly near or somewhat below average though with a few short milder interludes in the South.

THE GFS JET STREAM FORECAST  The Jet Stream lighter than recently will tumble down across the UK over the next few days in association with the UK midweek trough. It then strengthens from the weekend and crosses the East over the North of the UK before the axis moves South again later to lie West to East over Southern Britain and France later in Week 2.

http://www.netweather.tv/index.cgi?action=jetstream

GFS OPERATIONAL The GFS Operational Run today shows a strong ridge of High pressure moving East across the UK followed by a trough of Low pressure moving erratically ESE midweek and bringing rain to many and the risk of some snow for a time for some especially in the East. Following on behind will be a spell of chilly and bright weather before Atlantic Westerly winds bring milder weather to all areas with changeable conditions with wet and windy weather alternating with colder brighter weather with showers especially later in the period.

GFS CONTROL RUN The theme of the Control Run looks quite similar in theme to the Operational Run with a cold working week with rain and snow in places midweek giving way slowly to milder and stronger Atlantic winds and rain at times especially in the North with still the likelihood of some colder interludes in showery NW winds at times as weather systems pass by.

http://www.wetterzentrale.de/pics/Rtavn1441.gif

http://www.wetterzentrale.de/pics/Rtavn3841.gif

http://www.meteociel.fr/modeles/gefs_cartes.php?code=0&ech=144&mode=0&carte=0

http://www.meteociel.fr/modeles/gefs_cartes.php?code=0&ech=384&mode=0&carte=0

GFS ENSEMBLE DAY 14 DATA  The GFS Clusters today continue to support winds blowing from a West to NW direction across the UK in two weeks time with varying degrees of influence from Low pressure always up to the North of the UK. there is some degree of support too that suggests High pressure may be quite close to the South of the UK restricting the worst of wind and rain towards the North. This currently has a level of 25% support from members which is more than yesterday.

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=euro&MODELL=gefs&MODELLTYP=2&BASE=-&VAR=cpre&HH=372&ZOOM=0&ARCHIV=0&RES=0&WMO=&PERIOD=

UKMO The UKMO model this morning shows the midweek trough stalling across the South soon after midweek with an awkward mix of rain and snow over Central and Eastern areas and on the hills. Then the trough weakens towards the end of the week and is given a kick up the backside as milder and stronger Westerly winds blow across the UK at the weekend with some rain for all.

http://www.wetterzentrale.de/pics/Rukm1441.gif

THE FAX CHARTS The Fax Charts today replicate the raw data well and illustrate the complexities of pinning down the detail of the exit east of the trough across the UK midweek. It does succeed however towards the weekend as milder Atlantic winds give it a shove away East into Europe.

http://www.weathercharts.org/ukmomslp.htm#t120

GEM GEM today follows the theme with milder and more changeable mobile conditions developing across the UK from next weekend leading on to an unsettled week next week with rain at times and colder showery conditions in between. The run does show the sinking South of the Jet Stream later bringing the risk of heavy rain equal to all areas next week after prioritising it towards the North in the early days of the week.

http://www.wetterzentrale.de/pics/Rgem2401.gif

NAVGEM NAVGEM shows a much broader trough from the middle of the week with cold weather with some rain and snow in places as the rough decelerates across the UK. milder air does eventually take over through with a more typical Westerly flow across the UK by this time next week with rain and strong winds at times in near average temperatures.

http://www.wetterzentrale.de/pics/Rnvg1681.gif

ECM ECM shows the current ridge declining away East as the trough up to the NW slides in towards midweek with the same mix of rain and hill snow shown by the other output moving across the UK West to East. After lingering for a while over the East and SE the whole thing is swept away east by much milder Westerly winds with rain at times changing to colder and showery conditions at times, this especially towards the North. High pressure is shown close to the South at Day 10 indicating the chance of more settled weather for many at the end of the period.

http://www.wetterzentrale.de/pics/Recm2401.gif

ECM 10 DAY MEAN The 10 day mean chart today maintains the theme of Westerly winds between Low pressure to the North and High to the South and SW likely across the UK in 10 days time with rain at times in the North and West especially and temperatures never that far from the seasonal average.

http://www.wetterzentrale.de/pics/Reem2401.gif

NOTABLE TRENDS & CHANGES FROM PREVIOUS RUNS The overall message is a little mixed but with the theme of milder Westerly winds in 10 days following a messy period when milder air may be delayed for a time through midweek this week remains the main agreements behind today's output.

31 DAY HISTORICAL VERIFICATION STATS FOR GFS, UKMO & ECM The verification Statistics of GFS, UKMO and ECM show at 24 hours ECM ahead at 99.6 pts with UKMO and GFS at 99.5 pts each.  At 3 days ECM is leading with 97.8 pts to UKMO's 97.2 pts while GFS lags behind at 96.7 pts. At 5 days ECM leads with 91.4 pts to UKMO at 89.3 pts and GFS at 88.7 pts. Then at 8 Days ECM has the leading spot from GFS with 69.2 pts to 65.5 pts. Finally at Day 10 GFS leads today at 52.1 pts to ECM's 50.1 pts.

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day1_PMSL_MSL_G2NHX.png

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day3_PMSL_MSL_G2NHX.png

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day5_PMSL_MSL_G2NHX.png

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day8_PMSL_MSL_G2NHX.png

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day10_PMSL_MSL_G2NHX.png

MY THOUGHTS   The main focus of interest in the models today remains the erratic passage of a cold front across the UK midweek and it's subsequent clearance to eventual milder conditions likely to cross the UK from the West at the weekend. This week though sees some very cold air across the UK put in place by a cold NE flow decaying under a strong ridge of High pressure, We then see a cold front up to the NW move East across the UK midweek, decelerating and becoming more complex as potential small disturbances run along it as the cold air across the East proves stubborn to shift at the same time as the air to the West of the trough is none too warm either. However, all models show it all cleared East out of the UK by next weekend as the Jet Stream re-invigorates and moves across the North of the UK bringing milder and at times stronger Westerly winds with rain at times with the emphasis of this being towards the North and West. Then as we move through next week 'changeable' weather looks the best term to use as the pattern of High pressure to the South and SW and Low pressure to the North looks the most likely pattern to verify. All areas will see some rain and also some colder interludes as weather systems pass by with polar maritime air giving some wintriness to the showers in the North of the UK. Looking really long term there seems nothing to suggest any major late Winter cold outbreak with the Jet Stream still dictating the direction the UK weather takes with it's traditional West to East flow not undulating enough or far enough South to open the door to anything more than fleeting cold snaps I'm afraid.       

Next Update Tuesday February 16th 2016 from 09:00

[SMU]

Morning All

I think its been about 4-5 days since I posted - the last time it was showing the snow potential for England at about day 8.

Since then the models should be commended for their consistency around the timing & progess of the front, kudos to them all.

Whats changed since my post ( ironically in the 12's of the day I posted ) was the switch of 2 variables that supported snow - thats was :

* The angle of the WAA off the atlantic into the front 

* The angle & depth of CAA being fired back into the front from the continent-

At the time I posted all parameters were favourable for snow with the theta E values around 8c & a cold pool around -6 @ 850 with sub zero dewpoints

After that day especially the inmediate 24 hours all models moved to a slightly flatter solution -

This then modified all the paratmeters to a place where the signal was rain as opposed to snow-

- uppers modified to -2 to -4 

- Theta values of 8c were ushered east into the continent to be replaced by the 12-14 line & dewpoints moved to be forecast above zero -

 

Since that day the models have ever so slowely edged back to a colder solution but not quite as cold as the initial projection

- the Theta values at day 3 ( T72 / 00z Thurs ) are around 10c

- the uppers in the best case scenario ( UKMO / ECM ) blend are circa -5c in the SE & dewpoints close to zero -

 

So we have gone from all snow to all rain to a very borderline scenario with evaporational cooling the wildcard -

heres the UKMO & ECM for 00z thurs

 

As we can see the cold air does filter back into the SE as the front decays-

So I would say we have a rain to snow event more so possible accumulations to the North at elevation ( as ever )

usual places like the Derby peaks, pennines etc look in the firing line-

futher south more borderline relying on evaporational cooling-

Maybe a surprise for SE ( more especially for the NE part of the region ) - cambridgeshire etc as the PPN feeds into the continental air

For info GFS 00z was the warmest run out the big 3...

aperge also cold with snow....

max snow depth forecast - 10cm at the cat & fiddle

 

S

Edited February 15, 2016 by Steve Murr

[Frosty.]

The Gfs 6z also shows an increasing risk of the slow moving band of moderate to heavy rain turning more to sleet and snow during the midweek period, especially on thursday as slightly colder air digs in from the west, even parts of the south / southeast seeing some back edge snow.

Edited February 15, 2016 by Karl.

[Mark Neal.]

Consistently starting to be modelled across most models now is the threat of Weds rain to turn to sleet/snow towards the backedge of the front through Weds night and into Thursday, even across Central Southern England and into SE. Most likely to settle over elevation further north as Steve Murr alluded too with his cat & fiddle prediction.  Here is a look at the Weather Online charts view of the Precip through Weds and into Thurs.

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=ukuk&MODELL=gfs&MODELLTYP=1&BASE=-&VAR=rart&HH=54&ZOOM=1&ARCHIV=0&PRINT=0&PANEL=0&INFO=0&MOUSE=1

 

Edited February 15, 2016 by Mark N

[Eskimo]

GEM views the warm sector as being slightly more narrow and fills in slightly quicker. Thought it may be worth mentioning as it did pick up the short January cold spell first. 

[Nick F]

A tough call for the rain/snow question along the frontal zone grinding to a halt from Wednesday through Thursday and perhaps not clearing until Friday morning. Really can't forecast accurately the crucial dew points and WBFL to be able to predict snow or sleet/rain in one area ... all comes down to nowcasting when these parameters are knife edge and potential for heavier burst, which can't be assimilated accurately by any model, that may tip the balance of favour of snow rather than cold rain. Whoever gets the snow, it will be a slushy affair if does settle, but beggars can't be choosers in a winter like this, some will be glad just to see it falling!

Doesn't really turn mild (above average temps) until Saturday on the 06z GFS, temperatures back into double figures Saturday afternoon. Then it's back to average temperatures early next week, as we see Pm air return from the NW behind a cold front sweeping SE Sunday night. So by no means are we back into mild long-term, though certainly nothing particularly wintry showing away from northern hills.

Edited February 15, 2016 by Nick F

[Frosty.]

Further into the Gfs 6z run, it's looking generally unsettled and there are repeated polar maritime shots of varying potency bringing wintry showers, night frosts and even some short lived snow events as Atlantic systems bump into the colder air..so the outlook does hold some interest for coldies.

[Man With Beard]

8 minutes ago, Nick F said:

A tough call for the rain/snow question along the frontal zone grinding to a halt from Wednesday through Thursday and perhaps not clearing until Friday morning. Really can't forecast accurately the crucial dew points and WBFL to be able to predict snow or sleet/rain in one area ... all comes down to nowcasting when these parameters are knife edge and potential for heavier burst, which can't be assimilated accurately by any model, that may tip the balance of favour of snow rather than cold rain. Whoever gets the snow, it will be a slushy affair if does settle, but beggars can't be choosers in a winter like this, some will be glad just to see it falling!

Doesn't really turn mild (above average temps) until Saturday on the 06z GFS, temperatures back into double figures Saturday afternoon. Then it's back to average temperatures early next week, as we see Pm air return from the NW behind a cold front sweeping SE Sunday night. So by no means are we back into mild long-term, though certainly nothing particularly wintry showing away from northern hills.

It's like weather pinball this week with that front, isn't it!!

Now I've been reading how it's all going to "back-edge" snow and no front-edge, but can we be sure of that?? I'm noticing this morning a trend to bring colder 850s back towards the SE, especially as the front stalls. Many ECM postage stamps have the -6C 850hpa mark very close to the SE, if not over it - as well as approching from the west.

http://old.ecmwf.int/samples/d/inspect/teasers/samplers/banner/mean_sea_level_pressure_and_temperature_at_850hpa!72!pop!od!enfo!enplot!2016021500!!/

[Lukesluckybunch]

14 hours ago, Lukesluckybunch said:

Yes this evening ecm is quite good,with a lot of the UK still in -4 uppers Wednesday midday..I'm just asking when will the gfs back this,or will it at all..maybe a different looking 18z coming up??

 

14 hours ago, feb1991blizzard said:

I think we are past the point of no return wrt any nationwide event down the spine of the country, its just seeing if the models can just hold back the front for a tiny bit longer and get a few favoured places some snow, it would take too much of a climbdown now at too later stage for anything better.

Hmm I kind of agree,but the interesting thing is it turns quickly colder again behind the front,Thursday has us back in -4/6 uppers nationwide