Model output discussion - 20th Feb onwards

[winterof79]

Euro4 says no to snowfest Friday

 

[karlos1983]

my interests turn now to this little feature showing on GFS and ECM @ +120 and where it ends up.

ECM shows decent uppers at the same timeframe.

 

 

Edited March 2, 2016 by karlos1983

[Fred Sykes]

19 minutes ago, winterof79 said:

Euro4 says no to snowfest Friday

 

Perhaps it might start as rain, but it will increasingly turn to snow as the system draws in air from the east 

[knocker]

22 minutes ago, karlos1983 said:

my interests turn now to this little feature showing on GFS and ECM @ +120 and where it ends up.

ECM shows decent uppers at the same timeframe.

 

 

 

The little feature is west of Stornoway 12 hours later before being zapped by the ridge.

[Banbury]

Hopefully something wintry later

[joggs]

10 minutes ago, Banbury said:

Hopefully something wintry later

Totally overdone there re snow imo.

[MR EXTREMES]

Not a lot of optimism from me today continued mixing out of colder uppers still interest in seen for northern areas especially inland midlands north northwest and north east.

as stated few days back mlb topples towards the uk.

possibilty of settled cold nights average or slightly below temps moving into the later parts of the run coldest part being from middle part of the model outputs.

but still not convinced the wintry saga is over as we still need to wait and see what effect the strat warming has further on onto March although I feel it's all bit to late to really have to much of an impact on half of the Uk especially southern half.

its certainly followed the trend of the last few winters almost but no cigar.

 

 

[knocker]

The ecm is showing some significant snowfall 00-12z Friday for NW England stretching SE to the Midlands and the Wash. Now you see it, now you don't.

Edited March 2, 2016 by knocker

[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 WEDNESDAY MAR 2ND 2016

THE CURRENT GENERAL SITUATION   A depression will move SE across the North sea today with a complex trough structure attached to it moving SE across the UK today in a cold and very strong NW flow gradually weakening tonight and tomorrow as a new trough approaches the west from off the Atlantic by then.

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

CURRENT SNOW FORECAST AND FREEZING LEVEL OVER THE UK The freezing level across the UK will in general be around 2000ft but will change downwards towards sea level as squally wintry showers pass giving snowfall right down to sea level in the heaviest showers and settling snow possible above 1000ft.

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

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

MODELS-2 WEEK HEADLINE  Rather cold and breezy with rain or showers at times with snow on hills. Perhaps drier later. Temperatures mostly rather below average with frosts at night in places.

THE GFS JET STREAM FORECAST  The Jet Stream is blowing strongly SE or South across the UK and France and it remains moving South in this position for the coming three or four days weakening and buckling over the weekend as pressure builds in from the West. The flow then becomes much lighter and variable next week with the main emphasis supporting the flow wanting to remain South of the UK later in response to a pressure rise over Europe. 

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

GFS OPERATIONAL The GFS Operational Run today shows cold weather for the UK in the next 7 days as depressions run SE across the UK in the next 48 hours and then more slowly away east over the weekend and start to next week maintaining a cold and Northerly source to the winds across the UK with sunshine and scattered wintry showers and eventual frosts at night. Another disturbance running South over western Britain at some point over the weekend threatens more general rain or snow for a time in the West before the ridge to the West and NW topples across the UK with a fine day or two before a change to SW winds and milder air for a time next week with rain at times especially in the North. Towards the end of the run pressure is High over Europe and Low pressure moves into the UK engaging with cold air across parts of Europe and from the NW meaning a return to complex and cold Low pressure across the UK with rain or snow in places in two weeks time.

GFS CONTROL RUN The Control Run's theme is almost identical to the Operational Run in Week 1 detailing a delay in the ridge moving in from the West now until towards the middle of next week so cold and unsettled weather is expected through this period. Then as the ridge finally moves across midweek it declines rapidly with a milder West or SW flow becoming established with rain or showers across the UK at times in the second week though this run demonstrates rather less cold conditions possible later when compared to the Operational Run.

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 again today offer no real clues in the weather likely across the UK in two weeks time with a very mixed pattern likely across the UK shown this morning  which could bring us mild or cold and wet or dry so these offer very few clues on what is likely.

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 continues to project a cold period of weather to come. As the Friday Low pressure slips away to the SE at the weekend it's slow clearance East makes for a cold North wind across the UK at the weekend with wintry showers and night frosts. Further disturbances in the flow could threaten further more prolonged rain r snow in places for a time before the ridge which is all the time to the West finally makes it's move into the UK by Tuesday with fine and frosty weather looking more likely with any showers then restricted to the far SE.

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

THE FAX CHARTS The Fax Charts today show a close proximity to the raw data run this morning with cold and complex Low pressure type synoptics offering the heady mix of rain and snow in places with a cold northerly flow developing at the weekend as the Low pressure areas drift away towards the SE and East.

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

GEM GEM today shows a slight extension to the cold synoptic pattern too this morning as low pressure moving SE over the UK on Friday is slow to clear East leaving a cold Northerly flow in it's wake with further disturbances running South in the flow enhancing wintry showers at times for some areas.as they pass. It's not until towards the middle of next week the ridge to the West collapses across the UK bringing drier and eventually much less cold weather later next week with WSW winds and rain at times especially in the North and West establishing itself by the second weekend.

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

NAVGEM NAVGEM shows no true break in the cold or rather cold conditions at all in it's run today with the complex Northerly flow at the weekend and start to next week bringing plenty of wintry showers especially in coastal areas and a few longer spells of rain or snow too. A ridge of sorts does make inroads into the UK towards the middle of next week but troughs to the West running into it and disrupting in situ offer up more cold rain and hill snow in places.

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

ECM ECM this morning follows the general theme too of cold and unsettled conditions under Low pressure to the East of the UK through the next 5-7 days with High pressure trying desperately to displace Low pressure as it moves slowly in from the West finally doing so by the middle of next week with the cold Northerly feed displaced by strong and milder Westerly winds and unsettled conditions later next week as the more traditional UK pattern of High to the South and Low pressure to the North establishes. 

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

ECM 10 DAY MEAN The 10 day mean chart continues it's rock steady support for milder and well established SW winds and rain at times for all across the UK at that time.

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

NOTABLE TRENDS & CHANGES FROM PREVIOUS RUNS The pattern between the models shows cross model support for the next week before differences shown on the timing and extent of a change to milder Atlantic winds is indicated between the models and ensembles thereafter.

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 at 99.5 pts and GFS at 99.4 pts.  At 3 days ECM is leading with 97.6 pts to UKMO's 96.9 pts while GFS lags behind at 96.3 pts. At 5 days ECM leads with 90.8 pts to UKMO at 88.8 pts and GFS at 87.0 pts. Then at 8 Days ECM has the leading spot from GFS with 67.0 pts to 63.9 pts. Finally at Day 10 GFS has the lead from ECM with a score of 50.6 pts to 48.7 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  I think the cold period we have just entered into is shown to persist a little longer from within this morning's model outputs. The low pressure area moving SE over the UK on Friday with it's cocktail of rain and snow followed by wintry showers in a Northerly flow is shown to release it's grip more slowly than previously drawing down further disturbances across the UK over the weekend and start to next week from the North or NW. This then is replaced by a weakening ridge of High pressure moving East across the UK towards the middle of next week with fine and frosty weather for a day or so before there seems reasonable support between the operational's that milder Atlantic westerly winds and rain at times takes over thereafter. With High pressure then shown by some output shown to lie to the South from ECM and GEM in particular there seems little chance of a return to colder synoptics at first sight but deep within the models are less clear cut chances of milder air as GFS in particular shows in it's output and bearing in mind that this model is performing better than ECM at the 10 day point in it's verification stats leads me to believe that the chance of milder air later next week is very real but by no means not a done deal and more runs are needed before we can be definitive that's the way the dice is going to fall later next week. meanwhile we can settle into a week of chilly and rather typical March weather with some bright early Spring sunshine mixed with cold winds, frost at night, some bands of rain and snow plus wintry showers scattered about across the UK on most days in the next week.         

Next Update Thursday March 3rd 2016 from 09:00

[knocker]

 

[Summer Sun]

GEM again something milder later next week

ECM is also trying its best to bring in some milder air but we still have some colder air mixed in

 

[mushymanrob]

9 hours ago, Timmytour said:

Personally I've seen JH hit the jackpot with his calls too many times to ever dismiss his thoughts....I've learned not to get excited by great looking charts if his interpretation of the anomaly charts don't back them up....and likewise if he senses something changing for the better in them (by which I mean cold and snow potential), then I allow my hopes to get up

spot on, and those of us that have looked into them agree with what john has said. of course they are not infallible, they are inaccurate sometimes, but not as inaccurate as the ops for the timeframe.

the noaa's are currently at odds with the ops, the ecm keen to bring the azores ridge across our south, the 00z gfs suggests a scandinavian high by day 10. the noaas keep the azores ridge to our west, troughing over the mediterranean . so great uncertainty ahead, but its looking below average/cool.

Edited March 2, 2016 by mushymanrob

[johnholmes]

copied below are the anomaly charts, some seem to think they are not that much use, so take them or leave them.

To me they suggest no major change from the current set up over 6-10 days. Some suggestion of the upper ridge being close enough to the UK in the 8-14 day time scale for a more anticyclonic trend, no sign of any prolonged mild though, temperature a bit below average at best if one takes the mean daily value (avge of Max and Min). Beyond 2 weeks well that has never been my area of confidence.

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

http://www.cpc.noaa.gov/products/predictions/610day/500mb.php

[Banbury]

1 hour ago, joggs said:

Totally overdone there re snow imo.

That's falling snow.................not what's laying on the ground - time will tell

[Man With Beard]

21 minutes ago, knocker said:

 

So model accuracy is actually better in the winter than summer? Or has the zonal nature of the past three winters made it easier for the models?

[knocker]

7 minutes ago, Man With Beard said:

So model accuracy is actually better in the winter than summer? Or has the zonal nature of the past three winters made it easier for the models?

Are you assuming zonal over the whole of the NH?

[MKN]

50 minutes ago, Banbury said:

That's falling snow.................not what's laying on the ground - time will tell

Those charts are very misleading as sleet is shown as snow. We wont see snow as widespread as shown there

[knocker]

Looking at the ecm this morning signs next week that as the HP edges east and the mid Atlantic trough develops that the upper flow will back W. Thus after a brief interlude of more settled weather a return to unsettled in the north in particular but at least the temps edging up to nearer average.

I'll need to let Sidney know as he's opted out while this inclement stuff is around.

[Nick F]

Been looking at the extended 00z EPS and 00z GEFS 500 hPa mean and anomaly charts out to days 15 and 16 respectively and they both indicate a shift of the trop PV over eastern Siberia west across Russia toward. Europe as we head into Mid to late March. This corresponding to height rises over Greenland, Iceland and the Canadian Arctic.  This was indicated by the EC32 out a few days ago too.

here's the GEFS mean and anomaly at 500 hPa for days 10, 13 and 16, can't show EPS mean/anomaly d10-15, but show similar movement of the Siberian PV.

so although we see the trop PV edge down from Greenland next week backing the wind westerly with less cold/mild conditions returning, don't think we have necessarily seen seen the back of wintry potential for the rest of Spring. 

The return to milder could be temporary. A major SSW being touted and this could be the effects on the NH pattern to unfold, I see there are comparisons to March 2013 being discussed on Twitter too:

 

Edited March 2, 2016 by Nick F

[Singularity]

Look at that low to the west of the Azores High. We need more of a ridge ahead of it, with a break in the jet between that area and the trough over Iceland, which would mean a chance the system becomes cut-off and supports a ridge to its NE i.e. in the mid-Atlantic.

For that we can look at UKMO:

The slower that low is to arrive, the better the chances of something like UKMO suggests - though it still looks a bit too flat over the U.S. to avoid the low merging with the next incoming trough.

To improve our chances, we need more amplification to the flow. 

This needs watching later this afternoon to see if the MJO has moved into phase 8 with decent amplification or not. 

Then comes a defining period really - if the MJO decays as ECM shows then increasing westerly momentum will encourage the faster upstream lows and flatter Atlantic pattern prior to the SSW having whatever impact it does. GEFS is a bit better but only really in the longer-term, with a short term loss of activity also suggesting added westerly momentum to the polar jet.

 

The flatter pattern has other consequences too; cold, unstable air is locked in across Greenland/Canada more, which is why the det. runs are showing a distinct trop. vortex over Greenland that is entirely independent of the stratosphere. It's a means to escape the cold regime for a few days at least - but not without unsettled conditions for the northwest in particular.

I'm not yet convinced about this milder interlude, but confidence in a persisting cold pattern has waned somewhat.

[Nouska]

1 hour ago, Man With Beard said:

So model accuracy is actually better in the winter than summer? Or has the zonal nature of the past three winters made it easier for the models?

I suspect the accuracy (or not) of tropical cyclone forecasting is playing a part in the lower summer figures.

[Yarmy]

2 hours ago, Man With Beard said:

So model accuracy is actually better in the winter than summer? Or has the zonal nature of the past three winters made it easier for the models?

NH Summer => More Energy => More Active Atmosphere => Less Predictable

 

[cheeky_monkey]

I always thought it was the other way round..bigger temp difference between poles and the tropics in winter therefore more volatile the atmosphere in winter..summer is less difference less active weather more likely longer periods of one weather type during the summer than winter.

[Yarmy]

18 minutes ago, cheeky_monkey said:

I always thought it was the other way round..bigger temp difference between poles and the tropics in winter therefore more volatile the atmosphere in winter..summer is less difference less active weather more likely longer periods of one weather type during the summer than winter.

The seasonal dip is always there.

 

The solar insolation increases during the NH summer and the atmosphere reacts like any fluid by becoming more active and volatile. (Indirectly, as it is more or less transparent to the incoming shortwave radiation, but instead absorbs the outgoing LW radiation from the land and sea surfaces). 

 

Edit: The SH variation is less pronounced because of the lack of land masses. 

Edited March 2, 2016 by Yarmy

[fergieweather]

45 minutes ago, cheeky_monkey said:

I always thought it was the other way round..bigger temp difference between poles and the tropics in winter therefore more volatile the atmosphere in winter..summer is less difference less active weather more likely longer periods of one weather type during the summer than winter.

Winter forecasting in the longer medium range/seasonal sense benefits from some areas of greater predictability, e.g. MJO forcing, which becomes indistinct and ultimately of no forecasting value as we move on into the summer, plus various global teleconnections known to have more distinct influence on winter outcome (as we saw very evident this past winter). Clearly however, in terms of forecasting shorter-range SFC conditions, both seasons have a raft of very differing challenges for the UK.