Model output discussion - 20th Feb onwards

[knocker]

Your usual excellent summary Gibby. Cheers.

[Summer Sun]

ECM this morning shows things slowly turning less cold by months end as the winds shift round to more of a westerly still plenty of cold air before then though

[mb018538]

Very, very tentative signals of the northerly component starting to disappear by the months end. Only baby steps, but something to cling onto either way. Until then it's cold, cold and more cold.

[weather09]

2 hours ago, Penrith Snow said:

Still looks like a potent 8-10 day northerly coming up and with low pressure, low uppers below -5c and late April solar heating, I am expected some big wintry showers 

This is no two day toppler and the atmosphere will be exploding next week under such cold air and solar heating.

If it does 'explode',  it will be due to low geopotential heights and sub -35C air at 500mb, and not the decrease in temperatures at 850mb.  Saturday is modeled to have cold temps at 850mb, but given the proximity of ridge aloft to the west and only gradual cooling with height, thus weak lapse rates, deep convective activity is unlikely.  

Look at the mid and upper profiles in this context - not the low-level atmosphere. 

Edited April 20, 2016 by weather09

[Man With Beard]

A bit fresh this weekend?

[knocker]

The EPS 7-12 anomaly this morning has the upper low north North Sea and and another NE Canada with the Azores HP pushing north mid Atlantic. Thus the upper winds gradually backing to NW but temps still below average. As the run progresses the two lows fill and the HP moves east backing the winds further and although the temps rise steadily they still remain a tad below average.

[andymusic]

GFS 06z cold all the way out to the end of the run

[knocker]

2 hours ago, weather09 said:

If it does 'explode',  it will be due to low geopotential heights and sub -35C air at 500mb, and not the decrease in temperatures at 850mb.  Saturday is modeled to have cold temps at 850mb, but given the proximity of ridge aloft to the west and only gradual cooling with height, thus weak lapse rates, deep convective activity is unlikely.  

Look at the mid and upper profiles in this context - not the low-level atmosphere. 

Indeed. And you will be struggling to get sub -35C, at least at the beginning of the week.

Edited April 20, 2016 by knocker

[weather09]

Yes, only the 00z GFS had the upper trough and deep cold mid-levels dropping over the UK from mid-next week- its 06z output and ECM not going for this, instead having lowest heights, and coldest mid-level air, over N or to the NE.  All too far out anyway for any real confidence.  Though the point I was making (and have made numerous times but obviously not filtering into this part of the forum) was that, in this particular context, cold air at 850mb, alone, doesn't tell the whole story regarding the likelihood of vigorous convective activity, and isn't really relevant.  One should be considering the whole profile (upper trough/ridge pattern) for gauging instability.  Pretty basic stuff.  

Edited April 20, 2016 by weather09

[stodge]

Afternoon all

The question for the medium to longer term remains the strength of northern blocking. GEM this morning kept in firmiy in place right through to the end of next week.

ECM at the same point this morning had significantly eroded the blocking thanks to that shortwave south of Iceland which allowed the Azores HP to ridge NE and a hint of "normal" service returning.

GFS 06Z OP at the same time veering more toward GEM:

A lot of options in the Ensemble Members and not all of them cold or blocked by any means though it has to be said the biggest cluster probably closest to the OP (including both the Control and the Parallel).

There's a solid 5-7 days of not very pleasant weather ahead it has to be said with temperatures well below where they should be and plenty of rain or showers especially for the east and south with snow to higher altitudes more than likely. 

 

[Summer Sun]

GFS switches winds round to more of an easterly as early as Wednesday on this run

The lowest 850's I can find for now are around Tuesday

Nasty looking low pushing up from the south at d10

Edited April 20, 2016 by Summer Sun

[phil nw.]

There has been some fabulous sunshine around for many of us today making it feel really pleasant out there.

A pity the Arctic air is still on it's way,no surprise of course as it's been consistently modeled, and it will be with all of us by the weekend.

Once here that elongated Scandinavian trough and the Greenland heights look like persisting through much of next week with just signs of it's gradual demise near month end. 

The GFS mean at days 5 and 10

 

Looking at the Op runs on GFS/UKMO the cold flow is further enhanced from the north early next week- around day 6- as quite a nasty low develops and moves into the North Sea strengthening the Northerly winds and showery activity especially down the eastern side.

Hopefully the distant signs of something less cold as we enter May appear without any delay and we see a return to some more days like today.

Edited April 20, 2016 by phil nw.

[Summer Sun]

Snow during the coming week is a real possibility for some

The closer to 23 the greater the chance of snow

 

[cheshire snow]

Blimey -10 uppers within touching distance for the far North of Scotland at T168 on this evenings ECM

C.S

[knocker]

As stated previously there continues to be signs of a pattern change end of April/beginning of May but having said that the temps are in no rush to push up to average.

[damianslaw]

After a temporary warmer phase this week, back to the set up we had last weekend come Friday, but this time a protracted well below average cold period is forecast with a robust block of heights to our NW and a pronounced meridional flow with a deep trough feature to our east, end result screaming deep seated arctic northerlies from a long source, hence very cold uppers and means probably a good 4-6 degrees below the norm. The deviation from the average is comparable to what we saw in late July when we had a similiarly cold locked in spell with heights in the 'wrong place'. Nothing unusual for late April, traditionally this is when we see northerlies reach their yearly maxim.

Models are showing a slow transition to a more NW flow as we enter May, still chilly though and most likely unsettled with plenty of showers.

[knocker]

The EPS 8-13 anomaly is similar to the NOAA  and by the 3rd May a slack area of LP to the NW with the Azores HP nudging north to the SW of the UK, The upper flow has backed to the westerly quadrant but this still portends unsettled conditions, perhaps more especially in the north, with temps still below average.

 

Edited April 20, 2016 by knocker

[knocker]

A quick run through of the first 10 days of this morning's GFS.

As expected we get into the circulation of the trough to the west on Sunday with the low that originated way up north now around Stavanger 994mb and the UK in a NW airstream.

During the next couple of days the low travels south to Denmark veering the streamlines over the UK and introducing much colder air with wintry showers, more particularly in the north and east. Cornwall still basking.

Very quickly a new low 986mb, one that has travelled NW from near the Black sea, is in position near near Stavanger where it slowly fills and moves north. Whilst this is happening HP is edging it's way into Ireland and England backing the streamlines westerly.

This heralds the introduction of much warmer air or so we are led to believe. Serious health warnings have been issued.

Edited April 21, 2016 by knocker

[knocker]

The GEFS anomaly still looking at a pattern change in the 8-13 period

[Frosty.]

WOW what a beautiful ending to the Gfs 00z op this morning with an early taste of summer developing through early May with 564 dam heading our way!.

[Summer Sun]

Hints from ECM of the colder air easing towards the end of next week as high pressure gets closer by

Still plenty of chilly weather to get through first though with some snow especially for higher ground and frosts quite possible

[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 THURSDAY APR 21ST 2016

THE CURRENT GENERAL SITUATION High pressure across the North of the UK will slide away to the West over the coming few days. In the South troughs of Low pressure will edge up from the South tomorrow with a stiff NE breeze and then a Northerly flow will then develop across all of the UK over the weekend.

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

CURRENT SNOW FORECAST AND FREEZING LEVEL OVER THE UK The freezing level across the UK is as high as 10000ft across the far South today but over the coming days colder uppers will move steadily South with the freezing level dropping to as low as between 1700ft-3000ft even across the South over the weekend with snow showers on hills above around 500ft at times giving accumulations above 2000ft.

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

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

MODELS-2 WEEK HEADLINE Becoming colder at the weekend with cool nights and sunshine and showers looking likely with a continuing night frost risk thereafter. Perhaps becoming less cold as we enter May.

THE GFS JET STREAM FORECAST  The Jet Stream is in the process of change as the split flow is replaced by a South moving flow from the Northern arm moving down over the UK through the weekend and for much of next week. Then in the second week the flow backs Westerly with it's core to the NW of the Uk through the second week.

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

GFS OPERATIONAL The GFS Operational Run today shows a North or NNW flow developing across the UK over the coming week or so delivering cold temperatures and showers with sleet or snow in the mix along with hail and thunder as well as bright sunshine between times and frosts at night for many. Most of the showers will be in the North and East and the trend will be for less cold weather to develop from later next week as winds back Westerly and High pressure builds near the South towards the May day Bank Holiday with warmer and sunnier weather as a result while the North sees cloudier conditions with some rain.  

GFS CONTROL RUN The theme of the Control Run is less supportive of milder air returning after a week or so of cold Northerlies. Instead it keeps rather cool and very showery weather going for many well into the second week and probably right out until the end of the period as shallow and cool Low pressure is shown to remain close to the UK.

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  It's been some considerable while since the GFS Clusters were instrumental in giving a good indication of what weather to expect across the UK in a couple of weeks and this morning's crop is no exception with High pressure positioned in a variety of positions around the UK along with some Low pressure too offering some rather cool and changeable conditions within the mix.

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 still shows a cold pattern developing as we move through the weekend. The weather will be typified by a mix of sunshine and April showers but those showers will be cold and potentially wintry with frosts at night a common feature for many as skies clear overnight especially in the South and West.

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

THE FAX CHARTS The Fax Charts today show a cold Northerly flow developing across the weekend with sunshine and showers the order of the weather but with some disturbances shown to move South in the flow at times enhancing the showers, wintry on hills almost anywhere by early next weekend.

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

GEM GEM this morning shows a cold Northerly flow too this weekend and next weekend with sunshine and potentially wintry showers by day and frost by night. With time though and later in the period the winds fall lighter and back westerly and with gently rising pressure the showers should die away later next week with the South seeing nearer to normal temperatures by day but still with the risk of frost by night in the by then quiet conditions for many.

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

NAVGEM NAVGEM N/A at time of issue. 

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

ECM ECM today continues to show the same drift into a cold Northerly flow at it'sd peak early next week when winds will be stronger and a day or so of really raw conditions seem possible with widespread showers, strong winds and sleet or snow in those showers on the hills almost anywhere. This then marks the change to less cold conditions later in the week as High pressure builds from the SW killing many of the showers and steadily backing winds off towards the West with much less cold conditions especially by day with sunny spells in the South and any remaining showers restricted towards the NW late in the period.

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

ECM 10 DAY MEAN (12z) The 240hr mean Chart from last night shows the cold northerly flow all but dead by then with winds having backed off towards the West. There are still quite a few members who keep Low pressure in control though with showers especially in the North with the overall bias towards the driest conditions developing towards the South later in those less cold temperatures.

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

NOTABLE TRENDS & CHANGES FROM PREVIOUS RUNS Changes in the model remains slow but there is a continuing shift away from the coldest conditions lasting too long this morning as the theme of milder Westerly winds arriving towards the latter part of the period continues to be shown.

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 99.4 pts and GFS at 99.3 pts.  At 3 days ECM is leading with 97.2 pts to UKMO's 96.5 pts while GFS lags behind at 95.4 pts. At 5 days ECM leads with 88.5 pts to UKMO at 86.4 pts and GFS at 83.2 pts. Then at 8 Days ECM has the leading spot from GFS with 62.6 pts to 55.9 pts. Finally at Day 10 ECM has the lead from GFS with a score of 43.1 pts to 36.6 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 models continue to point towards a colder than average period of weather to come across the UK as winds over the next few days settle Northerly with a mix of sunshine and wintry showers developing across all areas by day with frosts under clear skies at night. the worst of the chill looks like being early next week when a squeeze in isobars make for a windy and raw period especially over the east where more prolonged showers look possible for a time with snow over modest hills. In the South and west a lot of dry and bright weather will occur between more scattered showers in sparkling visibility. Then as we look further ahead the pattern still looks a bit mixed but the general trend of yesterday remains in that there should be a shift away from cold Northerlies to lighter and more importantly warmer Westerlies with the South possibly becoming largely dry and bright while the North sees more cloud and occasional rain. So all in all Winter refuses to lose it's grip next week but it should be it's last hurrah before something more seasonably traditional and Springlike arrives in Week 2 of this morning's output. In the meantime I would strongly advise gardeners and growers to protect or withhold placing tender plants in outside locations for a couple more weeks while the passage of this cold spell takes place. For the rest of us the cold spell will be no more than an inconvenience with some very pleasant looking conditions between the cold showers. Let's hope the improvements shown longer term this morning are enhanced and extended in the upcoming days outputs.

Next Update Friday April 22nd 2016 from 09:00 

[Singularity]

Interesting direction of travel from the models over the past few days. The period Sat-Mon has been watered down, with the cold shifted east Sun-Mon, but a second bite has been added Tue-Thu. Peak temps in the high single digits to low teens throughout, initially held back more by cloud and rain amounts, then by the sheer chilliness of the airmass in spite of increased sunshine. Wintry precipitation generally looks to be restricted to high ground unless something develops for one of the overnight periods Tue-Thu - a trough line in the flow perhaps.

Longer term, promising signs that heights will lower near/just south of Greenland, with the Azores High extending NE across the UK by day 9-10. Looking at the MJO, little guidance is offered, except that GEFS have been toying with a move into phase 8 which may be why numerous runs have been prolonging the theme of blocking to the W/NW - but not necessarily, given our proximity to May, for which the phase 8 composite is very different (below, April on the left, May right):

  

Indeed the May composite appears quite well represented in the GFS 00z operational.

The other models, however, are not keen on any MJO activity of note. 

 

- which leads me to conclude that the lowering of heights to the NW and ridging of the Azores High our way may be driven by other forcing variants.

Looking at the AAM as a possible driver - it may be hitting an El Nino-driven floor in the GEFS output (above-right), but it's a long way into the negative - too far perhaps, given the known bias. Not sure it's quite right for the AH ridging in - but I'll leave that to the best informed on the matter e.g. Tamara; I've been too busy with other aspects of meteorology to cement what I know about the AAM/torques and the GWO into my mind for reliable access!

 

[Fourty Point Three Degrees]

2 hours ago, Frosty. said:

WOW what a beautiful ending to the Gfs 00z op this morning with an early taste of summer developing through early May with 564 dam heading our way!.

Charts like this always get me in the mood for summertime, they do it everytime!!  But just watch it all erode away piece by piece, hour by hour until we're left with dull miserable & gloomy westerlies

[Frosty.]

3 minutes ago, 40*C said:

Charts like this always get me in the mood for summertime, they do it everytime!!  But just watch it all erode away piece by piece, hour by hour until we're left with dull miserable & gloomy westerlies

I'm quite optimistic about a considerable warm up after the upcoming unseasonably cold spell, especially after reading Singularity's post..hopefully may will spring an early taste of summer!