Model Output Discussion - 1st February Onwards 12z--->

[Vorticity0123]

A short post from me focussing on medium range (up to 10 days out). I will only focus on the models for now (so not at the influence of the MJO etc.). So basically this post can be seen as a general guide to what the setup will be on average.

 

Both the ECMWF and the GFS ensembles show that high pressure will return in about three days as the Azores high connects with another high pressure located over Scandinavia. For example, check the 72 hour surface level pressure charts from both models (12Z runs):

 

GFS: http://www.wetterzentrale.de/pics/Rtavn721.gif

 

ECMWF: http://www.wetterzentrale.de/pics/Recm721.gif

 

Thereafter, a north-south split seems to develop, with the north of the UK coming more under the influence of low pressure activity while the south remains somewhat drier (of course, details about the exact positioning can change, but the general theme seems to be significant low pressure activity to the north of us alongside with strong high pressure activity to the south). Once again, the GFS and ECMWF for 8 days out are given:

 

GFS:  http://www.wetterzentrale.de/pics/Rtavn1921.gif

 

ECMWF: http://www.wetterzentrale.de/pics/Recm1921.gif

 

Also, the 6-10 day 500 hPa anomalies tend to agree quite nicely with this forecast:

 

NOAA 6-10 day 500 hPa heights (green lines) and anomalies (broken lines) for 6 to 10 days out (made yesterday).

 

What can be seen is that there is a deep 500 hPa trough extending from the USA via the north of Iceland toward Siberia. Furthermore, the Azores high seems to be displaced somewhat to the northeast edging closer to the UK, but not as close seen as last week.

 

This creates quite a vigorous westerly flow over and to the north of Scotland. The precise positioning of the combination Icelandic trough - Azores high will determine how far south the low pressure activity will reach. If, for example, the Azores high tends to creep even somewhat more north than indicated here, it will be pretty calm over the whole UK. On the other hand, if low pressure activity can drop somewhat further south than seen here, the south will also experience some unsettled conditions.

 

A caveat to this may be that the GFS is showing the troughing to shift more toward Scandinavia near day 10, creating a cooler northwesterly flow over the UK:

 

http://www.wetterzentrale.de/pics/Rtavn2401.gif

 

The GFS has been showing this idea intermittently for some time now, so it would be worth keeping an eye on this to see whether this could become a trend.

 

Finally, for the ones interested, I've made a thread about long range forecasting, also explaining the GWO from the basics. It can be found here:

 

https://forum.netweather.tv/topic/82525-long-range-forecasting-and-teleconnections/

 

Hope to have as many contributions as possible .

 

Sources:

http://www.wetterzentrale.de/topkarten/fsecmeur.html\

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

Edited February 14, 2015 by Vorticity0123

[Winter Cold]

Well one post in 6 hours on the model thread in winter is a very sad state of affairs pretty much sums up whats happening.

 

GFS 12z is poor and goes zonal in FI. ECM 12z is a little better but only manages 24 hours of colder 850s near the end but you can see the high isnt pushed south enough and milder air is waiting to flood in again.

[johnholmes]

 

 

Those ideas seem fine to me V and I recommend folk, especially new to the idea of longer range forecasting, to read his link to this.

thanks for this and the other link.

[Eugene]

That is the quote that describes the entire winter this year :-D

 

 

No late Dec, late Jan to mid February was dry and cold.

[Mark Parsons]

Where is everyone? Obviously valentines day is having an impact....................

[bluearmy]

ecm ens continue to drop the heights ever further south pre day 10. (worth looking at the spreads to see where the systems are likely to track).  the gfs love in with blocking will be nothing but the imagination of the model and we will be left wondering where our ultra dry february went!

 

the zonality looking cold btw though that is unlikely to mean anything particularly wintry pre day 10 away from northern higher elevaiton. wouldnt like to pick what happens to the azores ridge post day 10. the extended eps not too consistent with this feature. the euro low anomolys also waxing and waning from run to run.

[Paul]

For those who are interested in teleconnections and their use in forecasting, Vorticity has started a really interesting thread here:

https://forum.netweather.tv/topic/82525-long-range-forecasting-and-teleconnections/

[Frosty.]

Tonight's Ecm 12z ensemble mean continues to show an increasing bias towards periods of colder westerly to northwesterly winds just beyond a week from now with at least -5 T850 hPa sweeping SE across the UK which means we would have colder and showery conditions between bouts of milder, wet and windy weather. This would mean a return to the pattern we have had for most of this winter BUT not yet because for the next week or so, high pressure will bring a lot of fine weather to the south of the UK in particular whereas NW Britain will be predominantly unsettled and windier with rain and showers..but the signs are there for colder Polar Maritime shots during the further outlook with snow showers and night frosts at times.

[snowblizzard]

Outlook remains dire!

The series of mild/wet & windy or benign February's for UK continues!

We always seem to be in the right place at the wrong time!

[Chief Wiggam]

If the posting rate is related to the chances of cold then this model is forecasting mild, mild, mild.....

[Daniel*]

Wintry interest on GFS 18z in the reliable nothing earth shuddering.

850s:

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=54&mode=1

http://www.meteociel.fr/modeles/gfse_cartes.php?ech=60&code=0&mode=1

Precip:

http://www.meteociel.fr/modeles/gfse_cartes.php?ech=54&code=0&mode=2

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=60&mode=2

Freezing level:

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=54&mode=3

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=60&mode=3

[bluearmy]

Has to be said that even the GEM has worked out the post day 7 solution better than the GFS. Finally, it stumbles across the less blocked outcome. Really not sure that the resolution increase has done much good.

[Eugene]

Yeah GFS has been hopeless lately, turning increasingly unsettled from thursday now across almost all model output, GFS's springlike weather for next weekend has now gone with cooler unsettled westerlies, glad to see that high just to our south be pushed southwards allowing cooler PM airmasses to dominate.

[Frosty.]

Ecm 00z looks cold and stormy in little over a weeks time, especially across scotland with one of those weather bombs (explosive cyclogenesis) similar to a few occasions earlier in the winter, we would all see a change to colder and more generally unsettled weather later in the week and more especially next weekend with increasingly wintry showers and gales or severe westerly / northwesterly gales and some of us would see snow, particularly on hills and further north. This run shows the potential for further bouts of very unsettled weather beyond T+240 hours with marked temperature changes from one day to the next and further disruptive winds..The week ahead by comparison looks very benign in the south with high pressure for most of the week but for n.Ireland & Scotland it looks like Atlantic weather with rain and showers with strong winds at times.

Edited February 15, 2015 by Frosty.

[IDO]

Has to be said that even the GEM has worked out the post day 7 solution better than the GFS. Finally, it stumbles across the less blocked outcome. Really not sure that the resolution increase has done much good.

 

 

Agree. I said in November/December it kept blowing up pressure cells and suspected it may throw up some ECM D10 teasers, but it is worse than that, it has now defaulted in FI from the Atlantic bias to the Azores bias. Just as we got use to its foibles we now face a new puzzle. I suppose that it was obvious, they have increased the resolution but have not upgraded the software, so any poor algorithms may only increase the errors? 

 

It's mean had been sinking the high slowly for a while so last night's GEM was no surprise. Though one thing remains clear it was always either a washout zonal fest or a dry settled anticyclonic pattern. The high was always my preference as even with PM interludes, for most it will remain cold rain, and after last year that does not float my boat.

 

So now we are faced with about three days of settled weather from Tuesday and then a week at least of the Atlantic train. The D12 mean:

 

 

Average temps in the south but feeling cool in the cloud and rain. Looking at the GEFS clusters at D14, no sign of HLB'ing as yet. 30% N/S split, 20% zonal, 25% UK HP and 25% jet NW to SE through UK. In other words anything but blocked.

 

Neither ECM or GEM at D10 offer any hint at long term cold though variations on the zonal theme are present:

 

 

[Gibby]

HERE IS MY LATEST ANALYSIS USING DATA SUPPLIED BY THE NWP OUTPUT COVERING 5 OF THE WORLDS MOST POWERFUL WEATHER COMPUTERS.

THE CURRENT GENERAL SITUATION A slack pressure gradient lies across the UK today. Pressure will fall in an increasing Southerly flow tonight ahead of a cold front moving slowly across the UK from the West tomorrow

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

MODELS-2 WEEK HEADLINE Changeable weather seems likely especially in the second week when strong winds and rain may develop for all areas at times. Near average temperatures.

THE GFS JET STREAM ENSEMBLE FORECAST The Jet Stream Ensemble Forecast shows the split flow with a strong arm North of the UK and a weaker split running South over the West of the UK tomorrow will shift East as a strengthening surge in the Northern arm crosses East to the North. The flow then splits again later in the week before a general shift somewhat further South of the flow than has been shown of late is likely later as it is shown crossing Southern Britain and Northern France through Week 2.

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

GFS OPERATIONAL The GFS operational today has shifted much more towards a more cyclonic and mobile nature when compared to yesterday with the occasional weakening troughs crossing East this week superseded by much windier and unsettled conditions in strong Westerly winds with the Atlantic High lying much further to the South and being much less influential. Some occasional spells of cold polar maritime winds from the NW are shown to at times dragging wintry showers through at times to higher ground generally and lower ground too at times later in the far North. A similar theme is shown at the close of the run moving forward.

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

http://www.wetterzentrale.de/pics/Rtavn3841.gif
 
THE GFS CONTROL The GFS control run shows a watered down version of the operational holding High pressure somewhat closer to the South at times which makes any polar maritime air incursions much less pronounced that the operational and as a result the wetter spells less pronounced too in the South.

THE GFS CLUSTERS The GFS Clusters today show a 40% cluster that support an Icelandic Low and Azores High in two weeks while the remainder show variations of this pattern ranging from a displaced Azores High to the SW and a chilly NW flow across the UK or an even more displaced High North over the Atlantic with a Northerly across the UK.

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 UKMO this morning shows a strengthening Southwest then West flow through the week with a cloudier and milder interlude with rain in the NW gradually extending to all areas later in the week as pressure falls generally

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

THE FAX CHARTS The Fax Charts this morning show weak fronts crossing slowly East tomorrow followed by a ridge of High pressure over the South and a mild fetch of SW winds developing over the NW by midweek. This extends to all ahead of further cold fronts approaching from the Atlantic at the end of the week.

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

GEM GEM shows High pressure close to the South following a cold front slowly East tomorrow. A mild SW flow will affect the North midweek with the South quieter under High pressure. Then another front crossing all areas from the West later in the week is the introduction to much more unsettled and windy conditions for all as Low pressure develops close to the North with strong winds at times from the West and spells of rain mixed with colder periods with wintry showers in a week or so.

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

NAVGEM NAVGEM shows a couple of weakening fronts moving slowly across the UK tomorrow and again later in the week. In between a mild SW flow affects the North with some rain and mild conditions in the sheltered East while the South stays dry and bright. Then by next weekend this model too shows a slow progression into much more unsettled territory for all as pressure falls and strong West winds affect all areas with rain at times.

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

ECM ECM is much the same as NAVGEM through the week with the same dip into windy and unsettled weather next weekend as Low pressure drops SE across the North sea with a spell of rain followed by cold and showery conditions following. then as we move through next week the mobile weather pattern persists with fronts crossing East periodically in the strong West breeze with rain at times for all, but as always with High pressure to the South heaviest in the North.

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

ECM 10 DAY MEAN The 10 Day Mean this morning shows the likelihood that the UK will lie under a Westerly flow in Week 2 between High pressure near the Azores and Low pressure to the North of the UK with the Jet flow close to the South of the UK.

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

NOTABLE TREND CHANGES FROM PREVIOUS RUNS The long term trend has moved back today towards more unsettled conditions developing for all in the second half of the output that would involve some incursions of somewhat colder air at times in a NW wind.

31 DAY HISTORICAL VERIFICATION STATS FOR GFS, UKM & ECM The current verification statistics for the past 31 days shows ECM leading the way at 3 days with 97.4 pts followed by UKM at 96.9 pts and GFS at 96.1. At 5 days ECM just about leads the field at 89.7 pts over UKMO at 88.9 pts and GFS at 86.8. At 8 days ECM remains the leader with 62.9 pts over GFS's 62.0 pts. Then at Day 10 ECM retains superiority at 47.8 pts over GFS at 42.4.

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.prig
 

MY THOUGHTS The pattern this morning remains one of Atlantic High pressure domination in the short term though that won't exclude a cold frontal trough moving slowly east tomorrow delivering rain for all at some point. Then High pressure builds back across the South towards midweek while the North sees a short spell of mild but strong and moist SW winds with heavy rain over hills. Later in the week another weakening front looks like moving over all areas with another band of relatively light rain but this time introducing a much more buoyant phase of weather as the pressure across the UK falls and Low pressure moves in closer to the North and pushes more significant troughs and accompanying bands of rain followed by showers to all areas. Thereafter most output shows unsettled westerly winds predominating for the rest of the period with the usual cocktail of bands of rain alternating with colder and brighter interludes with showers, wintry at times on hills and in the North. There remains little sign of anything particularly cold or unusual  within any weather parameter over the next few weeks but it does look like the month will end rather wetter than it started for many with temperatures overall not far from average given the time of year.  

Issued at 08:30 Sunday February 15th 2015

[mushymanrob]

i must be looking at different charts to some, whilst wednesday and thursday look mild, theres not much 'mild' aside from then. its looking average, with normal late february weather on offer in a changeable, mobile, conditions. suits me!

just because theres no cold spell on offer doesnt make it 'mild'.

[knocker]

A quick run through of the ecm ops to T240 just shows the surface temp anomaly alternating around the average.

[Iceaxecrampon]

Winter Over?

 

 

Maybe not for the Pennines - Mid Wales and Alba?

 

Albeit a week away.

 

Ian

[polar vortex]

The UKMO t144 chart is loaded with potential this morning. Certainly the pick of the bunch from 

a coldies perspective but with it being the t144 chart maybe should not put to much faith in it just yet.

 

[bluearmy]

Worth noting that once the pattern flattens out, upstream is frigid and a strong WNW flow is going to provide wintry interest ( more so at elevation of course but not exclusively)

[polar vortex]

Worth noting that once the pattern flattens out, upstream is frigid and a strong WNW flow is going to provide wintry interest ( more so at elevation of course but not exclusively)

The UKMO model this morning suggests that it may not flatten out.The t144 chart screams north Atlantic ridging 

and a much more meridonal pattern. Something to watch perhaps.

[knocker]

Worth noting that once the pattern flattens out, upstream is frigid and a strong WNW flow is going to provide wintry interest ( more so at elevation of course but not exclusively)

 

Yes that's very true and not much point in selecting individual charts in this fluid situation but perhaps just a note of the strong jet in the latest GFS run.

Chart courtesy weatherbell

[IDO]

The UKMO model this morning suggests that it may not flatten out.The t144 chart screams north Atlantic ridging 

and a much more meridional pattern. Something to watch perhaps.

 

I do not see any chance of Atlantic ridging on that chart TBH. With the direction of travel of the PV circulating to the north of the UK the pattern in our sector is as flat as it could be. Looking at the GEM and GEFS mean at D7 and they show a flat zonal pattern:

 

 

 

Not one member of either suite builds a ridge in the Atlantic. The UKMO chart is similar to many of the ensemble members with a surface high ejecting out of the US, but with no WAA it will just get pushed east under the jet.

 

Looking at the GFS 06z op and it is zonal from around D5 to D16 with the PV showing no current signs of easing off:

 

 

From week 2 the westerly flow is consistently cold (850s) for the north, though at this range we will have to wait to see if they get modified.

[polar vortex]

I think there is enough evidence in the model output post t120 to suggest a more amplified pattern 

in the Atlantic. Could be quite a potent affair should this happen. Role on the 12z