Model output discussion - 20th Feb onwards

[Polar Maritime]

And back to the Models please folks, Thanks.

[knocker]

The models are still looking to push some spasmodic rain up from the south west around mid week, courtesy of the Iberian low, with perhaps some thundery outbreaks but there is still considerable uncertainty about this.

Edited April 16, 2016 by knocker

[Timmytour]

10 hours ago, knocker said:

Some people keep saying next weekend and after is a long way off but the anomalies have been pretty consistent vis the upper air pattern for a couple of fays now. The EPS this evening 8-13 day mean has the deep trough due east and the northerlies for the period giving a negative 850mb temp anomaly in the 5-6C range. It may not pan out quite this way of course but I wouldn't bet the house on there not being a cold spell around this time. But I would be more than happy to be wrong.

As someone who's looking forward to a few days off at the end of April I hope you are wrong Knocker and this, like so many other glimpses of a great "winter-looking- chart in F this year goes the way of the pear.   But to me you've been singing from an accurately typed hymn sheet all year with the anomaly charts which to my mind have proved an immensely more accurate way of gauging what the weather will turn out to be in this sort of time-frame than the exciting looking narnia type FI  output we've occasionally seen from all the odels which have never verified.

This puts me in mind of the year I got married (if only I could turn back the clock and use that year more wisely!) it was in 1997 in late April and by the time the early May bank holiday came along we were walking in snow on the hills around Lake Garda on honeymoon and hearing of snow falling back home in the UK
 

  

[Polar Maritime]

GFS take on next weekend.. Another cold Northerly flow in the pipeline with -10 uppers and snow showers pushing South into week 2.

 

Edited April 16, 2016 by Polar Maritime

[Summer Sun]

ECM doesn't take the high quite as far west on this mornings run compared to last nights 12z for next weekend

12z yesterday

00z this morning

Still some colder air but the position of the high is far from nailed on yet

 

[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 SATURDAY APR 16TH 2016

THE CURRENT GENERAL SITUATION  A cold Northerly airstream has become established over the UK overnight and will continue today. Pressure will rise though and a strengthening ridge of High pressure will extend over Southern Britain tomorrow and extend it's influence further North too early next week.

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

CURRENT SNOW FORECAST AND FREEZING LEVEL OVER THE UK The upper air temperatures are very low for April over the whole of the UK this morning at almost 1500ft in places allowing snow to fall over modest elevations across England and Wales this morning with some covering in places. This will be short-lived and after today uppers will rise to around 4000ft by Monday and higher by Tuesday.

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

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

MODELS-2 WEEK HEADLINE  Slowly becoming drier and brighter from the weekend but with the risk of cool nights and some frost for a time next week. Perhaps more showers again later especially across the South and East.

THE GFS JET STREAM FORECAST  The Jet Stream pattern is now a split flow with one portion well South over Spain and North Africa in association with Low pressure down there. Another finger is moving West to East near Northern Scotland though this flow remains quite weak. The flow to the South feeds North by midweek and sets up another period of cool North winds as pressure remains quite high at Northern latitudes encouraging the flow to remain well South of normal.

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

GFS OPERATIONAL The GFS Operational Run today shows a lot of cool and unsettled weather across the UK as the Jet stream remains unco-operative in supplying sustained warmer weather. The current chill Northerly will be replaced by somewhat warmer conditions for a time early in the week as pressure builds strongly across the UK. this is then eroded by low pressure moving up from the SW midweek with some potentially thundery rain here while the North stay or become largely dry and bright. Then from the end of next week on we're back to where we are this weekend with a cold North or NE flow developing. This time though it looks longer lasting than this weekend with Low pressure lying close by with a cold NE feed from Scandinavia so showers and some longer spells of rain and hill snow are still possible despite approaching May. However, High pressure is shown to win back ground to lie across the UK at the end with a warmer SE feed. 

GFS CONTROL RUN The GFS Control Run although similar in sequence High pressure remains closer to the UK through the end of next week firstly restricting the extent of any spread of unsettled weather from the South and also restricting the influence of the cold and showery North feed thereafter that the Operational run above shows. Nevertheless, there will be a lot of North in the wind with High pressure stuck over the Atlantic so temperatures would still be normal or somewhat below for the most parts with the continuing risk of night frosts where skies clear.

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 still show a 75/25 split in preference of High pressure lying close to the NW of the UK in two weeks time with a  chill NE flow likely to be blowing across the UK. The remaining 25% show High pressure over or to the South of the UK in an anticyclonic or Westerly feed.

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 High pressure extending it's influence from across the South to the North through next week as Low pressure begins to move up from the South or SW towards the middle of next week. Temperatures will be on the rise again though with some thundery rain possible at times across the South from midweek.

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

THE FAX CHARTS The Fax Charts show troughs clearing South with cold Northerly winds briefly before a ridge builds across the South and then extends North early next week. Low pressure over Spain and Iberia is then shown to move North towards the South towards midweek with a warmer ESE flow ahead of it.

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

GEM GEM this morning follows the same suit as the rest with High pressure early this week slowly being pushed North or NW as Low pressure to the South edges up towards Southern Britain strengthening an Easterly flow which eventually turns to a chillier North or NE'ly as High pressure establishes to the west and NW. Northern and Western parts would likely stay dry with night frosts while the South, East and particularly on this run the SE stay cold and breezy with showers or rain at times.

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

NAVGEM NAVGEM also shows the same build of pressure in the coming days, firstly across the UK before it gets sucked away NW to Greenland by the end of the run opening the door to cold NE winds and heavy showers to sweep South to all parts by next weekend, this following a period when Southern England could have some thundery rain from a Southern European trough moving North midweek.

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

ECM ECM today still shows the same theme as it and i't ensemble dats have shown for days in that the current cold day today will be replaced by a period of benign and settled weather lasting several days with temperatures recovering for many. However, Low pressure is shown to try and push North towards Southern Britain midweek with the risk of some showery rain. While this is happening High pressure over the North at the end of next week is sucked away to the NW near Greenland with a cold and showery NE flow developing across the UK although the NW lying close to the ridge from the Greenland High might stay dry. Frosts at night look very likely under any clear skies late in the period

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

ECM 10 DAY MEAN (12z) The 240hr mean Chart from last night continues the theme of High pressure likely over the Atlantic in 10 days time with Low pressure to the East or SE meaning a cool Northerly or NE'ly flow likely over the UK with some showers by day and frost by night

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

NOTABLE TRENDS & CHANGES FROM PREVIOUS RUNS Still too much emphasis on the trend for cool and showery North or NE winds to be blowing down across the UK in 10-14 days time for my liking. However, that is the main trend this morning.

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 99.3 pts.  At 3 days ECM is leading with 97.4 pts to UKMO's 96.8 pts while GFS lags behind at 95.6 pts. At 5 days ECM leads with 89.6 pts to UKMO at 87.5 pts and GFS at 84.2 pts. Then at 8 Days ECM has the leading spot from GFS with 65.1 pts to 60.2 pts. Finally at Day 10 ECM has the lead from GFS with a score of 42.6 pts to 39.2 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  It still looks far from ideal Springlike conditions for gardeners and growers this morning as they will despair at the amount of High pressure shown in the models this morning all in the wrong places to eradicate the risk of night frosts almost anywhere in the UK over the next 10-14 days. A notable frost is expected for all tonight as today's cold Northerly is replaced by a strong ridge of High pressure. This then gently feeds North in the following days to allow some warmer air to develop in the sunshine with the first few days of next week looking very respectable. However, we have not lost the Low pressure down to the South and towards midweek troughs from that edge up towards the South with potentially thundery rain likely for a time. This then looks like being pulled away to the East as not unlike this weekend a surge of colder air is pulled down from the NE as pressure retreats towards the NW Atlantic and Greenland. These NE winds would likely bring a mix of bright sunshine but some big and very cold April showers with soft hail, thunder and sleet all in the mix I would suspect and no doubt somewhere could see snow. As a result of this flow nights would be clear and cold inland with frosts likely but in compensation in the sun between the showers it should feel OK. The NW would probably see the best weather overall but having said all of the above the overall weather pattern is not concerning in the amounts of wind and rain totals but as I live in an area of avid gardeners and growers they will be disappointed that I am still talking frosts and cold showers at this stage in Spring rather than dry and warm ideal Spring conditions. However, I can only say what I see and lets hope that the models turn around in a days or so to take us out of this Northern blocking situation that has eluded us all Winter which not unsurprisingly has decided to turn up in Spring this year.     

Next Update Sunday April 17th 2016 from 09:00

Edited April 16, 2016 by Gibby

[knocker]

The EPS 7-12 anomaly this morning has HP ridging through the Denmark Strait into Greenland with the centre of the upper low Denmark. Not good as this indicates a cold northerly from around the 23rd until around the 28th. 850mb negative temp anomalies in the 5-7C range.

[Singularity]

    

First up we have the 2m temp anomaly for days 1-5, which shows that the impacts of the cold northerly are focused most on the UK, with rapid mitigation over continental Europe followed by a warm -up that cancels out the negative anomalies. Obviously today is responsible for a large part of the cold anomaly even here (see below  for anomalies for 6pm today and 6am tomorrow).

There's then a warmer period midweek, but too faint and short-lived to be reflected as positive 2m temp anomalies. By the weekend we are on a big downward slide, with GFS taking it to the extreme, as the right-hand of the above images shows. That it brings all-day snow to southern England throughout Monday 25th, with some settling, is just bonkers.

 

 

[049balt]

GFS 850, not that bad for the West.

[Summer Sun]

GFS now has the high not as far west next weekend as I said last night the position of the high is far from nailed on yet

24 hrs ago

GEM like yesterday also has the high close by next weekend

Still some chilly air on the models but not as cold as some other runs showed

[knocker]

Not unexpectantly little change with GEFS 7-12 anomaly with HP ridging Denmark Strait and centre of the trough northern Germany. Ergo northerlies still very much on the cards with a cool few days. Details obviously to be finalised some days hence.

[knocker]

Still looking dry for most of the week with the exception of Weds/Thurs when rain, perhaps thundery, pushes up from the SW. It probably will not track very far NE. Temps gradually warming up from this weekend, that is until the northerly kicks in around the latter part of next weekend when it well turn markedly chilly.

[SMU]

Not often you see a -16 degree anomaly over the UK 

ECM has the -8c isotherm into london at 192 - for the last week of april thats ultra rare !

[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 SATURDAY APR 16TH 2016

THE CURRENT GENERAL SITUATION  A ridge of High pressure is building across Southern Britain today. Weak troughs of Low pressure will move East over the far North later today and more slowly SE across other areas tonight and tomorrow weakening further as they run into High pressure over Southern England by then.

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

CURRENT SNOW FORECAST AND FREEZING LEVEL OVER THE UK The frezing level across the UK currently is around 2000ft but it will rise to around 3500ft for many by tomorrow and much higher across the South around midweek, perhaps to as high as 10000ft by midweek as warmer air moves up from the South. As a result snowfall will be impossible on lowland Britain later this week.

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

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

MODELS-2 WEEK HEADLINE  A lot of dry and bright weather this week with cool nights then even chillier weather with sunshine and showers look likely with a continuing night frost risk thereafter.

THE GFS JET STREAM FORECAST  The split flow in the Jet Stream will remain with the main arm well South over the area of Southern Spain and North Africa with low pressure West of Portugal. The northern arm while weak moves East near Northern Scotland and this buckles at times later this week as the Southern arm also sends a spore North to the UK before the flow simplifies to a single flow blowing North to South over the UK and sets up a cyclonic airstream near the UK at the end of the period.  

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

GFS OPERATIONAL The GFS Operational Run today shows a lot of High pressure influenced weather across the UK although the positioning of this is poor for the UK. Through the working week High pressure well establishes across the UK with fine weather developing for all but with cool nights and some frost the days will be bright and sunny. Later in the week a SE flow across the far South and SW could give rise to some potentially thundery rain before winds back NE for all and temperatures decline once more next weekend with the second week looking very cool and showery with some wintry showers over hills and frost at night even more likely under winds from such a cold source to the North. The best weather then looks to be towards the NW before all areas look like warming up a little at the very end of the period as winds finally return to a milder Westerly source.. 

GFS CONTROL RUN Apart from minor details the Control Run offers only small differences and that occurring in the much more unreliable part of the run in the second week. As it is things get much more complex in Week 2 as Low pressure is shown to elongate the UK with cold air to the North and warmer air pushing up into the South. This means rain at times for many but possibly becoming warmer and more Spring feeling in the South with time.

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 are all over the place again with no clear pattern determined by this morning's set. As they stand there is around equal support for some sort of cold Northerly flow over the UK with low pressure to the East and High to the West whereas there is another equally big group who support the opposite of High pressure to the East and Low pressure over or just to the West of the UK with South or SW winds and undoubtedly less cool conditions as a result. Not a lot can be drawn from this pack this morning.

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 High pressure well in control over much of this working week although some sort of hiatus could develop across the extreme South midweek as Low pressure to the South brings the risk of some showery rain here for a time. then as we look towards next weekend UKM looks to be setting itself up for the UK to have another very cool weekend of sunshine and showers with frosts at night under a strengthening NE or North flow.

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

THE FAX CHARTS The Fax Charts show High pressure developing across the South of Britain over the coming days and killing off a weak front moving down from the North by Tuesday. Then High pressure builds across all areas for a time before a pincer movement develops caused by troughs from both the North and South moving towards one another by the end of the week.

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

GEM GEM this morning is a little slower in bringing the cold North or NE flow into the UK, leaving it until after next weekend before the main thrust of rain and cold showers feeds down over us close to Low pressure near the SE to end the run. This leaves much of the coming week dry and bright with High pressure over or eventually just to the West and NW with a ridge close by though this model too runs a risk of showery rain over the extreme South soon after midweek as things warm up for a time.

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

NAVGEM NAVGEM too shows good support for a High pressure based week to come with fine days with some sunshine mixed with chilly nights with frost in places. Some exceptions to this theme also look possible with the same risk of showery rain in the far South soon after midweek this coupled with falling pressure later culminates in High pressure being sucked back out into the Atlantic late in the week and next weekend at the expense of a cold Northerly flow establishing with showers and cold winds to end the period.

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

ECM ECM today still maintains the theme it has for days now of a High pressure based week to come as it builds across Southern Britain over the next 24 hours or so before extending North to all areas by midweek. A freshening Easterly will then develop across the South and with fronts over the channel some showery rain could develop here soon after midweek. Then as for some considerable while now the model has all eyes looking to the North and NE as showery Low pressure pulls down a cold Northerly airflow as result of High pressure being sucked out over the Atlantic and Greenland to end the period. This could spell quite a protracted period of cool and perhaps very unsettled weather for much of the UK given such extensive High pressure blocking to the North and NW is shown at Day 10.

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

ECM 10 DAY MEAN (12z) The 240hr mean Chart from last night endorses the Operational Run issued this morning well with a cold Northerly flow with sunshine and showers a strong theme offered to the UK this morning for 10 days time.

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

NOTABLE TRENDS & CHANGES FROM PREVIOUS RUNS Still too much emphasis on the trend for cool and showery North or NE winds to be blowing down across the UK in 10-14 days time for my liking. However, that again is the main theme this morning.

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 99.3 pts.  At 3 days ECM is leading with 97.4 pts to UKMO's 96.8 pts while GFS lags behind at 95.6 pts. At 5 days ECM leads with 89.7 pts to UKMO at 87.5 pts and GFS at 84.0 pts. Then at 8 Days ECM has the leading spot from GFS with 65.6 pts to 59.8 pts. Finally at Day 10 ECM has the lead from GFS with a score of 44.0 pts to 39.4 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  Another day and no change in the models theme this morning and with a lot of cross model support the theme of weather I'm about to describe for the next few weeks comes with a higher degree of certainty than is often the case. What we currently have is pressure rising across the UK as a strong ridge develops over Southern England in the coming day or so. For a time a weak Westerly flow will permit weak troughs to bring cloud and a little rain across the UK and this may approach the South too tomorrow before the front responsible dies in situ as the High pressure develops and extends North. This then leads to much of the UK having a largely dry and settled three or four days with some chilly night but bright and warm sunshine by day. Low pressure will be flirting with Southern England from midweek and this could lead to some showery rain extending North from France on Thursday under a previously strengthening ESE flow while in the North it stays dry and fine until the weekend. Thereafter things get much more complicated although the message from all the models is an assured one. High pressure will be retrogressing to the West and NW at the weekend and coupled with Low pressure to the SE and later East and NE cold north winds are expected to flood back down across the UK next weekend and then last for some considerable time. Although day to day details between the models are shown I can generalise by saying that this period looks like being rather cold and showery and the air still looks cold enough for some snow in the showers over the hills with hail, graupel and thunder possible almost anywhere between spells of sparkling sunshine and good visiblities. More importantly for gardeners and growers frost by night look inevitable on occasions as showers and clouds decay away each evening. Then if I have to look at the crystal ball for the days between Day 10-14 I think we can say that winds may back Westerly with time allowing somewhat less cold though still changeable conditions to develop as we move into May proper. So there you have it a lot of dry and fine weather over the week to come looks like being superseded by another cold attack from the North or NE next weekend with the lead up to the Bank Holiday Weekend at the turn of the month looking a cool and showery one although as always in showery setups some fair better than others and overall with no persistent rain or gales looking likely away from the cold showers and night frosts things overall may not feel too bad.     

Next Update Monday April 18th 2016 from 09:00

[Cloud 10]

51 minutes ago, Steve Murr said:

Not often you see a -16 degree anomaly over the UK 

ECM has the -8c isotherm into london at 192 - for the last week of april thats ultra rare !

 

Your avatar is quite apt when viewing the latter stages of the overnight ECM.

 

GWO looks pretty likely now to take a plunge into phase 1/2 (la nina anyone?) so could be quite a protracted spell of northern blocking coming up.

 

 

 

[Polar Maritime]

Probably colder than of any chart seen over Winter just gone! A long way off re detail, But certainly a cool if not cold outlook from the N/NE as we head into the final week of April. 

Edited April 17, 2016 by Polar Maritime

[Summer Sun]

At t144 UKMO has quiet a cold north to north easterly flow brigning some showers these wintry over high ground

ECM has the high a bit more over us but still some cold air for the time of year

GFS has the colder air moving down through the day with temps ranging from 5c to 12c and towards the mid teens possibly for some parts of Ireland

If this was mid winter a set up like the above would sent this place into meltdown as its mid April it won't

Edited April 17, 2016 by Summer Sun

[BLAST FROM THE PAST]

23 hours ago, knocker said:

The EPS 7-12 anomaly this morning has HP ridging through the Denmark Strait into Greenland with the centre of the upper low Denmark. Not good as this indicates a cold northerly from around the 23rd until around the 28th. 850mb negative temp anomalies in the 5-7C range.

I agree with Knocker's summation and GFS from a couple of days ago moved into ECM outlook.  ECM seems pretty solid on this......I'm still with it.  A very chilly end to April looking on the cards.  Synoptic pattern 3 months too late one thinks

 

BFTP

[bluearmy]

Been away but was still watching

this cold weekend and the next one have been well trailed by the extended ens. Some astonishing NH blocked charts on offer in a weeks time. could be the year without a spring at this rate. let's hope it's straight into summer and not the European monsoon! 

[karyo]

3 hours ago, Steve Murr said:

Not often you see a -16 degree anomaly over the UK 

ECM has the -8c isotherm into london at 192 - for the last week of april thats ultra rare !

Absolutely fascinating stuff! I would imagine this set-up will give some cracking thundery wintry/snow showers.

I had a few of those yesterday just north of Manchester yesterday with upper values around -5c.

Karyo

[bobbydog]

as Ian Brown would say...

WTF???

[SMU]

Yes a very convective flow-

The -9c line now progged into the midlands 

I wonder if we could hit the magical -10 line - that would be truly remarkable

 

added to the mix is the prospect of the April CET coming in around 7c leaving the May CET target if about 8.5c for a even more remarkable spring colder than winter statistic!

S

Edited April 17, 2016 by Steve Murr

[knocker]

As I and others have mentioned the anomalies have been signalling this cold snap for a while now and there continues to be good agreement between NOAA, and the 7-12 GEFS and EPS.regarding the upper air pattern. Assuming no major developments it looks at the moment a case of sorting the surface detail which naturally is going to vary with every ops run until nearer the time. Will we get perturbations within the northerly flow I ask myself?

Can't post the EPS 7-12 but it's very similar to the GEFs and gives a negative 850mb temp anomaly in the 7C range.

Edited April 17, 2016 by knocker

[Tamara]

4 hours ago, Cloud 10 said:

 

Your avatar is quite apt when viewing the latter stages of the overnight ECM.

 

GWO looks pretty likely now to take a plunge into phase 1/2 (la nina anyone?) so could be quite a protracted spell of northern blocking coming up.

 

 

 

Yes indeed - although there has been plenty going on outside the forum and well away from this thread, have been keeping something of an anticipatory eye on the usually progressive GEFS suite likely exhibiting its low Atmospheric Angular Momentum bias in the prevailing circumstances

However progressive it may be though -  in terms of where we are at, and more importantly where we are increasingly heading through 2016, it does have a lot of eventual relevance.

Whether that is sooner or later though, cannot yet be determined.

Several factors are in play, and the previous post a month back dealt in detail with the likely progression and evolution of them to the mid part of Spring

This has been progressing well enough in line with expectations, and although Spring has been slow to get started much as widely expected, up to now at least, the attempted cold shots (too late in truth in to provide proper widespread winter excitement) have actually been, in relative terms, less than might have otherwise expected - that is, if the atmospheric state had not been rooted in a higher AAM programme as it has till now.

So, at the mid-stage of Spring, a fresh appraisal of the determining factors is attempted in the purpose of maintaining further continuity through the upcoming period and into the last third of Spring. It is how these factors progress and interact that will determine the weather patterns through the rest of the season and into the first part of Summer

1) The continuing decline of the very strong Nino state, that has been influential since early Summer last year, into neutral territory (and then chances increase through the second half of the year of an established Nina base state developing)

The process of decaying Nino continues apace, with negative sub surface temperature anomalies now appearing in the eastern and central Pacific. This tells us that easterly trade winds are propagating northwards from the tropics, scrubbing out westerly wind tendency across the Pacific, and consequently eroding the surface anomalies, from east to west in the ocean waters of the Pacific, through upwelling of the colder water at depth.    Lack of tropical forcing, and supressed convection rooted over the Indian Ocean for some time is encouraging this process and is further indicated by the falling torque tendency in recent weeks, and as a consequence, a relative decrease in the higher Global Atmospheric Angular Momentum (GLAAM) state levels, in the first part of this month.

Hence we have seen the Global Wind Oscillation spiralling from its weak default Nino phase 5,6,7,5 6,7 orbit triangles towards Phase 8/0 - as the GEFS chart that Cloud 10 posted illustrates.

Though heading decisively southwards, we are still, for the here and now at least, in official Nino territory. For the coming intra two week/month period, it is this that is important in terms of the floor of AAM and where the Global Wind Oscillation ultimately heads. Hence, while ultimately prophetic in the very long term, we best be highly cautious of taking those GEFS forecasts at face value in the much nearer term. 

Self limitation of falling AAM tendency is already evident by torque tendency now recovering somewhat through the first half of April, and that suggests a bottoming out of AAM tendency over the next 10 to 15 days. We should remember that timelines exist with these sub-season and intra seasonal phenomena and the current rise has lagged implications for the direction of travel of the atmospheric response up to 14- 21 days ahead.

 

The lack of MJO (tropical convection) influence hampers progress in this respect, but there are still possible implications for the weather patterns after the turn of the month and into May.

2)  A late, but intense, seasonal break-up of the polar vortex

The robust turn of Winter to Spring season Final Warming of the stratospheric polar vortex is fully advertised in NWP modelling with the recurring height anomalies to the NW.  As documented in the previous post in March, such blocking is augmented by falling tendency in GLAAM and supressed tropical convection - as consistent with Spring seasonal wavelength changes. It is no coincidence that the fruition of downwelling of these warm stratospheric anomalies after FW break-up are surfacing just at a time when the atmospheric state has become more conducive to seasonal northern blocking. Hence NWP modelling of a distinctly below average northerly period from next weekend to probably see out the remainder of the month

3) Transition from w/QBO to e/QBO.  Furthermore, in tandem with the other evolutionary changes happening, we are seeing the emergence of easterly QBO anomalies start to assist the downwelling of the warm stratospheric polar easterlies to the troposphere. Clearly in conjunction with a relatively lower AAM tendency phase, this will hasten and likely help sustain the upcoming below average phase through the last ten days of the month into the very start of May.

Putting all this together, we await the turn of the month at the earliest for possible worthwhile changes. As stated, its too soon (just yet) for the atmosphere to embrace a proper Nina state - and we should see the supressed convection heading eastward

Added to the lagged effects of recovering frictional and mountain torques, an assist is available for a rebound in AAM by months end and re-assert, at least for a time, the weakening Nino ocean/atmosphere coupled state.  

The Global Wind Oscillation will of course provide the key. Attempts, in the short term at least, to breach meaningfully into Nina transitioned Phase 1, as the GEFS suite bullishly continues to insist, will be restricted and constrained by the still conflicting ocean base state. However, with a one way ENSO ticket in progress, easterly processes in the atmosphere are set to increasingly force their hand and we are increasingly at risk of seeing more and more transitory Nina like incursions to atmospheric responses, and knock on effects to hemisphere weather patterns, as the transition continues.

So, from end of this week, a cold showery regime set to be established with the GWO likely snagged around Phase 0 and the Spring vortex break-up in full sway.  Beyond that, its a case of looking for signs of improvement with the GWO hopefully back to weak orbit 5,6,7 and, equally hopefully, a relaxation of the blocking to the NW towards the UK. At least for a time.

The rest of the Spring looks set to be determined by how the atmospheric circulation/ocean SST state interacts as we get closer and closer to entering transitional neutral ENSO. This in turn will dictate how much (or otherwise) the legacy of the break up of the seasonal vortex and the emerging e/QBO are able to suppress the jet stream southwards, and augment (or otherwise) further northern block potential (as negative easterly anomalies continue to arrive into the troposphere) and associated Scandinavian/UK trough patterns through May

 

Edited April 17, 2016 by Tamara

[knocker]

No big surprise with the GEFS 6-11 anomaly tonight with the highly amplified pattern persisting giving a general northerly flow and temps significantly below average. As we move towards the end of the 16 day period the amplification slowly weakens and with the ridge/trogh retrogressing a tad the upper flow gradually backs to WNW but temps are still a little below average.

So in a nutshell from the end of the week the rest of April looks like being unsettled and on cool side.