Model Output Discussion - Spring 5th March Onwards 6z--->

[Frosty.]

The GEFS 12z mean supports a cold and unsettled first half of next week with wintry showers and night frosts but after midweek indicates drier and brighter conditions spreading from the southwest as the Azores high ridges northeast into the south of the uk cutting off the cold air supply with temperatures then starting to climb back towards average, conditions return to normal further on.

Edited April 22, 2015 by Frosty.

[Summer Sun]

UKMO very much on its own still with ECM backing the colder unsettled weather

 

[bluearmy]

ukmo very odd. has to revert back tomorrow. signs that the BH weekend could be reasonable.

[Winter Cold]

What you mean what's causing the high latitude blocking HP?

 

Im not clever enough yet knocker to understand all the background stuff, but Tamara summed it up lovely yesterday with a very good explanation.

 

I was just talking more in the way of the UK, after whats been a nice sunny few weeks, we can hopefully look forward to some big convective showers due to the cold upper air and strong sun etc and wondering whether we will see some snow/wintryness. Not sure when the last time we got a late April cold spell or a snow flake in May?

 

Anyway, ECM does back the GFS tonight and we are still on course for a northerly blast with some very cold air shown to pump down:

 

 

 

Then perhaps things returning more to normal as we head into May:

 

 

Certainly looks like a significant cool down for a while doesnt it, and with temps around 7c for a few days on tonights GEFS for S Yorkshire, you can imagine someone with my altitude seeing some wintryness hopefully as temps would be lower than that up here:

 

[Gael_Force]

Im not clever enough yet knocker to understand all the background stuff, but Tamara summed it up lovely yesterday with a very good explanation.

 

I was just talking more in the way of the UK, after whats been a nice sunny few weeks, we can hopefully look forward to some big convective showers due to the cold upper air and strong sun etc and wondering whether we will see some snow/wintryness. Not sure when the last time we got a late April cold spell or a snow flake in May?

 

Anyway, ECM does back the GFS tonight and we are still on course for a northerly blast with some very cold air shown to pump down:

 

Then perhaps things returning more to normal as we head into May:

 

Certainly looks like a significant cool down for a while doesnt it, and with temps around 7c for a few days on tonights GEFS for S Yorkshire, you can imagine someone with my altitude seeing some wintryness hopefully as temps would be lower than that up here:

 

gefs224.jpg

Not that long ago.....2010 saw a very chilly start to May.

 

http://www.meteociel.fr/modeles/archives/archives.php?day=1&month=5&hour=0&year=2010&map=0&mode=2

 

That's the month in sequence as it unfolded.

[Skullzrulerz]

Tonight's short summery of the main models.

 

ECM and GFS on the same team know as "Team Cold" want to bring a cool/cold northerly blast with snow for the north and somewhat for the south at times as well as unsettled weather on the cards but the details will be known soon.

 

UKMO is the last man/model standing if your a fan of warm/hot settled weather,let's see it takes the stand for partners in crime to join him or if he falls to the coldness is up for contest.

 

We find that out soon.

[ANYWEATHER]

Hiyer Folks.! A complete reversal of weather is about to happen, you can say major change , an enormous change , or even record breaking change. I will be not surprised that next week will see some spectacular weather , even Breaking news. I would not be surprised to see snow falling in Southern England given any very heavy precipitation. Im looking forward to the convective side of this major change! Some big clouds developing with hail, thunder and lightning, gusty winds , sleet, snow and heavy rain....Then again you will get sparkling sunshine and deep blue skies in between,!.....Perhaps some funnel clouds and small tornadoes......Its not out of the equation next week. If youre  a convection geek this is the week for you   PS ....The Kitchen Sink!!

[knocker]

The anomalies tonight are not showing any great enthusiasm to promote the Azores ridge.

 

The evolution next week up to day10 is a slackening of the high latitude block allowing a more zonal flow accompanied by the main UK orientated trough moving east but developing further troughs in the eastern Atlantic as LPs migrate west to east in the zonal flow. At least this will cut off the cold air over the UK (assuming this pans out) and introduce a more SW flow with temps around average.

Charts weatherbell

Edited April 22, 2015 by knocker

[knocker]

Well the GFS run this morning brings better news with the cold NW flow cut off at the pass ( could always change on the next run of course) and thereafter seems to follow the anomaly (see above) with depressions sweeping in from the west with periods of rain but temps near average and even above.

Chart weatherbell

Edited April 23, 2015 by knocker

[Polar Maritime]

Next Tuesday could to be an interesting day. Lot's to keep an eye on reg detail over the next 5/6 days.

 

Edited April 23, 2015 by Polar Maritime

[mushymanrob]

Hiyer Folks.! A complete reversal of weather is about to happen, you can say major change , an enormous change , or even record breaking change. I will be not surprised that next week will see some spectacular weather , even Breaking news. I would not be surprised to see snow falling in Southern England given any very heavy precipitation. Im looking forward to the convective side of this major change! Some big clouds developing with hail, thunder and lightning, gusty winds , sleet, snow and heavy rain....Then again you will get sparkling sunshine and deep blue skies in between,!.....Perhaps some funnel clouds and small tornadoes......Its not out of the equation next week. If youre  a convection geek this is the week for you   PS ....The Kitchen Sink!!

 

 

The anomalies tonight are not showing any great enthusiasm to promote the Azores ridge.

 

The evolution next week up to day10 is a slackening of the high latitude block allowing a more zonal flow accompanied by the main UK orientated trough moving east but developing further troughs in the eastern Atlantic as LPs migrate west to east in the zonal flow. At least this will cut off the cold air over the UK (assuming this pans out) and introduce a more SW flow with temps around average.

Charts weatherbell

 

yep, the anomalies have not supported a mid atlantic ridge off the azores high which is needed to give us the deep draw northerlies 'anyweather's post (above) refers to. whilst the ecm still suggests a shorter cold northerly, other models are backing away from that and the ukmo and gfs now look more like what the anomalies would allow.

so it will get colder and more unsettled, but not looking so likely now that there will be much wintiness (away from high ground in the north).

[Summer Sun]

UKMO has backed off for rising pressure on Monday it now has it edging up to the south during Tuesday and Wednesday

 

 

ECM gives us a couple of settled days later next week before low pressure moves back in just in time for the weekend

 

[Gibby]

HERE IS MY LATEST ANALYSIS USING DATA SUPPLIED BY THE NWP OUTPUT COVERING 5 OF THE WORLDS MOST POWERFUL WEATHER COMPUTERS ISSUED AT 08:00 ON THURSDAY APRIL 23RD 2015.

 

THE CURRENT GENERAL SITUATION High pressure will slowly decline across Britain today as a trough of Low pressure moves South towards Northern Scotland and another one approaches the SW of the UK from off the Atlantic.

 

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

 

MODELS-2 WEEK HEADLINE Becoming unsettled  and changeable with bright spells and showers, heavy and wintry on hills in the North for a time. Local night frosts still likely.

 

THE GFS JET STREAM ENSEMBLE FORECAST The Northern arm of the jet is expected to slip South towards and eventually across the UK amalgamating with the Southern arm moving up from the South. The flow then basically continues across the UK in one form or another for the remainder of the duration of the output today. 

 

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

 

GFS OPERATIONAL The GFS Operational this morning shows High pressure declining quite quickly now and being replaced by Low pressure moving up from the SW and eventually settling to the Northeast of the UK. Rain and showers look like becoming established with a cold Northerly interlude next week when wintry showers could occur over Northern hills for a time. Things then warm up somewhat as winds turn SW but the unsettled theme looks likely to continue with rain and showers at times but with pressure higher to the South some decent dry spells look likely later across the South and East with the most unsettled conditions returning towards the North and West.

 

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

 

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

 

THE GFS CONTROL The theme of the GFS Control run is very different beyond the first week with the colder period next week extended somewhat as High pressure gradually extends East across the UK at the end of next week with dry and fine conditions for a time before High pressure migrates to the North of the UK setting up a cool Easterly flow across the UK with some showers possible at times across the South.

 

THE GFS CLUSTERS The GFS clusters today show 50% of the pack hoing for a Low pressure based theme likely two weeks from now with Low pressure likely to lie over or to the NW of the UK with a lesser number of members contrastingly suggesting a ridge of High pressure lying across the UK from the West or SW.

 

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 shows Low pressure taking control of the weather over the coming weekend with a mix of sunshine and showers in average temperatures. early next week the model continues to restrict the surge of cold air reaching the South as much as recently shown with High pressure to the South backing winds towards a milder and less unstable Westerly in the South by midweek.

 

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

 

THE FAX CHARTS The Fax Charts follow the raw data early in the run but look to have been overwritten on last night's 120hr chart to accomodate a different evolution to cater for a shallow Low over Southern Britain early next week with cloud and rainy weather in cool conditions more likely with less influence of High pressure to the South.

 

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

 

GEM GEM this morning shows a changeable theme next week with rain and showers at times for all. After a cool push of North winds early in the week slightly less cool weather is shown at times thereafter but still unstabe air enough to ensure the continuation of rain and showers at times for most areas, heavy in places.

 

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

 

NAVGEM NAVGEM shows cool and unsettled weather early next week gradually lessening with time as this run too shows winds backing to a milder Westerly later next week with pressure rising slowly to give more in the way of dry if still a little cool weather by next weekend.

 

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

 

ECM ECM this morning shows the cold Northerly wind it has shown on previous output too but as with much of the other output it's duration looks shortened somewhat as like UKMO it builds pressure to the South backing winds more Westerly late in the week with a strong ridge crossing East. The end of the run sees Atlantic Low pressure crossing East into the UK with rain at times for all perhaps most likely across the South. 

 

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

 

ECM 10 DAY MEAN(12z) The ECM 10 Day Mean Chart  from last night shows fairly slack conditions across the UK with various options making up the mean biased towards slightly unsettled weather with Low pressure not far from the UK with some rain at times in average temperatures for all.

 

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

 

NOTABLE TREND CHANGES FROM PREVIOUS RUNS The trends this morning show a drift away from a prolonged cold spell in favour of more benign conditions later with a little rain at times for all and nearer average temperatures.

 

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 97.3 pts followed by UKM at 96.8 pts and GFS at 96.1. At 5 days ECM  continues to lead the field at 88.6 pts over UKMO at 88.4 pts and GFS at 86.0. At 8 days ECM remains the leader with 62.1 pts over GFS's 57.6 pts. Then at Day 10 ECM retains superiority at 46.0 pts over GFS at 41.7. 

 

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 Today sees the last day of the prolonged settled spell that many parts of England and Wales at least have enjoyed for quite some time. In replacement comes the re-introduction of Low pressure near the British Isles with a mix of sunshine and heavy showers over the weekend and temperatures returning to near average. Then as yesterday we have to look to the North to await cold Northerly winds to flood down over the UK early next week with very chilly air with further showers, wintry on hills. However, this phase looks shorter-lived than on previous output picked up first by UKMO a day or so back and now spreading across other output too. The most likely theme now reflects that after a day or two of cold North winds the airflow backs to a milder Westerly and as the possibility of High pressure building close to the South midweek the most changeable conditions return towards more Northern and Western areas with more in the way of dry weather and average temperatures to the South and East. It does look though that the weather over the UK from all models reflect a more changeable and unsettled theme than of late with the second week 2 offering some rain and showers for all at times with temperatures near to average and occasionally rather cool. It does reflect good growing conditions as the showers mix with occasional sunny spells but despite the shortening duration of the cold Northerly flow next week the risk of night frost remains if skies clear by night for some while yet and that from some output includes Week 2 as well. 

 

Next update from 08:00 Friday April 24th 2015

[Milhouse]

As some say, its all about spotting trends on the GFS and the trend appearing at the moment is height rises over Europe going into May. Highlighted very well on the latest GEFS mean.

 

[Summer Sun]

Pressure is slightly higher in the south at t144 this should give a fairly dry day here though if the sun breaks through it could trigger off some heavy showers

 

 

Low pressure quickly sweeps back in

 

 

Then towards the start of May high pressure gradually builds over the UK so settling things down again during the bank holiday weekend though temperatures would be around average at best given the air under the high would still chilly

 

 

The air will be cold enough for some snow over the high ground especially in Scotland where some accumulations are possible

 

 

Anything that falls on the higher ground in England isn't likely to amount to much more than a temporary dusting

[Captain Shortwave]

One more day of warmth tomorrow, especially for England

Could be the warmest day of the week with temperatures widely getting to near 20C, perhaps a 21/22C in favoured spots.

 

Cold air will erratically spread southwards, complicated by a trough developing on a SW/NE axis allowing low pressure to form and push north east through the UK.

Saturday could see some thundery downpours in the southern half of the UK as any remaining mild/warm conditions and increasing instability allow some big showers to form.

In this run this is actually the best day in the reliable timeframe (including Monday and Tuesday).

 

On Sunday cold air will be continuing its journey southwards, but in the south there is the risk of some heavy persistent rain pushing north east as the low forming over the Bay of Biscay travels this way.

The track of this is still uncertain, in the north brighter and colder conditions with showers (wintry over high ground).

 

By Monday the cold air will be fully established, the models now agreeing on 850s of -4 to -8C, so the snow level might get close to ground level in the north and maybe even the hills in the south could see a wintry mix.

Beyond this is where things get difficult.

We need to watch the area between southern Greenland and Iceland as pieces of cold pooling get left behind by the Scandi trough. How deep these are and their position directly relate to how things will pan out for the UK, the deep pooling will likely initiate a developing Atlantic trough which will allow the Azores high to build back in across Europe and possibly the UK, the outlier UKMO last night might have been extreme, but this mornings output suggests that the run might have had a point with regards to how long the northerly spell will last. As such I think we will need to wait a day or so more to see how next week pans out.

[Frosty.]

The change to colder and unsettled weather is getting closer although saturday will still be on the pleasantly warm side across the south of the UK but with a risk of thundery showers but then it turns progressively colder from the NW, down to low teens celsius in the south by Sunday and lower than that early next week. The Gfs 0z shows a very unsettled spell on the way with stronger winds than of late, at least for a time which will accentuate the cold, especially in the north of the uk and by the start of next week it will be cold enough for snow on northern hills. Later in high res and especially through low res (beyond T+192 hours) shows a change back to warmer and settled spells for the south and east but with the north / northwest staying generally unsettled but becoming milder. I ignored the 6z op because the latest met office outlook (6-15 day) for early may is more in tune with the gfs 0z, i e... trending drier and brighter for the south & east

Edited April 23, 2015 by Frosty.

[Summer Sun]

UKMO back to the unsettled outlook this afternoon

 

 

GFS meanwhile goes for a weak ridge of high pressure for the south it doesn't last much more than a day before low pressure returns whilst in the north with low pressure near by it remains fairly windy with the chance of snow on high ground

 

 

After a few more lows clear away we start and pick up more of a south westerly flow later next week if this did happen temperatures would start and recover

 

[Frosty.]

The ukmo 12z looks a lot colder and much more unsettled than it did on the previous few runs at T+144 hours with widespread showers and hill snow if that verifies, potential big shock on the way with the current warm and sunny (20c max) replaced by much colder and unsettled with Arctic Nly winds (6-9c max), strongest winds in the far north with frequent showers, many of them heavy with hail and thunder and becoming cold enough for settling snow on northern hills and sleet and wet snow in the heaviest showers further south as temperatures drop like a brick during showers before recovering in the sunny spells between the showers.

Edited April 23, 2015 by Frosty.

[East_England_Stormchaser91]

Is it me, or have the models flipped to almost the total opposite as to what they were showing!?!

We no longer have the northerly after the weekend, but a westerly flow then becoming a very mild to warm southwesterly! What a turnaround!

[Frosty.]

Is it me, or have the models flipped to almost the total opposite as to what they were showing!?!

We no longer have the northerly after the weekend, but a westerly flow then becoming a very mild to warm southwesterly! What a turnaround!

Well from sunday and throughout the first half of next week looks cold and showery, well, much colder than now anyway and the ukmo 12z is cold until at least midweek, we might not have a straight northerly but we do have a cold northwesterly of arctic origin, and there would be wintry showers and below average temps so it doesn't look much of a turnaround to me, not until later next week at the earliest. Edited April 23, 2015 by Frosty.

[Summer Sun]

ECM following on from the 00z run with hints of something slightly more settled later next week though with the 850's under the high still below zero temperatures won't be more better than around average though feeling slightly warmer if you have some sunshine and light winds the lightest winds would be in the west with the east still getting a north to North easterly wind

 

 

Then by day 9 the east would loose that nagging wind and it would be the far west starting to turn more unsettled as low pressure edges closer

 

[Frosty.]

This evenings Ecm 12z shows increasingly cold and unsettled weather from Sunday until later next week with cold Northerly winds as shown below, this run and the ukmo 12z are similar and would extend the chilly showery spell until at least next thursday, 522 dam thicknesses at the end of April would be impressive, the ecm shows the unseasonably cold spell lasting all next week, frost risk increases too..so it's the euros v gfs.

Edited April 23, 2015 by Frosty.

[Milhouse]

SWly or NWly. Which is it to be?

 

[Eugene]

SWly or NWly. Which is it to be?

 

 

 

Lets hope for the latter milhouse, nothing worse than mild overcast wet conditions after a gloriously sunny fresh Spring.