Model Output Discussions 12z 03/05/2016

[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 MONDAY MAY 16TH 2016

THE CURRENT GENERAL SITUATION High pressure lies just to the West of the British Isles but will decline tomorrow as winds back from a chilly NNW flow to a WSW flow tomorrow with a trough of Low pressure approaching the West late on Tuesday.

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

CURRENT SNOW FORECAST AND/OR FREEZING LEVEL OVER THE UK The freezing level across the UK will rise over the coming days as the chilly NNW flow weakens and backs towards the WSW through this week. From a level of around 3000ft at first it should rise to at least 5000-6000ft for several days.

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

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

MODELS-2 WEEK HEADLINE Rather changeable with some rain or showers at times but some dry and brighter periods as well especially in the South and East.

THE GFS JET STREAM FORECAST The slack Jet flow currently will strengthen across the Atlantic and move towards Western Britain by Wednesday. It then continues blowing quite strongly for the time of year moving East then SW to NE towards and over next weekend. The flow then weakens through Week 2 and breaks up as higher pressure develops over and later to the North of the UK with a split flow then both North and well South of the UK.

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

NEW GFS OPERATIONAL The New GFS Operational Run today shows the current ridge of High pressure weakening and being replaced by a strengthening Westerly flow for the remainder of the week and next weekend with rain and showers spreading to all areas from the West. This unsettled phase peaks at the weekend when gales are possible in exposure before a transformation into High pressure develops through Week 2 with fine dry and warmer conditions developing for all while an easterly flow develops across the UK and with thundery Low pressure down to the South again some thundery showers could edge up into Southern Britain at times again by the end of the period.

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

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

GFS CONTROL RUN The Control Run sees things rather differently this morning in the second week with the High pressure of early next week gradually declining away to the SE with a breakdown occurring from the Atlantic rather than the South like the Operational shows. So after the unsettled phase of this week a drier phase early next week when it becomes warmer is gradually replaced by rain at times especially towards the North and West later in the second week.

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 clustering today for day 14 shows no clear cut direction in what may be thrown at us at that time point with a lot of clusters indicating fairly slack conditions across the UK about equal in measure between slack Low and High pressure areas in proximity of 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 The UKMO model this morning shows an unsettled spell developing for the UK this week and lasting through next weekend too with brisk West or SW winds carrying bands of rain, heavy at times but with some brighter weather with heavy showers in between. Temperatures remain near average by day but will be much milder by night than currently.

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

THE FAX CHARTS The Fax Charts show the slack High pressure ridge across the UK currently subsiding away South and being replaced by WSW winds and a whole plethora of troughs moving East across the UK for the remainder of the week and into the weekend with showers or longer spells of rain at times for all.

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

GEM The theme of GEM too is for Low pressure to bring a change to Westerly winds and rain at times towards midweek in association with low pressure close to NW Britain with further spells of rain and showers under a similar guise through next weekend before better weather develops early next week as pressure is shown to rise across the UK and then remains High over the North next week while the South sees the return of thundery rain later as Low pressure edges North towards SW England by the end of the period.

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

NAVGEM NAVGEM is not available this morning at time of issue of this report. 

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

ECM ECM today also shows the unsettled spell starting late on Tuesday with periods of rain and showers across all areas for that period sometimes heavy and accompanied by fresh winds from a Westerly source. Then as we move through next week winds back SW as pressure rises to the SE and a NW/SE split in the weather looks possible with rain and showers continuing across the North and West while longer dry spells and more occasional rain is likely in the SE where it looks like it could become rather warm for a time at least.  

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

ECM 10 DAY MEAN (12z) The 10 Day mean Chart from last night shows Low pressure across the Atlantic and a bias of High pressure just to the SE and east of the UK with a weak SW flow delivering some rain and showers at times, perhaps thundery in places as the South or SW flow indicated brings relatively warm and humid air up across the UK at times especially in the South and East.

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

NOTABLE TRENDS & CHANGES FROM PREVIOUS RUNS The theme from the models today continue to paint a more unsettled phase of weather to come before things become more uncertain thereafter.

31 DAY HISTORICAL VERIFICATION STATS FOR GFS, UKMO & ECM The verification Statistics of GFS, UKMO and ECM show at 24 hours ECM ahead at 99.5 pts with UKMO at 99.4 pts and GFS at 99.2 pts.  At 3 days ECM is leading with 97.3 pts to UKMO's 96.2 pts while GFS lags behind at 95.7 pts. At 5 days ECM leads with 88.7 pts to UKMO at 86.8 pts and GFS at 83.8 pts. Then at 8 Days ECM has the leading spot from GFS with 61.2 pts to 49.3 pts. Finally at Day 10 ECM has the lead from GFS with a score of 44.0 pts to 36.5 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 weather is about to turn rather more unsettled across the UK as the chilly NW flow gives way to a stronger WSW flow from later tomorrow on with troughs of Low pressure delivering spells of rain and showers for the remainder of the week. The one good thing is that all risk of frost by night will be removed after tonight as wind and cloud cover serve to hold night temperatures up. By day temperatures will stay close to average and it will feel warm in any sunshine between the showers. Over the weekend it maybe that the peak of this unsettled phase of weather will occur with strong winds for some accompanying more rain and showers but from the start of next week on there are tentative signs of a change to somewhat or maybe entirely drier conditions with higher pressure building in the proximity of the UK with time, settling the weather down with warmer conditions in place too. The method in how this develops is still very uncertain and it may not be the start of a sustained fine and settled spell as various outputs push the High to the North with thundery Low pressure edging up from the South while other outputs hold High pressure closer to the SE with the NW seeing some more unsettled conditions moving in against the higher pressure from off the Atlantic. What I can say though is that it looks as though temperatures will be fairly comfortable over the period resulting in any sunny spells between the outbreaks of rain feeling rather warm and frosts at night will hopefully become a thing of the past for this season and while there is no sustained fine and warm weather shown to last long all in all conditions shown within this morning's output could be a lot worse and represents fairly standard late Spring conditions across the UK. 

Next Update Tuesday May 17th 2016 from 09:00

[knocker]

Needless to say the ecm ops is having nothing to do with the gfs evolution for next week and continues to track Atlantic systems into the UK. Given this is ops output over a week away one musn't read too much into this so await to see what the anomaly comes up with

[Singularity]

With GFS moving toward ECM in terms of keeping LP more NW of the UK Thu-Sat, we have a loose consensus on temperatures tending to do quite well, especially in the southeast where spells of rain will be fewest and furthest between. High teens are achievable on a couple of the days, perhaps all three. Further north and west, a gradual fall off of peak temperatures toward the mid-teens, with low-teens for parts of Scotland where it will, unfortunately, feel a bit naff, particularly in the west - but given what those parts had last week, it should not seem as unfair as usual .

Longer term, ECM is reluctant to dig the jet south in the Atlantic, maintaining a tendency for the warmest and driest conditions to be in the southeast.
By contrast, GFS has the jet tracking well south and supporting a low west of Europe, this supporting a strong cell of high pressure that pushes across the UK from the west, but tends to sit at a latitude too high for England and Wales to see warm weather establishing. The finest conditions end up returning to Scotland!

If the low is pulled west after day 10, as appears possible, then the ECM run holds more promise for warm, settled weather to establish across southern parts at least. If not, the GFS route is perhaps a safer route for attaining a lot of dry weather, but southerners in particular could do with the flow aligning more south of east. In the GEFS, the potential for that outcome is certainly there - indeed some of the perturbations hint at something similar to last week's setup, though not with such a deep low to the south.

 

 

Of some concern is that both models are suggesting anomalously high pressure will return to the Arctic in the 8-10 day period, with GFS maintaining that thereafter. This is not necessarily a problem for the UK if the highs position more toward the Pacific side - but for the sake of the sea ice, a broadly lower pressure environment up there is greatly desired (but without any strong storms - which is easier said than done with so much extra open water around).

 

[Vorticity0123]

Interestingly for friday, the GFS shows a rather strong jet stream crossing the Atlantic towards the UK. In such situations there is often a risk of disturbances rapidly deepening along the polar front into significant low pressure systems.

Jetstream forecast of the GFS as of Friday 00Z.

In such situations storm tracks would probably aim for the UK and just north of that area if one disturbance finds a sweet spot to form in (preferably the left exit of the jet stream). The GFS shows this development to a certain extent.

Surface pressure (white) and geopotential height (colours) on Friday 00Z.

Encircled is a disturbance that would in this case have the potential to develop into a potent low pressure area. This low pressure is by then located along the polar front (not shown here).

28 hours later, this disturbance has developed into a significant low pressure just to the north of Scotland (once again encircled in black). The low pressure has attained a central pressure of 985 hPa here, which equals to a deepening of about 25 hPa in just 28 hours!

Surface pressure (white) and geopotential height (colours) on Saturday 06Z.

Given the small scale of the possible low pressure area, and the timeframe in which it would develop (4-5 days out), this low pressure area may develop in a completely different way, or not develop at all. It is just to show that the potential exists for a significant low pressure area to form. The ECMWF does not support this idea, whereas the UKMO does (but it takes a different path to get there). It will be interesting to see whether, and if so, how this strong jet stream potential will be 'used' by any disturbance along the polar front.

 

Edited May 16, 2016 by Vorticity0123
Corrected grammar mistake and quantified significance of low pressure area

[knocker]

Just to add one thing to Vorticity's analysis and that would be just 12 hours later...............And funny enough the ecm was developing this a couple of days ago and running it into southern England.

Edited May 16, 2016 by knocker

[knocker]

Looking at the ecm anomalies this morning suffice it to say they are sticking to previous runs. That is during the 8-13 period th upper trough to the north retracts to the trough mid Atlantic which does allow for HP nudging into the south but it's confined to this area as the aforementioned trough moves a little east. And NOAA has never been happy with this build up of heights in the eastern Atlantic in any case. It looks at the moment that the GEFS is a wee bit on it's own.

 

[wishingforsnow]

As it stands ECM's output is more palatable than the GFS (as it often has been recently ) so it is good to see that at the moment ECM appears to have the outputs with the most support  as GFS would have the unsettled weather continue into next week whilst ECM is showing high pressure edging in again after the weekend.

Edited May 16, 2016 by wishingforsnow

[northwestsnow]

Looking pretty unsettled on the 0z runs with the jet progged to be unfavourable for any sustained ridging from the azores.

6z showing some very suppressed temps for the last week in may..

Edited May 16, 2016 by northwestsnow

[wishingforsnow]

5 minutes ago, northwestsnow said:

Looking pretty unsettled on the 0z runs with the jet progged to be unfavourable for any sustained ridging from the azores.

6z showing some very suppressed temps for the last week in may..

GFS also showed some very suppressed temperatures under the 'Northerly' during the weekend just gone. ECM were closer to the mark on that one rather than the silly cold the GFS was showing, so hopefully their output does end up being the form horse for the last week of May. GFS has a tendency to overblow low pressure and cooler weather too.

[Man With Beard]

Vorticity - yes that has been on my mind too

What we've seen in the past few days is on absolutely typical example of what the models often do. How many times have we seen this over the years? In the mid-long range, the models pick up on the macro-signal to push heights from the Azores towards the UK. Look at ECM archive charts below at T240/T216 for the coming Saturday:

  

Then, around D6-D8, the models pick up on micro-signals, usually being extra disturbances coming from the Atlantic and, with heights being too weak to withstand, we see a turnaround - BBQ charts replaced with umbrella ones. As shown on the ECM at T192/T168/T144 below:

    

But there's often one last twist in the tale, and this is the one I don't really get - just before the point of no return, the models decide that there was actually some merit in the macro-signal after all and there is a slight backtrack on the dominance of the Atlantic. And hey presto - here's today's ECM for Saturday - now at T120 - the bump of heights towards NW Europe is back:

I reckon that the T120 result is what happens 70% of the time when the T240-T144 pattern shown beforehand occurs i.e. when a decent pattern in the long range gets overridden in the mid-range, there seems to be a small bounce-back to the original pattern just before FI ends.

OK - in this case, the implications are small - areas to the south and east of London may get two decent, warmish days on Friday/Saturday, but apart from that it's pretty wet - time has gone for a big enough correction to allow more areas escape the unsettled weather. But when the weather seems on an Atlantic knife-edge, where it could go either way, I would suggest looking back at what the signals were in the T200-T300 range - more often than not, the weather will nudge back in that direction slightly, especially when there was a big turnaround between T150-T200. Doesn't always work but if you look for this over the summer I think you'll find this idea is right more than wrong.

 

Edited May 16, 2016 by Man With Beard

[wishingforsnow]

9 minutes ago, Man With Beard said:

Vorticity - yes that has been on my mind too

What we've seen in the past few days is on absolutely typical example of what the models often do. How many times have we seen this over the years? In the mid-long range, the models pick up on the macro-signal to push heights from the Azores towards the UK. Look at ECM charts at T240/T216 for the coming weekend:

  

Then, around D6-D8, the models pick up on micro-signals, usually being extra disturbances coming from the Atlantic and, with heights being too weak to withstand, we see a turnaround - BBQ charts replaced with umbrella ones. As shown on the ECM at T192/T168/T144 below:

    

But there's often one last twist in the tale, and this is the one I don't really get - just before the point of no return, the models decide that there was actually some merit in the macro-signal after all and there is a slight backtrack on the dominance of the Atlantic. And hey presto - here's today's ECM at T120 - the bump of heights towards NW Europe is back:

I reckon that the T120 result is what happens 70% of the time when the T240-T144 pattern shown beforehand occurs i.e. when a decent pattern in the long range gets overridden in the mid-range, there seems to be a small bounce-back to the original pattern just before FI ends.

OK - in this case, the implications are small - areas to the south and east of London may get two decent, warmish days on Friday/Saturday, but apart from that it's pretty wet - time has gone for a big enough correction to allow more areas escape the unsettled weather. But when the weather seems on an Atlantic knife-edge, where it could go either way, I would suggest looking back at what the signals were in the T200-T300 range - more often than not, the weather will nudge back in that direction slightly, especially when there was a big turnaround between T150-T200. Doesn't always work but if you look for this over the summer I think you'll find this idea is right more than wrong.

 

That is a good analogy - seems the standard weather pattern for summer for an island between the Atlantic Ocean and Mainland Europe, but occasionally deviates due to extremely good or bad synoptic patterns respectively where either heights over Europe (1976, 2003, 2006) or the Atlantic (2007, 2011, 2012) is the dominating influence. Other than that the weather is in principle, a mixed bag of both for this isle during the summer season 

Edited May 16, 2016 by wishingforsnow

[northwestsnow]

Gfs6z looks better in FI with HP becoming more influential -

[knocker]

1 hour ago, wishingforsnow said:

As it stands ECM's output is more palatable than the GFS (as it often has been recently ) so it is good to see that at the moment ECM appears to have the outputs with the most support  as GFS would have the unsettled weather continue into next week whilst ECM is showing high pressure edging in again after the weekend.

Are you sure you haven't got that the wrong way round?

[wishingforsnow]

12 minutes ago, knocker said:

Are you sure you haven't got that the wrong way round?

Isn't the 06z GFS run showing unsettled weather continuing into the last week of May? I thought the ECM runs for that period looked better. Although as mentioned before, the 06z is showing high pressure at the end of the run so if that came off it would be a silver lining at the end. 

Edited May 16, 2016 by wishingforsnow

[knocker]

1 minute ago, wishingforsnow said:

Isn't the 06z GFS run showing unsettled weather continuing into the last week of May? Although as mentioned before, the 06z is showing high pressure at the end of the run so if that came off it would be a silver lining at the end. 

Well I was looking at the 00z runs but the ecm certainly isn't showing High pressure edging in after the weekend. Anyway all a bit academic as there is plenty of time for revision.

[wishingforsnow]

I'd say with the GFS the High Pressure arrival is delayed by a week but ECM would have it arriving earlier (much like what Matt Hugo was hinting towards a few days ago). Either way, if ECM is closer to the mark then so much the better, with GFS we would have to endure a last week of May with cooler and more unsettled weather (like 2006 and 2014) but if the High Pressure did arrive after that in time for summer then it's not so bad after all 

[phil nw.]

The 12z UK and GFS runs continue to show more unsettled weather on the way from mid-week and this unfortunately looks like lasting into the weekend with low pressure around the UK.

UKMO and GFS next Saturday showing the path of the jet across the UK

                                                                                      

signs of some improvement in the following week though from the GFS mean output as pressure starts to rise from the south west.

Uncertainty on how long lasting any improvement will be continues though and this may only be transient ridging before the next low from Atlantic moves in.The problem is that there is no indication of the jet moving north of the Uk yet which leaves us prone to another period of unsettled conditions between any ridging.

 

 

[mb018538]

Utterly horrific output tonight that wouldn't look out of place in Autumn! Fired up jet stream and low pressure steaming straight into the uk. Anything beyond this is as good as guesswork, but until the end of next weekend we can expect plenty of unsettled weather.

[knocker]

The GEFS anomalies tonight are still plugging ridging just to west of the UK as the trough to the NE weakens by the 24th, This would portend a start of some more settled and warmer weather. In fact as we progress through the run, although the Atlantic trough does nudge east indicating some unsettled weather for the NW with the south and east remaining dry, this does appear to be the scenario it's indicating until the end of the month.

[johnholmes]

1 hour ago, mb018538 said:

Utterly horrific output tonight that wouldn't look out of place in Autumn! Fired up jet stream and low pressure steaming straight into the uk. Anything beyond this is as good as guesswork, but until the end of next weekend we can expect plenty of unsettled weather.

A few charts to illustrate your view of, I assume, the GFS output might make things a bit clearer, perhaps?

[mb018538]

Try these :-) 

 

 

[ANYWEATHER]

Good Evening folks! Gfs and ecm trying to show some settled conditions from the weekend onwards but the last few runs ecm no gfs yes! BBC News 24 have showed high pressure moving in from this weekend onwards. In my eyes Ecm ops are completely wrong , my money is on the GFS!!!!

[Methuselah]

From carrying-out my normal 'blurring' tactic, the models together with the MetO's further outlook seem to suggest pretty normal May fayre: rain at times, sun at times, but temps perhaps a tad above normal. So it doesn't look too bad - does it?

[wishingforsnow]

GFS is improving by showing High Pressure moving in and changing the position of the low in the Atlantic so its no longer to the West of the UK. More runs are needed but judging by the Met Office current outlook and what Matt Hugo has been hinting, perhaps the jet will move north allowing for some hot spells post the unsettled weather during the middle/end of the week. ECM still looks like the quicker option for this path rather than the GFS which keeps the jet firmly south for the last week of May although the High Pressure does make tentiative inroads at the end of the run in FI. At worst regarding the prospect of a settled warm/hot spell it looks as though a North South split may develop with the jet running through the middle of the UK - giving at least the South access to the European heat and high pressure though it wouldn't take a lot of tweaking for it to spread to all of the UK 

Edited May 16, 2016 by wishingforsnow

[knocker]

The eps anomalies this evening are certainly not in agreement with GEFs regarding the high pressure being the main player after next weekend which rather supports the ops. The best that can be said is it does introduce brife ridging on Tuesday, brief being the operative word, before the Atlantic trough comes into play driven by the deep upper low Northern Canada. Thus becoming unsettled again although the south east may retain some more settled and warmer weather.. Towards the end of the run as the trough weakens and retrogresses there are indications, albeit quite slight at the moment, of HP perhaps edging north but really it's mainly a zonal flow which really is bit indeterminate.

Having said that NOAA doesn't take quite such an apocalyptic view, regarding the trough but neither does it indicate height rises in the eastern Atlantic. None of this entirely satisfactory but one is inclined to think the GEFS might be over egging it a tad.

.

Edited May 16, 2016 by knocker