PART 2 OF STEVE MURR'S POST.
The ONLY area of fault on the NEW updated ECM has come from the area around the SW tip of Greenland & the speed of the solution- being slow & amplified, in-fact its not 'quite' been there & that subsequent swing to a faster solution has taken the amplification past the point when it no longer goes North, but ENE traversing the coast of southern Greenland.
HERE
What we are talking is an UNDER estimation of the Jet by a maybe a FEW M/S -
The net correction is a 'slightly flatter pattern, a slightly eastward jog (200 miles is nothing in weather terms- but Massive for the UK) & of course 1 full less day of cold as there is no high pressure to traverse around the high but through it.
We need to be clear though the ECM has never promised sustained HLB, just over amplified the ridge towards Greenland.
Incidentally the ECM made a similar mistake the other week, that is- totally lick the GFS in the overall pattern but mistake the over amplification- which again has big repercussions for the UK-
this was the model output ECM
http://www.meteociel...ECH1-144.GIF?12
Notice ridging into Greenland
ACTUAL Varification:
http://www.meteociel.../ECH1-48.GIF?12 -
Notice the flatter upstream pattern- right in the place it hurts for us.
What to take away from the ECM for the rest of Winter, ECM is the leading model over the GFS, it licked the 500 MB pattern 9 days in advance & has stuck with it run after run all the way through, however around the Iceland region it 'sees' more ridging than perhaps is going to happen-
there's not many places in the globe that the extra amplification matters, however at the southern tip of Greenland there comes a cut off where systems all of sudden STOP going North & suddenly start going East- this through an angle of 90 degrees.- so a SMALL error / bias which would normally swing from say 10 degrees to a ever so slightly flatter 20 degrees to the North is suddenly swung from 0 degrees North to nearly 90 degrees East.
This pattern change has a direct impact on the sustainability on UK cold as it shortens the cold & reduces the westerly penetration of cold-
This small error is some peoples eyes is a huge error- hence the calls for the ECM being trounced / its failed its followed the GFS etc etc-
No the model error is small but the visible impact to the UK is huge.- so the perception is skewed towards a thought process that the model is rubbish.
Its not- its king with a bias just like nearly all the models.
In terms of the rest of the Winter wit the ECM I will generally STILL run with this model - why? because the Hemispheric pattern for the last 4 years has been heavily loaded towards Northern blocking so fortunately the ECM bias hasn't been visible due the conditions actually supporting the bias, however this winter thus far that bias has made it look a little foolish - when actually its performed superb.
So for Future budding cold spells look towards Southern Greenland to see if there is any low pressure or shortwave action that is the key trigger - as this may be to slow & to far west in the ECMS eyes- then as it corrects east the low slips east of the tip rather than South.
SW GREENLAND = CRUCIAL TO THE UK COLD.
The GFS model... ( Links are the 12z & 00z model only)
What can I say about the GFS ..... well in the name of balance when the ECM at 216 was picking up the pattern for spot on the GFS was here-
216 00z & 12z
http://modeles.meteo...700-0-216.png?0 Very good but to flat with the US pattern
http://modeles.meteo...12-0-216.png?12 VERY GOOD
192 00z & 12z
http://modeles.meteo...800-0-192.png?0 Pretty good but upstream Midwest low very fast ejecting out to pole
http://modeles.meteo...12-0-192.png?12 AWFUL AWFUL
look at the eastward bias in all its glory our northerly it over into Germany
168 00z & 12z
http://modeles.meteo...900-0-168.png?0 Not bad- pretty close upstream
http://modeles.meteo...12-0-168.png?12 POOR AGAIN- look at that bowling ball low to the NE- but like all the other runs to Greenland ridging
144 00z & 12z
http://modeles.meteo...000-0-144.png?0 V Poor but very flat- +4c isotherm across England some 14 degrees to warm @ 850.
http://modeles.meteo...12-0-144.png?12 Poor again- to far EAST - England has zero cold air. - Eastward bias evident again.
120 00z & 12z
http://modeles.meteo...100-0-120.png?0 Pretty good ticks all the right boxes.
http://modeles.meteo...12-0-120.png?12 Slightly to far east again but catching up & westward correcting.
96 00z & 12z
http://modeles.meteo...0200-0-96.png?0 SPOT ON
http://modeles.meteo...212-0-90.png?12 SPOT ON.
GFS SUMMARY
Why do I personally Hate the GFS- because its always playing catch up to the EUROS, Its always flat when the Euros show an amplified pattern so is wrong nearly every time we get a Scandi or Greenland high.
We get 4 runs a day- which If I overlaid all the other 12 runs would show a multitude of scenarios, some at the extreme eastern end of the range, some over amplified ( looks like the 18z is usually the pub run) & some just on some wild tangent- usually the 06z.
Should I dismiss it- well I'm going to change my tact on GFS, what the faster flat pattern helps to show is usually the opposite of the pendulum, If the ECM is at the slowest amplified end then you can bet your bottom dollar that the GFS will be the flattest, with this in mind quite often the final solution is a blend of each- the halfway house- but normally not quite halfway to the GFS, more like 1 third to the GFS & 2 thirds of the EUROS-
From this you could generate a predicted forecast, but with one very difficult element & that is does the 2 third house create any pinch points that could change the final pattern so drastically for the UK-
2 main areas arise from this- ( For UK cold)- Southern tip of Greenland energy is 1 & the other is when we are setting up Easterlies & low pressures are projected to move south then SW whilst the ridge builds above.-
The fast solution ( GFS ) will throw the low pressure further into Europe - but the bigger impact on the long-wave pattern is instead of a Scandi High you see a 'Sceuro' high, with the UK in a southerly or SE flow & the jet to flat on top.
Then as the Easterly approaches its how far does the GFS move to ECM where the Sceuro is suddenly a Scandi high again because the solution was in-fact slower.
This example is VERY evident tonight.
GFS SCEURO HIGH- http://modeles.meteo...nh-0-192.png?12
JMA Scandi high -http://www.meteociel...92-21.GIF?02-12
This all comes from FAST v SLOW solutions.
Anyway, what to take away from the GFS-
12z Eastward bias. IGNORE- if its significantly FLATTER or EAST than the ECM.
6z/18z . IGNORE - if its significantly different to the ECM.
00z- do not discount- I cannot find to many faults with the 00z GFS- not biased in many ways & generally the most consistent.
What we can also take away is the GFS will find the weaknesses in the blocking first ( usually) because its primed for a faster solution- so that can support us going forward with comparisons with the ECM.
The model that's come out best again is the UKMO- resilient & Smooth, seemless & minimal fuss.
In this case it started at 144 with the 2 thirds house & has never changed since.
The Scandi High..........
I'm pleased that I presented this idea first ( even Mr Holmes questioned the 500 heights not following ANY ridging to Scandi)
The forecast was driven by the angle of the jet coming out of Canada & the subsequent split flow-
It is now appearing in the models-
So what would be tonights forecast- based on the ABOVE model inconsistencies.
GFS- 12z 240- Slight amplification -
http://modeles.meteo...nh-0-240.png?12
But a Euro high-
Mild SW winds for the UK.
ECM 240 12z Much better amplification
http://www.meteociel...H1-240.GIF?02-0 KEEN ESE wind & very cold at the surface, -
JMA 192- Run of the day
http://www.meteociel...92-21.GIF?02-12 Easterly @ 216
GEM 240 - AWSOME
http://modeles.meteo...nh-0-240.png?12
But... the Best suite of the day is the ECM 15 day.
00z Chilly
http://www.knmi.nl/l...0.png&width=692 day 11/12 mean around 4c.
12z very much colder
http://www.knmi.nl/l...0.png&width=692 ( swop to 12z) Day 11/12 mean now down to 2.5c & the control + op very cold.
Therefor the updated forecast based apon the model bias today is-
Northerly toppler, for 24 hours, high pressure ridging over the top but contrary to the GFS no WAA getting into the UK barring the extreme NW -
The SE staying cold-
day 8 -9 look for Energy dropping south into scandi in the form of a shallow low- with rapid pressure building NE, the UK sitting at the extreme western end of blocking for day 9/10.- light Southerly or SE tug.
Then energy getting underneath tugging the winds easterly & increasing day 12.
Look out for the Maps for 13/14 December.
best regards
Steve
Edited by user
Monday, December 2, 2013 10:35:31 PM
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