Model Output Discussion 26/08/2012

[SMU]

Cheers John-

The key for the 06z failings are the regional results in which we really focus on key locales for Winter modelling - IE Arctic, pacific Atlantic basin & Europe are all very poor results-

Especially the arctic as IIRC baloon data is only collected for 00z & 12z model suites.

regards

Steve

[johnholmes]

Cheers John-

The key for the 06z failings are the regional results in which we really focus on key locales for Winter modelling - IE Arctic, pacific Atlantic basin & Europe are all very poor results-

Especially the arctic as IIRC baloon data is only collected for 00z & 12z model suites.

regards

Steve

I have to admit I have not refined any routine check down to the regional outputs but it must be a better idea for any model; what is the current state Steve if you have it please?

Re the upper air data, that point may be valid, there is limited 06 and 18z inputs but it is much less than the 00 and 12z inputs.

[Gibby]

Hi Folks Here's a rundown of the 12zs from GFS, UKMO and ECM tonight.

All models continue to paint a very unsettled picture as we move through the working week. With Low pressure advancing in towards the NW in the next 24 hours and a front moving SE over the UK a band of rain will introduce a protracted spell of showers or longer spells of rain through all 5 working days, peaking around midweek. It will be windy for much of the time as the Low pressure drifts only very slowly East just to the North of Britain.

GFS then builds High pressure down from the NW with most of FI seeing the UK under it's influence with dry and rather cold conditions predominating meaning sunny spells by day and frost and fog patches night and morning.

The GFS Ensembles show fairly average uppers when taken as a whole. There is a large spread though in the second half of the run with many options possible, some warmer, some colder. Precipitation is shown scattered about through the runs with the second half drier than next week indicating high pressure of sorts trying to gain control. The operational and control runs were cold outliers in the second half for scotland and interestingly showed a similar pattern through this stage.

The Jet Stream is shown to dip slowly South over the UK in the coming days before GFS has it breaking up by the second half of next week on the operational as the intervention of High pressure kicks in. the ensemble mean though has it still blowing over the UK by the end of next week if tilting NW to SE.

UKMO for midday next Friday shows a small but vigorous Low over Eastern England as part of a complex Low pressure system to the NE of Britain. Needless to say the weather would be very unsettled with rain, showers and rather cold conditions through the day.

ECM builds a ridge of High pressure in over next weekend to dry things up for a day or so before Low pressure moves back in from off the Atlantic and away to the NE leaving the UK in a chilly and unstable NW flow.

In Summary the pattern is as mixed as ever tonight. The first week is fairly agreed upon by all the models but week 2 is all to play for as the differences between GFS and ECM is quite stark. GFS shows a rather cold High pressure taking full control of the UK weather while ECM has none of it pulling Low pressure back in from the West with the usual cocktail of wind, rain and showers. Who will be right, well I think there will continue to be a lot of changes run to run and model to model over the next few days. One thing is for sure there doesn't look like being an Indian Summer in the UK at the start of this October.

[Glacier Point]

http://www.esrl.noaa...ltaum.90day.gif

.. a very strong mountain torque in progress. That increases confidence in phase 4 type pattern..

A definate nod towards GEFS / NAEFS modelling, against operational 12z ECM which has gone off on one tonight.

[damianslaw]

Its a predominantly unsettled outlook for the foreseeable future - very changeable under a strong atlantic airstream with no signal of anything particularly settled on the horizon nor mild for the time of year - big contrasts to this time last year.

Next 7 days = unsettled, often wet and windy in the north and west and cool for the time of year, becoming notably chilly by next weekend. Further south and east, drier more sunny conditions but temps around average with cool nights. Very very typical weather for early october. Autumn 2012 so far has been text book stuff, early sept being dry warm and settled, by middle of the month much more unsettled with average temps, then we have had the first autumn storm around/just after the equinox (albeit the strongest for 30 years), and now a late sept/early oct period dominated by the atlantic on its traditional westerly axis.. will we get the mid october indian summer (i.e. warmer settled period but cold at night with first widespread air frosts.. ) followed by a stormy very wet end to the month... mmm the long term signals don't favour any mid month warm up, but the stormy very wet end could more likely verify and possibly a cold middle and end to boot - we shall see... a very different october to many recent ones.. more in the vein of 1993 and 2008 than the likes of 2009 and 2010.

Edited September 29, 2012 by damianslaw

[Jack Wales]

There could be a warm up next weekend, especially with the large trough progged for the N Atlantic drawing a warm s'ly flow. There is also a growing signal for heights over Europe and the mid latitudes so I'm not convinced of a stormy month coming up. After next week, I wouldn't be surprised to see an anticyclonic spell...which could be cold or warm depeding on the exact synoptics.

[syed2878]

hey guys this is i beleave the discussion for the 12Z model runs for the 29th sep. From the NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD

959 AM EDT SAT SEP 29 2012

VALID 12Z WED OCT 03 2012 - 12Z SAT OCT 06 2012

EARLY IN THE FORECAST PERIOD...D3-D4...CONTINUED WITH THE 00Z

OPERATIONAL UKMET/GFS/ECMWF THEME AND A SPLIT-FLOW REGIME ACROSS

THE NORTH AMERICAN CONTINENT.

THE SOUTHERN STREAM DOMINATED BY THE SUBTROPICAL MOISTURE PLUME

AND RATHER UNUSUAL SHORTWAVE...BY LATE SEPTEMBER STANDARDS...WITH

ORIGINS IN MEXICO...TRACKING THROUGH THE OHIO VALLEY AND

NORTHEAST. THE NORTHERN STREAM SYSTEM TRACKING THROUGH SOUTH

CENTRAL CANADA AND THE ATTENDANT CANADIAN FRONT WILL BE A TRICKY

PATTERN TO TIME...WITH THE AIRMASS RATHER SHALLOW ALONG ITS

SOUTHERN FRINGES...AND A DEEP UPSLOPE COMPONENT SETTING UP BEHIND

IT ACROSS THE NORTHERN/CENTRAL HIGH PLAINS.

BEYOND D5...GENERALLY FOLLOW THE 00Z EC MEANS/OP ECMWF WITH A

NORTHERN STREAM DOMINANT PATTERN AND MIGRATORY UPPER RIDGE

TRACKING EWD THROUGH THE NORTHERN ROCKIES.

VOJTESAK

[Frosty.]

The latest ensemble mean (gfs and ecm) continues to show an anticyclonic spell dominating the outlook beyond the next 5 days with light winds and sunshine but with overnight mist and fog and a touch of frost but there are signs of a warm up as the airflow becomes sourced from southern europe with low pressure held back well into the atlantic and high pressure over the near continent, the ensemble mean is quite bullish about this, much as it was yesterday. The gfs ens mean does eventually show the anticyclone being shunted away as low pressure moves in from the northwest and the mid october charts indicate a collapsing atlantic ridge and the jet tilting nw/se with a hint of a possible blast of cold zoneality soon after mid month, so although the next 5 days or so look fairly unsettled, it still looks like a benign spell will follow.

[tinybill]

http://www.meteociel.fr/modeles/gfse_cartes.php?mode=2&ech=204

morning all just looked deep in to fantasy word could see problems with flooding again as its looking very wet , plus just been reading the sun weather forecasters are saying the U.K. could expect an early winter!!

[Gibby]

Good morning. Here is my latest look at the 00zs for this morning Sunday September 30th 2012.

All models are fairly clear and straightforward on events this week. An unsettled and breezy week looks likely as westerly winds in association with Low pressure drifting slowly East to the North of Scotland pushes troughs and showers across all areas at times through the week.

GFS then brings a Euro High closer to the SE backing winds off towards the South and introducing some drier and milder conditions for the SE while the weather stays unsettled elsewhere. Through FI and the High declines away East as Low pressure drifts slowly across Britain from the West and become a complex system which continues to influence the weather through to the end of the run with much wet and cooler weather for all.

The GFS Ensembles look rather wetter again this morning. There is some indication of slightly warmer uppers in a weeks time but these look to be swept away quite quickly as cooler ones move back in association with Low pressure. the operational was a warm outlier in this warmer phase.

The Jet Stream currently running East across Britain for several days sinks south through the Atlantic according to the GFS Ensemble mean in the following days.

UKMO for midnight on Saturday shows High pressure moving into Western Britain bringing a cool, dry and bright day next Saturday once remaining showers in the NE clear away.

ECM is very similar to UKMO at 144hrs today migrating High pressure across and away to Scandinavia in the days that follow allowing Low pressure to move up from the South with rain in tow and rather chilly air on it's northern flank.

In Summary the pattern this week is agreed with a showery and unsettled week for all areas. Nex weekend looks quite promising as a ridge of some sorts look like affecting most areas for a while before a slow decline back to more unsettled conditions develop thereafter though the ways we arrive there differ between GFS and ECM.

[johnholmes]

http://www.meteo.psu.edu/~gadomski/ECMWF_0z/hgtcomp.html

is the output this morning and gives a very good example of when they are pretty unlike one another over much pof the chart.

Little confidence with this type of output for the time scale shown. The only thing they seem to agree on in the UK area is a 500mb flow from s of west! I suppose there is some agreement of rising heights over some part of Europe but just where is not clear, south or north?

[phil nw.]

http://www.meteo.psu...0z/hgtcomp.html

is the output this morning and gives a very good example of when they are pretty unlike one another over much pof the chart.

Little confidence with this type of output for the time scale shown. The only thing they seem to agree on in the UK area is a 500mb flow from s of west! I suppose there is some agreement of rising heights over some part of Europe but just where is not clear, south or north?

Yes the Operationals are different at that timescale John-the complications of a split Jet coming off the States?

Looking at the means at T192hrs they seem to favour Heights further south.

An Atlantic trough just to our west-depending where this is finally situated could give us a little spell of warmer and brighter conditions from next weekend.

[Thundery wintry showers]

The latest GFS runs are reminding me of early October 1995, which started with a week of windy and showery west to south-westerlies, and then a southerly incursion on the 8th/9th which brought unusual warmth, and plenty of sunshine to most places. The GFS is indicating similar temperatures for next weekend, with 21-24C over a wide area on Sunday when you account for the GFS's traditional underestimation of maxima:

http://cdn.nwstatic....180/h500slp.png

http://cdn.nwstatic....6/ukmaxtemp.png

However I don't think it is very likely to come off, as the UKMO and ECMWF are going for a very different picture- we still get a ridge of high pressure, but we get a cool bright showery west to north-westerly regime on Thursday/Friday which would set us up for a dry sunny cool weekend with overnight frosts.

Before that, next week looks like being showery but also quite bright, with a slow moving low pressure giving us relatively little frontal activity, although as always in these setups there is potential for disturbances to turn up nearer the time and turn sunshine and showers into a cloudy wet scenario from time to time.

[bluearmy]

No confidence in developments beyond the ridging but I note that ECM spreads day 10 have a ridge to our west and the mean shows troughing to our se. ECM op fi seems to want to retrogress the Russian ridge - maybe it's picking up the right signal, just in the wrong place! Given Stewart's thoughts on where a big MT event would take us, the models may be 'fishing' around a bit in fi though the T192 means look fairly consistent, though without the cross model operational support that JH likes to see.

[TonyH]

My look at the week ahead, anything possible next weekend!

http://forum.netweather.tv/blog/309/entry-4481-weather-guide-sunday-30th-september-to-sunday-7th-october-west-wales-and-the-midlands/

[Bobby]

Could be a very wet week or so to come

[Frosty.]

There is now increasing uncertainty in the further outlook beyond the anticyclonic spell which is currently due to begin next sunday and well into the following week, the meto had been confident that it would only be a fine interlude before the next batch of unsettled weather rolled in off the atlantic but the benign nature of the ensemble mean (gfs and ecm) has perhaps changed their thinking although they have a lot of additional data that we can't access in the public domain, so we could be looking at a rather more prolonged fine spell with pleasant sunny days but misty/foggy chilly nights with some ground frost. The next 5 or 6 days look unsettled with sunshine and showers (+ longer periods of heavy rain in places) and windy at times, it also looks like turning cooler as the week goes on with temps dipping below the seasonal average but probably too much cloud and breeze for any frost until the pressure rises.

Edited September 30, 2012 by Frosty039

[minus 9]

looking at the charts i cant help thinking the euro high could really show its hands after the weekend.

[BLAST FROM THE PAST]

Interesting to me is watching the changes to model runs but also the subtle hints that they are grappling with what the background signals may be pointing to. I read GP's thpughts yesterday on P40, general pressure pattern of LP over Europe and HP over/to N and NE of UK. An easterly flow.

ECM 00z gets there, GFS to me grappling with jet stream heading south with some tasty LPs/secondary LPs to crash over us but initially into idea of the Euro Heights being high. I think that the Euro heights will get shunted away with pressure likely to fall with a disrupted or southerly jet pattern. Looking at 7-10 days ahead here, that's my favoured outcome.

BFTP

Edited September 30, 2012 by BLAST FROM THE PAST

[BLAST FROM THE PAST]

12z brings in the dreaded PV, monstrous in FI. No wonder its quiet in here.

BFTP

[camiscool]

whats PV?

[Eskimo]

whats PV?

Polar Vortex, can't give you any more information because I don't fully know what they do.

[Chris K]

All ive heard is that a strong polar vortex tends to mean a milder UK winter overall depending on its position. I believe its ONE of the reasons why last winter was quite mild for a lot of it?

Im sure one of the more knowledgeable folk will explain/point you in the right direction.

Edited September 30, 2012 by Chris K

[Zenarcher]

whats PV?

Polar Vortex, Wiki has a good article about it http://en.wikipedia.org/wiki/Polar_vortex

Basically it's not what you want to see if your looking for cold weather. We had it for most of the winter last year.

[SnowObsessor90]

12z brings in the dreaded PV, monstrous in FI. No wonder its quiet in here.

BFTP

The beginning signs of deja vu from last year perhaps with a big fat euro high sat right over us?

It's still early days of course but it certainly isn't a theme you'd like to see starting to persist.....

Edited September 30, 2012 by Anonymous21