Model Output Discussion

[Geordiesnow]

18z is Not looking as good as 12z and seems to be going towards Ecm with that 1000 mb low above our high. Although it does start to fill at +162 .

Indeed but at least the trend for high pressure to affect our weather is still there - whether this will lead to a cold spell remains to be seen but i am happy with this run. It could be much worse.

[kold weather]

Temps are not really all that cool at all with the high that builds over us at 144hrs, can only guess the easterly drift picks up quite a lot of modification from a still fairly mild north sea. Still I suspect this is probably a classic case of the GFS totally missing inversions...I seen countless times GFS forecast maxes of 5-8C only for the fog to stick all day and keep maxes close to freezing.

Not as good as the 12z, general trend isn't bad however and at this stage thats what counts.

[essexblue]

Been watching on year for years not posted much but just have to say 1981

[Cal]

General evolution of the pub run is roughly the same, albeit a slight delay with the cold, which is expected, how far the cold air moves westwards is another matter but there is at last some general agreement in the longer term, and drier hopefully too !

[cyclonic happiness]

All still moving in the right direction IMO , let's see what the ensembles bring, my bet is near the middle for this run.

[Thundery wintry showers]

The 18Z scenario with a fairly cold anticyclonic interlude and the cold air just missing us this time around is, IMHO, the most likely evolution. It should at least give western areas a relief from the cloud and rain if it comes off.

[Duncan McAlister]

Strange run, it becomes colder as zonality returns....

[Ben_Cambs]

A slight downgrade from the 12z run, although things still look good, a delay in the colder weather is shown in the latest run

[snowmadchrisuk]

Parallel run out to +180 and it is just as good as it was earlier. I think the 18z operational will be on the warm side of the Ensembles in FI.

EDIT : The run now fully out and it is an absolute Cracker ..

Edited December 4, 2009 by snowmadchrisuk

[nick sussex]

Indeed but at least the trend for high pressure to affect our weather is still there - whether this will lead to a cold spell remains to be seen but i am happy with this run. It could be much worse.

It's very encouraging to see some consistency with at least the euro high looking like it could bring an end to the rain, given where the output was a few days ago today has been a real step forward and you're totally right it could be much worse.

Whatever happens in the lower resolution part of the output isn't really important for the timebeing, the building blocks have to be laid early and its crucial that we see the euro high ridge as far north as possible, the further west we can get the trough and the more this digs south the higher the chance that we'll see something much more interesting later.

Edited December 4, 2009 by nick sussex

[Optimus Prime]

A typical recent December pattern after 1996. Mild either side with a cold anticyclonic spell giving rise to fog and frost.

[cooling climate]

The parallel run still very much game on.

Biggest difference I could see on 18z compared to 12z GFS run was at t240 on the

n/hemisphere charts the 18z had a 1000 mb low while the 12z had a 1040 high over

the pole.

Edited December 4, 2009 by cooling climate

[on the coast]

The 18Z scenario with a fairly cold anticyclonic interlude and the cold air just missing us this time around is, IMHO, the most likely evolution. It should at least give western areas a relief from the cloud and rain if it comes off.

I agree. The cold must always be favourite to go South. However exciting charts.

[kold weather]

Strange run, it becomes colder as zonality returns....

Yeah I noticed that, though the HP orginally isn't sourcing air thats actually all that cold, we'd need inversions to do the trick, meanwhile the weak ridge that remians in place around 360hrs is dragging air from the south which is sourced from the orginal cold pool thus actually surprisingly cold given what the synoptics suggest.

Still you may as well throw the GFS temp forecast into the rubbish bin, as I said before it can be way out in those anticyclonic conditions. Also all in all a rather cold run, depsite the synoptics not being nearly as good, but its closer to what I expect to be the eventual outcome.

ps, the Paralell run is immense however it has to be said...

[Methuselah]

I have to say, that the current indications point at a typical '60s-type Xmas...Anywhere between 7 and -1C looks possible for SE England? At any rate, it's not the 'standard fayre' that we've been used to for many years...

Three cheers for uncertainty!

[bluearmy]

no shortwave on the parallel = stonking FI

if you are looking at the cold coming quicker and more reliably, then you dont want the shortwave ejecting ne. with the shortwave, there is pressure on the block forcing it where we dont want it and if it misses the chance to get sucked into the arctic ridge, we could get stuck with it a la GFS 18z op. as nick says, still better than the atlantic conveyer belt of depressions but the chance of the parallel being right and ecm + ens being wrong?

[snowmadchrisuk]

ps, the Paralell run is immense however it has to be said...

The Paralell run is even better than GFS 12z , it set's us up for a prolonged Cold Spell with very cold 850's from next Sat 12th

[NorthantsSnow]

The 18z is probably as close to the middle scenario as you could get with the coldest air never quite reaching our shores but at the same time never very far away.

At +216 I thought we were heading for something colder but it didn't quite happen. Interesting how far south that cold plunge ends up though, albeit no consolation for us Brits if it were to materialise!

[SMU]

Yeah I noticed that, though the HP orginally isn't sourcing air thats actually all that cold, we'd need inversions to do the trick, meanwhile the weak ridge that remians in place around 360hrs is dragging air from the south which is sourced from the orginal cold pool thus actually surprisingly cold given what the synoptics suggest.

Still you may as well throw the GFS temp forecast into the rubbish bin, as I said before it can be way out in those anticyclonic conditions. Also all in all a rather cold run, depsite the synoptics not being nearly as good, but its closer to what I expect to be the eventual outcome.

ps, the Paralell run is immense however it has to be said...

What I am also noticing in the model output is the fact that we get into a continental flow from around t150 as the surge of warm air moving towards iceland-

Not exactly the beast from the East- however not to be sniffed at & a far cry from recent decembers...lets see the ensembles-

Irrespective of whether its going to be resolved tonight who can find the best chart!!!!!!!!

S

[Cloud 10]

Parallel run out to +180 and it is just as good as it was earlier.

Certainly is a cracker,no shortwave to stop our high ridging north leading to an easterly then north-easterly combo courtesy of big heights over greenland. Meteociel - Cartes du modèle numérique GFS pour l'Europe

[LomondSnowstorm]

With the parallel run replacing the current operational run in a few weeks, this could be an interesting test of it's accuracy, to see whether using it as the main model is really a wise move. Anyway, the Euro high being consistently in the higher resolution timeframe, as odd as it sounds to say this, is a good sign, but as Nick says, we don't yet know how it will develop from there.

CW

[Paul]

The Paralell run is even better than GFS 12z , it set's us up for a prolonged Cold Spell with very cold 850's from next Sat 12th

Quick reminder for those who don't know - the parallel run becomes the operational on the 15th December - pretty major upgrade:

EFFECTIVE DECEMBER 15 2009...BEGINNING WITH THE 1200

COORDINATED UNIVERSAL TIME /UTC/ RUN...THE NATIONAL CENTERS

FOR ENVIRONMENTAL PREDICTION /NCEP/ WILL UPGRADE SEVERAL

COMPONENTS OF THE GLOBAL FORECAST SYSTEM /GFS/.

NEW DATA SOURCES AND IMPROVED NUMERICAL TECHNIQUES WILL BE

INCLUDED IN THE GRIDPOINT STATISTICAL INTERPOLATION /GSI/

ANALYSIS.

THE POST PROCESSORS USED FOR THE GLOBAL FORECAST SYSTEM

/GFS/ AND THE GLOBAL DATA ASSIMILATION SYSTEM /GDAS/ WILL BE

UNIFIED AND TWO MINOR CHANGES WILL BE INTRODUCED INTO THE GLOBAL

FORECAST MODEL. UNIFICATION OF THE POST PROCESSING CODES WILL

RESULT IN SLIGHTLY LESS SMOOTH FIELDS IN THE GDAS.

IN ADDITION THE ACCURACY IN THE FORMULATION OF A NUMBER OF

DIAGNOSTIC VARIABLES WILL BE IMPROVED AND ADDITIONAL

PARAMETERS WILL BE ADDED TO THE MODEL OUTPUT FILES.

THE ANALYSIS CHANGES INCLUDE:

-ASSIMILATING TROPICAL STORM PSEUDO SEA-LEVEL PRESSURE

OBSERVATIONS

-ASSIMILATING NOAA-19 HIRS/4 AND AMSU-A BRIGHTNESS

TEMPERATURE OBSERVATIONS

-ASSIMILATING RARS 1B DATA

-ASSIMILATING NOAA-18 SBUV/2 AND AURA OMI OZONE OBSERVATIONS.

MONITOR NOAA-19 AND METOP-2 GOME OZONE OBSERVATIONS

-ASSIMILATING EUMETSAT-9 ATMOSPHERIC MOTION VECTORS

-USING UNIFORM THINNING MESH FOR BRIGHTNESS TEMPERATURE DATA

-IMPROVING ASSIMILATION OF GPS RADIAL OCCULTATION /RO/ DATA

/QC... RE-TUNED OBSERVATION ERRORS/

-ADDING DRY MASS PRESSURE CONSTRAINT

-USING GODDARD MODELING AND ASSIMILATION OFFICE/EMC MERGED

CODE INCLUDING HOOKS FOR 4DVAR AND OBSERVATION SENSITIVITY

-UPDATING BACKGROUND ERROR COVARIANCE FILE

CHANGES TO THE GLOBAL FORECAST MODEL INCLUDE:

-UPGRADING EARTH SYSTEM MODELING FRAMEWORK /ESMF/ TO

VERSION 3.1.0RP2

-CHANGING OUTPUT CLOUD DEFINITION INCLUDING BOUNDARY LAYER

CLOUD AND LOW CLOUD

THE PARAMETERS WITH IMPROVED FORMULATIONS IN THE POST PROCESSOR

INCLUDE:

-VORTICITY

-ISENTROPIC POTENTIAL VORTICITY /IPV/

-DYNAMIC TROPOPAUSE FIELDS

-PLANETARY BOUNDARY LAYER /PBL/ MEAN RH

-BEST CAPE/CIN

-BEST LIFTED INDEX

-LFM 0.33-1.00 RH

THE NEW PARAMETERS FOR THE GDAS INCLUDE:

-UNFILTERED SEA LEVEL PRESSURE

THE NEW PARAMETERS FOR THE GFS PRESSURE GRIB FILES INCLUDE:

-RELATIVE HUMIDITY AT 10...30...50 AND 70 MB

-HELICITY

-ICAO HEIGHT AT THE TROPOPAUSE AND MAXIMUM WIND LEVEL

-SUNSHINE DURATION

THE NEW PARAMETERS IN THE GLOBAL FORECAST MODEL SURFACE FILES

/SFLUXGRBFXX.GRIB2/ INCLUDE:

-MAXIMUM SPECIFIC HUMIDITY

-MINIMUM SPECIFIC HUMIDITY

-DOWNWARD SOLAR RADIATION FLUX AT TOP OF ATMOSPHERE

-CLEAR SKY /CS/ UPWARD LONG WAVE RADIATION FLUX AT TOP OF

ATMOSPHERE

-CS UPWARD SOLAR RADIATION FLUX AT TOP OF ATMOSPHERE

-CS DOWNWARD LONGWAVE RADIATION FLUX AT SURFACE

-CS UPWARD SOLAR RADIATION FLUX AT SURFACE

-CS DOWNWARD SOLAR RADIATION FLUX AT SURFACE

-CS UPWARD LONG WAVE RADIATION FLUX AT SURFACE

-SNOW PHASE-CHANGE HEAT FLUX AT LAND SURFACE

-WILTING POINT AT LAND SURFACE

-FIELD CAPACITY AT LAND SURFACE

-SUNSHINE DURATION

[NorthantsSnow]

The Paralell run is even better than GFS 12z , it set's us up for a prolonged Cold Spell with very cold 850's from next Sat 12th

Are we looking at the same thing? Doesn't look very cold to me.

http://91.121.94.83/modeles/gfsp/run/gfs-1-192.png?18

It does improve later on with a solid GH but delayed like the ECM.

[I remember Atlantic 252]

best chart lol 384 parallel, shame pure fantasy, that parallel FI is unbelievable

[Cloud 10]

Irrespective of whether its going to be resolved tonight who can find the best chart!!!!!!!!

S

could there be something better on the ensembles though?

Edited December 4, 2009 by Cloud 10