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Model Output Discussion 18th Nov.2013-12z onwards.

phil nw.

By phil nw.
in Forecast Model Discussion

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snowangel32 Rising Star

snowangel32

Posted
  • Location: Oldbury, West midlands
  • Weather Preferences: Heavy snow, Thunder storms and lightning
  • Location: Oldbury, West midlands
Posted

Hi all can someone please explain to me a term i have heard a few times what is a cross polar flow. The models are certainly bringing drama and its not even winter.

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pip22 Accomplished

pip22

Posted
  • Location: Clayton-Le-Woods, Chorley 59m asl.
  • Weather Preferences: very cold frosty days, blizzards, very hot weather, floods, storms
  • Location: Clayton-Le-Woods, Chorley 59m asl.
Posted

I think upcoming December is gonna be a changeable month with fair share of mild and cold weather. I don't mind changeable. Posted Image  Its better than high pressure cloudy muck.

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johnholmes Maestro

johnholmes

Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks
Posted

Hi all can someone please explain to me a term i have heard a few times what is a cross polar flow. The models are certainly bringing drama and its not even winter.

 

from one side of the pole to the other

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nick sussex Maestro

nick sussex

Posted
  • Location: Eastbourne and Larnaca,Cyprus .
  • Location: Eastbourne and Larnaca,Cyprus .
Posted

The UKMO and GFS disagree on the low moving east across the USA at 144hrs, although they look similar over Europe this will effect how the pattern develops after this point.

 

I thoroughly recommend people reading the latest update from NOAA regarding the upstream pattern, this explains much of the volatility we're seeing over the USA and Canada.

 

http://www.hpc.ncep.noaa.gov/discussions/pmdepd.html

 

Its quite longwinded as theres so much going on but just pulling out a few quotes here:

 

...OVERVIEW...ARCTIC SURGE AND AMPLIFYING UPPER-LEVEL FLOW FROM THE EASTERNPACIFIC TO THE INTERMOUNTAIN WEST  WILL BE THE PREVAILING WEATHERTHEMES THIS MEDIUM RANGE PACKAGE ACROSS THE WESTERN HALF OF THECONTINENTAL UNITED STATES. IN THE EAST AND SOUTHEAST...THE MAINFORECAST CHALLENGE WILL BE TO DETERMINE THE OUTCOME IN THE WESTERNATLANTIC--OF SOUTHERN STREAM ENERGY ORIGINATING IN SOUTHERN ANDBAJA CALIFORNIA.

 

ALOFT...THE GEFS...NAEFS AND ECMWF ENSEMBLE GUIDANCE PREFER TOMAINTAIN A DEEP TROUGH AXIS OVER THE DESERT SOUTHWEST INVOF 110WTHROUGH THE END OF THIS MEDIUM RANGE PERIOD...BUT HAVE DIFFERENTSOLUTIONS AND CONCLUSIONS DOWNSTREAM WITH AN 'INITIAL SHORTWAVE'EXITING THE UPPER-LEVEL SYSTEM AS EARLY AS DAY 4 (INTO THENORTHERN HIGH PLAINS).

 

As you can see they mention that energy into the west Atlantic and also that shortwave which is the subject of disagreement between the GFS and UKMO at 144hrs, remember here that the speed of this shortwave is important as its expected to phase with another over the west Atlantic, so how quickly it gets there will impact our side of the water.

 

 

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johnholmes Maestro

johnholmes

Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks
Posted

Yes but not just any event, potentially a blizzard event dumping feet of snow. Hardly something to just dismiss offhand.

 

feet of snow, where please?

ah, I see you said potentially, so that possibly means it won't happen?

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Snowman. Accomplished

Snowman.

Posted
  • Location: Essex, Southend-On-Sea
  • Weather Preferences: Warm, bright summers and Cold, snowy winters
  • Location: Essex, Southend-On-Sea
Posted

Posted Image

 

Very close up there.

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The PIT Maestro

The PIT

Posted
  • Location: Sheffield South Yorkshire 160M Powering the Sheffield Shield
  • Weather Preferences: Any Extreme
  • Location: Sheffield South Yorkshire 160M Powering the Sheffield Shield
Posted

Big difference between GFS and UKMO at T144. Before that nothing much happening once we've got rid of today's low. GFS takes the low south of Greenland and makes it into the beastie at T144. while UKMO sticks to main low of Norway. Will be interesting what route the ECM takes.

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Mucka Maestro

Mucka

Posted
  • Location: Manchester
  • Weather Preferences: Sunny and warm in the Summer, cold and snowy in the winter, simples!
  • Location: Manchester
Posted

The 12Z GFS operational was colder than any of the ensembles at T180.

 

Posted Image

 

 

GFS 12z set very keen on flattening the pattern after a short, sharp cold snap. Just one set though and if it has the upstream pattern wrong they will not be worth much.

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nick sussex Maestro

nick sussex

Posted
  • Location: Eastbourne and Larnaca,Cyprus .
  • Location: Eastbourne and Larnaca,Cyprus .
Posted

The 12Z GFS operational was colder than any of the ensembles at T180.

 

Posted Image

The ensembles look quite underwhelming but given their lower resolution I suspect they're even more clueless over the USA and Canada than the operationals.The pattern setting up in the western USA is quite unusual.

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R.P. McMurphy Community Regular

R.P. McMurphy

Posted
  • Location: Manhattan, USA
  • Location: Manhattan, USA
Posted (edited)

In the far reaches of FI.

But this is the model thread, and we can only report on what the models show? Unless it's mild of course, then it's set in stone and isnt classed as Fi, right? Posted Image

Edited by Glenn W
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SMU Maestro

SMU

Posted
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Posted (edited)

A big issue with todays GFS is that its modelling of the PNA pattern is not very good- especially on the 12z

 

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/gfs4cyc/

 

The GFS wants to move the Midwest Low up & through any blocking VERY quickly, however as every run passes by so the PNA block ( & ridge that's thrown across the whole of Canada ) becomes Stronger-

 

The UKMO has a 1040MB high flat across Canada from the Aleutian High

http://www.meteociel.fr/ukmo/runs/2013112912/UN144-21.GIF?29-18

 

With this in place the Midwest low has nowhere to go except remain in situ -

GFS at the same time 144-

http://modeles.meteociel.fr/modeles/gfs/runs/2013112912/gfsnh-0-144.png?12

See there is no blocking- so the low ejects towards the pole.

 

 

The GFS is reknown for being

 

* To fast

* To eastward with its flow

* weak on polar blocking-

 

As a result of these tendancies- just like yesterdays 12z its game over straight away-

 

However with none of those tendancies the UKMO shows much better potential as long as we can get that sliding low angled NW/SE-

 

Interesting we are talking about this NOW - as the ECM was modelling this nearly 3 days ago-

http://www.meteociel.fr/modeles/ecmwf.php?jour=27&mois=11&annee=2013&heure=0&archive=1&mode=1&ech=72&map=1Anyone

 

Anyone questioning the ECM really need take this example yet again to see how the GFS has flopped around like a boxer on its last legs -

 

Lets see what tonights ECM brings....

 

S

Edited by chionomaniac
avoidance of swear filter tut tut!
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Methuselah Maestro

Methuselah

Posted
  • Location: Beccles, Suffolk.
  • Weather Preferences: Thunder, snow, heat, sunshine...
  • Location: Beccles, Suffolk.
  • Popular Post
Posted

I'm thinking of spending the next 3 months in the GIN corridor...Anyone care to join me!Posted Image 

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tight isobar Maestro

tight isobar

Posted
  • Location: uxbridge middlesex(- also Bampton oxfordshire
  • Weather Preferences: blizzard conditions. ice days
  • Location: uxbridge middlesex(- also Bampton oxfordshire
Posted

ECM 12z....feel this is going to be intresting,to say the least.

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terrier Seasoned

terrier

Posted
  • Location: west yorkshire
  • Weather Preferences: extreme weather
  • Location: west yorkshire
Posted

Some are saying the gfs is wrong and go with the ECM. But wasn't it the gfs that got the pattern spot on other week and trounced the ECM

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SMU Maestro

SMU

Posted
Posted

Some are saying the gfs is wrong and go with the ECM. But wasn't it the gfs that got the pattern spot on other week and trounced the ECM

 

NO.

 

The ECM did polar blocking for 2 runs & gave it up before it found the right pattern. This was to do with the path of the tropical storm.

 

The GFS goes for the zonal reset every time, that means occasionally it will seem correct when in fact its just forecasting persistence.

 

S

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Whether Idle Contributor

Whether Idle

Posted
  • Location: Dover. Kent
  • Weather Preferences: Snow, sun, thunder, storms, frosts, summer heatwaves.
  • Location: Dover. Kent
Posted

Some are saying the gfs is wrong and go with the ECM. But wasn't it the gfs that got the pattern spot on other week and trounced the ECM

 

Correct.  But that is no guide to this episode.

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R.P. McMurphy Community Regular

R.P. McMurphy

Posted
  • Location: Manhattan, USA
  • Location: Manhattan, USA
Posted (edited)

Some are saying the gfs is wrong and go with the ECM. But wasn't it the gfs that got the pattern spot on other week and trounced the ECM

 

The fact remains there isnt a single person on this forum who can be 100% sure and say the GFS is wrong, or the ECM is wrong etc.... Unless we are actually living in the Matrix and NetWeather has been infiltrated by Agent Smiths (A Boy Named Sue) who can 'jack in' to the Models.

Edited by Glenn W
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terrier Seasoned

terrier

Posted
  • Location: west yorkshire
  • Weather Preferences: extreme weather
  • Location: west yorkshire
Posted

NO. The ECM did polar blocking for 2 runs & gave it up before it found the right pattern. This was to do with the path of the tropical storm. The GFS goes for the zonal reset every time, that means occasionally it will seem correct when in fact its just forecasting persistence. S

ok Steve thank you still learning
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Summer Sun Maestro

Summer Sun

Posted
  • Location: Darlington
  • Weather Preferences: Warm dry summers
  • Location: Darlington
Posted

Once again GEM shows the coldest air moving away very quickly to be replace by milder air from the west to south west

 

Posted ImagePosted ImagePosted ImagePosted ImagePosted ImagePosted Image

 

Posted ImagePosted ImagePosted ImagePosted Image

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Methuselah Maestro

Methuselah

Posted
  • Location: Beccles, Suffolk.
  • Weather Preferences: Thunder, snow, heat, sunshine...
  • Location: Beccles, Suffolk.
Posted

Some are saying the gfs is wrong and go with the ECM. But wasn't it the gfs that got the pattern spot on other week and trounced the ECM

I think it's true to say that the ECM is marginally superior to the GFS - at least where Europe is concerned...But, IMO, that marginal superiority sometimes gets hugely exaggerated...Especially when certain folks get carried away by the 06Z.Posted Image 

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nick sussex Maestro

nick sussex

Posted
  • Location: Eastbourne and Larnaca,Cyprus .
  • Location: Eastbourne and Larnaca,Cyprus .
Posted

Some are saying the gfs is wrong and go with the ECM. But wasn't it the gfs that got the pattern spot on other week and trounced the ECM

Both models have their ups and downs, and a bias in certain set ups. NOAA are often critical of the GFS for being too fast and remember last nights 12hrs which was on another planet upstream, its slowly walked back from that but is still probably too quick. The ECM bias is to overdo Greenland ridging when its on its own picking that and overamplifying things, the GFS flattening things out and especially in its lower resolution. With time you get to know the models, they all have their distinctive personalities. The UKMO often avoids too much slating because we only see its output upto 144hrs, there is a 168hrs but for some reason the UKMO view this as top secret, apparently its under armed guard 24hrs a day in case God forbid a member of the public could actually view it!!!

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R.P. McMurphy Community Regular

R.P. McMurphy

Posted
  • Location: Manhattan, USA
  • Location: Manhattan, USA
Posted

Once again GEM shows the coldest air moving away very quickly to be replace by milder air from the west to south west

 

Posted ImagePosted ImagePosted ImagePosted ImagePosted ImagePosted Image

 

Posted ImagePosted ImagePosted ImagePosted Image

 

Where is the rest? Where it shows a full reload and any "warmer" (If you can call it that) air is removed and an attack from the NW resumes....

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