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The hunt for cold - Model discussion (late November)


Paul
Message added by Paul

If you're hunting for cold potential in the model output, this thread is for you. But if you'd like to look more widely at the models, please head over to the general model discussion thread.

This is a model related thread, so a general, frequent theme of the model output is a given, but it will not be strictly enforced:

  • Some topic drift, humorous responses etc are fine
  • Posts likely to lead the thread off on an entirely off topic tangent are not ok. For example (but not solely limited to): Posts entirely or mainly about Met Office, BBC or media forecasts with little or no model context, and posts solely asking for a weather forecast in a specific location.
  • Posts which start with something like 'I know this is off topic but ...' are not ok.
  • Posts which break the forum guidelines are not ok (eg trolling, troll-hunting, weather guilt tripping, overly defensive/aggressive, abusive, disrespectful to others)

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Posted
  • Location: STEVENAGE, HERTS (100M ASL)
  • Location: STEVENAGE, HERTS (100M ASL)

Surely the GFS jet stream forecast correctly ties in with where it indicates that low will go? You cant say the handling of the low on GFS is wrong because it doesn’t match the jet stream forecasts of other models ?!

Edited by Tim Bland
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Posted
  • Location: Leeds/Bradford border, 185 metres above sea level, around 600 feet
  • Location: Leeds/Bradford border, 185 metres above sea level, around 600 feet

One interesting but unnoticed thing is that the GFS has been consistent until the 6z in saying that winds do not turn to the NE until early Wednesday. The 6z (although it has the Atlantic through quicker) changed that to Tuesday. 

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Posted
  • Location: oldham
  • Location: oldham
8 minutes ago, knocker said:

Whether it is right or wrong what the 06 gfs is showing is the very strong jet running around the amplified ridge/trough axis over N. america, with storms developing across the southern states and in the baroclinic zone along the eastern seaboard where explosive cyclogenesis quite often occurs. This is also aided and abetted by SST anomalies

.gfs_uv250_nh_23.thumb.png.a6f2d14afefcc6d915251e4d566fba69.pnggfs_t850a_nh_23.thumb.png.0280939c69048eb7504ef7d14e6ea753.pnggfs_ptype_slp_noram2_23.thumb.png.3809d1c1209531fcf47c8f47c0152645.png

cdas-sflux_ssta_atl_1.thumb.png.95d498f7e3ae756c70bae6b37cf20b26.png

From the other thread @Knocker gives a good explanation for why the GFS 06z did what it did with those deep lows.

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Posted
  • Location: Wantage, Oxon
  • Weather Preferences: Hot, cold!
  • Location: Wantage, Oxon

Well as we wait for the 12s, it's very interesting times on many timescales, I've enjoyed reading the comments on the morning runs. We'll be able to watch the strat developments at our relative leisure, but the shorter term stand off is fascinating illustrated here by GFS 6z T162 and ECM 0z T168:

image.thumb.jpg.bcde61f9111ad2e4ba40989d3eab8acb.jpg

image.thumb.jpg.389f8c17e7dc6130a32859d372ca6c2d.jpg

Some have argued very plausibly that that low in the Atlantic that later pushes away the block on the GFS is unfeasible, but it has cropped up on other output so it can't completely be discounted, it's one to watch in the runs to come...ICON rolling...

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Posted
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)
4 hours ago, jules216 said:

If we isolate MJO and pretend we trust the GEFS progression of it. Then a period of +NAO would fit OK with last week before and around Christmas.

We then hopefully see a coherent passage through phases 6 and 7 between Christmas and New Year which then correlate with -NAO.

How nice if the advection of blocking happens in the same time as SSW.

image.png

Lagged+probability+of+the+NAO+index+Positive_+upper+tercile;+Negative_+low+tercile.jpg

The antecedents for the formation of next week’s Scandinavian high certainly contributed by in a large part by extra-tropical forcing of a coherent MJO wave moving through the tropical East Pacific and Atlantic towards Africa (phases 8-1). Yes, the MJO wave continues through the ‘warmer’ phases into the eastern hemisphere on the RMM plots, but the signal looks increasingly muted. Also AAM looking suppressed after its recent positive spike, which suggests westerly momentum will decline upstream for a time from its recent El Nino-esque state – with associated jet retraction over the Pacific, which may allow a meridional flow downstream over N America and into the N Atlantic - with the blocking signal maintained to our NE through mid-December.

Longer term, we look to the stratosphere, solid signals for SPV weakening and displacement towards Eurasia from wave-1 energy, aided by forecast strong Aleutian low forecast in the medium range. Also bursts of wave-2 energy (though not as robust as Wave-1). Not likely to destroy/split the SPV this side of New Year IMO, but El Nino tends to favour SSWs in winter more than La Nina, through greater poleward forcing into the stratosphere.

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Posted
  • Location: Bexhill-on-Sea, East Sussex
  • Weather Preferences: Winter Snow, extreme weather, mainly sunny mild summers though.
  • Location: Bexhill-on-Sea, East Sussex

Good news, ICON is out and has finally started to wake up and smell the coffee!

12z compares to 06z @ T156.

icon-0-156.png

icon-0-168.png

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Posted
  • Location: Frankley, Birmingham 250masl
  • Weather Preferences: the weather extremes in general but my favourites are snow & thunderstorms
  • Location: Frankley, Birmingham 250masl
1 hour ago, Iceaxecrampon said:

Ppn creeping in.....

99B37CAA-F201-4B55-8DB4-910F36CDF74E.png

I can’t almost guarantee you that will change more than my pants

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Posted
  • Location: Wantage, Oxon
  • Weather Preferences: Hot, cold!
  • Location: Wantage, Oxon

Big improvement for cold prospects on the ICON 12z, here T180:

image.thumb.jpg.95b452d1ccbfcb1b3e31d283d5e72493.jpg

Good chance of that low going under, and if it's been overblown it should be further reduced on subsequent runs, good chance anyway.

Further illustrated by the jet stream at same time, all power to the southern arm:

image.thumb.jpg.8e8c9c5620ba61842be52bc1e0494776.jpg

Cracking start to the 12s!

Edited by Mike Poole
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Posted
  • Location: Warsaw, Poland. Formerly London.
  • Weather Preferences: Four true seasons. Hot summers and cold winters.
  • Location: Warsaw, Poland. Formerly London.
1 minute ago, Mike Poole said:

Big improvement for cold prospects on the ICON 12z, here T180:

image.thumb.jpg.95b452d1ccbfcb1b3e31d283d5e72493.jpg

Good chance of that low going under, and if it's been overblown it should be further reduced on subsequent runs, good chance anyway.

The icon does just seem to toddle off on its merry way, only to rejoin the pack as the reliable time frame moves closer. 

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Posted
  • Location: Fenland Fylde.The same village as Duncan Iceglide.
  • Weather Preferences: LP - Horizontal Drizzle - Nice Blizzards
  • Location: Fenland Fylde.The same village as Duncan Iceglide.
28 minutes ago, markw2680 said:

I can’t almost guarantee you that will change more than my pants

 :oldrofl: Yes.

All about the hunt....

Not at sea level probably but maybe a nice early season covering on the Cumbrian tops.

(You were lucky last Saturday.....)

Edited by Iceaxecrampon
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Posted
  • Location: Gillingham, Kent
  • Weather Preferences: Snow, Thunderstorms,
  • Location: Gillingham, Kent

ICON more in line with UKMO/ECM in regards of the low that was a dartboard on the previous run.. surprise surprise. I suspect GFS 12z will follow suite nicely

Edited by Daniel Smith
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Posted
  • Location: Solihull, Midlands. (Formerly DRL)
  • Weather Preferences: Sunshine, thunder, hail & heavy snow
  • Location: Solihull, Midlands. (Formerly DRL)

Definitely seems to be enough support now on the 6 to 10 day 500mb mean chart from the NOAA/CPC for Scandinavian height rises to our North-East

http://www.cpc.ncep.noaa.gov/products/predictions/610day/500mb.php

CFF59101-65CC-4F1D-A54A-80026C858637.thumb.gif.dfb5369cb88b83c45c68fe87ddd3d418.gif

A cooler/chillier spell certainly on the UK’s menu, especially further East you are, with some of the the Atlantic’s energy (Low Pressure and Low heights) getting steered South into Mainland Europe. 

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

GFS looking good at T30...can't post charts; am using my phone. 

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Posted
  • Location: Fenland Fylde.The same village as Duncan Iceglide.
  • Weather Preferences: LP - Horizontal Drizzle - Nice Blizzards
  • Location: Fenland Fylde.The same village as Duncan Iceglide.
8 minutes ago, Ed Stone said:

GFS looking good at T30...can't post charts; am using my phone. 

There you go Ed.

T+30

uksnowrisk.thumb.png.e4bf8dbb3525daa235c4e65d6e6317d7.png

All quiet.

Serious Kilt movement at T+51 ??????? :blink2:

h500slp.thumb.png.13b6b617b271b0f874ee714fdd70fd0d.png

Iain

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Posted
  • Location: Wantage, Oxon
  • Weather Preferences: Hot, cold!
  • Location: Wantage, Oxon

UKMO looks to build a stronger block to me and quicker,  this is a win for those looking for a cold outlook, T120 and T144:

 

image.thumb.jpg.8e12a56d8e7fc7a01a1f40aefc93812f.jpg

image.thumb.jpg.a1f55ba951561e30747b9f51ad39404a.jpg

Initial block edging into the reliable now.

Edited by Mike Poole
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