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

[Summer Sun]

Finally some consistency starting to appear from the models all now showing high pressure over the UK at t120

 

 

And t144

 

[MR EXTREMES]

ive had a good gander at the models and to be honest it really is not that bad even the ecm at 240with residual -4 upper air across the country yes indeed dry but if it was not for the Iberian low we would be in a totally different situation.

 

and there is still room for futher developments im sticking with the ukmo in future and the other models up to t144 and even that's fi at times like this.

 

its also worth noting that the solar activity has gone through the roof so this may not be helping.

Edited November 19, 2013 by model rollercoaster

[Richie V]

Lets not forget, thats a pretty vicious area of lp for tommorow. It's going to be quite a wild ride for some.

[radiohead]

For what its worth, the latest NHC update on Melissa. Track has shifted further east.

.THERE IS A NOTABLE DISAGREEMENT IN HOW THE POST-TROPICAL REMNANT OF MELISSA INTERACTS WITH THE DEEP-LAYER TROUGH. THE GFS CONTINUES TO SHOW THE CYCLONE ROTATING AROUND THE EASTERN SIDE OF THE TROUGH OR LOW...WHILE THE ECMWF AND UKMET SHOW THE CYCLONE MOVING MORE EASTWARD IN THE WESTERLIES. THE NHC FORECAST IS ADJUSTED A LITTLE TO THE EAST OF THE PREVIOUS ONE...AND LIES CLOSE TO THE FLORIDA STATE SUPERENSEMBLE...WHICH IS IN BETWEEN THE AFOREMENTIONED SCENARIOS.

[Summer Sun]

Latest from Gibby

 

All models show a showery NW flow over the UK with a deepening Low heading SE towards NW Britain through today. This sinks further South down the North Sea and away to the South of Britain on Thursday. Spells of rain and hill snow on the highest ground will move SE tonight and tomorrow to affect all areas followed by clearer and rather cold weather with wintry showers on Thursday. These will clear away South on Friday then High pressure is shown to build across the UK with fine, cold and crisp conditions for all with widespread frost and freezing fog patches night and morning, persisting all day in places.

 

GFS then keeps High pressure in one form or another completely dominant over the UK positioned over or just to the North. There will be fine and dry weather almost through the entirety of the second half of the run with no rain at all and mostly fine conditions with just varying degrees of frost and fog problems day to day. Temperatures at the surface will be just below average under clear conditions by day but nights will be colder than average and if fog persists through the daytime then temperatures will be held very low.

 

UKMO shows High pressure positioned over Southern Britain with flat calm conditions allowing plenty of frost and fog at night and variable conditions through the day's totally dependant on whether fog clears or not.

 

GEM too just about manages to hold High pressure over the UK throughout the latter stages of it's run though pressure on the ridge across Southern Britain is squeezed from both the North and South. It would stay rather cold overall and once again the only variance from day to day would be the extent of mist, fog and frost.

 

NAVGEM is the only model this morning that holds High pressure further North over Scotland maintaining an Easterly flow across England and Wales though it would be unlikely to offer any different weather other than more breeze restricting fog formation down here.

 

ECM has also brought High pressure further South this morning but maintaining an axis and trajectory East to West across Central Britain right out to the end of the run with fine and dry conditions for all with varying amounts of frost and fog night and morning dependant on cloud cover and airflow day to day.

 

The GFS Ensembles paint a dry period through the Central portion of the output today once tomorrow's Low pressure clears away South. With Britain seeing above average uppers for a time in association with a UK based High temperatures will be close to average or below at the surface with overnight frost and fog. Should fog prove reluctant to clear then temperatures at the surface would be very cold despite these higher uppers. There are tentative signs of the High pressure giving ground to more unsettled conditions very late in the run.

 

The Jet Stream is flowing South over the UK at the moment and is setting itself up for a blocked setup in association with a UK based High late in the week. The flow is then directed well North around the High over Iceland and Northern Scandinavia next week.

 

In Summary if it's static cold and calm High pressure conditions you're after then your in luck today because virtually all models with the exception of NAVGEM show a UK based High pressure offering all the ingredients for light winds and widespread night frosts and fog patches, freezing in places with the inevitable November conundrum of it's failure to clear some days, making it very cold and miserable. Outside of fog though there would be plenty of sunshine should most of the runs verify and there looks little likelihood of any significant rain anywhere and of course this applies to anything wintry also. So a very typical late Autumn and early Winter period to come with High pressure very much in control for all.

 

http://www.norton-radstockweather.co.uk/Model-Analysis%282859336%29.htm

[MKN]

Much snowier run for many from the 06z gfs even the south east could see some... Between +36 and +48. I can't post charts as I'm on mobile though.

[tight isobar]

Slight variations on gfs 6 z...thus far!

[Weathizard]

Much snowier run for many from the 06z gfs even the south east could see some... Between +36 and +48. I can't post charts as I'm on mobile though.

-4 uppers - cold rain unfortunately, no snow for the south east, in fact I can't see anywhere in the UK apart from high ground in the north.

[Summer Sun]

-4 uppers - cold rain unfortunately, no snow for the south east, in fact I can't see anywhere in the UK apart from high ground in the north.

 

GFS hinting at possible snow for SE

 

[Weathizard]

GFS hinting at possible snow for SE

Perhaps something of a wintry sort then but looking at high res models I don't see much apart from a bit of patchy sleety rain, north & high ground certainly possible though. Good consistency from GFS so far out to T96. Edited November 19, 2013 by Weathizard

[radiohead]

-4 uppers - cold rain unfortunately, no snow for the south east, in fact I can't see anywhere in the UK apart from high ground in the north.

I've seen snow at low levels with -2 uppers, as long as the dew point is below freezing.

[ARNOTT ad]

Another early crock from ECM as per last year but UKMO was never on board and I agree with Steve Murr, we need that model on board with the ECM for confidence in stellar outcome...never mind, it is still only November. winter hasn't even started.....but I get the feeling that December is going to be a long month on here.

BFTP [/quote

It doesn't matter that the winter hasn't started etc. the Pv is cranking up and may not get similar charts again.

[Summer Sun]

I've seen snow at low levels with -2 uppers, as long as the dew point is below freezing.

 

Sea temperatures will play a big part in this spell as well they are still above normal after the hot summer and mild Autumn

[Gavin Hannah]

I wouldnt trust the GFS snow charts. They change run by run. Even within the 24 hour window.

Caught the beeb forecast and thought they were being a bit optimistic with the temps from tomorrow onwards.

On my way to glasgow this morning, saw plenty if snow covered peaks and the odd dusting by the road but dang it was cold. Car said -4 at 8:10am.

The LP will bring plenty of hill snow for Scotland with snow down to roughly 200m I reckon depending on proximity to the sea.

Elsewhere, gales, sleet and freezing rain so wrap up warm.

Edited November 19, 2013 by IBringTheHammer

[Frosty.]

The GEFS 00z mean shows the atlantic cranking up into early December with our high drifting away southeastwards and a spell of rather cold zonality eventually replacing the cold, foggy & frosty anticyclonic conditions but it's a slow erosion from the west/nw, the far northwest corner of the uk would gradually turn unsettled and windier through next week but most areas look like becoming fine and benign for at least a week before the potential change arrives. With cool / cold zonality and a jet aligned wnw / ese there is a good chance of wintry ppn for northern hills and occasionally to low levels and further south and a higher chance of upstream amplification with mid atlantic high pressure building north and much colder shots from the nw / n. I really think we have a good chance of a chilly zonal flow from slightly north of west once the anticyclonic spell ends during early / mid december. 

[legritter]

FROSTY you could squeeze a snow flake from a full blown azores high ,but i think Models are struggling at the moment .it wouldnt surprise me once the high pressure sets in it will hang around a while so the far outlook could change dramatically over say two runs .ECM is still showing some good charts and i expect plenty of changes over coming days ,as always exciting .

[shaky]

-4 uppers - cold rain unfortunately, no snow for the south east, in fact I can't see anywhere in the UK apart from high ground in the north.

minus four uppers defo cold enough especially if the flow is slack so you just never know.

[ICETAB]

NAVGEM looks interesting at T114 on the 06Z

 

[shaky]

NAVGEM looks interesting at T114 on the 06Z

thats three runs in a row now where its shown a stronger north east/easterly effect.

[Captain Shortwave]

Hmm, it's a bit of a stretch but I wonder where the GFS is going with this

It's trying to retrograde the ridge around the low, which the model handles differently to the others. Now if that could phase with the trough in the med it could be used to prop up the high a bit better than currently modelled. With very cold air going into Scandinavia and Eastern Europe, a few tweaks here and there, and the GFS easing off the energy going over the top in the latter frames, we might see something interesting develop. Just a thought and probably will be wrong, but I am quite intrigued in what the 12z GFS op will show.

[Vorticity0123]

And that's the end of the consistency regarding Melissa. Models have made a quite significant shift to the right concerning the recurve of Melissa. Most of the models currently show the system moving up toward the Iceland/Greenland area, while just 12 hours ago, a track edging more toward Nova Scotia was forecasted. This is a good example of the flip-flop of the different models.
 

 

The uncertanity is also reflected in the advisory of the NHC:

 

 

BEYOND A COUPLE OF
DAYS...THERE IS A NOTABLE DISAGREEMENT IN HOW THE POST-TROPICAL
REMNANT OF MELISSA INTERACTS WITH THE DEEP-LAYER TROUGH. THE GFS
CONTINUES TO SHOW THE CYCLONE ROTATING AROUND THE EASTERN SIDE OF
THE TROUGH OR LOW...WHILE THE ECMWF AND UKMET SHOW THE CYCLONE
MOVING MORE EASTWARD IN THE WESTERLIES.

 

For comparison: The EC shows the system moving as a seperate entity toward Spain (T96):

 

(Melissa is the 1005 hPa low a couple hundred miles southwest of Newfoundland).

 

While the GFS shows the system curving and becoming absorbed by the low pressure area just off Newfoundland. (T96):

 

(Melissa is the low pressure area weakly discernible to the right of the Newfoundland low pressure area).

 

The difference in outcome is that at T120 the EC shows a north-south block over Great Britain, while the GFS shows a more northeast-southwest oriented "blockade".

 

Concluding, The uncertanity will remain for the next few days as the models flip-flop with the track. The coming days will be an interesting period of model watching.

 

Sources:

http://www.nhc.noaa.gov/

http://www.ral.ucar.edu/guidance/realtime/plots/northatlantic/2013/al142013/

http://www.wetterzentrale.de/topkarten/fsecmeur.html

Edited November 19, 2013 by Vorticity0123

[iamgazza]

And that's the end of the consistency regarding Melissa. Models have made a quite significant shift to the right concerning the recurve of Melissa. Most of the models currently show the system moving up toward the Iceland/Greenland area, while just 12 hours ago, a track edging more toward Nova Scotia was forecasted. This is a good example of the flip-flop of the different models.

 

 

The uncertanity is also reflected in the advisory of the NHC:

 

 

For comparison: The EC shows the system moving as a seperate entity toward Spain:

(Melissa is the 1005 hPa low a couple hundred miles southwest of Newfoundland).

 

While the GFS shows the system curving and becoming absorbed by the low pressure area just off Newfoundland. (T96):

 

(Melissa is the low pressure area weakly discernible to the right of the Newfoundland low pressure area).

 

The difference in outcome is that at T120 the EC shows a north-south block over Great Britain, while the GFS shows a more northeast-southwest oriented "blockade".

 

Concluding, The uncertanity will remain for the next few days as the models flip-flop with the track. The coming days will be an interesting period of model watching.

 

Sources:

http://www.nhc.noaa.gov/

http://www.ral.ucar.edu/guidance/realtime/plots/northatlantic/2013/al142013/

http://www.wetterzentrale.de/topkarten/fsecmeur.html

Completely agree, I don't think we can be overly confident with any model runs until this feature has decided which path it will take. Small changes = big changes down the line.

[radiohead]

When it comes to tropical/subtropical cyclone tracks I'd usually bet on the ECM before the GFS.

[Frosty.]

The GFS 06z op run shows a decent spell of crisp anticyclonic weather with sunshine by day once mist / fog and overnight frost clears, temperatures continuing below average but as with the GEFS 00z mean, during FI there is a gradual erosion of the settled spell from the northwest, the northwestern corner of the uk becoming unsettled and windier with temps heading back towards average, eventually the high drifts away southeastwards into mainland europe and the atlantic fires up but as with the mean, probably a much greater emphasis on cold zonality with only short bursts of milder weather, cold enough at times for snow on northern hills but that is well into early december.

[nick sussex]

Hmm, it's a bit of a stretch but I wonder where the GFS is going with this

It's trying to retrograde the ridge around the low, which the model handles differently to the others. Now if that could phase with the trough in the med it could be used to prop up the high a bit better than currently modelled. With very cold air going into Scandinavia and Eastern Europe, a few tweaks here and there, and the GFS easing off the energy going over the top in the latter frames, we might see something interesting develop. Just a thought and probably will be wrong, but I am quite intrigued in what the 12z GFS op will show.

The problem with the GFS and also the NAVGEM is that they deal differently with the upstream low compared to the ECM/UKMO which moves east out of the ne USA, its much more amplified, the ECM has really toned down this low and is much flatter upstream.

There is no agreement on that key area upstream and also with the Melissa uncertainty its proving to be a real mess.