Model Output Discussion

[Eugene]

Another pleasing GFS 12Z run with HP taking over by end of the week and lasting quite a while before the usual BS collapse in extreme FI which should be taken with a truckload of salt, some nice cold foggy weather on the cards from next weekend ......Great summers charts these would make shame we havent had many like them in the past three summers.

Edited December 5, 2009 by Eugene

[Guest North Sea Snow Convection]

If the jet is angled northwards then any potential shortwave would assist the warm air advection preocess which is needed to pull the euro/uk high northwards to in turn allow a trigger low to push the cold air westwards beneath it. It becomes a problem if the jet angle is SW-NE as that prevents the high moving north and the cold air is shunted southwards away from us instead.

Edited December 5, 2009 by North Sea Snow Convection

[Mark Bayley]

GFS essembles arn't great. One or two are ok after T300 but thats about it. Best one i found after scanning through was P19

Other than that not a great GFS/GEFS tonight

UKMO looks good however the T144 charts from the UKMO are not the best in the world. Not to be dismissed though !!

I wonder what the ECM is going to come out with

Edited December 5, 2009 by mark bayley

[Glacier Point]

Huge synoptic scatter in the 12z GFS ensembles suggesting the GFS has not got a good handle on next week's evolution.

Following on from my posting yesterday, big question mark on the ridge programmed t120-t144 sticking around. Key question, which way will it go - north or south? I suspect that heights will be sufficient enough to our north to set up a battleground scenario with the cold to our east and trough trying to re-eastblish itself from west. Snow potential potentially increasing here.

[Snowstorm1]

Huge synoptic scatter in the 12z GFS ensembles suggesting the GFS has not got a good handle on next week's evolution.

Following on from my posting yesterday, big question mark on the ridge programmed t120-t144 sticking around. Key question, which way will it go - north or south? I suspect that heights will be sufficient enough to our north to set up a battleground scenario with the cold to our east and trough trying to re-eastblish itself from west. Snow potential potentially increasing here.

Thankyou Gp you have regained my faith

[Lightningboy]

GFS essembles arn't great. One or two are ok after T300 but thats about it. Best one i found after scanning through was P19

Other than that not a great GFS/GEFS tonight

UKMO looks good however the T144 charts from the UKMO are not the best in the world. Not to be dismissed though !!

I wonder what the ECM is going to come out with

They dont seem to bad at all really, Im too waiting for the ECM.

what time does the ECM update?

[reef]

The GFS 12z is the epitome of what has gone wrong with many attempts at easterlies in recent times. It also highlights the danger of a mid-latitude high, as it gradually sinks leaving us in a very Bartletty situation at the end of the run ready for christmas. As others have said, the lack of a trigger low means the flow remains slack and flabby before the inevitable fall in heights around the GIN corridor occurs giving us a few days of inversion cold and nothing more. Greece on the other hand, get another cold spell.

Unfortunately, these 'spoilers' very rarely upgrade once they have been picked out on the models.

[Mark Bayley]

They dont seem to bad at all really, Im too waiting for the ECM.

what time does the ECM update?

There not great to be honest. That short wave spoils things. Best hope for something like the UKMO. Encouraging thoughts from GP though

It starts updating around 18:00 and finishes at 19:00

http://www.meteociel...deles/ecmwf.php

Edited December 5, 2009 by mark bayley

[Lightningboy]

There not great to be honest. That short wave spoils things. Best hope for something like the UKMO. Encouraging thoughts from GP though

It starts updating around 18:00 and finishes at 19:00

http://www.meteociel...deles/ecmwf.php

ok thanks

im not the best ar understanding models i will learn.

Im going to be waiting tonights runs

[stewfox]

its clear from the ens that the GFS 12z suite has picked up a signal for there to be more energy in the atlantic jet later this week

Where does that signal come from ?

[SP1986]

I certainly dont buy the 12z's idea of an Azores Atlantic push towards the end of the run, that is, in my opinion as unlikely as a severe easterly.

However it does looks more likely that High Pressure will settled over the UK giving cold days and frosty nights, and perhaps later on leading to an inversion perhaps, so cold looks like figuring, but outside of frost hollows it probably wouldn't be anything extraordinary judging by the last few models runs (realistic timeframe)

[bluearmy]

Where does that signal come from ?

the input data it runs with. could be any number of things, but the result for our little part of nw europe is significant.

still plenty of 15% spread sypnotically in fi on the GEFS as GP alluded to.

[Guest North Sea Snow Convection]

I think if it was the other way around and the UKMO was showing what the GFS is and vice versa many would be pointing to the METO model being right and waiting for the GFS to backtrack!

There is too much uncertainty atm at this distance to call this either way and the GFS operational and ensembles chop and change so quickly - apparently showing a consensus one minute and then not the next time around. All that tells me at any rate is that the model doesn't really know the right solution to the situation. Not much change there then from the usual. Pointless really getting hung up over it every six hours (if you happen to watch it each time that is!)

How many times did the models (especially the GFS) blow hot and cold over the Dec 2005 easterly for eg?

It may or may not happen as we all wish, but no point agonising over each and every output

In the first instance I am just pleased to see an end to all this wind and rain. There is plenty of time for things to back westwards, and I think provided the cold air can make some progress into europe at least, be consolidated there, and we can get another boost to the -AO via a large warming event then next time prospects improve even further.

Edited December 5, 2009 by North Sea Snow Convection

[bluearmy]

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get used to it

its only the 5th of december - your head will be real sore by march

[Mark Bayley]

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Not very constructive... as bluearmy says your going to have a very sore head by the end of the winter

Very good post NSSC and as you say the models will flip around all over with different outcomes being show. The GFS has particular habit of doing this. What ever happens its going to become settled. So even if we don't get an easterly it will be at least cold and frosty. Far better than the dreaded south westerlies. The potential is there in the long term as well. With the -AO and hopefully another Stratospheric warming as we enter the last part of the month. I think GP said he thought one was likely around the 20th. Will have to check the thread

ECM should start coming out now, hopefully good!

http://www.meteociel...deles/ecmwf.php

Edited December 5, 2009 by mark bayley

[cooling climate]

I think we are all use to the wobbles the GFS model has at times where it will drop an

idea and then pick it up again.

Also if the model has an inherent flaw in overdoing shortwaves then this would apply to

the ensembles as well I would have thought.

The 12z ECM run should give us a better idea on weather the GFS is right or not.

[ChartViewer]

I think we are all use to the wobbles the GFS model has at times where it will drop an

idea and then pick it up again.

Also if the model has an inherent flaw in overdoing shortwaves then this would apply to

the ensembles as well I would have thought.

The 12z ECM run should give us a better idea on weather the GFS is right or not.

Totally agree...NOAA have this model as the model of consistancy and to be honest if the 12z ECM shows a wobble I suspect the GFS will come on board soon..............To be honest I think we all expect a High over UK and cold flooding down Central/Eastern Europe but we can hope

Edited December 5, 2009 by ChartViewer

[pyrotech]

I think we are all use to the wobbles the GFS model has at times where it will drop an

idea and then pick it up again.

Also if the model has an inherent flaw in overdoing shortwaves then this would apply to

the ensembles as well I would have thought.

The 12z ECM run should give us a better idea on weather the GFS is right or not.

The GFS 12z has been withdrawing the cold for last few days, The 18z and 06z bring it back.

That will probably happen again tonight, just shows the extent of forecasting this. I think the 12z is the more accurate normally but the 6z and 18z seem stuck on this cold coming. If the ECM trys to bring it in then maybe we will get lucky. In my opinion the cold into Europe is a great start anyway and allows possibilities if nothing else.

[03jtrickey]

I was wondering whether anyone could tell me what to look for when people talk of "height rises". Is there a difference between "height rises" and a rise in sea level pressure? If so, which NetWeather charts would show the height rises? Linked to this, what distinguishes a strong Greenland/Scandi block from simply having high surface pressure over these areas?

Sorry for the novice questions but it's something I've been wondering for a while.

[TEITS]

I think if it was the other way around and the UKMO was showing what the GFS is and vice versa many would be pointing to the METO model being right and waiting for the GFS to backtrack!

So very true.

The problem is we have had so many disappointments in the past that we forget that at times the models do actually upgrade. The UKMO is excellent and I personally won't be too concerned with every single GFS run.

As I said earlier today an E,ly will be a bonus and im personally satisified with a spell of HP.

[I remember Atlantic 252]

The GFS 12z has been withdrawing the cold for last few days, The 18z and 06z bring it back.

That will probably happen again tonight, just shows the extent of forecasting this. I think the 12z is the more accurate normally but the 6z and 18z seem stuck on this cold coming. If the ECM trys to bring it in then maybe we will get lucky. In my opinion the cold into Europe is a great start anyway and allows possibilities if nothing else.

12Z maybe more accurate but yesterday's 12Z was ridiculous, certainly not accurate not the FI bit, but this 12z looks realistic

sadly going by recent form, climate change etc, the GEFS control will be close to the outcome I think, but still great to have a few dry cold days

Edited December 5, 2009 by mark forster 630

[pyrotech]

12Z maybe more accurate but yesterday's 12Z was ridiculous, certainly not accurate not the FI bit, but this 12z looks realistic

Sorry was talking about Fi, been saving them for comparison with actuals when they arrive, to try to see what is best with GFS, ECM.

[TEITS]

Just found some interesting charts.

Last year I started a thread showing what the GFS was indicating for xmas. Below are the charts before xmas day and what actually happened.

http://www.wetterzentrale.de/archive/ra/2008/Rrea00120081225.gif

The point of this post is in my experience the GFS has a tendancy of underestimating blocking and over cooks LP systems.

[Thundery wintry showers]

I was wondering whether anyone could tell me what to look for when people talk of "height rises". Is there a difference between "height rises" and a rise in sea level pressure? If so, which NetWeather charts would show the height rises? Linked to this, what distinguishes a strong Greenland/Scandi block from simply having high surface pressure over these areas?

Sorry for the novice questions but it's something I've been wondering for a while.

This link may help:

The 500hPa height is simply the height above mean sea level at which the atmospheric pressure is 500 hPa (and 1 hPa = 1 millibar).

"Height rises" tend to refer to increases in the 500hPa height (shown by greens, yellows and oranges on the charts as opposed to blues and purples) rather than just increases in sea-level pressure although the two are correlated.

[Gowon]

Nogaps is looking good also.