Model Output Discussion 22/07/12 Onwards.

[Bobby]

No proper settled weather on the 06z GFS, rather unsettled all the way

+192

+264

End of the run also unsettled, notice the tropical storm/hurricane that has developed off America, heading our way?. Quite a few of the ensembles have been showing tropical storms developing in that area lately.

As JH said they could really shake things up, into what who knows. Something to keep an eye on as this is a consistent trend showing.

Edited August 23, 2012 by Barb-

[syed2878]

Well if u look at the met 30day outlook they forecasting above avrage rain and below avrage sunshine.

[Summer Sun]

Well if u look at the met 30day outlook they forecasting above avrage rain and below avrage sunshine.

They been forecasting that for about the past month now, they only picked up on last weekends hot spell with about a week to go

[Polar Maritime]

As always with ex hurricanes the models struggle with the lack of information, and are always uncertain of the final outcome untill the nearer time frame. Some interesting and erratically changing model watching over the next week.

The reliable timeframe looks unsettled and Autumnal.

[legritter]

just a quick post today as sorting out older relatives ,but iv had a very quick look at modells and data and a very interesting time weather wise coming up .the next 3 days looks nailed ,but there is something about that next low out in atlantic ,the track of which will be critical ,just got a feeling it could creep a little further south to start then move in closer . cant back it up with technical info but one to watch .in the later runs of GFS iv noticed a deepish low mid atlantic ,sometimes at that time frame iv noticed that before ,it could be on to something and perhaps a deep low is on the cards at a closer range say perhaps T 240 HRS . will look in later cheers .

[Gavin P]

Incredible differance between ECM and GFS at 240hrs;

http://www.wetterzen...cs/Recm2401.gif

http://www.wetterzen...s/Rtavn2401.png

Thats the kind of variation we often see at this time of year, probably because the models struggle modelling tropical developments?

Edited August 23, 2012 by Gavin P

[phil nw.]

Incredible differance between ECM and GFS at 240hrs;

http://www.wetterzen...cs/Recm2401.gif

http://www.wetterzen...s/Rtavn2401.png

Thats the kind of variation we often see at this time of year, probably because the models struggle modelling tropical developments?

Yes Tropical Storm Isaac appears to be the cause of the differences Gavin.

Tonights discussions on the NOAA site seem to indicate that GFS has it being picked up by the Upper level flow in the next few days moving it out into the Atlantic and thus flattening any ridging from the Azores High downstream over our side of the Atlantic.

We can see the differences in the Operations at T168hrs from the 12z run here.

Isaac showing up clearly out in the Atlantic off the E. Seaboard on the GFS but no sign of it on the ECM.

The part of the discussion by the forecaster reads.

THERE IS CONSIDERABLE DISAGREEMENT ON THE UPPER LEVEL CIRCULATION OVER THE EASTERN

CONUS, WITH THE GFS ENSEMBLE MEANS PREDICTING A SIGNIFICANT TROUGH ALONG THE

EASTERN SEABOARD, WHILE THE ECMWF ENSEMBLE MEAN PREDICTS THE TROUGH AXIS TO BE

WELL OFF THE EAST COAST. THIS IS RELATED TO DIFFERENCES IN THE PREDICTED TRACK

OF TROPICAL STORM ISAAC WHICH IS NOW SOUTH OF PUERTO RICO. THE NATIONAL

HURRICANE CENTER FORECASTS THE STORM TO BE IN THE GULF OF MEXICO OFF THE

FLORIDA COAST BY DAY 5. BEYOND THAT, MODEL SOLUTIONS DIVERGE WITH SOME, MAINLY

FROM THE GFS, PREDICTING THAT THE STORM WILL BE PICKED UP BY THE UPPER LEVEL

TROUGH AND MOVE RELATIVELY RAPIDLY TOWARDS THE EAST COAST AND OFF INTO THE

ATLANTIC. THE WEAKER EASTERN TROUGH PREDICTED BY THE ECMWF LEAVES THE STORM

BEHIND, RESULTING IN MUCH SLOWER MOVEMENT AND A MUCH MORE UNCERTAIN TRACK.

Full discussions here

http://www.cpc.ncep....day/fxus06.html

Needless to say much uncertainty beyond t144hrs at the moment.

[Guest pjl20101]

Noticed that Tuesday of next week looks less unsettled. Think that the overall message is to treat FI with caution.

[Milhouse]

Noticed that Tuesday of next week looks less unsettled. Think that the overall message is to treat FI with caution.

The GFS has had this idea for quite a while now to keep low pressure far enough away to deliver two reasonable days next Tuesday and Wednesday. The ECM seems less keen on this but it would still keep the south east mostly dry. However the NW would be affected by showers or longer spells of rain even going by the GFS.

[bluearmy]

spot the difference? one of them will be wrong. probably both of them.

[johnholmes]

Yes Tropical Storm Isaac appears to be the cause of the differences Gavin.

Tonights discussions on the NOAA site seem to indicate that GFS has it being picked up by the Upper level flow in the next few days moving it out into the Atlantic and thus flattening any ridging from the Azores High downstream over our side of the Atlantic.

We can see the differences in the Operations at T168hrs from the 12z run here.

Isaac showing up clearly out in the Atlantic off the E. Seaboard on the GFS but no sign of it on the ECM.

The part of the discussion by the forecaster reads.

THERE IS CONSIDERABLE DISAGREEMENT ON THE UPPER LEVEL CIRCULATION OVER THE EASTERN

CONUS, WITH THE GFS ENSEMBLE MEANS PREDICTING A SIGNIFICANT TROUGH ALONG THE

EASTERN SEABOARD, WHILE THE ECMWF ENSEMBLE MEAN PREDICTS THE TROUGH AXIS TO BE

WELL OFF THE EAST COAST. THIS IS RELATED TO DIFFERENCES IN THE PREDICTED TRACK

OF TROPICAL STORM ISAAC WHICH IS NOW SOUTH OF PUERTO RICO. THE NATIONAL

HURRICANE CENTER FORECASTS THE STORM TO BE IN THE GULF OF MEXICO OFF THE

FLORIDA COAST BY DAY 5. BEYOND THAT, MODEL SOLUTIONS DIVERGE WITH SOME, MAINLY

FROM THE GFS, PREDICTING THAT THE STORM WILL BE PICKED UP BY THE UPPER LEVEL

TROUGH AND MOVE RELATIVELY RAPIDLY TOWARDS THE EAST COAST AND OFF INTO THE

ATLANTIC. THE WEAKER EASTERN TROUGH PREDICTED BY THE ECMWF LEAVES THE STORM

BEHIND, RESULTING IN MUCH SLOWER MOVEMENT AND A MUCH MORE UNCERTAIN TRACK.

Full discussions here

http://www.cpc.ncep....day/fxus06.html

Needless to say much uncertainty beyond t144hrs at the moment.

It's that time of year Phil.

FI becomes even more fraught with variations thanks to the injections of tropical storms. Even without them being upgraded into hurricanes their effect can be very pronounced. So far no longer term modelling has been able to convincingly model them, or at least not often enough for forecasters to have a great deal of confidence in their projections. No doubt over the next few years this will be an area that ECMWF especially will be seeking to improve. Not so sure about NOAA as once they clear the eastern seaboard their effect downstream has disappeared by the time it is of interest again to NOAA.

[Gael_Force]

Just to correct above info - it is TS Joyce that is shown to be in the Atlantic. Isaac is modelled to move through the Gulf of Mexico with landfall anywhere from Florida panhandle to Texas/Louisiana border.

[Turnedoutniceagain]

Sunday night's looking clear-ish. Could see a seasonal drop to single figures. 'Frosts in the isolated Glens' anyone ??

[The Northern Ramper]

The ecm has brought the settled weather forward 24 hours and the GFS has somewhat backtracked towards this from last night if not fully backtracked.

[johnholmes]

The ec-gfs 500mb charts this morning have changed quite a lot from their previous predicted upper air pattern, now going pretty much full on for a sizeable ridge and it looks like its from south of west. Previous run suggested building heights in the north and one model showed it from the NW the other from the NE so uncertainty really from these models. NOAA last evening still showed an unsettled pattern with some sign of heights building west of the UK.

http://www.meteo.psu.edu/~gadomski/ECMWF_0z/hgtcomp.html

[shedhead]

For those wanting a protracted spell of fine, dry weather, just be patient. The models are going to take a little longer to settle universally on the strong SW/NE ridging, but we are getting there and charts like this should become increasingly familiar as the next few days unfold.

[Bobby]

There are signs of a ridge building into FI but the Atlantic looks to be really firing up, perhaps helped by energy being injected by tropical systems. Will the ridge hold over us or will it be squashed flat back south? The GFS ensembles show a good mix of scenarios, maybe 50/50 for a decent ridge settling things down and half going for a more squashed ridge with Atlantic systems bringing wind and rain. The ECM and GFS means seem to be in decent agreement this morning at day 10:

GEFS

ECM

NAEFS shows decent ridging from the south at day 10, but it doesn't last long, 2-3 days and we're back to

average

So rather uncertain at the moment.

One thing's for sure, in the more reliable timeframe (the next week or so) it's looking very unsettled indeed and rather Autumnal and several deep lows heading for us with plentiful rain and gales in places as well. Flooding concerns for some.

GFS precip accumulation for the next week or so

Edited August 24, 2012 by Barb-

[Frosty.]

The Gfs and Ecm 00z are more or less in agreement of a significant pressure rise from the southwest in around a week or so with high pressure building quite strongly across at least southern britain with the jet being forced further north, the north of the uk may not enjoy the settled warm weather further south but there is a chance that the high may extend further north on subsequent runs. At the same time, as others have mentioned, the tropical storm season may impact on the settled looking FI the models are currently showing so it's not in the bag yet. The coming days show an unsettled spell but with drier and brighter days, sunday is looking fine with sunny spells but it's touch and go whether bank holiday monday will be a washout, it looks like it will be in the west and north but the south and east may escape with a largely dry and fine day until late on. After monday it looks mainly unsettled, especially further north and west but then there is a fair chance of a settled and warmer spell in early september.

[Weather Boy]

There are signs of a ridge building into FI but the Atlantic looks to be really firing up, perhaps helped by energy being injected by tropical systems. Will the ridge hold over us or will it be squashed flat back south? The GFS ensembles show a good mix of scenarios, maybe 50/50 for a decent ridge settling things down and half going for a more squashed ridge with Atlantic systems bringing wind and rain. The ECM and GFS means seem to be in decent agreement this morning at day 10:

GEFS

ECM

NAEFS shows decent ridging from the south at day 10, but it doesn't last long, 2-3 days and we're back to

average

So rather uncertain at the moment.

One thing's for sure, in the more reliable timeframe (the next week or so) it's looking very unsettled indeed and rather Autumnal and several deep lows heading for us with plentiful rain and gales in places as well. Flooding concerns for some.

GFS precip accumulation for the next week or so

Good charts to post thanks (which I've deleted to avoid clutter) but I don't really think that there is particular uncertainty considering the timescale in question. Clearly unsettled from today (tonight in the east) until approx mid-next week, but thereafter none of the charts you have posted suggest an early return of LP. The 'worst' one shows average pressure, none below average pressure.

It seems to me the only real uncertainty as to the generality of the pressure pattern is the persistence or otherwise of the HP that develops next week. Only very rarely would we expect to be confident of that beyond the 10 day period ish, so that would nornally be uncertain.

[Bobby]

The GFS 06z is rather unsettled, wet and windy all the way (especially to the N and W), apart from the occassional brief ridge between lows, with the azores high squashed flat by the active Atlantic.

+192

+252

End of run

[Gavin P]

Hi all,

Here's todays model based video: (With Caveats) Warm And Dry For Start Of September?

http://gavsweathervids.com/

Has a full run-down on todays and the weekends weather, but you may want to skip that bit.

Edited August 24, 2012 by Gavin P

[Frosty.]

<p>

The GFS 06z is rather unsettled, wet and windy all the way (especially to the N and W), apart from the occassional brief ridge between lows, with the azores high squashed flat by the active Atlantic.

+192

+252

End of run

That is the problem at the moment, the models are just as unsettled as the weather but I still think a settled spell such as the gfs and ecm 00z are showing, at least for southern britain is a fair bet for early september although the 6z has sort of torpedoed that idea for now.

Edited August 24, 2012 by Frosty039

[tinybill]

well looking at the models can we call summer over its looking wet now even deep into fantasy world at the moment

http://www.meteociel.fr/modeles/gfse_cartes.php?mode=2&ech=6

[The Northern Ramper]

well looking at the models can we call summer over its looking wet now even deep into fantasy world at the moment

http://www.meteociel...hp?mode=2&ech=6

Looking at what models? The 6z GFS or the 0z GFS which are quite different, or the ECM with the higher verification stats showing it to be settling down in six days time.

[The Northern Ramper]

Met office - Thursday, showers will be mainly confined to the east, with sunny spells elsewhere. Thereafter, a more settled period looks likely with extended spells of fine, dry weather in most areas, although rain is still possible at times, mainly in the north and west.