Model Output Discussion October 2012

[A Winter's Tale]

Evening all.

A wet night is on the cards south of the Midlands. Largely clear across northern Ireland and Ireland tonight with clear skies, a little more overcast at times in parts of Scotland and Northern Ireland with a few showers in western and northern areas and temperatures on the whole should drop to somewhere between 6-10C tonight. Saturday should be a day of sunny spells for much of the British Isles although parts of Ireland and northern and western Scotland could see increased cover and showers. Maximum temperatures 12-15C. Saturday night is likely to be a cold one with lows of 5-9C in towns and cities and should be close to freezing in a few spots in highland Scotland. A dry and calm night too with plenty of clear spells.

Sunday once more is currently looking like anothe day of sunny spells for much of the British Isles. There could be more cloud cover and the threat of rain in the south of Ireland as a front from the SW nears. Maximum temperatures should be around 12-15C. Ireland, Wales and western and southern parts of England should have an overcast night with rain in southern parts of Ireland and south western parts of England as the front moves furthern north east but in eastern England and much of Scotland a clear night looks likely and another cold one too with lows in towns and cities at 5-9C and closer to freezing in rural areas; elsewhere a milder night with lows of 9-12C.

On Monday, there should be some fragmented areas of rain across southern England and Ireland an overcast day for most other than the majority of Scotland where there should be some fine autumn sunshine. Maximum temperatures 11-14C. Most of the rain on Monday night should be in the west over much of Ireland and the Irish Sea and a largely overcast night for England and Wales other than the north sea coastal settlements and much of Scotland should have a clear night away from the SW. Minimum temperatures at the moment look like being somewhere in the range of 7-13C in cities.

Much of the western side of the British Isles should have a wet day on Tuesday although southern Ireland and the far NW of Scotland may remain dry. Largely overcast for much of the British Isles other than a few clear patches in some areas. Maximum temperatures 11-15C. Some coastal parts of western Ireland and central England could be have clear night skies at times on Tuesday night as rain is currently expected to be over central and eastern Scotland and further south along the north sea coast of England. Minimum temperatures 7-14C.

[summer blizzard]

http://dd.weatheroffice.ec.gc.ca/bulletins/alphanumeric/20121002/NO/CWAO/17/NOCN03_CWAO_021644___00044

GEM has seen an upgrade.

[Cloud 10]

http://dd.weatheroff..._021644___00044

GEM has seen an upgrade.

It will be interesting to see if the GEM improves its performance after this upgrade,as it has not fared

very well in the "how did the models do" thread.

[SMU]

BLOCK CITY ARIZONA.

S

[Gibby]

Good evening. Here's a look at the rather complex outlook from the 12zs from GFS, UKMO and ECM.

All models show a High pressure area will sink slowly ESE across Scotland and the NE by tomorrow. A slow moving trough near to Southern England will give a wet night here before it moves steadily away South into Northern France tomorrow. The rest of the weekend looks fine as the High maintains its grip over the East of Britain. By Sunday night Low pressure to the SW pushes a trough slowly NE into SW Britain with rain arriving overnight. Over Monday and Tuesday rain will see rain move slowly North up the Western side of the UK while many Eastern areas hang on to some dry weather although overcast conditions look more likely away from Scotland.

GFS then shows a Low pressure trough sliding in from the West and settling over the UK with rain spreading East too. the offending trough intensifies over the following days to give an increasingly cold, wet and windy outlook. FI is then governed tonight by Low pressure over or to the South of Britain with wet conditions frequently in the South while the best of the dry if chilly conditions is reserved for Northern areas as pressure remains High to the North.

The GFS Ensembles show 850's close to or trending just below the long term mean. Rain at times is shown for all locations though Northern areas are dry for several days from now.

The Jet Stream is still shown to split in a few days as the Southern portion weakens away with the Northern arm riding high North of the UK later.

UKMO for midday on thursday shows Low pressure over Iceland with a trough down over the UK delivering rain then showers as it transfers East through the day. Temperatures would fall off later in the day too as winds turn NW.

ECM has flipped again since this evening with a very unsettled picture evolving from its similar position to UKMO at 144hrs. Low pressure is shown to migrate close to Southern Britain by the end of the run with rain and showers for all, especially in the South. it is likely to feel cool too.

In Summary the pattern is far from clear even at t72hrs. The Low pressure recently programmed to cross the UK over the early days of next week has far less power tonight and it looks as though a High pressure of sorts could have a bigger say in conditions early next week, at least for Northern and Eastern areas. Things then turn very unsettled in the longer distant runs with Low pressure anchored close to the UK with more Autumn rains for all.

[Gavin Hannah]

GFS FI on the 12z going for some Scandi blocking. A feature to keep and eye out for in further runs.

[BLAST FROM THE PAST]

http://www.meteociel...H1-216.GIF?05-0

BLOCK CITY ARIZONA.

S

Both ECM and GFS going for massive northern blocking......let's see where we go from here. I for one am going for this direction. I think a very cold period [for time of year] will dig in end latter part of month and carry on into November. I think also in fairness to the models that they have had blocking 'in the picture' for a wee while.and a full blown pattern as per FI is plausible.

BFTP

Edited October 5, 2012 by BLAST FROM THE PAST

[Frosty.]

According to the Gfs 12z operational, ne europe looks like becoming very blocked with a large anticyclone, similar to the 6z but further northeast and the uk becomes locked into a very unsettled pattern with low pressure either to the south or directly over the country, a locked in pattern as atlantic high pressure ridges northeast and a trough becomes very slow moving and later next week would see a band of rain staggering slowly eastwards with some large rainfall totals and probable flooding risk, also some displaced pockets of arctic air coming into the mix as the main trough edges further east with some single digit maxima, all in all, a messy picture and unsettled for the most part with below average temps.

[bluearmy]

some very sexy winter patterns on offer this evening in operational fi. lets hope its just a taster of what we'll see in a couple of months time.

[phil nw.]

Looking at the N.Hemisphere modelling by T240hrs some rather untypical patterns for mid -Autumn with a very disrupted jet this side of the Hemisphere.

Some images to show this are GFS means anomls.ECM operational run, and 00z NAEF`s.

All suggest a similar picture with the main part of the cooling vortex towards Canada and greater heights showing to our north and east.

A little early for anything interesting for cold lovers yet but in another month or so this setup would have some looking to our east to see how close those cold uppers are.

[BLAST FROM THE PAST]

This autumn looks like it will continue the trend of the jetstream being shunted much further south than normal, very meridional. There is a chance of 'extreme' disruption of the jetstream later this month. Just some thoughts. If it does then some very cold air for time of year from the N/NE to visit our shores.

BFTP

Edited October 5, 2012 by BLAST FROM THE PAST

[Cloud 10]

Both ECM and GFS going for massive northern blocking......let's see where we go from here. I for one am going for this direction. I think a very cold period [for time of year] will dig in end latter part of month and carry on into November. I think also in fairness to the models that they have had blocking 'in the picture' for a wee while.and a full blown pattern as per FI is plausible.

BFTP

The 12z CFS seems to fit with your thoughts.

[syed2878]

hi people noaa's model discussions from 5TH october.

PRELIMINARY EXTENDED FORECAST DISCUSSION.

VALID 12Z TUE OCT 09 2012 - 12Z FRI OCT 12 2012

GENERAL FLOW PATTERN

==================================

UPSTREAM PACIFIC FLOW IS EXPECTED TO WEAKEN THE REX BLOCK PATTERN

IN PLACE OVER THE ERN PAC THRU THE SHORT RANGE TIME FRAME... WITH

THE CLOSED LOW JUST OFF THE CA COAST DRIFTING TOWARD THE SWRN

CONUS AND THE STEADILY WEAKENING NERN PAC RIDGE EVENTUALLY

BUILDING TOWARD EXTREME WRN CANADA. BY DAY 7 FRI THERE SOME

INDICATIONS TOWARD A SPLIT FLOW CONFIGURATION NEAR THE WEST COAST

AS TROFFING AMPLIFIES OVER AND TO THE S OF THE BERING SEA.

DOWNSTREAM THERE IS BETTER THAN AVERAGE AGREEMENT WITH AN ERN NOAM

MEAN TROF CONTAINING A SERIES OF EMBEDDED SHRTWVS. THE AXIS OF

THE MEAN TROF SHOULD BEGIN TO MOVE EWD BY LATE NEXT WEEK IN

RESPONSE TO A GRADUAL INCREASE IN NERN PAC/WRN CANADA PROGRESSION

AT THAT TIME. BY D+8 TELECONNECTIONS RELATIVE TO THE CORE OF

POSITIVE ANOMALIES OVER THE NERN ATLC AND NEG ANOMALIES OVER ERN

CANADA HINT AT THE PSBL SPLIT FLOW PATTERN UPSTREAM AT THAT TIME.

MODEL DIFFERENCES/PREFERENCES

==================================

EARLY IN THE FORECAST...THE 00Z GFS GETS TO BE ON THE FASTER SIDE

OF MODEL SPREAD WITH BRINGING THE CLOSED LOW OFF THE WEST COAST

INLAND OVER CALIFORNIA MONDAY AND TUESDAY...BUT THE 06Z GFS CAME

IN A BIT SLOWER AND NOW FITS IN BETTER WITH THE REST OF MODEL

GUIDANCE. THE MOST NOTABLE DIFF ARISES LATE IN THE FORECAST

PERIOD OVER THE ERN PAC AND WRN NOAM. THE 18Z/00Z GFS RUNS ARE

MORE AGGRESSIVE THAN OTHER SOLNS IN AMPLIFYING FLOW OFF THE WEST

COAST BY DAYS 6-7 THU-FRI...AND THEY EVEN CLOSE OFF ANOTHER LOW

NEAR THE CALIFORNIA COAST BY FRIDAY MORNING. THE 06Z GFS BACKED

AWAY FROM THIS SOLUTION...BUT STILL APPEARS TO BE AN AMPLIFIED

OUTLIER COMPARED TO THE MAJORITY OF DETERMINISTIC GUIDANCE. THE

00Z GEFS MEAN/ECMWF SHOW SOMEWHAT LATER/FARTHER NWD AMPLIFICATION

OF THIS FLOW WHILE SUCH AN EVOLUTION IS NOT EVIDENT IN THE 00Z

ECMWF/CANADIAN ENSEMBLE MEANS. A BLEND AMONG THE NON-GFS GUIDANCE

APPEARS BEST FOR GUIDING THE FCST TOWARD THE EXPECTED MEAN PATTERN

BY THE END OF THE PERIOD. MEANWHILE WITHIN THE ERN NOAM MEAN TROF

THERE IS REASONABLE AGREEMENT FOR THE SERIES OF EMBEDDED

SYSTEMS... ONE TRACKING AWAY FROM SRN CANADA MON-WED FOLLOWED BY A

STRENGTHENING WAVE TRACKING FROM THE ERN GRTLKS TO N OF NEW

ENGLAND WED-THU... AND FINALLY ANOTHER SFC LOW TRACKING FROM NEAR

THE UPR GRTLKS TOWARD NEW ENGLAND THU-FRI.

FOR THE MORNING PACKAGE...GUIDANCE COMPARISONS FROM LATE IN THE

SHORT RANGE THRU EARLY MEDIUM RANGE FAVORED A 70/30 WEIGHTING OF

THE 00Z ECMWF/00Z GFS FOR FEATURES AFFECTING THE CONUS DAYS 3-4

MON-TUE. SOME GEFS/12Z ECMWF ENSEMBLE MEAN GUIDANCE WAS ADDED DAY

5 WED AS DETAIL UNCERTAINTIES BEGIN TO INCREASE...WHILE A NEARLY

EVEN BLEND OF THE 00Z ECMWF/00Z GEFS MEAN/12Z ECMWF MEAN IS

FAVORED FOR DAYS 6-7 THU-FRI TO LEAN AWAY FROM THE LOWER

CONFIDENCE GFS EVOLUTION OFF THE WEST COAST. FOR THE MORNING

UPDATE...THE 00Z GFS WAS REPLACED WITH THE 06Z GFS DUE TO ITS

BETTER HANDLING OF THE CLOSED LOW MOVING INLAND OVER CALIFORNIA

DAY 3-4. TOWARDS THE END OF THE FORECAST PERIOD...THE 12Z ECMWF

ENSEMBLE MEAN WAS REPLACED WITH THE VERY SIMILAR 00Z RUN. THESE

UPDATES RESULTED IN MINIMAL CHANGES TO THE ORIGINAL DAY 3-7

FORECAST.

RAUSCH/GERHARDT.

Last Updated: 1000 AM EDT FRI OCT 05 2012

http://www.hpc.ncep.noaa.gov/preepd/preepd.html

[AWD]

GFS 0z showing a similar evolution in FI to its previous outputs in that heights look to rise to our E/NE.

However, on this mornings output the heights have sunk SW somewhat, leaving the trough further south over Spain & us under settled and rather mild conditions for the time of year.

Doesn't last with this run however, with a westerly flow taking shape at the runs end.

[Gibby]

Good morning. Here's a look at the 00Z model outputs from GFS, UKMO and ECM.

All models are now firming up on a quieter spell of weather over the coming few days. High pressure drifts down over Scotland and the East in the next 24 hours pushing the troublesome trough of the last few days away from the South. early next week will see a weakening area of low pressure move in from the SW to SW districts while Northern and Eastern areas look like holding on to the Higher pressure area for a few more days. Through the period this would mean a fine and settled weekend for all before a spell of cloudier weather moves in from the SW early in the week with some rain and overcast skies with the border somewhere near Central Southern England to the Isle of Man. By midweek a more active zone of unsettled looks like moving in from the West on a freshening SW wind carrying a band of rain east by late Thursday/Friday followed by colder and fresher NW winds late in the day.

GFS then forms a Low pressure within this trough and slips it South of the UK in the later half of the run with the South seeing rain at times in a slack East or NE flow at the surface while Northern areas lie closest to a belt of High pressure stretching in from the Atlantic and Scandinavia. This breaks down late in the run with something of an attack from the North as High pressure breaks down over Scandinavia with the other centre receding back out into the Atlantic.

The GFS Ensembles show that the operational was a warm outlier later in the run while under the Low pressure to the South which scoops up some warm uppers. More likely is a continuation of a basically Atlantic focussed changeable pattern with the chance of rain at times in uppers which stay fairly close to the mid October average.

The Jet Stream currently blows across the Atlantic under two arms converging over the UK. This continues for a few more days before the southern arm weakens and decays away South while the Northern arm strengthens and blows way northeast towards Iceland later next week.

UKMO for midnight on Friday shows the same as last night with a sharp trough SE over Britain from low pressure over Iceland. A band of heavy rain would be moving slowly East through Britain slowly being replaced from the West by fresher and colder NW winds and showers in the day that follows.

ECM this morning looks identical to UKMO at the same time point with the trough clearing away East and leaving a showery Westerly flow over Britain as Low pressure inches in closer to Scotland. Towards the end of the run isobars open out somewhat as the Low fills and winds back West to Southwest as a weak ridge builds North through Britain at the end of the run bringing drier and brighter weather briefly.

In Summary this morning its standard Autumn fayre from the models today with a mixture of cloud and rainy spells mixed with some drier and brighter days. There are no extremes of wind and particularly high rainfall totals likely from what I can tell nor are temperatures to likely stray far from the mid October normal at the surface. There looks likely to be too much cloud for much in the way of frost or fog too so all in all pretty standard Autumn conditions for all over the coming 10-14 days.

Edited October 6, 2012 by Gibby

[IDO]

GFS 0z showing a similar evolution in FI to its previous outputs in that heights look to rise to our E/NE.

However, on this mornings output the heights have sunk SW somewhat, leaving the trough further south over Spain & us under settled and rather mild conditions for the time of year.

Doesn't last with this run however, with a westerly flow taking shape at the runs end.

The 0z GFS is a relatively mild outlier in FI:

http://www.netweathe...ensviewer;sess=

Next week has LP to our SW with HP filling in from other areas so it looks like the SW may get some more of the wet stuff early next week.

Hp for a few days for most though.

By Thursday another trough takes over for 3-4 days. Inter model and inter run support for this.

GFS then has a HP with winds from the East, so average temps there.

By T372 GFS has a strong hint (85% within ENS) the UK will be under another trough, within a NW axis. The ENS Clusters highlight this:

http://www.weatheron...=0&WMO=&PERIOD=

So a discernible pattern for cooler air sinking, giving a variable, more Autumnal feel to October this year.

Edited October 6, 2012 by i'm dreaming of...

[Frosty.]

The Gfs 00z extended ens mean is showing the scandi high influence covering the uk until near the end of the run when the high eventually slips away and low pressure moves in from the northwest, the 00z mean has changed significantly in that range since 24 hours ago. There is a lovely weekend ahead of us for most of the uk as high pressure builds, plenty of sparkling sunshine but cold overnight with a touch of frost and quite a lot of fog forming but then burning off to bring sunny afternoons, this type of weather looks like persisting for much of the coming week but the exception being the southwest with cornwall likely to have some rain later tomorrow and the southwest of the uk does look at risk of some unsettled weather early next week but for many it looks fine. The models have firmed up on a much more unsettled and rather cold spell developing over the uk by next friday and the weekend with nw'ly winds and probably even some wintryness for northern hills and mountains but thereafter it can go two ways, either the scandi high blocking or as the ecm 00z op run shows, with an atlantic ridge pushing east followed by more atlantic low pressure.

[bluearmy]

Anecdotal post but I've been paying close attention to this coming Tuesday and throughout this week (up till Thursdays gfs op runs) the operational output has been poor. however the naefs anomaly output has been consistent all week on dropping the Atlantic ridge in around the top of the Azores trough over the uk. Clearly, even at less than a week out, naefs has proved to be a far better forecasting tool than the operationals. That is quite unusual as naefs is normally the tool to use post day 8.

[johnholmes]

Thanks again for the last 3 inputs

What is of special interest to me is just how much the models changed over the last 7 days as to what would happen through Sunday?

Gone is almost any mention of rain by UK Met or any other model. When I did my forecast for this area Thursday morning the 00z GFS output was suggesting that the rain would reach here overnight Sunday with about 20mm falling before it cleared away on Monday. This had been the fairly consistent signal for a few days. From Thursday on both media forecasts from UK Met and models backed away from this to the position we have today.

This is at least the third such faulty prediction from the models, UK, GFS and ECMWF for systems approaching from the south. I do hope that UK Met and ECMWF are doing some urgent research into this problem. It has little impact for NOAA as these errors are smoothed out by the time any effect is felt in the Pacific area.

Edited October 6, 2012 by johnholmes

[IDO]

The GFS 0Z run in FI, was a milder option. GFS 06z gives us a colder variety:

http://cdn.nwstatic.co.uk/gfsimages/gfs.20121006/06/384/prectypeuktopo.png

http://cdn.nwstatic.co.uk/gfsimages/gfs.20121006/06/384/h850t850eu.png

The 06z Ensembles suggest something in-between. As it is T384, all rather academic, but maintains the overall cooler synoptics as we head towards November.

[johnholmes]

Anecdotal post but I've been paying close attention to this coming Tuesday and throughout this week (up till Thursdays gfs op runs) the operational output has been poor. however the naefs anomaly output has been consistent all week on dropping the Atlantic ridge in around the top of the Azores trough over the uk. Clearly, even at less than a week out, naefs has proved to be a far better forecasting tool than the operationals. That is quite unusual as naefs is normally the tool to use post day 8.

interesting that ba

[Summer Sun]

The Met office say the following Heading into next weekend, it will turn very unsettled and windy with rain, heavy at times for many, and a risk of gales across the north and west.

GFS shows it staying settled

This mornings ECM would produce windy conditions but no Gales away from the far north of Scotland

Edited October 6, 2012 by Summer Sun

[bluearmy]

gavin - odds on it turning wet and breezy. that gfs op run is on its own. didnt you read my earlier post about trusting op runs beyond day 6 and looking at ens output.? naefs has a tough over the uk .

[tinybill]

Both ECM and GFS going for massive northern blocking......let's see where we go from here. I for one am going for this direction. I think a very cold period [for time of year] will dig in end latter part of month and carry on into November. I think also in fairness to the models that they have had blocking 'in the picture' for a wee while.and a full blown pattern as per FI is plausible.

BFTP

i just seen deep f1 if that happens this place could go into melt down for late oct

[Summer Sun]

Quite a settled FI tonight from GFS