Model Output discussion 1st September 00z------->

[knocker]

Latest Atlantic Tropical Depression Model Tracks (1200 UTC 09 September

 

http://derecho.math.uwm.edu/models/al082015.png

 

Edited September 9, 2015 by knocker

[Frosty.]

Very interesting Gfs 6z which shows a very unsettled spell from the weekend until around the middle of next week followed by a very settled and summery spell which lasts to the end of the run with power to add. When the unsettled spell arrives in a few days time it shows bands of heavy rain spreading north across the uk with strong winds at times but there is also some drier and sunny spells with temps still well up to average except under the wind and rain when it will be cool but then the jet is pushed away north with an anticyclone building in and becoming warm or very warm for the time of year.

[phil nw.]

Michael Ventrice â€@MJVentrice 14m14 minutes ago

ECMWF EPS showing strong indications for a big wind storm across much of the U.K. next week.

Indeed Knocker and it all starts over this weekend with the High to the east finally giving way as the Atlantic trough digs south east.

The fax for Saturday shows the breakdown to low pressure well underway.

 

Looking at the GFS jetstream forecast reminds us that Autumn is upon us as it fires up across the UK from the weekend and into next week.

 

so quite a change approaching with wind and rain at times for many of us over the next week or so.A totally different period to come compared to the benign conditions we are seeing currently.

[johnholmes]

Latest Atlantic Tropical Depression Model Tracks (1200 UTC 09 September

 

http://derecho.math.uwm.edu/models/al082015.png

no doubt this will cause some issues with all model outputs. When these get into the North Atlantic injecting huge amounts of moisture no model copes very well with them. This is to be expected as it is the introduction of moisture into forecasts that bedevils any forecast.Note that the anomaly charts have no sign of it, although I have been paying the close attention I normally do over the past 48-72 hours.

 

output below from NOAA control centre

The depression has been meandering this morning and the currentmotion estimate is an east-southeastward drift, or 120/3 kt.  Overthe next couple of days, a mid-level high is forecast to build tothe east and northeast of the tropical cyclone while a shortwavetrough moves into the northeastern United States.  This shouldresult in a northward motion at an increasing forward speedbeginning within 12 hours.  After 48 hours, the system should turnto the right and move within the mid-latitude westerlies.  Theofficial track forecast is east of the previous one, but in goodagreement with the latest dynamical model consensus.  Analternative scenario, shown by the GFS, is for the system to becomeabsorbed by an extratropical cyclone centered near New England in acouple of days.FORECAST POSITIONS AND MAX WINDSINIT  09/1500Z 30.7N  60.8W   30 KT  35 MPH 12H  10/0000Z 31.4N  61.0W   35 KT  40 MPH 24H  10/1200Z 33.0N  61.0W   40 KT  45 MPH 36H  11/0000Z 35.5N  61.0W   45 KT  50 MPH 48H  11/1200Z 38.8N  60.2W   50 KT  60 MPH 72H  12/1200Z 46.0N  54.0W   50 KT  60 MPH...POST-TROP/EXTRATROP 96H  13/1200Z 48.0N  42.0W   40 KT  45 MPH...POST-TROP/EXTRATROP120H  14/1200Z 48.0N  19.0W   35 KT  40 MPH...POST-TROP/EXTRATROP

Edited September 9, 2015 by johnholmes

[knocker]

Latest from Jeff Masters

 

 

Tropical Depression Eight spun into life on Wednesday morning in the waters a few hundred miles east-southeast of Bermuda, and appears poised to become Tropical Storm Henri by Thursday. TD 8 is under high wind shear of 20 knots, which is inhibiting development, but ocean waters are warm, near 28.5°C (83°F). The 8 am EDT Wednesday run of the SHIPS model predicted that by Thursday, TD 8 should find moderate wind shear of 5 - 15 knots and a much moister atmosphere, which should allow it to become a tropical storm. By Friday afternoon, TD 8 will move northwards across the warm waters of the Gulf Stream, and encounter very cold waters near 23°C (73°F), which should cause a rapid transition to an extratropical storm. TD 8 will likely pass over or near southeast Newfoundland, Canada on Saturday morning.

 

http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=3106

[Frosty.]

Just to add to my earlier post regarding the Gfs 6z op run showing a return of warm anticyclonic conditions from later next week, there is no indication of that occurring on the latest met office update which is for a generally unsettled pattern to persist, especially in the west / southwest but at least sheltered parts of the east / northeast are expected to have some fine and pleasantly warm days mixed in and looking further ahead there is a suggestion that high pressure could form to the northeast bringing fine weather to the east and north during late Sept / early Oct so it's certainly no washout we are looking at, just normal September weather.

[Frosty.]

Well this is getting interesting, since there was no support from the met office for the 6z op anticyclonic FI I was expecting the 12z to be generally more unsettled for longer but once again, the gfs is showing high pressure building in towards the end of next week with increasing warmth and settled weather for many parts of the UK....so, the upcoming unsettled spell may not last more than 5/6 days with a return to the current benign conditions soon after mid month.

Edited September 9, 2015 by Frosty.

[Singularity]

 

This cluster is composed of 20% of the 12z GEFS and appears to represent the scenario in which a vigorous low races across England from the southwest without merging with the broader scale Atlantic trough. It's the most threatening in terms of high wind gusts for the country, and among the wettest scenarios for England and Wales.

 

 

This cluster has 15% of the GEFS and is similar to the 12z ECM op, as the tropical remnants merge with the trough to create a large, deep low that focuses the rain and high wind gusts across the western half of the UK, the coasts getting hit hardest.

 

 

This is the largest cluster, with 40% of the GEFS, and shows little appetite to develop a nasty low in the vicinity of the UK. I didn't check this morning but I suspect that this cluster was smaller back then, with an overall move toward the tropical remnants heading too far south to engage with the jet stream and bomb out.

[William of Walworth]

Personally I'm hoping/hopecasting that those 6z and 12Z GFS runs that Frosty has been discussing above (albeit any optimism is strictly FI-based!) do come to fruition in some form for after next week.

 

But I'm very sceptical, because several of the other latest models contradict much if any idea of another settled/summerlike spell like that for later this month.

 

Still, sceptism about FI should apply equally IMO,  to writing off the whole of September yet, or to assumptions that next week's almost certainly very unsettled prospects will inevitably continue throughout the month. 

 

As we know, storms/hurricanes, or the ex-versions, can throw a few spanners in the works at all kinds of forecasts.

[William of Walworth]

And thanks to Singularity for that nicely balanced and clearly explained intepretation of the 12z GEFS charts, just above.

[knocker]

A few days break is not out of the question as the anomalies have been hinting at break (not a settled summer like break) around day nine/ten with the upper trough retreating for a while.

A snapshot look at the GFS Atlantic analysis next week with the low that has formed just to the south west. Purely out of interest as much can and no doubt will change in the interim.

http://www.atmos.albany.edu/student/abentley/realtime/atlantic.php

 

[Summer Sun]

Well this is getting interesting, since there was no support from the met office for the 6z op anticyclonic FI I was expecting the 12z to be generally more unsettled for longer but once again, the gfs is showing high pressure building in towards the end of next week with increasing warmth and settled weather for many parts of the UK....so, the upcoming unsettled spell may not last more than 5/6 days with a return to the current benign conditions soon after mid month.

 

ECM hinting at this too

 

[Frosty.]

Just as the Gfs 6z/12z ops showed high pressure making a comeback towards the end of next week, the Ecm 12z op also shows pressure rising later in the run so there are signs it may become warm and settled again, at least for the south and east just after mid month but one thing we can be sure of is we are in for a big change from the current very pleasant conditions from Saturday with bands of rain pushing northeastwards across the uk interspersed with brighter and showery conditions and also a risk of strong winds or even gales at times. Temperature wise, cool under the persistent rain but otherwise, pleasant enough with potential for rather warm conditions if we get a southerly flow for a time next week as this run shows. So...yes it's soon going to become unsettled but perhaps not for too long.

P.S...Gavin beat me to it

Edited September 9, 2015 by Frosty.

[legritter]

Very interesting Gfs 6z which shows a very unsettled spell from the weekend until around the middle of next week followed by a very settled and summery spell which lasts to the end of the run with power to add. When the unsettled spell arrives in a few days time it shows bands of heavy rain spreading north across the uk with strong winds at times but there is also some drier and sunny spells with temps still well up to average except under the wind and rain when it will be cool but then the jet is pushed away north with an anticyclone building in and becoming warm or very warm for the time of year.

Always great to see Frostys charts ,certainly some interesting weather on the horizon and plenty for us to get our teeth into .

Atlantic certainly kicking off but longer range at this point will be hard as many models struggle with many possibilitys especially any placing of high pressure ,so lets enjoy the next couple of days for those not working ,cheers .

[Singularity]

Some of the long-range model guidance is suggesting that blocking highs over Scandinavia could be a common feature during the second half of this month and a large part of October.

 

ECM's output for 10 days from now ties in with that nicely, but GFS has the jet stream proving too energetic and running over the block, resulting in the high being pushed south until it's E of the UK rather than NE. That brings a southeasterly flow with some very warm air for a time that lifts temperatures into the mid-20's for a couple of days.

 

A Scandi High offers less in the way of warmth, but could do a better job fending off the Atlantic storms. Unless of course the jet undercuts the high or the lows grind to a halt just as they begin to influence our weather, in which case you have slow moving areas of rain to contend with.

 

 

As usual, the reality is most likely to be a combination of these things, with the exact distribution depending on the strength of the Atlantic jet. Here's hoping that it isn't getting a boost this season - I've been really enjoying the usability of the recent dry weather and it'll be a shame to lose it Friday night.

[Singularity]

Briefly on the rain potential next week, that currently looks to be highest in association with a shallow low running up against high pressure across Europe on Wednesday, following Tuesday's potential windstorm. The alignment of the flow will make a big difference to the totals though, with a more SW-NE alignment as per GFS reducing the risk of a frontal boundary 'trailing' across part of the UK to deliver an extended spell of often heavy, sometimes torrential precipitation, when compared with something closer to S-N such as ECM has come up with tonight.

 

I still think Tuesday's event could produce some very heavy rainfall, but the speed at which the low looks likely to move is probably going to keep the totals from being excessive. Perhaps 20-30mm generally?

 

There's also every chance that Wednesday's threat does a vanishing act, as it wasn't there at all on the GFS 06z operational run, for example.

 

 

Shorter term, Sunday's low seems to be causing the models a lot of headaches. The large range of solutions and lack of severe outcomes within that range is the reason for my looking past it for the time being. They say ignorance is bliss... 

[knocker]

Both the anomalies tonight have the trough retreating but no great build up of positive heights in the vicinity of the UK and the the ridge remains over eastern Scandinavia. This scenario remains in the ext period. Thus a return to low pressure around Iceland and a zonal westerly.

http://www.tropicaltidbits.com/

Edited September 9, 2015 by knocker

[Summer Sun]

Looking at ECM whilst nowhere is immune from some rain next week it does look like the far west and south west could take the brunt of it and some strong winds at times as well further east should see the best chance of seeing something drier and may be quite warm and humid at times

 

 

Then towards next weekend like last night ECM offers a hint of high pressure trying to build though the further north west you are you could remain more prone to unsettled conditions continuing

 

 

How much we can believe ECM at this stage remains open to question

 

UKMO at t144 is quite a bit different to ECM

 

[Gibby]

APOLOGIES FOR THE BROKEN LINKS YESTERDAY BUT HERE IS MY LATEST ANALYSIS USING DATA SUPPLIED BY THE NWP OUTPUT COVERING 5 OF THE WORLDS MOST POWERFUL WEATHER COMPUTERS ISSUED AT 09:00 ON THURSDAY SEP 10TH 2015

 

THE CURRENT GENERAL SITUATION High pressure will continue to drift slowly away NE into Scandinavia over the next 24-48hrs with an ESE flow developing across the UK and Low pressure and troughs moving up into the SW later tomorrow.

 

http://www.wetterzentrale.de/pics/Rtavn001.gif

 

MODELS-2 WEEK HEADLINE Becoming unsettled and often windy with rain or showers at times.

 

THE GFS JET STREAM FORECAST The GFS Jet Stream Forecast shows the flow ridged well to the North of the UK currently but over the coming days it is scheduled to realign to the South of the UK at the same time as strengthening markedly. It then returns on a NE'ly course across the Uk for much of next week before slackening somewhat through Week 2 for a time but the axis of it never moving far enough away to the NW to eliminate the UK being under the influence of Atlantic Low pressure.

 

http://www.netweather.tv/index.cgi?action=jetstream

 

GFS OPERATIONAL The GFS Operational Run today shows a deteriorating weather pattern across the UK as Low pressure moves up from the SW late tomorrow and through the weekend and persists in one shape or form over the UK for the following 10 days or so. This will bring spells of strong winds and rain interspersed with showery interludes and temperatures no better than average. It takes until Day 12 to obtain a ridge which would promise the South a temporary dry interlude for a couple of days before Atlantic Low pressure returns by the end of the period.

 

http://www.wetterzentrale.de/pics/Rtavn1441.gif

 

http://www.wetterzentrale.de/pics/Rtavn3841.gif

 

THE GFS CONTROL The theme of the GFS Control Run this morning is very similar over Week 1 but is rather kinder in Week 2 as more influence of higher pressure to the SE keeps the rain more concentrated towards the North and West in the second week with the drier weather extending to other areas too at the end of the period as High pressure crosses England and Wales from the SW.

 

THE GFS CLUSTERS(14 Days) The GFS Clusters this morning show 45% of members with Low pressure to the West in 14 days time with rain at times especially in the West. The remaining 55% of members show a variety of options ranging through High pressure to the South (25%) High pressure to the NE with 'Col' conditions across the UK (25%) and 5% with a rasping Northerly with a deep Low over Scandinavia.

 

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=euro&MODELL=gefs&MODELLTYP=2&BASE=-&VAR=cpre&HH=372&ZOOM=0&ARCHIV=0&RES=0&WMO=&PERIOD=

 

UKMO UKMO today shows a cocktail of Low pressure areas revolving around the UK through next week in very unstable, unsettled and often windy weather with temperatures near average.

 

http://www.wetterzentrale.de/pics/Rukm1441.gif

 

THE FAX CHARTS The Fax Charts this morning show Low pressure taking control of the weather across the UK from the start of the weekend with troughs crossing all areas from the SW and being reinforced by more early next week when windy weather is shown to become a feature too.

 

http://www.weathercharts.org/ukmomslp.htm#t120

.

GEM GEM today shows the unsettled weather too beginning tomorrow evening in the SW and extending to all areas soon afterwards. The rest of the period is shown to be unsettled and windy with heavy rain at times especially in the West while the SE may see some reduction in rainfall later next week as High pressure brushes by over the near continent setting up warm and humid conditions for a time.

 

http://www.wetterzentrale.de/pics/Rgem2401.gif

 

NAVGEM NAVGEM looks very unsettled this morning as Low pressure moves in from the SW and makes the UK it's resting place for much of next week with rain and showers for all in sometimes strong winds and average temperatures.

 

http://www.wetterzentrale.de/pics/Rnvg1681.gif

 

ECM ECM this morning looks very similar to the majority of the output this morning bringing deep Low pressure areas up from the SW and across all areas over the next week. A lot of rainfall is possible in places and some for all though later next week could see drier and humid conditions affect the East and SE for a time as the heaviest rain remains across the West and NW.

 

http://www.wetterzentrale.de/pics/Recm2401.gif

 

ECM 10 DAY MEAN The ECM 10 Day Mean Chart  from last night shows a slightly better prospect as Low pressure appears to have retreated further to the NW in the preceding days enabling drier weather to affect the South and East at times while the North and West maintains the more unsettled theme with rain at times.

 

http://www.wetterzentrale.de/pics/Reem2401.gif

 

NOTABLE TREND CHANGES FROM PREVIOUS RUNS The models maintain their theme of High pressure migrating East away from the UK later next week with a return to more unsettled Atlantic winds thereafter. It also indicates that a temporary better period of weather could affect the SE and East late next week.

 

31 DAY HISTORICAL VERIFICATION STATS FOR GFS, UKMO & ECM The Verification Statistics of GFS, UKMO and ECM show at 24 hours ECM leads UKMO at 99.3 pts to UKMO's 99.2 pts with GFS coming in third at 99.2 pts.  At 3 days ECM and UKMO are at 95.9 pts  while GFS lags behind at 95.0 pts. At 5 days UKMO is king at 85.1 pts followed by ECM at 84.7 and GFS at 82.1 pts. Then at 8 Days ECM still leads at 58.6 pts over GFS's 50.2 pts. Finally at Day 10 ECM leads GFS at 38.3 pts to 33.9 pts from GFS.

 

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day1_PMSL_MSL_G2NHX.png

 

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day3_PMSL_MSL_G2NHX.png

 

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day5_PMSL_MSL_G2NHX.png

 

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day8_PMSL_MSL_G2NHX.png

 

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day10_PMSL_MSL_G2NHX.prig

MY THOUGHTS We are staring down the barrel of a marked unsettled and eventually windy period of early Autumn weather as the High pressure of this week becomes a distant memory by Saturday. The SW looks first to see this change with some rain marching in later tomorrow and over the weekend this extends North and East to all areas followed by brighter and more showery conditions for a time. It's the second phase of rain later Sunday and through next week which looks moreominous as this could be accompanied by strong winds and gales in places as a depression deepens as it moves North over the UK on Monday. This sets up a complex system of Low pressure over and around the UK with further spells of rain and showers along with blustery winds throughout the rest of next week. In amongst all this gloom is hope of a better period of weather across the SE and East late next week and the second weekend as High pressure over the near continent could ward off the worst of the Low pressure out to the West and NW and send some warm and humid conditions up across the South and East for a while. The charts showing this are marginal though and in any event it hints that Low pressure would return again to all after a few days to end the period unsettled for all with further rain. So it's basically make the most of this week's fine weather which in itself has been something of a disappointment for many because from saturday onward it will either be raining or rain will never be far away with strong winds to boot at times next week too. Amounts of rain do look greater than any charts I have seen for some considerable while and while widespread problems do not seem likely the water table could become quite high by the end of next week if the Low pressure areas are as persistent and active as some charts show today, this most likely in the West and SW.

 

BEST CHART OF THE DAY 00z RUN

 

http://www.wetterzentrale.de/pics/Rtavn001.gif

 

In selecting the best Chart of the Day there is a measure of how poor conditions will be at times over the next few weeks as the best chart I can find is the current midnight last night one showing High pressure warding off an Atlantic attack for now in a warm SE feed and dry weather for all.

 

WORSE CHART OF THE DAY  00z RUN

 

http://www.wetterzentrale.de/pics/Recm1201.gif

 

For the worst chart of the day I could of selected quite a few but opted for this one from ECM at Day 5 with the UK engulfed by active Low pressure with the one to the West affecting the UK in the days that follow. This chart is notable for me as it offers no easy way out of unsettled weather over the UK in the following days.

 

Next update from 09:00 Friday Sep 11th 2015

[Singularity]

Another set of runs, and no closer to knowing how the ex-tropical low will behave early next week.

 

Key differences between the operational runs are already evident as early as +96 hours. See how GFS (first image below) has a small low SW of Greenland that's having nothing to do with the remnants of TS Hilda moving north of the Azores (the vague 'sausage' of lower pressure west of the UK trough). Yet ECM (second image below) has the two lows interacting, with their combination resulting in a powerful low southwest of the UK 48 hours later. 

 

 

Even the GFS 18z operational, which also had a powerful low to the southwest, took 24 hours longer to produce it, as it was the result of disturbances combining just west of Iberia.

 

The results were quite similar though, despite the differences of timing (see below images, GFS first, ECM second). In both cases, the import of warm (even very warm) air into the UK combined with rapidly falling pressure suggests a recipe for some severe weather in the form of heavy rain (with convective features) and strong wind gusts.

 

 

Relative to this, the GFS 00z operational is very tame, the only real trouble being caused by some trailing frontal boundaries in the manner warned about last night. 

 

I was going to look at the ensemble clusters again now, but my PC is forcing a restart with no option to postpone it... how rude! 

[Tamara]

https://forum.netweather.tv/topic/83901-model-output-discussion-1st-september-00z/?view=findpost&p=3255855

 

A very pleasant end to what has been a much welcomed increasingly pleasant week

 

Thereafter, progress largely still on course to follow the summary outlined in the previous post - albeit the nearer term unsettled phase augmented thanks (or no thanks!) to extra energy supplied from ex tropical activity

 

http://modeles.meteociel.fr/modeles/gens/runs/2015091006/gens-21-1-120.png.

 

http://www.meteociel.fr/modeles/ecmwf/runs/2015091000/EDM1-120.GIF?10-12

 

A weak MJO related Maritime signal overlain with the dominant Nino Pacific pattern supports continued higher relative angular momentum and will help maintain high pressure to our east right through to the end of next week and beyond. Our fortunes however, at border control, will continue to be dominated as to how the upper trough ebbs and flows, at first still close to our west and NW

 

http://modeles.meteociel.fr/modeles/gens/runs/2015091006/gens-21-1-162.png

 

http://www.meteociel.fr/modeles/ecmwf/runs/2015091000/EDM1-144.GIF?10-12

 

Putting aside usual intra day model operational output chopping and changing, a definite trend has appeared as suggested might occur in in the previous post, towards the backing of the upper trough late next week just a fraction west and allowing pressure to try and rise again towards the south east and east of the UK

 

http://modeles.meteociel.fr/modeles/gens/runs/2015091006/gens-21-1-204.png

 

http://www.meteociel.fr/modeles/ecmwf/runs/2015091000/EDM1-216.GIF?10-12

 

http://modeles.meteociel.fr/modeles/gens/gem/run/gens-21-1-240.png

 

This might be enough to allow some improvement, and with luck some warmth, at least for a time, to come up from the south to eastern and, just maybe, some central areas to follow a widespread unsettled, blustery and changeable weather sequence as dictated by the cyclonic phase through to at least mid week next week

 

In this respect, the ex tropical activity should assist the heights over NW Europe through pumping northwards a good supply of warm air advection on the eastern flank of the lows

 

Whilst the outlook from this weekend looks distinctly rather unpalatable for at the least, a few days, and most especially further west throughout the week, there certainly remains room for the potential window of improvement further south and east later next week/weekend to gain a little further substance in future output - even if it is only for a time

 

NAEFS 0z Day 10 H500 anomalies

 

http://modeles.meteociel.fr/modeles/gens/naefs/run/naefs-0-0-240.png?0

 

[Frosty.]

The Gfs 6z op turns into a very unsettled run with bouts of strong winds and heavy rain interspersed with sunshine and showers, temperatures on the cool side under persistent rain but well up to average and feeling pleasantly warm in the sunny spells. Low pressure dominates the run either slap bang on top of the UK as per early next week or just to the west as shown later next week. The message from the models so far today is prepare for plenty of wind and rain during the next few weeks.

The latest met office update is very unsettled too with periods of rain and strong winds, especially in the west with the best of any drier, brighter and warmer spells favouring sheltered eastern / south-eastern areas, it's a changeable outlook at best but generally unsettled, especially through next week.

Edited September 10, 2015 by Frosty.

[knocker]

The latest on Henri

http://derecho.math.uwm.edu/models/al082015.png

 

[Polar Maritime]

The 6z GFS continues to show an unsettled Westerly flow next week as we head into the 2nd half of September, With bouts of wind and rain crossing the country off the Atlantic. There could be some large rainfall amounts in some areas with gales as a complicated area of Lows slowly spiral across/over the Uk stalling and bumping into the block to our East.

 

So plenty to keep tabs on reg detail as we head towards the weekend on how the models handle these systems.  

Edited September 10, 2015 by Polar Maritime

[johnholmes]

The latest on Henri

http://derecho.math.uwm.edu/models/al082015.png

 

and the latest from NOAA on its predicted track along with various other elements of their forecast

http://www.nhc.noaa.gov/refresh/graphics_at3+shtml/083818.shtml?5-daynl#contents