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

[knocker]

Tonight's anomalies play around with briefly with some height rises to the SE/S with the trough a little to the west next weekend. This could suggest a synoptic analysis of WAA for a time. I say briefly because they soon revert to the trough to the NW westerly flow scenario.

http://www.tropicaltidbits.com/

 

[Tim Bland]

All mods show that Autumn is about to kick in. Monday looks thundery in the south and Weds looks stormy for all. I doubt we will see an "Indian summer" this year, I also doubted that Piers Corbyn's brother could be our next priminister though! God help us all!

[johnholmes]

Your not the only one John! Yes it will be interesting how the models toy with this feature.

 

well the next issue at 12 z, decreases it a little but still well over 1 inch for this area.

[Frosty.]

The Ecm 12z ensemble mean shows a gradual relaxation of the nationwide very unsettled spell by the end of next week as high pressure builds across the near continent with a ridge extending north across southern england. This indicates a north/south split developing with the north of the UK staying predominantly unsettled and the south becoming fine and pleasantly warm again, at least for a time.

[Singularity]

That ECM 12z operational run sure had it in for S'rn England... a nasty low at just +96 hours range, but are we to trust that model over the others?

 

 

There would probably be some 50-60mph gusts out of that, even inland. Low risk 70mph perhaps?

 

Looks like HP will get a chance to ridge in behind the resulting LP complex as it lifts out NNE, but another area of low pressure west of the UK may simply flatten that to sustain changeable westerlies... OR it could drop south and become cut-off from the Atlantic jet according to the ECM 12z operational. The change of heart from the morning run - which was very flat with the jet pattern - seems to depend on the exact timing of the Wednesday low plus a tropical storm engaging with the jet in about 9 days time. So we're talking about an outcome that could easily disappear as suddenly as it materialised. Which is a shame because I find it a lot more interesting than the idea of a standard westerly pattern with pressure highest across the south.

[Polar Maritime]

This mornings GFS take on Wednesdays Camborne Low.

Edited September 13, 2015 by Polar Maritime

[tinybill]

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

 

nasty looking weather   expecting  met warning to appear they soon eastenside  of the  uk

[johnholmes]

This mornings GFS take on Wednesdays Camborne Low.

 

rainfall total for here by then now 19-25mm down about 10mm from the predictions for yesterday.

[knocker]

Currently knocks, yes but the ens modelling brings in some new activity. It's that time of year!

 

I appreciate it's that time of year but it is a Nino year. NHC gave the latest wave 2-day and 5-day odds of development of 10% and 50%, respectively. It appears likely that this wave will curve to the north well before it can affect the Lesser Antilles Islands. This is the case according to last night's GEFS (update) before it dissipates it next weekend.

Charts weatherbell

[Gibby]

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 SUNDAY SEP 13TH 2015.

 

THE CURRENT GENERAL SITUATION Low pressure will become dominant and complex near to SW England tomorrow with cyclonic and in places strong winds across the British Isles.

 

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

 

MODELS-2 WEEK HEADLINE Becoming unsettled and often windy with rain or showers at times though perhaps drier for a time especially in the South early next week.

 

THE GFS JET STREAM FORECAST The GFS Jet Stream Forecast shows the flow well to the South of the UK blowing strongly West to East or SW to NE over France and Northern Spain keeping the UK on it's northern flank and under a trough. after a week or so the flow migrates North to Scotland at the same time as weakening with hints of it moving further NW still at the end of the period.

 

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

 

GFS OPERATIONAL The GFS Operational Run today shows a very unsettled week to come with several Low pressure areas making the UK their home over the next week, each offering their own version of wet and windy weather with some heavy and thundery rain at times, most concentrated across Southern areas with brighter more showery weather at times too. By next weekend and beyond the emphasis of wind and rain shifts towards the North as High pressure desperately tries to move into the UK from the SW. It is shown to be a painfully slow progress but by the end of the run many places look to have become dry, bright and relatively benign for a time.

 

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 copycat of the operational for the next 5-7 days with unsettled and windy weather for all with heavy rain at times. It too then shows a brief improvement over the South in just over a weeks time before unsettled weather returns from the NW as Low pressure slips SE over Britain last to leave the SE. Pressure then rises from the North and several days of benign conditions look likely before Low pressure over the Atlantic edges troughs towards SW Britain again before the end of the period.

 

THE GFS CLUSTERS(14 Days) The GFS Clusters this morning are very diverse as members offer conflicting messages ranging from wet and windy to calm and settled weather. The emphasis though is around 50/50 perhaps with a slight bias towards influence from Low pressure more than High pressure being dominant.

 

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 Low pressure well in control of the UK weather throughout this week with heavy rain and showers mixed with occasional gales likely for many at times. It does show better conditions moving across the UK next weekend though as a ridge of High pressure builds across the UK from the South.

 

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

 

THE FAX CHARTS The Fax Charts this morning show complex areas of Low pressure moving North into the South of the UK where they become slow moving before being reinforced by further centres following a similar track meaning very unsettled and often very windy weather for the UK especially over the South.

 

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

 

GEM GEM today looks very changeable through it's 10 days with very wet and windy spells across the UK over the next 5 days under complex UK based Low pressure before cool and showery NW winds ahead of a ridge lead to a better period to start the second week. It isn't long though before Low pressure, this time to the NW is shown to move SE across the UK to return unsettled and sometimes wet weather to all by midweek of the second week.

 

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

 

NAVGEM NAVGEM shows wet and windy conditions at times too throughout this week as various Low pressure areas affect the UK as they pass over. Then as with much of the other output pressure rises somewhat next weekend with a better period especially over the South under a simplified Westerly flow with some rain at times still over the North.

 

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

 

ECM ECM this morning also looks very unsettled through the working week with rain, gales and sunshine all possible as deep low pressure areas cross the South at times. then by the weekend pressure is shown to rise markedly with dry and fine weather developing for many next weekend. How long it lasts is unclear as the model shows just a tenuous hint of a continuation of this drier spell as High pressure to the NE and SW link under conflictingly falling pressure over the UK.

 

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

 

ECM 10 DAY MEAN The ECM 10 Day Mean Chart from last night shows Low pressure up to the NW and a generally Westerly flow across the UK with no doubt rain at times, heaviest towards the North and West with some drier spells in the South and East closer to High pressure to the SW and France.

 

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

 

NOTABLE TREND CHANGES FROM PREVIOUS RUNS The models are universally supportive of 5-6 days of often wet and windy weather followed by something of an improvement over next weekend with no clear pattern of any improvement lasting or not from then on.

 

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 99.4 pts to UKMO's 99.3 pts with GFS coming in third at 99.1 pts.  At 3 days ECM ties at 96.1 pts with UKMO  while GFS lags behind at 95.2 pts. At 5 days UKMO is king at 85.7 pts followed by ECM at 85.2 and GFS at 83.2 pts. Then at 8 Days ECM still leads at 59.6 pts over GFS's 50.2 pts. Finally at Day 10 ECM leads GFS at 38.9 pts to 32.9 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 Though details from run to run are sometimes quite stark in the positioning of individual Low pressure areas over the coming week the message is the same from all output in that we are all going to see several spells of rain this week mixed with brighter showery conditions. What is less clear is whether that will be accompanied by potentially gale or severe gales. The positioning of Low pressure this week will be crucial in facilitating high winds with a more Northerly aspect to their passage giving the South a real battering while if they stay over the English channel or France then high winds are more unlikely. However, whatever happens through the week there remains a strong message that things may improve for a time next weekend as all models show a ridge of High pressure at least making an unusual if temporary weekend visit to our shores with dry and benign conditions likely. Then as we look into the longer term there is also a suggestion that Low pressure will reignite up to the NW and bring back more unsettled and windy weather with rain at times in Week 2 probably most focused towards the North and West. To be honest though with so much complexity in the atmosphere from ex tropical storms over the western Atlantic details of a period of time more than a week from now become quite futile and need to be explored later this week when the worst of this week's pool of Low pressure starts to move away and a clearer indication of the extent and longevity of next weekend's improvements are better understood. So in a sentence a wet and potentially very windy period of weather at times is likely over the next 5-6 days with less volatile and more benign Autumn weather arriving next weekend and possibly lasting for a time into the second week.

 

BEST CHART OF THE DAY 00z RUN

 

http://www.wetterzentrale.de/pics/Recm1681.gif

 

In selecting the best Chart of the Day today I have gone for the Day 7 Chart from ECM with a High pressure ridge having built strongly across England and Wales over the preceding 24 hours. Though in this run the ridge weakens in the following days it offers a period of relatively dry and benign typically quiet early Autumn conditions for several days across the UK.

 

WORSE CHART OF THE DAY  00z RUN

 

http://www.wetterzentrale.de/pics/Recm961.gif

 

For the worst chart I have gone for the ECM 4 day chart for midnight on Thursday although I could of picked any model's chart at that time point to highlight what is likely to be the pinnacle of the worst weather of the week. While the Low on this chart is harmlessly crossing NE over Southern England with SW gales kept across France any deviation further to the NW of this Low's movements could result in SW gales of some magnitude across Southern Britain and more especially the South Coast which could lead to some disruption. This Low is the one to watch this week as it has the potential to become newsworthy while on the other hand it may not depending in a shift of movement to that shown above by just a 100mls or so to the NW.

 

Next update from 09:00 Monday Sep 14th 2015

[knocker]

I suspect that looking for any prolonged warmth next weekend after a grotty week will be an early indication of that pernicious winter disease straw clutching syndrome. There is brief ridging from the SW that could give a pleasant day to the south but it's a mobile situation and soon gives way to an old friend.

http://www.tropicaltidbits.com/

Edited September 13, 2015 by knocker

[Summer Sun]

After a potential lull on Tuesday, Wednesday maintains a growing trend for some heavy rain moving up from France

 

[Singularity]

I appreciate it's that time of year but it is a Nino year. NHC gave the latest wave 2-day and 5-day odds of development of 10% and 50%, respectively. It appears likely that this wave will curve to the north well before it can affect the Lesser Antilles Islands. This is the case according to last night's GEFS (update) before it dissipates it next weekend.

Charts weatherbell

 

I believe bluearmy is referring to the potential for these recurving systems to interact with the mid-latitude westerlies and bring us some interesting or at least unpredictable weather at times?

 

GFS does seem keen on having a number of tropical cyclones wandering about in the subtropics, though it may be overdoing the intensity in some cases.

 

 

- - - - - - -

 

Short term, Euro4 shows nicely the wedge of relatively warm, moist and unstable air moving up across the south from near midnight, here's the 3am position:

 

 

As the day progresses, that wedge moves north and some drier air cuts in from the west to lie across the south by mid-afternoon.

 

Consequentially, shower activity looks to kick off in the middle of the night across the south, then become more vigorous during the morning but with the strongest activity trending north. By the afternoon convection is expected to be suppressed across southern parts, though showers may manage to keep going in some guise. Meanwhile some diurnal heating of the surface looks likely across the middle third of England and Wales during the morning, with the convective activity arriving during the afternoon and potentially utilising this surface heating to kick things up a gear, with a higher risk of thunderstorms featuring cores of very heavy or torrential rain and of course some electrical activity.

 

In terms of severity, the surface low associated with the warm, moist wedge of air (it's the warm sector) does offer some storm-relative helicity (a measure of rotation potential) to convective cells, however directional wind shear looks low, meaning storms aren't likely to stick around long enough to achieve dangerous levels of organisation. There is some suggestion of the convective cells merging into some form of organised line by late afternoon, along the occluded front marking the leading edge of the warm sector, but again the risk of severe conditions is looking on the low side to me.

 

 

Things then complicate a bit going into Tuesday, as a secondary low develops on the SW flank of the main low and draws the warm sector back southwest, this then moving across the south while the remainder clears steadily away from areas further north. The result in terms of precipitation looks to be a more pronounced back-end to the warm sector crossing the far south into the early morning, while areas further north see another day of showers, though these could tend to fade out by the afternoon as the warm sector clears to the east.

 

 

Then comes Wednesday's trouble, which the models still seem to be having issues pinning down the details for, so I'll leave that alone for the time being. It does look like a real soaker of a day though.

[Gael_Force]

Late stages of GFS 06 run having great fun with tropical and ex-tropical systems: a wall of heights to north and east causes a Fujiwara ballet of two lows with nowhere to go.

 

http://www.tropicaltidbits.com/analysis/models/?model=gfs&region=atl&pkg=mslpa&runtime=2015091306&fh=174&xpos=0&ypos=275

[knocker]

I believe bluearmy is referring to the potential for these recurving systems to interact with the mid-latitude westerlies and bring us some interesting or at least unpredictable weather at times?

 

GFS does seem keen on having a number of tropical cyclones wandering about in the subtropics, though it may be overdoing the intensity in some cases.

 

 

- - - - - - -

 

What was it about my post you quoted that makes you think I didn't understand to what blue was referring? And I suspect he was also considering the affect these systems can have on the models, such as the injection of moisture into the atmosphere, but I could be wrong.

 

En passant ACE for the N. Atlantic is currently standing 45 per cent of normal (as expected) and we are still awaiting IDA.

Edited September 13, 2015 by knocker

[legritter]

Looking at all current charts and Data things look very interesting over the coming ten days or so .

One of those situations  i feel when it would only need the Dice to fall right and we could see some disturbed and Newsworthy weather over the UK .

Tomorrow very interesting and mid week we still dont know which path our Low will take and the path and pressure will make big differences in forecasting and looking further ahead ,no real clear signal i feel is being given .

But one thing i,m pretty sure on and thats the number of posters will start to rise [including myself ] its great to have this forum for those into Meteorology ,the best im sure anywhere on the internet [cheers gang   ] .

[knocker]

Worth keeping an eye.on Strong indications of a blocking ridge Alaska and a pattern change in the Atlantic on the 06z GEFS 11-15 anomaly.

http://www.tropicaltidbits.com/

Edited September 13, 2015 by knocker

[Summer Sun]

After an unsettled week UKMO shows high pressure slowly moving in just in time for the weekend

 

Edited September 13, 2015 by Summer Sun

[knocker]

The GFS 12z is still running with the tropical disturbance and this is about the position it reaches it's lowest pressure and remains. It actually disturbs the jet which ends up pushed north.

http://www.tropicaltidbits.com/

Edited September 13, 2015 by knocker

[summer blizzard]

The GFS 12z is still running with the tropical disturbance and this is about the position it reaches it's lowest pressure and remains. It actually disturbs the jet which ends up pushed north.

http://www.tropicaltidbits.com/

 

GFS has it a hurricane around day 6. GEM develops like 3 different systems. Euro this morning ignored this wave and went for the one behind. 

 

Lots of uncertainty. 

[knocker]

Oh indeed.

[Paul]

No on topic, but just wanting to let everyone know that we now have a 500 metre rain radar available for you to try

 

https://forum.netweather.tv/topic/84002-new-500-metre-rainfall-radar-first-look/

[Frosty.]

The Ecm 12z op run shows a window of largely fine weather towards the end of the week, especially further south and east next weekend which looks pleasant as the complex low which will bring all the very unsettled weather during the coming days eventually clears away to the northeast with a ridge of high pressure building into the UK from the w/sw. Then much later in the run it becomes more unsettled from the west but at least there appears to be some welcome respite from the very unsettled weather on the way, according to this run which looks very similar to the ukmo 12z by T+144 hours.

Edited September 13, 2015 by Frosty.

[ANYWEATHER]

Well Im  jumping the gun , in this tumultuous period of model watching this coming week, and looking at next weekend and ecm and gfs are painting a quiet period as a weak ridge of high pressure builds across the nation. Good news ! But will this happen?

[Singularity]

 

Important differences between GFS (top) and ECM (bottom) at just 72 hours range.

 

GFS has a slightly weaker system than recent operational runs, which crosses the far southeast, keeping the strongest winds over the near continent, where 40-50mph gusts are projected.

 

ECM sticks with a deeper low than I have seen on any of the GFS op runs, with a 980mb feature in the above chart that is tracking west of the GFS path, meaning some of the strongest winds could impact the southeast. Wind gusts could be as high as 60mph, which would cause the trees some real trouble.

 

Some very heavy rain is expected, with embedded convective elements that I doubt GFS has fully resolved.

 

 

By Friday the system is clearing away northeast... but it could linger based on the GFS 12z operational. There's no such hanging-back from the ECM version of events, though. So we could have a lot of showers or just a few - in both cases tending to fade away during the evening.

 

We then seem to be in with a good shot of seeing a ridge of high pressure for next weekend. However, it may not be enough to save the far west and/or northwest from some rain before Sunday is over and out.

 

 

Curiously, GFS has become very keen on a low sliding SE from the North Atlantic to sit across the UK by Monday next week, with great run-to-run consistency over the past 24 hours. Meanwhile ECM has been more uncertain, despite being the first model to detect the jet taking a more southerly track again after just a brief break during the weekend.

 

Beyond that, a key player could be a tropical storm or hurricane which GFS has been very keen on for a couple of days now:

 

 

That could bring all manner of results for the UK depending on its track - you can see in the chart shown how it favours a ridge to build ahead of it should it track that far west, but if it tracked further east it could head toward the low pressure over the UK, which would be... interesting.

 

Remarkably, GFS now develops the cyclone 5 days from now, yet ECM refuses to develop it at all, and has been sticking to that across all of the past few operational runs. The official NHC discussions for America are currently discounting development of this system, suggesting that GFS is off on one. The Azores Isles will be relieved if that proves to be the case!