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

[summer blizzard]

 

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!

 

It has a 70% chance of development within 48 hours and a 90% chance within 5 days. 

 

The real question is how strong it will be.

[johnholmes]

It has a 70% chance of development within 48 hours and a 90% chance within 5 days. 

 

 

Can I ask where do you get that from please? As the post you linked to suggested NOAA do not rate it that way.

[johnholmes]

17-31mm are the two 'spot' amounts straddling me from the 12z

 

from UK Met they currently have 3 12z Wed Fax positions and depths

http://www.weathercharts.org/ukmomslp.htm#t84

The latest suggests less wind and less deep centre also a touch further SW from their first one

Edited September 13, 2015 by johnholmes

[Boro Snow]

Can I ask where do you get that from please? As the post you linked to suggested NOAA do not rate it that way.

TROPICAL WEATHER OUTLOOK

NWS NATIONAL HURRICANE CENTER MIAMI FL

200 PM EDT SUN SEP 13 2015

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

1. An area of disturbed weather associated with a broad low pressure

system located several hundred miles southwest of the Cape Verde

Islands is showing signs of organization. Environmental conditions

are conducive for development, and a tropical depression could form

during the next day or two while the system moves west-northwestward

to northwestward across the central tropical Atlantic.

* Formation chance through 48 hours...high...70 percent

* Formation chance through 5 days...high...90 percent

[knocker]

Are we perhaps looking to get rid of the trough and possible get at least some build up of heights in the eastern Atlantic. The ext ecm is broadly similar to the GEFS,

 

[knocker]

93 1800z

 

 

[Singularity]

TROPICAL WEATHER OUTLOOK

NWS NATIONAL HURRICANE CENTER MIAMI FL

200 PM EDT SUN SEP 13 2015

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

1. An area of disturbed weather associated with a broad low pressure

system located several hundred miles southwest of the Cape Verde

Islands is showing signs of organization. Environmental conditions

are conducive for development, and a tropical depression could form

during the next day or two while the system moves west-northwestward

to northwestward across the central tropical Atlantic.

* Formation chance through 48 hours...high...70 percent

* Formation chance through 5 days...high...90 percent

 

This isn't the system that GFS develops in 5 days time - it's an area of disturbed weather some way SW of the Azores Isles which I have seen rated at near 0% for the next 48 hours and the same again for the next 5 days.

I got that info via this blog post: http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=3111.

 

I think it may be the one that comes into the field of view in the past two GFS op runs at about +252 hours. GFS then had it doing a dance with the one near the Azores on the 12z operational which was fun to watch. The 18z clears the Azores one quickly NE via the UK (as a weak remnant) and then traps the one that originates near the CV islands underneath a strong mid-Atlantic ridge. That 'trapping ridge' keeps on coming up in the GFS operational runs at the moment.

[summer blizzard]

This isn't the system that GFS develops in 5 days time - it's an area of disturbed weather some way SW of the Azores Isles which I have seen rated at near 0% for the next 48 hours and the same again for the next 5 days.

I got that info via this blog post: http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=3111.

I think it may be the one that comes into the field of view in the past two GFS op runs at about +252 hours. GFS then had it doing a dance with the one near the Azores on the 12z operational which was fun to watch. The 18z clears the Azores one quickly NE via the UK (as a weak remnant) and then traps the one that originates near the CV islands underneath a strong mid-Atlantic ridge. That 'trapping ridge' keeps on coming up in the GFS operational runs at the moment.

The one spoken about in the blog and shown near the Azores days 5-9 is 93L, the wave at 90% currently.

The one you've noticed was not developed by the GFS and is not currently an invest.

I can't post the link from my mobile but you can track this one through tropicaltidbits.com and then looking at the north Atlantic view.

Edited September 13, 2015 by summer blizzard

[knocker]

Might pop out tomorrow morning. Westerly gales forecast here as the low moves north.

http://www.tropicaltidbits.com/

 

[Polar Maritime]

Yes Knock an interesting day for the South Coast and the Channel as the Camborne Low pushes North, Im sure shipping will be effected.

Edited September 14, 2015 by Polar Maritime

[johnholmes]

TROPICAL WEATHER OUTLOOK

NWS NATIONAL HURRICANE CENTER MIAMI FL

200 PM EDT SUN SEP 13 2015

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

1. An area of disturbed weather associated with a broad low pressure

system located several hundred miles southwest of the Cape Verde

Islands is showing signs of organization. Environmental conditions

are conducive for development, and a tropical depression could form

during the next day or two while the system moves west-northwestward

to northwestward across the central tropical Atlantic.

* Formation chance through 48 hours...high...70 percent

* Formation chance through 5 days...high...90 percent

 

apologies, must have been looking at the previous system comments!

[johnholmes]

rainfall on the 00z of less than 20mm (18 and 13 for the two spot locations closest to me)

[knocker]

The Camborne low mark 2 PM

 

[Frosty.]

Most of this week will be very unsettled but then the Gfs 00z shows a nice ridge of high pressure building in for the weekend and following a more changeable spell for a time next week the rest of FI becomes anticyclonic with pleasant sunny days and chilly nights with an increasing risk of mist/fog patches. The Ukmo/Ecm/Gem 00z also show a ridge of high pressure for next weekend.     

Edited September 14, 2015 by Frosty.

[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

MONDAY SEP 14TH 2015

 

THE CURRENT GENERAL SITUATION.  A complex Low pressure area currently over the SW of England will move slowly NE across the Midlands and away to the NE tomorrow. Gale or severe gale force Westerly winds will move across Southern England later today and tonight easing tomorrow.

 

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 for much of the working week before moving North of the UK towards the weekend. Thereafter it moves back South again across the UK for a time before finally resting much further North than recently in response to High pressure near the UK.

 

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 for very wet conditions at times with heavy rain and gale or even severe gale force wind gusts at time, especially over the South. Later in the week Low pressure is shown to move away to the NE as a High pressure ridge moves across from the West. Thereafter the South and West become dry and bright under a West or NW flow while the North and East see further troughs move SE for a time with occasional rain. Then at the end of the period High pressure takes control across all of the UK with fine and sunny weather but chilly and probably foggy nights too.

 

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 in sequence to the events listed above from the operational model. The main difference being that next week sees more in the way of changeable conditions for all under a NW flow as the High to the SW makes less inroads into UK airspace maintaining a cool NW drift down across the UK throughout next week.

 

THE GFS CLUSTERS(14 Days) The GFS Clusters this morning are all over the place with various scenarios very different shown for the UK in 14 days time. While 40% most favour a slight bias towards slack Low pressure across the UK between High to the East and West a fair amount show something rather better under High pressure in the vicinity of the UK.

 

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 possibly very windy weather for the UK especially over the SW today and SE midweek.

 

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

 

GEM  GEM today shows very unsettled and windy weather this week with rain and wind at times before an improvement is shown for the weekend as a risge of High pressure crosses East over the UK. In the days that follow and into next week a rather slack pressure gradient develops across the UK with some rain about as weak disturbances aloft look likely to give rise to a lot of cloud even in the drier periods between the inevitable outbreaks of rain.

 

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

 

NAVGEM NAVGEM shows wet and windy conditions at times too throughout this week before a weak ridge crosses East over the UK at the weekend promising a drier and brighter interlude. It isn't long for the output shows a return to more changeable conditions as fronts move back in across the UK from the West or NW next week.

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 at the weekend pressure is shown to rise markedly with dry and fine weather developing for many next weekend. It looks unlikely to be the start of a sustained fine spell though as pressure falls and becomes relatively slack over the UK and Western Europe with rain at times from slow moving frontal systems before perhaps becoming rather drier from the NW later next week.

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

 

ECM 10 DAY MEAN  The ECM 10 Day Mean Chart from last night has leaned back towards a more changeable Westerly pattern of weather across the UK in 10 days time with the general rule of thunb between members of the ensemble pack showing Low pressure to the North and High pressure well to the SW.

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

 

NOTABLE TREND CHANGES FROM PREVIOUS RUNS The models are generally unchanged from yestterday in the general message of wet and windy weather this week followed by improvements at the weekend, but for how long is not well agreed upon.

 

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 99.2 pts.  At 3 days ECM leads at 96.2 pts with UKMO  at 96.1 pts while GFS lags behind at 95.3 pts. At 5 days UKMO is king at 85.9pts followed by ECM at 85.4 and GFS at 83.4 pts. Then at 8 Days ECM still leads at 59.4 pts over GFS's 50.9 pts. Finally at Day 10 ECM leads GFS at 39.0 pts to 33.0 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.png

 

MY THOUGHTS   The models have changed little over the last 24 hours with the UK still shown to be under attack over the next 4-5 days of unsettled and occasionally very windy weather with spells of sometimes heavy and thundery rain. The main focus for disruption is likely to be from wind in coastal areas today in the SW and again from midweek in an area yet to be determined as a particularly nasty and complex Low looks likely to move it's way NE over Southern England. On current thinking we look to be spared widespread gales as the Low tracks over or to the South taking the worst of the winds across Northern France though this could change. We all look likely to have a strong blow from the West on Thursday and for a time Friday too as this feature moves away NE across the North Sea with a sunshine and shower mix across the UK. Pressure is then shown to rise strongly and a ridge is well documented on all output to move across from the West over the weekend with dry and bright weather developing for many once the last of the showers exit the East early on Saturday. It's from this point on when the waters muddy with some output like GFS showing High pressure once established never leaving the SW with largely dry conditions thereafter for the remainder of the period extending to all areas by the end of the run as pressure builds strongly across all of the UK then. The general message is a bit less attractive than this though with much more reluctance to bring High pressure across the UK and with pressure having leaked away next week further changeable weather looks far more likely to affect the UK next week with occasional rain from troughs which could be slow moving under slack conditions which look to be well supported for next week from GEM and ECM and the GFS Clusters. So in a nutshell a very wet few days to come with strong winds a risk too with the best weather for once this week likely to be in the NW. Then a better period of weather at the weekend with dry and bright conditions might last into next week before a slow reversion back towards more changeable weather looks likely later but all bets are off really on where we go next week and probably won't become clear for a time yet while the position of the passage of this weeks clutch of Low pressure is finally nailed down.

 

BEST CHART OF THE DAY 00z RUN

 

http://www.wetterzentrale.de/pics/Rtavn3601.gif

 

In selecting the best Chart of the Day I had no problem in selecting this chart as it highlights a typical Autumn anticyclone nesting across the UK with light winds for all and fine and sunny early Autumn weather in luke warm conditions by day contrasting with cool and often foggy nights. It is though at T+360hrs so is unlikely to verify as shown unfortunately.

 

WORSE CHART OF THE DAY  00z RUN

 

http://www.wetterzentrale.de/pics/Rnvg721.gif

 

For the worst chart I have gone for the Navgems 72hr chart but in all honesty I could of gone for any of the models at that time point and they would of all looked equally bad. This chart shows a deep Low near SW England with gales or severe gales around the UK coasts but not inland. This is probably the best scenario for the Low to be held to the South and SE keeping the strongest winds as on this chart over Northern France. It is likely though that copious rainfall in the South will be a problem and we will all experience a strong blow from the West later on Thursday as the Low exits away to the NE.

 

Next update from 09:00 Tuesday Sep 15th 2015

[Singularity]

The one spoken about in the blog and shown near the Azores days 5-9 is 93L, the wave at 90% currently.

The one you've noticed was not developed by the GFS and is not currently an invest.

I can't post the link from my mobile but you can track this one through tropicaltidbits.com and then looking at the north Atlantic view.

 

Ah... now I see it. It all makes sense having looked on that site - thanks for the link.

 

I was confused by the way the low seemed to develop from nothing in 5 days time on the N. Atlantic charts. Turns out GFS keeps it too shallow to show up on the charts until that time... lesson learnt! 

 

 

In which case, there's every chance that the behaviour of the Azores/N. Atlantic high pressure beyond 5 days range could end up substantially different to what's currently modeled. It'll all depend on how strong the tropical cyclone becomes... I see the GFS 06z has backed off a bit and it seems that a weaker low tends to end up further west with less chance of influencing our weather much.

[Frosty.]

The Gfs 6z looks very unsettled for most of this week with wednesday bringing a lot of rain northwards across england and wales associated with the remnants of Ex-Tropical storm Henri, heavy rain working north and behind it, the southeast brightens up with temperatures into the low 20's celsius as there is a lot of warm air wrapped up within the ex tropical storm but for many it looks dull and wet with temps in the mid teens celsius, meanwhile, scotland and n.ireland escape the rain on wednesday with sunny spells and just isolated showers but as the low pushes further NE on thursday, its scotlands turn to have a spell of heavy, persistent rain and strong winds. Eventually the low responsible for all the unsettled weather pushes away northeastwards with a ridge of high pressure arriving from the west just in time for next weekend which looks increasingly fine and warm with temps into the high teens to low 20's c, especially on sunday although it starts to turn unsettled in the west with rain pushing eastwards, the rain pushes east across most areas next monday but ahead of it across the east and southeast it looks warm and fine. Thereafter, it looks showery for a few days with a very slack pressure pattern before high pressure starts to take control from scandinavia with a strong block forming for a time which holds the atlantic systems at bay, becoming increasingly settled across all parts of the uk with plenty of sunshine and pleasantly warm daytime temps, by the very end of the run it starts to become more unsettled from the west but for most of low res its looking very nice.

Edited September 14, 2015 by Frosty.

[johnholmes]

continuing my check on GFS r/f totals different runs; 06z has 20/10mm

 

It has yet over the past 48-72 hours to come up with 2 runs, consecutive, with totals within 10mm of one another.

I am not having a go at the model, just hoping (!) that some who complain in winter at snow predictions being wrong can see it happens all the time. 500mb fairly easy relatively to get the pattern correct, the low 500mb, 18,000ft where most of the moisture is; incredibly difficult to get this correct even 24 hours out sometimes 12 hours.

please try and remember this come the winter.

[Polar Maritime]

Just look how far South the Jet ends up on Wednesday, Heavy rain crossing the country with gales especially the South coast as the Camborne Low sweeps through the Channel and up into the North Sea by Thursday. Much depends on how the Low interacts with the Jet, So an interesting 24hr coming up as the models firm up on exact track/detail. More or less is the general question..

Edited September 14, 2015 by Polar Maritime

[summer blizzard]

Ah... now I see it. It all makes sense having looked on that site - thanks for the link.

 

I was confused by the way the low seemed to develop from nothing in 5 days time on the N. Atlantic charts. Turns out GFS keeps it too shallow to show up on the charts until that time... lesson learnt! 

 

 

In which case, there's every chance that the behaviour of the Azores/N. Atlantic high pressure beyond 5 days range could end up substantially different to what's currently modeled. It'll all depend on how strong the tropical cyclone becomes... I see the GFS 06z has backed off a bit and it seems that a weaker low tends to end up further west with less chance of influencing our weather much.

 

Amusingly our entire model debate may now be redundant. Despite looking lovely and being given 90% last night, convection over 93L looks to have collapsed and tonight's GFS suggests no development at all (a coup for the Euro which was always bearish).

 

The result on the model output looks to be that tonights GFS is a bit more settled (probably because of the lack of an upper low beneath) between days 5-10.

[phil nw.]

Just look how far South the Jet ends up on Wednesday, Heavy rain crossing the country with gales especially the South coast as the Camborne Low sweeps through the Channel and up into the North Sea by Thursday. Much depends on how the Low interacts with the Jet, So an interesting 24hr coming up as the models firm up on exact track/detail. More or less is the general question..

Yes quite a nasty low for midweek PM with bands of heavy rain for many and some strong winds for a while.

Looking ahead to the weekend sees a complete contrast with rapidly rising pressure across the UK as shown in both GFS and UKMO runs

 

so it looks like settling down for maybe 2 or 3 days before the high gets shunted towards E,Europe/Scandinavia again.

GFS mean T180hrs.

 

How often have we seen the heights building over there in  recent months?Along with another Atlantic trough just to our west it's becoming almost our default pattern.

[johnholmes]

And another change in rainfall totals 35 and 29 mm, pretty much back to its ideas over 72 hours ago.

 

http://www.wetterzentrale.de/topkarten/fsgfsmeur.html

 

much of it due to it upping considerably the next 24 hour rainfall.

Edited September 14, 2015 by johnholmes

[DR(S)NO]

Yes quite a nasty low for midweek PM with bands of heavy rain for many and some strong winds for a while.

Looking ahead to the weekend sees a complete contrast with rapidly rising pressure across the UK as shown in both GFS and UKMO runs

gfs-0-120.pngUW120-21.GIF

 

so it looks like settling down for maybe 2 or 3 days before the high gets shunted towards E,Europe/Scandinavia again.

GFS mean T180hrs.

gens-21-1-180.png

 

How often have we seen the heights building over there in  recent months?Along with another Atlantic trough just to our west it's becoming almost our default pattern.

Hopefully this is model related....it does appear to me...that this year has seen a number of low pressure systems move across the UK and then up the North Sea....certainly more so than I can remember in past years.

Is this something that is likely to continue into the winter months and what influence would that have on the weather we would experience ?

[phil nw.]

Hopefully this is model related....it does appear to me...that this year has seen a number of low pressure systems move across the UK and then up the North Sea....certainly more so than I can remember in past years.

Is this something that is likely to continue into the winter months and what influence would that have on the weather we would experience ?

I think we would be specualting regarding Winter DR.

Best keep this thread for what we can actually see in the current charts.

Nothing to stop you opening another thread on this though or maybe use the General weather chat thread?

[knocker]

The GEFS anomalies showing a brief respite with a transient ridge at the weekend before our old friend the upper trough pays another visit although this too may be brief.

http://www.tropicaltidbits.com/