Model Output Discussion 1200 hrs 30/09/14

[Gibby]

HERE IS MY LATEST ANALYSIS FROM THE OUTPUTS OF THE WEATHER COMPUTER PREDICTION MODELS FOR TWO WEEKS FROM 8AM TODAY SUNDAY OCTOBER 19TH 2014.

 

NEXT UPDATE MONDAY OCTOBER 20TH 08:00

 

THE CURRENT GENERAL SITUATION. A deep Low to the NW of Britain moves slowly North with a trailing cold front over SE England moving away East. A breezy WSW flow covers the UK.

 

MODELS-2 WEEK HEADLINE  Changeable weather with rain at times but some drier and brighter periods across the South at times later. Near or slightly above average temperatures. Rather windy at times in the North.

 

THE JET STREAM ENSEMBLE FORECAST The Jet flow is shown to blow in a NE direction across the UK currently but will quickly be replaced by the flow running East across the UK this week. It then ridges North around High pressure South of the UK from next weekend and continues this somewhat ridging pattern around or over the UK for much of the rest of the period.

 

GFS The GFS operational today shows a changeable period of weather across Britain for the next two weeks. As repeated areas of Low pressure track East to the North of the UK there will be bouts of wind and rain for all. These will be frequent and heavy at times across the North will gales or severe gales possible at times. In more Southern areas High pressure to the South, SE or SW will ensure rather less active fronts reach the South at times and while some will bring occasional rainfall at times it is likely to be lighter and less frequent in occurrence than further North. All areas under a SW or west flow will remain relatively mild overall.

 

THE GFS ENSEMBLES. In simplified terms the Ensemble pack show a basic pattern of High pressure to the South and Low to the North of the UK over the period with a broad Westerly pattern of weather persisting throughout. The North will see the main share of wind and rain, heavy at times with gales while the High pressure zone close to the South at times will prevent anything more than occasional lighter rain at times between longer drier spells with fairly average temperatures if not rather mild at times across most parts of Britain.

 

UKMO UKMO this morning shows a weakening cold front moving SE across England and Wales next weekend with a band of rain and drizzle slipping slowly South over the South. Further North blustery showers look more likely in a stronger and fresher Westerly flow.

 

THE FAX CHARTS  The Fax Charts show warm sector conditions developing later in the week in a broad and mild WSW flow. A cold front is shown to move slowly SE late in the week turning things more showery over the North and bringing dull and drizzle conditions down across Southern Britain in mild air late in the week and next weekend.

 

GEM The GEM operational today shows very changeable and windy conditions with gales much more prolific UK wide on this run as High pressure to the South is held further away after the end of this week. As a result all areas are shown to have periodic bands of gales and heavy rain followed by squally showers and cooler air. There is a period of less wet and windy weather for the South later this week under a mild SW'ly over the South though

.

NAVGEM NAVGEM also shows changeable weather under Westerly winds throughout it's run this morning. It too shows a spell of High pressure close to the South for a time restricting the intensity of rain and wind down here for a time but even so some rain on a couple of fronts is show to cross the South from the NW towards the end of it's run to bring the chance of moderate rain and stronger winds here too. 

 

ECM The ECM operational today continues it's theme of changing changeable Westerly winds into a period of High pressure based conditions with mist and fogs likely over Southern Britain as the High pressure takes control by the start of the second week. Temperatures would remain relatively mild but it could become chillier overnight if skies clear and the mists and fogs take hold.

 

NOTABLE TREND CHANGES FROM PREVIOUS RUNS The trend remains unchanged from the basic Westerly flow continuing across the UK, most active over the North with pressure building close to the South at times later.

 

MY THOUGHTS  There is little change in the basic theme of Westerly or SW winds across the UK over the next week or two. However, with pressure expected to rise from the South at times amounts of rain under this changeable and unsettled pattern remains undecided with slow moving fronts descending down from the North into Southern England becoming slow moving and delivering spells of drizzly rain rather than anything more substantial. In the North heavy rain looks like being much more frequent and often accompanied by strong westerly winds too. ECM continues it's theme of bringing High pressure up across the UK in week 2 which if verified would bring quieter Anticyclonic conditions with light winds and some sunshine for many but also the risk of dense and persistent overnight mists and fogs too when it could turn more chilly. Overall though the prospects given the time of year appear quite moderate with the North likely to bear the brunt of bad weather while Southern Britain in particular see nothing out of the ordinary overall with temperatures remaining well up for all areas given the anticipated persistence of the Westerly flow.

[Captain Shortwave]

The ECM op and ens are still keen on building high pressure in strongly during week 2. 

GFS and GEM are not so bullish about this to be honest. 

[bluearmy]

The ECM op and ens are still keen on building high pressure in strongly during week 2. 

 

 

GFS and GEM are not so bullish about this to be honest. 

 

the ecm ens continue to show the area around the uk to have the NH's  largest high anomoly in the 8/12 day period. i think a quieter spell is becoming unavoidable.

[snowflakey]

A slight chance of retrogression up towards Greenland maybe ?

[phil nw.]

Indeed naefs also showing a similar +ve heights around the UK in week 2 and ongoing out to the end of the run.

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

A warm high having tm air within it but at this time of year, if it persists, nights will cool off in time under any clearances with an increasing risk of fog and frosts.

Away from the north west though things do look like settling down towards the last week of the month.

[draztik]

While it would be foolish to ignore the ensembles into week 2, esp the ecm ens which indicate higher than average heights for our region - indeed the core of those heights are centred directly over the UK into days 10-15 - saying all that....the gfs 6z follows the 0z with a more unsettled outlook into week 2 and beyond. One to watch w/ interest.

Edited October 19, 2014 by draztik

[Cloud 10]

Large scale differences between the ECM 00z and GFS 06z operational runs at day 7 don't inspire confidence for any week 2 predictions,and as we saw a few days ago ensemble means are not to be trusted either when arctic high's are around,although are still the best guidance we have !

 

ecm..  gfs..

[shaky]

Large scale differences between the ECM 00z and GFS 06z operational runs at day 7 don't inspire confidence for any week 2 predictions,and as we saw a few days ago ensemble means are not to be trusted either when arctic high's are around,although are still the best guidance we have !

 

ecm..ECH1-168.gif  gfs..gfsnh-0-168.png

what a beauty of a chart from the 06z gfs!!vortex once again shredded and plenty of northern blocking !!oh and you guessed it even more snow for Scandinavia!!!!

[Frosty.]

ECM 00z ensemble mean shows an unsettled week ahead and a short burst of colder weather by next weekend with air which originated in Greenland but is then modified as it crosses the atlantic but even so, it would turn the showers wintry on hills / mountains in scotland with snow at higher levels for a time. Thereafter it's high pressure building in strongly for week 2 as the atlantic takes another nap. 

[Newberryone]

While it would be foolish to ignore the ensembles into week 2, esp the ecm ens which indicate higher than average heights for our region - indeed the core of those heights are centred directly over the UK into days 10-15 - saying all that....the gfs 6z follows the 0z with a more unsettled outlook into week 2 and beyond. One to watch w/ interest.

Large scale differences between the ECM 00z and GFS 06z operational runs at day 7 don't inspire confidence for any week 2 predictions,and as we saw a few days ago ensemble means are not to be trusted either when arctic high's are around,although are still the best guidance we have !

ecm..ECH1-168.gif gfs..gfsnh-0-168.png

Interesting thoughts from the above posts with regards to week 2 when you read the following quote from the Irish met office..

Further outlook (high degree of uncertainty): A possibility of some rain on Friday followed by scattered showers on Saturday and then by mainly dry weather over the long weekend. (Average temperatures: daytime in the low teens typically and cool nights).

Edited October 19, 2014 by Polar Maritime
Can we please stick to model output, There are other threads for METO forecasts. Thanks.

[Bobby]

While it would be foolish to ignore the ensembles into week 2, esp the ecm ens which indicate higher than average heights for our region - indeed the core of those heights are centred directly over the UK into days 10-15 - saying all that....the gfs 6z follows the 0z with a more unsettled outlook into week 2 and beyond. One to watch w/ interest.

 

Been watching the various ensemble means...the GEM ENS have consistently been reluctant to build HP akin to the various ops since the idea of 1030-1035mbs highs near us started. The NAEFS has been slow to back the idea also. GEM, NAEFS day 10

 

 

 

Latest GFS mean has really gone off the idea

 

 

I think a build of high pressure settling things down - especailly in the south - is likely. But not a 1035mb high over us like the ECM is showing. The last 2 GFS ops aren't implausible either considering everything

[draztik]

I'm wondering if we are starting to see a new trend emerging; gfs & Canadian ens giving support to the gfs 6z's unsettled outlook into week 2. Ecm ens appearing isolated somewhat? Hmm, this afternoons runs should give us a better idea one way or the other.

[Frosty.]

Another unsettled gfs run, the 6z if anything is even more unsettled until near the end of low res, high pressure requires a few bites of the cherry to gain a decent foothold across southern uk but by the end of the run I get the impression the atlantic would bulldoze through soon after. There is quite a cold snap next weekend across the northwest corner of the uk (n.ireland / n & w scotland) with a risk of hill snow, maybe down to modest levels with a brief burst of polar maritimes. According to this run, high pressure will have a fight on it's hands to gain the upper hand beyond T+192 hours.

[MR EXTREMES]

lovely wedge of heights over scandi into the polar area looks very different this year.

gfs 72hr vortex looks all over the place this year.

[MR EXTREMES]

at t120 blocking into the arctic area more extensive than gfs earlier run.

[Wilxy]

at t120 blocking into the arctic area more extensive than gfs earlier run.

 

The blocking looks better on this run but the angle of the high pressure has allowed warmer uppers to push north towards Scandinavia

I am hoping this wont effect the Snow gain but there are some shifts the weather pattern for next week at this stage. 

[Ali1977]

WAA heading into Greenland, at T186, Northerly on this run maybe??

[Midlands Ice Age]

lovely wedge of heights over scandi into the polar area looks very different this year.

gfs 72hr vortex looks all over the place this year.

 

THis looks like a perfect H formation and only at 72hrs..... (not an expert mind you)

 

From my viewpoint it looks as though WAA is being pumped up directly into the massive polar high from both the UK and Scandy, but also from the Aleutions and very east of Siberia with the effects of a complete split into two of the polar vortex.

 

Surely this might get Steve M a bit excited even though its only October? 

 

Has this sort of chart been seen before at this time of year?

 

MIA

 

Edited October 19, 2014 by Midlands Ice Age

[knocker]

The GEFS 12z ens anomalies develops the trough Greenland/mid Atlantic which impacts the development of the HP to the SW/S of the UK but is it just a blip although no substantial positive heights after.. The PV remains very weak. No immediate sign of colder air with temps above average UK/Europe.

 

Be interesting to see what the ECM comes up with vis a vis the trough.

Edited October 19, 2014 by knocker

[SMU]

Afternoon All

 

Possible OCTOBER 2014 a RECORD H5 -AO GLOBAL MONTH???

WINTERS BIGGEST SIGNAL?

 

Just an update to my post from a couple of days ago regarding the AO Ensembles. These are a good way to illustrate the mean trending of the global H5 anomalies relating to this Index.

It also highlights the GFS over progressive nature with a strong bias to the historic long term mean- its out of date!!!!

 

2 days ago

 

Todays.

 

As you can see the GFS 8-16 day ensembles expected a strong ascent to the neutral zone before continuing to rise to on average a +2 index.

Looking at the month as a whole you would expect it then to pan out on a landing zone around -0.5 to -1. which is pretty low.

However now the means are suggesting ( as suggested ) that the modal change from Negative to Positive is less pronounced & in a shorter weaker burst. Also further down the line the mere scent of another drop.

 

Looking at the daily index values ( ive taken them from the graph)

So if anyone has any ACTUAL values please PM me the link as the NOAA is out of date.

we get a rolling mean of -31.8 / 19 days =

 

-1.67

 

The record is -1.5 on the NOAA site- so we need to manage -1.35 for the last 12 days....

Which may be a tad out of reach!

 

Current Anomaly.

 

 

Another strong signal towards Winter.

 

For November we move more towards stratosphere temp anomalies....

 

S

 

 

 

 

[Mucka]

A Murr sausage in October? 

 

 

(Steve, just PM'd you)

Edited October 19, 2014 by Mucka

[knocker]

AO !9th

 

ECM HRES -1.0

 

NCEP GFS -.5

Edited October 19, 2014 by knocker

[Captain Shortwave]

ECM still happy to build high pressure in for week 2

It all seems to come down to what direction the cold air over the Arctic is displaced when high pressure builds over the pole. This is complicated by having cut-off lows upstream. The GFS keeps one of these cut off which causes low heights to make a bee-line for the UK. The ECM opens this trough up on the Eastern seaboard and builds pressure over the UK in response.

GFS for comparison

[The PIT]

ECM horror show even in deep FI must be too progressive.

[The PIT]

ECM still happy to build high pressure in for week 2

It all seems to come down to what direction the cold air over the Arctic is displaced when high pressure builds over the pole. This is complicated by having cut-off lows upstream. The GFS keeps one of these cut off which causes low heights to make a bee-line for the UK. The ECM opens this trough up on the Eastern seaboard and builds pressure over the UK in response.

GFS for comparison

Well I call it deep FI very unlikely too happen