Model Output Discussion 1200 hrs 30/09/14

[SMU]

Whilst its at day 10 a spectacular ECM chart tonight with arctic high pressure, steep -AO and a tanked OPI index.

Crackerjack.

[TSNWK]

Hehe... Mucka, Nick Sussex and Steve Murr on the same page... Can only mean one thing! It's party time.. Enjoy the ride folks..I think this must be my 10th season and boy is it fun.

[nick sussex]

Hehe... Mucka, Nick Sussex and Steve Murr on the same page... Can only mean one thing! It's party time.. Enjoy the ride folks..I think this must be my 10th season and boy is it fun.

True if the ECM 240hrs doesn't lead to a response from myself or Steve then you know something weird is going on!

 

Last years party turned into a damp squib so lets hope for better this year!

[ANYWEATHER]

Its a more traditional theme to the weather to come with alternating cold and mild spells, high pressure building from the south on both models at T+168  is still in fantasy island

[TSNWK]

Yes it is great to see some of winter big guns emerge from their summer hideouts.. Early doors of course, but nothing wrong with limbering up before battle commences in a month or so..

Only on Monday I googled " Thames Streamer 2010 " and was offered several links to netweather regional snow watch threads from that time.. And enjoyable reads they were too - certainly help get you in the mood if your a coldie.

Cheers.

[carinthian]

Yes C they hinted this of sorts the other day as i mentioned, The Models are really skitty atm out in the runs as they continue with difficulties with the strong heights over the Northern Hemisphere.

PM, agree there. The synoptics are different to this time last year. 10 day models keep shifting  the high cells from Alps to Ireland . The -NAO remains consistent over the past 6 weeks. A shot of colder weather looks increasingly likely as the enter the last month of Autumn.

 C

[carinthian]

PM, agree there. The synoptics are different to this time last year. 10 day models keep shifting  the high cells from Alps to Ireland . The -NAO remains consistent over the past 6 weeks. A shot of colder weather looks increasingly likely as the enter the last month of Autumn.

 C

Our latest medium range spatial resolution model this evening has progged us our first snowfall of the season ( 14cm next Wednesday )  at 2000m altitude with temp 0f -3c . Its a start,was not expecting that 5 days ago.

 C

Edited October 17, 2014 by carinthian

[damianslaw]

We have a very amplified pattern over the atlantic hence reason for the long draw southerly airstream we have now, and with the Jetstream forecast to stay rather amplified a pronounced ridge building from the south looks the form horse as we approach the latter part of the week, combined with buckling in the jet there is every opportunity for heights to quickly inflate northwards over the country with a longwave trough setting up shop further to our west than where it is at present - the ECM output has very strong plausibility in this regard.

 

All eyes on developments across the NE USA Seaboard area - lesser amplification here would prevent such height movement. What doesn't look like happening anytime soon though is a strengthened polar vortex thanks to continuation of stronger heights over the Pole region.

 

This October so far has failed to develop a flat westerly pattern, unlike last year and I there is a strong chance it will fail in totality in this regard bar a few days during next week, indeed the ex tropical storm due to track towards us early next week will only help to reinforce the amplified flow - and the last two that hit the country were major game changers..

 

 

[cyclonic happiness]

I hate that the 'green run' is now 'the yellow' run ....shows my anal commitment to model watching lol :-P

[knocker]

Looking at the D14 pattern looks like quite a warm set up with less amplification in N. America and no organised PV. a and a more organised jet.

Edited October 17, 2014 by knocker

[bluearmy]

Just looking at the latter ECM anomalys from knocks post and naefs update - naefs seems to have the main vortex over N W Siberia whilst ECM looks to be nw of greeny . Either way, both maintain a split by the end of week 2.

[Captain Shortwave]

Just looking at the latter ECM anomalys from knocks post and naefs update - naefs seems to have the main vortex over N W Siberia whilst ECM looks to be nw of greeny . Either way, both maintain a split by the end of week 2.

I suspect the split will last until the end of the month (despite my dubious opinion of the ECM op). I guess outside of the next couple of weeks, Ricardo's work will get a solid test this winter as I suspect a -1.5 - -2 value come the end of the month.

The Azores high looks likely to ridge in around day5/6 and day 9 onwards. Though both look transient.

[SMU]

Evening All-

 

Following on from the post in the OPI thread the models do give us some indication of what the jet is doing you just need to identify the signals.

 

The UKMO 144 is a good case in point.

 

 

 

In Black- Cut off lows, all around the globe. Showing the jet is digging south in multiple locations allowing in some cases for snow to reach lower lattitudes. When you get a sinuous jet the lows you will see a continuous easterly progression of lows in all quadrants.

 

In Red- A shallow ( in terms of heights ) high pressure over the pole, but enough to steer low pressure systems into the mid lattitdues, remember the long term October mean ( especially late in the month) will show the pole having its lowest heights around 500 decameters, so the high is indicating higher thicknesses ( & from our feedbacks we know higher thicknesses usually indicate a warmer stratosphere )

 

In silver: 2 weak area of vortex with small areas of low heights, quite detached from each other & showing no signs of stabilizing & circulating East. Also a nice ridge moving into the pole over scandi which at this time of year is unusual when again the westerlies should be penetrating all the way towards Western Russia.

 

In Orange - Lastly the reverse flow around 3 quadrants of the globe which shows ( or should show) a weak zonal wind as the overally flow is more or less Easterly. That's inverse to the October average flow.

 

Complete the same exercise on the ECM& you see even more distortion of the pattern. remember the more extreme the indices the more extreme the weather becomes V the norm.

 

 

the ECM is a work of art if your looking for extreme indexes, the jet is all over the show meandering around the globe & a very strong negative zonal wind.

These are the quadrants I use for Winter...

 

Also the comment that was used the other day that the UK isn't effected by anything downstream is almost laughable when the azores high is linked to developments back around the globe....

 

I will leave you with the GFS NOAA AO ensembles from 00z earlier-

Interesting to see what they look like tomorrow...

 

 

for reference here is a +5 AO one of the most positive charts you can get-

 

just 1 cut off low & a jet with maximum easterly progression.

 

Cheers

S

 

Edited October 17, 2014 by Steve Murr

[Man With Beard]

The coldest November in 100 years is possible looking at the models

I presume you refer to ECM T240 - well, 'possible' of course, but backing the ECM op at this range is, in all honesty, like a backing a horse with 3 legs at the Grand National. The ECM mean is much better - usually - at D10, and it looks pretty westerly to me. Phil suggested colder options in the ECM monthly, so maybe something might emerge further down the line.

[knocker]

Well all I can say is I've looked at the ECM monthlies and there is nothing cold about them up to the end of the run as far as I can see.

 

Nor does the 18z GFS indicate any either.

Edited October 18, 2014 by knocker

[Mucka]

GFS and UKMO still differ greatly when it comes to how to deal with the split energy coming up against the Scandi ridge. We see this many times in Winter where the GFS always puts the place in a spin because it wants to flatten the pattern - not so important when the ridge is over Scandi and at this time of year though 

 

 

This will be of more interest to most people at present I dare say

 

 

Certainly need to keep an eye on that.

Edited October 18, 2014 by Mucka

[knocker]

Nasty looking chart GFS 00z for 06z Tuesday. Gonzalo paying a visit. with low 977mb Scotland and some very strong winds in the western half of the country.

 

What's split energy?

Edited October 18, 2014 by knocker

[Mucka]

Nasty looking chart GFS 00z for 06z Tuesday. Gonzalo paying a visit. with low 977mb Scotland and some very strong winds in the western half of the country.

 

What's split energy?

 

Yes I think someone else alluded to the remnants of Gonzalo still possibly causing trouble for the UK yesterday.

 

Split energy - I'm just referring to how the jet can buckling and splitting when coming up against high pressure so that low pressure sometimes splits two ways, one going over the block and one under. The default is over but sometimes low pressure undercuts and keeps the high pressure at higher latitudes, especially if it cuts it off. UKMO does this and ends at 144 with a cut off Scandi high.

 

GEM as an example of the energy splitting as it meets the ridge over Scandi. I suppose it isn't proper meteorological terminology but it is fairly commonly used in the MO thread (by me anyway.  )

 

Edited October 18, 2014 by Mucka

[knocker]

The ECM ops for Tuesday.

 

[Mucka]

Looking across the output and beyond it looks quite possible we could see a chilly first week of November. Slightly tongue in cheek but also out of genuine curiosity, When was the last time snow fell on bonfire night (5 Nov) in lowland England? I don't ever remember it in my lifetime and I'm a fossil.

Edited October 18, 2014 by Mucka

[Polar Maritime]

Nasty looking chart GFS 00z for 06z Tuesday. Gonzalo paying a visit. with low 977mb Scotland and some very strong winds in the western half of the country.

 

Yes Knock, It's looking quite a complicated system at 78hrs with Severe Gales for the East Coast and out in the Atlantic/Irish Sea. 

 

Edited October 18, 2014 by Polar Maritime

[Frosty.]

Most of next week looks unsettled, windier and cooler than recently thanks to the impact from the remnants of ex Hurricane Gonzalo during the first ½ of next week, quite similar to the effects of Bertha in august but then it's an improving picture with high pressure bouncing back with a vengeance towards the end of the Gfs 00z op run which has been the trend in recent days for an increasingly fine and mild end to october and early november, mild days but chilly nights with a risk of slight frosts and fog patches.

Edited October 18, 2014 by Frosty.

[Gibby]

HERE IS MY LATEST ANALYSIS FROM THE OUTPUTS OF THE WEATHER COMPUTER PREDICTION MODELS FOR TWO WEEKS FROM 8AM TODAY SATURDAY OCTOBER 18TH 2014.

 

NEXT UPDATE SUNDAY OCTOBER 19TH 08:00

 

THE CURRENT GENERAL SITUATION. A deep Low is moving slowly North over the Atlantic with a trailing cold front lying SW to NE over Southern Britain clearing East tomorrow.

 

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 for the next few days before turning more West to East or even NW to SE across the UK next week. It is shown to ridge up and around the UK for much of the time thereafter indicating pressure High close to the South of the UK.

 

GFS The GFS operational today shows the current SW flow veering more Westerly and NW for a time dragging much cooler air SE across the UK following an active cold front with gales and heavy rain for all for a time towards Tuesday. The cool showery NW flow will then give way to more moderate conditions later in the week as pressure builds close to and then over Southern Britain to begin and then all of the UK with widespread fog and some frost by night becoming commonplace late in the run replacing the unsettled weather still over northern Britain later next week. Late in the run High pressure is shown to move away slowly East with a cool SE flow gradually developing with fronts to the West and South.

 

THE GFS ENSEMBLES. The GFS Ensembles are quite supportive of it's operational with the gradual transition towards more settled conditions under UK based High pressure well modelled for next weekend and beyond. before then a period of changeable Atlantic based conditions remain with rain at times though not much in the South from later next week. Temperatures returning closer to normal overall looks likely.

 

UKMO UKMO this morning shows High pressure over France later next week and Low to the North. This promotes a Westerly flow quite modest in strength and with pressure quite High generally. The Westerly flow will carry a lot of cloud and a frontal boundary could lie close to the South with some rain and drizzle in places with brighter weather with scattered showers likely over the North.

 

THE FAX CHARTS  The Fax Charts show the SW flow across Britain being replaced by more Westerly winds from tomorrow. This will then strengthen on Monday evening as a deep  Low runs quickly ESE to the North carrying an active front SE across all parts. Cooler showery weather follows for a time towards midweek before a warm front crosses East bringing mild and cloudy warm sector conditions across the UK by later next week.

 

GEM The GEM operational today keeps High pressure later next week slightly further to the South maintaining a stronger though still relatively mild Westerly flow over all areas. Some rain at times would be expected especially across the North and West with some cooler and more showery interludes here. Not that much rain would reach the South under weakening fronts but temperatures and humidity here would be held well up.

 

NAVGEM NAVGEM looks broadly similar to the rest with a weakening frontal band edging slowly South across England and Wales late next week with occasional rain and drizzle. This then clears next weekend as High pressure never far away from the South anyway builds back slowly across all Southern areas at the end of the run with fine weather and mist and fog overnight the likely hazards then. 

 

ECM The ECM operational today shows westerly winds next week following the cooler incursion of NW'lies on Tuesday. These westerly winds would bring mild and rather cloudy weather with some rain towards the North and NW. A weakening cold front is then shown to cross SE setting up a more WNW flow with occasional rain most likely then in the North and East while the South and West become largely dry and benign with a lot of cloud and average temperatures.

 

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 steadily building close to the South.

 

MY THOUGHTS  The theme today bases itself around how much influence the projected higher pressure developing from the South and SW late next week and beyond has on suppressing the influence of a Westerly flow and accompanied troughs across Britain. As is usual in these scenarios details are hard to pin down with accuracy but what usually transpires is that the UK ends up with a weak or stalled front lying somewhere and giving cloudy and drizzly conditions in its vicinity while the North have the best chance of seeing some sunshine and passing showers after the front passes. There is strong suggestions that a cold front will clear the South next weekend and introduce less mild and clearer air to all areas then and GFS then moves on to build pressure strongly across the UK from then with fine and dry weather with mist and fogs overnight highly likely for all. Other output suggests such a High be held just to the South or SW of the UK with developing benign and relatively non eventful conditions across the UK in a moderate West or WNW flow. What is not shown is a Jet Flow which ends up South of the UK with attendant storms and heavy rainfall that would bring and instead we have a ridged pattern in the flow taking it North over the UK and down over central Europe from later next week. So as a result we can safely say that conditions will remain relatively mild for the foreseeable future with just exceptions being from brief polar maritime incursions affecting the North at times next week and overnight home grown cold if the High develops as GFS suggests in week 2 giving an increased risk of frost. So early season heating bills can be held under control for the next few weeks at least.

[Captain Shortwave]

For week 2, there does seem to be support across the ensembles of both the GFS and ECM for a pressure rise in the UK locale.

The dominant lobe of the troposheric vortex looks like it will push into the Canadian/Greenland area and promote troughing in the Atlantic. Hence the rise in pressure near the UK. It does looks likely the the polar profile will continue to see a split with a positive anomaly over the pole. This should keep the jet fairly weak and meridional, this also supports a more anticyclonic picture as opposed to the zonal weather we would normally observe with low heights dominant over Greenland.

[knocker]

Following on from last night. No sign of development vis a vis the PV, amplification North America, jet still fairly weak tending towards the north of the UK and HP encroaching from the SW. Probably the weather becoming a bit more settled with the temps generally above average.