Model Output Discussion October 2012

[syed2878]

hi guys i been posting the noaa discussion on this thread please remove if it's in the wrong section thx.

PRELIMINARY EXTENDED FORECAST DISCUSSION

NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD

959 AM EDT MON OCT 01 2012

VALID 12Z FRI OCT 05 2012 - 12Z MON OCT 08 2012

GENERAL FLOW PATTERN/MODEL PREFERENCES

======================================

THE GUIDANCE IS IN GENERAL AGREEMENT THAT AN ERN PAC REX BLOCK

WILL EDGE INTO THE WEST COAST WITH TIME...LEADING TO INCREASED

TROUGHING MID-CONTINENT. OUTSIDE THE 00Z CANADIAN...THE GUIDANCE

IS IN BETTER THAN AVERAGE AGREEMENT. ONE MODERATE EXCEPTION WAS

IN REGARDS TO A FRONTAL WAVE THE 00Z ECMWF ADVERTISES TO MOVE FROM

THE SRN PLAINS TO THE WEST OF THE APPALACHIANS FROM LATE FRI

THROUGH LATE SAT THAT HAS MINIMAL ENSEMBLE SUPPORT. A LARGER

PROBLEM CROPS UP IN WRN CAN SUN/MON...WHEN THE 00Z ECMWF DEPARTS

FROM THE SCRIPT AND USES SHORTWAVE ENERGY MOVING THROUGH WRN

CANADA TO KNOCK THE NRN PORTION OF THE REX BLOCK BACK INTO THE NE

PAC. BECAUSE OF THE ABOVE...HPC PRESSURES PROGS WERE PRIMARILY

BASED ON A 40/30/30 BLEND OF THE 00Z GFS/UKMET/ECMWF THROUGH SAT

BEFORE SWITCHING TO THE ECMWF ENSEMBLE MEAN DAYS 6/7 SUN/MON. THIS

ENSEMBLE MEAN ALONG WITH THE GEFS/NAEFS MEANS OFFER A LITTLE MORE

MID-UPPER LEVEL TROUGH AMPLITIDE/DIGGING THAN CORRESPONDING

DETERMINISTIC RUNS OVER THE CENTRAL US BY THEN THAT SEEMS

REASONABLE CONSIDERING UPSTREAM RIDGE AMPLITTUDE IS EXPECTED TO

REMAIN ENHANCED WITH APPROACH OF SEVERAL PAC SYSTEMS FORMERLY OF

TROPICAL ORIGIN AS TYPHOONS.

SENSIBLE WEATHER HIGHLIGHTS

===========================

THE INCREASING AMPLITUDE OF THE MID-CONTINENT TROUGH AND OVER THE

SW IS EXPECTED TO KEEP CONDITIONS COOL FROM THE INTERMOUNTAIN WEST

EWD THROUGH THE PLAINS AND EAST AS STANDARDIZED ANOMALIES WITHIN

THE 500MB HEIGHT AND 850MB TEMPERATURE FIELDS ARE EXPECTED TO BE

TWO SIGMAS BELOW AVERAGE...PARTICULARLY ACROSS THE PLAINS AND

MIDWEST. A CYCLONE LIFTING INTO ONTARIO THU COULD LEAD TO

COMMA-HEAD AND BACKSIDE LAKE-ENHANCED SNOWS INTO SAT. A SHORTWAVE

MOVING DOWN FROM WRN CANADA MAY ALSO INCREASE UPSLOPE FLOW AND

SNOW POTENTIAL SWD ACROSS THE N-CENTRAL HIGH PLAINS THROUGH LATE

WEEK. AS THE MOISTURE EJECTS EWD...RAINS SHOULD SPREAD FROM THE

CENTRAL PLAINS ACROSS THE MID-SOUTH THROUGH THE MID-ATLANTIC

STATES THIS WEEKEND. A POSSIBLE EARLY-SEASON CLIPPER SYSTEM COULD

BRING A SECOND CHANCE FOR SNOW TO THE UPPER MIDWEST SUN/MON.

MEANWHILE...MODERATE TO LOCALLY HEAVY RAINS MAY PERSIST FOR PARTS

OF FL AS A SUCCESSION OF FRONTAL BOUNDARIES TAP INTO MOISTURE FROM

THE WRN CARIBBEAN AND GULF OF MEXICO.

ROTH/SCHICHTEL.

http://www.hpc.ncep.noaa.gov/preepd/preepd.html

[IDO]

Yes it is clear that the upstream trough over the US will effect our weather for sometime (main synoptic pattern currently?). On the GFS 0z this trough is with us most of FI. It weakens and breaks the jetstream, promoting HP development in the UK area. GFS continually try to build a HP in from the Atlantic but with LP's never too far away it looks like changeable weather for the foreseeable.

Dare I say Autumnal weather in Autumn, a rarity of late.

After the frontal rain in the south on Friday, most models now suggest a settled HP weekend.

[lorenzo]

ECM and GFS looking quite different when reviewing for trends further out into October.

ECM GFS

CFS

Aberdeen ensembles shows scatter at around +132 / 144. Some disagreement within the runs.

NAEFS from last night goes with the HP at this range. Repeating signal for Mid-Atlantic ridge also.

Another trend on the NH view is the repeating Aleutian low, trigger point for the wave train ?

As for an arctic blast UKMO within next 72 hours give uppers of 0 at worst.. sarcastic Brrrr. Silly media.

[Gibby]

Good morning. Here's my look at the 00zs from GFS, UKMO and ECM.

All models show the UK under Low pressure to the North of Scotland with an unstable Westerly flow over all of the United Kingdom. Troughs of Low pressure are shown to push east in the flow, especially today and on Friday. So a very showery three to four days to come with some longer spells of rain as well, chiefly today and again in the South on Friday.

GFS then brings a High pressure area across Britain through Sunday and on East into Germany. A fine couple of days for Sunday and Monday before cloud and some rain moves into Western regions through Monday. Weakening troughs move slowly East across Britain midweek with some rain for all, heaviest in the North before High pressure ridges back across the UK in the second weekend with some more fine and Autumnal type weather for many.

The GFS Ensembles show a typical Autumnal changeable pattern with rain at times and temperatures athe surface near normal from uppers that are likewise. Most of the rain in the South falls later this week before it becomes rather less as we move into week 2. No unduly cold or warm trends are indicated this morning.

The Jet Stream pattern remains with the flow blowing close to Southern Britain for the time being. Longer term the flow splits and breaks up before a Northern arm strengthens blowing way north of the UK while the remains of a weak Southern arm continues to flow close to England.

UKMO at midnight on Monday shows High pressure over Germany with a Southerly flow over Britain. Eastern areas would likely stay dry and bright while the West clouds over with rain later as troughs advance in from off the Atlantic.

ECM looks decidedly Autumnal in its later stages this morning taking the High pressure quickly away early next week and bringing in increasingly deep and active Low pressure from the West meaning cool, wet and potentially stormy weather to all of the UK by the end of the run.

In Summary it looks like the weather next week is turning towards a more unsettled outcome than was originally being forecasted by some output. A High pressure of sorts is progged to affect us for 24-48hrs at the end of the weekend but it looks increasingly like being swept away as the Atlantic pushes Low pressure back in. ECM goes for a very stormy spell by the end of next week while GFS shows a much weaker Low pressure influence at the same time point going on to produce a decent High pressure for a while, though we are in deep FI by then. At least we can extend the similarities in the trend of the output towads the middle of next week this morning.

[jethro]

Gibby, can I just say thank you for your daily analysis. It's so clear and concise, even a model numpty like me can understand what the weather has in store for us, without your reports every morning I'd be lost. You're a star!

[Paul_1978]

Gibby, can I just say thank you for your daily analysis. It's so clear and concise, even a model numpty like me can understand what the weather has in store for us, without your reports every morning I'd be lost. You're a star!

Seconded!

[syed2878]

here here i agree.

[chionomaniac]

Then press the like button for Gibby's post all three of you!!!!

[jethro]

Then press the like button for Gibby's post all three of you!!!!

Sorry Chio, just thought a thank you was due.

[Gibby]

Many thanks to all of you for your kind comments. I'm just sorry I can't be around more in the daytimes to join in the discussion's that some of you engage in. However, I see no immediate reason why I shouldn't be able to keep these reports going through the winter months. If things get too mad on here and they get lost in the general mayhem of the winter fanaticals then unlike last year you can view them in isolation on my website...sorry for the plug. Once more thanks for the support.

Edited October 2, 2012 by Gibby

[Gavin Hannah]

Interesting high latitude profile...

Possible vortex splitting going on there? Or Not?

[AWD]

Pretty typical GFS 06z for October.

Looking like more of the same as what we currently have out the window, with some rain for all interspersed by drier and brighter spells with temps around average this week.

Next weekend is looking rather sunny and settled, although not overly warm.

The first half of next week does bring some warmer air into the equation, although at this stage, things turning more unsettled as next week progresses, with the worst of the rain/wind to the north.

Some cold air filtering down over the UK too. Pockets of negative uppers over the Midlands.

All in all, average weather for the next couple of weeks. All areas will see rain at times, all areas will see sun at times. A settled weekend does look favourable currently, after that as always, confidence drops away, although there is a decent enough signal for some sort of Mid Atlantic ridge developing from the GFS, how long it lasts is another question though.

[summer blizzard]

Possible vortex splitting going on there? Or Not?

Looks like more of a displacement to me, it would push what vortex there is south in the Atlantic as the high built over the pole.

[Glacier Point]

Classic cycling of the atmospheric circulation going on right now between GWO phases 2-3-4.

That's a strong Alaskan / NE Pacific ridge, distinctive eastern / central North American trough, and oscillating mid Atlantic ridge becoming flatter with alternating height rises over NE Scandinavia. Tendency in pressure over mainland Europe and North Africa to fall also, UK at risk of mid latitude highs and alternatibe troughs diving in from the NW.

That situation looks to continue for the foreseeable future. Main interest I think lies in the arctic air filtering southward through the two main trough axes over Canada and eastern Siberia. Shoud bolster snow cover in these areas...

Edited October 2, 2012 by Glacier Point

[phil nw.]

GFS12Z shows a temporary high moving in over the weekend which should give most of us a couple of fine days at least.

As GP has mentioned that cold upper trough spilling some early cold south over Canada and the USA in the next few days.

Some quite low daytime single figure max`s/close to freezing showing up right down to the southern states.

Illustrates quite well how quickly a continental landmass can cool even over areas much further south than our latitude.

Edited October 2, 2012 by phil n.warks.

[IDO]

Waiting for GFS Ens for 12z run in the hope its an abomination. Its a rain fest, a real treat for the ducks, and cool to boot. Here's hoping...

...a cold outlier it is. The ens has HP more influential so next week still ???

Edited October 2, 2012 by i'm dreaming of...

[cooling climate]

GFS12Z shows a temporary high moving in over the weekend which should give most of us a couple of fine days at least.

As GP has mentioned that cold upper trough spilling some early cold south over Canada and the USA in the next few days.

Some quite low daytime single figure max`s/close to freezing showing up right down to the southern states.

Illustrates quite well how quickly a continental landmass can cool even over areas much further south than our latitude.

I think you will find they are GMT times therefore we are talking about morning temps that

are being shown. Allowing for time differance t126 will give you the afternoon maximums.

[phil nw.]

I think you will find they are GMT times therefore we are talking about morning temps that

are being shown. Allowing for time differance t126 will give you the afternoon maximums.

Yup quite right CC it does pull those sub-zero `s further north somewhat by afternoon.Shows that i havent viewed the NAmerican charts for a while lol.

Still the main theme is that things are definitely cooling down over there with widespread frosts and single figure. max`s into the Northern states.

[Paul_1978]

Then press the like button for Gibby's post all three of you!!!!

I didn't realise the tick on an iPhone was "Like". I've done it now!

[Summer Sun]

A rather unsettled end to ECM tonight with some deep depressions covering all the UK

[Gibby]

Hi Folks. Here's my take on the 12zs from tonight GFS, UKMO and ECM taking a look at the GFS Ensemble mean and the Jet Stream along the way.

All models show another couple of days of showery Westerly wind over the UK with the most showers in the North and near Western coasts. As a weak and flat ridge crosses Thursday a dry day looks likely before a breakaway Low along a warm maritime air mass boundary rushes East across Southern Britain over Friday. With cold polar air to the North the mixing of these air masses could give some potent rainfall totals once more somewhere over the 36hr period from thursday night to Saturday morning. By Saturday a ridge of High pressure builds in temporarily from the West settling things down through the day.

GFS then shows another good day for Sunday before the High pressure cell moves away east into europe early in the week. southerly winds freshen and rain moves in from the West over Britain spreading relentlessy to all areas by midweek. Fi tonight shows a cold and unsettled setup as Low pressure slides SE repeatedly down over the UK with the British Isles lying on the cold side of the Jet with rain or showers in all areas in strong winds. It would be cold enough for snow on northern Hills as far South as Snowdonia at times with no let up in this theme at the end of the run.

The GFS Ensembles show the operational as expected to be a cold outlier in the latter part of the run which also shows it to be the wettest option in the South too. More likely is for 850's to deliver temperatures at the surface close to or a little below the norm with a changeable Atlantic theme continuing for all areas with rain at times.

The Jet Stream is currently expected to maintain its position roaring over Southern Britain and Northern France through the coming days before a new Northern arm takes precedence taking its flow well North of Britain while the Southern arm weakens and breaks up in 5-6 days.

UKMO for noon on Monday shows Low pressure centred over Britain with the fine weather of the weekend ebbed away and rain or showers falling in most areas through the day.

ECM too is not slow in removing the weekend High pressure and although it takes the incoming Atlantic Low further North than uKMO at 144hrs the net product is the same with wind and rain for all by Monday. Further on and towards the end of the run an intense and deep Autumn Low develops near Northern Britain with gale force Westerly winds and heavy rain sweeping East to be followed by rather cold and very showery weather for all with hail and thunder a distinct possibility.

In Summary tonight things look somewhat clearer from the big three tonight. The high pressure at the weekend is looking increasingly like a 36-48hrs affair with low pressure hot on its heels to take control of the UK weather early next week. Longer term and both GFS and ECM show some very turbulent Autumn conditions with rain and gales featuring highly in the output. With a SE moving Jet and the chance of the UK becoming on the cold side of it in FI it looks like things will be becoming rather chilly over the UK in a week or so time.

[tinybill]

i know i will get accused of cherry picking but deep f1 is looking good for the cold lovers so early i.e. like they said in one of the Sunday papers that winter could start 3 weeks early this year

[Polar Maritime]

i know i will get accused of cherry picking but deep f1 is looking good for the cold lovers so early i.e. like they said in one of the Sunday papers that winter could start 3 weeks early this year

Yes FI, But the GFS has been hinting this a few times over the last week. Something to keep an eye on with -3 and -4 uppers over the uk. And the Jet way South of the UK.

Edited October 2, 2012 by Polar Maritime

[blizzard81]

For next week, the models (more specifically the ECM) are showing something very similar (almost identical) to the synoptics

of early November 2009 with lows tracking on a south east trajectory through the British Isles and pressure gradually rising

to the north east. The great winter that followed didn't really kick in here until the 17th December. I wonder if the same sort

of thing happens this year but around 3 weeks earlier - say end of November!!

Edited October 2, 2012 by blizzard81

[phil nw.]

The difficulty in short term modelling caused by the lingering effects of Nadine are now receding with better agreement over the expected pattern developments in the next week/10days.

The 12z operationals are starting to trend in a similar way following the brief weekend High as the uncertainty`s clear.

As we go Into next week we see the pattern becoming more typically Autumnal with deeping low pressure moving across to the north of the UK bringing a colder feeling strong Westerly type flow with bands of rain and showers by the middle of next week.

The jetstream looks like reverting to it`s more southerly track again after a brief quieter period around the weekend.In this case there will quite a lot of Polar air in the mix with high level snowfall quite possible in the Scottish highlands at times.