Model Output Discussion - The Start Of Winter

[Geordiesnow]

I never said it wasn't model discussion?

 

In my opinion the CFS 1 month is pointless, I very much doubt the Met Office pay it the scantest regard.

 

For me personally, I don't pay much interest in long range forecasting regardless what it shows because at the end of the day, its what the models show in the here and now is what matters.

 

I think people get too hung drawn and quartered about what models show in the long term really because the weather is just way to variable to even get drawn on what the models are showing as they are subject to change nearly every day. 

 

If you get all the right building blocks in place, it really does not take long for a cold set up to form, so even if you have to wait right until February for it, then so be it.

[johnholmes]

I know you love those anomaly charts so yes why not .  Sometimes trying to get cold into the UK is like pulling teeth so its very natural to be more interested in colder synoptics at this time of year.

 

It's the same in summer with extreme heat, I think because of the UK's temperate climate people are always drawn to the extremes.

 

I'll have a go over the weekend if they seem to offer any sensible possibilities but it will have to be as a pdf so sorry in advance to those who are unable to open these.

[IDO]

Interesting post, but you're talking Day 16 here - that's a long long way off. I don't think there's any need for those looking for cold to be overly concerned at that range.

I do tend to look at FI for trends and the GFS have been solid for days for a mobile PV, away from the NE. It was also showing the upcoming week 1 signature developing last week and picked up this incoming Atlantic LP system 10 plus days out. Now I am trying to search for strong clusters as to what happens after the PV migration. Knowing the back story can keep you away from making too much of the smaller scale transient amplification the op runs sometimes throw up, as the bigger picture will guide you in the long wave direction. Much like the anomaly charts Dr John Holmes uses.

Edited December 4, 2014 by i'm dreaming of...

[Long haul to mild]

With respect, no it isn't......it's model discussion even if it's out in T1000's.....Many members use the CFS for possible trend spotting....If it was a waste of time then no-one would even pay it the scantest regard

If I recall correctly,the CFS and its insistence on a cold and blocked December in 2013 was one of the drivers behind those ridiculous "100 days of snow" headlines that were so spectacularly wrong. So let's discuss it by all means but it's not got a good track record and that's hardly a surprise given that most models struggle beyond seven days.

Too much doom and gloom on here in my opinion; December rarely delivers much in the way of snow for the UK with a few notable exceptions. Loads of time still; winter is only four days old!

The charts are different to this time last year, more PM incursions this time around, which often have far more potential to lead to something better down the line. I think the horror of last winter has got to people; more patience is needed.

This chart looks pretty cold to me; not the big freeze that many are waiting for, but it's not mild mush SW'lys either and that's promising I think.

Edited December 4, 2014 by Long haul to mild

[johnholmes]

the GEFS are interesting through week two with the expected evacuation of low heights from arctic canada continuing. very few members have any notable vortex segment south of 70N, nor any meaningful dperessions at all. should we arrive at this scenario, i would expect that our azores/atlantic high would retrogress by the end of week 3. of course, the canadian vortex may prove to be more resilient than this. we shall see. 

 

ba can you please put in basic weather language what the bit highlighted means please - thanks?

[ukpaul]

ba can you please put in basic weather language what the bit highlighted means please - thanks?

 

I presume it means that high pressure builds further north into Arctic Canada. 

[Gael_Force]

I would not get carried away with the "beat up PV". It could survive sometime like that, just meandering around, and the mid latitude pattern could still remain rather flat. We need some sort of trigger to expedite some HLB'ing. The MJO signal would have provided this when it was suggesting high amplitude phase 6 and 7. The current update from CFS continues to move away from that:

 

realtimemjo (1).png

 

For instance the CFS daily right through to mid January keeps a disrupted PV with no sign of a HLB till right out on 18th January when a Pacific ridge forms:

 

cfsnh-0-1074.png

 

So we really need an SSW to make use of such  a NH profile. It would indeed be a game changer (for the right places). As it stands the CFS shows mobile PV lobes for the next 6 weeks keeping any fledging height rises at bay. This is the background signal that I suspect the models, including the DJF UKMO update, are picking up. IMO we are therefore just waiting for a trigger. Any ideas?

 

Hi IDO, your MJO grapic, although correctly dated, is way out of sync. The GEFS are currently in phase 5 and not 3 as depicted ie, well past the forecast point of entry to the COD.

 

[Summer Sun]

Latest snow accumulation chart shows the potential for a dusting of snow over Dartmoor in the next 3 to 6 days

 

 

200m + in western Scotland should get a decent covering with up-to 10 inches in places

[Mapantz]

Latest snow accumulation chart shows the potential for a dusting of snow over Dartmoor in the next 3 to 6 days

 

 

200m + in western Scotland should get a decent covering with up-to 10 inches in places

The scale is in cm on that site. ;p

[IDO]

Hi IDO, your MJO grapic, although correctly dated, is way out of sync. The GEFS are currently in phase 5 and not 3 as depicted ie, well past the forecast point of entry to the COD.

 

It's the CFS and is based on a different measurement. It uses the Wheeler and Hendon 2004 RMM rather than the WH04 so the starting point will be different as well as the projected route. I find this gives a clearer picture.

[Gael_Force]

It's the CFS and is based on a different measurement. It uses the Wheeler and Hendon 2004 RMM rather than the WH04 so the starting point will be different as well as the projected route. I find this gives a clearer picture.

 

Thanks, wondered why the big discrepancy.

[Froze were the Days]

Exactly the point I was making yesterday. Where will the trigger SSW come from if the MJO refuses to play ball? (ok still possible but less likely). We could find ourselves looking at a groundhog day scenario over the next 6 weeks...not particularly cold, wet or anything. Fun fun! Not!

RE the CFS, I had noticed that the HLB signal for January had disappeared over the past week (to be replaced with something akin to what we have now). I wonder if this is the reason?

A month or two back I said that by the middle of December the early winter pattern would probably be set or at least set in motion. I'm not seeing anything in any NWP at present which leads me to believe the UKMO are wrong in sticking by their long range seasonal model. Will this change? Well it could do but the further into December we go, the more of winter we're eating up.

Totally agree - noticed the CFS has become more and more zonal over the last week or so re: end of December and January with similar conditions (as you state) to next week with Azores high ever present in one form or another, slightly more amplified at times.

 

Anybody notice over the last year or so how our synoptic patterns become somewhat 'locked' for at least a month. This weekend looks like the start of a new phase and would be surprised if it changes greatly going into January.

[Summer Sun]

The scale is in cm on that site. ;p

 

I know it is, the Orange covers up-to 25cm which is just over 9 inches however we don't know how heavy and prolonged the precipitation may be yet Sunday into Monday so thats why I've said up-to 10 inches. The met office are going for up-to 7 inches above 200m at this stage

 

[bluearmy]

ba can you please put in basic weather language what the bit highlighted means please - thanks?

There are hardly any gefs members by day 16 which have any low heights across arctic Canada below 70N. I take this as quite unusual. It has been forecast by the extended ens and remains so.

[LomondSnowstorm]

I do hate quoting twitter on here but it does have charts on the ECM extended Ens

https://twitter.com/MattHugo81/status/540611151743426560

"Tropospherically and stratospherically something is brewing & 12z EC ENS clusters by 19th are very interesting indeed"

 

 

In the shorter term, a mean low of 965mb at +144 so close to the British Isles is quite impressive, as is the upper cold pool, and the mean trough basically fills just east of the meridian with a mean NWerly flow:

     

[MR EXTREMES]

certainly some interest tonight once again as there is an indication the the flabby battered vortex is ready to move home also some good height rises into the united states with indications of heights building up into southern tip of greenland of coarse we need the vortex to move on although slow there is without a doubt movement of the fragmented vortex.

 

to be honest im getting sick of the word vortex but not sick of a weakened and flabby fragments of a vortex.

 

anyway for most of this week models have suggested tweaks to the overall northern hemispheric pattern although slow and still in fi.

but i notice the gefs has thrown up the ideas so we have two out of 3 main models suggesting this firstly the ecm and the gefs hopefully they will now build on this threw the weekend.

 

even so -6 850s snow wind rain sleet hail kitchen sink but typical pattern of the great uk british weather type.

 

overall there is changes being shown i suspect anything more exciting for other parts of the uk will be after christmas and most certainly could set up a wintry jan.

although it dont matter right now because its only the start of winter.

 

couple of charts to build on tonight for future developments.

 

although the ao looks to be positive but slips down around the 16th dec of coarse lots could change by then either up wards or down but at the moment its going with the models suggesting more of a downwards trend.

mjo looks a little stuck right now but nothing truely exciting just yet although cant complain with the snow forecast for some and in any case early days.

these are close to phase 8 - 1

and of coarse the el nino outlook still has uncertainties 

 

PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300PM EST SUNDAY NOV 30 2014

30-DAY OUTLOOK DISCUSSION FOR DECEMBER 2014

THE DECEMBER 2014 OUTLOOK REMAINS CHALLENGING, THOUGH FOR SOMEWHAT DIFFERENT
REASONS THAT THOSE DISCUSSED BELOW FOR THE 0.5 MONTH LEAD OUTLOOK. A DRAMATIC
PATTERN CHANGE IS ANTICIPATED ACROSS THE NORTH-CENTRAL CONUS, WHERE MUCH
BELOW-NORMAL TEMPERATURES FOR THE FIRST COUPLE DAYS OF THE MONTH ARE FORECAST
TO BE REPLACED BY ABOVE-NORMAL TEMPERATURES THROUGH AT LEAST THE SECOND WEEK OF
THE MONTH. A SIMILAR SITUATION IS FORECAST FOR THE NORTHEAST, WHERE A SERIES OF
CANADIAN HIGHS ARE FORECAST TO DOMINATE SURFACE CLIMATE EARLY. THE ARCTIC AIR
IN CANADA EARLY IN THE PERIOD IS THUS EXPECTED TO PROGRESS MORE EAST THAN
SOUTH, AS A +NAO CIRCULATION IS EXPECTED EARLY IN MONTH. THIS LEAVES AREAS TO
THE SOUTH MILDER THAN CLIMATOLOGY FOR MOST OF THE FIRST 10 DAYS OF THE MONTH OR
SO.

IN THE MEDIUM RANGE PERIOD, THE MODELS ARE IN GOOD AGREEMENT THAT AN ANOMALOUS
TROUGH WILL FORM IN THE NORTH PACIFIC, THOUGH THERE IS SOME DISAGREEMENT AS TO
ITS LONGITUDINAL CENTER. THE GLOBAL ENSEMBLE MEANS INDICATE A FAIRLY LONG
WAVELENGTH PATTERN, APPEARING AS A HYBRID OF THE CANONICAL +PNA AND
LOW-FREQUENCY ENSO FOOTPRINT. THE LATTER REMAINS SUSPECT AS THE EXPECTED
CONVECTIVE RESPONSE TO EL NINO IN THE CENTRAL PACIFIC REMAINS TENUOUS.

THE MJO HAS REMAINED ACTIVE OVER THE PAST TWO WEEKS, AND IS FORECAST TO
PROPAGATE INTO THE PACIFIC OVER THE NEXT WEEK TO 10 DAYS. THIS FAVORS A COLDER
SOLUTION RELATIVE TO NORMAL ACROSS MUCH OF THE CENTRAL AND EASTERN CONUS FOR
THE LAST 10 TO 15 DAYS OF THE MONTH.

COMBINING THE ABOVE FACTORS WITH UNANIMOUS MODEL AGREEMENT AMONG THE EXTENDED
RANGE ECMWF, CFS, AND JMA, A WARMER-THAN-NORMAL DECEMBER FOR MUCH OF THE CONUS
AND ALASKA IS FAVORED. SOME BELOW-NORMAL TEMPERATURES ARE FAVORED ALONG THE
GULF COAST WHERE A +PNA HAS A STRONG TEMPERATURE FOOTPRINT, AND WHERE ANY
PATTERN CHANGE LATE IN THE MONTH WOULD CONTRIBUTE TO BELOW-NORMAL TEMPERATURES.
PROBABILITIES ARE GENERALLY LOW, HOWEVER, REFLECTING THE MIDDLE AND LATE MONTH
UNCERTAINTY, GIVEN THE MJO SIGNAL FOR A PATTERN CHANGE.

THE PRECIPITATION OUTLOOK IS CHANGED TO REFLECT THE CHANGES IN MODEL GUIDANCE
FROM THE ECMWF, CFS, AND JMA, AS WELL AS TO HARVEST THE HIGH CONFIDENCE
SHORT-RANGE FORECASTS FOR THE NEXT SEVERAL DAYS. COMBINING THESE FACTORS WITH
THE WEEK-2 OUTLOOK INFORMS THE PRECIPITATION OUTLOOK FOR THE MONTH. EQUAL
CHANCES ARE INDICATED OVER MUCH OF THE EASTERN CONUS, WHERE PRECIPITATION
SIGNALS ARE WEAK EARLY IN THE MONTH. IN THE SOUTHEAST, THOUGH BELOW-MEDIAN
PRECIPITATION IS FAVORED FOR THE FIRST 10 DAYS OF THE MONTH, THE MJO AND ANY
LOW-FREQUENCY ENSO SIGNAL FAVOR NEAR- TO ABOVE-MEDIAN PRECIPITATION LATER IN
THE MONTH.

THE PREVIOUS DISCUSSION, ISSUED NOVEMBER 20, FOLLOWS:

THE OUTLOOK FOR DECEMBER 2014 IS DECIDEDLY UNCERTAIN AT THIS POINT. THERE ARE
SEVERAL COMPETING INFLUENCES THAT ARE YET TO BE CLEARLY RESOLVED IN EITHER THE
STATISTICAL OR DYNAMICAL TOOLS.

LET'S FIRST BEGIN WITH THE DYNAMICAL MODEL GUIDANCE. MONTHLY FORECASTS FROM THE
NMME AND IMME ARE FAIRLY MILD ACROSS MUCH OF THE CONUS, ESPECIALLY THE NORTHERN
AND WESTERN PORTIONS. THIS IS A REASONABLE SOLUTION GIVEN THE GENERAL WARM ENSO
SIGNAL. HOWEVER, THERE IS LITTLE INDICATION THAT A ROBUST ENSO RESPONSE IN THE
EXTRATROPICS CAN BE SUSTAINED ABSENT SOME REASONABLY CANONICAL EQUATORIAL
CONVECTIVE ANOMALIES CONSISTENT WITH AN EL NINO. CURRENTLY, THE CONVECTIVE
STATE OF THE EQUATORIAL PACIFIC IS SOMEWHAT INCONSISTENT WITH WHAT WOULD
OTHERWISE BE EXPECTED. SO IN THIS SENSE, MODEL GUIDANCE INITIALIZED WEEKS AGO
THAT INDICATE AN ENSO-LIKE FOOTPRINT OVER NORTH AMERICA ARE SOMEWHAT SUSPECT.
ADDING TO THE UNCERTAINTY IS THE FACT THAT MORE RECENT GUIDANCE FROM THE CFS
AND ECMWF THAT EXTENDS AT LEAST THROUGH THE MIDDLE OF DECEMBER INDICATES A
DIFFERENT PATTERN FOR THE FIRST TWO WEEKS OF THE MONTH, WITH ABOVE-NORMAL
TEMPERATURES CENTERED IN THE EASTERN CONUS (WITH THE CFS WARMER THAN THE
ECMWF), AND NEAR- TO BELOW-NORMAL TEMPERATURES CENTERED OVER PARTS OF THE WEST.
THIS LATER GUIDANCE IS SLIGHTLY PREFERRED, BUT THE TYPICAL LOW FORECAST SKILL
IS UNDERSTOOD.

THE CURRENT AND FORECAST STATE OF THE MJO MAY HAVE SOME IMPLICATIONS FOR THE
MONTHLY FORECAST. THIS, TOO, IS UNCERTAIN SINCE THERE DOES NOT SEEM TO BE A
STRONG ATMOSPHERIC RESPONSE IN THE SUBTROPICS YET, CASTING DOUBT ON WHETHER THE
ONGOING EVENT WILL SUBSTANTIALLY MODULATE NORTH AMERICAN CLIMATE. SHOULD A
ROBUST MJO PROPAGATE FROM THE INDIAN OCEAN TO THE PACIFIC, THE RESPONSE LATER
IN THE MONTH COULD BALANCE OUT A WARMER SIGNAL INDICATED EARLY BY THE FORECAST
EVOLUTION OVER THE NEXT WEEK OR TWO.

FINALLY, THERE ARE SIGNS IN THE CURRENT MEDIUM RANGE GUIDANCE THAT RELOADING OF
ANOMALOUSLY COLD AIR IN WESTERN CANADA COULD OCCUR BY LATE NOVEMBER. THIS IS
BEST SUPPORTED BY THE LATEST CANADIAN AND ECMWF ENSEMBLE AND DETERMINISTIC
GUIDANCE. SUCH A SCENARIO CASTS MORE DOUBT ON THE WARM ENSO RESPONSE OVER
SOUTHERN CANADA AND THE NORTHERN CONUS.

IN LIGHT OF THE AFOREMENTIONED DISCUSSION, THERE IS RELATIVELY LITTLE COVERAGE
ON THE 0.5 LEAD MONTHLY TEMPERATURE MAP. ABOVE-NORMAL TEMPERATURES ARE FAVORED
FOR THE IMMEDIATE WEST COAST BASED ON GOOD MODEL CONSENSUS AND STATISTICAL
GUIDANCE BASED ON PACIFIC SSTS. UNCERTAINTY INCREASES IN THE PACIFIC NORTHWEST
SOMEWHAT. ABOVE-NORMAL TEMPERATURES ARE FAVORED IN THE NORTHEASTERN CONUS AT
THE INTERSECTION OF SIGNALS FROM ENSO, MJO, AND RECENT MODEL GUIDANCE.
CONFIDENCE HERE IS STILL FAIRLY LOW AS INDICATED BY MEAGER PROBABILITIES.
BELOW-NORMAL TEMPERATURES ARE WEAKLY FAVORED FOR THE SOUTH-CENTRAL CONUS WHERE
THE ENSO SIGNAL IS STRONGEST AND THERE IS MORE SUPPORT FROM MODEL GUIDANCE. THE
NORTHWARD EXTENSION IS BASED ON THE DISTINCT POSSIBILITY THAT ANOTHER ARCTIC
AIRMASS MOVES SOUTHWARD EAST OF THE ROCKIES EARLY IN THE MONTH. IF THIS OCCURS,
EVEN AN EMERGENCE OF A STATIONARY ENSO SIGNAL LATER IN THE MONTH WOULD STILL
NOT UNDO THE ODDS FOR BELOW-NORMAL TEMPERATURES OVER THE INDICATED REGION.

FOR PRECIPITATION, A GENERAL CONSENSUS OF ENSO IMPACTS AND MODEL GUIDANCE IS
USED, WITH LOW PROBABILITIES INDICATING THE LOW CONFIDENCE IN LIGHT OF THE
ABOVE FACTORS. IF ROBUST MJO IMPACTS ARE REALIZED EARLY IN THE MONTH,
ABOVE-MEDIAN PRECIPITATION MIGHT EXTEND FARTHER NORTH INTO PARTS OF THE OHIO
VALLEY AT THE EXPENSE OF RAINFALL NEAR THE GULF COAST. UNCERTAINTY IS ALSO
ESPECIALLY HIGH OVER THE PACIFIC NORTHWEST, WHERE THERE ARE MULTIPLE
CONFLICTING SIGNALS.

[Man With Beard]

http://www.cpc.ncep.noaa.gov/products/predictions/814day/500mb.php

 

Massive positive anomaly at 500Hpa building up in Canada. Suggests to me some sort of high pressure in the vicinity - which would mean Arctic cold being directed through into the North Atlantic

[bluearmy]

It is odd that the cluster tweeted by matt is at odds with the same model mean/anomoly. given NOAA CPC and NAEFS at the same timeframe, one would have to question the likelihood of that cluster being close to reality re the biscay low. The only thing that seems reasonable on that cluster is the extension west of the Siberian ridge. anyway, as ever, time will tell!

[Cloud 10]

http://www.cpc.ncep.noaa.gov/products/predictions/814day/500mb.php

 

Massive positive anomaly at 500Hpa building up in Canada. Suggests to me some sort of high pressure in the vicinity - which would mean Arctic cold being directed through into the North Atlantic

 

 

Its the same story at 850 Hpa over that region,hence our downstream fairly potent blasts of PM air look set to continue.

 

[Penrith Snow]

Good ECM run, if I can't have deep cold easterlies and northerlies this is my second best winter weather set up with fast moving depressions pulling in cold polar air as they pass to the east of the UK before the next depression turns things temporarily milder as the warm sector comes through.

This leads to some very interesting weather with gales, sleet, snow, rain, sunshine, frost, just about every element and sometimes on the same day! You can't be interested in the weather and not enjoy that.

Ok I appreciate I am looking at this from a Cumbria prospective and conditions will not be as varied in Central London.

My only concern is that such cool zonal spells tend to be followed by a longer spell of milder westerly winds as the Atlantic high pressure moves into Biscay and this seems to be happening at +240, but that's a long way off and there is plenty of great weather to come in the meantime.

Andy

[Matty M]

Look at this 12z GEFS member!

 

[Bonjangle]

Look at this 12z GEFS member!

 

Scary is the only word for that .

[BlueHedgehog074]

Look at this 12z GEFS member!

 

I think we would be blown out of the Galaxy if that monster Low reached the UK like that... :O 

 

Either way, some sort of stormy Low Pressure system still looks possible for the middle of next week.

Edited December 4, 2014 by DiagonalRedLine

[johnholmes]

There are hardly any gefs members by day 16 which have any low heights across arctic Canada below 70N. I take this as quite unusual. It has been forecast by the extended ens and remains so.

thanks but what is the term expected evacuation of low heights mean, not being awkward I just do not understand that phrase?

[Mair Snaw]

Look at this 12z GEFS member!

 

if that came close to verifying and hit the uk I think anything that wasn't nailed down would end up in Norway...