Model Output Discussion; into 2015

[nick sussex]

Morning all

 

An early start for me today after another dismal nights sleep so I might be a bit grumpy today!

 

The overnight outputs generally show a mobile picture, within that there some differences in detail, some suggestion of a shallow low running east. It's looking marginal but there could be a little snow on the northern flank of this as it engages some colder air, the exact track though even if it verifies is likely to change.It's best of this stays a weak feature, less chance of any snow if this deepens too much.

 

However the ECM and UKMO disagree with that shallow low, so for the timebeing I'd say its a low risk.

 

Across all the outputs there are differences upstream which within the overall NH pattern won't dramatically change that although they will impact on any colder air into the UK.

 

You can see from this mornings NCEP  State update for New York why detail even at the weekend and early next week is difficult:

 

AS WE HEAD INTO NEXT WEEKEND...OUR FOCUS WILL THEN TURN BACK TO THE
SYNOPTIC SCALE AS ANOTHER DEVELOPING CUTTER-TYPE LOW PRESSURE SYSTEM
OVER TEXAS AND THE GULF COAST STATES LIFTS NORTHEASTWARD AND TOWARD
OUR REGION. WHILE THE MEDIUM RANGE GUIDANCE REMAINS IN GENERAL
AGREEMENT ON THIS OVERALL PATTERN...THERE IS ALSO MUCH DISAGREEMENT
ON THE FORWARD SPEED OF THIS SYSTEM AND EXACT TRACK IT WILL TAKE...
WITH THIS LIKELY ARISING FROM CONTINUED RUN-TO-RUN AND MODEL-
TO-MODEL VARIATIONS IN THE DEGREE OF PHASING BETWEEN THE INCIPIENT
PARENT SOUTHERN STREAM SHORTWAVE AND THE NORTHERN BRANCH OF THE JET
STREAM.

 

Developments there do effect the angle of the jet into the UK and also possible interactions with the PV to the northwest.

 

Briefly in terms of the strat we're seeing a first for this winter so far with a warming at the 10hpa level over Greenland, the models all vary in its intensity. So far any warmings have been on the Asian/Pacific side so I'm sure the strat thread might be a good port of call today!

 

 

 

 

[ICETAB]

GEFS ensemble 7 shows the type of pattern I want to see in the future. Perhaps it's the only one that has sniffed the projected warming up in the srat. I believe we will see allot more HLB come Wednesday of this week.

 

[IDO]

No change this morning. The D16 GEFS show nothing but zonality with at best a N/S split: 

 

Again any differences with the attempted ridging up to D10 has no effect on the long wave pattern, just introduces more TM air into the mix. The three main models at D10:

 

  

 

A good deal of certainty as to the general flow, just variations on timings and amplitude of short wave ridge and troughs. 

 

We await to see if the ECM's continued strat warming is verified and if it is then maybe another week of poor charts before it will get interesting. In the interim just average weather for the south:

 

 

At best a 15% chance of some of that PM air giving us some snow.

[Frosty.]

So let me get this straight, we have an 85 percent chance of not getting any more snow during first half of janvier..nooooooo

[nick sussex]

IDO the ECM's strat warming today is even stronger than last night so that's some good news.

[dragan]

So let me get this straight, we have an 85 percent chance of not getting any more snow during first half of janvier..nooooooo

How can you be so accurate?

[IDO]

IDO the ECM's strat warming today is even stronger than last night so that's some good news.

 

Yes certainly is but I always wait three runs when we get a big change before I believe it. If the 12z continues with that warming then confidence will be high.

 

So let me get this straight, we have an 85 percent chance of not getting any more snow during first half of janvier..nooooooo

 

I am sure your chances are better than that Frosty. 

 

35% (at best) of getting snow according to the latest run: 

Edited December 29, 2014 by i'm dreaming of...

[Frosty.]

How can you be so accurate?

I was quoting from the post above mine, that's all.

[Duane S.]

Mobilty from the models this morning but a lot of uncertainties within. None more so than member 7 of the GEFS (oh yes, shamelessly cherry picked) who tracks the low SE all the way into Southern Italy and the Arctic high then does noses over to see what's going on and it all ends up being, well, rather interesting to say the least...

 

 

We can but hope!

[IDO]

How can you be so accurate?

 

On the graphs I post at the bottom they have probability of snow. They are based on the ensembles that produce snow in what ever region (London in my case).

[nick sussex]

Yes certainly is but I always wait three runs when we get a big change before I believe it. If the 12z continues with that warming then confidence will be high.

 

 

I am sure your chances are better than that Frosty. 

IDO a question if indeed the GEFS go out further with suggestions that they might run to T720hrs in a few years  will you be using those or will you be sticking to just day 16? lol

 

In terms of the strat warming its likely to verify but just the extent of it that might move a little.

[IDO]

IDO a question if indeed the GEFS go out further with suggestions that they might run to T720hrs in a few years  will you be using those or will you be sticking to just day 16? lol

 

In terms of the strat warming its likely to verify but just the extent of it that might move a little.

 

Wow you have got me excited now, out to T720. When will that be? 

 

As I understood it last nights run ramped up the warming after the split was forecast where it had been rather mute on previous runs. This was unexpected and may be enough for a real run on the PV. Where as before we may have had to wait for another warming event to do the job.

[lorenzo]

Yes certainly is but I always wait three runs when we get a big change before I believe it. If the 12z continues with that warming then confidence will be high.

 

 

The trend has been slowly evolving since Xmas eve, GFS was the first model to pick up on the strength of the warming, before muting the signal slightly only for the ECM to grab the reigns and keep the momentum active.

 

Towards D 0 the modelling trend has been to increase the temp profile/ heat flux and build in the Greenland wave 2, which again the GFS sniffed out first. With GFS (P) and JMA on the case also, I think we can be confident in the development. It is the trop. response that I am keen to see and how effectively this pulls through into output.

[Smiler1709]

The way I see it is the next 5 to 7 days looked pretty sorted in terms of what we can expect from the weather, cool, rain or showers and abit windy at times, wouldn't get hung up to much about the ensembles showing anything past day 8. If a pattern change happens in the next week then the ensembles will come kicking and screaming after.

We're having some very decent cold weather at the moment, sometimes it's nice to start a fresh, go back to neutral for us which is westerly regime then hopefully let the next cold spell build and bring us something more interesting than we have now.

It's just a shame that normally we lose about two or more weeks of winter hunting for our next chance. But that's what you get when surrounded by warm waters.

[nick sussex]

Wow you have got me excited now, out to T720. When will that be? 

 

As I understood it last nights run ramped up the warming after the split was forecast where it had been rather mute on previous runs. This was unexpected and may be enough for a real run on the PV. Where as before we may have had to wait for another warming event to do the job.

If you start putting up GEFS charts for T720hrs then I really will be worried! lol The best thing about this strat warming is that its different from any so far this winter with it being over Greenland. I really hope this can finally dislodge those limpet low heights from Greenland and move the PV further away to the nw, that PV is now seriously getting on my wick!

Edited December 29, 2014 by nick sussex

[Frosty.]

P7 please with a cherry on top :-)

[dragan]

On the graphs I post at the bottom they have probability of snow. They are based on the ensembles that produce snow in what ever region (London in my case).

Thanks. I would say that ties in with my thoughts also.

[Penrith Snow]

The models are even worse this morning as we lose the colder PM shots on the ECM with pressure higher over Iberia linked to a huge high pressure covering most of the Med and North Africa from +120.

It's not quite a Bartlett but getting close to a zonal Bartlett so no snow even in the North apart from Scottish mountains and even here you will need 2000feet.

For the start of the New Year it's difficult to see how it could be worse.

Andy

[nick sussex]

The models are even worse this morning as we lose the colder PM shots on the ECM with pressure higher over Iberia linked to a huge high pressure covering most of the Med and North Africa from +120.

It's not quite a Bartlett but getting close to a zonal Bartlett so no snow even in the North apart from Scottish mountains and even here you will need 2000feet.

For the start of the New Year it's difficult to see how it could be worse.

Andy

You're obviously too young to remember winter 88/89! Compared to that winter this one so far is positively great! Theres little chance of the much feared horror Bartlett show setting up. Keep the faith we're not even in January yet and things can change very quickly. We shouldn't always assume the worst, its easy sometimes to fall into that trap because in the UK it can be a painful process to get some proper wintry weather in.

[dragan]

Yes, i agree with the above. The broader pattern seems to be fairly well established across the models. Although Scottish Mountains will see some wintriness, the ECM suggests even less so for other areas than yesterdays output.

Edited December 29, 2014 by dragan

[stratty]

The models are even worse this morning as we lose the colder PM shots on the ECM with pressure higher over Iberia linked to a huge high pressure covering most of the Med and North Africa from +120.

It's not quite a Bartlett but getting close to a zonal Bartlett so no snow even in the North apart from Scottish mountains and even here you will need 2000feet.

For the start of the New Year it's difficult to see how it could be worse.

Andy

 

.......................also regular LPs and the angle they are coming into the country in the latter part from the GFS 00z run would be reminiscent of last years flooding 

 

 

......................hopefully a one off!

Edited December 29, 2014 by stratty

[mushymanrob]

looks this morning like the jets shifted further north, meaning we look like getting slightly more tm sectors and less pm in the forthcoming unsettled spell.

as for instinct (something i too have employed) , in reality so far this winter no ones instinct for something cold has become reality. TEITS even apologised for getting it wrong just the other day... respect. before crimbo there was the jh science vs omm instinct debate..... clearly the scientific method has proven correct? of course theres no recording of instinct based predictions, maybe there should be in some way, but imho instinct often is misplaced unless anyone can provide evidence to the contrary (as in an instinctual prediction followed by subsequent charts that proved it right).

....and just for the record, my instincts dont suggest to me a major cold winter, but i do think we will get a widerspread cold snap (upto a week) where snow and frost feature. thats based on past experiences and the 'feel' i get from the way this winters pattern is playing out.

[Gibby]

HERE IS MY LATEST ANALYSIS FROM THE OUTPUTS OF THE WEATHER COMPUTER PREDICTION MODELS FOR TWO WEEKS FROM 8AM TODAY MONDAY DECEMBER 29TH 2014.

NEXT UPDATE TUESDAY DECEMBER 30TH 08:00

THE CURRENT GENERAL SITUATION A large and intense Winter High pressure area will slip slowly SE over Southern Britain today with a slowly freshening SW flow developing over Northern Britain tonight and tomorrow.

MODELS-2 WEEK HEADLINE Becoming unsettled and windy later this week and onward with rain or showers at times and snow on Northern hills. Some drier periods likely in the South.

THE JET STREAM ENSEMBLE FORECAST The Jet Stream Forecast shows the flow ridging North over the UK currently. It then becomes strong and flows from West to East across a point close to 50deg North for the remainder of the period

GFS OPERATIONAL The GFS operational this morning shows High pressure collapsing SE into NW Europe over the next day or two with a freshening and less cold Westerly flow developing across the UK. Within this flow is shown various periods of wind and rain from troughs crossing East in the flow attached to Low pressure persistently to the North and these then alternate with somewhat colder and more showery weather with some wintry showers over the North. Overall temperatures are shown close to average with some brief somewhat colder interludes with strong winds in places at times.

THE GFS PARALLEL RUN The Parallel run is very similar to the operational this morning in overall pattern with differences in specifics from day to day especially later when a period of very volatile weather is shown with severe gales and heavy rain as deep Low pressure areas crash into the UK from the Atlantic.

THE GFS CONTROL The GFS control run also shows a strongly zonal pattern under Westerly winds developing for the North by midweek and to all areas by next weekend with strong winds and rain at times for all through the second half of the period in average temperatures or a little above at times apart from brief colder interludes at times in the North and some drier periods across the South as High pressure over France remains close by at times.

THE GEFS ENSEMBLES The GFS Ensembles show strong support for a Westerly flow to dominate the UK from later this week. With Low pressure biased to lie to the North and High near the Azores Westerly winds, strong at times will follow their normal characteristics of spells of wind and rain for all with slightly colder and more showery interludes in between, these most prolific across the North.

UKMO UKMO shows the High pressure and attendant cold weather receding away from the SE through the New Year period replacing it with stronger but milder SW winds and a spell of rain as a cold front is shown to move SE followed by another strong rise of pressure from the SW with frost returning as colder conditions develop later at least for next weekend away from the far SW where cloud may be more prolific and a few showers affect North Sea coasts in a NW flow.

THE FAX CHARTS The Fax Charts follow the raw data quite well today with a milder SW flow replacing the cold High across Southern Britain over the New Year. A cold front in the stronger SW flow will clear SE by the weekend with a strong rise of pressure moving back in from the West with frost at night developing again over the weekend at least for a time.

GEM GEM today also shows High pressure moving away SE with milder SW winds ahead of a cold front taking hold over the festive celebration period. Into the New Year a ridge of High pressure returns a few nights when frost is likely before the pattern flattens under Westerly winds and rain at times in generally milder conditions as we move into next week.

NAVGEM NAVGEM also shows the well worn track between the models recently of replacing High pressure with a milder Westerly flow between High pressure to the South and Low to the North with rain at times with some brief drier and chillier days in between.

ECM ECM this morning shows the current High pressure moving away to the South with a freshening SW flow ahead of a cold front later in the week bringing some rain. A cooler spell is possible again at the weekend in a rather complex pressure pattern across the UK with slacker winds and variable conditions as troughs get hung up across the South. Then through next week the pattern simplifies into a relatively mildish and windy period with rain at times especially in the North and West.

ECM 10 DAY MEAN The ECM 10 Day Mean Chart shows Low pressure to the North and High well to the South the most likely scenario at Day 10. This would indicate a strong Westerly flow veering WNW at times with spells of rain mixed in with colder and more showery conditions.

NOTABLE TREND CHANGES FROM PREVIOUS RUNS The trend this morning remains strongly in flavour of Westerly winds over the period with spells of wind and rain alternating with colder periods. A few models have leaned to another brief but strong ridge of High pressure for a time this coming weekend.

MY THOUGHTS The models continue to hold resolute in maintaining a general Westerly pattern of winds across the UK blowing between deep Low pressure to the North and High pressure to the South. The details of day to day conditions are hard to distinguish this morning with some output indicating some deeply unsettled weather later with svere gales and heavy showers plus colder wintry showery periods while others hold or bring High pressure closer towards Southern Britain at times sending the worst of the wind and rain towards the North and West while allowing some rather milder conditions into the South at times. However, these are just small nuances in an overall flat pattern of weather which sees the UK saved from any major cold incursions over the next few weeks at least. There is a hint that this weekend will bring a window of chilly and perhaps frosty weather for a day or two as another strong ridge attached to High pressure to the South and SW moves through but with a weak trough close to the South cloud could restrict night time frosts to more Northern and Eastern areas before all parts fall back into the Westerly regime soon afterwards and through next week. The Azores High remains the nemesis for our failure to lock into any lengthy and meaningful cold across the UK both in the past and the near future. The Jet flow riding across the Atlantic on the Northern flank of this High remains poorly aligned to play ball for cold weather to be other than passing shots as ridges between the Lows to the North pass by. There is still little evidence that there is a quick end to this pattern through January from the model output today though being the time of year it is things can and have changed quite quickly in the past but like waiting for a bus we are going to have to continue to be patient.

[Penrith Snow]

You're obviously too young to remember winter 88/89! Compared to that winter this one so far is positively great! Theres little chance of the much feared horror Bartlett show setting up. Keep the faith we're not even in January yet and things can change very quickly. We shouldn't always assume the worst, its easy sometimes to fall into that trap because in the UK it can be a painful process to get some proper wintry weather in.

Not too young I am 53 and remember the 1989 horror, however, I also remember the lovely widespread snowfall in late November 1988 that was followed by a week of frost.

So to me so far winter 2014/15 has been worse!

Plenty of time for change but at the moment despite all the techno chat nothing is on the horizon.

Andy

[nick sussex]

In terms of the shorter term there is a cluster of solutions on the ECM postage stamps that back the GFS's in terms of a low pressure crossing on a fairly southerly track:

 

 

Theres still quite a variation in terms of how far south any colder air gets at T120hrs.

 

Regarding that low theres not any deep cold air to tap into but if the feature remains shallow evaporative cooling might help.

 

The operationals disagree regarding that low so for the timebeing I'd put this as a low probability but certainly something to keep an eye on.

Edited December 29, 2014 by nick sussex