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Paul

Model Output Discussion - Stormy Period Inbound...

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Anyone? :)

 

It's unstable, and people will get snow if the charts were correct as of right now. It's too far out though for detail.

Edited by Dr. Astro

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The GFS P hasn't even been properly launched and its getting on my nerves already. Now stopped at T72hrs, what is going at NCEP?

 

Yes and just when we have interesting charts the 06z GFS op was its last run ever :angry:

 

The GFS Control is similar to the op at D6: post-14819-0-37223100-1421234002_thumb.p

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It's unstable, and people will get snow if the charts were correct as of right now. It's too far out though for detail.

Thank you! Something akin to 09/10 would be nice especially from an IMBY perspective. Bring It On!

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The GFS P hasn't even been properly launched and its getting on my nerves already. Now stopped at T72hrs, what is going at NCEP?

 

I did post about this last night - but it's because they've started the process of upgrading the parallel to be operational and are having to manually load the parallel files for now - this'll be the final run that the para runs on, as it replaces the operational as of the 12z. Incidentally, expect the new version to be about 20 minutes later than the current one approx. 

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Anyone? :)

 

Well, a bit of both, some cold dry weather but also a risk of snow - given areas of low pressure will be dropping SE across the UK. It doesn't have to be one or the other.

 

Tuesday/Weds sees a risk of snow spreading SE on 06z GFS op across many areas as shallow low pressure(s) drop SE over western UK, likely to change in detail from those charts quite a bit unfortunately this far off, but shows what kind of cold spell we are getting into, by no means cold and dry all the time:

 

post-1052-0-23985500-1421234413_thumb.gipost-1052-0-03735100-1421234426_thumb.gipost-1052-0-68200700-1421234445_thumb.gi

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The GFS P allows for more frontal snow: post-14819-0-00926200-1421234841_thumb.p

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Gfs parallel the same!! Slightly deeper low at 168 hours but the theme is the same!!

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One change that has been gathering pace is the deeper low centred near the ne USA. Originally we saw a shallower feature there and over time this has been deepened.

 

The track of this and speed is important down stream, you can see it gets close to the low near Iceland but the GFS P still manages to drop this south.

 

I would say that if theres any westwards corrections with a shallower feature dropping south from Iceland that significant snow is likely to fall on the eastern flank of that, if things go well then an easterly will set in.

 

It's the best synoptics for nearly two years and even better that this moved quickly into the T144hrs timeframes rather than subjecting us to some nervewracking countdown from T240hrs plus.

 

So overall we've got a solid signal for some cold and snow upto day 7, however to get over the line in terms of a future ne/e flow I think we need a few more runs for that because of that upstream low over the ne USA, we need the Azores ridge to remain sufficiently amplified at the key timeframe.

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Only snow for Midlands north, us in the south would continue with the theme of cold rain

 

Way out to be discussing snow detail, But the synoptic ido shows would produce Snow for the South.

 

162-574UK.GIF?14-6

Edited by Polar Maritime

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Perhaps the weather wants to celebrate the 70th anniversary of the winter of 1947 early!  :cold:  :friends:  It was around this time in January that things started getting interesting http://www.meteociel.fr/modeles/archives/archives.php?day=23&month=1&year=1947&hour=0&map=0&mode=0  :spiteful:  ;)

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Only snow for Midlands north, us in the south would continue with the theme of cold rain

Its too far out to be sure of where the frontal snow might be, I'd advise people to not get hung up on the GFS snow charts or any predictions for snow at that range.

 

This is likely to lead to an emotional rollercoaster and possible sedation! lol I understand your concerns Smiler but until we get closer in and the depth and track of the drop down low are agreed on then theres no way of knowing where the snow band might be.

 

The thing to look out for is the shape of the low so you want a more elongated shallow low.

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Just to highlight the uncertainty comparing the GFS op and Control at T288:

 

post-14819-0-09387900-1421235598_thumb.p  post-14819-0-71562500-1421235598_thumb.p

 

Both are cold but the GFS P has 2-3 potential snow events where as the Control is a lot drier. Looking at the GEFS at that time frame and it is clear the hi-res has very little support at that range with the majority cluster showing a return to a more zonal flow:

 

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=288

 

So maybe treat the GFS 06z hi res runs after D10 with caution (probably a good mantra in any case)!

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Only snow for Midlands north, us in the south would continue with the theme of cold rain

 

Not with upper air temps that low I wouldn't have thought. The -5 850hPa is pretty much clear of the isles the whole of that segment of run, and that's always the litmus test especially with the dew points given. The GFS itself doesn't agree with you either: their Snow Risk charts are usually surprisingly accurate in terms of the type of ppn:

 

 
With the setups showing the main aim is to get the precipitation. Mother nature looks like taking care that it drops down in version white.
Edited by West is Best

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Just to highlight the uncertainty comparing the GFS op and Control at T288:

 

attachicon.gifgens-0-1-288 (2).png  attachicon.gifgfs-0-288 (1).png

 

Both are cold but the GFS P has 2-3 potential snow events where as the Control is a lot drier. Looking at the GEFS at that time frame and it is clear the hi-res has very little support at that range with the majority cluster showing a return to a more zonal flow:

 

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=288

 

So maybe treat the GFS 06z hi res runs after D10 with caution (probably a good mantra in any case)!

Probably no point comparing anything to the GFS as it is no more after this run. So Parallel all the way, but yes, at 10 days, pointless anyway.

Looking at 10 days we wouldn't have even seen this coming in the first place.

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You no what I have to be honest although there was signs of a change to colder conditions . I really didn't expect to be heading into a freeze. I no its not 2010 but it looks full of potential and certainly has the ability of been colder than Jan 2013 . Those events was very marginal . But ironically it won't match the march 2013 freeze which was a rare event . But certainly real cold air with lots of snow opportunities to give the forecasters headaches.

It's also notable that this is mainly MJO driven which again after been in the slumber for months is nice to see it gaining momentum finally. With the strat event that took place in the first 10 days of Jan I would estimate normally 20-25 days after the event so maybe another week before we see if any trop effects will be felt ? Be nice to go from this easterly to a Greenland high wouldn't high wouldn't it ?

I'm one happy chappy today despite lack of sleep watching the snow most the night !

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Okay I have some news re that ne USA low.

 

So in terms of depth and likely track, if this low deepens as shown then we need it to not run east but ne, the upstream pattern behind this low is now expected to remain more amplified which helps.

 

I know many have their eye on Europe but its essential for any possible easterly that the upstream pattern remains sufficiently amplified.

 

The Azores ridge has to hold on and give the drop down low from Iceland time to clear and separate from any low heights near Greenland

 

The thinking from NCEP state forecasts, they highlight a lot of uncertainty but edge towards the more amplified solutions, in terms of detail this New Hampshire discussion is brilliant.

 

I wouldn't normally quote this much but wouldn't it be great if the UKMO had this sort of in depth discussion available to the public.

 

Overview:

 

SOMEWHAT A SURPRISE AS FORECAST MODEL GUIDANCE TOOK A RATHER BENIGN
FRONTAL PASSAGE ACROSS THE GREAT LAKES REGION INTO THE NE CONUS AND
AMPLIFIED IT CONSIDERABLY INTO A OFFSHORE COASTAL LOW FOR THE LATE
WEEKEND TIMEFRAME. PER MODEL CONSENSUS AND DISCUSSIONS WITH WPC...AN
AMPLIFIED PATTERN WAS PREFERRED THOUGH HIGHLIGHTED IN THE DISCUSSION
BELOW THERE ARE STILL MANY UNCERTAINTIES SURROUNDING THE LACK OF
CLUSTERING AND CONTINUITY OF MODEL SOLUTIONS. IT IS LIKELY THAT AS
WE NEAR THE TIMEFRAME IN QUESTION...AND THE ASSOCIATED ENERGY TO THE
COASTAL LOW IS BETTER SAMPLED...THAT WE WILL GAIN GREATER INSIGHT AS
TO OUTCOMES AND POTENTIAL HAZARDS.

 

SUNDAY...

EXERCISING CAUTION AS THERE IS NO CERTAINTY AS TO OUTCOMES. SEVERAL
POINTS CAN BE MADE THAT EXACERBATE THE COMPLEXITY OF THE FORECAST.
ONE: ATTRIBUTING N- AND S-STREAM IMPULSES REMAIN POORLY SAMPLED BY
UPPER-AIR OBSERVATIONS. TWO: EC/GFS/CANADIAN ENSEMBLE MEMBERS AND
DETERMINISTIC FORECASTS VARY WIDELY IN ALL CATEGORIES INCLUDING THE
STRENGTH...TRACK...AND TIMING OF A POTENTIAL COASTAL LOW OVER THE
GULF OF MAINE. THREE: THE WIDE VARIATION MAY BE IN PART DUE TO THE
LACK OF CLARITY AS TO WHETHER N- AND S-STREAM IMPULSES PHASE /MOST
SEEMINGLY DOWNSTREAM/ OR REMAIN SEPARATE. TO THAT REGARD IT IS
POSSIBLE THAT THE BULK OF ENERGY BETWEEN THE TWO SYSTEMS IS SHIFTED
DOWNSTREAM TO THE LEE OF THE HIGH TERRAIN ACROSS REGIONS OF BETTER
BAROCLINICITY /OFFSHORE/ RESULTING IN MOST OF THE ACTIVITY JUMPING
OVER OUR REGION LEAVING US FOR THE MOST PART QUIET AND DRY.

HOWEVER...RECOGNIZING THE PROFICIENCY AS WHICH FORECAST MODELS HAVE
PERFORMED 7-DAYS OUT...THE OVERALL MEAN SIGNAL OF WEATHER OUTCOMES
CAN NOT BE IGNORED JUST BASED ON THE ENSEMBLES. WPC HAS ACCEPTED THE
TREND OF A MORE AMPLIFIED SIGNAL BASED ON SUPPORTIVE 14.0Z GUIDANCE.
ECHOING WPC SENTIMENTS...WITH PERSONAL PREFERENCE GIVEN TO THE 14.0Z
AND 13.12Z EC/EC-ENS AND CMC/CMC-ENS RESPECTIVELY...SOME CONCERN AS
TO MAGNITUDE OF SE-FLOW OUT OF THE HUDSON BAY AREA ANTICIPATED WITH
THE DEVELOPMENT AND INTENSIFYING COASTAL LOW INTO SE CANADA...AS
WELL AS HOW EFFICIENTLY MOISTURE CAN BE DRAWN N OFF THE NW-ATLANTIC.



 

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Well it looks like finally the (very, very) gradual shift in pattern over the last three months from mid-lat blocking over these islands and Europe to more cyclonic-influenced, and from split jet with dominant arm to the north to split jet with more emphasis south, is finally leading to more significant cold-potential.

 

Perhaps it can be summed up more crudely as a very slow shunt in the overall pattern of systems to a position where they result in the cold that was going sometimes to East Europe and to NE of the American Continent being able to come over here, to some extent.

 

Another possibly even more crude summary I would make is that if one was to gather up the patterns of weather systems since the start of November, there has been very much a repetition in the northern hemisphere, the only major change during that period being the stronger phases of jet activity. In the past I have formed the impression that any sort of shift in patterns to bring much colder solutions here tend to take about 2-3 months. How often have we seen mostly mild Decembers and Januaries give way to colder februaries? Mild winters give way to cold springs? And visa versa.

 

The predicted trough disruption over the coming days repeats that which happened at various times over the last few weeks. This time it seems like it will allow in more entrenched/persistant cold. It's almost as if the first colder PM spells in November (after the record-breaking warmth of October, especially Halloween) progressed to the cold snap just after Christmas and have now progressed further to now. Each period seems to have represented a 'phase'. If anyone could bottle this sort of thing and predict it with confidence/accuracy, there would be little to bother tuning in here for!

 

Except of course to study the details. And as WIB said above, rare (these days, the past 25 years) events like freezing westerlies are something to savour anyway, regardless of how it pans out in the next week.

Many people have been taking about "the best chance for significant snow in two years". Well IMBG it has been four years, hards to believe. And considering the winters of 09-11 provoked predictions of a period of apocalyptic winters for years to come (which I never believed would translate to reality) it seems like forever. So here's hoping this will be a 'proper' cold spell with snow lying for many, that is, lasting at least a week, preferably ten days, if that's not too greedy.

 

Meanwhile this storm is going to pound the west and north of Ireland and parts of Scotland and North England. Hope everyone stays safe. Serious storm followed by possibly serious cold, as Al Pacino said in Carlito's way, "Here come the PAIN!!" Of course, for those who saw it, Al had no pain to give, as his gun was out of bullets. Lets hope the cold stays loaded!

 

My view of the models predictions currently - alot of stuff not at all nailed on yet, the sort of combination of things needing to happen that could change radically as small shifts occur. The progress from the storm to this weekend alone is fraught with unlikelihood. The odds of it ending up with anticyclonic influence forcing any cold too far northeast to influence much of these islands are strong IMO. A much more likely outcome that what the models are showing, for lets be honest, only a day or two consistently, and even then only some models.

 

If the anticyclone pushes further east earlier at the end of this week and cuts off the Arctic air before it hits us then the chances of the following predicted trough disruption next week being too far east for many of us are very strong.

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Just to highlight the uncertainty comparing the GFS op and Control at T288:

 

attachicon.gifgens-0-1-288 (2).png  attachicon.gifgfs-0-288 (1).png

 

Both are cold but the GFS P has 2-3 potential snow events where as the Control is a lot drier. Looking at the GEFS at that time frame and it is clear the hi-res has very little support at that range with the majority cluster showing a return to a more zonal flow:

 

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=288

 

So maybe treat the GFS 06z hi res runs after D10 with caution (probably a good mantra in any case)!

Much the same as the anomalys which have showed zonal at 360 forever and not the up and coming cold period.

 

It is very important for newbies of a fragile tendancy to note that anything after say180z (most of the time) is to be treated as a highly unliklely to verify period.The GEFS have been a useful tool for trends into the longer period.Along with the means.

Edited by winterof79

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Way out to be discussing snow detail, But the synoptic ido shows would produce Snow for the South.

 

162-574UK.GIF?14-6

 

that is not showing snow for the south though is it apart from a small patch in Devon.  Either way that will 100% change anyway come next week

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 I DON'T KNOW WHAT TO SAY...

Lol! say about what, shock that some colder synoptics might actually verify. The UK's defences against decent cold with snow might be breached!

Edited by Polar Maritime

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What ? Where has that come from ?

 

Are you referring to the currently synoptics churned out recently by any chance Barry ?

 

:cold:

Edited by ajpoolshark

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Absolute madness on the charts. So much to play for in the coming few days.

Short term still doesn't show my neck of the woods getting much if any but I have seen before the difference that is made when a large proportion of the country has lying snow.

Best shot of the winter so far.

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