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Paul

Model Output Discussion - Stormy Period Inbound...

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Tonight's GEFS 12z mean shows good support for a cold snap around T+240 hours, perhaps an Arctic flow with snow showers. Overall the models show a very unsettled and sometimes stormy outlook and although there will be some mild weather, there will be cold weather too, possibly lasting up to a few days or more at a time, especially in the period I mention above, there is also a possibility of a spell of fine and chilly conditions during late january with widespread frosts according to the mean.

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Edited by Frosty.

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That's an excellent post, Tamara - as ever - much appreciated.

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best output for sometime here we go then

ecm 240fi 

ECM1-240.GIF?06-0

cold air incoming could be some real excitement across the broad scale of the uk but up until this point colder milder so not terrible by far

ECM0-240.GIF?06-0

 

ukmo dragging polar air in snow in the forecast for sure

UW144-21.GIF?06-18

UW144-7.GIF?06-18

its not here yet by the ukmo but its heading that direction.

 

gfs and gfs p plus gefs all have a feature futher south in the alantic although this might seem strange but this itself can turn tables allowing other things to start building in 

gfs-0-192.png?12

gfs-0-192.png?12

gens-0-1-180.png

gens-0-0-180.png

trending more colder as we move forward through jan regardless whether its from the nw or even west lots of cold air digging down from our nw also this little feature on the gfs family does provide possibilities.

 

milder especially in the south but colder from time to time and becoming colder if the gfs family trump the ecm but even the ecm is a little better today.

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I am hoping that tentative signs we will get colder conditions into low levels of UK post mid Jan into late Jan. With no deep negative AO or NAO since mid Nov and any SSW still yet to come to fruition we are looking at any straw to clutch.

I suggest with AO and NAO trending neutral negative after mid month...a shift of the NE Canada segment of the PV to SIberia and hence a slowing of a powerful jet we may see some colder options start to cement into outer reaches of GFS in future runs. Fingers crossed as I really don't want to wait for a late Feb Easterley or March spring cold. That scenario doesn't float my boat re Winter cold at all. Nice black hole of death there

yep interesting you say this not so much the neg nao ao !

but the segment of the pv and nearly every models see very fine decline and movement lets hope it wobbles on holiday over to scandi or the other side of the arctic please polar vortex pea off.

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It was just general comment that a deep depression of 940mb is not good news both regards wind and precipitation. I wasn't being more specific because I've no doubt this will have changed by the runs tomorrow.

 

Imodium?

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Duplicated by mistake..damn tablet lol

Edited by Frosty.

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Imodium?

 

Yes after I wrote it I thought it might open the flood gates.

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Plenty of cold weather on tonight's Ecm 12z op run with a risk of sleet and snow showers at times, also a risk of leading edge snow as frontal systems bump into cold air, on balance, it's cold which has the upper hand with 522-528 dam thicknesses making inroads SE.

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Edited by Frosty.

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I am hoping that tentative signs we will get colder conditions into low levels of UK post mid Jan into late Jan. With no deep negative AO or NAO since mid Nov and any SSW still yet to come to fruition we are looking at any straw to clutch.

I suggest with AO and NAO trending neutral negative after mid month...a shift of the NE Canada segment of the PV to SIberia and hence a slowing of a powerful jet we may see some colder options start to cement into outer reaches of GFS in future runs. Fingers crossed as I really don't want to wait for a late Feb Easterley or March spring cold. That scenario doesn't float my boat re Winter cold at all. Nice black hole of death there

 

 

Sorry but that is what looks like happening, after the glorious cold, sunny and snowy March/early April 2013 i say, Bring It On.

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The " pot of gold at the end of the rainbow" continues this evening.

 

Some GEFS members look interesting but sadly seem to be stuck in the dark reaches of FI, the search for snow surely shouldn't be this difficult!

 

The much debated MJO shows conflicting signals depending on which output you look at, some weaken this in phase 6, others have it scraping into phase 7.

 

It's likely the PV will weaken somewhat towards mid month and I think cold prospects look a bit better after that but whether that can bring some deeper cold or just below average only time will tell.

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Perhaps some signs of a potential cold spell around mid-month from both ecm and gfs where both models to a degree show a mid-Atlantic ridge and low pressure over Scandinavia, at the unreliable time frame of T+240.  In the meantime, lots of weather to come along with the fluctuations of mild and cold spells....

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post-6830-0-85109700-1420574981_thumb.pn

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The very strong jet stream does look like gradually weakening during the second half of January, the peak of the stormy potential is at the end of this week and into next week, when the jet eventually slows down we could be looking at much colder scenarios as shown on some of tonight's GEFS 12z perturbations.

Edited by Frosty.

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For what its worth (caveats galore), the GEFS look a little bit more amplified at day 10 compared to the ECM ensembles.

 

gensbc-21-1-240.png

EDM1-240.GIF?06-0

 

Maybe the GFS/GEFS over-doing any mid-Atlantic amplification?

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For what its worth (caveats galore), the GEFS look a little bit more amplified at day 10 compared to the ECM ensembles.

 

gensbc-21-1-240.png

EDM1-240.GIF?06-0

 

Maybe the GFS/GEFS over-doing any mid-Atlantic amplification?

 

I remember a few weeks ago it was the ECM ENS that showed huge amplification in the Atlantic, and the GEFS were having none of it. That time the GEFS turned out to be correct. It'll be sods law though if the ECM ENS have this one nailed....

Edited by SE Blizzards

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The ECM extended eps have rather a wide envelope by T360. Again, it progs the removal of the euro high anomoly and shows a Mediterranean upper trough. No low anomoly to go with it so we're not looking at a solid low pressure down there but I always think that where no anomolys are shown in the distance, that area could go either way.

A MLB looks unlikely given the pressure probability profile. wouldn't be wise to discount anything by the back end of week 2 - been saying that for a while now!

Edited by bluearmy

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Quite a strong polar maritime blast incoming next weekend, showers turning to sleet and snow I would think.

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post-4783-0-27575600-1420579658_thumb.gi

Edited by Frosty.

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The " pot of gold at the end of the rainbow" continues this evening.

 

Some GEFS members look interesting but sadly seem to be stuck in the dark reaches of FI, the search for snow surely shouldn't be this difficult!

 

The much debated MJO shows conflicting signals depending on which output you look at, some weaken this in phase 6, others have it scraping into phase 7.

 

It's likely the PV will weaken somewhat towards mid month and I think cold prospects look a bit better after that but whether that can bring some deeper cold or just below average only time will tell.

The dark reaches of FI have been around the dates 18th through to 20th for a while now.They are not being pushed back as is the norm Nick.The trend is our friend as they say. :cold:

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Has anyone got any charts for the 14th please regarding this storm? Thanks

The storm you refer to is not within the reliable timeframe and as such will be subject to change.Here are the latest GEFS panels for that time frame

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=192

 

Many of the GEFS prog the low to be further north of the UK much as Ian F referred to in his earlier post that low pressure systems MAY start to move further north than at present.

 

Indeed ECM is not overly keen on it on its 12z output

http://www.meteociel.com/modeles/ecmwf/runs/2015010612/ECM1-192.GIF?06-0

Edited by winterof79

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Has anyone got any charts for the 14th please regarding this storm? Thanks

 

 

GFS in particular showing a nasty storm,but much to far away to be able to pin any detail on.

 

post-2839-0-59094600-1420581129_thumb.pn

 

 

Check back in here on Sunday to see if the threat is still there.

Edited by Cloud 10

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Some very tentative changes emerging in AAM forecasts which might underpin the hints of a gradual pattern change upstream through the second half of January.

 

Whilst these forecasts are just GEFS based (and tentative) they do lend some credence in terms of latest METO monthly suggestions based on EPS data

 

Starting with the here and now first:

 

GWO has undergone another fast classic -AAM style orbit through phases 1,2,3 and then return back to phases 1,2. Negative frictional torgues have led to negative mountain torque, adding yet further easterly momentum in the sub tropics to the atmosphere, compensated by stoking up poleward westerly momentum at mid and higher latitudes.

 

Net effect? : The fast and furious zonal pattern and invigorated Canadian/Greenland vortex we are witnessing following the brief turn of year vortex split.

 

As suggested in previous posts, re-initiated Nina imprint to the atmosphere has beefed up sub tropical ridges - and a strong Azores High features in the near and mid term, forcing a dynamic pressure gradient differential between the High pressure to the south and the zonally active jet stream just to the north of Scotland.

This pattern now fully advertised in modelling with the deep lows which threaten Northern areas most especially later this week

 

Meanwhile, the MJO continues its eastward progress towards the dateline, but convection, as anticipated, still looks set to die before it overwrites the more beneficial downstream phases in the central/eastern Pacific. We should not, imo, therefore expect any significant downstream amplification signal around the mid month period - much as suspected in recent days.

 

This signal could yet be just delayed rather than cancelled though

 

Beyond the 10 day time period there are early and uncertain indications that the atmosphere will attempt to scrub westerly momentum from mid and higher latitudes as easterly trades in the tropics show signs of weakening - as negative torgue wave lengths become exhausted.

 

So, although uncertain and FI, these predictions are a logical atmospheric pay-back budget balancing compensation act for sooner or later

.

Resultant rather more positive AAM tendency consequently added to the atmosphere in tandem with a less strong ferrel cell signal, gives fully credible support to FI forecasts of forcing the GWO through phase 4 , and into 5

This Phase progression neutralises Nina tendency in the atmosphere and would take us closer to a more 'Nino friendly' atmospheric signal as we head closer towards the last third of the month and February. Such a signal would better favour ridging of High pressure at better altitude

 

GWO direction of travel through Phases 4/5 engages positive frictional torgue and then subsequent Asian positive mountain torgue. Net effect would be to force orbit through to Phases 8/1 and trigger a retrogression of the Pacific pattern and switch from -PNA signal to a more +PNA pattern

.

With the EPO as a consequence turning more +ve, and pressure falling towards the western US coast, this change of pattern would concur with better downstream amplification feeding eastwards thereafter into the atlantic.

 

In tandem with pressure rising across the Atlantic as the Azores High is weakened and retrogressed North-Westwards, this gives the support for Greenland/Canadian vortex gravitas to transfer eastwards into Scandinavia.

Such vortex transport would be of even further benefit if longer term stratospheric trends could continue to favour a more favourable split in the Atlantic sector next time around.

 

Long way off, a lot of uncertainties yet to come, and the atmosphere has to plough quite some furrow yet for a while, but things sure would become much more interesting for the last third of winter.

 

Such evolution does rather echo a typical weak El Nino winter which is often characteristically 'end-loaded' (final-third) for cold. In that sense, and in the context of the frustrations of the winter so far for snow and cold lovers, this sure would be some compensation.

 

http://www.atmos.albany.edu/student/nschiral/research/gwo/gfsgwo_1.png

Tamara

For me I have this feeling that we'll be waiting a wee while yet for decent prolonged cold setup....if indeed one does arrive.  Excellent post but so were previous ones and we're all getting bitten thus far as even your reasoning during December re Jan is not happening.  I hope back third is right....Feb is my coldest month, and I feel this month will maintain 'westerly' with two main stormy periods coming....this week and around 18-22 tied in with perigee/new moon 20/21.....hopefully the start of a pattern shift.  I'm hoping the vortex shifts to our locale...or just to our east come Feb

 

BFTP

Edited by BLAST FROM THE PAST

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A major difference between NOAA EXT ECM EPS at T360. and GEFS mean anomalies. NOAA and the ECM are more or less singing from the same hymn sheet ( the former does have the UK trough further east) but the GEFS isn't. It removes the eastern/Atlantic trough or at least retracts it towards Greenland, , retains the one in the Med and settles for an Atlantic HP zonal flow.

Charts weatherbell

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Edited by knocker

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