Model Output Discussions 18z 31/01/2016

[MR EXTREMES]

I'm certainly under no illusions on snowy breakdown I think this cold snap was never going to be anything of interest unless u live on a hill a high hill.

moving on things don't seem much different apart from relaxation of Atlantic storms and cooler at times.

im glad I threw the towel in last week so my interest in the incoming rain band tomorrow is zero.

some will see flakes of snow sleet but mostly sleet wet snow rain.

very tiny possibilities that march may have sting in its tail especially further north.

but pretty certain winter has rolled past very disappointing so looking forward to summer now.

hopefully high pressure will soon start to dominate for large periods of time just in time for summer.

those who do see wintry weather enjoy 

[phil nw.]

The latest London Ens.Temperature graph from the 00z runs.

Fairly typical of the expected westerly set up.

After the mild blip for the south over the weekend the outlook doesn't look far from average.I would imagine further north some lower values with the jet tending to move south and polar air more dominant at times.

Edited February 16, 2016 by phil nw.

[karlos1983]

19 minutes ago, phil nw. said:

The latest London Ens.Temperature graph from the 00z runs.

Fairly typical of the expected westerly set up.

After the mild blip for the south over the weekend the outlook doesn't look far from average.I would imagine further north some lower values with the jet tending to move south and polar air more dominant at times.

Not many are on the warm side in the extended range by the looks of it. Infact seems to be a majority cluster on the cold side?

Pretty good set of Ens right there in terms of cold potential.

Perhaps winter is not done just yet!

Edited February 16, 2016 by phil nw.
amended error in quoted post

[phil nw.]

6 minutes ago, karlos1983 said:

Not many are on the warm side in the extended range by the looks of it. Infact seems to be a majority cluster on the cold side?

Pretty good set of Ens right there in terms of cold potential.

Perhaps winter is not done just yet!

Yes further north looks quite cold on the gefs chart Karlos as i alluded to.

Aberdeen 

It could well be a period of days with quite cold polar air coming south behind Atlantic fronts with areas further north remaining on the cold side of the jet for longer periods.

I guess it is easy to overlook that parts of Scotland will have a different perspective of Winter than many of us further south and this sort of split could well continue.

Edited February 16, 2016 by phil nw.

[karlos1983]

I know attention will probably be on the close range, and looking at the 12z just rolling out, but one thing of note from just going through all 20 GEFS purbs in the +192 onward territory if you ignore the detail, a lot of them are showing heights to the NW of the UK being a distinct possibility, so something to look for on the 12z for comparison for me later. I certainly don't think the Atlantic will be firing back up on all cylinders like the majority of Winter going off the 06z Purbs and a lot to still be positive about.

[TomDav]

GEFS 06z categorical snowfall probabilities

[karlos1983]

Just now, TomDav said:

GEFS 06z categorical snowfall probabilities

 

Purple being snow Tom?

[TomDav]

Just now, karlos1983 said:

 

Purple being snow Tom?

Yeah purples are high probabilities, light blue low

[Man With Beard]

GFS for Weds/Thurs - just seems to oscillate between runs. This time, the GFS 12Z seems to save most of the lowland snow for the SE corner on Thursday - higher ground most at risk further north/west. Still no clear direction for a huge portion of the country.

[IPredictASnowStorm]

What time is it showing this?

10 minutes ago, Man With Beard said:

GFS for Weds/Thurs - just seems to oscillate between runs. This time, the GFS 12Z seems to save most of the lowland snow for the SE corner on Thursday - higher ground most at risk further north/west. Still no clear direction for a huge portion of the country.

 

[karlos1983]

One thing that now look certain is that the warm air at the weekend won't be hanging around for long.

 

[Man With Beard]

4 minutes ago, IPredictASnowStorm said:

What time is it showing this?

 

Lunchtime Thursday?

On and upwards though, summoning up the spirit of Nick Sussex, GFS T120 is interesting. Could the low in the Atlantic act as a trigger low to bring cold back into the UK by T168, as it combines with the mother low to the north?

[karlos1983]

Looking like a better 12z than 06z, the low heading toward europe and heights building north in the Atlantic 

[Tim Bland]

Who's got the nerve for another week of marginal snow event chasing ? 

[chris55]

Im quite looking forward to see how tomorrow unfolds!

A very very tricky forecast all round, the met have yellow warnings out "just in case". How the band of ppn evolves over the next 36 hours will be fascinating. It may well be all rain, it may slow up....speed up....fizzle or it may even deliver a little of the white stuff down south.

Nowcast it is then!

[IDO]

GFS snow depth after the front pushes through Thursday:

 

 

 

[Hotspur62]

29 minutes ago, Tim Bland said:

Who's got the nerve for another week of marginal snow event chasing ? 

Need that Low to be another 50-75 miles further South and then we could be in business. On a couple occasions this winter the trend has been for Lows to move Southwards so will interesting to monitor this. TBH this is a week away atm but hopefully will still be  there come the weekend. In the meantime we have the fun and games of the next 48 hours to resolve. History tells me that it will be a rain/sleet event with snow with elevation(150m+) but hope for upgrades and for people to get their snow which has been severely lacking for the last 3 years Midlands Southwards.   

[bobbydog]

hints that winter is coming....

in spring!!

[Frosty.]

The southeast is the sweet spot on the Gfs 12z, Essex and Kent could get a covering on Thursday.

[feb1991blizzard]

37 minutes ago, Tim Bland said:

Who's got the nerve for another week of marginal snow event chasing ? 

Looking at these charts, there could be a fair few more as well before March is out, the end to this snow chasing season has got March 1995 written all over it, we cant keep being unlucky though, if those runners keep coming we will hit the Jackpot at some point.

 

All aboard the Wave 2 train.

[gottolovethisweather]

19 minutes ago, Karl. said:

The southeast is the sweet spot on the Gfs 12z, Essex and Kent could get a covering on Thursday.

 

 

 

I don't want to be a killjoy but are these simply not charts showing the precipitation type expected rather than a prediction of snow cover? (granted you've used the word could Karl). The reason I ask is that I forsee the wet snow truly struggling on what will likely be wet surfaces in the first instance. Perhaps it is still possible but away from the South, Southeast and Southwest I'd be shocked to see any snow cover other than possibly at elevation, say above 200m or so. Northern England and NE England in particular, having a strong likelihood of an all snow event hence a much better chance of lying snow there and not exclusively at elevation. An interesting watch anyhow and the excitement building over the snow potential is good viewing in here. 

Edited February 16, 2016 by gottolovethisweather

[Frosty.]

1 minute ago, Essex snowman said:

If it happens Karl then finally il day it's been a good winter lol 

Well you deserve it Essex Snowman and I have proved beyond doubt I have no imby bias, I really hope the snow starved south / southeast gets some white stuff..The charts show it..let's hope they prove to be correct!

[Singularity]

To be honest, next week is starting to steal the limelight big-time, due to the large potential for improvements to the ridges to the W/NW and the jet tracking more favourably. For example, that Scandi trough at +144 need only be a little closer to drive a cold air undercut for that channel undercut from the 12z GFS for days 6-7. After that it makes a bit of a hash of the trough disruption/slider mechanism but the broad theme never goes away - and all the while, high latitude blocking builds. The final chart is almost eye-candy but as usual GFS displays a poleward bias with the polar jet.

   

The blocking, at last, is a bit epic:

I'm sure its no coincidence that the MJO finally reaches phase 8 on this run, presenting another opportunity to pose the epic analogue chart for that phase in February:

Although we'd be starting March by then (if it took that long - look how fast it's moved again since yesterday), I think the first week or so is close enough to Feb that the effects would be generally similar. 

It's not just the MJO behind this HLB signal though; just look at the stratosphere at 30 hPa:

GFS did, however, move drastically away from this for a short time yesterday before returning with even better results today, which lowers confidence - though the backtrack does mitigate that to some extent. The above is enough to promote thoughts of something like March 2013 unfolding, but the 06z didn't produce such a mighty split and so this remains just a possibility for now.

Good thing* is, the vortex looks to be displaced away from the North Pole and Greenland again by just 7 days time, and this trend is maintained through to day 10 with little sign of ceasing soon thereafter:

  

 

This seems to be an incredibly long period of sustained warming at this level. It barely even pauses for breath in the next few days and then just keeps on coming!

*if you like cold weather in March!

Edited February 16, 2016 by Singularity

[nick sussex]

The same broad theme shown in the GFS and UKMO although there are differences with the handling of that low in the southern jet stream. The GFS takes this east cleanly and the UKMO has this attached to the troughing.

I'm pretty sure the ECM will follow this broad theme tonight so its really now seeing whether theres enough cold heading south to meet any shortwave low heading east.

NCEP discussion looks good downstream for western Europe:

OVERVIEW AND GUIDANCE/UNCERTAINTY ASSESSMENT... LATEST MODEL/ENSEMBLE MEAN SOLNS DISPLAY BETTER THAN AVG AGREEMENT ON THE PATTERN RETURNING TO AN AMPLIFIED WRN RIDGE/ERN TROUGH BY EARLY NEXT WEEK... IN RESPONSE TO A DEEPENING MEAN TROUGH BTWN AK/HI. THIS EXPECTED PATTERN IS CONSISTENT WITH TELECONNECTIONS RELATIVE TO THE STRONG NEG HGT ANOMALY CENTER OVER THE E-CNTRL PAC AS WELL AS POS HGT ANOMALY CENTER OVER THE ATLC AS DEPICTED IN D+8 MULTI-DAY MEAN CHARTS.

The hgt anomaly in the Atlantic is in relation to the displaced Azores high, the upstream pattern normally pulls that west/nw, you can't have a Euro limpet high with that upstream pattern! Thankfully! Generally the correlation with that upstream pattern is Euro troughing which is helpful.

 

Edited February 16, 2016 by nick sussex

[Singularity]

Appraising the model projections for the MJO from the 13th compared to today:

I've added matching coloured crosses for where each of the models had the MJO for the 16th as of the update on the 13th (ECM and JMA were the same, so share the yellow/orange cross). They've done a decent job with the propagation speed, but only UKMO has anticipated the level of amplification - as ironic as that is given what the Met Office thinking was last week.

GEFS then had a two day propagation time to phase 7, ECM three or four (stalls momentarily at the borderline). Now, GEFS goes for between two and four, with a momentary stall, while ECM is keen on just the two days.

From this it can be concluded that it's the greater than expected magnitude of the current Kelvin Wave - perhaps with the MJO already coming together, sooner than expected - which has changed the nature of the ECM and GEFS output so much, as  opposed to faster propagation.

We'd probably have seen a steadier UKMO if only it went beyond 6 days range.

Edited February 16, 2016 by Singularity