Model output discussion - 21st Jan Onwards

[MP-R]

4 minutes ago, -Bomber- said:

February is the second coldest month of the year and the second snowiest after January so it's more likely to snow than in December. "yes we have had snow in Feb, but it is still low probability when you compare when we didn't." You can say that about any time during WInter/Spring. The day by day post is a tad extreme too

I just fear that if a wintry spell shows up in the second half of February, it will be something like 2005 with fantastic synoptics but given the conditions prevailing through so much of the winter here, it will amount to next to nothing in snow amounts away from higher ground. I think we would have to rely on either a strong northerly for widespread snow with emphasis on night-time falls or a prolonged bitter spell culminating in a front approaching from the southwest.

Anyway, all up in the air at the moment (pardon the pun) and emphasis will be on strength of Pm shots, at least through the first week of Feb. We managed snow here on 14th Jan last year with -5C uppers and snow showers on the 29th from -6C uppers, both on westerlies.

[fergieweather]

7 minutes ago, Essex snowman said:

I'm with frosty still plenty of time to get snow and ice till end of March so stop being so negative 

True (as 2013 attested). Indeed, as the UKMO 3-month outlook (issued this morning, to ensure proper assimilation of the ongoing stratospheric developments) alludes, re overall temperature signal from late Feb into/through March. 

[coldcomfort]

1 minute ago, fergieweather said:

True (as 2013 attested). Indeed, as the UKMO 3-month outlook (issued this morning, to ensure proper assimilation of the ongoing stratospheric developments) alludes, re overall temperature signal from late Feb into/through March. 

Why am I not surprised that the start of meteorological spring will probably bring the best chance of widespread wintry weather...as I said yesterday in the moans thread, the line on the UK weather headstone will read ' right synoptics, wrong time of year'

[EastAnglian]

May be a stupid question and please feel free to move mods if inappropriate. But as there is the possibility of wintry/snow showers in the next week or so is it possible to calculate the lapse rate (change of temperature with altitude) from the model output and if so is there a beginners guide on the forum?

Edited January 26, 2016 by EastAnglian

[Ravelin]

15 minutes ago, Essex snowman said:

I'm with frosty still plenty of time to get snow and ice till end of March so stop being so negative 

Obviously given my location I'm better situated than many but up here March is just as much a winter month as December is. In fact, so far I've had more snow days outside the "winter" months than I've had in them this year.

Anyway when PV-wise you go from this currently....

To this the same time next week...

Then I think you've got to look at it as a positive development. Beyond that, well who knows.

[Frank Trough]

5 minutes ago, coldcomfort said:

Why am I not surprised that the start of meteorological spring will probably bring the best chance of widespread wintry weather...as I said yesterday in the moans thread, the line on the UK weather headstone will read ' right synoptics, wrong time of year'

Blocking is statistically more common in spring anyway, isn't it? weakening vortex and all that...i'm sure I read some old flannel that snow is more common in march than December in the south.

Interestingly (and for "fun") the CFS monthlies suggest February will be above average but every month after that until the end of civilisation will be slightly below average and no doubt windy.

[mb018538]

Autumn and winter tend to be more stormy with tighter thermal gradients as everything cools down.....so spring does tend to favour more higher pressure patterns than say Oct/Nov, coupled with a weakening vortex at the pole.

6z carries on the cool/mild/cool/mild rinse and repeat pattern right out until 384. No solace in this run at least.....on to the broader range of the 12z for some more crumbs to feed on.

[Singularity]

4 hours ago, Nick F said:

Large -ve height anomaly over NE Atlantic and the U.K. through much of the run. Aleutian low anomaly, west Canadian ridge, eastern US trough also dominate again after day 10 after a temporary reversal to western U.S trough / Eastern U.S. ridge. There is +heights over the Arctic though for much of the run. But the general theme looks unsettled through much of Feb.

The EC32 850mb temp anomalies suggest -ve departures over much of the N Atlantic and into the UK at times through much of the run though, so it's not particularly mild for us.

 

Thanks for the update. It sounds like what's not quite there is a pronounced enough mid-Atlantic ridge between the eastern U.S. trough and that across the UK (which would be less across the NE Atlantic with such a modification). Almost but not quite there... I wonder how much that model makes use of reanalysis data as a guide?

 

Anyway, some very positive trends from ECM and GEM this morning. The amplifying trough moving across the central U.S. drives enough ridge development ahead of it to encourage the Euro high to depart for the Azores and then make at least some attempt to ridge north. The bigger consequence though is how this makes room for low heights to dig south through the UK on the western flank of the Eurasian trough. This is good because it draws cold air down from the NE toward the N of the UK which may then interfere with the attempts of further Atlantic lows to turn the flow back to the west. Handling that sort of thing effectively is beyond the capabilities of the longer-range guidance.

ECM +192:  +240:   GEM +240:  

Of course, the usual caveats apply given the range this is at. GFS is more progressive with the U.S. trough so things really don't work out in the longer-term. Again I look to tropical signals and figure GFS is missing some amplification and toning down of the polar jet... hopefully this intuition will be along the right lines.

GEM doesn't dig the trough down quite so neatly and this is another variation to consider. It still looks tricky to get some decent cold air in across southern parts until after the first week of Feb.

At this point though it's important to consider what's going on with that U.S. trough. What GEM does is keep it a relatively shallow feature, so although we don't get as much of a ridge ahead of it, there is a distinct lack of any catalyst for redeveloping low heights over Canada. This run looks to me to be headed for a west-based -ve NAO which is a start given the tendency for such to drift east as Feb progresses.

ECM does develop the trough quite a bit, but without any other troughs in the mid-Atlantic and the Arctic High so close to Greenland, I can't see a route back to a Canadian vortex segment there either. From that +240 I reckon it would either turn out a bit like the EC-32 or see some trough disruption to keep things a whole lot more interesting.

 

It's also worth bearing in mind that all of this analysis is based on what we have in front of us this morning, and if the ECM/GEM trends of the past 48 hours continue, it is possible that variations such as a ridge toward Iceland could crop up, or even the U.S. trough I've been talking about tracking further south and stalling out as the cold, unstable air is dispersed. 

The other side of the coin sees the tropical signals fail to materialise and an unpleasant trend toward GFS' more progressive runs of late. There's a lot resting on the extent to which the 'tropical Indian Ocean interference' is genuine or an artifact of the models being confused.

[Frosty.]

The Gfs 6z shows regular incursions of Pm air with sub 528 dam thicknesses, especially further north with occasionally wintry ppn and a chance of snow, the highest risk of snow across upland northern UK but there is scope for the jet to dig further south and bring a chance of wintry conditions to more of the UK at times since the alignment of the jet is good for reloads of polar air mixed with milder, wet and windy spells so most of us would have some night frosts and the north especially would see some snow at times..it's something to build on from a coldies point of view!

[BLAST FROM THE PAST]

As the days lengthen so the cold will strengthen.  And the BH the  UK in general is more likely to see snowfall is?

Plenty of time, and imo moves are afoot to see some good interest into Feb.  And a very interesting update by Fergie too

 

BFTP

 

[Iceni]

1 hour ago, fergieweather said:

True (as 2013 attested). Indeed, as the UKMO 3-month outlook (issued this morning, to ensure proper assimilation of the ongoing stratospheric developments) alludes, re overall temperature signal from late Feb into/through March. 

You could include early May. My late Mum's birthday was 2nd May and it's been snowy several times, albeit on high ground  in Sussex.

Edited January 26, 2016 by Iceni

[Nouska]

I don't know when the Contingency planners forecast was written but mention of both MJO and SSW as a likely route to negative NAO in the month ahead.

If February is likely to be a bit above on balance, a colder outlook for the three months as a whole, lends credence to the change seen in other outputs for a cool spring.

"The MJO is expected to reach a phase in early February which is conducive to a negative phase of the NAO in mid- to late-February."

We'll see the latest EC32 later - if it continues with a faster orbit than the short range.

For comparison after update.    

 

 

[fergieweather]

11 minutes ago, Nouska said:

"The MJO is expected to reach a phase in early February which is conducive to a negative phase of the NAO in mid- to late-February."

We'll see the latest EC32 later - if it continues with a faster orbit than the short range.

For comparison after update.    

 

 

Hi Nouska, the latest EC Monthly MJO forecast was issued yesterday (see below). Note that UKMO also run this via GloSea5, so their assessment isn't solely based upon the EC version.

[ukpaul]

I mentioned as such in the banter thread but it tends to be not the original suggestions but the subsequent spin that confuses matters. Someone like Ian posts something, it gets misinterpreted, people fixate on a word rather than the whole post and the caveats therein and weeks down the line you get the 'but so and so said' posts which reflect the spin not the actuality.

Case in point was GP's mention of torpedo within a post in early January that suggested a mid Jan to Feb 1983 evolution. He didn't link to it but that period was similar to what we're getting, cold spell followed by westerlies and storms for the North, getting to a potential lowering of heights to our west by the second week of February. To read some commentary it seems to have been built up into some mega snowfest that failed already to transpire.

What remains is no clear sign of height rises to the West but that period is still in FI. The next week will show us if the warming has helped or hindered (and knowing us it will be hindered!) 06z looks to be going the right direction  by 240h at least.

[Ali1977]

33 minutes ago, fergieweather said:

Hi Nouska, the latest EC Monthly MJO forecast was issued yesterday (see below). Note that UKMO also run this via GloSea5, so their assessment isn't solely based upon the EC version.

Is this from the METO better for cold that the one Nouska posted?

[fergieweather]

8 minutes ago, Ali1977 said:

Is this from the METO better for cold that the one Nouska posted?

That's ECMWF Monthly. 

[Weather Observer]

I like to believe that we have a 15 week window in this country for a snowfall to stay around for at least a day or two. That is from late November to early March. November 2010 was the best example of the former and March 1965 the best late snowfall I can remember.

Near the south coast of Hampshire, we had 15cm of powder snow on 4th March as the low shown on the chart below moved south east across the country. What seemed remarkable to me was that the snow showed no signs of melting in three days of brilliant sunshine that followed. As the second chart shows we were under artic air with very low uppers. The snow then slowly disappeared but some was still around after a week. When it did go it there was no messy end. It remained dry and settled.

Of course the synoptics may not deliver in the six weeks left but we can't know that. There is still hope. There are of course even later Spring snowfalls that we can post to keep morale up but let's not go their just yet

Edited January 26, 2016 by Weathervane
Wrong date

[Coopsy]

1 hour ago, will_wonka said:

I know the more "experts" amongst the squad here are stating the next shot of chilliness will come, but timeline wise over the past month or so it's gone from generic Feb, to first half Feb, mid Feb to now end Feb / early March by some here.

Truly pin the tail on the donkey.

i know "scientifically and with modelling assistance " 10 days is a good benchmark for future potential will it / won't it get cold / mild but frankly it's still guesswork and pattern interpretation. Signals yes but as we know - no guarantees.

We are bound to get "colder" at some point, whether sustained or just a shot.

I think for us amateurs and I'm a super am - it gets frustrating to hear about potential that constantly pushed out by timeline.

For those that do flip the coin or go with a hunch stating "it's a dead cert" certainly amongst the more regular squad, are brave or just (maybe due to frustrating Synoptics) just think f*** it and hope it happens. I guess if it pays off then credibility is abound and we all wonder what others missed! If it doesn't pay off, credibility shot due to a wild guess.

i think the majority of model discussions are excellent on here - sometimes right, mostly not but that's the joy of weather on this small rock. Keep up the great work.

ive lurked for years but the excessive "xx mentioned Feb", "xx said we will get something in his prediction back in July" - yes I'm dramatising - gets a bit long in the tooth as it rarely verifies and if it does, was nothing more than a good guess - Lady Luck and nature teamed up!

sorry for the whine but used to be "very real" on here - seems now it's a bit ego based.

mods - please feel free to move.

Spot on (for some) but by the very nature of having a like button on a post it becomes a game of ego's (again for some)

Also as you stated there are some great posts and educated guesses based on what computer models are telling us. If the models were right it'd be dull everyone getting it right all the time lol

[Rocheydub]

Looking possible for my locality on Saturday now, marginal, but certainly possible! Would be my first proper snowfall since 2010 if it does land!
 

[IDO]

2 hours ago, *Sub*Zero* said:

When cold and snowy weather is actually showing you don't provide the same level of model analysis (if at all) but seem to take pleasure in making detailed doom and gloom posts writing off wintry weather prospects weeks at a time!

As we move into February there is still every chance of a cold and snowy period and even in March you cannot rule it out. There has been some very wintry weather in February before and some good snowfall events have occurred during that month and more recently March (although not ideal) has shown us that we shouldn't give up hope, plenty of time left if everything falls into place and we have plenty of time left for that to happen imo. 

 

Cheers for that,  I am in here for the search for cold and not to be all "doom and gloom". It's just when we get patterns like we are experiencing now and we have seen enough of them over the last few years, they are nearly always winter killers, taking big chunks out of the coldest part of the Winter. We are over five days since this synoptic popped up and it remains relentless on today's D16 on the GEFS. I wasn't prescient five days ago, its just based on previous model watching, that I was very confident that this was a locked in pattern. Just my opinion and I am always open to opposing views as I am no expert, just a keen hobbyist. There are background signals but until the models start showing these I am not going to be presumptuous, as we are seeing the PV as the main driver of the NH at the moment.

As for not posting when it is cold and snowy, when was that, did I miss that cold spell?

Yes February can be cold; and it can be mild and it can be rainy and it can be dry, and it may be....

My opinion remains that blocked cold will only come from a SSW, if you go back to December I haven't changed that view. We should get a displacement at least of the strat PV, and a good chance of a major SSW. So the last third of Feb is now the time period we are looking at, 5-6 weeks later than was forecast by the experts in December, so for me very disappointing.

I won't post the 06z GEFS mean but a snapshot of the GEFS show little sign of any changes yet:

    London Ens T850s: 

^^^ The GEFS for the 06z run showing the classic sine wave signature for a zonal flow, how much of those colder uppers will penetrate down south after D6 is debatable and are dependant on how stormy the lows are, as well as shortwave developments upstream; but the further north you are the PM flows will be cooler and the TM not as mild.

 

[MP-R]

The following chart from the ECM 06Z can be described as 'effing shortwave'.

Not far off a northerly at all from that. I'm wondering if our cold anomaly in the north Atlantic is partly behind lows forming/intensifying so readily in that area?

[EastAnglian]

Hi MP-R I am sure it has a bearing but I thought the Low pressure systems were intensified by the jet roaring across the top of the system. A bit like blowing across the top of a bottle, by doing so you lower the pressure in the bottle. So the stronger the jet the more intense the low pressure system. The jet does not appear to be modelled as it was in November/December but it is still quite powerful.

Edited January 26, 2016 by EastAnglian

[chris55]

Im liking the last two frames of this mornings ECM, watch how the low just to the north of the UK dives EAST to WEST and rapidly strengthens, riding what must be a strong jet pulse coming straight out of the Acrtic.

[Frosty.]

Looking further ahead into the mid / longer range, the GEFS 6z perturbations show some wintry options so the cupboard certainly isn't bare as far as wintry weather evolving through February is concerned. It's work in progress but there is enough there to make me think we could get some arctic incursions next month...and the latest from the met office still offers encouragement to coldies hoping for a switch to a meridional pattern towards mid Feb with mid Atlantic ridge...hope is still there guys.

[Daniel*]

Quite a decent HLB in the polar region a product of the displacement, with the purple monster elsewhere...would be interesting if it approached Greenland following the path of least resistance? I think it would...an encouraging northern hemispheric profile IMO. I'd say looking further afield using my crystal ball, there is a chance currently a very remote one of a cross polar high reminds one of the model output we've seen not so long ago, which did not materialise, that would be fun - I think the tables are turning, perhaps earlier than we envisaged. Instead of putting the focus on mid Feb onwards I do not think it is wise to cast aside the first half of the month, we're seeing these variables which the likes of GP ect discuss starting to be absorbed by the models imho. I could be completely wrong but I have a inner feeling deep down winter's on the way how scientific.