Spring Model Discussion 18Z 6/3/13 onwards....

[PolarWarsaw]

Would suggest that people read a very sensible post by Alex in the spring chat thread and really that should also be in this thread too. I agree with him as angular momentum is pretty high ATM and having massive ramifications on the atmosphere and the GWO too.

Dont be shy...

[Mair Snaw]

192 hrs.....considerably better than the GFS if it's cold and snow possibilities you're after

Uppers still -5 or -6

No sign of anything warm or even a little bit warm from the ECM a real good set of charts if snow and cold are your thing, if you like warm weather look at the summer holiday brochure in your mag rack..

[hec1]

No sign of anything warm or even a little bit warm from the ECM a real good set of charts if snow and cold are your thing, if you like warm weather look at the summer holiday brochure in your mag rack..

Yes. Gavin.

[Duane S.]

What I feel we need now is an immediate gallop in solar activity to alter the fortunes with weather and it seems as though its not able to do so currently as the numbers simply are not high enough. Something I did latch onto was the AO trending a bit towards neutral, but still negative, the NAO is still negative too and I reckon if it were to change our output would be different.

Completely lost me here... Puting aside the solar reference, the AO is heading from deeply negative towards still negative / neutral. Combine that with a very (relatively speaking for this winter) -NAO + a very southerly tracking PFJ and we have our favourable conditions for a cold spell. Apart for the fact that they are merely pressure anomaly indicators, The AO state is much more an indirect influencer on our weather than the NAO anyway. The NAO is not going positive anytime soon. Happy days.

Outrageous charts (still) from tonight's 12z suite. When we have a set of 850 ens in March that show not one member going above the +5 isotherm for 9 consecutive days out from T+0, in DORSET for goodness sake, then we know we are on the cusp of some very interesting weather indeed. Never mind how low the mean is hitting in just a few days!

Lots of fretting about the low placement and with perfectly natural IMBYism this will continue no doubt right up to T+0. For those in the South this is very different to the Easterly of Feb, sooo much more potential in terms of heavy snowfall. However very difficult to judge whether that channel low (a genuine one as well) will wind up a tad more and head on slightly more northerly track or fill and head on a more southerly. Got to big the METO's biggest headache right now I would guess.

Incredible that in March we have this setup with as little embedded marginality as there is showing, I've never seen that before.

Edited March 8, 2013 by s4lancia

[J10]

Latest Ski blog now out

With the Synoptic charts for the nest week courtesy of the latest GFS run.

[Suburban Streamer]

precip further north on the ecm 12z compared to earlier

[Weather-history]

What I feel we need now is an immediate gallop in solar activity to alter the fortunes with weather and it seems as though its not able to do so currently as the numbers simply are not high enough. Something I did latch onto was the AO trending a bit towards neutral, but still negative, the NAO is still negative too and I reckon if it were to change our output would be different.

But NAO and AO are human inventions, they are just numerical values. The fact they are -ve is indicative of higher pressures at northerly latitudes, they will only go +ve when the higher pressures collapse. They only measure the degree of blocking, they don't cause the blocking.

[Ice BIast]

Could anyone post a link for those ECM precip charts?

Thanks.

[mushymanrob]

hmmph the ecm follows the gfs in fi suggesting a quicker then expected return to average . ill believe that when its iminant.

[nick sussex]

I think if the negative NAO is going to be west based then it might aswell become very west based because the normal halfway house situation is troughing stuck over the UK or further to the nw with a sw'erly.

SM mentioned earlier a possible surface high developing over Scandi, you can see that suggestion between 144hrs and 168hrs, at the same time you've got that low dropping south from the north.

I think its very unlikely looking at the ensembles and operational trends that the UK is going to get low pressure sufficiently south and east after 168hrs to be on the cold side of that troughing so I think a longshot would be troughing dropping south further west with a pressure rise to the east.

Upto 168hrs theres a lot going on in terms of wintry potential so if it does indeed end up with the typical west negative NAO set up after that then at least theres been a bit of interest beforehand.

Edited March 8, 2013 by nick sussex

[Suburban Streamer]

Could anyone post a link for those ECM precip charts?

Thanks.

http://en.vedur.is/weather/forecasts/atlantic/#type=prec

[kold weather]

Yep the ECM is a little further north with that precip shield, not too different from the GFS.

One word of warning though, these things more often then not correct south between 24-48hrs out, so still time for things to change...

[Summer Sun]

Deepest FI but I've found some milder air on ECM with the Atlantic coming back

GFS shows something similar a few days after

Edited March 8, 2013 by Gavin.

[cooling climate]

ECM t240 + is full of eastern promise again and I would be very wary of what the models are

showing at the moment post t144.

[Methuselah]

does it drive the synoptic pattern or does the synoptic pattern create the nao?

It doesn't drive anything, rob; it's just a derived index...see Weather History's post, above, too...

Edited March 8, 2013 by Rybris Ponce

[Gibby]

Good evening. Here is the report on the 12z output from GFS, UKMO and ECM for tonight Friday March 8th 2013.

All models are agreed on a shift to very cold conditions for all within the next 48 hours. Low pressure to the SW has pushed a succession of troughs North into the UK over the last few days and they are soon to encounter an undercut of cold air flooding out of Scandinavia over the coming few days. by Sunday night the cold NE flow will of reached all areas with rain turning to snow in places as it recedes South. A deep Low then moves East over Northern France and will probably be close enough to threaten a spell of snow across Southern England overnight Sunday into Monday. This will be accompanied by near gale bitterly cold and raw NE winds with significant windchill with snow flurries in the East moving well west at times in temperatures only a little above freezing. Then as we move towards midweek the strong winds decrease and back Northerly with a change to bright or sunny intervals and snow showers likely through this period with sharp overnight frost inland.

GFS then shows Low pressure moving SE over the UK soon after midweek with further rain, sleet and snow moving South in continuing cold conditions. Then through next weekend and beyond the pattern changes as Low pressure deepens to the West of the UK and then moves NE pulling milder SW winds and rain across all areas followed by sunshine and showers, wintry on the hills. Through the rest of FI the weather remains typically March like with wind and rain in temperatures ranging from near normal or a little below as Low pressure areas move West to East across or just to the North of the UK.

The GFS Ensembles show a 5-6 day cold spell before reasonable agreement on a recovery of surface and upper temperatures late next week and over the weekend and beyond. This will be accompanied by quite unsettled conditions with rain or showers at times, wintry through next week.

The Jet Stream shows little overall change in position over the next week or so, staying well South of the UK across North Africa and the Med.

UKMO shows the cold weather through the middle of next week but with much lighter winds by then, rather a lot of cloud at times and some sleet or snow showers scattered about. The slowly deepening low to the NW looks like it could bring rather less cold conditions with time unless it continues to sink SE over the UK. As it stands the weather would cloud over from the NW with some rain, sleet or snow later.

ECM shows the same Low holding position to the NW whilst deepening later next week and ending the very cold theme as SW winds develop with rain spreading across all areas preceded by snow for a time in the North and East but followed by chilly Spring conditions with showers, wintry on hills. By the end of the run South or SW winds return as a new Low moves into an area West of Ireland bringing rain and nearer to average temperatures, especially in the West.

In Summary it looks like next week is going to be cold and potentially wintry at times. I do not share the thoughts of many in the amounts of snowfall expected though. Through late Sunday and into Monday when a covering of snow is likely in the extreme South and prior to that in parts of East and SE England on Sunday it's the marked windchill that dominates my headlines over Monday and Tuesday with a bitter NE wind and cloudy skies with occasional snow grains or light snow flurries. Thereafter winds back North and decrease and the risk of snow is then directed to be from showers midweek and these look like being fairly scattered and as is always the case quite a few places will miss them while staying bright by day but very frosty at night. Low pressure then looks to develop and deepen close to NW Britain late in the week with a gradual ingress of milder SW Atlantic winds gradually taking control with rain or showers preceded by a spell of snow in the North and East and followed by sunshine and showers which may still fall as snow on the hills of the North.

Note: Sorry for the intermittent reports at the moment as I am currently very busy particularly at weekends. However, if my report here is missing I always try and get something up on my website as a priority. There will only be a report on the website tomorrow morning but should be back with you guys tomorrow night, hopefully for a snowmageddon report.

[legritter]

A follow on from my previouse post ,this is certainly going to be a cliff hanger for the south and indeed some other areas .it wont take much for a fair dumping of snow if all ingredients come together .any one hoping including myself take a deep breath and hang on in there till say later tomorrow .i think the met have gone as far as they can today but tomorrow should see much more confidence .it just does not seem possible with all the mild muck around in my part of the uk ,that something so magical could just be around the next corner .also some very interesting developments possible mid week next week .hats off to the Modells and please dont do a last minute Backtrack .

[No Balls Like Snow Balls]

From what I can tell the snow chances for the South on the ECM from the channel low don't look as good as the GFS but are better than the UKMO.

The South coast seems to still get a fair old whack, but the snow doesn't seem as far North as the GFS.

The track will continue to change over the next 48 hours that is for sure.

Edited March 8, 2013 by No balls like Snow Balls

[bobbydog]

Deepest FI but I've found some milder air on ECM with the Atlantic coming back

GFS shows something similar a few days after

well gavin, things must be looking good for us cold lovers when you're searching FI for mild weather!!

[fergieweather]

From what I can tell the snow chances for the South on the ECM from the channel low don't look as good as the GFS but are better than the UKMO. The South coast seems to still get a fair old whack, but the snow doesn't seem as far North as the GFS.

The track will continue to change over the next 48 hours that is for sure.

UKMO-GM modifications have the M4 as approximate delineation. Broad consensus at this range, but halfway-house approach for yellow warning at present. Either way, UK4 (extended), run with cold, nil & warm biases, generates only snow as PPN signal. That model also has M4/Bristol as approximate N'rn boundary by 12z Mon, across ESE to Sussex (ish) in so far as the southern UK event is concerned.

Awaiting latest EC-EPS and MOGREPS snow probs updates.

[-uksnow-]

UKMO-GM modifications have the M4 as approximate delineation. Broad consensus at this range, but halfway-house approach for yellow warning at present. Either way, UK4 (extended), run with cold, nil & warm biases, generates only snow as PPN signal. That model also has M4/Bristol as approximate N'rn boundary by 12z Mon, across ESE to Sussex (ish) in so far as the southern UK event is concerned.

Awaiting latest EC-EPS and MOGREPS snow probs updates.

Thanks Ian, are are any updates on totals or is the concencus to stick with what the warning says at the moment with 3-5cm over hills if I remember correctly?

[manutdmatt1986]

UKMO-GM modifications have the M4 as approximate delineation. Broad consensus at this range, but halfway-house approach for yellow warning at present. Either way, UK4 (extended), run with cold, nil & warm biases, generates only snow as PPN signal. That model also has M4/Bristol as approximate N'rn boundary by 12z Mon, across ESE to Sussex (ish) in so far as the southern UK event is concerned.

Awaiting latest EC-EPS and MOGREPS snow probs updates.

Sounds like yet another near miss for me. Thanks for the update, Ian.

[nick sussex]

I wonder whether the Scilly Isles might see their first snow for a few years, also the Channel Isles could well see some significant snow.

Looking at Ians post I think we can see the orientation of the precip is going to be in a semi circular fashion,hence its not a west east orientation.

Interesting to see Ian also mention an all snow signal, you don't always get that uniformly from these set ups, so for coastal areas less marginality helped by the low sea temps at this time, and of course those low dew points.

Given that its more than 48hrs away I'd still be wary of getting too excited, especially in the low margin for error areas.

These set ups are always liable to last minute changes.

[fergieweather]

Thanks Ian, are are any updates on totals or is the concencus to stick with what the warning says at the moment with 3-5cm over hills if I remember correctly?

No: holding fire on totals until all data assessed tonight. But check out these two profiles from GM: tell the story far better than any raw PPN charts. White: classic dynamic snow profile, 12z Mon, Lyme Bay area.... the yellow, by contrast, for Norfolk coast, midnight Mon into Tues.

[suxer]

I wonder whether the Scilly Isles might see their first snow for a few years, also the Channel Isles could well see some significant snow.

Looking at Ians post I think we can see the orientation of the precip is going to be in a semi circular fashion,hence its not a west east orientation.

Interesting to see Ian also mention an all snow signal, you don't always get that uniformly from these set ups, so for coastal areas less marginality helped by the low sea temps at this time, and of course those low dew points.

Given that its more than 48hrs away I'd still be wary of getting too excited, especially in the low margin for error areas.

These set ups are always liable to last minute changes.

Its amazing we've been following these synoptics for days,were only 48/60 hours from T Zero and we still have to be wary....Surely no last minute change now..Bye the way i always rate your assumptions and views nick..