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Model output discussion 02/02/20

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MetO have upgraded their warnings for Sunday. #StormDennis looks like it's going to stall right over the top of us with big rainfall totals. Could be messy for all the usual areas

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21 minutes ago, Turnedoutniceagain said:

MetO have upgraded their warnings for Sunday. #StormDennis looks like it's going to stall right over the top of us with big rainfall totals. Could be messy for all the usual areas

Gfs has it raining from Friday afternoon until the early hours Monday morning down here with winds  of up to 50 plus. The winter that keeps giving eh??

0779EB36-83D8-4B15-BDC0-920F700A591E.png

Edited by That ECM
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Some places in the south and west can look foreward to around 30 hours rain this weekend, especially west and south as the fronts stall in the south westerly flow...on a seperate note, forgetting stratosphere influence, by the end of February the PV usually starts to fragment....this chart is what you would expect mid December...grim unless you have a liking for wind and rain!

 

ECMOPEU00_216_1-2.png

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Some snow showing on the NetWx hi rez for the early hours of Thursday morning mainly for high ground on the Pennines and Yorkshire Moors.

1049071997_viewimage-2020-02-12T070407_350.thumb.png.56c5211e7668ba5511978e66ba0d9fca.png1282566747_viewimage-2020-02-12T070438_053.thumb.png.975cc6de8090c8ba07eed21f424d8196.png1178807047_viewimage-2020-02-12T070459_169.thumb.png.7aea916f09bf086f8c59297d2236bc6e.png

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Rubbish charts this morning, the PV just won't give in. Flooding will be a real problem over the next week or so:

image.thumb.png.909427efc08d6eaa6644fd425b350f66.png


Even the GFS pressure ensemble is starting to get worse - was up above 1030mb yesterday, now down to 1020mb, indicating a shift towards the Atlantic possibly being more dominant.

image.thumb.png.93e3dbbfb2eb41e8f5359e3723fe102e.png

Last nights ECM clusters still showing a westerly flow at day 12:

ec-ens_nat_z500scenarios_2020021112_300.

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Clearly GFS/GEFS responding to its forecast (juries very much still out on that) of enhanced Pacific activity but tentative signs of interest late month into March in recent runs. Amplification and a super strong vortex in its seasonal weakening state can be spectacular. 

I’m off to the Indian Ocean for a couple of weeks tomorrow, the primary driver of our ghastly winter and Australia’s awful fires. Fingers crossed I come back to total thermal shock ?❄️

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Maybe just maybe hints of Atlantic amplification at the outer range of the EPS. Let’s see if this follows through on this evening’s suite.

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2 hours ago, KTtom said:

by the end of February the PV usually starts to fragment....this chart is what you would expect mid December...grim unless you have a liking for wind and rain!

 

ECMOPEU00_216_1-2.png

Normally by long before that it’s started falling apart. We often see the first signs by mid Jan, assuming it’s formed into a fully fledged monster beforehand. The persistence of it this year, however, is notable in itself. Just a shame it has to deliver such arduous weather most of the time. The last few days have been an exception.

Down here, the rainfall hasn’t been that bad so far this month but the upcoming low looks like hitting at a different angle so trailing fronts could really be an issue if the low takes its time to clear E or NE.

Can’t wait to leave the country for a week next week!

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So with no tropical forcing or any MJO help, the main driver remains the tPV and this clearly is a brute being reinforced as we speak. At D6 it is migrating towards Greenland (epicentre) so by D11:

gfsnh-0-258.thumb.png.adf242638c5a36e4e8d57a95d0b1b7b5.png

Obviously a strong tPV to our NW is the winter killer King. I do not expect it to stay there due to the underlying atmospheric westerly-flow and what has come before. So it should cross to our north. That will preclude any Atlantic ridge for probably till the latter part of February. After D13 we await what the tPV does and if any other driver can influence the ongoing pattern. 

The GFS 06z is awful, wind and rain to D8, then maybe N/S split, drier for us southerners with a flat zonal flow so not as stormy, more rainfall from fronts crossing to the north. colder air chances>milder air chances so Scotland could get some snow after D8. For the SE winter continues to fail us.

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45 minutes ago, IDO said:

So with no tropical forcing or any MJO help, the main driver remains the tPV and this clearly is a brute being reinforced as we speak. At D6 it is migrating towards Greenland (epicentre) so by D11:

gfsnh-0-258.thumb.png.adf242638c5a36e4e8d57a95d0b1b7b5.png

Obviously a strong tPV to our NW is the winter killer King. I do not expect it to stay there due to the underlying atmospheric westerly-flow and what has come before. So it should cross to our north. That will preclude any Atlantic ridge for probably till the latter part of February. After D13 we await what the tPV does and if any other driver can influence the ongoing pattern. 

The GFS 06z is awful, wind and rain to D8, then maybe N/S split, drier for us southerners with a flat zonal flow so not as stormy, more rainfall from fronts crossing to the north. colder air chances>milder air chances so Scotland could get some snow after D8. For the SE winter continues to fail us.

Not if the pattern orientates itself favourably - January 1984 had a strong PV to the NW and that delivered polar maritime air with widespread snowfall - this week has made an effort to get there with some polar maritime zonality and PV to the NW, with snow for some areas off a zonal flow, although nowhere near as impressive as January 1984.

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30 minutes ago, North-Easterly Blast said:

Not if the pattern orientates itself favourably - January 1984 had a strong PV to the NW and that delivered polar maritime air with widespread snowfall - this week has made an effort to get there with some polar maritime zonality and PV to the NW, with snow for some areas off a zonal flow, although nowhere near as impressive as January 1984.

Yes, a possibility, but probability low, far greater chance that just the usual suspects will benefit from a PM flow. Looking at the winter so far, as we are in a repeating pattern, seems a good guide, and for most of us, south of Birmingham, snow has been MIA. 

Looking at my locale for the next 16 days, the mean uppers only go below the historical average 4-days and nothing noteworthy:

graphe9_1000_304_157___.thumb.png.c7be80c9050a4ce5a61bfb4d0e9c205e.png

Chances of snow just background noise and nothing that suggests that a one-off PM UK event like you suggest is likely to happen.

Of course, eventually that bottled up cold will be released and lets just hope it does not hit early April and ruin Spring and early Summer!

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The latest GFS update indicates a low pressure system tracking across the early hours of Thursday along with very heavy rain with very cold air besides it.

And when heavy rain bumps into cold air, then you get... SNOW! ❄️

The snow won't be present everywhere in the UK though. Northern England and some parts of Scotland should see some decent snow amounts on Thursday morning.

These snow amounts are likely to cause disruption on roads and railways.

If you live in tomorrow mornings snow alley, stay safe! ❄️

 

Edited by Zak M
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MJO cycle uodate- one of the few favourable features in the mid range at the mo-

Since my post yesterday the latest update us actually more positive ECM now goes up to phase 6 instead of 5 while GFS backs the CFS through 7 into phase 8 interestingly by 26th Feb which could be behind the snow row increase around this time on the 6z update. Some positivity amongst the negativity to pin some Hope's on.

20200212_161127.jpg

20200212_161114.jpg

20200212_160913.jpg

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The GFS is colder upto day 6 than the UKMO but the latter is much better upstream than it at that stage .

Shortwave drama in the Atlantic holds the key here , and moving forward the UKMO could develop a decent ridge ne at day 7 .

The GFS takes that further east before absorbing it into the main low upstream , and upstream is flatter than the UKMO.

The UKMO makes less of that shortwave and absorbs it more favourably , you have a cleaner flow ahead .

And if you look upstream it has the more amplified Canadian high .

That shortwave is going to cause modelling issues , because of phasing and the timing of that with the upstream low.

 

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The most vicious and potent jet streak in the entire NH this weekend is  - guess where?...

image.thumb.png.f2ef8b04f8b9e989b5fbff6b31a149fe.png

Now there's a surprise. ?

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The GFS 12z post-D10 is probably not instructive. We get a block, wedge of heights over the Kara Sea that sends the zonal flow on a more E/SE tangent compared to previous runs:

gfsnh-0-282.thumb.png.ebd987fece79770cad95b29b88780d7b.png

These wedges come and go and are more to do with ghosts in the machine at this range so probably best to treat the run as low-confidence after T240 (unless strat-trop related?).

Before that, not much change and although there are uncertainties within the bigger picture, I am not sure that pre-D10 they will get us close to snow nirvana south of the Pennines.

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Keep an eye on the GEM evolution . That’s similar to the UKMO upstream and gives an idea how that could evolve .

Factor in though that the UKMO has the cleaner evolution , so more energy will head se ahead of the amplifying upstream pattern because it’s absorbed the shortwave earlier .

PS sorry I can’t do one of my infamous point jobs which would explain things better ! 

So finally just the final bit , the shortwave stops a clean ridge developing as the upstream pattern amplifies.  The GEM is similar to the UKMO upstream but has the shortwave issue downstream , the GFS is flatter upstream than both and has the same issue .

 

Edited by nick sussex
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1 hour ago, Zak M said:

The latest GFS update indicates a low pressure system tracking across the early hours of Thursday along with very heavy rain with very cold air besides it.

And when heavy rain bumps into cold air, then you get... SNOW! ❄️

The snow won't be present everywhere in the UK though. Northern England and some parts of Scotland should see some decent snow amounts on Thursday morning.

These snow amounts are likely to cause disruption on roads and railways.

If you live in tomorrow mornings snow alley, stay safe! ❄️

 

Some model snaps:

snow.thumb.png.76874e79c2c0ac1f995253eb054e362a.pngsnow0.thumb.png.2165f99109fb55a2a9c5dd950cbc0b88.pngsnow1.thumb.png.b6ab049e068332251a60c74d09a0e82d.png

snow2.thumb.png.19f6e95eac3b5dae95a224644b5cb97a.pngsnow3.thumb.png.5fa42bb6467d69ad10999faf9298b19b.pngsnow4.thumb.png.d2b456519687b26053dc29942f269903.pngsnow5.thumb.png.d04e4bbd8e81d191b22af796e9e8bdb7.png

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The ECM day 10 chart is an absolute horror show....massive PV and low arctic heights all over. Strong +AO on display again. Wave bye bye to February.

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The agreement 48 hours on a pressure build has degenerated into a 24-48 hour dry spell. 

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2 minutes ago, summer blizzard said:

The agreement 48 hours on a pressure build has degenerated into a 24-48 hour dry spell. 

Yes, the strat signature was for it to regroup and centre over or close to the Arctic, but it also coincides with it strengthening and it is now being forecast to become a monster for "x" number of days. The D10 charts highlight that:

ECH1-240.thumb.gif.9f6fe854be8aaf65e0e0a08cfbf6e1f2.gifgfsnh-0-240.thumb.png.232fd8bbe9819af1a57bb7098a5b7190.png

Seems that it is being modelled to encroach this side of the NH more and this tPV beast has even squashed the Azores/Iberian high! This looks locked in now, so as others have said that is that for February, that is unless PM air is your thing! Doubt it is long term, thankfully we are in February, rather than early winter, so by late February hopefully it will diminish. Any hopes of an MJO signal whilst the tPV is dominant should be repressed for the time being.

Maybe at the end of Winter the experts will tell us why the sPV was so such of a powerhouse mid-Dec to Feb?

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15 minutes ago, IDO said:

Yes, the strat signature was for it to regroup and centre over or close to the Arctic, but it also coincides with it strengthening and it is now being forecast to become a monster for "x" number of days. The D10 charts highlight that:

ECH1-240.thumb.gif.9f6fe854be8aaf65e0e0a08cfbf6e1f2.gifgfsnh-0-240.thumb.png.232fd8bbe9819af1a57bb7098a5b7190.png

Seems that it is being modelled to encroach this side of the NH more and this tPV beast has even squashed the Azores/Iberian high! This looks locked in now, so as others have said that is that for February, that is unless PM air is your thing! Doubt it is long term, thankfully we are in February, rather than early winter, so by late February hopefully it will diminish. Any hopes of an MJO signal whilst the tPV is dominant should be repressed for the time being.

Maybe at the end of Winter the experts will tell us why the sPV was so such of a powerhouse mid-Dec to Feb?

At least it is good for a cold arctic and build of ice I suppose. I've already give up on this winter.

Just hope the models from now on(for me) show signs of a bottled up cold arctic until spring proper.

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There will be a way out of this, if I can't see it yet, it may be what is known as 'summer' but as others have said this is now set in for Feb into March.  

The MJO continues to be unfathomable, here GFS and ECM take:

image.thumb.jpg.cf3cc38969667aa8568d1a2ac7280733.jpgimage.thumb.jpg.983dc8865edc5f5ba5e2c933848a939c.jpg

Not even trying to get any closer together, but maybe the ECM take a possible reason for the abysmal outlook on that model today?  (Just as suggested GFS MJO output might have been part of a more positive GFS run yesterday).

Strat charts shocking, virtually no variability amongst ensembles and models, record PV.  That's what it is.  

image.thumb.jpg.0c90d4677cefc97bb34abdaf34485314.jpg

Some discussion earlier, not sure it was this thread, about the IOD and if it has declined from the massive positive values in October, why we are still getting awful winter weather.  Remember that in the early part of winter, to mid Dec, the strat and trop vortexes were disconnected.  I think the IOD as I understand it had effect in two ways, first it promoted westerlies across the UK - the Met Office Contingency planners   forecast made this clear in October, so first way - it helped prevent any high lat block scenarios from taking hold prior to mid Dec, and second way, it helped to make more likely the coupling of the strat and trop vortexes, which of course happened.  Yes the IOD has declined since but by this point winter was  already ruined - I wasn't one of those who wrote it off in October, but once the trop and strat vortex were coupled in Dec, the writing was on the wall.  This plot from Cohen's AO blog sums up what happened after, the polar cap height anomaly (averaged north of 60N) - the blues take over the whole lot from late Dec onwards:

image.thumb.jpg.3a85840980af4265c5cba2af1d8d3bab.jpg

I still maintain without the IOD, the early winter could have held some promise given other factors, but as it was it tipped us into this massively strong PV regime that it may take until April to get out of. 

Edited by Mike Poole
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Looks like plenty of action will be ongoing next week.

Some models suggesting plumes of warm air, and some models suggesting plumes of cold air - I don't mind the outcome either way!

Just seen some people looking like giving up on winter/snow if the plume of warm air verifies. Giving up on winter/snow now is still quite early! Most plumes of cold air or snow have been in March here.

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