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Model Output Discussions 18z 31/01/2016


phil nw.

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Posted
  • Location: Eastbourne and Larnaca,Cyprus .
  • Location: Eastbourne and Larnaca,Cyprus .

Just as I was wondering where the MJO update has gone here it is:

MJO and other subseasonal tropical variability: • Some MJO indices are indicating a signal over the Maritime Continent, but the spatial pattern is not quite coherent yet.


• Most dynamical model MJO index forecasts depict eastward propagation of a signal through Week-2.  The amplitude of the signals vary widely from weak to extremely strong by the end of Week-2. Uncertainty due to early period destructive interference with the ongoing El Nino increases uncertainty.


Extratropics: • The extended range temperature and precipitation forecasts for the U.S. are likely to impacted by the MJO as it’s likely to disrupt the ENSO signal early, then amplify it later in Week-2 and beyond. 
 

I think looking at the divergence in the models it could be some are more prone to error due to interference from the strong El Nino. The issue with the MJO is the early stages can also be masked by Kelvin waves, the GEFS has really gone mad for amplification and generally the ECM suite has the better verification.

The ECM monthly shows a large spread, the ECM normal is less bullish about any amplitude. I think its a confused picture at the moment. Hopefully by the weekend we'll have more convergence in the outputs.

 

Edited by nick sussex
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Posted
  • Location: West Cumbria, Egremont 58m (190.3ft) ASL
  • Weather Preferences: Cold/snow winter, Warm/hot summer, Thunderstorms, Severe Gales
  • Location: West Cumbria, Egremont 58m (190.3ft) ASL
8 minutes ago, stratty said:

...with some nice results close by....arpegeuk-1-105-0.png?09-19

The Arpege model always exaggerates the snow risk.

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Posted
  • Location: Mid Welsh/English Border
  • Weather Preferences: Snow! Exciting weather!
  • Location: Mid Welsh/English Border

.....

1 minute ago, fergieweather said:

That's even if it has much influence for UK into March (latest EC Monthly prognosis attached). Mixed GloSea5 signals by early March (whilst EC Monthly goes for -ve MSLP anomaly directly to NW, maintaining +ve PPN anomaly and a fairly cool NW-WNW-W flow). But at least the new EC Seasonal & GloSea5 output peering into later Spring to early-mid Summer both look agreeable...(keep fingers crossed!) 

ps2png-atls19-95e2cf679cd58ee9b4db4dd119a05a8d-T1_8GH.png

......do you have a view on this weekend Ian for snow potential that you can share with us please? :) 

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Posted
  • Location: Castle Black, the Wall, the North
  • Weather Preferences: Spanish Plumes, Blizzards, Severe Frosts :-)
  • Location: Castle Black, the Wall, the North
5 minutes ago, fergieweather said:

That's even if it has much influence for UK into March (latest EC Monthly prognosis attached). Mixed GloSea5 signals by early March (whilst EC Monthly goes for -ve MSLP anomaly directly to NW, maintaining +ve PPN anomaly and a fairly cool NW-WNW-W flow). But at least the new EC Seasonal & GloSea5 output peering into later Spring to early-mid Summer both look agreeable...(keep fingers crossed!) 

ps2png-atls19-95e2cf679cd58ee9b4db4dd119a05a8d-T1_8GH.png

BBQ Summer..can't wait:D

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Posted
  • Location: Kirkburton, Huddersfield - 162.5mtrs asl.
  • Weather Preferences: Winter synoptics.Hot summers.
  • Location: Kirkburton, Huddersfield - 162.5mtrs asl.

The mornings fax will be interesting as to the track of the second low

fax120s.gif?0

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Posted
  • Location: Evesham/ Tewkesbury
  • Weather Preferences: Enjoy the weather, you can't take it with you 😎
  • Location: Evesham/ Tewkesbury

Hiyer Folks, as regards late weeks potential of some wintry weather for southern parts of the Uk ,don't take the models output as gospel as of now. You will see the difference between the 06z and 12z  gfs as regards of the orientation of the channel low . Small changes synoptically make big changes on the surface.! History tells us that a marginal set up like this can produce some big unexpected snowfalls....Models will struggle with this scenario right down to the line and it is a weather forecasters nightmare.  Interesting viewing from the models in the next few days as the models try to handle this developing situation,,,,,,

witney.png

witneyx.png

snowx.gif

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Posted
  • Location: Bristol/South East
  • Location: Bristol/South East
21 minutes ago, fergieweather said:

That's even if it has much influence for UK into March (latest EC Monthly prognosis attached). Mixed GloSea5 signals by early March (whilst EC Monthly goes for -ve MSLP anomaly directly to NW, maintaining +ve PPN anomaly and a fairly cool NW-WNW-W flow). But at least the new EC Seasonal & GloSea5 output peering into later Spring to early-mid Summer both look agreeable...(keep fingers crossed!) 

ps2png-atls19-95e2cf679cd58ee9b4db4dd119a05a8d-T1_8GH.png

Good news for summer?

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Posted
  • Location: Castle Black, the Wall, the North
  • Weather Preferences: Spanish Plumes, Blizzards, Severe Frosts :-)
  • Location: Castle Black, the Wall, the North
1 minute ago, wishingforsnow said:

Good news for summer?

Yes..but keep a brolly handy..just in case!:D

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Posted
  • Location: Brighton (currently)
  • Location: Brighton (currently)
25 minutes ago, fergieweather said:

That's even if it has much influence for UK into March (latest EC Monthly prognosis attached). Mixed GloSea5 signals by early March (whilst EC Monthly goes for -ve MSLP anomaly directly to NW, maintaining +ve PPN anomaly and a fairly cool NW-WNW-W flow). But at least the new EC Seasonal & GloSea5 output peering into later Spring to early-mid Summer both look agreeable...(keep fingers crossed!

ps2png-atls19-95e2cf679cd58ee9b4db4dd119a05a8d-T1_8GH.png

How can we have any faith in late spring/summer when there is such disagreement for March?

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Posted
  • Location: Evesham/ Tewkesbury
  • Weather Preferences: Enjoy the weather, you can't take it with you 😎
  • Location: Evesham/ Tewkesbury
3 minutes ago, fergieweather said:

Nothing specific. Far too much variance in main models and ENS from MOGREPS (12z EC ENS due soon) post broad agreement on frontal progression from SW late Thurs. Beyond that, it's only worth broad-brush approach. Models vary re cyclonic detail through weekend; rain v snow boundary (eg 12z EC DET brings snow through Wales, W Midlands & W Country on Sat); plus how quickly (or not) the drier, colder, sub-200m WBFL air runs south during Sunday as the ridging builds to west..  none of which is at all reliable as presently modelled.

The only clarity is that any risk of snow to lower elevation in the S will be very dependent on instantaneous PPN rates and proximity of frontal zones. Any attempt at detail beyond that is currently pointless.

Do you mean a forecasters nightmare?:cc_confused::wallbash:

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Posted
  • Location: Mid Welsh/English Border
  • Weather Preferences: Snow! Exciting weather!
  • Location: Mid Welsh/English Border
17 minutes ago, fergieweather said:

Nothing specific. Far too much variance in main models and ENS from MOGREPS (12z EC ENS due soon) post broad agreement on frontal progression from SW late Thurs. Beyond that, it's only worth broad-brush approach. Models vary re cyclonic detail through weekend; rain v snow boundary (eg 12z EC DET brings snow through Wales, W Midlands & W Country on Sat); plus how quickly (or not) the drier, colder, sub-200m WBFL air runs south during Sunday as the ridging builds to west..  none of which is at all reliable as presently modelled.

The only clarity is that any risk of snow to lower elevation in the S will be very dependent on instantaneous PPN rates and proximity of frontal zones. Any attempt at detail beyond that is currently pointless.

Thank you :) 

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Posted
  • Location: Darlington
  • Weather Preferences: Warm dry summers
  • Location: Darlington
29 minutes ago, wishingforsnow said:

Good news for summer?

Fergie has posted a bit more on spring and summer in the thread below

 

 

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Posted
  • Location: Eastbourne and Larnaca,Cyprus .
  • Location: Eastbourne and Larnaca,Cyprus .

I know its frustrating for members who want to know their prospects for snow but these set ups are very difficult to forecast.

The rain/snow boundary is likely to change between outputs and theres the added complication of the differences also in terms of available cold to draw on.

Essentially theres an area of deeper cold in Scandi but not much over central Europe, and so the way the models deal with that area in Scandi will be important.

The UKMO takes this cold west, you can see by looking at its output, you can follow that cold from T72hrs to T96hrs and then sw into the UK.

The ECM keeps this cold over Scandi and doesn't release this till later.

Its all very complicated and the UKMO can't be sure at the moment because theres these disagreements between operational runs and also in the ensembles.

Later you also have to factor in the differences upstream between the GFS/ECM/UKMO and how this might effect the longevity of the cold.

If mainland Europe was very cold the issue would just be where these shortwave lows might track because then any flow from Europe would likely be sufficient for snow.

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Posted
  • Location: North Somerset, UK
  • Location: North Somerset, UK
11 minutes ago, Summer Sun said:

Fergie has posted a bit more on spring and summer in the thread below

 

 

I can't share the EC Seasonal output but GloSea5 seasonal probabilities/ENS means are of course public domain on UKMO website.

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Posted
  • Location: Pucklechurch near Bristol 113m ASL
  • Weather Preferences: Hot summers and cold winters with snow.
  • Location: Pucklechurch near Bristol 113m ASL

Nick sums it up perfectly and those fretting on where its going to snow and how much need to realise these situations will go down to nowcasting. Many more twists and turns yet, here in Bristol I have been left disappointed many times when snow events are rain and other occasions like Feb 6th 2009 I have been surprised by heavy snow after rain was forecast.

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Posted
  • Location: New Forest (Western)
  • Weather Preferences: Fascinated by extreme weather. Despise drizzle.
  • Location: New Forest (Western)

Didn't enjoy the ECM 12z det. much; little to no development of the LP on Friday meaning cold air isn't drawn in ahead of Saturday's low, which itself deepens too early (i.e. too far west) hence brings up milder air ahead of it. That it still delivers snow through Wales, W Midlands and W Country on Saturday is noteworthy in itself.

ARPEGE is much better, with more of Friday's low and the Saturday low sliding well, while ICON does seem to be developing a closed low SE of the UK as of +78 (the limit of that model's public output range)

arpegeeur-0-102.png?12 icon-0-78.png?09-12

UKMO seems to have similar ideas but that's as far as agreement goes this evening.

 

Longer term we have seen the models wanting to have low heights converge across Greenland for a time, but this is against the MJO forcing and this is reflected by the way in which GFS, with its far stronger MJO signal, manages to find some amplification across the U.S. +168 to +192 which allows another mid-Atlantic ridge to develop and advance on Greenland. WIth the MJO in phases 5/6, a blocking scenario can't really be expected, but the deep trough could be forced far south enough for some very interesting conditions should that ridge hold on for long enough.

With a weaker MJO, low heights may well converge over Greenland for a time as per the 12z ECM det. (aided by the stratospheric vortex being in that location) but even then we see some suggestion of that trough complex moving SE toward the UK by day 10.

Just going to post the MJO projections again because GEFS appears a bit crazy in phase 7:

ALL_emean_phase_full.gif

...but here's the thing. The SSTs in that area are at record highs and so it's entirely logical to have some serious convective development once the MJO makes it there. This seems likely to be the reason why even the reluctant ECMF suddenly starts to escalate in phase 7. I'm really not sure what could be causing some of the ECM ensemble members to kill it off in that area of the Pacific.

One major uncertainty is whether the MJO will make it as far as phase 8 before we get too far into March for that to produce a strong HLB response. In fact I've done a bit of looking at past years and found that by mid-March the corresponding pattern with a waning El Nino tends to be well above normal heights across the UK accompanying a more west-based negative NAO. I suppose many would welcome that if we had a cold end to Feb and start to March, myself included!

 

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Posted
  • Location: Windermere 120m asl
  • Location: Windermere 120m asl

Its a complex set up, reliable timeframe probably 72 hours tops, dare I say it only 60 hrs maybe. Difficult to forecast what happens thereafter as the position of the trough is unknown, also the depth of cold air injected from the NE.

General theme is a cooling one with temps back to near average, but trending below by the end of the week in northern and probably central parts - unclear about southern parts in this respect.

GFS showing a deep low moving in from the NW mid next week - along way off but we see a mid atlantic ridge behind it and some very cold uppers ejected out from NE Canada to the rear of the trough.

Reading between the lines, there are signs we could see significant cold plunge from the NW by the end of the month and into early March.

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Posted
  • Location: East Ham, London
  • Location: East Ham, London

Evening all :)

Plenty of weather already this week and the weekend looks "interesting" - I don't hold out much hope for snow in lowland East London but places further north with altitude might do quite well.

The problem, as it's been the last three winters, has been the lack of heights to support a longer-lasting cold spell. The "Holy Grail" of the Azores HP retrogressing to join the Greenland HP is as always tantalisingly out of reach as there's just too much energy in the PV to stop the track of depressions.

As others have said though, plenty of cold options on the table right through to the end of next week and, to broaden the discussion further, I was musing on a comment from someone last year about it can take up to three attempts to break down a powerful PV. Well, I make this attempt two so it's likely there'll be another reset to a more zonal pattern later this month before the final attempt perhaps at the end of the month.

Looking outside the range of the models, I would suspect a more anticyclonic March might be on offer though whether that means warm or cold remains to be seen.

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Posted
  • Location: Bexhill-on-Sea, East Sussex
  • Weather Preferences: Winter Snow, extreme weather, mainly sunny mild summers though.
  • Location: Bexhill-on-Sea, East Sussex

This chart looks a lot like the ECM the other day when it was playing the villain...

gfs-0-66.png

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