Jump to content
Snow?
Local
Radar
Cold?
IGNORED

Model Output Discussion - Spring 5th March Onwards 6z--->


Recommended Posts

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

Lots if interest in this morning's charts with no default westerly pattern shown longer term - always a sign changes are afoot.

 

Short term - not quite as settled as expected with atlantic troughs breaking through from west to east and it isn't until Thursday next week we begin to see a more pronounced build of heights killing off the atlantic advances.

 

The trigger to the more pronounced build of heights from the south, is a predicted change in the coverage, depth and position of the Polar Vortex over NE Canada. Heights are projected to rise over Aluetian region and these are set to pierce and probe the core of PV forcing a lobe to break away into mid north atlantic and quite far south enabling a strong build of heights to build to the east over NE Atlantic. Knock on effect, a split ineffectual Jetstream with greater energy transferred into the southern arm. The end result a quick shift of heights towards Scandinavia and lower heights over the Med propping these up. So no surprise to see GFS and ECM output this morning.

 

So all eyes on events Aleutian region a strong build of heights here and significant changes over northern hemisphere profile are likely- the first major change since November, nothing unusual in this, March always sees the northern hemisphere profile shift as it moves out of its winter base state and quite often the shift is favourable for more blocked and northerly and easterly airstream set ups.

  • Like 5
Link to comment
Share on other sites

Posted
  • Location: Fazendas de,Almeirim, Portugal
  • Weather Preferences: The most likely outcome. The MJO is only half the story!
  • Location: Fazendas de,Almeirim, Portugal

Significant upward changes in AAM tendency finally underway which illustrate fully what had being anticipated a month or so back to provide a much more interesting end to the winter period than has been the case. 

 

High amplitude GWO Phase 4/5 progression, much higher than led to the late Jan/early Feb rather marginal cold spell, underpins a large Asian Mountain Torque event which has ramifications for end of season stratospheric warming.

 

Following such events, usually the stratosphere responds in about 12 days. I would expect the Berlin site to start advertising this warming in the coming days.

 

http://www.atmos.albany.edu/student/nschiral/research/gwo/gfsgwo_1.png

 

The significance of increasing torques and poleward AAM is to decrease the strength of ridging from the tropics - which has been the feature throughout this winter and created the dominant +NAO profile in the Atlantic and to increase easterly winds across higher latitudes and thus support blocking to higher latitudes than we have seen for some considerably long time - and prior to the winter season.

 

Alongside the extra tropical GWO signal we have attendant tropical convective amplification MJO signal Phases 7/8 to support Scandinavian blocking

 

http://i.imgur.com/kBqcw9l.gif

 

If this scenario was occurring some weeks back it would be receiving much more interest on here than it is at this time

 

This winter, as everyone knows, failed to produce the -AO feedbacks that created such potent cold pooling as was seen late winter and Spring in 2013 - the wintry conditions then were quite exceptional and are not a prospect this time.

 

Much depends on orientation of the High which could simply just provide surface conditions ranging from chilly and cloudy stratus from the North Sea, to sunny with cool breezes and overnight frosts if the wind vector has more of a south easterly component. 

 

All this said, there have been plenty of March cold spells from the north east through the years - so a typical sunshine and wintry showers scenario cannot be ruled out if the High orientates itself to bring sufficiently cold uppers this way. Most especially though aided by an element of retrogression which is quite conceivable as zonal winds at higher latitude become more amenable to this happening - and if the polar vortex dislodges itself from its Canadian/Greenland home.

 

Too early to be sure, but this may happen as the effects of the +EAMT occur within the polar stratosphere :)

 

 

 

  • Like 5
Link to comment
Share on other sites

Posted
  • Location: st albans
  • Location: st albans

 

 

No sign of retrogression to Greenland as early as D10 on this run (no surprise there) so at D10: attachicon.gifgfs-0-240 (7).png

 

Likely to change again by the 12z!

 

two things IDO - a day 10 chart will never verify from any model!

 

secondly, retrogression is not likely until post day 10. interestingly, another push of cold now progged into the ne states at this juncture (T240+) which should promote another jet streak of sorts. its possible that this could, given the different atlantic profile likely at that time to what has been evident thus far this season, produce the WAA required to force that retrogression further west and deliver a proper greeny ridge. but if dr cohen thinks differently - who are we to disagree !

 

btw, that takes us to the last week of march so its likely to just depress everyone even more by delaying decent spring warmth1

Edited by bluearmy
  • Like 2
Link to comment
Share on other sites

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

two things IDO - a day 10 chart will never verify from any model!

 

secondly, retrogression is not likely until post day 10. interestingly, another push of cold now progged into the ne states at this juncture (T240+) which should promote another jet streak of sorts. its possible that this could, given the different atlantic profile likely at that time to what has been evident thus far this season, produce the WAA required to force that retrogression further west and deliver a proper greeny ridge. but if dr cohen thinks differently - who are we to disagree !

 

btw, that takes us to the last week of march so its likely to just depress everyone even more by delaying decent spring warmth1

 

 

Provided the signal for more energy to be transferred into the southern arm of a split jet is maintained then any further jet streak development could indeed be the trigger to retrogression - the two would go hand in hand.. and undercut situation..

  • Like 1
Link to comment
Share on other sites

Posted
  • Location: Reigate Hill
  • Weather Preferences: Anything
  • Location: Reigate Hill

two things IDO - a day 10 chart will never verify from any model!

 

secondly, retrogression is not likely until post day 10. interestingly, another push of cold now progged into the ne states at this juncture (T240+) which should promote another jet streak of sorts. its possible that this could, given the different atlantic profile likely at that time to what has been evident thus far this season, produce the WAA required to force that retrogression further west and deliver a proper greeny ridge. but if dr cohen thinks differently - who are we to disagree !

 

btw, that takes us to the last week of march so its likely to just depress everyone even more by delaying decent spring warmth1

 

Hi. Funny you should mention that. The GFS showing very well verification wise for D10 charts for the last couple of days. Proving it is still the King of D10 zonal flows.

 

Current chart:  post-14819-0-31771700-1425731053_thumb.p

 

GFS from 10 days ago: post-14819-0-80541700-1425731095_thumb.p ECMpost-14819-0-44704300-1425731095_thumb.g

 

The verification data for the last 2 D10 charts is 0.82 & 0.79. Bearing in mind it's average is 0.53 for the last 31 days, a very good showing:

 

post-14819-0-67075700-1425731657_thumb.p

 

Agree on both points though and I was really referring, rather ineptly :fool: , to the WAA from the Scandi ridge to Greenland on the GFS 0z, which fires up at D9 where as it was D11 on the 06z:

 

0z: post-14819-0-62774900-1425731611_thumb.p  06z: post-14819-0-18005400-1425731611_thumb.p

  • Like 1
Link to comment
Share on other sites

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

The problem at the moment for a snow showers type easterly is the depth of cold. This late into March you'd need a chunk of the PV dropping south and that cold being advected west.

 

The outputs in the winter months would be a lot more interesting and its really a case of too late now to deliver unless that is you get that PV induced cold.

 

Even then with the increase in solar energy you'd need something exceptional, if the pattern retrogresses then a northerly/ne could deliver those convective showers with chances for some temporary snow accumulations.

 

Personally I'm not a  lover of spring cold and great winter synoptics leaving you with the if only feeling, unfortunately given the MJO forecasts I fear the worst!

  • Like 3
Link to comment
Share on other sites

Posted
  • Location: Darlington
  • Weather Preferences: Warm dry summers
  • Location: Darlington

GFS like previous runs has the centre of the high at day 10 to our east, which results in a south easterly flow and temps around average

 

gfs-0-240.png?12gfs-1-240.png?12

 

GEM on the other hand has the centre of the high over the Atlantic and stretching across Scotland, that leaves us with some slightly cooler air than GFS

 

gem-0-240.png?12gem-1-240.png?12

 

Massive differences between those 2 this afternoon in the position of the high

 

What they do both agree on is it settling down by Friday 13th along with UKMO

 

gem-0-144.png?12gfs-0-144.png?12UW144-21.GIF?07-18

Edited by Summer Sun
  • Like 1
Link to comment
Share on other sites

Posted
  • Location: Castle Black, the Wall, the North
  • Weather Preferences: Spanish Plumes, Blizzards, Severe Frosts :-)
  • Location: Castle Black, the Wall, the North

I wouldn't rule out the chance of a wintry spell later this month, just had a browse through the GEFS 12z perturbations and found these. It could become interesting. We have had a mass exodus of coldies recently but some of them could be returning soon. :-)

post-4783-0-95808900-1425752487_thumb.pn

post-4783-0-67803100-1425752549_thumb.pn

post-4783-0-21241300-1425752557_thumb.pn

  • Like 2
Link to comment
Share on other sites

Posted
  • Location: Darlington
  • Weather Preferences: Warm dry summers
  • Location: Darlington

ECM is a day later than the other 3 with it building on the 14th rather than the 13th, could be quite cool around the coasts given the sea temps but more pleasant in land sunshine permitting of course

 

Recm1681.gifRecm1921.gif
 

At the end of the run we have the highs to our east and west linking up

 

Recm2401.gif

 

The 850's aren't as cold as this morning bar a short spell in the SE on the 15th when they get down to around -7 if the cloud had enough moisture in it then we could see some wintry showers given the 850's

 

ECU0-168.GIF?07-0ECU0-192.GIF?07-0ECU0-240.GIF?07-0

Edited by Summer Sun
  • Like 1
Link to comment
Share on other sites

Posted
  • Location: Castle Black, the Wall, the North
  • Weather Preferences: Spanish Plumes, Blizzards, Severe Frosts :-)
  • Location: Castle Black, the Wall, the North

I don't know if anyone has mentioned the very stormy spell heading to Scotland later on monday so I will. It looks like a very nasty spell up there with heavy rain and severe gales with storm force gusts, perhaps 90 mph or higher for a short time before calmer conditions follow...for those in the zone likely to be affected..take care.

post-4783-0-67590900-1425758288_thumb.pn

post-4783-0-09633900-1425758304_thumb.pn

Edited by Frosty.
  • Like 7
Link to comment
Share on other sites

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

Evening all :)

 

More fascinating synoptics again tonight with the AO index recording its highest value for some time;

 

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao_index.html

 

And yet the forecast is equally dramatic:

 

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao_index_ensm.shtml

 

That's a pretty dramatic decline in value in what is a short period of time.

 

http://modeles.meteociel.fr/modeles/gfs/runs/2015030712/gfsnh-0-6.png?12?12

 

That's why we have a strong AO currently - deep LP near the Pole (down to 950 MB) with at least three HP cells (including one of 1045MB over northern Siberia).

 

http://modeles.meteociel.fr/modeles/gfs/runs/2015030712/gfsnh-0-288.png?12?12

 

Yet within a fortnight the synoptic situation has transformed with much higher pressure near the Pole and lower pressure to southern latitudes creating a negative anomaly. Perhaps after months of absence, northern blocking is returning with a vengeance.

 

I'd also be interested to know if very positive AO numbers have immediately preceded negative values and whether three's any correlation between the strength of the positive anomaly in one cycle and the strength of the following negative anomaly. If there is, we could be looking at a very negative AO for the last third of the end of the month which might correspond to the MetO idea of an above average spell in mid month followed by a change to something colder later in the month.

  • Like 6
Link to comment
Share on other sites

Posted
  • Location: st albans
  • Location: st albans

note the NAO also predicted to head into neg territory. 

 

ecm extended consistent with the 00z run.  rising heights to the west/northwest and upper trough establishing scandi.  winter sypnotics seem to be arriving with spring

  • Like 9
Link to comment
Share on other sites

Significant upward changes in AAM tendency finally underway which illustrate fully what had being anticipated a month or so back to provide a much more interesting end to the winter period than has been the case. 

 

High amplitude GWO Phase 4/5 progression, much higher than led to the late Jan/early Feb rather marginal cold spell, underpins a large Asian Mountain Torque event which has ramifications for end of season stratospheric warming.

 

Following such events, usually the stratosphere responds in about 12 days. I would expect the Berlin site to start advertising this warming in the coming days.

 

http://www.atmos.albany.edu/student/nschiral/research/gwo/gfsgwo_1.png

 

The significance of increasing torques and poleward AAM is to decrease the strength of ridging from the tropics - which has been the feature throughout this winter and created the dominant +NAO profile in the Atlantic and to increase easterly winds across higher latitudes and thus support blocking to higher latitudes than we have seen for some considerably long time - and prior to the winter season.

 

Alongside the extra tropical GWO signal we have attendant tropical convective amplification MJO signal Phases 7/8 to support Scandinavian blocking

 

http://i.imgur.com/kBqcw9l.gif

 

If this scenario was occurring some weeks back it would be receiving much more interest on here than it is at this time

 

This winter, as everyone knows, failed to produce the -AO feedbacks that created such potent cold pooling as was seen late winter and Spring in 2013 - the wintry conditions then were quite exceptional and are not a prospect this time.

 

Much depends on orientation of the High which could simply just provide surface conditions ranging from chilly and cloudy stratus from the North Sea, to sunny with cool breezes and overnight frosts if the wind vector has more of a south easterly component. 

 

All this said, there have been plenty of March cold spells from the north east through the years - so a typical sunshine and wintry showers scenario cannot be ruled out if the High orientates itself to bring sufficiently cold uppers this way. Most especially though aided by an element of retrogression which is quite conceivable as zonal winds at higher latitude become more amenable to this happening - and if the polar vortex dislodges itself from its Canadian/Greenland home.

 

Too early to be sure, but this may happen as the effects of the +EAMT occur within the polar stratosphere :)

 

 

Excellent as usual Tamara, yes southeasterlies would be our best hope of pleasant sunny conditions and crisp nights, still puzzled why a respected member still insists on southeasterlies being cloudy, as you say they are most likely to bring in a chilly clear undercut though of course solar power will prevent it feeling that cold in March but I do remember some exceptional cold dewpoints on a stagnant southeasterly drift in the past in March but not sure if the continent supports that this March, still think next winter is when we'll have to wait for the next proper cold spell, just doesn't feel right to me for this Spring even with the great winter like synoptics.

  • Like 5
Link to comment
Share on other sites

Posted
  • Location: Manchester
  • Weather Preferences: Sunny and warm in the Summer, cold and snowy in the winter, simples!
  • Location: Manchester

I mentioned yesterday the Aleution ridge making in road's to the Arctic.GFS continuing the theme with dramatic Northern hemispheric results.

 

 

Yes although there may be a strong signal for a Scandi high initially there is a clear signal for retrogression and for Atlantic positive height anomalies later, perhaps even Greenland height anomalies as we head into the last third of March.

If that happened it would be very annoying and ruin any chance of early Spring warmth after any mild weather during the transition.

It would likely result in some beefy snow showers though.

Edited by Mucka
Link to comment
Share on other sites

Posted
  • Location: Castle Black, the Wall, the North
  • Weather Preferences: Spanish Plumes, Blizzards, Severe Frosts :-)
  • Location: Castle Black, the Wall, the North

The 18z shows another very windy spell later next week, especially northwest scotland although not quite as stormy as late Monday, still disruptive with another spell of heavy rain but that heralds a change, as the low responsible moves north to the east of Iceland we see high pressure finally allowed to build in properly after almost a weeks delay. This run shows a cold Easterly setting in by early in week 2 with a lot of cloud and a few wintry showers but some clearer and sunny spells too, with a strong E'ly to SE'ly flow it would feel bitterly cold during the first half of week 2 and for the east and northeast, a risk of sleet and snow flurries..it would feel very cold.

post-4783-0-84370100-1425768948_thumb.pn

post-4783-0-55903700-1425768954_thumb.pn

post-4783-0-02121600-1425768960_thumb.pn

post-4783-0-73605700-1425768964_thumb.pn

post-4783-0-01158200-1425768971_thumb.pn

post-4783-0-74307800-1425768976_thumb.pn

post-4783-0-86586000-1425768983_thumb.pn

post-4783-0-09990600-1425768989_thumb.pn

post-4783-0-40887300-1425768996_thumb.pn

  • Like 2
Link to comment
Share on other sites

Posted
  • Location: Reigate Hill
  • Weather Preferences: Anything
  • Location: Reigate Hill

There was always a good chance that retrogression on the GFS op was again a figment of it's imagination bearing in mind it's bias since the upgrade. Today the core Scandi heights slowly sink SE into Europe:

 

D10: post-14819-0-00394200-1425799154_thumb.p D13: post-14819-0-51897200-1425799153_thumb.p

 

TBH the mean never supported the op and the signal was always a sinking high. However it remains fluid after around D10 so I wouldn't rule anything out just yet.

 

GEM keeps returning to its theme of pushing the Scandi high Russia bound so by D10: post-14819-0-83107400-1425799385_thumb.p

 

ECM keeps a Scandi High from D5-10: post-14819-0-27858200-1425799478_thumb.g post-14819-0-93273500-1425799477_thumb.g

 

All these options remain on the table and its a case who you trust around the D10 mark.

 

In the nearer term the models are finally resolving the storms for the upcoming few days. Tomorrow:

 

post-14819-0-97188800-1425799679_thumb.g post-14819-0-34001500-1425799680_thumb.p post-14819-0-79014500-1425799680_thumb.p

 

Wednesday: post-14819-0-36147600-1425799779_thumb.ppost-14819-0-67975400-1425799779_thumb.p

 

The D5 storm still showing differences with the UKMO; as it sometimes is a run or two behind the curve ball:

 

post-14819-0-00159000-1425799937_thumb.g  Compared to ECMpost-14819-0-80608600-1425799982_thumb.g GFSpost-14819-0-29246700-1425799982_thumb.p

 

ECM was similar to the UKMO yesterday but have moved closer to GFS this morning. GEM is similar to the GFS.

 

For the south temps continue to be forecast for between 1-2c above average for the next 8 days and rainfall remains relatively low:

 

post-14819-0-97952800-1425800184_thumb.g  post-14819-0-28655600-1425800185_thumb.g

 

With the CET anomaly heading for +2c above normal, the first half of March looks a mild one. Too early to be confident further on. No point talking about the GEFS after D11 as they are all over the place suggesting changes are happening and it has not got a clue.

Edited by IDO
  • Like 1
Link to comment
Share on other sites

Posted
  • Location: st albans
  • Location: st albans

There was always a good chance that retrogression on the GFS op was again a figment of it's imagination bearing in mind it's bias since the upgrade. Today the core Scandi heights slowly sink SE into Europe:

 

.

And tomorrow? your initial statement is rather too definitive for me IDO. there is still is a chance that the pattern won't retrogress but I'd say it's no different to yesterday. Using the mean to back up a retrogression argument in fi is tough without using spread charts. At a range beyond T200, the mean will generally default to a zonal appearance, especially the further out you go.

  • Like 3
Link to comment
Share on other sites

Posted
  • Location: Reigate Hill
  • Weather Preferences: Anything
  • Location: Reigate Hill

And tomorrow? your initial statement is rather too definitive for me IDO. there is still is a chance that the pattern won't retrogress but I'd say it's no different to yesterday. Using the mean to back up a retrogression argument in fi is tough without using spread charts. At a range beyond T200, the mean will generally default to a zonal appearance, especially the further out you go.

 

Hi. Normally I would agree. But since the GFS upgrade I do not trust it with respect to HLB signals. So I need to see other models and the GEFS to also trend that way. No significant cluster on the GEFS or the GEM ensembles and the ECM op doesn't look even close this morning:

 

post-14819-0-62160100-1425801054_thumb.g

 

Not that I believe in that chart will verify. One thing I have noticed with the new GFS is that when it suddenly throws a HLB it runs with it for a few runs before moving away from it. That looks like the case this morning. Also it looks like the GEFS MJO is reducing amplitude in phase 7 and maybe will avoid phase 8 (Greenland High):

 

post-14819-0-22759900-1425801406_thumb.g

  • Like 1
Link to comment
Share on other sites

Posted
  • Location: Castle Black, the Wall, the North
  • Weather Preferences: Spanish Plumes, Blizzards, Severe Frosts :-)
  • Location: Castle Black, the Wall, the North

Ecm keeps showing a deeper cold pool later in the run so it must be taken seriously, after all, it was also the ecm which was the first model to show a significant delay to the anticyclonic spell so I think it's one to watch.

post-4783-0-90402700-1425801978_thumb.pn

post-4783-0-93926900-1425801984_thumb.pn

  • Like 1
Link to comment
Share on other sites

Posted
  • Location: Castle Black, the Wall, the North
  • Weather Preferences: Spanish Plumes, Blizzards, Severe Frosts :-)
  • Location: Castle Black, the Wall, the North

The GFS 00z shows Scotland in particular having some very windy spells in the week ahead, tomorrow's is severe with gusts to 90 mph, the second and third less strong but still with 60 mph gusts, bouts of heavy rain too but by Friday it's all change with high pressure firmly in charge and it strengthens its grip through next weekend into week 2. Following a very mild spell, it turns colder from the east next Sunday into following week, feeling bitterly cold despite what the thermometer shows but it doesn't last, gradually winds back more southerly as Atlantic lows push up against the blocking high which gives ground. To be honest I wasn't expecting the Atlantic to push in so soon as these blocking scandi highs can sometimes last 10 days or more but in any case, from Friday it's HP in charge for a while.

post-4783-0-62337600-1425803901_thumb.pn

post-4783-0-49850500-1425803913_thumb.pn

post-4783-0-90695500-1425803919_thumb.pn

post-4783-0-81758900-1425803925_thumb.pn

post-4783-0-03274100-1425803932_thumb.pn

post-4783-0-92660900-1425803939_thumb.pn

post-4783-0-76258100-1425803948_thumb.pn

post-4783-0-20624500-1425803963_thumb.pn

Link to comment
Share on other sites

Posted
  • Location: st albans
  • Location: st albans

bastardi's saturday summary on weatherbell this week is worth a watch (as per usual). not sure when its freely available but definitely by tomorrow. bear in mind that he is a coldie but he has had a decent winter upstream with his predictions.

Link to comment
Share on other sites

Posted
  • Location: Warminster, Wiltshire
  • Location: Warminster, Wiltshire

 To be honest I wasn't expecting the Atlantic to push in so soon as these blocking scandi highs can sometimes last 10 days or more but in any case, from Friday it's HP in charge for a while.

Is it?

 

Last weekend we were apparently due HP for much of the rest of March once the early week PM flow dissipated. True it's been fine for 3/4 of the UK since Wednesday, but the NW 1/4 has had a soaking and that front is now heading SE. So that's been 4 fine days for the 3/4 - hardly the rest of March!

 

Then rather than the HP reasserting itself we have a series of deep lows modelled for this week before, apparently, a HP takes over. I predict that by next weekend, while we may have a HP for several days, it's longevity will not be assured!

 

A similar early month HP outlook for February was overrun by much lower pressure and to me it seems the models over-predict HP past the supposedly reliable 5 day period then revert to a more fluid movement of the highs and lows as time nears.

 

  • Like 1
Link to comment
Share on other sites

Guest
This topic is now closed to further replies.
×
×
  • Create New...