Model output discussion - after the beast, what next?

[bluearmy]

@Summer Sun - gavin, with mean output at his time of year, getting snowfall to show is going to be tough. 

its a good tool Dec/jan/Feb to indicate how likely snowfall is but approaching April, it isn’t (if it does show then I think it’s pretty conclusive)

[Frosty.]

Looking through the GEFS 6z there are certainly some very wintry options on the table looking ahead to Easter week and even beyond..I don't think winter has finished with us yet!⛄⛄⛄⛄⛄

[Frosty.]

Although the long Easter weekend is still too far ahead to be confident with any details, the current thinking is that we will be heading into a colder than average spell with an increasing risk of frosts / ice and wintry precipitation which would include snow, especially on higher ground and further north but there is also a risk of snow further south judging by some of the GEFS 6z perturbations i posted above..I would say there is currently a good / very good chance of an unseasonably cold Easter which would also be trough dominated with a risk of snow!❄❄❄❄❄

Edited March 20, 2018 by Frosty.

[lassie23]

22 minutes ago, Frosty. said:

Although the long Easter weekend is still too far ahead to be confident with any details, the current thinking is that we will be heading into a colder than average spell with an increasing risk of frosts / ice and wintry precipitation which would include snow, especially on higher ground and further north but there is also a risk of snow further south judging by some of the GEFS 6z perturbations i posted above..I would say there is currently a good / very good chance of an unseasonably cold Easter which would also be trough dominated with a risk of snow!❄❄❄❄❄

It just won't go away from the models, this cold spell has been showing for quite a while now, looks to last longer than the one we just had too

[Derecho]

Swingometer updated again, still the trend for below average temperatures remain although these runs are getting colder. Northerlies still very much a theme.

However one development which has caught my eye is the potential for an increase in SLP to the east of Greenland. This could result in the cold pool over Scandi having an influence on things. On a few runs the cold tries to make its way here, which intensifies incoming low pressure systems. More energy sent to our east which in turns leads to a northerly earlier from the back edge of a low pressure system. Most are transient before building further again in April.

There is one ensemble member in the 00z that sends another beast our way... 

Edited March 20, 2018 by Quicksilver1989

[stodge]

Afternoon all

Apologies for the lack of reports in recent days but there is life beyond NW. The cold snap is fading into history but a second memorable event for many especially in the south west. In my part of London, another limited covering and three very cold days with Sunday only just getting above freezing.

Attention is inevitably turning toward Easter and today's medium term report takes us to Good Friday, March 30th, the start of the four-day Easter Weekend.

Kicking off with the ECM 00Z OP at T+240:

The 00Z yesterday teased with a warm looking start to Easter but today it's back to the trough with a large area of LP rolling in off the Atlantic bringing in rain and showers for most. Moderate WSW'ly winds so nothing too cold it has to be said. It does look as though the weekend from this would be unsettled with LP in charge.

GEM 00Z OP at T+240:

Something rather different as a weak HP over Scandinavia and the Azores HP split the trough. Very cold air is held out to the east over Poland and similar areas while the British Isles is in a light SSW'ly flow. Mainly dry and benign for most you'd think and the possibility of a decent Easter weekend though cold air remains close at hand.

GFS 00Z OP at T+240:

A much colder evolution. To be fair, GFS has banged the drum persistently for mid-Atlantic ridging in recent days  As the LP moves to the east, a NE'ly can set up introducing some much colder air. Further into FI and after a short colder spell, the HP, as so often happens in these evolutions, slip south but then, slightly surprisingly, builds back to the north of the British Isles.

GFS 06Z OP at T+234:

Even colder if anything. Uppers below -4 and -8 air filtering in from the NE. Showers or longer outbreaks of rain with snow to hills and some lower elevations.  Further into FI it remains cold and unsettled with the jet far to the south and strong Greenland blocking keeping cold air close to or over the British Isles.

GFS 06Z Control at T+240:

Not as cold but still unsettled with the British isles under the trough and LP close at hand. Further into FI, it becomes cold and remains unsettled with heights to the NW and LP either over the British Isles or close by.

The GFS 06Z Ensembles at T+240:

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=240

Cold and unsettled pretty much covers it with significant mid-Atlantic ridging in many Member evolutions. LP is close to or over the British Isles so some colder evolutions than others but nothing settled and not much spread.

In summary, GFS is the best if you want winter to continue and certainly a chilly Easter looks likely if the OP and Control runs from today so far verify. GEM tries to offer some heights while ECM promised a lot yesterday but has re-introduced the more unsettled evolution today. The strength of the GFS Ensembles behind the colder evolutions has to be respected however and that looks the form horse at this time so after a few decent day this week, an unsettled weekend and an improvement early next before the downhill plunge into colder and more unsettled conditions as Easter begins.

[Man With Beard]

Something interesting in the clusters. Compare the last day of March and the last day of April:

   

The change is colours must represent the change in anomaly against the seasonal norm.

I guess it indicates how heights are supposed to be much higher in April than in March!

Overall, though, heights are still favoured to the west or north-west, which means no sign of sustained warmer weather even into April.

[Summer Sun]

Latter stages of ICON 12z and the low around Iceland isn't so far south on this run as it was on the 00z

12z

00z

As a result, the chillier air clings on a bit longer but on the upside, it is drier

Edited March 20, 2018 by Summer Sun

[MR EXTREMES]

162 GFS looking like shallow heights building between Iceland and Scandinavia beast trilogy still possible.

[nick sussex]

Time to put the spring bulbs back in the shed!

Some big changes since yesterday , now pressure building to the ne .

The UKMO looks similar to the GFS at T144 hrs.

Indiana Jones and the search for the mini beast mark 2 begins ! 

 

[bluearmy]

32 minutes ago, Man With Beard said:

Something interesting in the clusters. Compare the last day of March and the last day of April:

   

The change is colours must represent the change in anomaly against the seasonal norm.

I guess it indicates how heights are supposed to be much higher in April than in March!

Overall, though, heights are still favoured to the west or north-west, which means no sign of sustained warmer weather even into April.

Jeez MWB - you have perhaps spotted a problem with anomolys when there is a more sig change in averages (ie March to April). Surely the models work to daily averages ??? Otherwise it’s ridiculous to compare across months end. The eps uppers  anomoly shows a marked drop on 1st April. Checking the actual numbers shows that there doesn’t seem to be much of an actual drop. Meteociel anomolys for gefs don’t drop off across the month end 

Weatherbell doesn’t show a drop off across the month end on gefs but does on eps

this needs a bit more investigation !!

[MR EXTREMES]

162 GFS looking like shallow heights building between Iceland and Scandinavia beast trilogy still possible.

And then it evolves into this

Notice the Azores ridge and a northeasterly looking like game on if this chart evolution is correct.

And the shallow ridge between Greenland and Scandinavia.

Another cold shot is still there.

Stratospheric events clearly helping run the cold train.

[nick sussex]

interesting these changes are coming after the short strat reversal .

Sub -20 850s now over southern Norway ! Good grief ! 

[SLEETY]

WTH the gfs thinks ANOTHER Siberian High is trying to build again.Its nearly April you know  Met talked about pressure in the NE still,so maybe it’s not a surprise,but wow anyway

Edited March 20, 2018 by SLEETY

[nick sussex]

It’s a shame we can’t get into a time machine and go back a month !

Some tasty looking synoptics , shame it’s so late. Not enough forcing here on the GFS to pull that deep cold pool sw.

Better heights to the ne would help.

[Faronstream]

Good to know that the GFS12z is an extreme outliner, neither ECMWF or GEM shows anything close to GFS for the moment and the AO value is not negative enough to let the really cold air flow down to middle latitudes

[SLEETY]

What about the Meto at 144 or are we just ignoring that then 

[nick sussex]

Just now, Faronstream said:

Good to know that the GFS12z is an extreme outliner, neither ECMWF or GEM shows anything close to GFS for the moment and the AO value is not negative enough to let the really cold air flow down to middle latitudes

The UKMO has just backed the GFS at T144hrs.

I’m ready for some warmer spring weather but as a coldie I’ll give it a few more runs to see whether the models can develop something rather outlandish for this late into March.

[Man With Beard]

GFS very close to beast mark 3 - have we gone through the wardrobe into Narnia? Or has Queen Elsa put an eternal spell on the UK? (you need young kids to get the last one!)

  

[feb1991blizzard]

18 minutes ago, nick sussex said:

Time to put the spring bulbs back in the shed!

Some big changes since yesterday , now pressure building to the ne .

The UKMO looks similar to the GFS at T144 hrs.

Indiana Jones and the search for the mini beast mark 2 begins ! 

 

I wouldn't actually want the deep fetch proper beast again as showers wont settle as much, UNLESS 1 of 2 things happen, either its a -15c to -17c which is unheard of in April, or some sort of shortwave feature develops actually in the flow itself. To me this chart here is the perfect setup, slack flow giving us another edge - evaporative cooling maybe worth a degree or so in itself, we  want a slack flow with continuous heavy snowfall with big flakes.

 

[frosty ground]

1 minute ago, feb1991blizzard said:

I wouldn't actually want the deep fetch proper beast again as showers wont settle as much, UNLESS 1 of 2 things happen, either its a -15c to -17c which is unheard of in April, or some sort of shortwave feature develops actually in the flow itself. To me this chart here is the perfect setup, slack flow giving us another edge - evaporative cooling maybe worth a degree or so in itself, we  want a slack flow with continuous heavy snowfall with big flakes.

 

Heavy wet snow...... a whole new bag of hazards. 

[Man With Beard]

2 minutes ago, feb1991blizzard said:

I wouldn't actually want the deep fetch proper beast again as showers wont settle as much, UNLESS 1 of 2 things happen, either its a -15c to -17c which is unheard of in April, or some sort of shortwave feature develops actually in the flow itself. To me this chart here is the perfect setup, slack flow giving us another edge - evaporative cooling maybe worth a degree or so in itself, we  want a slack flow with continuous heavy snowfall with big flakes.

 

I recall 3" of snow settling on this chart in April

so mega-deep uppers not always needed even in April. Though it did all melt by the next morning

[nick sussex]

GEM just jumped ship to the colder solution! 

Somethings afoot , I think this could be the models once again being slow to catch upto the strat reversal .

The strat profile does look interesting. Too early to say whether they’ve over reacted but if they haven’t then it could get interesting.

But we would need to factor in the ever increasing solar energy , so would have to tap into the coldest possible air.

[feb1991blizzard]

1 minute ago, Man With Beard said:

I recall 3" of snow settling on this chart in April

so mega-deep uppers not always needed even in April. Though it did all melt by the next morning

TBH though, I'm looking for more than 3 inches, incidentally I see 1989 as a good spring analogue although probably a bit later this time, I can see a sudden turnaround from well below average temps happening to hot weather like 25c in the space of a couple  of days, its always a very strong possibility with these blocked springs, it only needs a slight shift in the wavelength pattern.

[Summer Sun]

GEM going for a northerly at the start of Easter

High pressure close by to our west if it could move east during the weekend we may get a decent Easter day

Edited March 20, 2018 by Summer Sun