Model output discussion - here comes the beast!

[Guest]

20 hours ago, Fingers said:

Can anyone post country wide 850’s for the coldest days in 87, 91, 10 and 13? Interested to see where this is predicted to sit!! It looks completely bonkers!

PUTTING THE DEPTH OF THE PREDICTED COLD SPELL INTO CONTEXT 

I have noted that there have been several queries regarding how the predicted very low 850 temperatures compare to the lowest values in earlier severe winters such as the example that I quote above. This is a very good question and as nobody appears to have answered this (unless I missed it) I shall do a comparison now. I'll start off with the lowest 850s predicted by ECM on their Feb 23rd 0z run. Other models are available!  Some models have shown slightly higher or lower values at slightly different times on different runs but the ECM is pretty representative of what we "might" expect. Then I go on to show the lowest values that I could find from the archives for the years requested and a few others too working backwards. Some of these might surprise you but I've doubled checked them. Although I might have missed a few examples, some do not appear as they did not quite make my sub -14c yardstick (eg: Feb 2009 got close).

                ECM  Mar 1st  2018                                   March 11th 2013                                     December 1st 2010                                February 7th 1991                                     January 12th 1987

         

               February 20th 1986                                  January 7th 1985                                      January 9th 1982                                    January 1st 1979                                     January 30th 1972  

         

                   March 5th 1971                                       February 7th 1969                                     March 2nd 1965                                     February 2nd 1963                                 January 17th 1963 

         

                 February 26th 1962                                  February 7th 1958                                 February 2nd 1956                                   February 23rd 1947                              January 31st 1947 

        

                 January 24th 1947                                   February 21st 1942                                January 17th 1940                                    February 13th 1929                                 March 8th 1917   

        

                 February 7th 1895                                  7th January 1891                                  27th November 1890                                      27th January 1881                                9th January 1879  

        

There were some very near misses with 850s as low as -28c in western and central Europe but only -8c over here. Although the coldest March in at least 150 years was in 1883, it never managed values below -12c. Both 1947 and 1962/63 saw repeated periods of sub -10c and sometimes sub -12c but 1962/'63 never managed sub -15s and 1947 only just managed a sub -16c. The 2018 spell looks like managing values below March 2013, well below December 2010, slightly below February 1991 on a par with February 1956, January 1940, February 1895 and November 1890 and almost as low as January 1987, the coldest in the 20th century. So this should be a truly exceptional period of cold and so late in the season! In terms of longevity, it may last longer than many of those other severe spells but perhaps not as long as March 2013 (time will tell) and certainly nowhere near matching 1947 or 1962/63. Finally, note that only February 1969 saw sub -14c 850s on a northerly and that was ushered in by a polar low event (there are a number of sub -12s) but all the others are polar continental flows from an easterly quarter.

I'll be back with my Eurasia temperature report late this evening. 

 

Edited February 23, 2018 by Guest
Correct typos and check charts

[Interitus]

27 minutes ago, Luke Best said:

Here's an interesting excerpt:

"We have not seen such an absence of deep cold pool events since the 1970s, and therefore, in spite of global warming, who is to say that, following 1956 and 1987, the next extremely deep cold pool event will not visit us in January or February 2018?"

Considering that was written in Jan 2011, that's not a bad call!

A 31-year cycle!

[Snowy Hibbo]

1 hour ago, jmp223 said:

NAO lower today than it was a few days ago..increased connfidence of the cold pool remaining over the UK well into March

Hey mate, would you have a link to this forecast? Thanks.

1 hour ago, Glacier Point said:

Away from the impending brutalness, are we about to see another high amplitude MJO wave develop ?

Currently quite a large convective signal across the Indian Ocean (different indices depicting different phase locations due to large aerial extent).

Surface and particularly sub-surface temperatures very conducive in the Western Pacific.

Rapid orbit into the higher aam states entirely feasible during March, with associated blocking signal persisting to the N/NE.

Do you really think that? Because all of the NWP guidance I have seen, shows the MJO in the COD by Early March. So I personally doubt any high amplitude MJO waves occur. This would plant the seeds for your higher AAM orbit in Later March.

[MattStoke]

Can't understand why the people of Snowtopia are getting excited about the upcoming snowmaggedon freeze fest about to decent upon our frozen shores.

[IPredictASnowStorm]

that new gfs is amazing snow nearly everyday weather warnings out already !!!

[Frosty.]

It's Nirvana for coldies next week with cross model support for a major freeze, especially away from the far north and west..further east and south expect plenty of snow both in the form of showers and more persistent snow probably spreading up across the south later next week but even the areas that don't see much snow would also be very cold with severe frosts..some extremely low minima over the snow fields and severe wind chill further south due to the strong Easterly winds..the GEFS / ECM mean next week look absolutely incredible for the end of winter / early spring..it won't feel like spring through early to hopefully mid march!

Edited February 23, 2018 by Frosty.

[SMU]

44 minutes ago, Paul said:

Just wanted to follow up, as the 6z run is much snowier!

Still the same caveats though....

Thats better 30-40 expected around the mouth of the thames - 50-70 up on the tops in the jackpot areas

Nixe to see a large swathe covered over the UK

Northern England taking a pasting as well!!

Edited February 23, 2018 by Steve Murr

[I remember Atlantic 252]

Control the best! not accurate though, low resolution

https://www.meteociel.fr/modeles/gefs_cartes.php

[terrier]

Is it just me or is anyone else wishing 15.30 hours would hurry up for our next instalment of Model output. I wonder if the 12z output can upgrade the potential further. If that is possible of coarse with these Stella charts. 

[karyo]

3 minutes ago, terrier said:

Is it just me or is anyone else wishing 15.30 hours would hurry up for our next instalment of Model output. I wonder if the 12z output can upgrade the potential further. If that is possible of coarse with these Stella charts. 

It feels like it is taking forever!

[ItNeverSnowsInWindsor]

Never seen at least 5 consecutive days with high snow row values for London!

 

[sparky71a]

15 minutes ago, SizzlingHeat said:

A 31 year cycle with gale force Easterly winds which still cant deliver any snow for the Dorset coast. Unbelievable. Amazing charts, but dry and cold here which is bitterly dissapointing. If we cant get snow in a 1 in 30 year Easterly then when can we? #giveup

Patience Jedi,keep your eye on the low pressure system that may push into your area in around about a weeks time. ?

[stainesbloke]

18 minutes ago, SizzlingHeat said:

A 31 year cycle with gale force Easterly winds which still cant deliver any snow for the Dorset coast. Unbelievable. Amazing charts, but dry and cold here which is bitterly dissapointing. If we cant get snow in a 1 in 30 year Easterly then when can we? #giveup

How do you know Dorset will be dry? Initially, probably, but snow looks likely to reach the area and if low pressure starts moving up from the S....could be a lot of snow. 

[Duane S.]

18 minutes ago, SizzlingHeat said:

A 31 year cycle with gale force Easterly winds which still cant deliver any snow for the Dorset coast. Unbelievable. Amazing charts, but dry and cold here which is bitterly dissapointing. If we cant get snow in a 1 in 30 year Easterly then when can we? #giveup

We won't do as good as the east coast. Unless that is... we have a system move up from the SW and stall in the right place. That would knock their snow totals into oblivion It's no coincidence all the biggest dumpings have occured in the SW. Less quantity, more quality!

Still though, we will see plenty of convective showers down here, I am sure. Especially with a decent chance of winds veering around with a bit more SSE in them later on next week.

[tight isobar]

20 minutes ago, Steve Murr said:

Thats better 30-40 expected around the mouth of the thames - 50-70 up on the tops in the jackpot areas

Nixe to see a large swathe covered over the UK

Northern England taking a pasting as well!!

Tbf steve' taking this still into account- its viable- via looking that it screams streamer/convective..

All (barring) the wash...'red areas' noted are classic streamer teritory!..

Thus highlighting that given the snow has'nt yet fallen-and indeed accumulated" that as again convection is being underplayed...

A clear sign imo.

Also of note is the wash impaired signal also notes the horizintal flow...

Thus once again convection being clearly underplayed as we stand...

Im not complaining though..

As i feel the stakes ramping up hugely on this point.

Edited February 23, 2018 by tight isobar

[Duncan McAlister]

36 minutes ago, Bring Back1962-63 said:

PUTTING THE DEPTH OF THE PREDICTED COLD SPELL INTO CONTEXT 

I have noted that there have been several queries regarding how the predicted very low 850 temperatures compare to the lowest values in earlier severe winters such as the example that I quote above. This is a very good question and as nobody appears to have answered this (unless I missed it) I shall do a comparison now. I'll start off with the lowest 850s predicted by ECM on their Feb 23rd 0z run. Other models are available!  Some models have shown slightly higher or lower values at slightly different times on different runs but the ECM is pretty representative of what we "might" expect. Then I go on to show the lowest values that I could find from the archives for the years requested and a few others too working backwards. Some of these might surprise you but I've doubled checked them. Although I might have missed a few examples, some do not appear as they did not quite make my sub -14c yardstick (eg: Feb 2009 got close).

                ECM  Mar 1st  2018                                   March 11th 2013                                     December 1st 2010                                February 7th 1991                                     January 12th 1987

         

               February 20th 1986                                  January 7th 1985                                      January 9th 1982                                    January 1st 1979                                     January 30th 1972  

         

                   March 5th 1971                                       February 7th 1969                                     March 2nd 1965                                     February 2nd 1963                                 January 17th 1963 

         

                 February 26th 1962                                  February 7th 1958                                 February 2nd 1956                                   February 23rd 1947                              January 31st 1947 

        

                 January 24th 1947                                   February 21st 1942                                January 17th 1940                                    February 13th 1929                                 March 8th 1917   

        

                 February 7th 1895                                  7th January 1891                                  27th November 1890                                      27th January 1881                                9th January 1879  

        

There were some very near misses with 850s as low as -28c in western and central Europe but only -8c over here. Although the coldest March in at least 150 years was in 1883, it never managed values below -12c. Both 1947 and 1962/63 saw repeated periods of sub -10c and sometimes sub -12c but 1962/'63 never managed sub -15s and 1947 only just managed a sub -16c. The 2018 spell looks like managing values below March 2013, well below December 2010, slightly below February 1991 on a par with February 1956, January 1940, February 1895 and November 1890 and almost as low as January 1987, the coldest in the 20th century. So this should be a truly exceptional period of cold and so late in the season! In terms of longevity, it may last longer than many of those other severe spells but perhaps not as long as March 2013 (time will tell) and certainly nowhere near matching 1947 or 1962/63. Finally, note that only February 1969 saw sub -14c 850s on a northerly and that was ushered in by a polar low event (there are a number of sub -12s) but all the others are polar continental flows from an easterly quarter.

I'll be back with my Eurasia temperature report late this evening. 

 

One of the most informative posts I've seen on here, a great reference. Thank you!

[FetchCB]

21 minutes ago, FiftyShadesofSnow said:

Just imagine this thread and the charts showing potential in Feb 2049 then.......wonder if by then theres a GFS model going out to T10,000...imagine the carnage in here then!

ramping starts with models flip flopping from Xmas 2048 

[Chris.R]

Tableaux GEFS T850 watch for 53.5,-3.0 (my location)

 T78 - all members below -10.0. 

 T84 - 15 members below -12.0. 

T90 - peak of first cold pool - lowest member -13.3. 

 T120 - all members below -12.0. 

 T138 - peak of second cold pool - 18 members below -14.0 - lowest -16.5. 

 The signal actually get stronger the further out we go, wow. 

Edited February 23, 2018 by Chris.R

[Nick123]

It wasn't so long ago when northern England was missing out on the snow and now we're apparently going to get pasted... I urge caution as much as I want to believe it.. come Sunday night if the models are still saying the same then I will believe...

[swebby]

2 hours ago, jmp223 said:

NAO lower today than it was a few days ago..increased connfidence of the cold pool remaining over the UK well into March

Blimey, just looked at that, the mean does not go +ve until April and the 50% spread is effectively -ve until gone 16th March.  Even in April there are some significant -ve members.  I wonder where that will leave the Dec-Mar avg for 2017/18?

[Tony47]

Adding to the record low uppers debate, in my copy of Prof Gordon Manley's 'Climate and the British Scene' now sadly out of print - (Manley it was who devised the CET) - in late December, 1739, the temp in London was 15' Fahrenheit (or -9'C) with an easterly gale blowing. Temp in Holland was -17'C or around zero Fahrenheit. That would suggest 850 uppers of around minus 25'C  perhaps?

Fascinating modelling atm.

Tony47

[Rayth]

Isn’t @Bring Back1962-63 Output just ace !! 

[Duane S.]

What potential...

OK, it may've been 50,000 (and eighty) days ago but anything less than what this produced will be a massive letdown!

(jokes )

[Frosty.]

Just looked through the extended GEFS 6z and there are quite a few cold / blocked one's even by 11th March..in the meantime, next week looks incredible if you're a coldie!

[Timmytour]

1 hour ago, Frosty. said:

It's Nirvana for coldies next week with cross model support for a major freeze, especially away from the far north and west..further east and south expect plenty of snow both in the form of showers and more persistent snow probably spreading up across the south later next week but even the areas that don't see much snow would also be very cold with severe frosts..some extremely low minima over the snow fields and severe wind chill further south due to the strong Easterly winds..the GEFS / ECM mean next week look absolutely incredible for the end of winter / early spring..it won't feel like spring through early to hopefully mid march!

Nirvanania?