Early run up to Winter 2020/2021 discussion

[sebastiaan1973]

Thanks to Simone Lee. Excellent charts for december from EC, MeteoFrance and UKMO.

https://twitter.com/SimonLeeWx/status/1316012838222090243

Edited October 13, 2020 by sebastiaan1973

[Northernlights]

 Real feeling of late autumn early winter today wth a keen north easterly wind driving showers in off the firth. Currently dull and 8c

In the arctic thread i see there has been a big increase in ice growth.I am one of the believers that feels the sun has an influence on our weather so with low solar minimum just in the past the lag factor may give us a fairly chilly winter in the next year or two.

[sebastiaan1973]

 

[Earthshine]

Met Office suggesting something colder next month 

[jules216]

Some nice dusting in upper parts of my region(Slovakia) today, about 2cm measured at the height of 909m.asl this morning, now there probably is over 10cm, will look later time permitting

[blizzard81]

Last couple of cfs runs has gone into the slightly warm category for December after being average/normal for a very long time. 

[summer blizzard]

A test a few years ago suggested the monthlies were useless less than two weeks out (except for a few months which tended to be the more extreme CET months Vs average). I have never been sold on it since.

[blizzard81]

11 minutes ago, summer blizzard said:

A test a few years ago suggested the monthlies were useless less than two weeks out (except for a few months which tended to be the more extreme CET months Vs average). I have never been sold on it since.

Yes I certainly take the cfs with a huge pinch of salt. 

[Cheshire Freeze]

Averaged mean for Dec doesn't look great now

[cheeky_monkey]

22 hours ago, sebastiaan1973 said:

Thanks to Simone Lee. Excellent charts for december from EC, MeteoFrance and UKMO.

https://twitter.com/SimonLeeWx/status/1316012838222090243

yep all three would produce a brutally cold winter here..in fact alll of them would be cold here..just not as cold as the three mentioned

[Don]

52 minutes ago, CreweCold said:

Averaged mean for Dec doesn't look great now

Probably due to it's forecast of a super Nina?  Something to keep our feet on the ground at least!

[daz_4]

3 hours ago, jules216 said:

Some nice dusting in upper parts of my region(Slovakia) today, about 2cm measured at the height of 909m.asl this morning, now there probably is over 10cm, will look later time permitting

Such a waste of a perfect winter synoptics in October. This would be legendary had it happened in December. Now we just have floods which is pretty much the worst thing to get in October.

Edited October 14, 2020 by daz_4

[swfc]

Looking at the nao- ao they do look to be going positive which kind of are reflected on the current fi runs on gfs and ec to a degree. Id suspect anything more than a month ahead ie forecasts should be left alone. The meto forecast on here were generally showing a lot of cold weather etc that never landed. For me I'd suck it and see until mid late November. Nothing scientific but there's a lot of hype most winters and it causes a lot of hyperventilating

[SqueakheartLW]

CHRISTMAS DAY PREDICTIONS FROM CFS

As promised I am giving my next Christmas update based on the CFS 9 month runs from Meteociel

These were the figures that came up in my first update

Start 26/09/2020    End 24/12/2020

Temps        0z           6z      12z         18z       TOTALS

V Mild                                                             0

Mild            2                        1             2         5

Average     4              6         5            3         18             Average to Colder than average was favoured

Cold           4              3         4            3         14

V Cold                       1                       2          3

LEADER    AV/CD    AV    AV/CD    AV/CD    AV

 

Precip               0z          6z     12z    18z    TOTALS

V Dry                                                             0

Dry                    2             4       3        7        16

Average            4             2       4        2        12            Drier than average was favoured with a tie between Average and Wetter

Wet                   4             4       3        1        12

V Wet                                                             0

LEADER        AV/WET    AV    AV    DRY    DRY

Latest Figures

Now here are the updated figures, first for the latest 10 days then both sets of data combined. The initial data contains the change from the previous 10 days in brackets

Latest

Temps        0z       6z        12z         18z       TOTALS

V Mild                                                                0 (No Change)

Mild             1                                                    1 (-4)

Average       7        7           6            3             23 (+5)  Average Temperatures predicted in last 10 days

Cold              1       3           2            5              11 (-3)  Colder than average most likely alternative option

V Cold          1                     2            2               5 (+2)

LEADER       AV     AV        AV         CD            AV

A bit of a let down after the first 10 days predictions for temperatures. It appears the CFS has shifted more towards mediocre average temperatures over colder than average. However the milder count has also fallen too which is the positive from this second update. What keeps a cold Christmas option open however is the slight increase in V Cold options in the last 10 days.

Precip        0z        6z        12z        18z        TOTALS

V Dry                                                                   0 (No Change)

Dry              2          2           2           1                7 (-9)

Average      6          4           7           6               23 (+11) Average precipitation predicted in last 10 days

Wet              2         3            1           3               9 (-3)

V Wet                      1                                          1 (+1)

LEADER      AV       AV         AV         AV             AV

There has been a definite shift in the CFS towards average precipitation compared with drier than average in the first update. The only good point about this is if one of the few V Cold options was to combine with this then a potential white Christmas could be on the cards.

Cumulative Data

Temps        0z            6z       12z       18z      TOTALS

V Mild                                                                0

Mild            3                          1           2           6

Average     11            13        11         6          41

Cold            5              6          6           8          25

V Cold         1              1          2           4           8

LEADER     AV           AV        AV        CD        AV

Precip        0z            6z         12z         18z        TOTALS

V Dry                                                                       0

Dry              4              6            5             8            23

Average     10             6           11           8            35

Wet             6              7            4              4           21

V Wet                          1                                           1

LEADER     AV       AV/WET     AV        AV/DRY     AV

The overall 20 days worth of figures shows an overall average temperatures signal at 41/80 on the count so far with a good chance of something a little bit colder at 25/80. At present a milder than average Christmas Day is looking unlikely but with 6/80 milder options it cannot be ruled out. However a V Mild Christmas day is looking like a big no at this stage with 0/80 on the count so far. A V Cold Christmas is still looking more likely than a milder one at 8/80 chance.

Precipitation is more or less looking average now after both updates combined together with 35/80 on average. Dry just scrapes into 2nd position over wet with 23/80 vs 21/80. A V Wet or V Dry Christmas are looking extremely unlikely with just 1 count between both options.

I will give my next CFS Christmas update in 10 days time again on 25/10/2020.

[sebastiaan1973]

Some information from Weer.nl & World Climate Service

Week 4: from Monday November 9 to Sunday November 15

World Climate Service and MeteoGroup, the companies we work with to formulate long-term forecasts, expect, based on their research, that high-pressure ocean areas in the Iceland and Greenland regions should become increasingly important in the course of November. In the ECMWF's expectation for this 4th week, we also clearly see this option, as well as the option in which there is a high-pressure area above Scandinavia. Together they roughly represent the heft of the calculations in this period. A western circulation gets a little more support with 20 to percent of the calculations and the other calculations are not very clear in terms of pattern. The last week of our forecast is also very average in terms of precipitation and temperatures, although you should keep in mind that only one of the three patterns can continue. Two of them, the high-pressure circulations, offer serious chances of colder weather. If it becomes the western circulation, soft and changeable lurks. In the last two weeks of November - the ECMWF now continues to calculate for another two weeks - we still see all three options. There will also be a 4th. While the probability of a Scandinavian high-pressure area decreases somewhat and that of a western circulation remains approximately the same, the idea of a pattern associated with a negative NAO index is gaining in importance, comparable to what we have now. This can also degenerate into a southern current, with mild and changeable weather. However, as winter approaches, the chances of colder options rolling out of the bus also increase. We will see for themselves. https://www.weer.nl/nieuws/2020/30-daagse-drukverdeling-blijft-lang-geblokkeerd

[jules216]

12 minutes ago, sebastiaan1973 said:

Some information from Weer.nl & World Climate Service

Week 4: from Monday November 9 to Sunday November 15

World Climate Service and MeteoGroup, the companies we work with to formulate long-term forecasts, expect, based on their research, that high-pressure ocean areas in the Iceland and Greenland regions should become increasingly important in the course of November. In the ECMWF's expectation for this 4th week, we also clearly see this option, as well as the option in which there is a high-pressure area above Scandinavia. Together they roughly represent the heft of the calculations in this period. A western circulation gets a little more support with 20 to percent of the calculations and the other calculations are not very clear in terms of pattern. The last week of our forecast is also very average in terms of precipitation and temperatures, although you should keep in mind that only one of the three patterns can continue. Two of them, the high-pressure circulations, offer serious chances of colder weather. If it becomes the western circulation, soft and changeable lurks. In the last two weeks of November - the ECMWF now continues to calculate for another two weeks - we still see all three options. There will also be a 4th. While the probability of a Scandinavian high-pressure area decreases somewhat and that of a western circulation remains approximately the same, the idea of a pattern associated with a negative NAO index is gaining in importance, comparable to what we have now. This can also degenerate into a southern current, with mild and changeable weather. However, as winter approaches, the chances of colder options rolling out of the bus also increase. We will see for themselves. https://www.weer.nl/nieuws/2020/30-daagse-drukverdeling-blijft-lang-geblokkeerd

This weather regime chart is perhaps the best representation of what they discus at weer.nl. Overal the westerly +NAO regime does not dominate until last 5 days in November, still the Atlantic ridge and -NAO have roughly the same probability. I would say we are in for intriguing November to see what will prevail. Some sort of block is evident during days 10-25 anyway, probably Scandi or Sceuro as dam values are approximately same between Oslo/Helsinki/Offenburg/Bratislava -  I would say Sceuro block likely first week of November, then all up for grabs later. I would like to see dam value mean increase for Reykjavik as a good precursor to a possible cold end of autumn. 

[Tim Bland]

Bodes well for us

[NeilN]

Are the US and the British Isles allowed to be in the freezer at the same time, or does one have to lose out? To be fair, in our case we win if that comes off!!

[NorthernRab]

15 minutes ago, NeilN said:

Are the US and the British Isles allowed to be in the freezer at the same time, or does one have to lose out? To be fair, in our case we win if that comes off!!

Strictly speaking no, both can be very cold at the same time but intense cold in the NE of the USA can mix with warmer air to the SE and cause cyclogensis, leading to a very mobile and stormy pattern over the north and west of Europe. 

[Tim Bland]

90% of cold spells in the UK are preceded by Warm spells in the NE of the US. Mild in that area kills the jet stream and allows it to buckle / shift and blocks to form to our west

[Mapantz]

3 hours ago, Tim Bland said:

Bodes well for us

..If the forecast turns out to be correct.. 

It's also possible that we end up with a mild one at the same time as them.

If a moderate Nina is on the cards, I plump for an average December and January, both temps and rainfall. And a colder and dryer February. At least for the South.

I'm thinking of February 4th 2012 when it got to -9°C, which was exceptional for here!

[damianslaw]

10 hours ago, jules216 said:

This weather regime chart is perhaps the best representation of what they discus at weer.nl. Overal the westerly +NAO regime does not dominate until last 5 days in November, still the Atlantic ridge and -NAO have roughly the same probability. I would say we are in for intriguing November to see what will prevail. Some sort of block is evident during days 10-25 anyway, probably Scandi or Sceuro as dam values are approximately same between Oslo/Helsinki/Offenburg/Bratislava -  I would say Sceuro block likely first week of November, then all up for grabs later. I would like to see dam value mean increase for Reykjavik as a good precursor to a possible cold end of autumn. 

Would be happy with the above is a month on, i.e. 10-25 December.

[damianslaw]

10 hours ago, sebastiaan1973 said:

Some information from Weer.nl & World Climate Service

Week 4: from Monday November 9 to Sunday November 15

World Climate Service and MeteoGroup, the companies we work with to formulate long-term forecasts, expect, based on their research, that high-pressure ocean areas in the Iceland and Greenland regions should become increasingly important in the course of November. In the ECMWF's expectation for this 4th week, we also clearly see this option, as well as the option in which there is a high-pressure area above Scandinavia. Together they roughly represent the heft of the calculations in this period. A western circulation gets a little more support with 20 to percent of the calculations and the other calculations are not very clear in terms of pattern. The last week of our forecast is also very average in terms of precipitation and temperatures, although you should keep in mind that only one of the three patterns can continue. Two of them, the high-pressure circulations, offer serious chances of colder weather. If it becomes the western circulation, soft and changeable lurks. In the last two weeks of November - the ECMWF now continues to calculate for another two weeks - we still see all three options. There will also be a 4th. While the probability of a Scandinavian high-pressure area decreases somewhat and that of a western circulation remains approximately the same, the idea of a pattern associated with a negative NAO index is gaining in importance, comparable to what we have now. This can also degenerate into a southern current, with mild and changeable weather. However, as winter approaches, the chances of colder options rolling out of the bus also increase. We will see for themselves. https://www.weer.nl/nieuws/2020/30-daagse-drukverdeling-blijft-lang-geblokkeerd

Would be good to compare Novembers that have featured scandi highs and following Decembers. Thinking of some such as 1985, 1988, 1993, 1995, 1996, 2010 have been followed by very different Decembers, some very mild such as 1985, 1988, others mixed such as 1993 but with some cold, others cold and snowy 1995, 1996 nd 2010. 

[Norrance]

3 hours ago, NeilN said:

Are the US and the British Isles allowed to be in the freezer at the same time, or does one have to lose out? To be fair, in our case we win if that comes off!!

Can happen. 1947 and 1979 spring to mind.

[summer blizzard]

On the US cold issue when the AO is negative both the east coast of the US and western Europe tend to be cold, when the AO is positive however a +PNA does tend to make our pattern worse but often I imagine we'd struggle for cold weather anyway.

When the AO is neutral a +PNA is probably for the worst rather than better but then without a very negative AO the UK is not normally very cold anyway.