Model output discussion - Into 2021

[Tim Bland]

Ensembles similar to this morning. op this time on the cold side in FI

[Osbourne One-Nil]

1 minute ago, weathercold said:

would you be kind enough to share your original  winter forecast? Thanks 

But not here. 

[iapennell]

5 minutes ago, weathercold said:

Ian - would you be kind enough to share your original  winter forecast? Thanks 

You will find this in the Winter Prediction part of the forum

 

Edited January 2, 2021 by iapennell

[northwestsnow]

45 minutes ago, iapennell said:

Firstly, a Happy New Year to Netweather Forum members and those eagerly watching the charts hoping for a very cold and snowy synoptic set-up.

The weatheriscool website offers a forecast for mean winds to be up to 25 metres/ second (over 50mph) from the East along 60N by the 18th January, and given the tendency for Sudden Stratospheric Warmings over the Arctic (and the associated circulation) to work downwards into the troposphere over the following three weeks this does offer hope of a frigid easterly blast in early February. BUT...

1) The QBO in November (at the 30 mb level in the stratosphere high over the Equator) was on average over 11 metres/second (24 mph) from the West.

2) Most of the Equatorial waters are hotter than usual, even though there is an East/ Central Pacific La Niña (the worst possible place for Westerly AAM considerations as it strenthens the tropical easterlies to the west but any westerlies aloft wont touch the Peruvian Andes to be dissipated). A hotter-than-usual Equator overall means an active Intertropical Convergence Zone (ITCZ) and a healthy ITCZ means stronger north-easterly Trade Winds further north- busily pumping Westerly Atmospheric Angular Momentum (AAM) into the Northern Hemisphere general atmospheric circulation (thereby also increasing the sink for Westerly AAM elsewhere). 

3) The Norwegian Sea and Barents Sea remain free of ice and are warmer than usual- as is the North Atlantic, but Canada/ Greenland are already very cold. This not only fosters cyclonogenesis in the north-west Atlantic but warmer-than-usual waters further east and north wont discourage the depressions moving into those areas.

4) There have been Westerlies over the Tibetan Plateau- up to 20 mph in recent days. But this is not enough to negate the Westerly AAM- increasing effects of 20 mph (and above) North East and Easterly Trade Winds most places between 30N and the Equator (which you can see from "Windy" website).

Much Westerly AAM is being generated by North East Trade Winds, some of which will be offset by surface Westerlies over the Equatorial Indian Ocean. But most of the generated Westerly AAM will remain intact even after the sink effects of surface Westerlies over the Equatorial Indian Ocean and the limp Westerlies over Tibet are taken into consideration. The Westerly QBO over the Equator- feeding its influence down from the Stratosphere will add Westerly AAM to the tropospheric Northern Hemisphere circulation. This only leaves higher latitudes of the North Atlantic and North Pacific as sinks for this Westerly AAM- and (given the fundamentals of Canada-Greenland to North Atlantic baroclinicity and sea-surface warmth in the European Arctic) there is a strong likelihood that the UK and points west will be seeing those Westerlies. The Easterlies predicted for the Arctic Stratosphere can only make limited headway against these fundamentals.

So, on the basis of such meteorological fundamentals, there will not be a January 1987 or a February 1986 style Great Freeze in the UK in Winter 2020-2021. There will (probably) be this coming week and another week in early February with some very cold east winds, some sharp night frosts and snow-showers (as the predicted Sudden Stratospheric Warming feeds its influence downwards) but no month-long freeze with nights below -10C and deep snow across Britain.              

Thanks Ian for your valued thoughts.

[Radiating Dendrite]

8 minutes ago, iapennell said:

Early February will likely be cold and frosty, on the strength of the Sudden Stratospheric Warming now predicted for mid-January exteme minima across the English and Welsh lowlands will be somewhere between -5C and -10C, some frost-hollow areas are likely to be a bit colder than this. In the Scottish Highland's frost-hollows (places like Altnaharra and Braemar) the extreme minima are likely to be near -15C. However, don't expect widespread heavy snowfall unless you live near the North East and Yorkshire coasts, in the Pennines or in northern/ eastern Scotland.

For temperatures to get below -10C right across Britain you ideally need three ingredients: Significant powdery snow-cover (over two inches), a very cold airmass in-place, then clear skies and light winds for the duration of at least one night (this leads to strong radiative heat loss). For this to happen you need (firstly) a cold enough airstream to bring widespread powdery snowfall that does not melt, followed by clearing skies and light winds with the very cold air being maintained. I cannot quite see how that is going to happen unless the frigid easterlies have a fetch to as far east as Russia, this lasts three or four days and then high-pressure ridges in from the north or north-east. The Norwegian Sea will likely remain too warm for a direct hit from the Arctic to bring daytime temperatures below freezing across the whole country necessary to sustain powdery snow-cover, a following ridge from a Greenland High will involve air being warmed over the far north Atlantic/ Norwegian Sea (due to northerlies falling light) and that could lead to daytime thaws before the clear still nights set in: Wet snow releases a lot of latent heat as it freezes due to radiative cooling- and such latent heat release, combined with the air above not being especially cold, would likely temper how far air-temperatures could fall.     

I have a hunch that Westerly influences off the North Atlantic will too soon become (or remain) a little too strong to permit the uninterrupted flow of air from northern Russia to the UK for three or four days that would be needed to establish widespread powdery snow-cover in the first place, let alone for this to then be followed by a high-pressure ridge then extending south-west from Scandinavia (to clear the skies and keep the airmass very cold with an east or north-easterly drift of air) to complete the frigid set-up. 

Ian, you're too specific at such range. 

I admire how much you put into such forecasts, but you cannot forecast with such accuracy at that range. 

I've yet too see one of your forecasts come to fruition. 

[XtremeUKWeather]

Is this a error ???? 2 days

[Scott Ingham]

13 minutes ago, Catacol said:

GFS smells the coffee. Ridge holds tight, undercutting a possibility. Remember - NWP is having to resolve a huge North Pacific low of record breaking depth alongside a very aggressive wave 1 displacement. I’m no expert in algorithms but to me this spells problems....

Prepare for the seesawing to include both downgrades and upgrades...but look at the ripple effect of the amplified pattern in the semi reliable. East of the pacific there is just nothing flat at all. 

I thought youd have spotted the exaxt same time period matey! 

Very encouraging that run i thought!

[chionomaniac]

Btw, I think the ECM is running with colder pooling to our east in the short term.

Just sayin’

[northwestsnow]

I can't make my mind up about UKMO...

So finely poised at 144....

Looks a classic toppler but with lows to our south is it?

[Anthony Burden]

21 minutes ago, Johnp said:

Ah thanks - I was hoping you meant the Met Office. 

Hi would imagine this meteorologist does know insiders.

[Scott Ingham]

1 minute ago, chionomaniac said:

Btw, I think the ECM is running with colder pooling to our east in the short term.

Just sayin’

Also got the same angle on the Greenie Ridge as GFS

[ICE COLD]

T96 will feel pretty cold

[That ECM]

Doing the same as gfs? Think so. Great read tonight

Edited January 2, 2021 by That ECM

[Cuban Zebra]

2 minutes ago, ICE COLD said:

T96 will feel pretty cold

That’s a huge understatement!

[Jackski4]

3 minutes ago, ICE COLD said:

T96 will feel pretty cold

Got the charts for Tuesday?

[snowice]

Ecm120

[Battleground Snow]

ECM at 120 v ukmo at 120.

Easier to see the difference on Europe wetterzentrale. 

Not much in it but ECM is better

The low to the west won't put as much pressure on the ridge on ECM

 

Edited January 2, 2021 by Battleground Snow

[Griff]

4 minutes ago, That ECM said:

Doing the same as gfs? Think so. Great read tonight

I think anything beyond 120 really is just for giggles right now. 

Interesting strat charts floating around social media as early as Monday, I won't post them here. Presumably everyone has twitter these days? 

[ICE COLD]

5 minutes ago, Jackski4 said:

Got the charts for Tuesday?

There are mate . Cold as well

[Jackski4]

Just now, ICE COLD said:

There are mate . Cold as well

Thanks mate. Appreciated;)

[weathercold]

15 minutes ago, iapennell said:

You will find this in the Winter Prediction part of the forum

 

I think this winter is proving very hard to predict. We are seeing many Lomb range forecasts going bust very early into the winter. Projected patterns aren’t behaving as they should and therefore this winter is arguably one of the hardest to call in many a year. Based on the way weather patterns look like playing out through Jan you would be a very brave individual to make a call against a notably colder and snowier winter compared to recent years.

I would go as far to say, there is every possibility (and a realistic one at that) we may well at experience one of the coldest January’s in many a year. 

[That ECM]

2 minutes ago, Griff said:

I think anything beyond 120 really is just for giggles right now. 

Interesting strat charts floating around social media as early as Monday, I won't post them here. Presumably everyone has twitter these days? 

1/2 way between Ukmo and gfs.
 

No don’t do twater can’t keep up in here.

[sheikhy]

2 minutes ago, Jackski4 said:

Thanks mate. Appreciated;)

 

3 minutes ago, ICE COLD said:

There are mate . Cold as well

You got mondays mate?

[booferking]

Ec halfway house between ukmo & gfs 144hr

[Allseasons-Si]

ECM,UKMO and gfs at 144...,ECM the middle ground here but i suspect more twist's and turns by them

and guess who is cooking the tea whilst i am trying to watch the ECM come out,...yes me

my OH can't cook...won't cook ha ha.