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Stratosphere temperature watch - 2016/17

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17 minutes ago, iapennell said:

The North Atlantic looks set to dominate for the remainder of the winter, possibly even more so towards March because by then the effects of the record Westerly QBO (15 m/s and 9 m/s at 30 mb and 50 mb respectfully) will have fed into the Northern hemisphere General Circulation- there is a time lag of two-three months typically. The far North Atlantic is still warmer than normal overall and Greenland/NE Canada are at their coldest by February which will encourage an even stronger baroclinic gradient across the far North Atlantic just south of Greenland (this is a site of major cyclogenesis for the deep depressions that pass to the north of Britain and bring strong west or SW winds). None of this portends any strong high-latitude blocking heading through the second half of the winter and towards spring.

The strength of the Westerlies in the sub-polar Stratosphere looks set to remain strong (Westerlies at 10 mb over 60N projected to be around 30 m/s over the next 10 days- see the Weatheriscool.com site) and there are no indications that this will shift radically in the coming days. Given the patterns of temperature across the far North Atlantic and far North Pacific combined with the fact that the central Arctic typically reaches it's coldest during February-early March this is all supportive of a healthy tropospheric Circumpolar Vortex with high-pressure in the sub-tropics and over continental interiors but persistent strong cyclogenesis up-wind of higher-latitude western continental margins such as NW Europe.   

Despite what you say about the atmosphere being conducive to rapid cyclogenesis which usually promotes deep low pressure systems and consequent storms/gales and heavy rain, we are being spared such fayre so far this winter, indeed how quiet has the 'atlantic' been since August in this respect - we've barely had a day of heavy rain since then - compare to autumn-winter periods of 2013/2014 and 2015/2016.. whether we can maintain such benign calm conditions for the rest of the winter remains to be seen, but I don't see a rpaid change in fortunes anytime soon, and traditionally things go quieter during the latter part of winter/early spring - which if verifies will mean we have had a very quiet dry preety much storm free 6 months - not often that happens..

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2 hours ago, Interitus said:

Well as December had the highest QBO of any winter month in the NOAA data linked above, then obviously your first statement is absolutely correct. However, unless you are less than six years old then you would've experienced December 2010 with QBO 10.97.

Even colder? February 1986 QBO 10.15.

There is no statistical correlation between CET and QBO for December or February, and a tentative 0.24 for January.

However, the data does appear to show cooler CET for eQBO, worth around 0.2°C for December and February and a more notable half degree for January (though Jan 1963 skews this somewhat) and this persists after taking into account that eQBO is stronger than wQBO so the mean is easterly.

When looking at more extreme QBO values greater +/- 1 sd the picture is more muddled - though there is a problem with small and uneven sample sizes so must be taken with a pinch of salt.

The December difference is the same, but both are above average (+0.2 / +0.4).

January seems more clear cut with means of 3.47°C (1963 is worth 0.3 degrees) and 4.75°C - may be reflected in the weak correlation noted above and worthy of some investigation, though is not statistically significant - we have had a prolonged run of generally mild Januaries regardless of QBO.

February has no difference in CET between extreme east or west QBO - this is perhaps the most interesting bearing in mind links between QBO and late winter stratospheric vortex strength.

But, to say that QBO is responsible for whether we have notable cold spells is more than a bit of a stretch.

@Interitus; You are correct in that the Quasi Biennial Oscillation is far from the only influence on the British winter weather, but it is an important one. Other influences include the phase of the Sunspot Cycle, sea-ice extent in the Arctic, El Ninó/La Niná, snow-cover over Eurasia and sea-surface temperature patterns in the North Atlantic. Therefore, if you pick even quite a big sample of winters and the QBO over preceding months (not at the same time) you will not get a very clear correlation.

You refer to Winter 1985/86 which was indeed very cold, yet which had a Westerly QBO. Also in that winter Arctic sea-ice was well above the average for the season and northern margins of the North Atlantic were a good deal colder than now; regardless of QBO phase this would have pushed the depression tracks at higher latitudes further south and giving Britain a real chance of finding itself in cold polar air. This particular winter also occurred near Sunspot Minima and (since it is well known that there is a link between an active Sun and increased winter storminess in high latitudes) this also supports weaker higher-latitude Westerlies and greater scope for blocking. Another factor is that Eurasia was very cold and snow-covered (more than usual) during Winter 1985/86 and this would have pushed the strong Westerlies in the Circumpolar Vortex southwards over the continent-to the extent that these strong Westerlies would have hit the Pamirs of Central Asia. When that happens the atmosphere loses a lot of the Westerly atmospheric momentum it acquired on it's high-altitude passage north from the Equator and there is then less Westerly momentum to feed into Westerlies at the surface at higher latitudes.

This does not mitigate the effect of the Quasi Biennial Oscillation: When that is Westerly that is like a store of Westerly angular momentum in the atmosphere that can later strengthen the Westerlies further north, leading (other things being equal) to a stormier but milder winter for the united Kingdom. When strong Easterlies dominate the Equatorial Stratosphere, however, this is a store of easterly momentum that can slow down Westerlies in higher latitudes leading to drier winter conditions over Britain. You are right that in recent years we have had a run of mild winters with the QBO being Easterly as well as Westerly- The Sun has been in an active phase and solar activity will have helped to promote mild wet Westerlies even when the QBO has not. The retreated extent of Arctic ice and the far North Atlantic and Pacific being a little warmer than normal also encourage storm tracks to move further north, this means Britain is invariably on the warm [south-westerlies] side of depressions.

Strong El Ninós tend to encourage mild and stormy winters over Britain by strengthening the Intertropical Convergence Zone and (thus) the north-easterly Trade Winds to the north of the ITCZ. Stronger NE Trade Winds gain Westerly momentum for the Northern Hemisphere circulation through frictional interaction with the underlying surface and this (eventually) translates into stronger Westerlies at higher latitudes. But the Quasi Biennial Oscillation is still a major player.

For the coldest, most high-latitude-blocked winters in Britain you need all the major variables acting together to weaken the Circumpolar Vortex (and push it equator-wards): A very quiet Sun needs to be combined with a strongly easterly QBO (like 20 m/s or more) with a cold North Atlantic and pack-ice extending as far south as Iceland (which would help shift storm-tracks southwards). A weak La Niná would also weaken the Hadley Circulation and lead to less Westerly atmospheric momentum being pushed polewards. Extreme cold and snow-cover over all Eurasia north of 40N (and very cold conditions over western Canada and NW USA) would also help displace the strongest upper Westerlies southwards (and somewhat downwards) so that they impacted the Sierra Nevada and Pamirs with force (and losing much of the remaining Westerly AAM that could still upset Britain with any mild incursions off the North Atlantic). Should all these factors come into play around November-time a severe winter would be a foregone conclusion!

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29 minutes ago, damianslaw said:

Despite what you say about the atmosphere being conducive to rapid cyclogenesis which usually promotes deep low pressure systems and consequent storms/gales and heavy rain, we are being spared such fayre so far this winter, indeed how quiet has the 'atlantic' been since August in this respect - we've barely had a day of heavy rain since then - compare to autumn-winter periods of 2013/2014 and 2015/2016.. whether we can maintain such benign calm conditions for the rest of the winter remains to be seen, but I don't see a rpaid change in fortunes anytime soon, and traditionally things go quieter during the latter part of winter/early spring - which if verifies will mean we have had a very quiet dry preety much storm free 6 months - not often that happens..

@damianslaw; I certainly hope so, certainly where we live in the north of England we could well do without a repeat of the extreme flooding of December 2015 and the devastation that this caused. I am confident we will get nothing like that over the next couple of months (last December broke records for rainfall), by February the North Atlantic is colder than in early winter and this supports less evaporation and thus less rainfall as a result. There is also scope for optimism in that our friend, the north Atlantic Cold Blob has re-established itself south of Iceland and this could help weaken any cyclonic activity headed towards Britain. All the same, the QBO is at a record Westerly extent (15 m/s at 30 mb and 9 m/s at 50 mb as averaged through December) and sea-surface temperatures in the far North Atlantic (i.e from Greenland to the northern Norwegian Sea) are still seasonally above normal by 2 to 3C; combine this with the fact that sea-ice over the Central Arctic is thickening and that that area gets very cold by February then there is the prospect of some severe gales in late February/March. March used to be associated with gales in northern Britain and some of the underlying factors look like they may come together to deliver some real old-fashioned March gales this year.

There is (hopefully) a possibility that the warmth of the far North Atlantic and the reduced extent of Arctic ice in the European Arctic pushes the storm tracks further north so that much of central and southern Britain misses these March gales entirely!  

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Teleconections.

IMG_3107.PNG

-EPO currently.

IMG_3106.PNG

North Pacific HP replaced by Low pressure systems. Imitate pattern change. 

Wave train from MJO sector 5IMG_3108.GIF

Low pressure in East Asia allows warming (East Asia MT event). IMG_3105.PNG

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19 minutes ago, KyleHenry said:

 

Low pressure in East Asia allows warming (East Asia MT event). IMG_3105.PNG

Here we go again, what are you on about? 

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1 hour ago, Interitus said:

Here we go again, what are you on about? 

Nice attitude you got there. You asked me this question last year and that answer still stands.

Low pressure in North Pacific allows Indian Ocean rossby wave energy transfer to lower/upper Stratosphere via Hymalayan mountain range. 

Low pressure systems spawning from the Trop PV over Kamchatka region adds the amplification to allow Rossby wave energy to progress to 10hPa level. 

Enough energy=SSW.

High pressure in N Pacific=No East Asian mountain torque event.

 

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The European warming in the stratosphere next weekend on 30 hPa (picture 1) may be helpful to enable a change in weather patterns over Europe. The ECMWF run today (picture 2) shows a ridge, that possibly for the first time will not be overrun by the so far very dominant westerlies. Without counteraction of the stratosphere this time, this may be the best opportunity until today to extend the Russian blocking into Scandinavia.

http://www.netweather.tv/index.cgi?action=stratosphere;sess=

http://www.meteociel.fr/modeles/ecmwf.php?ech=72&mode=1&map=1&type=1&archive=0

Also noticible: the synopsis in East-Asia and the Pacific is encouraging wave2 activity, putting pressure on the stratospheric PV

Netweather 8-1-2017.PNG

Run enseble EC 8-1.PNG

Edited by Paul123
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On 06/01/2017 at 20:21, damianslaw said:

Despite what you say about the atmosphere being conducive to rapid cyclogenesis which usually promotes deep low pressure systems and consequent storms/gales and heavy rain, we are being spared such fayre so far this winter, indeed how quiet has the 'atlantic' been since August in this respect - we've barely had a day of heavy rain since then - compare to autumn-winter periods of 2013/2014 and 2015/2016.. whether we can maintain such benign calm conditions for the rest of the winter remains to be seen, but I don't see a rpaid change in fortunes anytime soon, and traditionally things go quieter during the latter part of winter/early spring - which if verifies will mean we have had a very quiet dry preety much storm free 6 months - not often that happens..

Yes has been a pretty quiet winter thus far and it wouldn't surprise me if it continues that way.

Interesting is how the stratospheric polar vortex this season has been hassled throughout. Part of the reason why it has been a quiet winter thus far?

npst30.png

Edited by Weather-history

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Interitus, I am in agreement with you 100% in your excellent and detailed post, right up until the end paragraph.

"So it appears that there is a tropospheric Rossby wavenumber 1 forcing originating from ridging on the Atlantic side, propagating to the stratosphere creating a baroclinic vortex. The mechanism as described accounts for both the vortex shape and warming observed. No need for spurious or speculative mountain torques or wave interactions, just standard troposphere/stratosphere wave/mean flow interaction."

Is it spurious? Is it not merely observing the model output and commenting on why the output is displaying the increased activity in the East Asian Strat sector?

IMG_3108.GIF

MJO chart which I originally posted showed slight amplification towards sector 5. 

Model reads that as poleward propagation of Rossby/gravity waves. 

Results in forecasted chart.IMG_3115.PNG

Wave signals 1&2 remain undefined at this range. I don't know what energy will emit from MJO forecast if any. Too early to call. 

Supporting factors for giving it any credence: 

La Niña phase default is Millar B patternIMG_3092.JPG

Also reason why SSWs occur less  in La Niña as Rossby waves struggle to permeate easterly winds created by N Pacific HP ridge. 

That has changed due to N Pacific HP retrogressing to create upcoming -AO phase. 

Reversation to Westerly winds as Low pressure systems are forecast for Kamchatka region and possible Rossby wave propagation. Possible if models are correct. 

Origin of the added energy forecasted was the basis of my original post. 

 

 

 

 

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IMG_3116.GIF

Stratosphere warming event.  Wave 1 is already circumnavigating. 

Is this wave 2 from MJO activity? 

Time will tell.

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17 hours ago, KyleHenry said:

Interitus, I am in agreement with you 100% in your excellent and detailed post, right up until the end paragraph.

"So it appears that there is a tropospheric Rossby wavenumber 1 forcing originating from ridging on the Atlantic side, propagating to the stratosphere creating a baroclinic vortex. The mechanism as described accounts for both the vortex shape and warming observed. No need for spurious or speculative mountain torques or wave interactions, just standard troposphere/stratosphere wave/mean flow interaction."

Is it spurious? Is it not merely observing the model output and commenting on why the output is displaying the increased activity in the East Asian Strat sector?

IMG_3108.GIF

MJO chart which I originally posted showed slight amplification towards sector 5. 

Model reads that as poleward propagation of Rossby/gravity waves. 

Results in forecasted chart.IMG_3115.PNG

Wave signals 1&2 remain undefined at this range. I don't know what energy will emit from MJO forecast if any. Too early to call. 

Supporting factors for giving it any credence: 

La Niña phase default is Millar B patternIMG_3092.JPG

Also reason why SSWs occur less  in La Niña as Rossby waves struggle to permeate easterly winds created by N Pacific HP ridge. 

That has changed due to N Pacific HP retrogressing to create upcoming -AO phase. 

Reversation to Westerly winds as Low pressure systems are forecast for Kamchatka region and possible Rossby wave propagation. Possible if models are correct. 

Origin of the added energy forecasted was the basis of my original post. 

 

Upon seeing an area of stratospheric warming the obvious assumption would be that the source is from below somewhere in the same general area. However it is not the case, as the warming seen in an SSW is due to the adiabatic warming of air as it descends rapidly, not directly due to energy heating from below . The forcing on the vortex causing the warming can originate from the other side of the northern hemisphere. Recall the series of forecast charts above showing wave 1 emanating at 500mb from the Atlantic side leading to wave 1 over the Bering Sea/Alaska area at 10mb - well here is the exact situation from the paper Blocking Precursors to Stratospheric Sudden Warming Events (Martius et al 2009) - the top line of images is a composite of troposphere blocking leading to wave 1 displacement SSW (bottom images wave 2)  -

grl26066-fig-0002.png

An alternative view of this can be seen in cross-section in a height/longitude plot and here is a fairly similar example from Influence of the vertical and zonal propagation of stratospheric planetary waves on tropospheric blockings (Kodera et al 2013) for December 2008. The top left image shows the 10mb wave 1 forcing slightly further east over Alaska, and the middle right image shows how this is vertically linked to wave 1 at lower levels over the north Atlantic and northern Europe -

kodera.png

With regards to the north Pacific HP ridge, contrary to it being a barrier to Rossby waves, it is integral to them. In simple terms, a Rossby wave can be seen by the jet stream meandering around a series of troughs and ridges with the north Pacific ridge being one of them - this explanatory diagram conveniently shows a ridge not too far away off the west coast of N. America -

rossby.waves.jpg

In these blended pressure/jet stream charts from meteociel, the current hp can be seen forming around the 28th December to the south of the jet stream which bulges northwards forming a ridge of a Rossby wave -

blend1.png

A couple of days later the hp displays some nice features of Rossby wave amplification - anticyclonic wave breaking -

blend2.png

notice how the jet stream curls round the high very much like this textbook example in the middle of the right hand side -

slide_3.jpg

and in this same example the top left image of an anticyclonic cut-off is where we are today, with the jet gaining strength to the south with a string of low pressures and the hp gradually dissipating and moving away -

blend3.png

Now, the mountain torques, MJO/tropical forcing and baroclinic cyclogenesis etc you describe can all generate and shape the Rossby waves, but they need to explain the large anticyclonic wave break such as the one also present on the Atlantic side in the last image in order to create the forecast stratosphere wave 1 forcing.

 

 

 

Edited by Interitus
reworded
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From reading the excellent posts above, my impression in very simplified format is;

  • The vortex is happy when it has good alignment in the vertical, with little tilt taking place. Small perturbations may occur peripherally but are easily shrugged off.
  • Forcing from the tropics and/or mountain torque events to name a couple can distort the lower levels of the vortex, often sufficiently for a substantial misalignment with higher up levels to occur, resulting in a tilted vertical profile with regions of warming and cooling as air descends or rises, respectively.
  • Distortion may then extend to higher levels as well, with misalignment and tilt occurring between those and the levels above. This may eventually culminate in warming right at the top of the stratosphere (1 hPa) which if strong enough can trigger a SSW/MMW with anomalies propagating back down.

I'm not very sure about that last sentence though.

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2 hours ago, Singularity said:

From reading the excellent posts above, my impression in very simplified format is;

  • The vortex is happy when it has good alignment in the vertical, with little tilt taking place. Small perturbations may occur peripherally but are easily shrugged off.
  • Forcing from the tropics and/or mountain torque events to name a couple can distort the lower levels of the vortex, often sufficiently for a substantial misalignment with higher up levels to occur, resulting in a tilted vertical profile with regions of warming and cooling as air descends or rises, respectively.
  • Distortion may then extend to higher levels as well, with misalignment and tilt occurring between those and the levels above. This may eventually culminate in warming right at the top of the stratosphere (1 hPa) which if strong enough can trigger a SSW/MMW with anomalies propagating back down.

I'm not very sure about that last sentence though.

The 1hPa level I find has more factors of influence.IMG_3124.JPG

First you've got the increase in wave altitude that progresses during January. 

Added to that we have to look above and towards the solar output. 

Lower 10.7 radio flux creates shrinkage of the thermosphere and the mesosphere as Earth enters solar minimum. 

Effects of energetic particles from the steady increase of protons released from coronal holes on sun's surface.IMG_3119.JPG

Them the chemical reactions at that altitude with Ozone and CO2 and in some years with cooling effect of SO2 with volcanic eruptions. 

Then return to Rossby wave breaking which increases O3 in the Northern hemisphere.

Kenetic energy contained within the Rossby waves at the particle level.

IMG_3120.GIF

Then differations in geo barclinic heights. 

No small feat to attain a clear understanding of these physical and chemical interactions within the atmosphere of earth and effectual outcome of them.

 

Back to the warming event forecasted Jan 21-25. 

IMG_3122.GIF

It appears borderline for a reversal at 10hPa, too early to make 100% claim just yet. GFS going for multiple warming and SSW. 

Waiting for Berlin to come into time scale.

IMG_3121.PNG

IMG_3123.GIF

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Thanks for your valuable input @KyleHenry, many stand to learn a lot from the likes of you :good:

The point about the ozone I had often wondered about - as the sun affects the highest levels of the atmosphere first albeit having had to travel through a lot of it first. Greater ozone concentrations, more interaction with UV, more energy expressed as warming.

The rest, for the most part, remains to be read into on my part. If I could just find the time in my hectic life :D

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6 minutes ago, Singularity said:

Thanks for your valuable input @KyleHenry, many stand to learn a lot from the likes of you :good:

The point about the ozone I had often wondered about - as the sun affects the highest levels of the atmosphere first albeit having had to travel through a lot of it first. Greater ozone concentrations, more interaction with UV, more energy expressed as warming.

The rest, for the most part, remains to be read into on my part. If I could just find the time in my hectic life :D

It's the polar night, limited interaction with UV.

Edited by Interitus
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Just now, Interitus said:

It's the polar night, no interaction with UV.

What I'm thinking is - the sun might peek over the horizon relative to the top of the stratosphere because it's so high up? Is that feasible? After all the earth is only tilted so much. I've had no time to check the validity of this, mind.

If not... I'm unsure how else ozone would affect things unless it has more kinetic energy inherent within it? :)

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4 hours ago, Singularity said:

What I'm thinking is - the sun might peek over the horizon relative to the top of the stratosphere because it's so high up? Is that feasible? After all the earth is only tilted so much. I've had no time to check the validity of this, mind.

If not... I'm unsure how else ozone would affect things unless it has more kinetic energy inherent within it? :)

Yes, there may be limited UV later in the late winter. Ozone is not generally considered a factor in SSW, it is the effects of the winter vortex on ozone which is important - being destroyed in cold vortex conditions and replenished by SSW.

Edited by Interitus
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2 hours ago, Interitus said:

Yes, there may be limited UV later in the winter. Ozone is not generally considered a factor in SSW, it is the effects of the winter vortex on ozone which is important - being destroyed in cold vortex conditions and replenished by SSW.

Agreed. An interesting study of ozone and the 1 hPa level http://onlinelibrary.wiley.com/doi/10.1002/2013JD020576/full

In which they declare processes at the 1hPa level are more predictable when studying O3 in Northern Hemisphere summers. 

States processes at the 1hPa level are set in motion up to a decade ago based on O3 levels at that time from summer data. 

 

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The latter stages of the ec 12z strat  look pretty odd co pared to the previous run. Generally run to run difference at 10 hpa aren't too big. 

berlin may look a bit different in the morning 

Edited by bluearmy

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On 1/12/2017 at 12:54, KyleHenry said:

The 1hPa level I find has more factors of influence.IMG_3124.JPG

First you've got the increase in wave altitude that progresses during January. 

Added to that we have to look above and towards the solar output. 

Lower 10.7 radio flux creates shrinkage of the thermosphere and the mesosphere as Earth enters solar minimum. 

Effects of energetic particles from the steady increase of protons released from coronal holes on sun's surface.IMG_3119.JPG

Them the chemical reactions at that altitude with Ozone and CO2 and in some years with cooling effect of SO2 with volcanic eruptions. 

Then return to Rossby wave breaking which increases O3 in the Northern hemisphere.

Kenetic energy contained within the Rossby waves at the particle level.

IMG_3120.GIF

Then differations in geo barclinic heights. 

No small feat to attain a clear understanding of these physical and chemical interactions within the atmosphere of earth and effectual outcome of them.

 

Back to the warming event forecasted Jan 21-25. 

IMG_3122.GIF

It appears borderline for a reversal at 10hPa, too early to make 100% claim just yet. GFS going for multiple warming and SSW. 

Waiting for Berlin to come into time scale.

IMG_3121.PNG

IMG_3123.GIF

@KyleHenry; Certainly, if these Stratospheric developments come off as-per the predictions above there is certainly potential for some very cold Maritime Arctic outbreaks over the UK going into February. If a big blocking-high results over Greenland that is certainly possible (maybe even something like what happened in February 1955), but if it positions further south and west (i.e over Canada) its more likely that deep depressions will pass to the NW of Britain instead in which case it will be milder with just short north-westerly snaps (as during the second half of this week).

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      Stratosphere
    • By Paul
      Please only post about the model output in this thread - if you're unsure what this entails, and what thread you should be using, please see our posting guide:
      https://www.netweather.tv/forum/topic/89198-model-threads-posting-guide/.
      We don't want to do it, but we have and will either block from posting, or pre-moderate the posts of those who continually post off topic posts in here. So please don't let that be you, with what may be a very interesting/exciting spell of weather on the way.  
      If you spot a post which you believe may be off topic or breaking the forum guidelines in any way, please hit the report button, and don't respond in the thread. The team will deal with reports as quickly as they can.
      Want to view the model outputs?
      You can get all the major ones here on Netweather:
      GFS
      GEFS Ensembles
      ECMWF
      ECMWF EPS
      NetWx-SR
      NetWx-MR
      Met-Office
      Fax
      GEM
      GFS Hourly
      Snow forecast and precip type
      Model Comparison
      Global Jet Stream
      Stratosphere
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