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Short range model discussion - into 2018

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The four main models currently all show a deep depression south of Greenland, moving closer to our west coast by +72h.  What happens to this depression and where it goes next is the question which remains to be answered as it could bring very different conditions depending on the evolution...

UKMO   image.thumb.gif.368a51caf72c12759b549e1bfb7127b2.gif

ECM     image.thumb.gif.4ba3b1a214402156577540baee6c7161.gif

GFS     image.thumb.png.f6ee7e27d1e366f7c688cccc9f0bc313.png

GEM.   image.thumb.png.fc8c09aed0e6c6ab885669fe46322bb6.png

This will bring the first stormy conditions of 2018 to some parts of the U.K.

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The jet is tracking just a little further north at times over the next few days on the back of the recent Azores high easing closer to our south.Often wavering across the UK marking the boundary between the polar and sub-tropical air.This meaning a very unsettled spell with wave depressions running across with wind and rain for much of country at times.

viewimage.pbx?type=gfs;date=20171230;tim

12z GFS showing the next 2 lows heading across Scotland puting areas further south in milder air for a while as the rain bands move through.

Sun 6pm                                                                 Tues 12noon

 viewimage.pbx?type=gfs;date=20171230;tim             viewimage.pbx?type=gfs;date=20171230;tim

The colder air still prevalent further north over much of Scotland with frequent snowfall over the highlands.Big temperature range at times with near freezing readings over parts of Scotland with double figures in the far south west.

The NH overall 500hPa pattern for tomorrow

viewimage.pbx?type=gfs;date=20171230;tim

 

showing low pressure to the north and high pressure across the south with a westerly type of setup-often referred to as +ve NAO pattern indicating the mean pressure differences between the Azores and Iceland.

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One has only to look at the Met O Fax charts to see how disturbed the Atlantic is predicted to be over the next 72 hours or so

http://www.weathercharts.org/ukmomslp.htm#t48

I like using this link as it gives the times when the charts are issued. There are times each day when there is a 'selection' of charts for the same time but all 3 issued at differing times. It does give some indication, for even further ahead at times, of how the latest thinking is in Exeter.

The link below gives a good idea of what weather systems are around.

http://meteocentre.com/analysis/map-surface.php?date=0&lang=en&area=eur&size=standard

One can have Europe or just the UK and a standard size or large size. The plots are the standard weather plots used throughout the world. During deepening and tracking lows one number in red to the right of the station circle will give you how much the pressure has fallen in the past 3 hours.

For instance in the link below, the observation from SW Eire shows a -74 in red, showing a pressure fall of 7.4 mb in 3 hours. So quite a decent fall that, it may simply be a front approaching or it may indicate that the 'low'is deepening.

oops sorry forgot to put it in, doing so now 2250!

http://meteocentre.com/analysis/map-surface.php?map=UK&date=2017123020&size=large&lang=en&area=uk

Edited by johnholmes
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A very windy few days (Sun to Weds) coming up as this sequence of maximum wind gusts forecasts from Arpege highlights. Hardly an area of the UK escaping from seeing a gust of 50 mph+ at some stage, although for a change the far north of Scotland might turn out to be the least windy place to be!

Wednesday is looking a particularly windy day nationwide.

 tempresult_mcv2.gif   

 

 

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The link below allows you to see how the deep low moved overnight

http://meteocentre.com/analysis/map-surface.php?map=UK&date=2017123109&size=standard&lang=en&area=uk

and the  Met O Fax charts latest outputs. Have a look beyond 120 hours at the bottom, showing the upper air predicted pattern post 120h. Quite a marked trough with not much sign of any upper ridging to the N or NE of the UK that is the talk of the other model thread?

instead it suggests a small upper ridge in the Iceland area.

http://www.weathercharts.org/ukmomslp.htm

Edited by johnholmes
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This output is, as far as I can recall, never quoted in here, UK Met Fax charts, not the usual outputs that do get comments but their furthest outputs.

http://www.weathercharts.org/ukmomslp.htm#UKmet-prognosis-00z

click on T+144 and scroll down for their latest outputs for 500 mb and the surface, currently the 00z goes out to Saturday 6 January 00 z

brain storm=this should be in the other model thread but I'll leave it here as well

Edited by johnholmes
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2 hours ago, johnholmes said:

Can you slow that down please BW?

Is this better John? The post above was 4 hourly intervals at 5 frames/second and, below, the same intervals but at 1 frame/second.

  tempresult_xzn0.gif

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Yes thanks very much for doing that, pretty windy for some looking at those frames.

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According to the 6 gfs by midnight tonight we have some very transients ridging over the UK whilst away to the west there is a wave forming on the front that has sneaked up from the eastern seaboard to be south of the main depression.

gfs_ptype_slp_eur3_4.thumb.png.7e34919018e58bfeb2dbccafa563a430.png

The wave then tracks quickly north east deepening rapidly on a very strong low level thermal gradient delineating the boundary between the cold and warm air to cross N. Ireland and the border country tomorrow evening. This will bring rain to many areas, particularly the further north with snow on the higher ground in Scotland. It will also get quite windy ending with the UK in a strong north westerly and frequent showers along western coasts.

gfs_ptype_slp_eur3_7.thumb.png.97a7ad66a3b2035d9ec8b124e67df8a5.pnggfs_ptype_slp_eur3_8.thumb.png.2563ddd4224d670bdf680c31daefa6a4.pnggfs_uv500_natl_7.thumb.png.eecc35b8e93991324a3228e5258324f5.png

As the low continues to track east the UK is once more at the mercy of the two pronged attack, one from the NW and the other from the SW as illustrated by the surface chart at 00 on Thursday which is also showing another low from the south east beginning to deepen behind the cold front to the west. This will deepen and swing across southern England on Friday whilst at the same time the Bermuda high pressure starts to amplify in response to the developing east coast storm I think it worth noting the 500mb chart at 00 Thursday which clearly shows the airmass distribution.

gfs_ptype_slp_eur3_12.thumb.png.8d9a83aa415177b98088278121d609b9.pnggfs_z500_natl_12.thumb.png.e0bb85875dd014d315e134a0af3ec17d.png

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further to the above a yellow warning from the METO

Quote

Between 18:00 Tue 2nd and 08:00 Wed 3rd

A spell of strong winds is expected later Tuesday, overnight into Wednesday morning. Combined with a period of high tides, it is likely that some western coastal communities will be affected by large waves and spray, and there is a small chance that injuries and danger to life could occur from large waves and beach material being thrown on to sea fronts, roads and coastal properties. Power cuts and disruption to other services (mobile phones for example) may occur, and there is a small chance of transport disruption or cancellation of public transport.

https://www.metoffice.gov.uk/public/weather/warnings#?date=2018-01-02

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Looking at the Fax outputs and the low is predicted to deepen by about 18 mb between the T+36 (12z Tuesday) and 00z Wednesday shown at 97 mb on the T+48 currently on view.

As before the path of this low can be viewed, when it starts to deepen, on this link

http://meteocentre.com/analysis/map-surface.php?date=0&lang=en&area=eur&size=standard

 

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Posted (edited)

Latest GFS run shows a wet and windy few days coming,these are charts for Weds.

viewimage.pbx?type=gfs;date=20180101;timviewimage.pbx?type=gfs;date=20180101;tim

The jet at times approaching 200mph wavering across the UK separating the cold air lurking just to the north from the sub-tropical air to the south.It A breeding ground for further wave depressions running across from the Atlantic.

A look at Thursday 1200hrs  at the expected surface temperatures as some deeper cold starts head into N.Scotland on a northerly wind.

viewimage.pbx?type=gfs;date=20180101;timviewimage.pbx?type=gfs;date=20180101;tim

The effect of this is to enhance the large temperature differences north to south at this time..

Edited by phil nw.
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Before we discover whether a weekend easterly will bring snow or rain to the UK we still have this nasty little depression to deal with, illustrated well by the Arpege

image.thumb.png.d036b2caa824122cae210e412458d131.png   image.thumb.png.5b26a704b306fa297bad2c1da9996690.png

Looks like tomorrow night will bring strong winds to many western and northern coasts and it will be very gusty even inland, accompanied by some prolonged rain, which could cause some travel disruption.  Not sure what the requirements are for a storm to be named but I don't think this has been given one yet?

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1 minute ago, Sky Full said:

Before we discover whether a weekend easterly will bring snow or rain to the UK we still have this nasty little depression to deal with, illustrated well by the Arpege

image.thumb.png.d036b2caa824122cae210e412458d131.png   image.thumb.png.5b26a704b306fa297bad2c1da9996690.png

Looks like tomorrow night will bring strong winds to many western and northern coasts and it will be very gusty even inland, accompanied by some prolonged rain, which could cause some travel disruption.  Not sure what the requirements are for a storm to be named but I don't think this has been given one yet?

 Yes, it has been named Eleanor and there is a thread for it now :-) 

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No need to go into the detail of Eleanor here but just to note the position at midnight tonight.

PPVE89.thumb.gif.4b4c950aca6f3b8464063711d68d396e.gif

Eleanor tracks east across the North Sea tomorrow leaving the UK in a strong north westerly wind, particularly in the north, with frequent squally showers, probably of snow in Scotland.

gfs_ptype_slp_eur3_6.thumb.png.9a64d1d3c21dd4a3e94c1cf421181caf.pnggfs_ptype_slp_eur3_7.thumb.png.71c6e30a25402950e5c3e3ce68756737.png

As can be seen from the last chart the UK is at the sharp end of two energy flows, one from the NW and the other from the SW.  This is very well illustrated by the chart at Thursday 00 which has a frontal wave south west Ireland with the front already impacting Cornwall, with another developing low behind  and another low approaching from the north west. It also shows the strong jet which delineates the boundary between the cold and warm air and facilitates the movement of the developing low behind the frontal wave

gfs_ptype_slp_eur3_9.thumb.png.1ed4d7fc87669277e538b832ce09e83f.pnggfs_uv500_natl_9.thumb.png.749ce63615d1cf33cd05bb8700f4811b.png

Thus by Friday 00 the low is 978mb south west Ireland with the associated front perhaps bringing some snow along the leading edge on higher ground in the north but at this stage the main interest lies to the west over North America where the east coast storm is impacting the jet as the Bermuda high pressure surges. This will have a knock on affect downstream and the evolution over the UK during the weekend and beyond.

gfs_ptype_slp_eur3_13.thumb.png.9c7a967e0a50fe6ea781922fbc1a73f7.pnggfs_ptype_slp_east3_13.thumb.png.732665bb7484b426c8145ab60fa344b8.pnggfs_uv250_natl_13.thumb.png.d62d3dbdad121da09068dde2233381be.png

 

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Quite wet over the next three days (apart from being very windy at times) in the W but particularly the NW

gfs_tprecip_uk2_14.thumb.png.2fe4deb17b9a74fa93647edf1fe9b344.png

 

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Morning all :)


90-515UK.GIF?02-0

From my IMBY-ist perspective, slightly more concerned by the track and intensity of Friday's feature - not as vigorous as Eleanor it would seem but likely to bring a period of heavy rain and strong winds during daylight hours on Friday so another "event" to consider.

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The updated fax for tomorrow has the stray occlusion that may be the squally feature mentioned by the METO

PPVE89.thumb.gif.1eb241da307c933b9092367ee597e2bb.gif

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The Met track, using their 06 z for today and predicted for tomorrow suggests:-

a bit below 1000 mb around 48N 28W to track just north of the Isle of Man then track just N of E clearing the east coast somewhere close to Newcastle with a central pressure around 976 mb.

http://www.weathercharts.org/ukmomslp.htm#t24

again to track it use this link

http://meteocentre.com/analysis/map-surface.php?date=0&lang=en&area=eur&size=standard

This link is not perfect for correct positioning and depth of systems but gives a fair idea, and you can toggle both the size and time of chart.

Interesting for sure and possibly severe gales for some, much as indicated by UK Met warnings. Why spend time in the coldie section when there is such interesting weather in the shorter term

After this low has passed we can also then turn to 'what cold spell, when, if etc. The next 72h after the storm takes us currently out to T+144h, right in the midst of the possible cold set up. If you want to cheat a bit and look that far ahead, take a look at the first link above for UK Met ideas on what may happen!

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2 hours ago, stodge said:

Morning all :)


90-515UK.GIF?02-0

From my IMBY-ist perspective, slightly more concerned by the track and intensity of Friday's feature - not as vigorous as Eleanor it would seem but likely to bring a period of heavy rain and strong winds during daylight hours on Friday so another "event" to consider.

Yes another on its way, again at T+84 (bit outside this thread?) UK Met show their position and I would suspect following its track from its position on the previous Fax chart, (we are assuming of course that depth and positions are correct-a big ask really), would take it out of the southern half of East Anglia, much as the chart you show. Just how strong any winds will be is obviously too far out to give values, windy will cover it for now.

Really interesting weather being predicted and maybe even a cold spell after all this?

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      If the deflection of the Rossby Wave then a wave breaking event occurs – similar to a wave breaking on a beach – except this time the break is of atmospheric air masses. Rossby wave breaks that are directed poleward can have a greater influence on the stratosphere. The Rossby wave breaks in the troposphere can be demonstrated by this diagram below –
      RWB diagram:

      https://www.jstage.jst.go.jp/article/jmsj/86/5/86_5_613/_pdf
       This occurs a number of times during a typical winter and is more pronounced in the Northern Hemisphere due to the greater land mass area. Most wave deflections into the stratosphere do change the stratospheric vortex flow pattern - this will be greater if the stratosphere is more receptive to these wave breaks (and if they are substantial enough, then a SSW can occur). The change in the stratospheric flow pattern can then start to feedback into the troposphere - changing the zonal flow pattern into something with more undulations and perhaps ultimately to a very meridional flow pattern especially if a SSW occurs - but not always. If the wave breaking occurs in one place then we see a wave 1 type displacement of the stratospheric vortex, and if the wave breaking occurs in two places at once then we will see a wave 2 type disturbance of the vortex which could ultimately squeeze the vortex on half and split it – and if these are strong enough then we would see a displacement SSW and split SSW respectively. The SSW is defined by a reversal of mean zonal mean winds from westerly to easterly at 60ºN and 10hPa. This definition is under review as there have been suggestions that other warmings of the stratosphere that cause severe disruption to the vortex could and should be included. http://birner.atmos.colostate.edu/papers/Butleretal_BAMS2014_submit.pdf
      A demonstration of the late January 2009 SSW that was witnessed in the first strat thread has been brilliantly formulated by Andrej (recretos) and can be seen below:
       
      The effects of a SSW can be transmitted into the troposphere as the downward propagation of the SSW occurs and this can have a number of consequences. There is a higher incidence of northern blocking after SSW’s but we are all aware that not every SSW leads to northern blocking. Any northern blocking can lead to cold air from the tropospheric Arctic flooding south and colder conditions to latitudes further south can ensue. There is often thought to be a time lag between a SSW and northern blocking from any downward propagation of negative mean zonal winds from the stratosphere. This has been quoted as up to 6 weeks though it can be a lot quicker if the polar vortex is ripped in two following a split SSW. A recent paper has shown how the modelling of SSW and strong vortex conditions have been modelled over a 4 week period. This has shown that there is an increase in accuracy following weak or strong vortex events – though the one area that the ECM overestimates blocking events following an SSW at week 4 is over Northwestern Eurasia.
      http://iopscience.iop.org/article/10.1088/1748-9326/10/10/104007
      One noticeable aspect of the recent previous winters is how the stratosphere has been susceptible to wave breaking from the troposphere through the lower reaches of the polar stratosphere - not over the top as seen in the SSWs. This has led to periods of sustained tropospheric high latitude blocking and repeated lower disruption of the stratospheric polar vortex. This has coincided with a warmer stratosphere where the mean zonal winds have been reduced and has led to some of the most potent winter spells witnessed in recent years.
      We have also seen in recent years following Cohen's work the importance of the rate of Eurasian snow gain and coverage during October at latitudes below 60ºN. If this is above average then there is enhanced feedback from the troposphere into the stratosphere through the Rossby wave breaking pattern described above and diagrammatically below.
      Six stage Cohen Process:

      The effect of warming of the Arctic ocean leading to colder continents with anomalous wave activity penetrating the stratosphere has also been postulated
      http://www.tos.org/oceanography/archive/26-4_cohen.pdf
      As ever, I will supply links to various stratospheric websites were forecasts and data can be retrieved and hope for another fascinating year of monitoring the stratosphere.
      GFS: http://www.cpc.ncep.noaa.gov/products/stratosphere/strat_a_f/
      ECM/Berlin Site: http://www.geo.fu-berlin.de/en/met/ag/strat/produkte/winterdiagnostics/index.html  
      Netweather: https://www.netweather.tv/charts-and-data/stratosphere
      Instant weather maps: http://www.instantweathermaps.com/GFS-php/strat.php
       NASA Merra site: http://acdb-ext.gsfc.nasa.gov/Data_services/met/ann_data.html
      Previous stratosphere monitoring threads:
      2016/17 https://www.netweather.tv/forum/topic/86485-stratosphere-temperature-watch-201617/
      2015/16 https://www.netweather.tv/forum/topic/84231-stratosphere-temperature-watch-20152016/
      2014/2015 https://forum.netweather.tv/topic/81567-stratosphere-temperature-watch-20142015/
      2013/2014 https://forum.netweather.tv/topic/78161-stratosphere-temperature-watch-20132014/
      2012/2013 https://forum.netweather.tv/topic/74587-stratosphere-temperature-watch-20122013/
      2011/2012 https://forum.netweather.tv/topic/71340-stratosphere-temperature-watch-20112012/
      2010/2012 https://forum.netweather.tv/topic/64621-stratosphere-temperature-watch/?hl=%20stratosphere%20%20temperature%20%20watch
      2009/2010 https://forum.netweather.tv/topic/57364-stratosphere-temperature-watch/
      2008/2009 https://forum.netweather.tv/topic/50299-stratosphere-temperature-watch/
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