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Short range model discussion - into 2018

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10 minutes ago, knocker said:

Not really Chris as the upper trough is becoming very negatively tilted and the very strong 500mb flow inclines from running North of east to south and this dictates the track of the developing low as it swings around the high pressure to the east.

Thanks - this thread and your posts are fantastic for improving my understanding and knowledge.

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The ecm has the very active front and a belt of heavy rain impacting the north west of Scotland by 1800z on Sunday with a strengthening south westerly wind.

Over the next 24hours it swings south east clearing Kent by 1800 on Monday with the heaviest rain in the north Snow would appear unlikely apart from maybe the much higher ground in Scotland with dew points way too high

But the legacy will be a very strong north westerly wind covering the country, perhaps gale force, and frequent wintry showers that could well be a mix of just about anything., mainly along western coasts but particularly in N. Ireland and Scotland.

ecm_mslp_uv850_natl_3.thumb.png.69ab53c7f1a9e5bb080a646ca8c31388.pngecm_mslp_uv850_natl_4.thumb.png.e33bf10fd01a2a209a85a92e1aec7c0e.pngecm_mslp_uv850_natl_5.thumb.png.427a19785e7bb17cebd48004afe64b0e.png

Edited by knocker
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yes not long before this thread will be in the middle of whatever ppn is predicted for the start of the next cold spell. It certainly has the look of being fairly potent at times, winds between West and NW, maybe even further round at times. So watch the Fax charts, and of course join the roller coaster ride for will it snow in my back yard. Hopefully this thread will avoid the yah boo comments that take up so much of the teams' time trying to weed out.

This winter is certainly, already, a very different winter to the last few. 11 air frost here since 1 December and 6 days with snow falling with 1 covering more than 60% of the ground at 9am.

Last year 3 days snow falling 1 lying with 14 air frosts 1 December-28 February

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As John has mentioned we have now arrived at the transition to a much more volatile period of weather with the likelihood of a bit of everything. And this weekend is the start of the transition. With this in mind there are two or three aspects worth noting.

Firstly, a glance at the 500mb field for Sunday 00 and Tuesday 00 indicates that the segment of the vortex, now the intense upper trough to the north west, is poised to duck south east over the UK, along with the much colder Pm airmass.

gfs_z500_natl_5.thumb.png.e19e7b6b218ddf35596387e99fde83de.pnggfs_z500_natl_13.thumb.png.ab781db86bbd138a8c8de4e62332b18d.pnggfs_t850a_natl_13.thumb.png.c4d90e7100c2cc0b090e5a57df6db2c6.png

The other aspects involve the detail over the weekend. First the shallow low and front(s) just to the west are going to lose their identity and stall over the western regions over today with the rain eventually petering out but not until maybe 20mm or so has fallen in places.(currently moderate rain here)

PPVA89.thumb.gif.b96a7d6524c9d4f2dad4b6d428b62b94.gifPPVE89.thumb.gif.c96472011bef8a5294ff7b14388ad582.gifoverview_015.jpg?2018011300

Secondly, and more importantly regarding future events, by Sunday 12 the deep surface low associated with the aforementioned upper trough is now in the Iceland area with it's associated fronts just impacting the north west of Scotland  They continue to track south east during the day and overnight before clearing the south east by 12 on Monday. Thus over the24 most places will receive a fair amount of rain, perhaps some snow on the mountains.

PPVI89.thumb.gif.77f2b6fcd19e6d58ffd557150b4dca8f.gifoverview_036.jpg?2018011300overview_060.jpg?2018011300

But the unfolding scenario behind the passage of the front(s) becomes centre stage now, A very cold and strong WNW wind is now in place, perhaps gale force along western coasts, with frequent squally wintry showers which could include thunder hail, snow and even rain. Predominately these will affect western and northern areas but also could spread a fair way inland. Also, as can be seen, the alignment of the jet is slowly changing to a more ESE direction as the upper trough tracks south east as indicated earlier.

gfs_ptype_slp_eur3_13.thumb.png.49182ca26ce3128456a27ddcf3ea0c70.pngoverview_072.jpg?2018011300gfs_uv500_natl_16.thumb.png.ca4b99dd1698d7f449c012e4e9f756d3.png

The alignment of the jet, courtesy of the positioning of the high pressure to the south west and the aforementioned trough is important because it dictates the direction of travel of the low that has formed of the eastern seaboard and is winging around the high pressure towards the UK. A track which this morning's gfs has adjusted a tad north

gfs_mslp_wind_atl_13.thumb.png.f5761caa39bd29b45a3e931261b6ad0e.pnggfs_mslp_wind_atl_17.thumb.png.04b36ddc9a74faae4ac868e1e8a342ed.png

 

Edited by knocker
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The other area is actually talking, well hyperventilating, about the weather almost within this time scale, well some are.

 

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The low for Wed Night/ Thursday morning now looks like bringing serious blizzards to Scotland. Temporarily milder in southern parts (A milder blip).  But that low will also aid in pulling deeper cold air south thereafter. Potential for a lot of snow over lots of the British Isles in the next week or so !

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A yellow warning for rain issued by the METO for Cornwall as the front continues to stall. The HR Modis midday sat image courtesy Dundee Satellite Station.

ch38.thumb.jpg.f9805937897c494373e4e6921c1358bb.jpg

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Following on from this morning's post, and to add a recent METO warning, once the front clears the south east on Monday the UK will be in a strong unstable WNW gale force wind,  perhaps severe, on western coasts and the north, with very frequent wintry showers of now, hail, thunder and rain. These will be more frequent in N. Ireland and Scotland leading to lying snow in many places. Feeling very cold. (snow depths not to be taken too literally)

overview_072.jpg?2018011312snowdepth_072.jpg?2018011312

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the latest fax for 12 Tuesday showing the strong WNW surface wind, the odd trough in the flow, and the 'low' over Newfoundland

PPVK89.thumb.gif.3c45e417153091766b0a80d2f732dc44.gif

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Euro4 also now has the effects of the trough within range as well, now.

18011518_1318.gif

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Yesterdays front which hung around western regions has finally dissipated, not before dumping 30mm of rain down here, leaving a mainly dry day with perhaps some sunshine in most areas. The exception being the far north west where front(s) associated with the deep upper trough over Iceland will impact the Hebrides by 12 and move south east bringing some heavy rain and strong winds to Scotland and N. Ireland.

gfs_z500a_natl_4.thumb.png.a779eb1fc487e25c95f5769c5940bca5.pngPPVE89.thumb.gif.080048874d9802756eb76815f31d0ebb.gifoverview_012.jpg?2018011400

The front(s) and rain will continue their journey south east overnight and though tomorrow thus bringing rain and increasing wind to most places before clearing the south east around 1800 tomorrow,. In their wake the surface wind will veer WNW introducing a much colder airmass which initially bring frequent wintry showers of snow, hail, thunder as well as rain to western and northern areas with snow starting to accrue in the north.

PPVI89.thumb.gif.a15024b28a07f092c8344732cdd96207.gifoverview_042.jpg?2018011400snowdepth_044.jpg?2018011400

This scenario continues through Tuesday with the wintry showers progressing further inland and the snow showers further south thus lying snow becoming more widespread.

PPVK89.thumb.gif.2cc9aa30296fb618fa647153e5b27888.gifoverview_066.jpg?2018011400snowdepth_066.jpg?2018011400

Overnight Tuesday into Wednesday some subtle changes take place as the upper trough to the north east and the high pressure to the south west slightly alter their alignment resulting in the surface wind  veering north west whilst at the same time the wave depression that originated off the eastern seaboard is tracking quickly east around the high and is at 30W by 1200 Wednesday. But there is no agreement on the position of the wave and , in particular the depth and track as can be seen by a quick glance at the fax and this morning's gfs.

gfs_z500a_natl_13.thumb.png.1e325ebcbaa8e286d21e4e05e5e52162.pngPPVM89.thumb.gif.33f558b5456d25ccc6789b4e9abafe2e.gifgfs_ptype_slp_eur3_15.thumb.png.0fb6cdf01d15c537f0923b0aab73ce14.png

Outside of the remit of this thread but the latest fax has the low 968mb northern Germany at 1200 Thursday but this is still along way from being a done deal.

PPVO89.thumb.gif.d15e1b6e49a80c0d1a720ad8fc34c7e6.gif

Edited by knocker
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Since going to press the fax for12 Wednesday has been revised so I would suggest the Thursday fax above be ignored as well.

PPVL89.thumb.gif.3203601146e8532dcf12166035a64edc.gif

Edited by knocker
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Oh for a couple of weather ships, particularly on stations Charlie and Juliett :whistling:

Atlantic_Weather_ships.jpg

Edited by knocker
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A quick follow up from the gfs  06 showing the rapid cyclogenesis as the low drops 25mb in 18 hours

gfs_uv700_natl_13.thumb.png.ed45d0c16d2187d3f38d51006d199b79.pnggfs_uv700_natl_16.thumb.png.275551828bbdc15772f1afd416618d55.png

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27 minutes ago, knocker said:

A quick follow up from the gfs  06 showing the rapid cyclogenesis as the low drops 25mb in 18 hours

gfs_uv700_natl_13.thumb.png.ed45d0c16d2187d3f38d51006d199b79.pnggfs_uv700_natl_16.thumb.png.275551828bbdc15772f1afd416618d55.png

Is that sufficient to qualify for explosive cyclogenesis status?

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55 minutes ago, chrisbell-nottheweatherman said:

Is that sufficient to qualify for explosive cyclogenesis status?

Easily as a drop of 24mb in 24 hours is normally taken as the criteria. Of course it hasn't occurred yet.

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Only just finding time to get on Net Wx for other than the briefest glimpse, wondered why the gloom on the other thread early this morning. Looking at the new Fax charts, quite big changes.

Must go and investigate the models.

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The front and rain on the way south east as seen at 1500 satellite and forecast progress by 00 and 12 tomorrow. with the colder showery airmass behind

ch4.thumb.jpg.c85f117a54b0a682b54373f2c3655e47.jpgoverview_012.jpg?2018011412overview_024.jpg?2018011412

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Tonight's ecm. At T72 (Weds 12) the Atlantic low is 984mb west of N. Ireland at around 35W where it is engaging an 120kt 500mb wind that is tracking north east along the western flank of a transient ridge.

Eighteen hours later, with the transient ridge pushed south , the low has tracked very rapidly ENE driven by the aforementioned jet, and at 0600 Thursday is over northern Scotland 958mb. This has the potential to bring very strong winds to N. Ireland, southern Scotland, and northern England gusting in the region of 70- 80 kts as it tracks into the North Sea over the next six hours.

ecm_mslp_uv850_natl_4.thumb.png.19aad5972b4e711d76434ac7fb3ac6c9.pngecm_mslp_uv850_eur_5.thumb.png.9da5e75ee251a13cfb1a8ff7c8332190.png

 

Edited by knocker
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Yes a very powerful feature. I'm going to make a guess that if it doesn't deepen as much it would track further south.

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What kind of rainfall levels can we expect with this storm and will the rain be worse to the NE quadrant or south  ?

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8 minutes ago, matty40s said:

What kind of rainfall levels can we expect with this storm and will the rain be worse to the NE quadrant or south  ?

Frankly I wouldn't like to hazard an opinion at this stage because there is still questions over the track and intensity of the low. Adjustments to both could make a big difference to areas potentially affected by rain, snow in the north, and of course the intensity of the wind. Regarding the latter I suspect the ecm is the worse case scenario (hopefully)

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55 minutes ago, knocker said:

Tonight's ecm. At T72 (Weds 12) the Atlantic low is 984mb west of N. Ireland at around 35W where it is engaging an 120kt 500mb wind that is tracking north east along the western flank of a transient ridge.

Eighteen hours later, with the transient ridge pushed south , the low has tracked very rapidly ENE driven by the aforementioned jet, and at 0600 Thursday is over northern Scotland 958mb. This has the potential to bring very strong winds to N. Ireland, southern Scotland, and northern England gusting in the region of 70- 80 kts as it tracks into the North Sea over the next six hours.

ecm_mslp_uv850_natl_4.thumb.png.19aad5972b4e711d76434ac7fb3ac6c9.pngecm_mslp_uv850_eur_5.thumb.png.9da5e75ee251a13cfb1a8ff7c8332190.png

 

Yes a very nasty storm potential here.

Metoffice/beeb very wary to pin point this storm as yet and what it may bring.

They have it tracking further south across scotland with snow risk to the north of low and as it engages colder air and also as it clears dragging colder air back in as it leaves.

Winds the main feature, very damaging gusts for ireland and more so northern england.

Expect warnings being issued tomorrow then an official named storm tuesday at the latest??

Edited by doctor32
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According to the latest fax for 1200 Wednesday the MET is putting the central pressure 986mb.

PPVK89.thumb.gif.3764c212c6710d5d8f2dcc6351856c9d.gif

 

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