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Model Output Discussion 01/09/17


phil nw.

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Posted
  • Location: Camborne
  • Location: Camborne

To some ext the GEFS 10-15 anomalies this evening has broken ranks and has altered the orientation of the HP/trough axis so that the latter is significantly negatively tilted SE over the UK. This would stop any northward drift of the Atlantic depressions and put them on more easterly track as the block eases. Of course merely to be noted at the moment so see if NOAA and EPS nod in this direction.

gefs_z500a_5d_nh_61.thumb.png.89cb80e0d799c54f52c1c6e5f4316064.png

Edited by knocker
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Posted
  • Location: Camborne
  • Location: Camborne

NOAA and the EPS (can't post) are not adverse to the above. A pattern change over the US has a trough down the east which incorporates a decaying Maria and the medium strength jet leaving the seaboard is north of west running to the UK, albeit weakening in the east where the configuration of the HP is still effective in slowing eastward movement. But this could indicate more unsettled weather in the south as systems track further south. Along way off and really just musing at the moment.

814day_03.thumb.gif.830055409715a0681171088fa9f3b9dc.gif

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Posted
  • Location: Camborne
  • Location: Camborne

To add a little to last night and to confuse matters even further the gfs this morning does not merge Maria with the east North American trough but runs it NE into the Atlantic. This obviously impacts the pressure distribution in the western Atlantic and impacts the jet and thus the downstream evolution. As of this morning it eventually forces a very strong jet south and opens the gates to the Atlantic but that's all a long way off and merely of academic interest at the moment.

gfs_uv250_natl_35.thumb.png.b5edcfba8eb30b34bde4cb80b6bdb23d.pnggfs_z500a_natl_41.thumb.png.7dd9e7f75c33dd00db52858fb4b489ae.pnggfs_uv250_natl_40.thumb.png.f5d44d63ac0fcc53372e646a13612ef2.png

Back to the here and now. The waving front currently bringing rain to Scotland which should clear is lying down the west of the UK and will slowly move east during the day bringing outbreaks of rain to all apart from the far south east that will remain dry and quite warm. This eventually clears overnight before the next system arrives with the fronts aligned down the Irish Sea by 12z Friday,

PPVE89.thumb.gif.908e40e53eca73610ed7a02fcb9d3b56.gifPPVI89.thumb.gif.ea1d96e07440e3a0209c2150534007ca.gifaccumprecip_d02_31.thumb.png.3fb4ca0339766b1247bd292e7a9ac27a.png

These weaken as they track east and soon clear the north leaving to UK within the influence of the HP to the east and a light S/SE drift and a pleasant weekend for most.The one fly in the ointment being the front of a large slow moving depression SW of Iceland attempting to track east but getting no further than the Irish Sea before dissipating. From the weekend until the middle of next week the weather remains quite benign over the UK which is in a very slack pressure gradient with the HP to the NE and troughs to the west and south east. So quite warm with light winds 

gfs_ptype_slp_eur3_11.thumb.png.ce8a2ae5e7680326375ebe4800b12049.pnggfs_ptype_slp_eur3_20.thumb.png.8db9b55a8db5d6318342ac559a9ecc44.pnggfs_ptype_slp_eur3_26.thumb.png.1e94c146f0cb38c91c222b7dd962c2a3.png

From here the low to the south west deepens and moves slowly north and the associated fronts track east, again slowly weakening as they go  But it's all rather messy and even though the high pressure has moved NE there is no great ingress by the Atlantic by the weekend and now is the time when Maria enters the frame so this best left here, In fact probably best left before this.

gfs_ptype_slp_eur3_32.thumb.png.332e4b6c4ea3354e4ac082d6d36670e1.pnggfs_ptype_slp_eur3_39.thumb.png.5bee259ab3974946ef6ebddc7124d65b.png

So all in all a pretty fair mixture the best of the weather being the weekend to midweek with as ever the usual NW/SE bias vis precipitation.

gfs_tprecip_uk2_37.thumb.png.3e674525bc306aabdee2a4808f3f1a67.png

 

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Posted
  • Location: Camborne
  • Location: Camborne

Just to clarify the front situation over the latter part of the weekend. The ecm would appear to make rather more of it as it slowly moves east Sunday evening/Monday morning accompanied by a band of rain and looking at the fax charts some doubt must still remain on how far east it will go and how active.

PPVM89.thumb.gif.fd5c566e4bbb4e646b44e52ea1e00ad4.gifPPVO89.thumb.gif.083604874fa5f3217e4a3dbd13074ca0.gif

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Posted
  • Location: Camborne
  • Location: Camborne

The ecm also has an unsettled end to next week and then has Maria caught up in the general trough mayhem NE N.America/N. Canada that leads to a deep low mid Atlantic at the end of the run, With the strong jet running east south of it place your bets on what happens next

ecm_t850_anom_natl_11.thumb.png.8e53a34b542d624fb9549edbc17d6659.png

 

Edited by knocker
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Posted
  • Location: Darlington
  • Weather Preferences: Warm dry summers
  • Location: Darlington
On 9/17/2017 at 17:47, I remember Atlantic 252 said:

but I have for last few runs been monitoring Thursday's washout for central parts, look unlucky on this, it will arrive in the day and not the night

 

On 9/18/2017 at 08:28, I remember Atlantic 252 said:

What about this though SS? looks vile, middle of the day as well

ukprec.png

So far it looks fairly standard moving in slowly from the west and weakening all the time

5756.thumb.png.6c79cd15a9abbea2bc90a56388b94aba.png54645667.thumb.png.7152b657777268570ab32308b994381e.png

 

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Posted
  • Location: Cambridge, UK
  • Weather Preferences: Summer > Spring > Winter > Autumn :-)
  • Location: Cambridge, UK

Models showing a gradual transition to something more unsettled as we head through next week - ties in with the MetO update too. Lots of energy piling into the jet too with all these hurricanes this year. I guess the outlook could easily change again if ex-Maria pushes the jet out of line once more. One to keep tabs on.

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Posted
  • Location: Lichfield
  • Location: Lichfield
2 hours ago, Summer Sun said:

 

So far it looks fairly standard moving in slowly from the west and weakening all the time

5756.thumb.png.6c79cd15a9abbea2bc90a56388b94aba.png54645667.thumb.png.7152b657777268570ab32308b994381e.png

 

Yeah, no disrespect at all mark, but i could never see this as anymore than a bit of a damp squib, not sure what the concern was about really?

In general a pretty depressing picture being painted by the models as of late.

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Posted
  • Location: Nr. Tunbridge Wells (150m/450ft asl)
  • Location: Nr. Tunbridge Wells (150m/450ft asl)

Can anyone explain why rel. humidity forecasts are higher for Sunday (and beyond) than they are for Friday and Saturday. The models show a change from a S/SW flow to a SE/E, continental flow during that period. It seems to me that that should bring drier air to the UK. What am I missing?

Friday:
GFSOPEU06_24_1.png

Sunday:
GFSOPEU06_72_1.png

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Posted
  • Location: Crewe, Cheshire
  • Weather Preferences: Snow, storms and other extremes
  • Location: Crewe, Cheshire
13 minutes ago, wellington boot said:

Can anyone explain why rel. humidity forecasts are higher for Sunday (and beyond) than they are for Friday and Saturday. The models show a change from a S/SW flow to a SE/E, continental flow during that period. It seems to me that that should bring drier air to the UK. What am I missing?

Friday:
GFSOPEU06_24_1.png

Sunday:
GFSOPEU06_72_1.png

To put it simply I think it's all down to airmass. Warmer sourced air on Sunday which has more potential to hold water vapour- this together with trough not too far to the west would account for what you're seeing in the output. The flow would have to back slightly more continental to have a drying effect on the airmass. 

I would also think the shallow troughing over mainland Europe would have some effect. 

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Posted
  • Location: Nr. Tunbridge Wells (150m/450ft asl)
  • Location: Nr. Tunbridge Wells (150m/450ft asl)
4 minutes ago, CreweCold said:

To put it simply I think it's all down to airmass. Warmer sourced air on Sunday which has more potential to hold water vapour- this together with trough not too far to the west would account for what you're seeing in the output. The flow would have to back slightly more continental to have a drying effect on the airmass. 

I would also think the shallow troughing over mainland Europe would have some effect. 

Hm... But that sounds like you agree with me. Warmer sourced air on Sunday (actually only looks a tad warmer, but nonetheless...) means more potential to hold water vapour, which should mean lower relative humidity, assuming the same or lower absolute humidity. And again, surely total humidity would be expected to be lower given incoming air tracking over continental Europe rather than the Atlantic Ocean.

All I can think of is that it's something to do with flow further up in the atmosphere being more southerly in the next two days, as per the 850 flow charts, and that that filters down and means drier air at the surface too. Still leaves me a bit confused as to why that continental flow from Sunday onwards is so humid.

 

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Posted
  • Location: Evesham/ Tewkesbury
  • Weather Preferences: Enjoy the weather, you can't take it with you 😎
  • Location: Evesham/ Tewkesbury

Evening ,looks like the progged east west battle is going to give the UK with perhaps flooding issues in one or two places especially out west but not exclusively in the next ten days and add the potential for some stormy conditions after a quiet start to next week into October with the added ingredients of ex tropical influence:hi:

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Posted
  • Location: Camborne
  • Location: Camborne

The ecm this evening would appear to have made a move to push the boundary of the block further east and by the end of the run Maria is engaing the strong jet in mid Atlantic.

Prior to this the models are still struggling with weak front which by 12z Sunday is lying down the west of the country. It appears to get a wave on it as it moves fractionally east in the next 24 hours which may give a fair bit of rain in the north west and Scotland. That eventually dissipates but by 12z Wednesday the next fronts have arrived in the west again bringing a fair bit of rain to the north and Scotland as they clear north east.

But this is short-lived as another low is forming in the circulation of the main low to the west and this quickly deepens and swings in on Thursday and could bring some substantial amounts of rain with it (again concentrated in the north and west) accompanied by gale force winds.

The low and fronts clear by Friday leaving the UK in a showery westerly. But not for long as the next low and fronts sweep in late Saturday heralding a very wet and windy night and Sunday  And Marie is waiting in the wings. We could be looking at 5-6in of rain in some western and northern areas over the ten days.

ecm_mslp_uv850_natl_7.thumb.png.8b12a984f7c98b59bc5c8c9f79c9fe30.pngecm_mslp_uv850_natl_8.thumb.png.dd1e33491e54dd9303301e493c45c5fa.pngecm_mslp_uv850_natl_11.thumb.png.7c52c87beba189f4442abde466829e65.png

Edited by knocker
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Posted
  • Location: Manchester Deansgate.
  • Weather Preferences: Heavy disruptive snowfall.
  • Location: Manchester Deansgate.

The models beginning to get a whiff of the weak nina + -QBO + low solar activity + active atlantic hurricane season combination.

 

cfsnh-3-10-2017_yxf2.pngcfsnh-3-11-2017_ndh3.pngcfsnh-3-12-2017_hcx4.png

 

EDIT : god knows why they have come out so big.

Edited by feb1991blizzard
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Posted
  • Location: Cambridge, UK
  • Weather Preferences: Summer > Spring > Winter > Autumn :-)
  • Location: Cambridge, UK

ECM....from quiet to insanity in 3 days!

ECM1-144.GIF?22-12ECM1-216.GIF?22-12

No correlation at all to the GFS at the same time:

gfs-0-192.png

Or the GEM, which goes full on high pressure:

gem-0-192.png?00

In a nutshell - the models don't have a clue!

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Posted
  • Location: Camborne
  • Location: Camborne

Never a dull moment these days. Naturally the ecm differs from the gfs at the end of next week although the end result of wet and very windly weather is similar

At T168 Maria is moving steadily north along the eastern seaboard  but systems are breaking off and travelling east on the jet to form intense lows over the UK and to the south. So that by the end of the run there is a large area of low pressure to the SW/S with the high pressure to the north thus the UK in quite a strong easterly airstream. :shok:

ecm_mslp_uv850_natl_8.thumb.png.09240390f4b2580982227d9744d55661.pngecm_mslp_uv850_natl_9.thumb.png.c7fc17907be925fab7d42faae0eb11d8.pngecm_mslp_uv850_natl_10.thumb.png.195b83e297722a2f2dee646368029d19.png

Edited by knocker
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Posted
  • Location: Brighton (currently)
  • Location: Brighton (currently)
1 hour ago, knocker said:

Never a dull moment these days. Naturally the ecm differs from the gfs at the end of next week although the end result of wet and very windly weather is similar

At T168 Maria is moving steadily north along the eastern seaboard  but systems are breaking off and travelling east on the jet to form intense lows over the UK and to the south. So that by the end of the run there is a large area of low pressure to the SW/S with the high pressure to the north thus the UK in quite a strong easterly airstream. :shok:

ecm_mslp_uv850_natl_8.thumb.png.09240390f4b2580982227d9744d55661.pngecm_mslp_uv850_natl_9.thumb.png.c7fc17907be925fab7d42faae0eb11d8.pngecm_mslp_uv850_natl_10.thumb.png.195b83e297722a2f2dee646368029d19.png

Interesting that the ECM sends Maria (as an extratropical storm) to Greenland. The GFS places her further south crossing the Atlantic while the GEM takes her to the east US coast but in a weakened state.

Plenty of interest this morning.

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Posted
  • Location: Camborne
  • Location: Camborne
1 minute ago, karyo said:

Interesting that the ECM sends Maria (as an extratropical storm) to Greenland. The GFS places her further south crossing the Atlantic while the GEM takes her to the east US coast but in a weakened state.

Plenty of interest this morning.

Yes there is much still to be resolved next week.

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Posted
  • Location: Manchester Deansgate.
  • Weather Preferences: Heavy disruptive snowfall.
  • Location: Manchester Deansgate.
1 hour ago, karyo said:

Interesting that the ECM sends Maria (as an extratropical storm) to Greenland. The GFS places her further south crossing the Atlantic while the GEM takes her to the east US coast but in a weakened state.

Plenty of interest this morning.

Its good news further down the line, if we keep getting these hurricanes sending warmth into the polar regions, surely the polar vortex will struggle to form, keep them coming, OPI (if we get to see it ever again) could be through the floor this year!

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Posted
  • Location: Beccles, Suffolk.
  • Weather Preferences: Thunder, snow, heat, sunshine...
  • Location: Beccles, Suffolk.
4 minutes ago, feb1991blizzard said:

Its good news further down the line, if we keep getting these hurricanes sending warmth into the polar regions, surely the polar vortex will struggle to form, keep them coming, OPI (if we get to see it ever again) could be through the floor this year!

No offence, feb, but I think I'll stick with what the proper models say...As for the OPI? Well, if the prevailing conditions during October really are a useful predictor, of what's to come during the following January, wouldn't real meteorologist have picked up on it by now?

They would stand to make £billions!

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Posted
  • Location: Brighton (currently)
  • Location: Brighton (currently)
54 minutes ago, feb1991blizzard said:

Its good news further down the line, if we keep getting these hurricanes sending warmth into the polar regions, surely the polar vortex will struggle to form, keep them coming, OPI (if we get to see it ever again) could be through the floor this year!

I can see what you are saying but what about the poor arctic ice?

The 6z has some vigorous low pressure systems over us in FI.

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Posted
  • Location: Derbyshire Peak District South Pennines Middleton & Smerrill Tops 305m (1001ft) asl.
  • Location: Derbyshire Peak District South Pennines Middleton & Smerrill Tops 305m (1001ft) asl.

Yes a very mobile pattern showing on the 6z into Wk2, With some deep lows crossing the Atlantic on a very strong Southerly tracking jet-stream..

viewimage-4.thumb.png.ac00254655b2cd8ca91151e41fbd7f0e.pngviewimage-3.thumb.png.ef038d9dfd6fb929056872eedd2b3c99.pngviewimage-2.thumb.png.3c1f07afa52739ccca6c856245b5c651.png

 

 

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Posted
  • Location: Nr. Tunbridge Wells (150m/450ft asl)
  • Location: Nr. Tunbridge Wells (150m/450ft asl)

Maybe this will be the time when GEM gets it right and all the others get it wrong. Warm, dry and sunny all the way from GEM...

Interesting that ECM sends the remnants of Maria north next week, allowing the high pressure to 'seal' over the top of the first low tracking southeast, and potentially returning us to drier weather again. ECM far outperformed the other models in forecasting the last few hurricanes during the Carribean / North American stage - anyone know if that trend (outperforming other models in the 5+ days range) continued as they decayed into tropical storms and moved North?

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Posted
  • Location: Camborne
  • Location: Camborne

Both the gfs and ecm this evening develop the negatively tilted upper trough idea whilst strengthening and extending the high pressure' Quite a classic reversal of the jet but it also pushes the UK block further east and allows troughs ti impact the UK as they track east on the strong upper flow which is further south. The ecm is now bringing Maria into mid Atlantic.

gfs_z500a_natl_27.thumb.png.b33463a89a15b5ce1fd8a9e55091a8c1.pnggfs_uv250_natl_27.thumb.png.16e0b8b5d055ce62f3b2f4f01c46cc4c.png

The ecm

ecm_z500_anom_natl_8.thumb.png.c8bf9d3811277e6ea9d5406dcb184078.png

Edited by knocker
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