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Model output discussion-mid Autumn and beyond


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Thanks knocker. Useful to come over to this thread for a dose of reality rather than seeing P14 of the 18z GFS run which shows cold weather at 300 hours, when we all know that it's standard wet, windy

Hi Malcolm, I just saw your post after doing mine above. Yes this thread seems under used which is a shame.The idea of this one as you probably know is for any members to post what hopefully

Finally getting time to check how the 500 mb anomaly charts have been over the past week. They have not consistently but generally gone from suggesting trough domination to one that now has ridging as

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The pattern change to Atlantic driven weather looks still to be still on course for next week.

GFS T120hrs shows the Greenland vortex with deep low pressure sending bands of wind and rain across the UK.

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Quite an active Atlantic jet tracking across our latitude by then,pushing the cold air back east for the time being.

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Temperatures lifting somewhat as could be expected under the south westerly regime although  some cooler incursions in this pattern will come from the north west behind passing cold fronts.

 

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1 hour ago, Summer Sun said:

Might have to batten down the hatches on Wednesday away from Scotland

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Yea, there is no model on tonights runs that does not bring some disruptive gusts to parts of the country midweek, hopefully things won't verify with gusts this strong 

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The Atlantic is back in full control of the weather by the end of the week as shown by (in order) the UKMO, ECM, GFS and GEM:

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Another low pressure system lining up in the far west to follow this weeks deep Atlantic depression looks likely to continue the unsettled conditions into early December.  No sign of any meaningful blocking in the foreseeable future so we may have to wait until mid-December for any sign of serious cold appearing.  The situation can change within quite short time frames, of course, but these charts don't look likely to alter much in the coming days.

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The 12z GFS shows a vigorous Atlantic over the next  few days starting tomorrow and continuing into the weekend.

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A strong jet pattern wavering across the UK and a large area of low pressure in the Atlantic.Wet and windy spells and temperatures on the rise as the south westerly spell establishes.

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Looking further ahead to next week from what the ens charts are showing - and a relaxation of the Atlantic jet seems the likely way forward.

A look at day 10 on GFS and ECM mean NH pattern.

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The shrinking back of the Greenland vortex towards Canada as pressure rises from the south towards southern UK.At this stage a mean downstream Scandi/E.European trough developing..The jetstream shifting north.of the UK.

Some drier,quieter weather probable as the high builds although at this stage surface conditions will depend much on how far north it situates.Currently ens are showing this high around N.France with ridging into Southern.UK. This would likely spill a lot of cloud in over the top on a damp south westerly .The expected high could develop further north of course given the +ve ht.anomalies showing across the polar field but for now it is modeled as a mid-latitude feature.

 

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The ECM weeklies don't indicate anything overly cold out to December 23rd maybe week 3 could be a bit cooler with a signal for slightly below average in ROI and NI otherwise above average looks most likely 

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The 12z Gefs shows a brief respite around days 7/9 as a sub topical ridge builds north across the UK but it now promises to be only a transient feature and by day 10 it's normal service again.

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No sign of a let up of the Atlantic westerlies yet. 

 

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According to the ecm a succession of frontal waves ensures periods of rain for most over the weekend as fronts traverse the country

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and then on Tuesday the upper trough in mid Atlantic splits under renewed, but brief, amplification of the twin high pressures, and by Wednesday a surface low has swung north east over the UK with some more rain and perhaps some strong winds/

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Which basically sums up the run which is very unsettled.with a lot of energy exiting North America across the Atlantic courtesy the Polar and subtropical jets.

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Edited by knocker
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The gfs and ecm det. runs depicted a pretty unsettled scenario this evening so worth a look at the the GEFS and EPS medium range anomalies to confirm or not.

The obvious difference between the two is the handling of the twin vortex lobes and the upstream amplification. But taking that into account they are essentially on the same page with a very strong westerly upper flow exiting North America south of the trough in the NW Atlantic and the Iceland/Greenland ridge and thus retaining quite a strong westerly flow across the UK. Ergo this portends a continuation of the unsettled weather with temps around average.

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And this evening's NOAA doesn't appear to have any issues with this

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Moving very briefly on from the short range and the gfs whips the aforementioned low through the UK at T144 introducing very briefly a cool northerly before the next major low arrives.

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Edited by knocker
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The Jetstream is expected to have the UK directly in its sights over the next few days as seen by the GFS:

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This pattern continues pretty much uninterrupted through to the end of the GFS run at +384h.  This would not allow any periods of settled weather to get established and may bring more in the way of windy and wet conditions for most of us until well into December.    

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Just my personal opinion, but not feeling confident of anything particularly cold occurring within the next week or so. The NOAA anomaly charts posted both here and by John Holmes on the Hunt For Cold thread don’t really support it (accept for the possibility for some cooler weather more from the West rather than the milder South-Westerly direction at times. Though expect Northern areas would be the coolest in that sort of setup). 

Just feel, however, the modelled blocking to the North, especially towards the Arctic, will unlikely to be far enough South for the cold and snow fans to benefit much. Obviously things can change and having an Arctic High can help dent the Vortex and maybe lead to some alluring opportunities further along Winter’s footpath. But just seems like the Atlantic, at the moment, has a little bit too much power to allow much in the way of favourable ridging to develop for cold and snowy weather. Maybe Northern high ground seeing some wintriness on occasions and a slight chance of a more widespread wintry event early next week. 

I think it’s also the case sometimes, some of us have our expectations set too high. It’s true really that seeing snow before Christmas, unless possibly on high ground to the North, is uncommon. Same for Polar Express quality Easterlies. They don’t happen often in the U.K. 

Despite that, feel like some, not necessarily on this thread, are being a little too eager to dump their teddies from the pram, even though I appreciate it’s a frustrating time for some, currently. 

I’d be happy to take a mild and dry spell if nothing particularly wintry turns up in the next 2 weeks. It’s just as well cold and snow isn’t the only weather type we’re restricted to (but nothing wrong with people liking it ? ). 

Edited by DiagonalRedLine
Modifying last paragraph
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