Model output discussion - hot spell beckons but then what?

[MATTWOLVES 3]

ECM 0z not ending to badly... Pressure rising from the SW while pressure falls over Greenland. This pretty much backed up by the mean as well! 

 

[Summer Sun]

A bit of everything over the next 4-weeks looking at the ECM weeklies with some warmer drier spells and some cooler wetter and drier spells

[johnholmes]

5 hours ago, Ed Stone said:

Still on course for something cooler (hardly difficult!) over the coming 16 days...according to today's GEFS 00Z ensembles. Proper sleep, here we come!

   

   

What has been pretty consistent for a fair number of days, looking at the predicted 850 mb temperature prediction. The dip around 29 and the brief rise before a general fall. It really has been a consistent signal for some time if you look back over the past ? week or so.

[mb018538]

End of the 6z run - what we will probably end up with in December/January when patiently waiting for some cold. After months of raging negative NAO it'll flip like this to strong positive. 

[northwestsnow]

1 minute ago, mb018538 said:

End of the 6z run - what we will probably end up with in December/January when patiently waiting for some cold. After months of raging negative NAO it'll flip like this to strong positive. 

Hope so as there is a good chance of a cold northerly incoming

[johnholmes]

2 minutes ago, johnholmes said:

What has been pretty consistent for a fair number of days, looking at the predicted 850 mb temperature prediction. The dip around 29 and the brief rise before a general fall. It really has been a consistent signal for some time if you look back over the past ? week or so.

A quick check and there were signs of this even as far back 21 st with GEFS.

[mb018538]

16 minutes ago, northwestsnow said:

Hope so as there is a good chance of a cold northerly incoming

I love a good northerly - but only when they can pack a punch in very late autumn/winter. They can stay on the shelf for now! Definitely the best wind direction in the winter - the air is so pure and clear, not like those mucky grey easterlies. Ok they may bring more cold and snow, but not as enjoyable!

[knocker]

Layers of Ac and Cs have encroached here over the last two or three hours which are indicated nicely on the midday sounding. (possible frontal surface 500mb associated with the trough perhaps)

.

[feb1991blizzard]

4 hours ago, mb018538 said:

End of the 6z run - what we will probably end up with in December/January when patiently waiting for some cold. After months of raging negative NAO it'll flip like this to strong positive. 

Thats a good chart, i would take that in December, could easily develop into a potent Northerly from there in December.

[Frosty.]

The Gfs 12z operational isn't all bad, there's a nice spell of anticyclonic weather with pleasantly warm days and plenty of sunshine but as it's autumn by then, nights look cool, especially where skies clear and also a risk of mist / fog patches for a time.

[Mike Poole]

As the last proper hot day of this spell and summer fades away, and it is quiet in here, some early thoughts as to winter. The polar vortex is about to form, delayed wrt averages, here GEFS showing the turn of the month for net westerly winds at 10hPa 60N:

A good time to check sea surface temperatures, here global:

Warmth in the N pacific probably not good +PDO, Atlantic profile not looking bad, although would prefer stronger cold signal due WSW of UK.  Compare last year:

My view is that the cold area south of Greenland became our nemesis last year, not in play most of the time until the synoptic pattern brought the jet over that area, and it jee'd it up and bang went the chances of UK cold.  This year the SST should be more favourable, but quite a lot could change come December...

The QBO looks optimal this year, here up to August:

And solar minimum too, so that all looks good...

But, with MO contingency planners forecast putting Sep to Nov at 60% chance of being in the hottest 20% category (the strongest I've seen) even if the vortex gets off to a very slow start (I think it will) will the cold air be there to deliver a cold spell in December?  Beyond that a SSW may be very possible, but after last year's nail biting, are we sure it would deliver? 

A lot of questions, but I'm sure it will be a compelling spell of model watching...just have to survive Autumn first. 

More to say on this, as things unfold.......

Edited August 27, 2019 by Mike Poole

[Methuselah]

I refuse to get carried away with any talk of impending Snowmageddon: we've been there, too many times already!

Anywho, today's 12Z ensembles might still allow for some freakish warmth, come Autumn...Heat has, afterall, kept returning ever since February...?

   

   

I'm not saying it will happen; just that, when things keep repeating like this, there's usually a reason for it? Even though I don't know what that reason is!

[Frosty.]

Not a bad Ecm 12z operational, especially further south where plenty of ridging is shown and actually a good finish as high pressure builds in.

 

[damianslaw]

A return to changeable conditions for all, after what will have been a notably albeit shortlived burst of persistant significant heat.. three days of maxima of 33 degrees not to be sniffed at, at all.

The atlantic has a fair bit of energy in it, and a generally westerly flow is to take hold, temperatures back down closer to average away from the SE which will hold onto to some late summer warmth. Some heavy rain for NW parts as well, which will help to bump up the high rainfall totals experienced this month in such parts. Its been a thoroughly wet one here in the Lake District.

As we end summer and enter September, an autumnal shot will descend on northern parts, some cool uppers from the NW, which could bring the first ground frost for sheltered parts if skies stay clear for long and winds fall light.

Into September - high pressure to the SW looks like nosing NE, but perhaps won't manage to get enough a stronghold on the UK to prevent weak frontal systems from the NW edging down, a fairly quiet start to September though, with temps very near average - very typical for the time of year, which tends to often be very quiet.

[knocker]

Outlook - a period of cooler and more unsettled weather will effect the UK

The North Atlantic 500mb and surface analysis for midnight and the 0300 sat image

A cloudy start to the day in many areas and the band of rain associated with the cold front, already into the south west, will track steadily east through the day effecting most of England and Wales apart from the far south east, It will be heavy in some western areas. The passage of the front heralds the introduction of cooler air and further north showers will occur in this more unstable air over N. Ireland and Scotland

The front and rain will clear the south east by the early hours resulting in a pretty clear night for all but by dawn another frontal system associated with the low centred pretty close to the position of the old OWS Station India at 20W, will bring more rain into western Scotland

The rain will spread across the rest of Scotland and N. Ireland during Thursday but being concentrated in the west of Scotland and it will be accompanied by strengthening winds. Elsewhere mainly dry with perhaps a few odd showers

By midday Friday amplification of the subtropical high zones has neatly encircled the upper trough so it's not going anywhere fast and further frontal systems track north east and thus bring more rain to the north and a continuation of blustery winds, Drier further south

Over Saturday the cold front will track south east resulting in a band of rain for most areas with frequent showers following behind in the brisk north westerly wind

Little change in the overall pattern on Sunday with the country in a showery and quite cool north westerly regime with perhaps some longer spells of rain as the showers coalesce

 

 

[knocker]

During the beginning of next week the energy running south of the trough over NE Canada does introduce more fluidity across the Atlanticand the in situ upper trough does get shunted east. thus after a transient ridge more frontal systems effect the north over Tuesday night as they track around the subtropical high in mid Atlantic.

From this point the gfs starts to promote the subtropical high in the Atlantic to eventually be the main influence over the UK but this does seem to be tied in with it's handling of TS Dorien tracking up the eastern seaboard so just a watching brief at the moment, particularly as we are now way out in the unreliable time frame

 

Edited August 28, 2019 by knocker

[knocker]

Predictable the ecm disagrees with the gfs on the evolution next week with no TS on it's travels and thus a much more mobile Atlantic portending a continuation of unsettled weather

 

[NApplewhite]

13 hours ago, JON SNOW said:

The Gfs 12z operational isn't all bad, there's a nice spell of anticyclonic weather with pleasantly warm days and plenty of sunshine but as it's autumn by then, nights look cool, especially where skies clear and also a risk of mist / fog patches for a time.

Looking very settled for at least 10 days in early to mid September, as is often the case! 

[Methuselah]

A mostly uneventful 16 days, should the GEFS 00Zs be correct:

   

   

[knocker]

In the 6-11 period the EPS is suggesting that the mean anomaly amplifies the Atlantic subtropical high north east portending temps a little below average and the better weather to the south west

 

Edited August 28, 2019 by knocker

[knocker]

EPS  - Dorian

 

[knocker]

The difference in the airmasses at midday. Camborne slap bang on the cold front with solid cloud up to the tropopause and Valentia in the cooler. clearer and more unstable air behind with potential cloud tops up to just below the much lower tropopause.

Sat image 1400UTC. Tomorrows frontal system clearly visible west of Ireland

Edited August 28, 2019 by knocker

[knocker]

The 5-10 GEFS this evening is subscribing to what appears to be the percentage play at the moment. To wit  a generally upper westerly flow across the Atlantic but with the subtropical high pushing north the likelihood of some regional variations with the south west perhaps benefiting more in the precipitation and sunshine stakes. Temps below average

[knocker]

GEFS 1200 - Dorian

[Mike Poole]

A settled start to September for Southern areas from the 12s tonight, with all models having the south at least under pressure above 1025 hPa by T144:

Following the hot spell, a degradation into unsettled weather generally is not the form horse into early September.