Model Output Discussion - Into Autumn 2019.

[knocker]

With reference to a previous postThe ecm this evening and previous run at t144, 168

Thus this evening's chart for Sunday but still obviously open to correction

 

Edited September 15, 2019 by knocker

[Frosty.]

Well there's very good news if you're looking for another encore of summery weather as we approach the Autumnal equinox because according to the Ecm 12z operational it's not only going to be another week dominated by high pressure but it's also becoming very warm again for a time later in the week, especially further s / se where mid to upper 20's celsius are again indicated..it does become more unsettled and cooler in FI but summer isn't finished with us just yet..Indeed longer range indications are that southern uk, especially the southeast could / should see plenty more fine and warm weather in the weeks to come!!!!

 

Edited September 15, 2019 by JON SNOW

[knocker]

The North Atlantic 500mb and surface analysis for midnight and the Nottingham sounding

The country today is divided by the front that is moving slowly south (see the sounding). Cloudy with bits and bobs of rain/drizzle south of it and much clearer with showers in the north which could be quite heavy over Scotland later

patchy precipitation will slowly clear this evening as the weakening front continues on it's travels leaving clear periods for most so some fog/mist around and even the odd ground frost in places

By Tuesday the high cell, centred over Galway, is pretty much in charge so a sunny day for most once any mist/fog has cleared, perhaps the odd shower in the north. But a warm front tracking around the periphery of the high could just bring some rain to NW Scotland by early evening.

Much the same on Weds after a nippy start to the day

No huge change over Thursday and Friday, but the high cell is shunted east east under pressure from the energy diversifying around it. So a couple of pleasant days after a cool start

 

[knocker]

Pressure on the ridge continues over the weekend and it quickly leaves the scene which becomes quite complicated as the Atlantic trough disrupts, courtesy of the aforementioned battle, This is of course according to the gfs

This morning's GEFS medium term mean anomaly indicates the trough becoming much more influential and a return to a more zonal Atlantic

[knocker]

Initially the ecm develops a small. quite intense surface low as the upper trough deconstructs over the weekend but simultaneously it tracks another upper trough down the west coast of Greenland into the Atlantic and develops another low at the base of this which undergoes explosive cyclogenesis along the left exit of the jet. Clearly much uncertainty in this area still to be resolved

 

[johnholmes]

The change in the upper air pattern from ridging being dominant to troughing taking over is now well underway.

https://www.cpc.ncep.noaa.gov/products/predictions/610day/500mb.php

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

[knocker]

19 minutes ago, johnholmes said:

The change in the upper air pattern from ridging being dominant to troughing taking over is now well underway.

https://www.cpc.ncep.noaa.gov/products/predictions/610day/500mb.php

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

Indeed John and this morning's ext EPS mean anomaly

 

[knocker]

[Methuselah]

This morning's GEFS ensembles clearly suggest a more unsettled spell of weather is now incoming -- reasonable temps and a better chance of seeing some rain than for some time:

   

   

Edited September 16, 2019 by Ed Stone

[northwestsnow]

Looking very much like those progressive op runs from GFS/EC were on the money wrt something more unsettled as we head towards the weekend.

How unsettled and for how long is the next question.

The Atlantic looks very powerful and the block will be blown away into Europe as it stands..

[shaky]

1 hour ago, Ed Stone said:

This morning's GEFS ensembles clearly suggest a more unsettled spell of weather is now incoming -- reasonable temps and a better chance of seeing some rain than for some time:

   

   

Lets be honest  Ed that is one dry ensemble graph all the way till the end!!i mean 2mm of rain max !!!it might aswell not rain at all lol!!the weekends high is proving to be a lot more resilient than what was shown 2 or 3 days ago aswell!!would not surprise me if this warm spell gets extended slightly!!gfs 06z gives a belter of a saturday and sunday looks warm still!!

[Methuselah]

Aye, I agree...And the outlook will be very dependent upon how the Atlantic trough develops: will it stay out west and drag-up warm air, or will the LPs migrate into Scandinavia? Or will a flatter zonal pattern set up?

   

[Methuselah]

And today's GEFS 06Z ensembles continue with the uncertain future; from Day 7, the SLP ensemble goes rather haywire.

   

   

And, when SLP ensembles go haywire, the others must surely follow...? Baa humbug!

[knocker]

The interesting question here is, if you only had the clusters available would you get near the det, run solution? Of course different map projections doesn't help

And roll it on

The obvious answer here is await the next run to reevaluate post T144

Edited September 16, 2019 by knocker

[knocker]

Latest on Humberto and the EPS

[Methuselah]

Maybe we should make-do with some long-fetch southwesterlies? There have been plenty of post-T240 solutions of late...

   

[Methuselah]

It's that time of year again, when summer is over and winter's yet to begin...so I'll nae bother with trying to make the weather sound interesting!

Needless to say, the GEFS 12Zs are hardly exciting:

   

   

Though it might rain!

[knocker]

According to the ecm this evening there are quite complex developments involving the upper trough in the Atlantic as it and the energy finally removes the ridge over the weekend

The trough in the eastern Atlantic is given a boost by energy running around the north and south of the East American ridge and an intense upper low forms west of Ireland by midday Sunday

Over the next 48 hours this low moves rapidly away to the north east but another major upper low has tracked east and if this is anywhere near the money some very windy and unsettled weather is a distinct possibility next week. Of course this is a fair way away so merely worth keeping an eye on at the moment

Edited September 16, 2019 by knocker

[MP-R]

1 hour ago, Ed Stone said:

It's that time of year again, when summer is over and winter's yet to begin...so I'll nae bother with trying to make the weather sound interesting!

 

Autumn first with its various complications, late tastes of summer, early tastes of winter, and Atlantic storms. Then again, maybe just mellowness like most of last October.

I'm interested in the possibility of something thundery over the weekend if the Atlantic trough takes on a more negative tilt with a surge of warmth ahead of it. Saturday looks like being warm and feeling quite humid, perhaps Sunday too albeit less settled. When the door finally opens, I think an Atlantic spell of sorts is pretty likely. Question is whether a nationwide unsettled spell or a N/S split again, in which case the south would stay drier.

[knocker]

And the EPS and NOAA confirming the unsettled outlook

[Mapantz]

A few posts moved to the Autumn moans/ramps/chat as that's where they are best suited.

Thanks.

[feb1991blizzard]

Number 13 doing what the op just about failed to do, an impersonation of the 17th Dec 2010, same setup except obviously it drops a regulation upper trough instead of a chunk of polar vortex.

 

[knocker]

High pressure will dominate over the UK this week so cue to keep the waffle to a minimum

The North Atlantic 500mb and surface analysis at midnight

As stated with high pressure in charge today > Thursday dry, sunny with light winds for most, so very pleasant after a chilly start to the days. The one exception will be the far north where some cloud and light rain may intrude, courtesy of the stray front moving around the periphery of the high cell

By Friday the country is still under the influence of the high cell but it been shinted to the east by pressure from the Atlantic with the upper trough to the fore.

The shunting continues on Saturday, albeit the ridge is quite resilient, and the movement results in probably the warmest day of the week. But cloud and rain from a front slowly moving east will effect western regions during the afternoon.

By Sunday the large, and complex, Atlantic trough is in charge and a wet and windy day is on the cards for the UK

This frontal system clears away quite quickly but an intense surface low has tracked rapidly north east to be 969mb NW of Ireland by midday Monday and the associated fonts will bring strong winds and heavy rain to the north. This is according to the gfs

 

 

Edited September 17, 2019 by knocker

[knocker]

The GEFS medium term mean anomaly indicates remaining changeable but with a NW/SE bias,

[Methuselah]

Well, just before I wander away to get my last(?) Vitamin D infusion of the season, the change to a more unsettled regime is about to get underway:

   

   

So, not a bad set of GEFS 00Z ensembles all told, and some much-needed rainfall to boot!