Model Output Discussion - Into Autumn 2019.

[SMU]

18 minutes ago, feb1991blizzard said:

Some quite staggering charts showing for this early, not even really out of the closed season yet, of course its arbitrary when it ends and not really a definition, but i would say its the point at which its scientifically possible for low level snow not just in the North to come into GFS range.

A chart like that has never verified in Sept - I checked back to 1948!

[feb1991blizzard]

3 minutes ago, Steve Murr said:

A chart like that has never verified in Sept - I checked back to 1948!

This is the nearest i can find to it but its not as long a fetch and as big a - NAO.

[Methuselah]

39 minutes ago, Steve Murr said:

A chart like that has never verified in Sept - I checked back to 1948!

They don't verify all that often, in Dec, Jan or Feb, either. More to the point?

[jules216]

I see there are a lot of talks around the web about what will NAO do in winter,but even in -NAO you can have a very mild setup with cut of lows under the block which can remain static under poor setup in Europe, esential is to have low pressure around Italy and eastern Europe. This May-August -NAO stretch didnt bring any cooling in Europe which was allround very  warm for summer,with exception of May, there is a persistant poor pattern in Europe for longer term cold spels in summer or winter in last 5 or so years with only isolated odd month producing below average(1981-2010) outcome.

[LRD]

As well as bringing in an unusually cool couple of days next weekend, this GFS run downplays any longer term high pressure build over the UK (it is still modelling a massively bloated Azores High in the Atlantic and over Europe - an all too familiar sight in the last 15-20 years), leaving us open to rain-bearing lows off of the Atlantic

Autumnal. As it should be in early October. Let's see if this downplaying of high pressure continues over the next 2 or 3 days or if it just proves to be a blip

Edited September 22, 2019 by LRD

[knocker]

Nice depiction this evening of the frontal system due to arrive tomorrow

 

[feb1991blizzard]

Can't fault the polar profile on the ECM.

[Methuselah]

Tonight's GEFS 12Z ensembles still have the GFS Op going up and down, amongst a pile of scatter; so still no definitive idea as to which way things will eventually go...And, as for the value of the NAO Index, in three-four months' time...Not even Nostradamus knows the answer to that one!

   

   

The two cold days? Looks like someone 'missed' when playing Dot-to-Dot!

[knocker]

The intense upstream amplification has induced an impressive cold arctic plunge down the western half of NA and WAA into the eastern half and in particular Greenland

Closer to home still looking unsettled as the trough moves east

Edited September 22, 2019 by knocker

[feb1991blizzard]

8 minutes ago, Ed Stone said:

 

The two cold days? Looks like someone 'missed' when playing Dot-to-Dot!

Yes but its only a time outlier really, others bring the Northerly plunge in just a day later.

[Frosty.]

Looking at the Ecm 12z operational longer term, with hurricanes / tropical storms in the mix it's best to take anything it shows with a larger pinch of salt than usual!

Edited September 22, 2019 by JON SNOW

[I remember Atlantic 252]

7 minutes ago, feb1991blizzard said:

Yes but its only a time outlier really, others bring the Northerly plunge in just a day later.

I like the useless model GEM, but as Jon says very uncertain and chances of GEM FI coming off is zero

[January Snowstorm]

The big news for me over the last 12 months is the icon model becoming more and more a factor. It comes out first and it's becoming a great trend setter for both the morning and evening runs.....how many times have we seen the ecm follow it's lead!

[feb1991blizzard]

26 minutes ago, I remember Atlantic 252 said:

I like the useless model GEM, but as Jon says very uncertain and chances of GEM FI coming off is zero

I would not say the chances of that hot setup are zero, ECM right at the end is fairy hot.

[knocker]

NOAA and the ext EPS are pretty much as expected with nothing of a particularly nasty nature lurking in the woodshed. Both have a trough in the western Atlantic with a westerly upper flow running around the subtropical high which is nudging north in the eastern atlantic.With the centre of the surface high to the south west this would suggest a north south split but temps not too bad and above average

Current North Atlantic SST anomaly

[damianslaw]

Lots of change in the models just beyond reliable at the moment - as ever take anything show beyond 144 hrs with large margin for error and correction. What is interesting to note is the arctic profile being consistently shown, one of high pressure - a theme since late April.. also quite an amplified flow to end September - two features that don't tend to come together at this point in the year, when we should see the jetstream steamrolling through on its normal westerly trajectory. What it means is a rather sluggish trough coming unstuck against heights to the NE, indeed trough disruption, with slow moving bands of rain under a SW/W air stream with every chance a potent northerly could quickly come in, or indeed ridge development through the UK, with low heights becoming cut off to the SW. Lots to keep an eye on, not least the impact of ex tropical storms..its the time of year when high pressure blocks have a hard time making there influence known, less intense heat and cold dense air, meaning we can be left sandwiched in a bit of a no-mans land with the 'major forces' struggling to exert enough dominance for the time being..

[MATTWOLVES 3]

For me I have to say... Its far to early to be talking up winter prospects just yet... Its September still!!! I can't see any potential winter bite till at least mid late November! The ECM mean brings some unsettled conditions next week, but the mean shows high pressure building towards the South later on, and again brings somewhat of a warm up. A very early call from me would be  a relatively settled 1st part of October.... Beyond that is anyone's guess. 

[Jordan S]

A tropical storm or hurricane has been modelled in the same place from the gfs for several runs in a row on the bottom left of the charts for the time period of 150-210 hours usually I see the placement of any tropical system vary in strength and position drastically at that range just thought I would note that.. Ofcourse anything at that time frame is uncertain whether its consistent or not. Nice to see some much needed rainfall for my area in the south east

[knocker]

Outlook - very unsettled with some strong winds and heavy rain at times over the next few days

The North Atlantic 500mb and surface analysis for midnight

Still some showery rain around in the north of England and particularly northern Scotland at the moment and probably a few showers continuing through the day. Elsewhere dry with sunny intervals But the frontal system associated with the quite deep low to the west of Ireland will soon bring rain to the south west and this will track north east during the day.

The complex frontal system will cover the country through this evening and overnight with the showery rain continuing in most areas, particularly the north, But during the latter part of the night heavy rain and strong winds, with thunderstorms embedded, will encroach the south west and move ENE early Tuesday morning. A distinct possibility of some torrential downpours here.

The rain and storms will continue tracking around the circulation of the low, now centred and filling over south west Ireland, so a wet and windy day for many with showers following behind the main rain belt and only the far north west escaping

By Wednesday low pressure dominates the eastern atlantic with a new trough on the scene west of Ireland.generally and the day will be breezy with sunny intervals and showers.but more heavy rain is fast approaching from the west associated with the new frontal system

The fronts and rain sweep across the country on Thursday resulting in a wet and windy day for most to be followed by heavy showers

Come Friday the surface low is north west of Scotland with the UK well within the circulation. Thus a day of sunshine and showers with some longer spells courtesy of any troughs embedded in said circulation

Edited September 23, 2019 by knocker

[knocker]

Sticking with the gfs we are now reaching a position hat has previously been discussed.

By midday Saturday a trough has sneaked around the north of Greenland to  phase with TPV/trough northern Russia and the Atlantic trough which is slowly moving east

All of this resulting in two energy flows around the Greenland/Iceland block and tricky surface detail which is yet to be finalised

For those in the E/SE with a vested interest the likely rainfall this sort of evolution would be better news. For what it's worth

 

Edited September 23, 2019 by knocker

[mb018538]

High pressure looks like it's really struggling to build in now as time moves on and we get a better idea of the Atlantic evolution & tropical situation. It tries - but ultimately there is too much energy and momentum from the west and it just gets squashed. That said, the ensembles still look drier as we move into October, a result of the highly amplified global pattern:

[knocker]

It wouldn't be exactly bad news if the track of the frontal wave came to pass next weekenf

Tacking a NH view the ecm has a not dissimilar start to the evolution over the weekend but quickly moves the trough east with the TPV over northern Scandinavia.At this point it's worth another look at the amplification over North america

 

[Methuselah]

There could still be time for another toasty weekend yet...16C T850s in October?

   

But...as the GEFS 00Z ensembles suggest, the will-it-or-won't-it northerly might still be a bit of a bugbear:

   

   

However, be that as it may, the SE Mohave should see some useful rainfall, at last!

[SLEETY]

Long fetch  Northerlies are not that uncommon in the Autumn,it's in the Winter when you really want them that they seem almost unheard of to appear

Edited September 23, 2019 by SLEETY

[I remember Atlantic 252]

25 minutes ago, SLEETY said:

Long fetch  Northerlies are not that uncommon in the Autumn,it's in the Winter when you really want them that they seem almost unheard of to appear

can be common April and May as well