Model Output Discussions 12z 01/09/2016

[No Balls Like Snow Balls]

Interesting as the CFS majority of the time has been going for a below average October, T2M wise. 

[mb018538]

The battle of the seasons...



Big summer heat still holding across the west of the USA, and the bitter cold starting to bottle up across the pole.....ready to spill its way down to the UK Greece for the winter months!

[legritter]

3 hours ago, mb018538 said:

The battle of the seasons...



Big summer heat still holding across the west of the USA, and the bitter cold starting to bottle up across the pole.....ready to spill its way down to the UK Greece for the winter months!

You were right first time ,back on topic some autumn weather proper arriving soon but the high pressure belt still clinging on , catch you all up later .

[joggs]

3 hours ago, legritter said:

You were right first time ,back on topic some autumn weather proper arriving soon but the high pressure belt still clinging on , catch you all up later .

Yes it'll be interesting to watch the high,low pressure battle in the coming weeks.Also re,the chart above,some nice cold spilling into siberia.

[phil nw.]

GFS and UKMO still showing the jet angled sw to ne bringing pulses of warmer air across the south between the occasional fronts.

Days 3 and 4

Looks quite decent with warm sunshine towards the end of the week with maximums in the low 20'c quite possible in favoured spots.

We do see those fronts then, coming through by Sunday with some rain before more ridging from the Azores high.

This looks to be the continuing pattern as we go into next week before signs of the jet flattening out somewhat and winds turning more westerly bringing more of a cooler Atlantic feel.

2m Temp. and rainfall graph for C.England

shows that gradual cooling off expected in week 2 although at present there is still a lot of dry weather expected away from that north western corner where the Atlantic systems continue to be more active.

 

 

Edited September 20, 2016 by phil nw.

[mb018538]

Looks like some firming up on details now. What tentatively looked like a build of pressure may be scuppered by the deepening low. Looks pretty windy at times, especially so in the NW. Some warmer interludes in the SE.

[damianslaw]

Today's models suggesting the atlantic will power up somewhat next week, kicking into touch ridge development from the SW and more significantly ushering a generally much cooler spell of weather. Indeed signs the azores high may be forced to ridge NW and the trough becomes slow moving and anchors itself down across the country locked in place by height rises to the NW, end result would be a chilly NW flow as we approach October. All along way off, and the next few days promise further rather quiet conditions, with wettest cloudiest conditions reserved for the NW, whilst the SE holds onto generally fine pleasant weather with respectable temps for late September.

 

[Polar Maritime]

The GFS shows a much cooler/unsettled N/Wly flow into next week, Possibly cold enough for the 1st snowfall of the season over the highest Scottish Mountains..

 

Edited September 21, 2016 by Polar Maritime

[mb018538]

ECM this morning shows a brief incursion of tropical air as one of the ex-Atlantic tropical depressions is scooped up by the Jetstream by midweek:



 

After this it favours low pressure being parked out west and over Scandinavia, with higher pressure near the UK (albeit under a cool NW wind)

[summer blizzard]

GFS suggests that Autumn is well and truly here now with the jet stream depressed and lows firing at us. 

Euro would be pleasent away from the north and east with a chilly inverted flow. 

[mb018538]

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

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

On yesterdays update at the moment, but not too far off today's output showing NW'erlies establishing in time. GFS still showing more dominant high pressure, but I expect that will change.

[Summer Sun]

A much more Autumnal look to GFS as we move into October

The ECM D10 chart couldn't be more different to GFS...

Edited September 21, 2016 by Summer Sun

[johnholmes]

The second quote is the ECMWF-GFS output from this morning?

The overall trend does seem to be some kind of ridging veering the flow at 500mb to be north of west into the UK. That does not necessarily mean a NW flow at the surface, if that is what you meant?

 All 3 output centres have been reasonably consistent over the past few days but with some variations and of course the ever present risk of a Tropical Storm/Hurricane getting into the N Atlantic to upset things.

[Paul]

Looks as though we may have an ex-hurricane not too far away next week which will probably have the models dancing about a bit over the coming days. Nick's written a blog on that + ex-hurricanes visiting the UK in general:

Ex-Hurricanes Visit The UK In September

[phil nw.]

The overnight means show there are subtle differences next week with perhaps the GFS a looking more unsettled at day 10

 

As Paul has pointed out there are signs of tropical lows currently in the picture-just a look at 2 images at the same time on day 4 from the 06z GFS and ECM 00z we can see some developments in the south Atlantic 

All images courtesy of Tropical Tidbits.http://www.tropicaltidbits.com/

 

even at that early stage subtle differences in modeling them can be seen.

Interaction with the jet or any merging with the main Icelandic trough will affect how the Azores high may get pumped up ahead as we go into next week.

We can see by next Thurs how the Op runs develop those differences

 

ECM going on to build the Azores high much closer than the GFS which looks to model a flatter pattern by day 10.

 

 

 

 

 

Edited September 21, 2016 by phil nw.

[Summer Sun]

The 1st snow run of the season has appeared

[Daniel*]

A more cool start to October at this stage looks to have the upper hand with southwesterlies at the backend of September, potentially becoming northerlies as we delve into October. We have had some balmy Octobers in recent years, one thinks this one will be different, a punt of a lower CET score looks to have more credence than an above one IMO. Quite a fair bit of northern blocking evident isn't there a correlation with low sea ice? I would reckon there would be the first ground frosts for the far north, and I suppose the tops of Scottish mountains will grow increasingly white although this can be fickle - if this run materialises, not quite what we traditionally see, but welcome for a wintry hearted man.

 

[Daniel*]

No comment on ECM that's startling -NAO at least there's no mass hysteria! 

It brings the northerly winds in quite a fair bit sooner to say the least. I believe the blocking in the Atlantic, is an example of an omega block? With cyclonic activity off Newfoundland hitting the buffers, if only we could fast forward time - as this thread would be markedly more active.  

 

Edited September 21, 2016 by Changing Skies.

[knocker]

The GFS this morning.

Tomorrow it continues to track the main depression NNE to Iceland whilst at the same time a shortwave forms in it's southern circulation that tracks NE to be 986mb NW of Scotland by 00z Sunday with associated fronts orientated N/S along the western edge of the UK introducing some wet and windy weather,

The situation then becomes slightly complicated as Karl tracks north and interacts with other low pressure areas to form a deep low in the western Atlantic. This area engages a very strong jet and tracks rapidly ENE north of the UK . This has the potential, depending on the precise track, of bringing some quite strong winds and heavy showers, particularly to the north with the south again drier and feeling the benefit of any possible ridging from the Azores.

Having said that this scenario is along way from being a done deal

See current model guidance for Karl

[mb018538]

Yes all will hinge on Karl - and the models are still clearly having some issues resolving this. Anything beyond here is next to useless at the moment, as where Karl ends up will completely vary what could happen afterwards.

[mb018538]

ECM broadly similar to UKMO out to 144 - it also sets up a nice brief crisp NW'erly by day 9....the start of frosty nights for the north!

[mb018538]

How about this too from Michael Ventrice....interesting!
 

 

[Summer Sun]

A more seasonal start to October with a northwesterly flow bringing some cooler air

[knocker]

Regarding Karl the ecm is more or less on the same page as the GFS albeit not quite so complicated. It runs the remnants of Karl NE into the central Atlantic where it engages the strong SW/NE jet (170kts) which whips it across northern Scotland 12z Tuesday which could bring some very strong winds to the area for a short time.All of this is very dependent on the track which has still to be resolved.

 

Edited September 22, 2016 by knocker

[sundog]

On Saturday, September 17, 2016 at 10:22, sundog said:

 

Ive been thinking the last day or two looking at some of the charts of a possible chilly first week of Oct. Just a thought anyway.

 

52 minutes ago, Summer Sun said:

A more seasonal start to October with a northwesterly flow bringing some cooler air

last week i thought the models were at times hinting of a chilly first week of Oct, those hints have this week gathered some momentum for early Oct.

Edited September 22, 2016 by sundog