Model Output Discussion 01/09/17

[phil nw.]

Here is a new thread as we start the Autumn quarter.

Today's model runs continue to indicate a pretty mobile Atlantic pattern through the coming week by the looks of things.

A glance at the latest fax for Monday shows plenty of frontal activity heading in from the west ending our short little fine spell for today and tomorrow.

http://www.meteociel.fr/ukmo/fax/fax84s.gif?3

and below we have ECM mean chart for the end of next week, continuing to show the westerly theme

http://www.meteociel.fr/modeles/ecmwf/runs/2017090100/EDM1-168.GIF?01-12

Low pressure moving across to the north and the Azores high only able to ridge briefly between the rain bands the new month looks to start on a rather unsettled note with, as often the case in this setup,the best of any brighter spells further south and east.

This seems to have been the story of much of our Summer and this pattern seems set to continue for now. 

 

[ANYWEATHER]

Evening All , Despite an unsettled outlook , there will be some fine spells of weather in between the rain bands , models struggling with any detail , but looks as though there will be some flirty pressure rises

[Allseasons-Si]

Thanks Phil for the new thread

i just hope that the GEM isn't right

looking at most of the main models,low pressure does seem to show a NW-SE tragectory with the influence of high pressure over scandi forcing them that way,well it is the first day of autumn.

 

[Summer Sun]

GFS has probably one final blast of heat as we move through week 2 of the month

[Frosty.]

And a heart shaped cold green blob for parts of scotland with 10/11c, talk about rubbing salt in the wounds of the last 3 months..roll on winter!

Edited September 2, 2017 by Frosty.

[phil nw.]

No real change to yesterday's outlook with the expected onset of Atlantic weather for the coming week.

A look at the UKMO day 4 chart sums shows the establishment of the westerly flow with the Greenland/ Icelandic trough becoming more dominant with time and any Azores ridging heading east into the continent.

.

Last night's Ht anomalies for days 6-10 reflecting this expected setup.

so a fairly early spell of Autumnal weather to come it seems with the north seeing the worst of any wind and rain as low pressure is expected to head across to the north later in the week. 

[Summer Sun]

GFS still going for summer to return at the start of week 2

[phil nw.]

13 minutes ago, Summer Sun said:

GFS still going for summer to return at the start of week 2

Week 2 shows what could happen when we see more wavering of the jet flow.

Compare the differences in the way the 2 main models handle this for the Uk,of course this is around 10 days away so just for illustration really

As you show SS a brief taste f Summer as warm air from S.Europe wafts northwards ahead of a slow moving cut-off low out west.However look at the way ECM models this with a much more Autumnal cooler cyclonic period.

Either scenario is possible of course if this splitting of the jet occurs.

[johnholmes]

Yes phil the anomaly charts, a bit variable recently as they always are when tropical storms/hurricanes get into the Atlantic mix, but an unsettled outlook is what seems the most likely overall pattern for 6-14 days at least. Obviously a break now and then, 48 hours perhaps, and probably the usual Nw-SE differences.

NOAA 8-14 below

http://www.cpc.noaa.gov/products/predictions/814day/500mb.php

ECMWF-GFS

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

 

[Ross Andrew Hemphill]

The next 2 weeks look rather changeable in my area if you ask me...

[Frosty.]

I really won't mind the unsettled spell later next week  as the Gfs 12z shows if it's followed by what happens in low res which is a complete transformation into a spell of very summery weather..a price definitely worth paying!

Edited September 2, 2017 by Frosty.

[Sardonixs]

Need to keep an eye on next Saturday, defiantly looking Autumnal at the moment.

 

[Frosty.]

You can see it's not just the Gfs 12z operational which goes all summery as we head towards and during the mid month period. The GEFS 12z mean also indicates there is plenty of support for a gradual change from unsettled to settled with increasing height's to the east extending west across the uk with help from the azores bringing a lovely spell of anticyclonic weather for all areas..fingers crossed.

Edited September 2, 2017 by Frosty.

[Summer Sun]

A change to warmth (if it arrives) looks like it will be proceeded by a spell of autumnal weather

ECM 00z

12z

[Summer Sun]

At D7 we have ECM & GFS going westerly with UKMO going north westerly

 

[Summer Sun]

The ECM London ens shows the Op is overcooking the low somewhat around next Sunday

 

[Frosty.]

Tonight's Ecm 12z ensemble mean isn't as extreme as the operational regarding the unsettled spell from later next week, it looks like the north bears the brunt from the low pressure / unsettled weather whereas southern areas are not too badly affected, nothing like as bad as the op showed for the south. I really hope once we get through next week that week 2 will bring a marked improvement as the Gfs 12z op / Gefs 12z mean show in the run up to and including the mid september period.

Edited September 2, 2017 by Frosty.

[knocker]

Given that there is quite a bit going on at the moment what with tropical storms in the Pacific and Atlantic last night’s ten day anomalies are in pretty good agreement and not particularly cheery as far as the UK is concerned.

The NH pattern is highly amplified, particularly over Europe, but the key factor vis the UK would appear to be the lobe over N. Canada/NW Greenland with low pressure over the latter and associated trough aligned south east over the UK. With the Azores high pressure suppressed and not playing a significant role this establishes a fairly strong westerly upper flow across the Atlantic which portends some unsettled weather over the UK with temps somewhat suppressed and a little below average.

Looking into the ext period there is not great agreement. The lobe is still influential and some suggestion of retrogression of the Atlantic trough and perhaps to ridging just to the east of the UK but still a fairly unsettled outlook but perhaps more biased towards the north. Temps may well trend up to average.

As always the det. Runs will sort the details.

And so on to more detail this morning.

After a decent couple of days the next 48 hours looks pretty unsettled with a succession of fronts and outbreaks of rain move east starting this morning in the west where it has been raining for a while.

By Wednesday the main low is east of Iceland with only the north still under its influence as a transitional ridge builds in from the south west But by Friday the next low, spawned by the  N. Canadian lobe, has tracked east and is over Iceland with the associated fronts tracking SE across the UK bringing more outbreaks of rain and thus suppressing the ridge. All nipping along on an impressive 150kt jet which ends slap bang over the UK

This also facilitates the next disturbance traveling quickly east and rapidly forming a little intense depression over Ireland by 18z on Saturday bringing some heavy rain and gales with it as it merges with the main low to the north. It continues to deepen quite quickly and by Sunday it is 966mb and in the North Sea, So quite an unpleasant weekend and quite cool with temps below average if this materialises.

Best left there but just to note (this will obviously be covered elsewhere) that with pressure rising in the western Atlantic Irma's route north is blocked.

 

[knocker]

The ecm much on the same page as the gfs but has a different interpretation next weekend.

At T156 it has the new disturbance running further south and is just west of Cornwall and within the circulation of the main low which is just north of Scotland. It then tracks rapidly east whilst forming an intense little depression that by 06z on Sunday is over N. Germany. This will bring some very wet, and quite windy, weather to the southern half of the UK and also France and Germany. Obviously the detail for next weekend is still to be resolved

[Summer Sun]

GEM remains consistent in the first storm of the season next Sunday a number of runs now have had a big low developing over the UK

00z

Yesterday 12z

ECM London ens shows the Op has pressure about 10mb higher than last nights run with the mean marginally lower

Last night's ens

 

[mb018538]

Just a continuation of the garbage we've had to endure for most of July and august then (barring a few recent days). Jet is on a mission this year it seems, constantly firing west to east at a rate of knots.

[phil nw.]

Actually it's not all bad news in this Atlantic pattern with something of a respite between the weather systems around mid-week.

Fax for Wednesday for example

not great but drier with some brighter weather around,maybe a few showers further north.This window probably extending into Thursday before it all goes downhill as the next low moves in.

 

[sundog]

Considering how dry the first half of the yr was ,im not surprised that the second half will overall be likely much less settled

[knocker]

There are signs on this morning's EPS means of the Iceland/UK trough weakening and drifting east whilst at the same time the Azores HP pushes north just west of the UK and also drifting east. This would portend a much more settled scenario with the temps nudging above average.

[draztik]

16 minutes ago, knocker said:

There are signs on this morning's EPS means of the Iceland/UK trough weakening and drifting east whilst at the same time the Azores HP pushes north just west of the UK and also drifting east. This would portend a much more settled scenario with the temps nudging above average.

around Mid-September?