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phil nw.

Model Output Discussions 12z 01/09/2016

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Bit of toing and froing from the models over how much influence the persistent ridge over central Europe will have on the UK against an rather active jet roaring across the Atlantic toward NW UK. The Euro ridge relaxes from Thursday and through this coming weekend to allow a succession of low pressure systems to brush NW UK and bring cooler/fresher conditions, wet and windy conditions in the NW from Thursday and rain for all by the weekend. 

But model uncertainty grows next week over whether the Euro ridge gains more influence across S/SE UK next week, returning summer warmth as per 00z EC op or whether Atlantic upper trough will be the dominant force across the UK as per 00z GFS op.

ec+gfs_00z.gif

00z EPS and GEFS 500mb mean/anomalies for  Wednesday next week indicates trough disruption off SW Europe, which indicates Atlantic trough being pushed back by the Euro ridge, so 00z GFS op maybe a little over-progressive in pushing in Atlantic trough axis across the UK

ecmwf-ens_z500a_nhem_9.pnggfs-ens_z500a_nhem_33.png

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Next week starts with a huge contrast in temps between England and Wales to those in Scotland, Northern Ireland, and the ROI

ukmaxtemp.png

After Monday parts of the south & SE really begins to heat up with temps getting into the high 20's possibly into the low 30's

ukmaxtemp.pngukmaxtemp.png

By the Thursday the heat spreads further north with the mid 20's as far as NE England the rain and fresher temps in the west mark the start of the breakdown

ukmaxtemp.pngukprec.png

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Need slight shift NW, SS, then we have it again! mini 'plume' /warm spike timed for Tue to Thur period, then no doubt rubbish by Fri

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2 minutes ago, I remember Atlantic 252 said:

Need slight shift NW, SS, then we have it again! mini 'plume' /warm spike timed for Tue to Thur period, then no doubt rubbish by Fri

Guess what...

ukmaxtemp.pngukprec.png

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The GFS going along with trough disrution next week and the cut off upper low. Ergo large slack unstable low pressure area to the south tracking slowly north, Wearm and thundery could be the order of the day but we shall see,

gfs_z500a_natl_32.pnggfs_6hr_precip_eur3_31.pnggfs_6hr_precip_eur3_36.png

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Need to keep an eye on the Sunday low. Could bring some quite strong winds to Scotland.

ecm_mslp_uv850_natl_6.png

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The general idea from ECM tonight for next week is warm to very warm Monday to Thursday especially so for England and Wales then fresher air moving in from the west by Friday with any remaining warmth in the SE

Recm1442.gifRecm1682.gifRecm1922.gifRecm2162.gifRecm2402.gif

Edited by Summer Sun
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14 minutes ago, Summer Sun said:

The general idea from ECM tonight for next week is warm to very warm Monday to Thursday especially so for England and Wales then fresher air moving in from the west by Friday with any remaining warmth in the SE

 

I have to say that's a very generous interpretation SS.:)

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Today

Dry and sunny for most depending on the cloud clearing which is most likely in central, southern and eastern England. Here it will get quite warm. cooler with some rain in northern Scotland.

ens_mean1hrprecip_43.pngens_max2mtemp_22.png

Last night's anomalies didn't indicate trough disruption next week that would impact adversely on the southern half of the UK and this morning's GFS det. run is going along with, but to start a tad earlier.

Friday see the next depression follow a familiar easterly track before swinging NE the N and phasing in with the other low Iceland area, The front associated with this will quickly traverse the UK on Saturday. This is quickly followed by another low running a similar track which could well bring some adverse weather the the NW late Sunday/early Monday.

The front associated with this system tends to fizzle out and this is where the trough disruption occurs but the resulting cut off upper low is too far south and ridging HP may well forestall any northward transport of unstable weather from Spain.This still a fair way from being nailed down.

So the remaining of next week is the classic N/S split with the south continuing dry and temps perhaps a little above normal but again probably just in the south.

gfs_6hr_precip_eur3_13.pnggfs_6hr_precip_eur3_21.pnggfs_z500a_natl_32.png

gfs_tprecip_uk2_41.png

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I'd go along with that. The tropical disruptions are still playing havoc and adding some real firepower to the Jetstream. Possibility of another muggy day or two down south next week as some more of this air is scooped up, but generally not too much rain in the SE, with a fair bit in the NW.

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The theme of the ecm is similar to the GFS if not the detail. Depressions fortunately tracking far enough NE not to impact too severely on the NW and then the trough disruption but the cut off upper low is away to the SW,so it is indeed cut off, allowing HP to build over the southern half of the UK.

ecm_z500a_5d_natl_11.png

Edited by knocker

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Whilst ECM has lost the real heat of previous runs it's an improvement in general with high pressure for more areas for the south we should still see temps around the mid 20's with ample sunshine

Recm1201.gifRecm1441.gifRecm1681.gifRecm1921.gifRecm2161.gif

Oh and the breakdown? yep, you guessed it....

Recm2401.gif

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As the 500mb anomaly charts are not in agreement for more than 1 day at any time then I am at the 'sit on fence' period-sorry

 

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Looking at some of the latest outputs we can see this lovely extension to the August warmth  will become increasingly restricted to the far south after today as Atlantic systems become more influential across the country over the next 3/4 days.

The weekend sees a noticeable change as rain and fresher weather moves right across the country.

sat rain.png

Next week then does look more changeable and indeed we could say unsettled for the much of Scotland/N.Ireland and at times N.England as further low pressure tracks north east towards Iceland.

Something less mobile seems likely further south as positive heights,extending from the Azores eastwards towards the continent,promise to keep areas further south much drier with low rainfall totals expected-after the rain over Saturday/early Sunday.

Comparing 2 graphs -Argyle and London from the 06z ens run

argyle.pnglondon..png

we can see the rain spikes on the Scottish graph where the active fronts come in whereas further south east little rainfall is shown indicating any rain bearing fronts coming south east will likely be much weaker or simply die out.

The day 10 ens graphs 

gens-21-1-240.pngEDM1-240.gif

so based on the above we are looking again at the warmest and driest conditions for the midlands south next week,although with a natural cooling off somewhat,as we should expect heading towards mid-September.

Edited by phil nw.
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Out of interest did any models predict this for my location Gravesend- the bbc and other apps always have us a degree or 2 down on London but we're nearly always warmer!

Screenshot_20160907-162832.png

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A wet start to next week for some western and northern parts temps for many in the high teens or low 20's possibly the mid 20's in the SE

ukmaxtemp.pngukprec.png

Into Tuesday the showers are a bit more widespread during the morning at the heat builds for the south and SE

ukmaxtemp.pngukprec.png

Wednesday is a drier day for the south and another hot one with highs into the low 30's

ukmaxtemp.pngukprec.png

Into Thursday and the heat continues for the SE with highs close to 30c again the warmth also extends up towards the Humber fresher in the west turning wet from the west

ukmaxtemp.pngukprec.png

By Friday the fresher air is UK wide with the last of the rain slowly clearing the SE

ukmaxtemp.pngukprec.png

UKMO to start next week

Rukm1201.gifRukm1441.gif

 

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The GFS this evening is still running the quite deep depression NE late Sunday early Monday, with the upper trough running a fair way south, bringing some inclement weather to the north Thereafter the trough disrupts leading to cut off upper low to the SW which facilitates a slack surface low pressure area to the south of the UK which drifts north which with some quite marked air mass boundaries could be quite interesting . But hey this is days away.

gfs_6hr_precip_eur3_20.pnggfs_z500a_natl_25.pnggfs_z500a_natl_32.png

gfs_6hr_precip_eur3_31.png

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ECM is more favourable for settled conditions more widely mid next week

ECM left GFS right

ECM1-168.GIF?07-0gfs-0-168.png?12

ECM1-192.GIF?07-0gfs-0-192.png?12

The southerly flow sends the 850's right up by Thursday

ECU0-192.GIF?07-0

Edited by Summer Sun
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The ecm also going for trough disruption at the beginning of the week but crucially the upper trough stretches much further south resulting in the cut off low being just west of Portugal. Ergo all the low pressure activity is further south and allows HP to build briefly over the UK until towards the end of the run the upper trough once again gets more organised becoming negatively tilted just to the west of the UK dragging the convective activity north.

ecm_t850_uv_natl_8.pngecm_z500_anom_natl_8.png

Edited by knocker
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Well this is most peculiar; UKMO and GFS consolidate the disturbances from the Atlantic into a single well-defined low pressure system for 12z Monday, yet ECM (right-hand chart) is having none of it, choosing to distribute the disturbances along a trailing frontal boundary:

Rukm1201.gif  h850t850eu.png ecmt850.120.png

GEM displays similar behaviour to ECM, and the knock-on effect in both cases is to develop the cut-off low further west - quite a bit further west in fact;

h850t850eu.png ecmt850.144.png

UKMO actually has the low just south of the UK at this time, but it seems to be a bit away from the main pack in terms of solutions being put forward this evening.

The effects on the potential plume are not hard to guess;

h850t850eu.png  ecmt850.192.png

GFS has shunted it east of much of the UK by the time it makes a strong push north, while ECM has it scoring a direct hit on England and Wales.

This is what, the fifth or maybe sixth plume of the astronomical summer? So we're some way past third time lucky, but you never know with these things :D

By the way - a rough estimate using the GFS 12z 2m temp data for my area of England (western edge of New Forest - so not the CET region, I must make clear!) has Sep 2016 around half a degree ahead of Sep 2006 as we pass the mid-month point, which implies that ECM would have my locality soaring above it. Just to drive home how exceptional the conditions that ECM shows are in the context of having already had a run of several well above average days in the month.

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ECM once again shows warm to very warm conditions next week possibly close to hot in the south at times

Recm1202.gifRecm1442.gifRecm1682.gifRecm1922.gif

By Friday the last of the heat leaves the east as lower pressure attempts to move in this probably affecting the north greatest

Recm2162.gifRecm2402.gif

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Well I still feel the general idea of the stalled trough against euro heights is a bit weak - UKMO certainly in mind - but as the ECM has been so consistent you can't really ignore it. Warmest first half of September ever surely wouldn't be far off if ECM/GFS is right. Need the right set-up to keep the clouds away, though - keep those winds east of SSW.

Also the extent of warmth for next week debatable as yet - ECM surely best case scenario.

It's becoming a bit of a stuck record, not only the pattern but the days of the week it falls on!!

Edited by Man With Beard
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