Model Output Discussion 01/09/17

[Summer Sun]

Even at just t120 we have some differences in how low pressure will be

[knocker]

The ecm this evening has the low NW of Scotland 994mb at 12z Thursday with the fronts impacting the north west, Over the ext 24 hours these track quickly east bringing a fair bit of rain to the northern half of the UK in the process before the wind veers NW and showers are the order of the day.

The wind continues to veer northerly as the low fills in the North Sea  Some very brief ridging before the second more intense low zooms in from the west and it is 976mb just west of the Hebrides at 12z on Sunday with the fronts and rain already into the west. By midnight the low is in the North Sea east of Yorkshire Ergo a very wet day on Sunday with strong winds with gales, possibly severe in exposed places

Edited September 5, 2017 by knocker

[Summer Sun]

A wet one for the south if UKMO is right on Tuesday

 

[Summer Sun]

The ECM mean for London takes pressure from 995mb to just under 1010mb in 24hrs early next week

[David Morse]

Not really a model, but I was wondering people's thoughts on the QBO; I went through it to see which years looked similar to 2017 in the whole set and only three have a trend to easterly QBO beginning in late spring.

[Cheshire Freeze]

2 hours ago, David Morse said:

Not really a model, but I was wondering people's thoughts on the QBO; I went through it to see which years looked similar to 2017 in the whole set and only three have a trend to easterly QBO beginning in late spring.

Looks to me like the -QBO is descending at a faster rate than any of those years, with 1993 perhaps being the closest match. Also, wasn't '78 a +QBO winter? According to this it was https://www.esrl.noaa.gov/psd/data/correlation/qbo.data

 

Edited September 6, 2017 by CreweCold

[knocker]

Although there continues to be some slight differences between last night's anomalies, the precise position of the UK trough and the Azores pushing north being paramount,  the outlook for the medium term remains unsettled with temps struggling as the upper flow from the north west quadrant continues unabated. Some light at the end of the tunnel maybe apparent as towards the end of the ten day period,and into the ext, the pattern is shifting east so the Azores may well take closer order which could initiate a more settled period, albeit perhaps only effecting parts of the country to any great extent.

The more pressing matters at the moment concern the this weekend and the beginning of next week.

Today should be the best day of the week before the next low arrives NW of Scotland by 12z tomorrow  These fronts will track SR across the country as the low continues to move easy bring some rain to most areas.

Over the next couple of days the low drifts into the North Sea and the UK generally is in a showery westerly airflow which gradually veers northerly. But by 06z on Sunday the next, far more intense low 978mb is midway between Iceland and Scotland with the associated fronts already impacting the north west. Twelve hours later it is over Scotland 975mb bringing with it a fair bit of rain and quite possibly westerly gales in the southern qudrant over England.

Over the next couple of days  it drifts around in the north of the North Sea with the UK once again in a showery north westerly but the door is now ajar for other little lows to swing south east into the Uk as the jet runs around the mid Atlantic high pressure.

Edited September 6, 2017 by knocker

[mushymanrob]

6 hours ago, David Morse said:

Not really a model, but I was wondering people's thoughts on the QBO; I went through it to see which years looked similar to 2017 in the whole set and only three have a trend to easterly QBO beginning in late spring.

as i recall, there was nothing noteable about '73, although there was an early frosty spell in november.

[Summer Sun]

The main 3 for Monday

All 3 are fairly close with the depth of the low it's just its exact position they differ on

[knocker]

The ecm is taking the weekend low a tad further south. Midday Sunday has it just NW of N. Ireland 978mb ans six hours later over northern England. Thus some very wet weather on Sunday with westerly gales along the south coast likely. And then by 00 Monday it's in the North Sea east of Durham

It then slowly wanders off to the east and after a transitional ridge the next intense low arrives over Ireland by 00 Wednesday with the associated fronts impacting the west.

[Summer Sun]

Quite a difference between UKMO and ECM at D7 this morning

[mb018538]

There's so much tropical activity at the moment!

At present it doesn't look like Irma will have any direct effects on the UK, but it's still a long way off. Very unsettled for the foreseeable future. The BBC did mention the mid atlantic high pressure quietening things down next week, but I'm dubious about this myself. I can just see low pressure remaining dominant for quite a while.

[Summer Sun]

The London mean has deepened Monday's low further on the 00z

12z it was 995mb

00z it's now down to nearly 985mb

Pressure on Tuesday at 00z is about 5mb lower than the mean had last night from Tuesday onwards it looks like a steady rise in pressure with it getting close to 1020mb by the 16th

Edited September 6, 2017 by Summer Sun

[Summer Sun]

UKMO shows the Sunday's low tracking across Scotland with its centre just to the east of Aberdeen at 12z Monday it is at 978mb keeping the UK in a mainly NW'ly flow

By 12z Tuesday this low has pulled away leaving a little ridge of higher pressure so hopefully, any rain will be a bit more patchy with pressure ranging from 999mb in the far north to 1013mb in the far south west

[Summer Sun]

GEM shows warmer air and high pressure moving in from mid next week

[Ukwoody]

HI all, some guidence please. Getting a tad confused here with all the lows ,lol   . We are still expecting a sigificant low pressure on sunday, Yes?   More importantly for me, In West Wales  (Tenby area) what sort of wind/weather/sea states likely to be on sunday morning, say 10 ish please.  We have a major sporting event on (Iron Man Wales) and I'm trying to keep some of my own followers up dated as best as possible.

Many thanks for your help

Woody

[Summer Sun]

2 minutes ago, Ukwoody said:

HI all, some guidence please. Getting a tad confused here with all the lows ,lol   . We are still expecting a sigificant low pressure on sunday, Yes?   More importantly for me, In West Wales  (Tenby area) what sort of wind/weather/sea states likely to be on sunday morning, say 10 ish please.  We have a major sporting event on (Iron Man Wales) and I'm trying to keep some of my own followers up dated as best as possible.

Many thanks for your help

Woody

The met office show wind gusts between 30mph and 40mph - https://www.metoffice.gov.uk/mobile/forecast/gchtuyxvd#?date=2017-09-10

The higher res models which are free won't be showing anything for Sunday until around Friday

[Summer Sun]

ECM is taking a similar route to some of the other models with Sunday's low pulling away during Monday allowing some higher pressure to build in for Tuesday

By Wednesday we are back to a westerly flow as a deep low tracks north west of Scotland driest the further south you are and temps recovering for many away from the far north

Thursday sees the stormy conditions return as the low from Wednesday really intensifies getting down to 968mb bringing severe gales to many northern parts

Edited September 6, 2017 by Summer Sun

[knocker]

1 hour ago, Ukwoody said:

HI all, some guidence please. Getting a tad confused here with all the lows ,lol   . We are still expecting a sigificant low pressure on sunday, Yes?   More importantly for me, In West Wales  (Tenby area) what sort of wind/weather/sea states likely to be on sunday morning, say 10 ish please.  We have a major sporting event on (Iron Man Wales) and I'm trying to keep some of my own followers up dated as best as possible.

Many thanks for your help

Woody

Two things realty. I would always advise consulting the METO fot the weather in your area and Sunday morning is still a bit far away at the moment because the timing is tricky for Sunday. Taking that into account here is this evening's gfs chart for 12z Sunday and it's not great with the fronts and rain over Wales and strong westerly wind. I can't post the ecm chart but it has the fronts a little behind the gfs so you would actually be better off with this analysis as the rain would be delayed and a fairly light westerly but backing and strengthening during the morning. But the timing is crucial here that you need to check this again tomorrow.

Edited September 6, 2017 by knocker

[Ukwoody]

Knocker, thank you for that. Just to clarify I am not involved in anyway with the event and I know they do take professional advice. It's more for many of my followers who are either taking part as stewards or spectators to give them a heads up, nothing more.

woody

[knocker]

1 minute ago, Ukwoody said:

Knocker, thank you for that. Just to clarify I am not involved in anyway with the event and I know they do take professional advice. It's more for many of my followers who are either taking part as stewards or spectators to give them a heads up, nothing more.

woody

Okeydoke woody so better keep your fingers crossed as it's very knife edgy but I have to say not looking good. Will have another check tomorrow.

[knocker]

I'll keep this brief as I'm beginning to sound like a stuck record. Still differences in the medium term with the anomalies vis the orientation of the UK trough and the influence of the Azores HP in mid Atlantic where the ecm has a flatter more westerly upper flow. This will obviously impact the det. outputs so suffice it to say unsettled in this period with temps depressed but perhaps the high pressure taking closer order late in the period.

On to the here and now. today sees a cold front across the country tracking east so basically rain in the northern half of the UK and drier in the south. Tomorrow the low to the NW moves into Scotland so more wet weather there and elsewhere with fronts never far away.

Saturday midday sees the low 992mb in the North Sea leaving the UK in a showery north westerly airstream with the odd perturbation sneaking south in the western flank of the circulation. But after a very transitional ridge by 12 on Sunday the next low 977mb has arrived WNW of the Hebrides with the associated fronts and rain orientated Scotland/Wales/Cornwall with a strong westerly wind with gales in Wales and southern England, maybe even severe gale in exposed areas. Over the next 24hours the low tracks across Scotland into the North Sea thus veering the surface wind north westerly with frequent showers that will effect most areas, perhaps heavy and thundery.

A familiar story then ensues with some brief ridging before the next low and fronts arrive Tuesday evening portending some more very wet weather accompanied by gales with the strong jet running from the WNW straight over the UK

 

[Summer Sun]

ECM has a nasty low developing at t144 over North West Ireland & Northern Ireland

UKMO at the same time keeps the centre out at sea

[mountain shadow]

Certainly no Indian Summer on the cards, models look very unsettled with a continued Autumnal outlook.

Looks like a ruined grain harvest over here. 

[knocker]

@woody

this morning's update vis Sunday morning is much the same as last night and not good. The fronts and rain are hovering around west Wales and it is likely to become increasingly windy from the SW/W. The ecm still has the front a little behind but it's marginal at best. Not looking good I'm afraid