Model Output Discussion - September Onwards

[Gibby]

Good evenng.

GFS tonight shows deep Low pressure moving in close to Northern Scotland on Tuesday and Wednesday with a strong westerly flow over the UK. A band of rain on a cold front crosses east through the UK on Tuesday replacing the showers of Monday. Wednesday would be showery while Thursday sees winds decrease as the Low moves away North. However a further trough brings another wet day on Thursday before a more substantial rise of pressure takes place from the SW on Friday. This brings a transient dry day or two before a warm front on Sunday brings a band of rain NE and introduces warm and humid conditions once more. In FI tonight a North/South split takes place with the North seeing more rain at times while the south have mostly dry conditions in rather cloudy and humid conditions before Low pressure feeds back over all areas at the end of the run.

UKMO tonight shows a breezy week coming up with a period of very windy weather midweek. After sunshine and showers tomorrow a trough will bring a marked band of rain east through all areas Tuesday. Wednesday will be a showery day with most of the showers in the North. On Thursday a warm front moves NE through the UK bringing a further band of rain followed by a broad warm sector with hill fog and drizzle extensive on coasts and hills in the west and North late in the run. The SE could see some bright and very warm intervals around Saturday as Low pressure moves in slowly to western regions bringing some potentially thundery rain slowly east with time.

ECM also follows the same pattern as UKMO with strong winds and rain Tuesday before slow improvements take shape on Wednesday in the shape of cool NW winds and showers. A ridge of high pressure then crosses east on Thursday with a warm front moving up its western flank delivering rain and drizzle as it goes leaving the end of the day dull and misty near all south and west facing coasts and hills. On Friday and through the weekend the cloud would break up over the SE with some very warm sunshine breaking through though the North and West would remain more cloudy and uninspiring. The run then ends with deep Low pressure to the west with continuing warmth for the SE and rain in more Northern and Western areas before rain extends east at the end..

The outlook tonight looks rather mixed with rain and windy conditions dominant this week. There are fairly strong signals now for things to improve for the SE next weekend and beyond with some warm and humid conditions looking possible to develop while the further North and West one goes any improvements will be shortlived.

[conor123]

Both the GFS and ECM have an attempt at a warmup come next weekend, the ECM in particular although the UKMO is having none of it.

The ECM in particular looks promising for a humid summery plume of some kind and if Hurricane Katia keeps getting progged further north then the warm weather would continue although still far away yet.

[mushymanrob]

i love it! a right mixed autumnal bag on offer this week, never too cold, but plenty of variety in a warmish mobile atlantic regime.

[Gibby]

Good morning.

GFS this morning shows a very windy spell for tomorrow and especially Wednesday over Scotland with westerly gales and squally showers after a band of persistant rain sweeps east tomorrow. Later in the week the weather remains unsettled with a small Low pressure area moving NE across England on Saturday bringing more rain with it. By Sunday and Monday pressure rises towards the SE with warm and humid conditions developing here though with a lot of cloud. Further North and West cloud and breezy conditions will continue to give occasional rain. In FI today High pressure lies to the SW though too far away to have total control of the weather even in the South. True a lot of dry weather would occur but occasional troughs would bring rain now and again. Further North the unsettled weather continues unabated with wind and rain never far away.

UKMO today looks unsettled throughout with a wet day for many tomorrow as an active and deep depression moves into Northern Scotland. More showery conditions will sweep east by Wednesday and through Thursday with most of the showers in the North and West with strong winds everywhere. On Friday a warm front moves NE in the continuing breezy SW winds with rain and humid conditions moving NE through all areas. On Saturday a band of rain on a cold front moves east through the UK followed by a weak ridge on Sunday giving a temporary respite from the unsettled theme.

The Fax Charts today show a deep Low pressure moving North of the UK with troughs sweeping east tomorrow. Later in the week a broad warm sector brings rain followed by humid and cloudy conditions with rain restricted to the NW for a while with much hill and coastal fog and drizzle in the west and North.

ECM today shows winds blowing from a Westerly quadrant throughout the entire run with troughs moving through from time to time in the brisk winds. The South and East will see the best of any dry, bright conditions as ridges of high pressure cross but even here rain will occur from time to time. Temperatures will be fairly normal for September and it could become rather warm feeling in the SE at times as very warm air over the Continent infiltrates over the SE at times.

In Summary today it looks typical early Autumn Fayre with the Atlantic very active pushing depressions and troughs east towards us at regular intervals. The least rain and wind will always be towards the east and SE while the North and West could be very wet at times. Temperatures look like being normal for most but rather warm in the SE at times. A fairly windy week to 10 days looks likely everywhere.

Edited September 5, 2011 by Gibby

[Methuselah]

Thanks for the update, Gibby.

[Isolated Frost]

Overall, another interchangeable run, with cooler 5C uppers around the UK, apart from the South, and up to 15C uppers on Thursday evening again, with persistant cloud, wind and humidity - however, ex-Katia is making an appearance on every run and getting closer, 948mb on this chart, 150 hours in the future.

[Stormyking]

Is it me or does GFS 06z show an indian summer towards FI, some warm looking charts from what I can see. In the meantime some very unsettled weather by the look of it, especially tomorrow with risk of gales! Wouldn't mind a bit of that

[Jack Wales]

Is it me or does GFS 06z show an indian summer towards FI, some warm looking charts from what I can see.

GFS has been throwing up those charts in FI since June!! I wouldn't read too much into them as the flow looks very mobile for the forseable future.

[shedhead]

GFS has been throwing up those charts in FI since June!! I wouldn't read too much into them as the flow looks very mobile for the forseable future.

Agree this has been the case all Summer, but I still expect Sept to turn out dry, warm and sunny overall... .we just need to get over this shorter term blip.

[Stormyking]

GFS has been throwing up those charts in FI since June!! I wouldn't read too much into them as the flow looks very mobile for the forseable future.

I know I was just saying, im more looking forward to tomorrows weather, GFS showing gales

[The PIT]

Interesting run briefly windy Tuesday suppressed day time temps but holding up very well by night before coming warm over England. Back to more normal temps then the remains of a hurricane well into FI the exact track of which will be important. If it's further west than shown could well throw up a warm ridge across the country further east wet and mild.

[Gibby]

Good evening.

GFS shows Low pressure North of Scotland dominating the weather over the next few days with gales and rain followed by showers the order of events. By Thursday a broad SW flow blows over the UK with a warm front crossing NE with rain followed by breezy and mild conditions with hill and coastal fog widespread. Low pressure then moves NE over England on Saturday bringing a spell of quite heavy rain with brighter but still breezy conditions following on Sunday. Through FI the weather remains Atlantic based but with High Pressure controlling the weather at times in much lighter winds there would be some lengthy drier spells but with some rain at times for all least in the south.

UKMO tonight looks like maintaining unsettled conditions through to the end of the run with a deep Low pressure moving close to Northern Scotland tomorrow before moving slowly NNE on Wednesday. A wet start for many tomorrow before a change to squally weather with showers especially in the west. On Thursday a warm front brings quite a wet spell before warm, humid, cloudy and still breezy conditions follow. From Friday through to Sunday the weather continues breezy but quite warm with outbreaks of rain continuing, especially in the North and West gradually spreading further east to most areas over the weekend.

ECM looks distinctly unsettled tonight. Deep Low pressure gives wet periods late tonight and tomorrow morning and again on Thursday with bright intervals and showers at other times. Winds will be strong making it feel cool out and about. By Friday a ridge runs across the UK before warm and moist SW winds take control over the weekend with rain in the North and West and for a while elsewhere first thing on Saturday. Then a further spell of rain and potential gales cross the UK next Monday with a further transient ridge moving quickly east behind it next Tuesday to leave the end of the run with Low pressure over the UK with wind and rain for all.

In Summary Autumn is setting in quickly at the moment with charts more akin to early October. Over the next few weeks there looks like several spells of strong winds and rain with relatively warm temperatures at times in the South. The earlier rise in pressure is held back until Monday now from GFS and has all but disappeared from ECM with any rise in pressure relegated to transient ridges between depressions. UKMO who has not as yet showed interest in showing any meaningful rise of pressure at all at the weekend continues to look unsettled and breezy though rather warm.

[Fozfoster]

Good summary again Gibby, more than could be said for the up and coming week, in my eyes anyway.

[damianslaw]

Its very quiet in this thread at the moment. I would have thought now September has started it would have stirred into action a little.. alas perhaps its the uninspiring outlook giving reason to such few posts.

Back to the charts, well all three major models - GFS, ECM and UKMO agree that this week will see a disturbed atlantic driven pattern reign supreme. Charts which wouldn't look out of place in late october/early november, but are a little too disturbed for my liking for early-mid September. For the northwest quarter of the country it certainly looks like a rain fest for the next few days, I am already expecting this month to go down as a wet one here.. On Thursday we will see a warm sector move up from the SW with associated warm front, this will give heavy rain to many sw parts and wales.

The weekend at this stage looks like a classic NW-SE split, the NW holding onto the wind, rain and cloud, the SE seeing the brightness and warmth.

Longer term - slight differences between GFS and ECM, the former building some stronger ridging of heights ahead of ex hurrican katia, much like we saw at the back of last week with ex hurricane irene. ECM very much keen on short temporary ridging with low pressure taking a more southerly path on a collision with the UK. Remains to be seen what will happen, ex hurricanes have a habit of doing very strange things, taking sudden u-turn paths. I do believe this autumn will see a very unsettled atlantic thanks to the colder than normal SST's over the mid north atlantic which will help aid the development of strong low pressure systems thanks to steeper than usual temp gradients. We have had a run of remarkably quiet autumns, or only shortlived unsettled spells, its about time an unsettled one came along.

[Thundery wintry showers]

NOAA longer-term outlooks have consistently placed low pressure there or thereabouts for mid-September, though with disagreement on the positioning of the mean trough, and the latest update has started to U-turn with high pressure near to the south:

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

The MJO signal is currently very weak, so I can't read much from the MJO signal at present.

Until today the odds appeared to strongly favour a changeable westerly-dominated September, with a warmer blip for south-eastern areas in the second week as we pick up a south-westerly (note that the SW regime will bring cloudier wet weather to most of the west though). However, the latest signals suggest that high pressure ridging may occur for rather longer.

[Cheese Rice]

Friday looks of interest for some hot weather. A pool of 15.c 850's amidst 10.c 850's. Providing the low even exists and is further west and north we could see a very warm day with temperatures in the mid twenties.

Edited September 5, 2011 by Cheese Rice

[mushymanrob]

Agree this has been the case all Summer, but I still expect Sept to turn out dry, warm and sunny overall... .we just need to get over this shorter term blip.

i dont, i cant see any tangible signs that this curret pattern will change soon, indeed the models quickly bring on another deep low early next week. i dont think theres any hope of things settling down within ten days, and thatll effectively 'write off' half of september for anything 'summer like'. (bar the odd day here and there esp for the south/east). im sure there will be a settled spell sometime in the next few weeks, but the orientation of any high will have a major impact on whether its 'summer like' or cool misty autumnal..

[Gibby]

Good morning. Here is a look at the 00zs of GFS, UKMO and ECM.

GFS today shows a very windy week to come. Without the need to go into specific detail this morning winds will always between SW and NW as deep or very deep low pressure is never too far away from the North or NW of the UK with showers or longer spells of rain for all areas at times over the next 7 days. Temperatures will be near or occasionally above normal in the South tempered in feel by the wind. In FI a complete change around in the weather is shown as High pressure builds from the SW with High pressure centred close to the UK with fine weather by day and mist and fog at night.

UKMO this morning shows unsettled conditions lasting throughout its run with a strong west or SW flow for all throughout. There would be rain at times too, heaviest and most persistant in the North and West but certainly some in the south and east too. Temperatures would be near normal but warm and humid at times in the south especially at the start of the weekend.

The Fax Charts mirrors the raw data for the most part though some updates are not shown this morning on my browser.

ECM looks a little more optimistic this morning but only in the long term. The unsettled theme progged by the others is replicated by ECM today with strong winds, rain at times and cloudy skies the main players of the weather in the next 7 days. Later in the run though as per GFS pressure rises from the SW with dry weather taking control by the end of the run though cloud cover would remain extensive with a feed of air around the High to the SW from off the Atlantic.

In Summary there is an Autumnal look about the charts for the next week or so with plenty of rain and wind for most. Later in the runs of GFS and ECM high pressure builds from the SW bringing a drier spell with sunshine by day and mist and fog overnight though if the High remains to the SW as per ECM cloud cover would remain dominant.

[Ja23]

What's peoples thoughts of that big low around 144 hours? Will it come near us? Or just miss us. Appearing on all main models at the moment but some disagreement over how strong it will be and where it will go.

[Radiating Dendrite]

What's peoples thoughts of that big low around 144 hours? Will it come near us? Or just miss us. Appearing on all main models at the moment but some disagreement over how strong it will be and where it will go.

That big low is actually Huricane Katie (well what will be left of her).

The GFS does tend to over develop these type of features, but if it did hit us it xould still bring heavy rain and gales (maybe even severe gales).

[Ladyofthestorm]

Hmmm the thing is will that very deep area of ex hurricane Katia take a more Sly route (and intensify) or take a more Nly route and fizzle out.

The GFS has stuck to its guns on this one for about 6 days... quite impressive if it pulls this one off. It wouldnt surprise me if it did to be honest, given how atlantic dominated our weather is right now.

I bet Cookie and Milkmaid will be warned, it could touch stormforce for a while over the exposed outer hebrides. OMG Ive just seen sunshine.

[Ja23]

06z has moved it further North just by a bit with a slight downgrade.

[summer blizzard]

The models have downgraded the warmth quite significantly. Rather than coming from ridges and approaching +15C in the upper atmosphere, the warmth is now associated with warm fronts and low pressure which will in the main provide cloud and high minima.

The models are strugling with Hurricane Katia as it has strengthened more than predicted and is a FISH.

[The PIT]

GFS loving Katia all the way now moving closer to us and giving as a very windy period. Expect this low to move around a lot. I think the Bamm model had it going up the Bristol channel yesterday. Worth checking the hurricane thread for progress as how this hurricane acts will have effect on the GFS modelling.

[Fozfoster]

summer blizzard, on 06 September 2011 - 17:44 , said:

The models have downgraded the warmth quite significantly. Rather than coming from ridges and approaching +15C in the upper atmosphere, the warmth is now associated with warm fronts and low pressure which will in the main provide cloud and high minima.

The models are strugling with Hurricane Katia as it has strengthened more than predicted and is a FISH.

Sorry, but " FISH". What does this mean? apart from the freshwater type. Cheers