Model Output Discussion - September Onwards

[Paul_1978]

I thought the GFS was throwing up some pretty dry settled but autuminal weather. Frosty nights and warm sunny days. Maybe Im wrong.

Has anyone else noted the possible winter setup for snow in the forecoming months...

http://hw.nwstatic.co.uk/gfsimages/gfs.20110908/00/336/airpressure.png

Ahhh...Greenland high....

[Radiating Dendrite]

I thought the GFS was throwing up some pretty dry settled but autuminal weather. Frosty nights and warm sunny days. Maybe Im wrong.

Has anyone else noted the possible winter setup for snow in the forecoming months...

http://hw.nwstatic.c...airpressure.png

Yep, quite similar to last year, with a mid atlantic high linking up with one over Greenland.

I really do think this winter will be a snow fest. It just feels right!

[Weather Boy]

Much will depend on the track of ex hurricane katia. A deeper low pressure system will be better for stronger ridging... not sure what I'd rather have i.e. a storm followed by promise of a decent settled spell, or a half baked storm followed by more of what we are experiencing this week, ..

Sorry, but could you say why you think that deeper storm = stronger Hp thereafter and vice versa? I'm struggling to see the link between the two.

[Gibby]

Sorry, but could you say why you think that deeper storm = stronger Hp thereafter and vice versa? I'm struggling to see the link between the two.

Might be able to help you here.

The deeper the depression/storm is the more isobars there are surrounding it. This means to the east of the storm the added strength to a southerly flow pumps up High pressure to a greater degree and likewise Northerly flow in its wake whereas a flatter weaker system could tend to maintain the status quo in weather pattern with lesser deviations in pressure ahead and behind the Low. Of course there are other factors which can diffuse that definition but that's it in a nutshell. Hope that helps.

[Frosty.]

The Ecm 00z shows another brief warm up for the south tomorrow with temps up to 23-24c, maybe 25c for london and the warm 850's should last through saturday but turning more unsettled after a fine day on friday, scotland looks like having a prolonged spell of rain tomorrow, once again, scotland and n.ireland missing out on the warm weather tomorrow, but attention is then drawn out into the atlantic with Ex Hurricane Katia sweeping towards the uk for sunday & monday with a spell of very wet and windy weather for all areas but especially for the north. High pressure then looks like building to the west of the uk through next week as the storm system departs to the northeast and later next week it could turn more settled in southern and western areas with the good weather eventually extending to all areas as the high pushes east into the uk by days 8-10 although timings will change..so a very unsettled spell on the way and then a slow improvement during next week but temps look closer to average next week with the airflow coming in mostly from a westerly point.

[Backtrack]

Is it me, or has Katia took a severe downgrade in wind speed as it approaches the UK?

[ANYWEATHER]

Is it me, or has Katia took a severe downgrade in wind speed as it approaches the UK?

Hi Jordan, the Gfs 06z seems to upgrade the strength of the wind for Monday especially the first half of the day. Gusts well in excess of 50mph will be common place even inland. Even before then a spell of strong winds for the southern half of the Uk on Sunday togeather with some very heavy Rain......

[Paul]

Latest forecast and look at Katia from Michael Fish:

[Frosty.]

The 12z models show that tomorrow and saturday will be the last warm days for a wee while, tomorrow the south and east of england will be looking at 22-24c generally and after a rather cloudy start, the sun punching plenty of holes in the cloudsheet with maybe a sunny pm for the south & east, saturday also looks warm @ 22-23c in the east of england before a band of rain pushes in from the west bringing a drop in temperature. Scotland will be rainy tomorrow, a slow moving area of steady rain pushing north but with brighter and warmer weather spreading into southern scotland later. The weekend is looking more unsettled with rain and showers and with much stronger winds but mon/tues look particularly windy with gales or even severe gales as a vigorous depression ( remains of katia) push east across central scotland and then the low heading north, at the same time we will see an atlantic anticyclone beginning to build and this should eventually cover the uk by the second weekend although it is then likely to become unsettled once again with spells of rain and strong winds.

[bluearmy]

the noaa cpc charts from yesterday continue to look the best (from a settled perspective) than for many months. the upper trough has left our vicinity to be replaced by a very shallow ridge within a westerly flow. a surface high seems likely to become the main player, mean position centred 400miles west of scotland.

today's output is different in that the surface high is pulled west and we come under the influence of the scandi trough somewhat. this tends to fit with the post mid month scenario from the meto 30 dayer over the past week.

[Gibby]

Hi folks. here's my evening summary of the 12zs.

GFS tonight continues to show some inclement weather to come over the three days from Sunday to Tuesday. Innitially we have a couple of warm days as Southerly breezes suck sub tropical air up over the UK. Some rain in the NW but a lot of dry weather too before a band of heavy rain and squally winds runs east on Saturday bringing fresher air and strong winds with showers. On Sunday a wave depression could run across the south with more heavy rain and strong winds before the main event on Monday and Tuesday as an intense Low pressure system runs NE close to NW Scotland with gales and rain affecting all areas for a while with severe gales in the North and West causing possible disruption to travel in places. After another squally trough runs east across the UK the winds turn NW and decrease rapidly as high pressure slowly moves in from the SW. For the remainder of the run from the middle of next week sustained high pressure settles over the UK with some sunnier skies and normal temperatures although with time cloud infill could become quite extensive as air is drawn around the high and over Britain from the Atlantic.

UKMO shows a similar time scale to events and although doesn't show the depth of Low pressure to the NW early next week its longevity seems to stretch towards the middle of next week as the model is less keen to bring the strength of high pressure up from the SW in the timescale of the run.

ECM follows UKMO quite closely although the storm system on Monday is further south over the mainland of Scotland delivering severe gales on its Southern flank, strongest on this run over Northern England and North Wales once more with the risk of traffic and travel disruption very high for all areas. As well as wind there would be heavy rain and showers at times driven along quickly in the wind. Then as per UKMO its Wednesday before pressure rises to enough of a degree to bring dry conditions as a ridge of high pressure slides into Southern Britain on Thursday. In the final days the high pressure ridge is pulled away South as renewed Low pressure from the NW proceeds SE.

We still have a big blow on our hands late in the weekend and early next week with some inclement and possibly severe conditions likely locally so listen to weather bulletins closer to the time for details on affected areas and timings. In addition to the wind heavy rain and showers would also accompany these conditions at times. From Wednesday of next week things do calm down with high pressure taking control if GFS is to be believed with variable sometimes large amounts of cloud and temperatures close to average. In ECM's latter end of the run the High pressure is held further South and Southwest allowing further Atlantic developments to maintain changeable conditions at least for Northern areas at least towards the second weekend.

[Geordiesnow]

This afternoons output indicates that after the reminisents of Katia heads into Scandi it pulls up an Azores ridge behind it which in turns leave the UK in a Northerly airstream which is quite strong on some runs but the uppers are not the coolest in the world however it will be the first time in the Autumn season where sustained uppers of 0C or below would of entered the UK, no chance of snow but as the high ridges in, chances of ground frosts increases so signs of Autumn in the outlook in terms of both winds and temperatures in this afternoon's outputs.

[mushymanrob]

this mornings runs have decreased the possible settled weather progged for mid next week, gone is the ridge that was expected to build to our west following the stormy weekend/early next week.. its now expected to be pushed further south by a flat jet.. so a continuation of this splendid autumn weather continues!

[casparjack]

this mornings runs have decreased the possible settled weather progged for mid next week, gone is the ridge that was expected to build to our west following the stormy weekend/early next week.. its now expected to be pushed further south by a flat jet.. so a continuation of this splendid autumn weather continues!

No surprise there then! The charts look virtually the same as they've looked since early May from a very broad perspective...

[Gibby]

A little late today but here's my view of the 00zs of the big three.

GFS this morning shows little change from the pattern shown yesterday with regard to the storm system late in the weekend and early next week. So the current warm, muggy drizzly and cloudy weather will give way to brighter weather for a while before winds start to freshen from the South the SW over the next 24 hours. A cold front crosses east over Saturday with a band of rain followed by fresher, windy weather with some showers or longer spells of rain on Sunday. Overnight and through Monday and Tuesday severe gales can be expected in the North and West with travel disruption possible due to tree debris as they are still in full leaf at the moment. Some heavy rain and showers will also accentuate conditions for most areas. From midweek though high pressure gradually replaces the wind and rain first in the SW then extending to other areas before the weather slowly deteriorates again from the Atlantic towards the end of FI.

UKMO follows a similar route but is less keen to bring high pressure in next week instead supports the evolution of a ridge crossing east on Thursday ahead of further Atlantic depressions late next week.

The Fax Charts show a very windy period to come with some heavy rain too for most. Post Katia is shown to cross close to or over Northern Scotland on Monday with secondary Low pressure dragging behind delaying any marked improvement until the middle of next week.

ECM also follows the UKMO route with a similar route for the Monday storm and the sequence of weather events as per GFS. From midweek on pressure has risen in response to High pressure to the SW with the South and West becoming dry while the North and Northeast remain breezy and cloudy with a little rain. Late in the week and through the weekend the unsettled weather slowly digs further south through the UK so that by the end of the run we are back to Low pressure to the North pushing rain bearing troughs with wind and rain at times for all areas.

It seems that the models have a very good degree of confidence now of the rough path of the Storm on Monday. It looks like all areas will experience gales (severe in the North and West) with some fast moving bands of rain and showers for all at some point. In the longer term GFS is a little more hesitant with its high pressure pattern shown last night as the Atlantic looks a little more active this morning. ECM too suggests a short improvement at least in the south later next week but also shows a deterioration back into an unsettled pattern by next weekend.

[minus 9]

A quick question. Are 850 temps the temperature at 850 meters. Sorry if its a bit off topic.

[grab my graupel]

A quick question. Are 850 temps the temperature at 850 meters. Sorry if its a bit off topic.

Here you go :

[georgiedre]

where is the model runs on netweather now? i cant view the charts!!

[minus 9]

Cheers gmg

[grab my graupel]

where is the model runs on netweather now? i cant view the charts!!

http://www.netweather.tv/index.cgi?action=nwdc;sess=

[georgiedre]

thank you..

[Simonl]

Not sure about that, IF this suggested ridge develops as nicely as some evolutions suggest is possible for later next week, that could feel pretty mellow and fruitful for a fair few of us!

To use a non meteorological term, we're overdue another spell of proper High Pressure dominated conditions. Owed it even!

I think the same.....Hopefully we are due and odds in favour of a more high pressure dominated scene from mid-month onwards - the signs are certainly there! Would be ironic if azores high were to set up camp across our fair land now...lol!

[summer blizzard]

I personally see little change in the models from the dominant summer pattern.

Once we get Katia out of the way, we see the winds turning north to north westerly before a ridge attempts to build and the next low comes in.

All in all, its Autumn and i find little reason to think that the GFS will be right about ridging.

[Iceni]

Another question (Sorreeee) I'm trying to find the Stratosphere Watch thread to find out what it's doing atm. All the search does is to direct me to lots of other threads.

[Mark Bayley]

Another question (Sorreeee) I'm trying to find the Stratosphere Watch thread to find out what it's doing atm. All the search does is to direct me to lots of other threads.

http://forum.netweather.tv/topic/64621-stratosphere-temperature-watch/page__st__500

Although monitoring only really starts in November