Model output discussion - summer rolls on

[Frosty.]

I see a north / south split next week with the jet stream mostly affecting scotland where it looks generally cool and changeable / unsettled whereas further south, especially the southern half of england and wales should have plenty of high pressure / ridging and a good chance of tapping into continental warmth, at least for a time towards / during the  next midweek period with temps potentially into the mid 20's celsius, possibly higher further s / se.

Tonight's Ecm 12z ensemble mean supports some very warm settled weather further south next week.☺

Edited September 6, 2018 by Frosty.

[mb018538]

Not one model post today! Must be the time of year!

A quick summary for those wanting one...

Huge uncertainty due to the triple threat of hurricane Florence, & disturbance 1 & 2 which both look likely to form into tropical cyclones.



Ensembles are a mess too. It's a day by day story at the moment, better the furhter south and east, and a bit warmer into early next week in the south.

ECM ensembles staying westerly at day 10, with the slightly warmer option favoured.

Edited September 7, 2018 by mb018538

[Frosty.]

There's plenty to suggest from the GEFS 6z mean that we are looking at a predominantly north / south split during the next 2 + weeks with frequent ridging  / high pressure across the south bringing a good deal of fine pleasantly warm weather with potential for it to be very warm at times further s / se and generally cooler and more changeable / unsettled the further n / nw you are. There would be some chilly nights where winds fall light and skies clear with a risk of mist / fog patches. ☺

Edited September 7, 2018 by Frosty.

[Frosty.]

Looking at the Ukmo 12z southern uk has plenty of fine and warm weather to look forward to well into next week thanks to strong ridging and potentially becoming very warm / hot across the s / se for a time with +15 / 16 850's from the near continent flirting with the SE @ T+144 hours!☺

[I remember Atlantic 252]

bbc said that Frosty, but GFS not good, washout and 13 degrees on Tuesday, wet wednesday, wet thursday

[mb018538]

It’s still a predominantly westerly flow, so I’d say 26-28c max maybe in that set up...which is still cracking for mid September. It’s all very knife edge, the southern UK looks like being the heat boundary, it’s just how far north the warmth  can make it from the continent.

Edited September 7, 2018 by mb018538

[Frosty.]

I've mentioned north / south split a lot recently and this also applies to the GEFS 12z mean, predominantly  fine and warm weather further south with plenty of ridging.. generally cooler and more changeable / unsettled further north by northwest.

 

[ANYWEATHER]

Evening ! A Changeable to unsettled outlook looks likely from both models ,yes some warmth in the south for a time this week,but fades away quickly from the Northwest. If I would put any money on a model GFS seems the most consistent..... Keep youre eyes on some very wet and windy weather by late next week

[Singularity]

ECM playing with the idea of bringing a son-of-Ophelia... that'd be quite something to have two such intense hurricanes so far (indeed, record-breakingly far) north and east, two years running. SST anomalies indicate that it could be done if the storm was to take such a track - but it's way too far out to consider this seriously at the moment.

That aside, the impacts of the Arctic sea ice on the N. Hemisphere cold air distribution is catching my eye already; there's an unusually intense focusing around Greenland/NE Canada as the usual polar vortex-friendly Arctic ocean is still too 'warm' what with all the extra open ocean around. 

This could lead to more ridging from the southwest than usual for a Nina-like atmospheric state, much as we saw May-June this year, but on the other hand, seasonal differences to back then may allow the Atlantic storms to come raging on in across at least the northwest of the UK.

I sense that we're going to need some strong attacks on the vortex to prevent it dominating proceedings from that position to our NW (be that via downstream ridges or troughs firing across us) in the coming months.

[mb018538]

It usually sets up residence in that locale in the majority of our winters, so it wouldn’t surprise me one jot if it does again! What is interesting is the effect that the record breaking June and July in the north of Europe had on ssts to our N/NE and how that will feed back into global cycles. I haven’t a clue, but it’s a long way from normal, so time will tell.

They are still well above this week: 

[JBMWeatherForever]

I note what has been said about the possible impacts of the Artic Sea Ice on the Northern Hemisphere cold air distribution, but will this be as big a factor for this year, as I see the artic sea ice extent is now back within the standard deviation of the 1981 - 2010 average ? 

[mb018538]

5 minutes ago, JBMWeatherForever said:

I note what has been said about the possible impacts of the Artic Sea Ice on the Northern Hemisphere cold air distribution, but will this be as big a factor for this year, as I see the artic sea ice extent is now back within the standard deviation of the 1981 - 2010 average ? 

Not sure where you are getting that information from - Arctic sea ice is well below normal, and even out of the interdecile range at the moment.

Edited September 8, 2018 by mb018538

[Newberryone]

Latest overnight run from the Ecm would certainly seem to suggest a far less unsettled latter stage compared to the previous run with heights to the south continuing to dominate. Any Atlantic influence really only being felt to the far off northwest and even here nothing overly unsettled. The run even manages to end on an all time high...Sorry ANYWEATHER!! 

[JBMWeatherForever]

The Artic Sea Ice extent seems to be back within the standard 1981- 2010 average deviation in the graph I am looking at https://nsidc.org/data/seaice_index 

The question I was raising was therefore whether the sea ice melt would indeed have as much of an effect this winter on the northern hemisphere cold air distribution. Some effect, Yes certainly, but more effect this year than previous ?  

[johnholmes]

1 hour ago, Newberryone said:

Latest overnight run from the Ecm would certainly seem to suggest a far less unsettled latter stage compared to the previous run with heights to the south continuing to dominate. Any Atlantic influence really only being felt to the far off northwest and even here nothing overly unsettled. The run even manages to end on an all time high...Sorry ANYWEATHER!! 

The fact that the two runs differ suggests a degree of uncertainty to me. So best not to get your hopes up too high just yet?

The 500 mb anomaly charts have, over the past 3-4 days been fairly consistent in their pattern suggestion, see links below. A 500 mb flow light enough for the far south for the probability of 24-48 hours of sufficient ridging from Europe to allow a more settled pattern away from the NW of the UK. This in the 6-14 day time scale.

Well that is my take on things.

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

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

[oasis]

1 hour ago, JBMWeatherForever said:

The Artic Sea Ice extent seems to be back within the standard 1981- 2010 average deviation in the graph I am looking at https://nsidc.org/data/seaice_index 

The question I was raising was therefore whether the sea ice melt would indeed have as much of an effect this winter on the northern hemisphere cold air distribution. Some effect, Yes certainly, but more effect this year than previous ?  

Hello. Yes, it does seem a bit higher, though not by a massive amount. Also, from what I've read recently, the amount of ice is still very low on our side of the Arctic. So, around Svalbard etc. So I'm not sure that this increased amount will have much effect on autumnal/winter weather patterns.

Ie, to keep on topic, charts for the next week have the jet stream passing just to the north of Scotland and leaving the south of England untouched. Which could be linked to lack of sea ice. 

[mb018538]

Pattern looks flat really - though as an ex- tropical system heads out way for mid month, we could either get howling gales or a couple of days of heat.

[Interitus]

3 hours ago, JBMWeatherForever said:

The Artic Sea Ice extent seems to be back within the standard 1981- 2010 average deviation in the graph I am looking at https://nsidc.org/data/seaice_index 

The question I was raising was therefore whether the sea ice melt would indeed have as much of an effect this winter on the northern hemisphere cold air distribution. Some effect, Yes certainly, but more effect this year than previous ?  

That's +/- 2 standard deviations - assuming that there was no long term melting trend and the ice extent had a normal distribution (i.e. the range of values) then statistically there would be only around a little more than 2% chance of the extent being lower than it is the moment. The ice is still in a very poor way albeit not as bad as the end of summer in some recent years. Worth bearing in mind that the lowest summer extents don't always have the lowest values by late autumn, never mind winter - this summer's levels are similar to last year and last winter had the lowest extent on record for much of the time.

[Man With Beard]

A look at the clusters for a few points in the coming two weeks.

First, T168 (15th September). The past three runs look like this:

    

You can see the options that have lower heights closer to the NE have increased in number. I wouldn't feel particularly confident about the prospect of good weather for next weekend.

Next T240 (18th September)

    

Signs of heights trying to shove into a Sceuro area but not that significant - also an even more intense looking Atlantic moving in - would suggest a NW/SE split but this could be a case of SE just being less unsettled, rather than actually being settled. A chance of a quick height rise / plume ahead of incoming lows but that doesn't look guaranteed. A larger chance of something a bit windier approaching the NW.

Finally T312 (21st September)

    

Very split - no strong direction here, but what I notice is that the lines are still tight in the Atlantic, low heights look resident near Iceland, and there's a tentative attempt to block the Atlantic to our east. The odds, I feel, are that the Atlantic will prove too strong and ridging to the east will still not be able to influence the UK in terms of settled weather, apart from maybe in the south. However, the ridging may be sufficient to deflect some Atlantic energy south into Europe. If that happens, then it could become increasingly wet and windy for the whole of the UK. 

So, overall, not lots to be optimistic about if you are seeking an Indian Summer - yet - aside maybe one or two warmer days this week in places, and maybe another day or two around the 18th. There's room in the models for the south to turn out reasonably well throughout the period, but a big change will be required for it to be settled in the north for any length of time.

 

[Frosty.]

If there is still a water shortage, there won't be if the Gfs 12z operational low res is anywhere close..torrential rain at times nationwide.

[Frosty.]

Looking at the week ahead, the Gfs 00z operational shows the southern half of england and wales largely fine, warm first half, cooler second half once a cold front / band of rain has cleared the south, more unsettled and cooler across central and northern areas. Beyond that, turning very unsettled and cooler across all areas..autumnal.

[Frosty.]

3 hours ago, Frosty. said:

Looking at the week ahead, the Gfs 00z operational shows the southern half of england and wales largely fine, warm first half, cooler second half once a cold front / band of rain has cleared the south, more unsettled and cooler across central and northern areas. Beyond that, turning very unsettled and cooler across all areas..autumnal.

Ditto the 6z as far as the week ahead is concerned, there are a few warm fine days here and there further s / e beyond that but plenty of cool rainy autumnal weather too, especially further n / nw.

[damianslaw]

Ooh just two posts so far today, both from Frosty.. a sure sign the outlook remains very underwhelming i.e. typical fayre. However, for the first time in a long time we look set to be locked in a very standard zonal flow, southern parts holding on to a bit of warmth, the north firmly in the cooler wetter airstream. In mid September this means weather to get very little excited about - no extreme conditions.

Looking at the jetstream profile, the flow will stay zonal all week, with a slight dig southwards before easing back north a touch, before a significant dig south as we move into the following week, the UK then on the cold side, before we see a cut off low cyclonic flow scenario, a split jet, with energy transferred into the northern arm, and heights building to the NE. A long way off..

Suspect this thread will remain very quiet all week, the summer heat lovers having finally deserted it, and the cold winter lovers, still in hibernation., waiting for November.

[mb018538]

Nothing much to add to the above - very typically zonal now looks like setting up from midweek onwards, with better weather the further south you are. The tropical system appearing looks like it’s not going to be too much of a player.

[Frosty.]

Really chilly end to the Ecm 12z, especially up north, I would expect some night frosts and a crisp autumnal feel to the weather.☺