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Model output discussion - August hot spell - how hot, how long?


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Astonishing rebound in momentum transport that is behind the current spectacular synoptics and associated high impact weather. Both the heat, and also the powder keg potential for thunderstorms.

*** USING THE ECM TO FORECAST TEMPERATURES IN A HEATWAVE - A REVIEW *** I often make predictions based on models several days ahead, and then I find it useful to revisit these predictions after t

The reality is that NWP is wholly congregated on, but susceptible to be blindsided and over preoccupied by, the re-ignition of the low frequency tropical convective standing wave across Africa and the

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4 hours ago, Tamara said:

Question marks persist over the enigmatic behaviour of the QBO. There is now a very high chance of failure of transition, despite some (future seasonal!) wish-casting in other arenas. Note that July has now reversed the easterly downwelling phase

Thank you for another stonking post, Tamara!:oldgood:

And the bit I've quoted, I find particularly interesting: assuming/guessing (as I am) that the QBO switches are some kind of 'elastic' response to accumulated drag, I wonder whether AGW might be throwing a 'spanner into the works' somehow?

One 'failure' can be put down to a 'freak' event perhaps... but two in the space of only a few years?

Well, I don't know... I'm just musing.:unsure2::oldgrin:

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23 minutes ago, Dominic Carey said:

What temperatures would this set up bring?

Roughly 15-21c sliding cooler to warmer from the NW to SE. A bit below average.

Edited by mb018538
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37 minutes ago, CreweCold said:

Yep sad when people get jumped all over for daring to take a view that differs from what people want to see.

Whatever happens from now on, people can't really moan about this August.

Seasonal bias has always hindered rational objective discussion on here, its made worse when people who should know better compound such views.

Meanwhile, the 12z in FI returns us to an average unsettled westerly regime towards the end of the meteorological Summer as we slide inextricably in the direction of  .... erm... September....

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1 hour ago, Dominic Carey said:

What temperatures would this set up bring?

Temperatures to plummet Sunday onwards for another week down to below average/average. Eg 15 degrees in north Wales. The weather is returning back to June/JUly types with constant low pressure and NW winds. early autumn on the way based on the models

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The 12z GFS (removing the absurd idea of that large enclosed low) is on a similar trajectory to the ECM, an open trough would allow winds to veer towards the west or north west as opposed to the generally south to south west cyclonic flow (The GFS is actually quite warm in places still to day 10), UKMO looks very ECM like.

Looks like 30c could be reached on Thursday as the progress of the Biscay low looks more hindered than initially thought.

Edited by Captain Shortwave
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10 minutes ago, Captain Shortwave said:

The 12z GFS (removing the absurd idea of that large enclosed low) is on a similar trajectory to the ECM, an open trough would allow winds to veer towards the west or north west as opposed to the generally south to south west cyclonic flow (The GFS is actually quite warm in places still to day 10), UKMO looks very ECM like.

Looks like 30c could be reached on Thursday as the progress of the Biscay low looks more hindered than initially thought.

image.thumb.png.4d7445e20fffd5714635a566fc804081.pngimage.thumb.png.57df59dd9d2e28082bc813078c313036.pngimage.thumb.png.9d3477f0a6c8c2f3f830abd8568ae54f.pngimage.thumb.png.976098e7972ea9a6b147a312cb65deca.png Heat swept away by Saturday with low pressure all the following week centred over the Republic of Ireland image.thumb.png.8d61c10e3c16eca6ce093f93bf87659b.png Rain only over the land! remarkable!image.thumb.png.4b89169a14e45ced1afb6d0c7c0e452a.png ECMWF shows very unsettled cool conditions all next week. 

Edited by NApplewhite
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Evening all 🙂

Day four of the great heat of 2020 (apparently) - 32c in lowland East London (I think) but more humidity and really not pleasant.

So for how much longer will the oven be switched on?

MY acquaintance (I wouldn't call it a friend) Arpege has been of value through this unpleasantness:

arpegeuk-41-26-0.png?10-17arpegeuk-41-50-0.png?10-18arpegeuk-41-74-0.png?10-18arpegeuk-41-98-0.png?10-18

As has been the case in the past couple of days, Arpege suggests tomorrow's heat will be more over central southern England while for Wednesday it's back to the far SE and East Anglia. It now looks as though there will be a final day of heat on Thursday for parts of East Anglia before by Friday we break out the thermals as the temperature crashes to a chilly 27c.

arpegeuk-47-26-0.png?10-17arpegeuk-47-50-0.png?10-18arpegeuk-47-73-0.png?10-18arpegeuk-47-98-0.png?10-18

Now, my other new friend, the Humidex, is painting a slightly different story to the weekend. High values over central southern England (40) but surprisingly the humidity isn't as severe on Wednesday as some earlier forecasts suggested so I'm just wondering if the storm risk has been overplayed a little. Obviously, we could import something from France but I'm pleasantly surprised some of the frankly obscenely oppressive numbers have disappeared.

The rainfall accumulation also suggest the main rain will be to the west rather than the east so we'll see.

 

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I haven’t given the Mighty Navgem an outing for a while so here it is . It’s much slower to my eye anyway in clearing the heat . 
 

incidentally has anyone noticed that recently the navgem’s uppers has fallen largely in line with the other models?  Perhaps an upgrade? ( Ahem ) 

I see a post or Two claiming Summer is over 🤪. I suppose we can write off Winter too whilst we are at it . What Nonsense .

48A606ED-2F14-40AA-B305-338F724876F8.png

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40FAF902-2FF7-42B7-9088-45AD169AFF1A.png

Edited by Mark wheeler
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1 hour ago, Mark wheeler said:

I haven’t given the Mighty Navgem an outing for a while so here it is . It’s much slower to my eye anyway in clearing the heat . 
 

incidentally has anyone noticed that recently the navgem’s uppers has fallen largely in line with the other models?  Perhaps an upgrade? ( Ahem ) 

I see a post or Two claiming Summer is over 🤪. I suppose we can write off Winter too whilst we are at it . What Nonsense .

48A606ED-2F14-40AA-B305-338F724876F8.png

B95AAF69-E428-4E11-8C8C-9833636B8C3C.png

BEC4CD5C-B898-476A-AD68-D0B75898620E.png

40FAF902-2FF7-42B7-9088-45AD169AFF1A.png

Can't be that wide of the mark, 21 days to go?

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Only been taking cursory glances at the models over recent days. Outlook remains rather uncertain, the heat looks like it will drain away slowly as we move past Thursday with lower heights invading from the south, creating a messy disturbed picture. The weekend currently looking much fresher and mostly fine with chance of showery rain in places.

ECM and GFS then want to bring the trough down and through the UK producing a much cooler unsettled outlook, but with heights still sat to our NE, such a spell could be shortlived with heat once again returning.

Longer term awaiting to see how tropical storm developments might shake things up a bit, given forecasts for a very active season, but so far we haven't had much influence..

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5 minutes ago, ribster said:

Can't be that wide of the mark, 21 days to go?

Depends on what an individual sees as summer ? For some it’s not Heat and Sun , Plenty to keep the storm enthusiasts going for the foreseeable for example , I also see no raging jet stream in the outlook either but I know through experience to expect the unexpected. Perhaps also an Indian summer in Autumn that would be great .
 

Anyway a bit off topic so I shall pipe down now and wait for the evening runs especially the Navgem ( better than the GFS 🤥 )

Edited by Mark wheeler
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Last day of summer is 20 September according to the cosmos. Plenty of summer to go, let’s hope it’s pleasantly warm rather than days on end of furnace like temps, which we are currently enduring down here. That said, late August and September heatwaves aren’t that rare, so I wouldn’t count on it! 

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Just an interesting note on tomorrow. The Arome has Heathrow reaching 36C by just 1pm. It then drops off due to a thundery development. But if the potential is there to reach 36C by 1pm, you have to wonder what's possible if the clouds don't arrive as forecast.

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8 minutes ago, Man With Beard said:

Just an interesting note on tomorrow. The Arome has Heathrow reaching 36C by just 1pm. It then drops off due to a thundery development. But if the potential is there to reach 36C by 1pm, you have to wonder what's possible if the clouds don't arrive as forecast.

Hows temps further north across midlands and east anglia mate?

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18 minutes ago, Man With Beard said:

Just an interesting note on tomorrow. The Arome has Heathrow reaching 36C by just 1pm. It then drops off due to a thundery development. But if the potential is there to reach 36C by 1pm, you have to wonder what's possible if the clouds don't arrive as forecast.

I see this but it’s the 1st time I’ve visited the site , is this accurate to your knowledge? Showing 37c over the next two days ? Perhaps a dodgy 2 instead of 7 .

35250E91-BE9A-4C9A-961A-F35471FBEB40.png

Edited by Mark wheeler
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6 minutes ago, Mark wheeler said:

I see this but it’s the 1st time I’ve visited the site , is this accurate to your knowledge? Showing 37c over the next two days ? Perhaps a dodgy 2 instead of 7 .

35250E91-BE9A-4C9A-961A-F35471FBEB40.png

I have been following AROME since June 2018 and I've found it to be neck and neck with ARPEGE for temperatures in hot and settled conditions, but slightly less strong when there's cloud and rain about.

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15 minutes ago, sheikhy said:

Hows temps further north across midlands and east anglia mate?

31 to 33C in Brum and possible 29 to 31 for Manchester , 30 to 32 for Leeds / Sheffield 

 

 

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