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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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18 minutes ago, summer blizzard said:

Euro AAM forecast now below -1 again from about mid month according to Matt Hugo. Run by run trend is more negative.

Early slide into autumn?

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4 hours ago, northwestsnow said:

Will there be a separate thread for thunderstorms next week guys?

There's been a separate thread for thunderstorms for years!

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GFS 18z rolling out looks like its finally happening for us at last - Manchester/Sheffield/Leeds getting a taste of the sticky heat and humid on Tues and Weds and Thursday looks warm too.  Could be a three day spell nudging close or at 30C with some high oppressive humid levels so hopefully some nice lightning storms along with daytime darkness. . Night times looks very warm not dropping below 23C on Tuesday night in Manchester and 26 in London. 

 

thursday.png

nights.png

humiddd.png

humiddddd.png

tuesd.png

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2 minutes ago, 38.7°C said:

GFS 18z rolling out looks like its finally happening for us at last - Manchester/Sheffield/Leeds getting a taste of the sticky heat and humid on Tues and Weds and Thursday looks warm too.  Could be a three day spell nudging close or at 30C with some high oppressive humid levels so hopefully some nice lightning storms along with daytime darkness. . Night times looks very warm not dropping below 23C on Tuesday night in Manchester and 26 in London. 

 

thursday.png

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humiddd.png

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Fantastic ukmo and gfs 18z!!keeps the heat widely across england nearly all week!ecm hopefully join in tomorrow morning!!whats with the arpege keeping the highest temps just across east anglia and south east next 3 days where as gfs and euro4 have it much  further west across england!!anyone got ukv temps for the next 3 days?

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Gfs definitely heading towards UKMO, Tuesday and Wednesday look very hot 35-37 possible maybe even 38 if right conditions, sunny, no thunderstorms, cloud, Thursday still looks hot 32/33 possible in London, friday mid to high 20,s Sunday heat building again, I wonder how this will pan out, wonder if it will go below 30 by end of the week 

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GFS pub run shows another hot day on Thursday, at face value a 32°C max in the SE.

image.thumb.png.e6856050d75e07db0f7e578cdbc2a912.png

Still very warm on Friday. Seems the muggy-ness will still be with us at this point, minima for much of England is 16-20°C

image.thumb.png.42fbf0fda1a530176d4510e70723a83b.pngimage.thumb.png.1d69adfffbcf9abd1d2a5d800635c0cc.png

Saturday is relatively back to average, but still reasonably warm further south and east.

image.thumb.png.e376943772531f0f7e50021296ac6860.png

Very warm again on Sunday in the SE / EA

image.thumb.png.849a462991b86edd18a5c876873336c4.png

Into fantasy island, looks relatively average or just below, with the odd warmer day but that's not worth looking at when this week isn't even resolved yet.

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47 minutes ago, Scorcher said:

Wishful thinking on your part I think...

Not really, August heat doesn't bother me at all...especially when there is a risk of storms thrown in.

More I was thinking out loud.

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ECMWF  00 model is out and it shows a cooling off from Sunday to Wednesday next week as a low pressure system established itself over the UK.  Much lower temperatures by the 19th August as the Scandi high remains and the azores high ridges north allowing the jetstream to move leaving us on the much colder side. 

image.thumb.png.7a0dc6f34ece0fd570ac8d52b8b4f3b3.pngimage.thumb.png.00a884cac21655f5db786d6a66ffaf4b.pngimage.thumb.png.d6928578e27792526847294c9a72316e.pngimage.thumb.png.df3e1216940eb6587c31f85917bc712a.png
 

image.pngimage.thumb.png.05c6ee97cdf479b42af7afb9c4498ce0.pngimage.thumb.png.f6b79494d25d42470542d37d7e8c273a.pngimage.thumb.png.c8cd853ce9e3c14d01bec43aec22bda8.pngimage.thumb.png.2f6e9b09c9b3bc9453d73fc3dccf421a.pngimage.thumb.png.35bfc3d1a8e48c8857277c3349571948.pngimage.thumb.png.14c52f567e3e47811e8a2475d84589ab.pngimage.thumb.png.65286a0ff1988179e37ed4042380e1c7.png Wet outlook for this week. image.thumb.png.1f5c6879d46bab52155c3e3344fb1c70.pngimage.thumb.png.b1cdd9264a5c738e20eaaf252fb64596.pngimage.thumb.png.8f4bc0bd97601dff634b7a2264274c88.pngimage.thumb.png.47df4ebe91e098cda9bcc94f55bfbcf3.pngimage.thumb.png.45995dd31abcc95780426c116c1f0032.pngimage.thumb.png.e171de9d3d3f48a7bc635c81e8110495.pngimage.thumb.png.2ed81128dfc3510f5bab479ab00a947a.pngimage.thumb.png.1c8c47859d4b3a88b3e7cd721d8098cf.png Longer range is distinctly average. 

Edited by NApplewhite
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23 minutes ago, NApplewhite said:

image.thumb.png.2ecf2bef80b33cb758c3e30dd676a30a.png

Wow. Only about a week later than the GFS was showing. It was completely wrong, yet again. All that rubbish about it being the king model because it was showing cooler and unsettled weather for this week before making a massive backtrack. 

Not sure what the point of your comment was. It’s like claiming a prediction of snow 10 years ago was right because 2 years ago we had the ‘Beast from the East’.

Edited by MattStoke
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Morning one and all - 

3/4 more days of heat, before Friday finally sees something closer to normal (though humidity will sadly still be high).

What next though for the second half of August, and the final 2 weeks of meteorological summer?

Having a look through latest data available, the prospects aren't great if you like the heat and settled weather. Conversely, if you are sick of this, and want something more akin to June and July, you may be in luck.

AAM is likely to fall back into negative territory after the recent spike at the of of July onwards (hence our change of fortune, and much improved weather in NW Europe).
Our old friends - the Indian ocean standing wave coupled with a suppressed Pacific - is likely to reform and intensify through August, which is the pattern that dug itself in through June and July.

image.thumb.png.ad801847407e609a1c0fcba860ccdd45.pngimage.thumb.png.6f3fbe19c53db5599612fc452e86ba4c.pngimage.thumb.png.a8a1c3e8ee78e3331a2efe4370f87abd.png 

This tends to retract the NW European ridge and promote troughing again. The CFS weeklies show this process through August as the ridging slowly ebbs away, and ends up with a trough. Last nights ECM OP & biggest cluster also show this ridge retraction & trough setting up. This mornings ECM follows this trend:

image.thumb.png.7a6ec6320d0a16b543fbc78a2a814a25.pngimage.thumb.png.753e549d0cccd3ce698e5cf0e8b70154.pngimage.thumb.png.110cae54360e9a3c89a3cc3214b83019.png

This doesn't necessarily guarantee a washout is imminent - more that the cards are starting to be stacked against us here in the UK for a continuation of a very memorable first half of August, and one that's been so long overdue!

(Images above courtesy of Matt Hugo, Ant Masiello, Simon Lee, Victor Gesnini) 

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The Thursday to Saturday period continues to be uncertain, with all main models now holding the upper trough very slightly west. This means genuinely cooler air is very slow to work through the country, and some eastern areas are forecast to remain in the mid to high 20s even by Saturday (which may seem cool after the last few days, but is usually considered very warm!).

I suspect the thundery risk will remain right up until Saturday. 

However, it's possible we haven't seen the final solution, and small changes on the trough could either usher in a faster breakdown, or extend the 30C plus days even further.

 

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ECM1-72.GIF?10-12   ECM1-120.GIF?10-12   ECM1-168.GIF?10-12

It looks like that low might need two attempts in breaking the pattern down fully, the first will likely drop the temperatures back to less extreme levels (Mid/High twenties possible even during the weekend). The second looks more likely to succeed as the pattern upstream is unfavorable and likely to stick the UK between the ridge that has influence our weather this week and an amplified ridge in the Atlantic. 

However a lot of questions need to be answered on that complex circulation in the Atlantic in the day 4/6 range and its eventual track and whether it does indeed lift out. The one thing I do note is that the eventual low at the end of the week has been toned down somewhat, still sending up a lot of rain but of course allows perhaps something drier by next weekend in the east perhaps (and still very warm).

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10 hours ago, bluearmy said:

Not convinced rob as the mean upper trough has edged over nw Europe rather than west of Iberia ....could be very messy as the difference between very acceptable summer conditions and the opposite may not be far apart .....

Aye, smacks of an Easterly to me, showery in the South, drier and sunnier in the North, we wouldnt get a hot southerly but a warm, southerly sourced easterly?.. It wont be as hot as current conditions though, but better then average?

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37 minutes ago, Captain Shortwave said:

ECM1-72.GIF?10-12   ECM1-120.GIF?10-12   ECM1-168.GIF?10-12

It looks like that low might need two attempts in breaking the pattern down fully, the first will likely drop the temperatures back to less extreme levels (Mid/High twenties possible even during the weekend). The second looks more likely to succeed as the pattern upstream is unfavorable and likely to stick the UK between the ridge that has influence our weather this week and an amplified ridge in the Atlantic. 

However a lot of questions need to be answered on that complex circulation in the Atlantic in the day 4/6 range and its eventual track and whether it does indeed lift out. The one thing I do note is that the eventual low at the end of the week has been toned down somewhat, still sending up a lot of rain but of course allows perhaps something drier by next weekend in the east perhaps (and still very warm).

Ecm looks more cut off than last nights 12z and has gone towards 12z ukmo!!love it when we see an extension to a heatwave or cold spell!!

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A lot of talk of AAM again in here over the last couple of days. I think after July we should know not to trust these forecasts of AAM going positive/negative etc.

It was forecast to turn positive in early July if I remember rightly- and it never really happened as expected.

I can't claim that my knowledge is brilliant on this but I certainly wouldn't be putting money on an early start to autumn.

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6 minutes ago, Yarmy said:

Arpege has a max of 36C in Norfolk on Wednesday which would be pushing the local record (made last year):

arpegeuk-31-66-0.png?10-06

it does seem to keep the heat more focused for the E/SE

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The Arpege's take on max temperatures over the next few days, today's through to Thursday:

image.thumb.png.bdff0690e5f45aa7bad143f3d90bf6be.pngimage.thumb.png.ae6aa829cb54ed07760bdcc4321d0aeb.pngimage.thumb.png.8c7493f47fec278ce6bdaab680fbe5e8.pngimage.thumb.png.27277ab40d8c583e007588373db9e4ed.png

So based on this, we are looking at highs of 34 / 35 / 35 / 31 with nighttime minima in the low 20's 🥵 

Also, some very high CAPE being modelled for the next few days.

image.thumb.png.69c31b54fda71a1b2da88d4007d55042.png  image.thumb.png.bc8537d0aa406b0a43e5dab671bd7e7e.png 

Wednesday could go bang in a major way if these numbers are on the mark.  Superb model watching at the moment.

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30 minutes ago, Scorcher said:

A lot of talk of AAM again in here over the last couple of days. I think after July we should know not to trust these forecasts of AAM going positive/negative etc.

It was forecast to turn positive in early July if I remember rightly- and it never really happened as expected.

I can't claim that my knowledge is brilliant on this but I certainly wouldn't be putting money on an early start to autumn.

Always a possibility, but i can't see anything in any of the output to suggest anything other than a transition towards unsettled weather? It was only the CFS AAM forecasts that were positively biased, the ECM forecast was spot on right throughout and never really showed any positive tendency until the veyr end of July, which is what transpired.

500mb heights and SLP are forecast to stay low/decrease markedly on the latest ECM ensembles. Low SLP in summer doesn't mean a washout, as we are showing now, but the drop in 500 heights just says unsettled weather is coming to me. Unless anyone has anything on the contrary?

image.thumb.png.05699844a4d964d1f6c8c003882d1fc4.pngimage.thumb.png.2e7b376bd58cfac432d272d1084be568.png
 

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