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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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I do wish this summery weather would just get on with it and start... to think tomorrow could be the hottest day of the month and it currently looks like late October outside...

I'm encouraged by all the models, though, at a generally lengthy spell of summery weather, as has been well pointed out by many members already this morning. Although we supposedly shouldn't pay too much attention to the GFS in the long run, I do like its reinforcement of heights from the SW later on in the runs just when you think things might turn more unsettled. Perhaps a few shots at plumes later in the month too. The 10C isotherm rarely leaves the country throughout.

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48 minutes ago, sheikhy said:

Unbelievable charts from all 3 of the main models!!heatwave conditions across england for nearly a week!!🔥🌡

 

 

A little misleading. Not all of England.

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11 minutes ago, Daniel said:

Metoffice going for 37c

Screenshot_20200806_103217.jpg

Interestingly, the models have reduced tomorrow’s highest temperatures slightly but increased Saturday’s. Could be that Saturday gives a slightly higher chance of breaking records.

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Well people, there's no escaping it: tomorrow will be hot, hot, hot!:shok:

h500slp.png    h850t850eu.png

As an aside, the NW app thingie has me down for 32C, this coming Monday afternoon; which, for somewhere so close to the North Sea, is quite unusual...But, as an aside aside, a week later, it's predicting sunshine and 16C for 1300 hours, followed by 20C at midnight... which hardly makes any sense at all, IMO!:oldgrin:

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15 minutes ago, MattStoke said:

Interestingly, the models have reduced tomorrow’s highest temperatures slightly but increased Saturday’s. Could be that Saturday gives a slightly higher chance of breaking records.

I think cloud is going to be the problem tomorrow. GFS suddenly gung-ho with large amounts of CAPE right through the weekend with some big TS breaking out even Saturday afternoon almost anywhere.

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1 hour ago, johnholmes said:

re this

Anomaly charts are great for trends but they can't tell me what weather I might get on a certain day, which the NWP does very well (usually) within 6 days.

I do agree that, good as it is to see folk looking and using these charts, sometimes the summary of what the poster says they show is, in my view, not really correct. As MWB posts they are not for surface detail at all. They can, when used carefully, give a very good idea of what the general weather is likely to be in the 6-10 day range and can be useful in the 8-14 day outlook also.. 

.......... Which is why matching those with the nearest GFS or ECm is useful, the NOAA charts will give you an accurate idea of the mean pattern of troughing and ridging plus the mean upper flow. You can then extraploate surface detail off the nearest ops... This is a very successful method that ive been employing for some time now, and its certainly more stable and accurate for that timeframe then trying to decide which op has found a new trend.

Talking of which... these charts still expect a trough over west of Northwestern Iberia, nudging into Biscay, High to our Northeast over Norway.. That has to suggest a Southeasterly flow for most of the time, even if the upper flow on that chart is a light southerly or ssw. It wouldnt surprise me at all if a major pattern change in the GFS and ECM were to back this... by dropping the propinquity of the Azores high. But hey...learning is fun..



 

610day.03th.gif

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5 hours ago, Captain Shortwave said:

UKMO pretty consistent on the passage of events early next week.

UW96-21.GIF?06-06   UW120-21.GIF?06-06   UW144-21.GIF?06-06

Looks like by Wednesday we may start to see a more significant area of low heights form at it begins to interact with that shallow Atlantic trough. So perhaps a more widespread outbreak of showers and thunderstorm developing by midweek, however the timing of this is uncertain and will be more drawn out than the normal set up due to how far north the main arm of the jetstream is going. By the way, yet again temperatures will be hot to very hot across the south with this extending northwards during the first part of next week.

GFS also looking god for the first half of next week too, however it is still struggling to get the proper shape of the longwave pattern right with that weaker southern arm dipping into the Bay of Biscay.

gfs-0-96.png   gfs-0-120.png   gfs-0-144.png

Just a random little note about the GFS, it has a high of 33C for Friday, but 34C on Saturday.

So five, perhaps six days where 32C+ could be reached in the south in a row. More limited in the north of course.

 

Also a few posts have been hidden from last night, please refrain from making personal comments please. Thank you 😊 

Looks like a big temperature upgrade is coming

 

Have a look at GFS 06Z (right) compared to GFS00Z (left) for next Thursday 13th August and the previous run . 

2 degrees have been knocked off the highs for tomorrow (August 7th 2020) though across most places in England and Wales.  I can see more changes by tonights 12Z. 

 

image.thumb.png.fb63753fe74857b923e4f0377d99e19f.pngimage.thumb.png.42ea0b17e1a86aac840d03c43bc42061.pngimage.thumb.png.a8df5d8d98f9ade73ebba9ee6d696017.pngimage.thumb.png.dbebfc6074bbca39f9eda21f62f1afeb.pngimage.thumb.png.6bc985d8cdde2bc3d1801a8bd459f080.png

Edited by NApplewhite
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An ever so slight tone-down for tomorrows heat, possibly due to a slightly faster encroachment of the upper cloud. Still looking good though for a 35-36c IMO, maybe a 37c in favoured hotspots.

What is increasingly evident is the models are now increasing temperatures throughout the Sat-Wed period. Saturday looks ever bit as hot as Friday is now in terms of max temperature and with a wider reach of 28-30c into the Midlands. I suspect we are about to see at least a 5 day period with maxes above 90F.

Beyond that and the temperatures are subject to quite large changes depending on just how much convection can kick off. Whilst the models have a habit (especially the GFS) of overdoing convection, the risk certainly looks there, especially further north you go.

In terms of long lasting very hot temperatures, the 06z for the SE is about a good run as I've ever seen within 168hrs!

Edited by kold weather
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That was a long hot to very hot run all depends on cloud cover but what I see is below -

tomorrow top temp 35/36

sat 36 possibly 37

sunday 35/36

monday 36/37

tuesday 35

Wednesday 35

thursday 34

friday 30/31 all subject to change with more runs and cloud cover, one to watch on later runs is 12th 13th August which could be the peak of the heat if all falls right 

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UKV now has 35°C at midday on Saturday which would probably mean Saturdays high would end up higher than the 35°C it shows for tomorrow if it went out further  

C597FF8C-C82A-4E59-8478-CA8B8D0745BD.thumb.png.1ce05a2cb0824e095b1f3de1a9ebdcfc.png

Also still showing 27°C at midnight tomorrow night. 
71947603-AD2D-447F-8C67-71DB75BEC8F2.thumb.png.f6d2b498bdcabab1641328fcee1d7a95.png

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36 minutes ago, General Cluster said:

Out to next Thursday, and the GFS 06Z has the 15C T850 isotherm encroaching toward Fife and Tayside... is @Kirkcaldy Weather going to steal all our storms...again!:oldlaugh:

h500slp.png    h850t850eu.png

🤣 an easterly can kill off thunderstorm chances have seen it happen many times here, think it’s the cooler flow off the North Sea though on those charts it looks like quite a slack flow but the details at a week away are not worth fretting about at this stage as we all know 😅 I’m not sure what the record is but somewhere down in the SE possibly threatening the August highest minimum temperature tomorrow night 🤔

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17 minutes ago, matt111 said:

UKV now has 35°C at midday on Saturday which would probably mean Saturdays high would end up higher than the 35°C it shows for tomorrow if it went out further  

C597FF8C-C82A-4E59-8478-CA8B8D0745BD.thumb.png.1ce05a2cb0824e095b1f3de1a9ebdcfc.png

Also still showing 27°C at midnight tomorrow night. 
71947603-AD2D-447F-8C67-71DB75BEC8F2.thumb.png.f6d2b498bdcabab1641328fcee1d7a95.png

What is with the cooler air around the wash area!!you got 25 26 degrees across england widely and then there is that weird spot around the wash of 23 degrees only!!is that on the boundary of the 15 degree 850hpa temp?if it is then there must be a band of cloud along that boundary🥴

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Today is a case in point as to why cloud amounts on the models shouldn’t be taken as gospel. It’s breaking up much more readily than many of the models were indicating. Should be a sunny and hot afternoon down south.

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Rather nice (or rather scary?) at T+384... far too early for any over-excitement I know, but the chance of an all-round stonking August is most certainly there!:oldgood:

h500slp.png    h850t850eu.png

Edited by General Cluster
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  Which is why matching those with the nearest GFS or ECm is useful, the NOAA charts will give you an accurate idea of the mean pattern of troughing and ridging plus the mean upper flow. You can then extraploate surface detail off the nearest ops... This is a very successful method that ive been employing for some time now, and its certainly more stable and accurate for that timeframe then trying to decide which op has found a new trend.

Very true mushy, as usual with a great deal of care, but for those interested it is worth giving it a go. Not just now but in the hectic search for cold come the winter!

 

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15 minutes ago, Djdazzle said:

Today is a case in point as to why cloud amounts on the models shouldn’t be taken as gospel. It’s breaking up much more readily than many of the models were indicating. Should be a sunny and hot afternoon down south.

I would've said the opposite? Temperatures here are suppressed, still only 23-24 under cloud and yet we're forecast to reach 30 later.. 

 

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