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


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9 minutes ago, Djdazzle said:

Doesn’t equate that today’s max will be 3C short though.

Indeed - UKV still going for a max of 36C today.

C15C204C-9D63-44F3-9B26-C37B3F7377D5.thumb.png.f8d3379e1d893b7463c70b1c165e70c4.png
 

@Alderc some nice cells approaching the SW - lightning kicking off.

07481016-5E69-4899-A66C-691CE46B65DF.thumb.png.665109a634fc9c29f15b1ec9442933dd.png

Edited by Mr Frost
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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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Yes temperature are definitely several degrees down compared with 7 days ago; the temperature dropped lower than forecasted in the early hours this morning.

However last week the wind picked up and cloud arrived around 15:30 onwards putting the brakes on any further rise despite being quick out the blocks in the morning.

Today is off to a slower start but the lighter winds and all day sun should still result in a very hot one with a more sustained climb peaking later in the afternoon in comparison. It will be interesting to see how much of an impact having a cooler night beforehand has! Stay cool everyone! 

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2 minutes ago, Mr Frost said:

Indeed - UKV going for a max of 36C today.

C15C204C-9D63-44F3-9B26-C37B3F7377D5.thumb.png.f8d3379e1d893b7463c70b1c165e70c4.png
 

@Alderc some nice cells approaching the SW - lightning kicking off.

07481016-5E69-4899-A66C-691CE46B65DF.thumb.png.665109a634fc9c29f15b1ec9442933dd.png

The cells near plymouth are good and developing in a clean environment, the rest behind is just convective leftovers and a mess. All it will do is hinder sunshine and provide light to moderate rain over a much wider area than currently forecast. This isn't a grumble but an almost certainty.

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22 minutes ago, kold weather said:

Broadly 1-2c lower.

Today will give a good indication of the models grasp of the actual heat and will show whether the models backed off too much.

Still very hot to be fair as well.

Steve, given we are still accepting warm air in its entirely possible we carry on at near 2c an hour through to 3.30-4pm before things level off.

The dynamics compared to last week are different, in fact there was a fairly sustained southerly breeze last week, which quickly dried the air at the surface out. This allows temperatures to rise quicker. Obviously today we have very light winds so a slower rise during the morning isn’t a surprise.

GFS op on the 06z has 34c for central London, actually given the set up I think London will be the top spot (Kew Gardens or St James park) and I will still go for 36c today. Stronger winds tend to push the hottest temperatures towards the north/west of London and areas north of that (Oxford/Cambridge corridor for instance).

More model related - Euros still fairly consistent in trying to break the heat down mid-week with low pressure trying to lift northwards. However following it does seem that the Azores high could build back in from the west again to bring more settled conditions after the potential fireworks next week.

Edited by Captain Shortwave
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Latest gfs has 35 tomorrow, 34 Sunday and Monday 31 Tuesday then it’s all over, maybe gfs is being over progressive again we will see in future runs, looks like for now   Records will not be broken maybe night time, how ever can change in future runs 

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41 minutes ago, Djdazzle said:

Doesn’t equate that today’s max will be 3C short though.

It doesn't, but the maximums at 11am are still 2 or 3 degrees lower than last Friday.

Although we could have longer heating today when maximums are achieved at 4pm or 5pm instead of 3pm as last week.We shall see.

My view is that we will fall some way short.

35c, with 34c more generally.

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6 minutes ago, sunnijim said:

It doesn't, but the maximums at 11am are still 2 or 3 degrees lower than last Friday.

Although we could have longer heating today when maximums are achieved at 4pm or 5pm instead of 3pm as last week.We shall see.

My view is that we will fall some way short.

35c, with 34c more generally.

Just to add on this, when we are shooting for those really high maxes heating the ground from say 34-37c after 3pm is very very difficult. I think on most of the hottest days maxes are usually 1-3pm not the usual 4-5pm we normally expect. Let’s see what happens in the next few hours. 

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3 minutes ago, Alderc said:

Just to add on this, when we are shooting for those really high maxes heating the ground from say 34-37c after 3pm is very very difficult. I think on most of the hottest days maxes are usually 1-3pm not the usual 4-5pm we normally expect. Let’s see what happens in the next few hours. 

that's only the case recently because usually a cold front started spilling cloud into the areas that are likely to get the highest temperature. Between 3 and 4.30 normally is  peak temperature of the day typically and unless we get a surprise amount of convective cloud come over the usual hotspots I would guess that will also be the case today. Cou

IMO we are gunning for something in the 36s, maybe low 37. 

Edited by kold weather
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11 minutes ago, sunnijim said:

It doesn't, but the maximums at 11am are still 2 or 3 degrees lower than last Friday.

Although we could have longer heating today when maximums are achieved at 4pm or 5pm instead of 3pm as last week.We shall see.

My view is that we will fall some way short.

35c, with 34c more generally.

You will be surprised when you see the 12-2 maximas we will surpassing 35c by then.

Max temp today around 5-530 pm

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The wind is also meant to veer more SE from midday, so this may facilitate a sharp rise.

Edited by Djdazzle
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6 minutes ago, Steve Murr said:

You will be surprised when you see the 12-2 maximas we will surpassing 35c by then.

Max temp today around 5-530 pm

Not so sure on that one today, a large mass of cloud is going to be over London before 5pm today and that is a cloud shield that is expanding, certainly not breaking up. 

Also surprise Arpege still going for 33C just inland from here today, to be honest its not got a good handle on the precip in the channel, there's a lot more in reality, its further and moving more NE opposed to NNE, that to me suggests there is less of a push of heights from the south east. 

Edited by Alderc
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For what it's worth, temperature here appears to be 89f or just shy of 32C at 1130. Should note the thermometer is on the east side of the house but in shade on a North facing wall.

Currently Arome cloud cover charts looking accurate incidentally.

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For those who say I only post nice charts, stick this in your pipe and smoke it!!!..joking aside, there’s plenty of heat, and sunshine and thunderstorms to come before that possibility!?😜

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Edited by JON SNOW
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Right lets be honest, not a single model has got a truly great handle of the situation this afternoon. Not a single has any showery activity at all through the spine of the country around midday yet we have thundery showers breaking out from York down to the midlands. All also under-estimating the precip in the south west significantly as well. 

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WOW Tamara, you are a legend!..as for the GEFS 6z mean, sure there’s a stutter mid range but generally speaking this is light years better than July..apart from July 31st that is!😜..enjoy all the heat, sunshine and thunderstorms blah blah in the meantime!😉

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54 minutes ago, Alderc said:

Right lets be honest, not a single model has got a truly great handle of the situation this afternoon. Not a single has any showery activity at all through the spine of the country around midday yet we have thundery showers breaking out from York down to the midlands. All also under-estimating the precip in the south west significantly as well. 

got that right , anyone have any idea why

Edited by Gordon Webb
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At 1400 it was 29.5 and rising with Humidity at 47%.

Heathrow seems to have it's own micro-climate or dodgy instruments, I can understand Kent being hotter with the SE wind flow.

This time last week it was 33c here.

 

 

Edited by Arch Stanton
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58 minutes ago, Gordon Webb said:

got that right , anyone have any idea why

Look at the Met O Fax 0600 Z chart, the reason is clear, a trough from the low in Biscay!

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Afternoon all 🙂

33c here in lowland East London and looking at Arpege, has it backed off some of the really high values forecast a day or so back?

arpegeuk-41-32-0.png?07-12arpegeuk-41-57-0.png?07-13arpegeuk-41-87-0.png?07-06

First two are from the 06Z run, last one is from the 00Z.

The curiousity is the heat being "confiend" to the southern coastal counties suggesting an onshore flow for eastern areas and that keeping London fractionally cooler. 

nmm_uk1-31-36-0.png?07-11

The WRF 06Z also suggests a change in the heat profile from the more traditional broad push north of the classic plume to a more sharply defined event for the far SE.

 

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2 minutes ago, stodge said:

Afternoon all 🙂

33c here in lowland East London and looking at Arpege, has it backed off some of the really high values forecast a day or so back?

arpegeuk-41-32-0.png?07-12arpegeuk-41-57-0.png?07-13arpegeuk-41-87-0.png?07-06

First two are from the 06Z run, last one is from the 00Z.

The curiousity is the heat being "confiend" to the southern coastal counties suggesting an onshore flow for eastern areas and that keeping London fractionally cooler. 

nmm_uk1-31-36-0.png?07-11

The WRF 06Z also suggests a change in the heat profile from the more traditional broad push north of the classic plume to a more sharply defined event for the far SE.

 

Yes, one day wonder here, temp for today slightly revised down and more so for next four days, before dropping away further.

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