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


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I dont share the optimism some of you are holding on to. Id be very surprised if this chart which yet again suggests troughing and a mean upper northwesterly will be inaccurate enough to allow much of a more summery feel by later next week. (True early next week is looking pleasant).
If you go on the GFS on Wetterzentrale and click North America, you can see this trough develop over Canada, as very warm/hot air drifts up from the American midwest and clashes with cool polar sourced air . That trough deepens and tracks rapidly Eastwards to take up residence in the north Atlantic, drifting slowly Eastwards.

 

814day.03mid sept poor.gif

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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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As ever mushy the proof will be in the eating..

Looks mainly dry locally after a blip today and tomorrow.

Next week looks nice to begin with but subtle hints the high pressure in the mid Atlantic may be dragged west opening the door to a north westerly.

 

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1 hour ago, mushymanrob said:

I dont share the optimism some of you are holding on to. Id be very surprised if this chart which yet again suggests troughing and a mean upper northwesterly will be inaccurate enough to allow much of a more summery feel by later next week. (True early next week is looking pleasant).
If you go on the GFS on Wetterzentrale and click North America, you can see this trough develop over Canada, as very warm/hot air drifts up from the American midwest and clashes with cool polar sourced air . That trough deepens and tracks rapidly Eastwards to take up residence in the north Atlantic, drifting slowly Eastwards.

 

814day.03mid sept poor.gif

I don't think anyone has said that it's going to be outstanding. Of course these charts show a predominantly westerly regime, but you can still get the odd nice day here and there. These charts are a good summary of the overall pattern but they don't necessarily show the minutiae from day to day.

I think most people's expectations are low at the moment, but in the medium term there has been a small improvement from yesterday from the op charts.

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1 hour ago, Scorcher said:

I don't think anyone has said that it's going to be outstanding.

 

nope they havnt, just "optimistic" , but apart from a few days of pleasantness early next week, theres no real evidence (imho) of a shift to a lengthier settled warm spell (which i would certainly welcome) showing... of course the outputs are subject to change, im just commenting on what the current outputs are showing now.

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1 hour ago, Scorcher said:

I don't think anyone has said that it's going to be outstanding. Of course these charts show a predominantly westerly regime, but you can still get the odd nice day here and there. These charts are a good summary of the overall pattern but they don't necessarily show the minutiae from day to day.

I think most people's expectations are low at the moment, but in the medium term there has been a small improvement from yesterday from the op charts.

Definitely looks better than yesterday. The deep low in our neck of the woods in just over a weeks time isn't half as bad on today's output. The 6z extends the low but is a big outlier.

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Not a bad ECM tonight.  Days 5-8 looking pretty warm and settled, certainly for the south of the UK.

image.thumb.png.28580fcbf55355ff46ba9d312381cfee.pngimage.thumb.png.ccdb80737fde7ef96301a3c96d9a323e.pngimage.thumb.png.018d2e0abcc14293671215b1c2e854d1.pngimage.thumb.png.4a2e51134b004e13994f21c21801c323.png 

By day 10, there's an attempt for another push of heights from the south west but far too out to worry at this stage (nice to see -18 uppers over Greenland as well, if that's your thing 🤭 )

image.thumb.png.a3012fc5f8203b8a2f33cfa8df5f7581.pngimage.thumb.png.abdfbb35b2ed9c3598ccc079c019ab9e.png  

Nothing spectacular on the cards, but overall quite positive for some 'usable' weather ahead.

 

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Looks pleasant enough - that ecm run isn’t overly hot, probably 23/24c maxes - but more than decent for mid September. We need a southerly now for some proper heat, the longer hours of darkness and decreasing sun angle really curbing daytime heating. That setup with a strong ridge and good 850s a couple of months back would probably be high 20s.

Edited by mb018538
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6 minutes ago, damianslaw said:

Quiet in here today, as said September the quiet month, always hard to get enthusiastic and excited by September weather.

Hardly surprising when it’s wet and windy for many. Little hope of August heat or the first October frost. Tentative signs though of some settled weather next week, especially across the south. May not be long lasting though...

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Tonight’s Euro was largely the same as the morning with a likely milder, drier and duller than average westerly outlook until day 9.

GFS more exciting but less likely to be the result.

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No dramatic improvement generally in the pipeline as the Atlantic high ebbs and flows and the changing wavelengths make the troughing rather more notable than the ridging for n Europe 

Edited by bluearmy
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1 hour ago, Steve Murr said:

Morning -

After a brief settled spell the ECM introduces the first -4c of the season to the UK

36D7E7C4-8FBC-4716-8801-E5A36BB7670E.thumb.png.5d39d6035cb591972f2bfd5583983d05.png

I’ve noticed on the last few ECM op runs towards the end of some kind of Northerly flow with -4 uppers getting into Scotland. 

CC460FDF-2D85-471E-B67E-53FBE78444A4.png

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Looking at the ECM 0z ensemble mean there’s certainly some settled and warmer weather indicated across the south at least during next week!..😜

F8E30613-DC88-4003-9BEC-0C5D258A4D9B.thumb.gif.6f223ca2ee02e34e0003606d8b1beadd.gif0097FEF2-2372-4DE4-83F8-D2193657D6C6.thumb.gif.407baa4b38a0f5f511035154fc9d2d16.gif422D5482-9492-46AD-B9B3-B3D64C0F5925.thumb.gif.aca07a9a54a90625ea999e32c507eefa.gifFAF56395-40A5-4D8A-86FC-F5A81503A5AC.thumb.gif.8b4aae63b767d2b6c76d06a88574aff0.gif

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Re post Tamara, perhaps I should have clarified, I don't believe we should avoid taking an interest in the weather in September, or that likely synoptics developments have no interest. It was more a personal statement on my perceptions of September, our most benign month, absolute extremes in condition and feel of things reaches its annual low. We can see temps in 30s still, significant wind storms as well, but they wont pack the same punch as they would in summer or other autumn and winter months generally in other words cant feel maximum effect in September.

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ECM clusters - after an above average week with temps back in the mid 20s for a while, next weekend needs keeping an eye on. A really deep low looks a strong possibility, and if cluster 2 holds the eventual outcome, then a very windy, even stormy weekend could materialise

ec-ens_nat_z500scenarios_2020090300_204.

Further out - still the chance that we could draw heat back up from the south but unlikely I would wager - note how many clusters have a trough anomaly over Europe - this usually prevents warm air circulating from the SW, though it could possibly introduce warm air from the east if the draw comes from the Mediterranean - touch and go because we are rapidly approaching the time of year when easterlies flip into colder solutions, and potentially much colder ones. 

ec-ens_nat_z500scenarios_2020090300_300.

Overall, though, I'm sensing a much more active Atlantic than usual for September - a slightly displaced jet to the north means most of the unsettled weather is staying north in the next week, and our chances of settled weather will continue to rely on a northerly tracking jet for the foreseeable - any southerly correction will put us in a wet/windy cycle.

 

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I think there’s an awful lot of uncertainty after the settled but probably not particularly warm spell for the south up to day 6.  T240 has these massively different offerings from ECM and GFS 12z:

705A9861-4368-4C94-8859-9C903069D69E.thumb.gif.c6e0f25408e36b05dfe27443d91cd4d5.gif43E8405C-7F51-43A8-8CB0-D7ABF9A027F8.thumb.png.459698c82d3df6e677aed59fe1fdcc1c.png

My money is on ECM being closer to the mark.

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38 minutes ago, Mike Poole said:

I think there’s an awful lot of uncertainty after the settled but probably not particularly warm spell for the south up to day 6.  T240 has these massively different offerings from ECM and GFS 12z:

705A9861-4368-4C94-8859-9C903069D69E.thumb.gif.c6e0f25408e36b05dfe27443d91cd4d5.gif43E8405C-7F51-43A8-8CB0-D7ABF9A027F8.thumb.png.459698c82d3df6e677aed59fe1fdcc1c.png

My money is on ECM being closer to the mark.

Hi Mike, yes difficult to be precise with low tracking that far out. Certainly, both models showing classic Rossby wave formations profile along the NH jet. Looks like a fluid period developing with fluctuations between cold and warmer. The positioning of the NW European trough being the main influence in the weather type likely to be experienced but no settled or unsettled period likely to dominate. Probably work out towards normal temps .

C

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Much of this uncertainty is down to Typhoon Maysak throwing a massive ripple into the Pacific jet - this then builds a huge ridge in the western USA, a big trough through the centre (hence Colorado going from 38c to 0c within 3 days), with the whole wave travelling further downstream and also effecting Atlantic patterns. It’s that time of year when anything can happen!

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Hi gang not been posting much lately but still having a catch up, and good to see the standard still remains very high. 

Quick one on tonights EC weeklies... Next week we have High Pressure bringing some decent conditions at times and especially further South, towards next weekend we need to keep an eye on a deep Low situated to the NE bringing some potentially much cooler and wetter conditions... Into the following week things look to improve again with High Pressure again building in from the SW.. so all in all some very usable conditions to look forward to over the next couple of weeks.. Enjoy your evenings. 🍺

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Some movement to a consensus this evening with the Euro and GFS having the trough move in at day 8 and removing the milder westerly flow in favour of polar maritime air.

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