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


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Back from the storms thread ....... it seems the fleeting upper ridge at day 5/6 is August’s last hurrah at sustaining some summer conditions ......can a sceuro upper ridge develop to hold back the Atlantic trough ?  Seems a forlorn hope now and the last third of August will likely be a reversal of the first half .....

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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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2 minutes ago, bluearmy said:

Back from the storms thread ....... it seems the fleeting upper ridge at day 5/6 is August’s last hurrah at sustaining some summer conditions ......can a sceuro upper ridge develop to hold back the Atlantic trough ?  Seems a forlorn hope now and the last third of August will likely be a reversal of the first half .....

Doesn't look likely:

image.thumb.png.1a7ef80f89757c37184660610009af9d.png
Jet roaring back into action after a couple of weeks of being subdued:

image.thumb.png.691085a0475785863add39c5d913cccf.png

Back to upper ridge over the pole and UK troughing:
image.thumb.png.99bfccd716cd47a818075ceff4016b90.png



Strongest -ve AO of the summer setting up too:

image.thumb.png.07616292f5b20dab8563862b6d279447.png

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1 hour ago, mb018538 said:

Funny how when an unsettled pattern emerges it gets nailed time and again...

GFS/GEM/ICON charts for next Friday:

image.thumb.png.890d6b2269eff8058999c54b2a4acce2.pngimage.thumb.png.8318b3fc9be265194ca4893d8108cb49.pngimage.thumb.png.56e8e77f04597c4a9e0405ff884360fb.png


UKMO only goes to 144, but looks to be headed the same way:

image.thumb.png.e081f36d9acaa84edb22c390698ba7dc.png

The next 10 days looking fairly wet wherever you are in the UK< but with more emphasis in the west:

image.thumb.png.7e17f27f84223f53f66e38870220c9ba.png

I'm saving that rainfall total chart for posterity, west central Scotland forecast to be the driest place in the UK over the next 10 days.

Unheard of 😁

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20 hours ago, mushymanrob said:

Id call that (for t240) pretty good agreement , and IF the mean upper trough continues its Eastward progress then itll become decidedly cool and fresh in the run up to the Bank Holiday weekend. Maybe a ridge will follow thats exit and build in time for the BH ?

 

gfs cool.png

ecm cool 1.png

814day.03 cool.gif

Yes Mushy.. Looks pretty unsettled for the the next 10 day's or so... Last night's EC46 agrees with your thinking as well... Definitely signs of a marked improvement come the Bank Holiday, with a High Pressure extending from the SW to bring dare I say it... A warm and fine Holiday period... Fingers crossed. 

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Right folks a little bit of cheer from me this morning, don't get to down about the conditions becoming more unsettled over the next week or so. Last night's EC weeklies were pretty positive, especially for the South come the end of the month, High Pressure is ridging nicely at times, and this pattern continues to hold into Mid September. There will be a risk of more unsettled conditions towards the NW at times, but there looks to be a decent amount of settled and at times warm conditions for many. I was almost expecting to see a barrage of lows spreading West to East, but it's not the case.. Perhaps a chance to take a late Summer break if this comes off. So all in all, the longer term outlook remains pretty positive. Enjoy your Weekends. ☀️👍

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Oh dear...i dont usually use these charts, tbh i dont care for them much as they seem to alter too swiftly to get a firm grip on what the most likely upper pattern may be, but these charts are pretty dreadful for summer weather likers... they smack more of winter then even autumn.. just look at the air source, polar! In winter we could get snow showers off this, pretty heavy ones in the West too...a bit like last February..

 

dreadful.gif

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13 hours ago, 38.7°C said:

Does the lack of comments in here tonight give you a clue? ? 

I thought it wasn’t good but i also wasn’t sure if it was quite because everyone was enjoying the weather yesterday 

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26 minutes ago, mushymanrob said:

Oh dear...i dont usually use these charts, tbh i dont care for them much as they seem to alter too swiftly to get a firm grip on what the most likely upper pattern may be, but these charts are pretty dreadful for summer weather likers... they smack more of winter then even autumn.. just look at the air source, polar! In winter we could get snow showers off this, pretty heavy ones in the West too...a bit like last February..

 

dreadful.gif

Yep, I use them with the Noaa outputs, together, if all 3 are consistent with themselves and each other over 3 days then its probably about 80% likely that the actual upper air will be pretty similar to them.

Quite a change by, perhaps, before next weekend, no heat, plenty of ppn likely, could be windy at times in exposed western coastal areas with lows being rather frequent visitors!

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ECM Clusters today - I had been following the small chance of a mini-plume next Thurs/Fri, but I think the chance of any noteworthy heat last next week has diminshed, not increased. The T144 and T168 clusters don't allow enough time for hotter air to work northwards before the Atlantic trough shows its full force for the UK, and I doubt we'd seen any more than one slightly warmer day in eastern areas. 

ec-ens_nat_z500scenarios_2020081400_144.  ec-ens_nat_z500scenarios_2020081400_168.

Further out, I'd expect rain and wind on regular occasions based upon charts like this (D12). Again, might scrape a warmer day in the SE at times. The whole D11-D15 is fairly similar to this, btw...

ec-ens_nat_z500scenarios_2020081400_300.

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26 minutes ago, JON SNOW said:

Hey Gang, I’m not the sharpest tool in the box / drawer / shed..whatever...as most of you probably know already..jeez I’m so modest!😉:shok:...BUT..I do know an early taste of autumn when I see one and there is emphatic support from the models so far today and in this case the ECM 0z ensemble mean to support it.,and I take absolutely no perverse satisfaction in saying that an early taste of autumn during late August is currently the form horse! 🐴 😜
3A5766F3-9B49-4123-8358-A7C1527302DB.thumb.gif.082b8bf4a976c3d8b7efda033825a5c5.gif4BB7370C-8F8D-4EB2-B57E-73CF564F2404.thumb.gif.9b6004b1ee8000023c0a3e1ae85a79fd.gif

 

I'm not sure I agree mate.. I don't think the models have come to grasps with the current situation right now. We are living in unprecedented times don't forget. And as tams would say its the background drivers that lead the models, and those drivers are a little out of soughts right now. 

I would agree its becoming more changeable over the coming days, but I feel perhaps things will Improve towards the end of the month and 1st part of September! And let's not forget there is still plenty of time for some decent Heat to manifest. If I'm proven wrong mate I will send some Champagne your way, and likewise you can return the favour... 🍻😂

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28 minutes ago, mb018538 said:

92743798-5A42-4846-ABA8-E2185D24DD39.thumb.png.c8e6526a45b96cb2cebfd4ecaf5b1dc5.png

Here comes trouble...

Oh no 🤦🏼‍♂️. Broad agreement too , Bring back the heat please . That’s Gem , Ukmo and Gfs at 144hrs 

BDD9B929-3500-44CF-BE47-F61A346F1DFE.png

191DCB25-4EDC-4DE6-883E-72D793A9556A.png

B52A6B72-F34B-4D58-BD61-99D1CBC0929A.gif

Edited by Mark wheeler
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How very unseasonal for the time of year, and a real kick in the teeth. If only we could do a turnaround like this:

archives-2016-8-19-12-0.png to archives-2016-8-23-12-0.png

Lots to happen before then so hopefully it will get downgraded nearer the time.

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Ecm deepened that Atlantic low on the 00z and seemed a bit lonely .....it isn’t now although the law of sod says it will tone it down on its 12z output ! 

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1 hour ago, MP-R said:

How very unseasonal for the time of year, and a real kick in the teeth. If only we could do a turnaround like this:

archives-2016-8-19-12-0.png to archives-2016-8-23-12-0.png

Lots to happen before then so hopefully it will get downgraded nearer the time.

Certainly hope so harvest not started yet so P.H.T. (pre harvest tension)  will be through the roof with those charts.

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I’ve said in past to much animosity UKMO is not that reliable at day 6 it’s gone from most settled to most autumnal. It seems actually GFS has done best with picking this up?

467C8FAD-A78B-408F-93A9-D9EC960316A8.thumb.jpeg.73ccce627246b11e42e1fda11bc44225.jpeg

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Well, that was the heat that was (as someone never said).

After seven days of daily maxima of above 30c in East London, back to 21c today and a welcome respite though humidity has returned with a vengeance.

Looking ahead to the next four days with the 12Z Arpege:

arpegeuk-41-27-0.png?14-17arpegeuk-41-51-0.png?14-18arpegeuk-41-75-0.png?14-18arpegeuk-41-99-0.png?14-18

As we've seen forecasted for a while, the last of the warmthis driven further north and west tomorrow with a cooler stretch and then the first sign of a return of warmer air back across the SE which we see on Sunday with 25-27c forecast. That all gets swept away with a cool day Monday and a modest recovery on Tuesday.

arpegeuk-2-27-0.png?14-17arpegeuk-2-51-0.png?14-18arpegeuk-2-72-0.png?14-18arpegeuk-2-96-0.png?14-18

The 500HPA charts tell the story. Tomorrow we see the E'ly pattern move further north so the sheltered west and NW of England is the palce to be but note also the onshore flow in the SE replaced by a weak offshore flow so the recovery in temperatures on Sunday but likely to be accompanied, you'd think, by a return of heavy showers or storms. By Monday an Atlantic sourced flow has re-established bringing in cooler air but note on Tuesday it's a TM air source so the longer passage across the land allows the SE to get the warmest of the conditions.

It doesn't likely from the 12Z suite any Atlantic LP will stall in situ to the west of the British isles and allow a return of hot air from Iberia but if, as GFS OP suggests, the LP moves more NE, there would be a brief push of warmer TM air across southern and south eastern parts before the cold front sweeps the PM airmass back. 

 

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