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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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ECM and JMA not interested in the plume scenario at T192, but a more organised move of high pressure towards our islands, take that too, its better than the current dross, overall good output tonight...

923A6C6A-CFA9-48B9-B2F8-AD9E2D51A0E1.thumb.gif.ec3eec4ed41dce1f1cd3c9ee25f46330.gif58CD01D7-CB10-4107-BC97-8F02BE86C190.thumb.gif.591f5c2106535d8f6fcabbc1da9b93dc.gif

Edit, ECM should settle things down!

DB376E90-C876-4517-8C0C-2E2586D8D941.thumb.gif.ad4e04607f658c7b0ef13fcb152b1fb0.gif

Edited by Mike Poole
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12 minutes ago, Mike Poole said:

ECM mean T144, T168, T192:

A2704753-D44E-4DE8-856C-6455B8456B01.thumb.gif.b844803a7ad84e45f637b8b1fbd9580b.gifDA9471B2-B6C1-4E89-AA34-320CD8A07642.thumb.gif.9edd5fc65a852ed0c8840bd23bfaffa6.gif4BD14175-66FA-4D48-BF0E-2492168EA7E9.thumb.gif.ac46d2076d1c94d954373354465533ee.gif

I think the plume scenario is a dud, but the UK high is looking increasingly more likely as per ECM op run.  I’ll take that, it will be nice to see some September sun!

No plume in the mighty Navgem either . Looks ok though .This is the final chart .

562597B8-EF19-43E3-B782-B37CB3DA9A71.png

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Yep, at D9, 70% of ecm ensembles spill over an Atlantic ridge before a plume gets a foothold. Usually the threshold value for a forecast. Fine weather = yes, hot weather = not likely.

ec-ens_nat_z500scenarios_2020082812_204.

Edited by Man With Beard
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ECM does appear to show a change from low pressure influence to dominant high pressure over six days from Wednesday......

  96A66F4A-C0CA-42BD-9BBC-9D10C0CD7F53.thumb.gif.1f1375edf52545edc06f7ce552e49589.gif

This would allow a period of settled weather so let’s cross our fingers that it happens!

 

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57 minutes ago, mb018538 said:


Here comes high pressure (so says ecm and gem):

CAEB0977-848C-4955-BDCF-CF93B911EE8F.thumb.png.85c571b544131372bbf810095a0641cc.png815302DC-DE75-40C6-AF0F-F3415DA14DC7.thumb.png.35ee02e85c4bbe47c700ed550b4767a1.png
 

GFS not keen - though the op is an outlier:

97CB7F6C-B434-4192-B7B3-1F05151ECEA0.thumb.png.509524b48537eae38367492d1a970eb9.png

Id have thought the GFS is closer to the mark if these charts are right, but i do like the hints of the positive pressure anomaly in the Western Atlantic progressing towards us. IF that continues then a decent settled spell in time for mid month?

 

hope0.gif

hope.gif

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1 hour ago, mushymanrob said:

Id have thought the GFS is closer to the mark if these charts are right, but i do like the hints of the positive pressure anomaly in the Western Atlantic progressing towards us. IF that continues then a decent settled spell in time for mid month?

 

hope0.gif

hope.gif

11CFA4B2-2130-492D-995C-716B9C799074.thumb.png.55ba056ccdb898024d15f62413244e29.png1E6D0604-2072-4A85-B755-A4A913E771A0.thumb.png.4454ad4c621fa224c3073fa58f60e11b.png
 

Quite possibly - the ecm op was a big outlier too this morning....just the opposite way to the gfs!

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46 minutes ago, Man With Beard said:

Clusters 00Z run for D10 - looking good for a UK high - should feel pleasantly warm - outside chance of southerly draw.

ec-ens_nat_z500scenarios_2020082900_240.

Yes,looks dry mid term,infact,hardly any rain forecast for Manchester for the next 10 days!!

 

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2 hours ago, mb018538 said:

11CFA4B2-2130-492D-995C-716B9C799074.thumb.png.55ba056ccdb898024d15f62413244e29.png1E6D0604-2072-4A85-B755-A4A913E771A0.thumb.png.4454ad4c621fa224c3073fa58f60e11b.png
 

Quite possibly - the ecm op was a big outlier too this morning....just the opposite way to the gfs!

Take the mean of them all and I'd be happy. (Self interest at play here as I have a south coast holiday coming up)

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2 hours ago, northwestsnow said:

Yes,looks dry mid term,infact,hardly any rain forecast for Manchester for the next 10 days!!

 

We certainly need some dry days. Today is just atrocious for August. Just started raining here and feels genuinely cold. These conditions can wait until late October at the very earliest.

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1 minute ago, Scorcher said:

We certainly need some dry days. Today is just atrocious for August. Just started raining here and feels genuinely cold. These conditions can wait until late October at the very earliest.

I know. What happened to the forecast for a dry sunny weekend?

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1 minute ago, East Lancs Rain said:

I know. What happened to the forecast for a dry sunny weekend?

Just horrible. Again, another example of the Netweather myth about northerly airflows being dry and clear. Most of the time polar air brings with it cloudy skies and a genuinely unpleasant feel.

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2 hours ago, Scorcher said:

Just horrible. Again, another example of the Netweather myth about northerly airflows being dry and clear. Most of the time polar air brings with it cloudy skies and a genuinely unpleasant feel.

Echo that - been 14c and miserable all day here. Rubbish.

12z op runs aren’t up to much - none showing high pressure moving in. I think if we’re presented with 2 scenarios at this juncture, we all know what will win.

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2 hours ago, Scorcher said:

Just horrible. Again, another example of the Netweather myth about northerly airflows being dry and clear. Most of the time polar air brings with it cloudy skies and a genuinely unpleasant feel.

not myth from late Nov to late Jan here, northerlies are dry and clear (wishbone effect) sun too weak for inland convection, rain/sleet/snow showers down west and east coasts, this area poor for snow in direct northerly, setups that create Pembrokeshire Danglers,

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ECM going against the grain of the other 12z suite as far as I can see, and builds in the UK high as per some of the 0z and yesterday’s 12z suite.  Not done and dusted this, by any means:

anim_npd9.gif

 

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1 hour ago, Mike Poole said:

ECM going against the grain of the other 12z suite as far as I can see, and builds in the UK high as per some of the 0z and yesterday’s 12z suite.  Not done and dusted this, by any means:

anim_npd9.gif

 

Well definitely not, no. One of the most reliable models is consistently showing a build of pressure and a potentially sustained period of warm, settled weather. Another shows an improvement but we can't see beyond 6 days. The NOAA anomaly charts are promising and show a significant positive anomaly close to us or over us during the next 14 days. Meanwhile, Tamara has outlined a series of factors that support not only a much improved spell of weather, but which also undermine some models' attempts at a rapid breakdown. 

I'm surprised at the lack of activity in here and the lukewarm chatter of a possible warm up towards mid month - from tomorrow it starts to look much better for the South and within a week there is a real prospect of widespread warmth and sunshine...

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Thanks for another informative post Tamara and good luck with the move. Getting out just before smelly stuff really collides with air-moving machine, I envy you the great weather too!

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ECM mean 12z here, T168 and T240:

43FE15CD-225E-460D-A52B-40098670EC9A.thumb.gif.620bf7e4784c6f4167aea9b69b6e5dca.gif92477041-BE5D-4F41-97D5-3205A5E0A854.thumb.gif.27a9f1d95077166c63ecf1848440a595.gif

This would strongly suggest that the ridge in the Atlantic would build over the UK over the next 10 days, with 1020 over most of UK at day 10.  Clusters will tell us more I would think...

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