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Sryan Bruen

Model output discussion for Autumn 2018

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I thought it'd be a good opportunity to open up this model discussion thread for Autumn 2018. To start us off, this morning the models have taken a clear trend to a warm and dry start to September, may even be significantly warm at times. The diagram below is of the GFS 0z ensembles for London. The ensemble mean (white line) is well above the 30 year average (red line) for 850hPa temperatures for early September showing it's going to be quite a warm start to the month and Autumn. Precipitation spikes are very low too. Remember this is for London though and there would be regional variations especially for the rainfall. Nevertheless, looking anticyclonic and warm for early September on this morning's runs.

GFSENS00_52_0_205.png.734a529e733223060ba05d3b16a3f717.png

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12z runs show a real split with the GFS still going for settled conditions whilst the ECM shows a zonal westerly, for early September.

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GFS 18z from last night was absolutely stunning for around next Sunday with a southeasterly flow of air from the continent. The air would be dry, very warm and likely sunny. Would be an excellent start to September if it were to verify. 

gfs-0-192.png.95f59360645c4354b32705375452e9ff.png

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GFS sticking to its guns this morning on a settled start to September but this time, it now shows blocking over Greenland beginning to occur.

352408003_gfs-0-204(5).png.125c221f577f89a3c5857773d98768fd.png

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ECM 0z is westerly but relatively high pressure to the south and east bringing the wind from a southwesterly. It'd be mostly cloudy (away from the south of the UK) and humid with some drizzle to the north and west. Far from a washout but very boring conditions if this were to verify.
475156663_ECM1-168(8).gif.5ce83c658e9a3ac66b4ba0b718544aec.gif

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GFS 12z goes more toward the ECM 0z solution of the humid, cloudy southwesterly for the north and west of the UK being the pattern for start of September. However, high pressure dominant in the south and southeast with the potential for some very warm conditions.

gfs-0-168 (3).png

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GFS, ECM and UKMO all in agreement on a massive extension of high pressure from America to Russia during early September with an easterly flow developing as has been common this year. 

ECMOPEU12_144_1.thumb.png.4305d3919e4d9a65041e059fa7359931.png

UKMOPEU00_144_1.thumb.png.3647080299aa178a7ecf2e761d246542.png

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All models showing this settled start to September with massive anticyclone even the ensemble mean from the GFS and UKMO.

GFSAVGEU06_150_1.png.2eaa044bc2dbaf0878d2190a03cfe7d8.png

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Exceptional levels of high pressure (near record breaking almost for September - 2018 does not stop does it?) still ahead on the outlook from Monday onwards with a very dominant anticyclone being the influence for the UK and Ireland for the end of September. Much higher pressure compared to what we had during the Summer. Signs of retrogression in early October though....

However, beyond the 5-7 day mark we have another cyclone expected to develop mid Atlantic west of the Azores. As we have seen its the storms brewing in this particular area (far enough north to catch the westerlies instead of the easterlies) that have arrived with us. This will likely add large uncertainty into the outlook again as we get closer.

rsz_gfsens12_53_-6_208.png.b657f73ced71368604ff8c0e763de917.png

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Just for a good laugh. Pub run the other night was showing the Atlantic blocked for early October with a potent northerly shot (for early October anyway) and bringing snow to the UK.

Saying that as just for fun, there has been some trend from each of the models for the end of the month into early October to be quite a bit cooler than average.

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42241971_1923937124576297_5390758842147536896_n.jpg.0da495672c9ff13b559a1a718be35a94.jpg

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