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Paul

Model output discussion - summer rolls on

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Looking at the models over the last several weeks you can clearly see the Atlantic is waking up. I think any very warm spells from now on will be fleeting events of between 1 - 3 days or so. Definitely the tell tail signs are there that a change is starting to happen. 1 or 2 more warm spells wouldn't go a miss before the autumn properly sets in. 

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Wow the Ecm 00z goes for another heatwave later next week with +15 T850's meaning temps potentially into the 30's celsius yet again!😀

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Edited by Frosty.

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Well we still have very little clue as to what will happen from this time next week. Broad agreement on a warmer day again for the SE on Sunday with the unsettled weather spreading to all parts early next week.

From then it’s all a bit up in the air. Yesterday’s 12z GFS was showing a more pronounced build of the Azores high into the southern half of the UK, this morning it shows a more westerly flow with only brief ridging into the south. 

ECM on the other hand is much warmer in the extended period than it was yesterday, however it looks quite unstable and thundery towards the end of next week. 

UKMO as ever only goes out to Tuesday, so no clue from that model on how things will pan out mid to late next week. Tuesday itself on the UKMO shows a westerly flow with some sunny spells and a few showers in the south and probably more persistent rain and much cooler air filtering into northern Scotland. 

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Take a look at the 500 mb anomaly charts. They are obviously not surface but will give you an idea on what direction the upper flow is, basically is it a cold or warm flow!

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

not a 'warm' flow for sure and more trough dominated than ridge.

http://www.cpc.ncep.noaa.gov/products/predictions/610day/500mb.php

less marked troughing but little sign of any ridging or even heights building

that is in the 6-10 day period.

The 8-14 also a similar sort of chart.

No sign though of the Atlantic winding up.This does leave probabilities for a day or two at a time with surface ridging but none of the charts shown really gives any solid idea where this might occur. Possibly one over or very close by the UK, maybe the near continent but that is really straw clutching rather than scientific.

No constant deluges and no return in this period to our 'summer'.

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ECM clusters still providing more questions than answers sadly!

As for our building high - I mentioned yesterday it was around 60/40 against....its now 70/30 against:

ec-ens_nat_z500scenarios_2018080800_192.

By day 10 it isn't looking great either:

ec-ens_nat_z500scenarios_2018080800_240.

Clusters after this are a mess. I find the day 10 anomalies strange as they don't really tally with the NOAA anomalies at all?

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The Gfs 6z operational is quite a changeable / unsettled run, especially further north where it also looks generally cool but further south there is some warm drier, brighter spells, occasionally very warm for the s / e and the best part of the run is the end as an anticyclone builds over the uk bringing pleasant surface conditions.

06_372_mslp500.png

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59 minutes ago, Singularity said:

The models have of late become keen to kick off a new MJO propagation from the Indian Ocean in about 10 days time... but this is counter-intuitive, as the Nino state favours a more eastward point of initiation, across the Maritime continent. There's been a slight trend in the modelling toward that, but not yet enough for the models to start capturing the onset of the next Nino-type AAM cycle that occurs as the MJO moves east from that region.

Given the dominance of warm SSTs in the C and E Pacific, I'm inclined to believe that the overall average MJO diagnosis in the H-W plots will actually follow a path very similar to its previous cycle (red line in the plot below), starting from where that cycle was on 6th or 7th July.

diagram_40days_forecast_GEFS_member.gif

So longer-term modelling is in the 'highly suspect' bin for the time being.

 

Before that - in the 4-10 day range - we look to be in a state of modelling chaos as a result of tropical cyclone activity in the Central and East Pacific which is supplying extra convective forcing and nudging the pattern toward a more Nino-like state by an amount that is fraught with uncertainty. This has exceeded model estimations, hence the models slowing down the approach of the weekend trough, and doing so in a pretty inconsistent manner.

This does mean that the timing and path of LP systems next week is totally up in the air. Best to just focus on the weekend details while waiting for the models to get a better handle on things, if you can afford to.

Looks like you will be spot on about the El Nino forcing - total model turnaround in the past couple of days - no Atlantic height rises, instead Atlantic trough / east heights. Of some sort! 

Looks like it will either be unsettled, hot, or fluctuations between the two. 

Edited by Man With Beard

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Probably the most uncertainty we've been dealing with all summer with regards to model fluctuations. Back in late June/early July we were seeing 100% agreement in the ensembles out to day 15! Now it's all over the place. The 6z ensemble isn't much better:

gefsens850london0.png

Fairly good agreement out to day 7, then any number of options from below average, to well above average again. The mean staying above average meaning cooler weather not quite as fancied, but frankly we don't have much idea what we will end up with.

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Improvement on the GFS for Tuesday and Wednesday next week. More pronounced build of high pressure compared to this mornings run:

 

50F780DA-4B2E-46FF-A8F6-9D484F6243BD.png

B36644C4-A68B-4EED-AC08-F09834890394.png

 

The high pressure looks a little more tenuous on the UKMO for Tuesday, but it still ridges in, temporarily at least.

 

 

43624AEF-A897-4E44-B1B2-FFAE46D9861F.png

Edited by danm

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Yes GFS still has the high pressure influence next Friday T204:

image.thumb.jpg.5614e3f63bf6ec80d9708ffa68caa76e.jpg

GEM looks the pick if a return to fine and settled is your thing, ridge building back in at T228 in a way that looks like it will last for longer:

image.thumb.jpg.72a62c7e597d718aca746729e8509356.jpg

ICON meanwhile at the end of the run T180 still looks westerly dominated:

image.thumb.jpg.0e48c022d1bbc588f3baa72538b7a179.jpg

So still quite a bit of uncertainty, given the background signals I still favour a return to warm and settled, the question is how long it takes.

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Well there's some cracking weather developing next week and well into the following week on the Gfs 12z operational further s / e...very warm / hot with reloading high pressure..temps into the high 20's / low 30's celsius..yet again!☺..add to this the fantastic extended outlook from exeter and there could be plenty more hot sunny high pressure in the weeks to come!!😀

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Edited by Frosty.

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5 minutes ago, Frosty. said:

Well there's some cracking weather developing next week and well into the following week on the Gfs 12z operational further s / e...very warm / hot with reloading high pressure..temps into the high 20's / low 30's celsius..yet again!☺

Yep it’s a cracking GFS run from Tuesday onwards for a of portion of the UK. High pressure dominated for the southern half of the UK, extending northwards at times too. 

GEM also excellent. 

Edited by danm

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Yes the Gem 12z turns into an excellent run too..if you like high pressure and warmth!😊

171_mslp500.png

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Still a bit baffled with what's going on but can't be denied - a good majority of runs have it hot for England and Wales at the end of next week, like the GFS

So if someone put a gun to my head today and said "forecast next week to me!" I'd say a bit up and down at the start of the week, hot for 2/3 days SE at the end (north stays changeable), then a front passing through making it fresher for all. A more traditional UK summer: 3 hot days and a thunderstorm :)

 

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Same as the met office models then.They think good chance of hot spells again this month,summer NOT over then despite what some would have you believe!

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Looking through the GEFS 12z there's good support for high pressure to build in next week, there's some beauties in there which bring back fine and very warm / hot weather.☺

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Edited by Frosty.

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ECM T96 - no, surely not, I can't believe my eyes! The ECM is a stones throw from stalling the low into Biscay and building pressure over the top! 

edit: no not quite, my that was close! Could have led to another extended heatwave

Edited by Man With Beard

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ECM T216, going for the ridge to the east, trough in the Atlantic, maybe a few more wiggles to come, awaiting the last frame.

image.thumb.jpg.7d2fcb656dafae9cad01c4d9996e3418.jpg

Heres the T240:

image.thumb.jpg.8b1c4f447294088d80616612fbdee910.jpg

Given the 12s as a set, I'm not sure this is the eventual solution, but promising output tonight overall for a last burst of summer.

Edited by Mike Poole

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Ecm much better tonight - though very different from the 00z. Pretty warm again at times too. Seems we just can’t shake the heat away for long this year!

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Plenty of very warm / hot weather on the Ecm 12z after the next couple of days with uppers generally in the +10 to +15 850's range, at least across most of england and wales!☺

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14 minutes ago, Frosty. said:

Plenty of very warm / hot weather on the Ecm 12z after the next couple of days with uppers generally in the +10 to +15 850's range, at least across most of england and wales!☺

Frosty I wouldn’t say that was a fair assessment of the 850’s. To me it looks very changeable with +12 uppers only briefly flirting with the southeast. A downgrade if it’s oppressive heat your looking for. 

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A lot of uncertainty remains tonight, over when (not, in my opinion, if) the warmer settled weather takes hold again.  GFS parallel, FV3 keeps the westerly flow right through to the end of next week, the this at T264:

image.thumb.jpg.11600e27fd74a4bbc606cc0c19dfd404.jpg

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23 minutes ago, shotski said:

Frosty I wouldn’t say that was a fair assessment of the 850’s. To me it looks very changeable with +12 uppers only briefly flirting with the southeast. A downgrade if it’s oppressive heat your looking for. 

Both GFS and ECM better than this morning’s runs. Not sure how that is a downgrade? The only thing is thst Sunday looks less hot. But overall both runs are an upgrade if you want settled and very warm / hot weather.

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