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


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1 hour ago, Mike Poole said:

Sorry for self quote, but just for the charts yesterday T120, compare today T96 re track of the low:

60727E93-4110-4361-83F1-5B518F1FDBBC.thumb.png.51ac513b292b5333d903ea3d9805fdb6.png0B036429-B8D0-4642-A6F5-51D3350FD387.thumb.gif.1e9d5c6625e809197c86eec0d746d432.gif51F12DAB-D4BC-4D16-AA62-8661D048B86F.thumb.gif.677d26984c3fd30452084fafbbf57704.gifDBA282D5-80DA-4AFF-8E4B-948AFF1FE9FC.thumb.png.de2652d8af56e15dcad9163b229192ba.png

Low deepest on ECM and UKMO, but will somewhat fill before it impacts the UK.

Moving on with ECM:

67422792-208A-4398-98CF-9A00465D7949.thumb.gif.325e143d2623f25914722c2c074c0b28.gif68561E5D-767B-4C9A-8289-F5CCF48380D8.thumb.gif.209042a275bb5debfc74d761018bdc3e.gif24BFCCD7-42E2-475A-86ED-5FE1EA58DE91.thumb.gif.b6e98cfa5075993451f2c001473272c2.gif

T120-168 returns the south at least to something more seasonal....

 

 

I was waiting for the ecm to come out tonight got stuck on 120 hours for what seemed ages so I gave up in the end . 

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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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Here in Lincolnshire we seem to have been stuck in a cycle since March with good weather in the last week of the month and first week of the next followed by poor weather for the rest of the period. This month is no exception and I wonder if we will have the same outcome at the end of august and first week of September. One thing is for sure it’s been consistent and easy to plan outdoor tasks in advance.

 

LO

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53 minutes ago, Captain Shortwave said:

Despite the rather cyclonic conditions forecast for the coming week. Temperatures will probably do okay with a fair amount of warm air around. Also the combination of those will mean that there will be some pretty hefty showers around away from the fronts that will move through during Wednesday.

Week 2 however does look pretty flat unfortunately.

image.thumb.gif.12c775eefe774c12f26dfc303f2798b9.gifimage.thumb.gif.1e5b91f92cc53b9dcf36f78dfda23994.gif   
 

The dominant trough to the north east isn’t going to be helpful.

Not only super flat, but slightly further south than normal, I detect.

Never say never with forecasts beyond D8, but it will be very difficult to conjure up a warm end to August based upon what we've seen modelled in the past 72 hours.

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9 hours ago, Man With Beard said:

Not only super flat, but slightly further south than normal, I detect.

Never say never with forecasts beyond D8, but it will be very difficult to conjure up a warm end to August based upon what we've seen modelled in the past 72 hours.

It's been on the cards for a week now to be honest. Once this pattern started to dig in, there wasn't going to be any quick route out.

With the Atlantic hurricane basin expected to go into hyper drive over the next fortnight though, there's a good chance some tropical remnants could end up in the mid latitudes again. Hasn't helped us this week with Kyle, but could set up a wave break more favourable for the UK. Other than that, it's as you were. Changeable, and a bit fresher after the humidity goes at the end of the week.

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10 hours ago, Lincs Observation said:

Here in Lincolnshire we seem to have been stuck in a cycle since March with good weather in the last week of the month and first week of the next followed by poor weather for the rest of the period. This month is no exception and I wonder if we will have the same outcome at the end of august and first week of September. One thing is for sure it’s been consistent and easy to plan outdoor tasks in advance.

 

LO

You had "poor" weather through mid April and (especialy) May?

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Seems like its the beginning of Autumn this week, low angled Jet, low pressures approaching from the west and the heavy convective rainfall many have had (obviously not here) being swapped for more generalised rain. Again nothing looks particularly settled during the next ten days, some may even struggle to jet 1 or 2 dry days. Low pressure this Thursday & Friday looks like being modelled further & further south east, certainly not a trend I wanted given I'm golfing both days - typical...

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Fairly wet pattern appearing to set up, as alluded to the Jet is south of normal. Both Euro and GFS presenting a significant rain threat towards day 9-10 as they try slow a low but fail meaning that it just ends up directly over the UK.

spacer.png

AAM down to about -1.5 again according to Matt Hugo and the EPS for the rest of the month. 

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EC clusters are out shortly, but in the meantime, I had a look through the individual ECM ensembles at D10 and D15.

At D10, it's pretty brutal, with about 80% having the UK influenced by a significant trough, and many of them introducing a northerly flow keeping temperatures very suppressed particularly in the north.

A better initial prognosis by D15 - as many as 60% of ensembles showing evidence of a renewed burst from the Azores High, and increasing warmth again. This is far too far out to build a forecast upon, but since D15 is September 1st, it wouldn't be too surprising if this came off ;)  

In the meantime, this Thursday may not feel too bad in the areas that avoid the rain:

arpegeuk-31-90-0.png?17-06

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3 hours ago, mb018538 said:

It's been on the cards for a week now to be honest. Once this pattern started to dig in, there wasn't going to be any quick route out.

With the Atlantic hurricane basin expected to go into hyper drive over the next fortnight though, there's a good chance some tropical remnants could end up in the mid latitudes again. Hasn't helped us this week with Kyle, but could set up a wave break more favourable for the UK. Other than that, it's as you were. Changeable, and a bit fresher after the humidity goes at the end of the week.

Yes is there a reason why tropical developments scupper August but can help September? It seems if we get a settled spell in September, it's because an ex hurricane has helped suck the Azores High further north than normal, but if one comes along in August, it interrupts the general settled theme and we end up with a whole pattern change. Makes you wonder what output we could be seeing without the interference of the tropics.

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48 minutes ago, Man With Beard said:

EC clusters are out shortly, but in the meantime, I had a look through the individual ECM ensembles at D10 and D15.

At D10, it's pretty brutal, with about 80% having the UK influenced by a significant trough, and many of them introducing a northerly flow keeping temperatures very suppressed particularly in the north.

A better initial prognosis by D15 - as many as 60% of ensembles showing evidence of a renewed burst from the Azores High, and increasing warmth again. This is far too far out to build a forecast upon, but since D15 is September 1st, it wouldn't be too surprising if this came off ;)  

yep, these clusters tie in with that:

ec-ens_nat_z500scenarios_2020081700_240.

ec-ens_nat_z500scenarios_2020081700_348.

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2 hours ago, Lincs Observation said:

Yes as in every month since March but as I say punctuated by two weeks of glorious weather at the end and start of the months since.

LO

How so? April and May were amazing. Even in Lincolnshire, surely May was as sunny and beautiful as everywhere else? It was sunnier than most summer months on record too!

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Understandably it's very quiet in here at the moment- no great prospects for any prolonged settled weather being shown by any of the models.

However,  it's certainly not going to be cold over the next few days. In between the showers it's likely to feel warm and night time temps look like remaining quite high. Even in the rain it should feel fairly warm for most of this week.

Another thing I'm noticing is the difficulty the cooler North Atlantic air is having making it to our shores- even towards the weekend and beyond. Plenty of warm to very warm air remaining close to the UK which allows the possibility of the odd warm, sunny day here and there.

 

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Evening all 🙂

As last week's heat recedes into memory and folklore, where are we in the second half of August, a time which can be quite poor weather wise before the settled conditions return just in time for the start of the school year (anecdotal);

ECM1-192.GIF?17-0gfs-0-192.png?12gens-0-1-192.pnggem-0-192.png?12

That's T+192 on the 12Z Output from ECM, GFS OP, GFS Control and GEM and if I'm being all honest all pretty much of a muchness. Control offers a hint of something drier and warmer for the SE but otherwise it's encroaching Atlantic LP bringing cloud and rain. It's a fairly shallow feature unlike this week's depression so no real issues with gales.

Looking further ahead to month end, a hint from GFS OP the Azores HP will shift NE and force the jet back north but that's a very long way off (though wouldn't be a great surprise).

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26 minutes ago, stodge said:

Evening all 🙂

As last week's heat recedes into memory and folklore, where are we in the second half of August, a time which can be quite poor weather wise before the settled conditions return just in time for the start of the school year (anecdotal);

ECM1-192.GIF?17-0gfs-0-192.png?12gens-0-1-192.pnggem-0-192.png?12

That's T+192 on the 12Z Output from ECM, GFS OP, GFS Control and GEM and if I'm being all honest all pretty much of a muchness. Control offers a hint of something drier and warmer for the SE but otherwise it's encroaching Atlantic LP bringing cloud and rain. It's a fairly shallow feature unlike this week's depression so no real issues with gales.

Looking further ahead to month end, a hint from GFS OP the Azores HP will shift NE and force the jet back north but that's a very long way off (though wouldn't be a great surprise).

Aye, normally 2nd half of August pure autumn, but last year, was unusually hot, wasn't it hottest Aug BH on record

gfs-2019082600-0-6.pnggfs-2019082700-0-6.png

 

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Further cursory glancing at the models over recent days, looking like August will be a very contrasting month, first half exceptionally warm, though not especially dry overall, second half much more unsettled with temps near average. A significant pattern change has occurred and the jet has moved south, leaving the UK exposed to low pressure, rather slow moving as well, with modest heights to the north locking the trough in place.

Not a complete washout, temporary ridge development at times will bring drier quite pleasant conditions. 

I too would not at all be surprised to see the azores high return just in time for September, seems an annual feature - early September being on average probably our most likely time for quiet settled pleasant weather. However, this year the hurricane season is forecast to be a lively one, and sudden about turns in tropical storm development will keep us on our toes.

 

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23 minutes ago, damianslaw said:

Further cursory glancing at the models over recent days, looking like August will be a very contrasting month, first half exceptionally warm, though not especially dry overall, second half much more unsettled with temps near average. A significant pattern change has occurred and the jet has moved south, leaving the UK exposed to low pressure, rather slow moving as well, with modest heights to the north locking the trough in place.

Not a complete washout, temporary ridge development at times will bring drier quite pleasant conditions. 

I too would not at all be surprised to see the azores high return just in time for September, seems an annual feature - early September being on average probably our most likely time for quiet settled pleasant weather. However, this year the hurricane season is forecast to be a lively one, and sudden about turns in tropical storm development will keep us on our toes.

 

Indeed - the trajectory of ex-hurricanes causes all kinds of problems as we know.

At the moment, while Hurricane Genevieve looks to become a major storm in the Pacific (not a threat to land in itself but likely to bring tropical storm force winds and swells to Baja California), there are a couple of waves in the Atlantic with the one nearer the African coast looking the more likely to develop into a significant feature by the end of the week.

IF we get ex-hurricanes moving out into the Atlantic from eastern Canada they usually prop up the Azores HP and keep the jet to the north. What we don't want is a more southerly recurving bringing the storm remnants closer to the UK as they can have large amounts of rain in the circulation.

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For the last two years we've become used to September having a settled first half, and unsettled second half. 2017 was cold and wet, 2016 a month of two halves but unsettled throughout, 2015 settled first and final third with very unsettled conditions in the middle third, 2014 very settled throughout, 2013 changeable and cool... It can be quite an interesting month with last peaks of warmth as well as the first chilly nights and often the first gales. The Atlantic often kicks up a gear in late August / September so as long as the jet is to the north of the UK, we may strike lucky with a final warm settled spell in the first week of the new month... who knows.

In the short term, let's see how the low (already watered down from before) later in the week behaves. A ridge building behind would be helpful.

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5 minutes ago, Scorcher said:

I seem to recall a very notable hot, settled spell around the middle of the month in 2016?

Indeed, for about 3 days. Lots of thunderstorms around too.

On the subject of heat - GFS 18Z FI:

h850t850eu.png

 

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Looking way ahead, the last two eps clusters have raised height anoms across the Atlantic and w Europe at the back end of the past few runs which ties in with general EC46 continuity and consequently a pleasant start to September ......

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No sign of anything settled from the NOAA 500mb charts which retain low pressure domination and an upper flow north of west. The current GFS and ECM are pretty much bang on imho, detail to be determined of course , but cool, unsettled, showery would be the general pattern for the timeframe 6-14 day and possibly beyond? https://www.cpc.ncep.noaa.gov/products/predictions/610day/500mb.php
 

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Weather seems to have gone into full blown 'Payback' mode for our week long heatwave, the current model output  really would be at home in the middle of October, low angled jet and low pressures barrelling across the UK. Away from the south coast many places have seen a lot  of rain at times this month despite the heat. Wouldn't take much for flooding to become a problem with the outlook. Hoping the things can sort themselves out for the late bank holiday. 

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ECM looks fairly quiet in the 8-10 day period, with a little bit of rain passing through. Before we get there, Wednesday and Thursday look quite wet in western areas. Driest in the east, best and warmest conditions in the SE corner as usual. Thursday could be quite warm.

image.thumb.png.ae9628222debc400fb916a888166f420.pngimage.thumb.png.69cf5af4c81a48131f42d2242633a90f.png



Perhaps some tentative signs of an improvement right at the end of the month after a good week of having nothing to look out for?

A few runs having a go at building the Azores high in to varying degrees sometime between 10-15 days away. One to watch:

image.thumb.png.19d4e1ed726240304be047b76e2276e5.pngimage.thumb.png.75442ab5a949e42bc3c0a12872cb2515.pngimage.thumb.png.8635a2e71b85404efe3cf434b8d2bf9f.pngimage.thumb.png.6c4253685b3fd15dbd783023de21d37b.png


 

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