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

[MATTWOLVES 3]

Not much to get excited about currently, and good lord it's so quite in here. But have a little patience folks.. Last night's EC46 is looking much more positive come Bank Holiday weekend! High pressure builds in nicely around this time, and guess what, this theme Continues into September.. Looks pretty good.

[Guest]

Modelling in near term needs to watched carefully, ECM, UKMO, ARPEGE all produced small mesoscale features running up the between Cornwall and Ireland producing anything from 70-110mph gusts of wind. GFS doesn't develop this system however and runs an open wave up the Irish sea.

[wellington boot]

I think the NOAA charts are at least somewhat promising. Still showing low pressure over us, but showing signs of migration to NE, plus intensity waning, plus high pressure moving closer day by day.

[Don]

2 hours ago, MATT said:

Not much to get excited about currently, and good lord it's so quite in here. But have a little patience folks.. Last night's EC46 is looking much more positive come Bank Holiday weekend! High pressure builds in nicely around this time, and guess what, this theme Continues into September.. Looks pretty good.

As long as we do not see a repeat of that ghastly heat last week, although a bit late for that now

[mb018538]

As alluded to earlier, convective areas are starting to be forecast to move as we head out of August into September. With AAM potentially rising again, we could potentially see a more settled spell of weather as we turn the page into September. Keep an eye out folks.


 

[Fourty Point Three Degrees]

I have a feeling September will resume where May left off - Warm and dry, perhaps another shot at some heat and thunder before the sun crosses into the Southern Hemisphere on 21st.  

[mushymanrob]

1 hour ago, wellington boot said:

I think the NOAA charts are at least somewhat promising. Still showing low pressure over us, but showing signs of migration to NE, plus intensity waning, plus high pressure moving closer day by day.

Well on the 8-14 day chart there is a very slight suggestion of ridging starting to build in the mid Atlantic, but there is quite a moderate upper flow, so unless that slight ridging builds, theres only transient ridging upwind imho. Ive been watching these all summer and only the last possibility actually grew into a spell of high pressure, that we enjoyed recently, several others failed to build. Maybe IF AAM rises it may lead to another stronger positive pressure build..
 

[Don]

41 minutes ago, mb018538 said:

As alluded to earlier, convective areas are starting to be forecast to move as we head out of August into September. With AAM potentially rising again, we could potentially see a more settled spell of weather as we turn the page into September. Keep an eye out folks.


 

I hate to say it I don’t think the heat is done with us yet

[Frosty.]

Looking towards the very end of August and into the start of September there are encouraging signs that high pressure could have an opportunity to build in, at least across southern u k judging by the GEFS 6z mean!

 

Edited August 18, 2020 by JON SNOW

[MP-R]

Nice summery look to early September lol:

[Man With Beard]

ECM clusters - just for trends of course.

D8/D9 - mainly umbrella type weather, though once heights get into France there's always a chance of better weather spilling into the SE

  

D14/D15 - be aware that the anomalies are matched against September averages from this point, which makes everything look a lot better - best to track where the negative anomaly is to the north - it's a 50/50 split between runs that bring the trough close to the UK and yet more umbrellas at the ready (clusters 1 and 2, though cluster 1 may be a NW/SE split), and runs that keep it far away, leaving the UK more settled (clusters 3, 4, 5 and eventually cluster 6 too).

  

My best guess from that would be same as yesterday's - a renewed pulse from the Azores High looks a reasonable bet as September starts, but questionable if will influence the whole of the UK.

Edited August 18, 2020 by Man With Beard

[johnholmes]

2 hours ago, wellington boot said:

I think the NOAA charts are at least somewhat promising. Still showing low pressure over us, but showing signs of migration to NE, plus intensity waning, plus high pressure moving closer day by day.

Well I must take issue with you re high pressure moving closer by the day.

I know it is each of our interpretations of these charts, as with any, but I cannot see what you suggest. Neither in the 6-10 nor the 8-14. In my view it is best to call the charts, what they are pressure charts at 500 mb, around 18,000 ft up in the atmosphere. Strictly speaking they are not what we usually refer to as 'pressure charts'. I think using that term it is too easy to suggest pressure at 500 mb will be what occurs at the surface; often it won't.

So having said that, the height rises and contours do not shows what you suggest wb in my opinion.

Just to show the charts, first the 6-10:- There is quite a marked, fairly rounded, trough over the UK, and over England and Wales this is quite strong, less so over Scotland. Any height rises are pretty small, over Greenland and Iberia. As an average over the 6-10 day period I would not expect much in the way of settled weather The contour height over mid England/Wales, 564 DM spends a fair amount of time well north of the UK so is not going to be 'warm' and thus neither is the surface temperature, as an average over those days.

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

Turning to the 8-14 chart and it shows even less in the way of any +ve height rises, again with a noticeable trough over the UK. The flow over the Atlantic has a hint, no more than that, of being diffluent. Diffluent flow in the upper atmosphere is a major factor in any surface features running into it to deepen quite a lot. So again, even without this effect, I don't see any real grounds for any change from the 6-10 day pattern. More unsettled than settled as the average and not warm really other than possibly the odd day with a passing surface ridge.

 

I'm not getting at you wb just using your comment to try and explain a little more about how to interpret these charts for new folk.

John

ps just noticed the post from mushy, no major differences with his comment

 

Edited August 18, 2020 by johnholmes
spelling

[Tamara]

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 Indian Ocean. Cue the drop back in angular momentum in progress as this signal re-emerges c/o steeply -ve trending global torques across mountain ranges scrubbing out the recent surge of westerly inertia (the +AAM anomalies that created our downstream heat ridge) within the atmospheric circulation -

 

 

- and hence the programmed re-amplified Pacific and flatter downstream pattern in the outlook as the GWO reflects loss of momentum through phase space with an orbit back through negative tendency Phase eight

 

 

Recent posts have attempted to deal extensively, ahead of time, the suggested problems to come surrounding this next phase of weather, and that period of focus is during the remaining third of August. A period where long term extrapolatory assumptions over the longevity of return to this "default pattern" are prone to be outed with time

As rightly stated by a few people, the coming week still looks relatively warm for quite a few, despite rain around and the increasing cyclonic influences just to the west.  That condenses the "worst" of the pattern switch into the last week or so of August.

This is where the further evolution becomes especially problematic and subject to questioning. How much credence is there in all these "early autumn" prophecies ?

The answer is they are equally prone to be outed as being unduly overstated.

I am not referring to Equatorial Atlantic tropical cyclone/hurricane developments , which are a manifestation of the active African Easterly Waves that develop due to the low frequency tropical standing wave default pattern in that part of the tropics - but much as stressed in previous posts of my own leading up to and during the heatwave - the eastward propagating high frequency tropical convection MJO cycle looks set to continue to be more active heading into September than during the earlier summer when it hit the doldrums and allowed that amplified Pacific wavelength and flat downstream pattern to dictate for several weeks in this part of the Northern Hemisphere.

The signs are that the high frequency signal may once again interrupt the upstream signal and another downstream ridge sequence emerge - eventually cutting off the cooler changeable flat North Atlantic influences. The cluster analysis from @Man With Beard of late has reflected this ultimate evolution, and this trend continues today, mirroring tropical>extra tropical forcing trends in the longer range 

The comments by @johnholmesare correct as ever related to the anomaly charts. Just to add that these also evolve according to numerical modelling interpretation of the signals and so current charts are equally snapshots in time of the period in question and are likely still on the cusp of the extended period they represent. However, coming days should provide greater traction to trends, because as suggested at the start of the post, NWP is somewhat blindsided and preoccupied by the Indian Ocean low frequency tropical signal and likely will perform a mid stream shoal switch - much as they did in late July, once they cotton on to the next eastward progression of the high frequency "mini ENSO cycle".

In short, plenty of scope remaining yet for the few who haven't pressed their bias preference switch from the furnace to the freezer, for further summer-like weather to come . September could become a pleasant and welcome extension of summer in terms of weather type, irrespective of change of season - at least for those of us who would greatly look forward to this weather type

 

[Methuselah]

4 hours ago, mb018538 said:

As alluded to earlier, convective areas are starting to be forecast to move as we head out of August into September. With AAM potentially rising again, we could potentially see a more settled spell of weather as we turn the page into September. Keep an eye out folks.


 

That, to me, would be the best possible scenario, MB: a September reminiscent of 1973 -- with foggy mornings and 26-27C, sunny afternoons...

Nothing annoys me more than cold (but nae cold enough for snow) dank autumnal shi'ite!

[stainesbloke]

52 minutes ago, General Cluster said:

That, to me, would be the best possible scenario, MB: a September reminiscent of 1973 -- with foggy mornings and 26-27C, sunny afternoons...

Nothing annoys me more than cold (but nae cold enough for snow) dank autumnal shi'ite!

Sounds perfect Dank, autumnal shi’te can wait 

[Djdazzle]

1906 anyone? That had a crazy hot spell at the end of August / start of September!

Baby steps at the moment, but always nice to have some hope on the horizon.

[January Snowstorm]

Possible hurricane could hit Ireland tomorrow night! Hurricane as in hurricane winds!

[damianslaw]

Mmm no words on the evening model runs, because well they are showing a preety poor late August outlook, GFS decidedly poor with trough anchored into the UK, southerly tracking jet, cool with it.

Often see such conditions in late August and a switch to something much more settled and warmer when the schools go back!

[Mr Frost]

Evening all 

Hope everyone is well!

Lots going on weather wise in the short-term! 
Tomorrow looks soggy in the South - good drink for the gardens that need it! 

Wednesday 06:00, 12:00 and 15:00

 

Not bad at all in the North - toasty 22C and sunny spells for me. 

Wednesday 15:00

 

Then as @January Snowstorm mentioned above - Storm Ellen arrives overnight! Big time gusts expected - wild Summer weather!

Wednesday 22:00, Thursday 00:00 and Thursday 02:00

If you are in that zone and a lover of extreme weather - enjoy!

August has been a bonkers month for heat, thunderstorms and now wind - fitting way to end Meteorological Summer. 

All the best to you all.

Edited August 18, 2020 by Mr Frost

[Mark wheeler]

We have the opportunity for  a little chink of good weather to my eyes on both the Ecm and Navgem with regards to settled weather not sustained yet but hopefully this comes a little later. It’s not been that bad the past 2 days here actually so looking forward to a final settled spell before the hunt for cold begins in earnest in mid to late October for me anyway . 

[Methuselah]

1 minute ago, Mark wheeler said:

We have the opportunity for  a little chink

Oh come on now, Mark... that's far too racist, for 2020! Sorry mate, I couldn't help it!

[Mark wheeler]

1 hour ago, General Cluster said:

Oh come on now, Mark... that's far too racist, for 2020! Sorry mate, I couldn't help it!

Oh No I’m going to reported now , TBF I thought it might have happened when I posted the Navgem consistently recently but thats acceptable

Edited August 18, 2020 by Mark wheeler

[Methuselah]

3 minutes ago, Mark wheeler said:

Oh No I’m going to reported now , TBF I thought it might have happened when I posted the Navgem consistently recently but that acceptable

I'm sorry, Mark, but I've just watched The Legend of Bruce Lee on Netflix (a truly fantastic 50-part series!) that I think I'll watch again... And, once I've discovered what that's got to do with the weather, I'll let you know. But, just to be on 'the safe side' there was a storm in Hong Kong!

[Mike Poole]

Evening all!

As the medium term is dross, I’m focussing on T240 today.  Here’s the ECM, GEM, GFS and the JMA (T192):

Tentative signs on ECM and GEM that a ridge may push across the UK at day 10, meanwhile the other two are not horrendous, anyway.  If predictions by many including me are for a settled September, worth noting the SST anomaly, here:

Very warm all around the UK.  If settled conditions prevail early September, it will be an extension of summer, I think....

Edited August 18, 2020 by Mike Poole

[Mike Poole]

Pub run starting to latch on to things, T240

T288:

Pressure not that high on the latter chart, but it is an evolution we want to see, some kind of Azores, continent link up.  I think we will be seeing more of this sort of run as we approach September...we will see...