Model Output Discussion - Autumn 2018

[Jordan S]

18 minutes ago, Badgers01 said:

The rain fall potential might be more noteworthy than the wind for some areas such as the Lake District - upwards of 6 inches of rain  from oragraphic forcing off a trailing front stretching all the way back to the southern Atlantic.

Indeed and that is just taking account Friday even more rain is likely during Saturday so flooding may become a worry in certain areas.

[ICE COLD]

A cheeky little Artic blast on the GFS 00z this morning. Yes in FI but still nice to see . 

[mb018538]

ECM ensembles:

Unsettled at day 7:



Odds-on unsettled at day 10, one small clsuter with a ridge:



Staying unsettled out to day 15:



Not much to enjoy out of that lot, unless westerlies, wind and rain float your boat.

[Newberryone]

17 minutes ago, mb018538 said:

ECM ensembles:

Unsettled at day 7:



Odds-on unsettled at day 10, one small clsuter with a ridge:



Staying unsettled out to day 15:



Not much to enjoy out of that lot, unless westerlies, wind and rain float your boat.

I'll settle for this anytime over heights to the south which have been nothing but a borefest for oh so long. Great to finally see the jet digging somewhat further south with lots of mobility promised for the foreseeable. Although with all of that said the overnight Ecm 00z run is not looking quite as unsettled in the latter frames unlike the previous run. 

[Wimbledon88]

9 minutes ago, Newberryone said:

I'll settle for this anytime over heights to the south which have been nothing but a borefest for oh so long. Great to finally see the jet digging somewhat further south with lots of mobility promised for the foreseeable. Although with all of that said the overnight Ecm 00z run is not looking quite as unsettled in the latter frames unlike the previous run. 

Fair play to you for having such radical views on a weather enthusiasts site. 

I've more or less been hounded off the SE thread for such contravesial  opinions. 

[ICE COLD]

And like the GFS 00z the 6z has a plunge from the north in FI . Let's hope they keep on coming . 

[mb018538]

At least by the end of October they have a chance of delivering something! If that's what we're gearing up for, bring it on!

[johnholmes]

The more changeable outlook expending further into England and Wales is following the upper air pattern predicted by the 500 mb anomaly charts. For a week or two now they have oscillated between more ridgy and more troughy for the UK but now seem, over the past few days, to have gone for a more disturbed Atlantic flow. Uncertain though whether, as they have so often for many weeks now, revert back to weather more ridge affected. A wait and see game perhaps?

links as always

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

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

We are of course still well within the Hurricane season so further complications from any residual storms getting out into the N Atlantic will likely throw more uncertainty for several weeks to come.

[Frosty.]

Another Gfs run with a very unsettled / disturbed and chilly late october with a risk of wintry ppn at least on northern hills and always a chance of something much colder and more wintry from the north as the 0z / 6z showed..a different face of autumn and one i would like to see now!❄❄

[Frosty.]

Looking through the GEFS 12z there's plenty of support for a generally unsettled / disturbed and colder atlantic pattern through late october and a sprinkling of wintry possibilities for northern high ground, the most unsettled weather further north but everyone would see more of it than has been the case so far this autumn..I've enjoyed the benign warm sunny weather but I'm hoping for a change to something much colder and stormier during the second half of this month!☺

Edited October 10, 2018 by Frosty.

[Frosty.]

The Ecm 12z is a generally unsettled run with lows chasing each other across the atlantic towards the uk bringing some wet and windy spells and the really warm weather is over after saturday with predominantly colder air and just short-lived milder interludes...proper autumn!!

Edited October 10, 2018 by Frosty.

[Frosty.]

Tonight's Ecm 12z ensemble mean indicates a much more unsettled and significantly colder pattern during mid / late october..good to see! 

[damianslaw]

Models are now shaking off the anticyclonic presence, and instead a resurgent atlantic is being shown, with vigour that we haven't seen since March. Odds on the atlantic winning out against any ridge development increase markedly as we move further into October, so not surprised to see this happening, especially given suggestion of deep cold pooling over NE Canada - which will have the effect of creating marked temp gradient contrasts over NW atlantic firing the jet into gear. The fly in the ointment as I mentioned a few days back is uncertainty regarding any future hurricane developments - these have caused the models a bit of headache this season, the static leslie being a case in point.

After a balmy late taste of summer today, its all change tomorrow, yes south east parts will hold onto warmth until Sunday, but the atlantic is about to pounce and this time is up for a fight it seems. Next week looks predominantly unsettled, and much cooler. Longer term perhaps a southward shift in the jet which will allow some colder air to filter in from the north at times, increasing risk of frost - all very seasonal and normal stuff for latter part of October. 

[BLAST FROM THE PAST]

Models seem to be edging now to a storm  track edging further and further south latter half of Oct affecting more and more of our neck of the woods.  Initially we see the swinging north as it hits the HP domination.....that’s going to change as we see a different animal for the latter half of Autumn.

 

BFTP

[Catacol]

On 09/10/2018 at 18:30, jules216 said:

There is an Eastern Asian mountain torque event happening right now which will flip the pattern in north america that has persisted most of the summer and early autumn courtesy of pacific jet extension and a split jet at eastern side of north america. This may have subsequent effect on the Atlantic jet, unfortunately I am not skilled enough yet to predict what effect these EAMT events have on the long range circulation in our vicinity, for this I desperately need insight from likes of Tamara,GP,Lorenzo or Chionomaniac to explain it in layman terms, unfortunately non of them has posted for long time which is a pity.

 

 

Not quite yet - pressure patterns from around the 12th suggesting the possibility of a trough dropping down to the east of the Euro high and perhaps setting a precondition

Certainly no torque event happening right this moment - Masiello is just getting excited.

If it comes as is possible it will produce +AAM that will help continue the current meridional type circulation. At the moment the most obvious thing to report is that we have some sustained positive relative AAM in pulses, sustaining that meridional jet and more N/S rather than W/E influence.

Way way to early really to draw any conclusions from this as we wait to see just how high Nino may push and just how the trop/strat vortex couples up and any sense of sustained pressure patterns. The current Euro block over Scandy would be good news later in winter for setting a precondition for vortex disruption, but not much point getting too excited about such things until we get to November. Cohen's October snow advance theory is an interesting one to keep an eye on at this time of year, but it isn't really a guarantee of anything. Bottom line - too early to risk any kind of forecast.

 

 

Edited October 10, 2018 by Catacol

[jethro]

2 hours ago, Frosty. said:

Tonight's Ecm 12z ensemble mean indicates a much more unsettled and significantly colder pattern during mid / late october..good to see! 

No, no, no, absolutely not. I'm in no way ready, or even vaguely willing to accept the possibility that I'm going to be cold and wet all day in the near future. The whole lot can clear off, southerly weather can continue for at least another 4 weeks, preferably longer. Cold can come the week before Christmas, at the earliest.

[jules216]

1 hour ago, Catacol said:

Not quite yet - pressure patterns from around the 12th suggesting the possibility of a trough dropping down to the east of the Euro high and perhaps setting a precondition

Certainly no torque event happening right this moment - Masiello is just getting excited.

If it comes as is possible it will produce +AAM that will help continue the current meridional type circulation. At the moment the most obvious thing to report is that we have some sustained positive relative AAM in pulses, sustaining that meridional jet and more N/S rather than W/E influence.

Way way to early really to draw any conclusions from this as we wait to see just how high Nino may push and just how the trop/strat vortex couples up and any sense of sustained pressure patterns. The current Euro block over Scandy would be good news later in winter for setting a precondition for vortex disruption, but not much point getting too excited about such things until we get to November. Cohen's October snow advance theory is an interesting one to keep an eye on at this time of year, but it isn't really a guarantee of anything. Bottom line - too early to risk any kind of forecast.

 

 

Hi Catacol, maybe I understood the GSDM synoptics poorly, but isn't the +GLAAM an indicator that the atmosphere is moving faster then earth spinning,which basically means that the westerlies at mid latitudes are also stronger? I thought that with EAMT event there is a switch from +AAM to -AAM in higher latitudes, thus westerlies weaken and we have more chance of blocking? Also on your first picture above, what do the yellow,red and green color contours equate to between 30 and 60N? Thanks. still learning

Edited October 10, 2018 by jules216
spelling

[Jordan S]

Aside from the stormy weather that  much of Scotland and Ireland will see on Friday from storm Callum there could be a renewed burst of pretty stormy weather effecting further southeast through wales, SouthWest England, the Midlands and Northern England during Saturday not all Models are in agreement but the Icon Model and the Arpege Model seem to think so..

                 Arpege

                       Icon

All in all a very unsettled period of weather over the next few days but for SouthEast England and East Anglia the weather should be relatively calmer and warmer with not much rain before rain possible later Saturday. Rainfall totals will really pick up in the next few days with flooding possible particularly for the West of England and Wales.

[Catacol]

46 minutes ago, jules216 said:

Hi Catacol, maybe I understood the GSDM synoptics poorly, but isn't the +GLAAM an indicator that the atmosphere is moving faster then earth spinning,which basically means that the westerlies at mid latitudes are also stronger? I thought that with EAMT event there is a switch from +AAM to -AAM in higher latitudes, thus westerlies weaken and we have more chance of blocking? Also on your first picture above, what do the yellow,red and green color contours equate to between 30 and 60N? Thanks. still learning

A spike or rising AAM at the tropics will tend to inject a westerly wind burst and help cancel out the trade winds at the equator. This in turn undermines the strength of sub tropical high pressure belts causing them to retreat south. High momentum at the equator is then balanced by lower momentum at higher latitudes. Therefore when we have higher relative momentum readings at the equator it is a decent precondition to blocking at our latitudes as the jet meanders under reduced momentum conditions at our atlantic latitude.

This diagramme does it for me - shows the Hadley Circulation and corresponding balance given to global momentum budgets.

Colour contours on my first image between 30 and 60 degrees tend to represent torques applied by the Tibetan Plateau (at about 30 degrees) and the Rockies (closer to 45 degrees). All mountain ranges can apply torque...but these are the big 2 relevant to the northern hemisphere. 

Edited October 10, 2018 by Catacol

[jules216]

7 hours ago, Catacol said:

A spike or rising AAM at the tropics will tend to inject a westerly wind burst and help cancel out the trade winds at the equator. This in turn undermines the strength of sub tropical high pressure belts causing them to retreat south. High momentum at the equator is then balanced by lower momentum at higher latitudes. Therefore when we have higher relative momentum readings at the equator it is a decent precondition to blocking at our latitudes as the jet meanders under reduced momentum conditions at our atlantic latitude.

This diagramme does it for me - shows the Hadley Circulation and corresponding balance given to global momentum budgets.

Colour contours on my first image between 30 and 60 degrees tend to represent torques applied by the Tibetan Plateau (at about 30 degrees) and the Rockies (closer to 45 degrees). All mountain ranges can apply torque...but these are the big 2 relevant to the northern hemisphere. 

on one of the images you attached - the vertical and zonal integral of relative AAM tendency, the bottom one global tend shows positive  values, it means that we have +AAM tendency? Is it in tropics or everywhere? Wouldn't it be better to differentiate between tropical AAM and subtropical AAM? It could lead me to believe that +AAM in subtropics just enhancez western zonality

[Newberryone]

Exceptionally quiet in here so far today, and understandably so if the overnight Ecm 00z run is to verify. I  remarked yesterday on how the latter frames of the Ecm looked less unsettled and now 24 hours later this overall theme seems to be even gaining further momentum with those dreaded heights to the south very much in evidence later next week. One has of course to factor in the volatility in the models right now owing to the hurricane season, but one also has to take cognizance of the fact we could now more or less be looking at something far less autumnal in nature for the second half of October than was previously envisaged. 

[Newberryone]

14 hours ago, BLAST FROM THE PAST said:

Models seem to be edging now to a storm  track edging further and further south latter half of Oct affecting more and more of our neck of the woods.  Initially we see the swinging north as it hits the HP domination.....that’s going to change as we see a different animal for the latter half of Autumn.

 

BFTP

This was a very brave call BFTP considering the latest Ecm run which I’ve just addressed in my previous post. 

[Frosty.]

A nice very early wintry blast on the Gfs 6z operational with some frosts, ice and for the north especially, some snow..this is a recurring theme of the gfs recently..hope it's right!!!❄❄❄❄

Edited October 11, 2018 by Frosty.

[Jordan S]

5 minutes ago, Frosty. said:

A nice very early wintry blast on the Gfs 6z operational with some frosts, ice and for the north especially, some snow..this is a recurring theme of the gfs recently..hope it's right!!!❄❄❄❄

I issued  my own forecast of what autumn may bring to my friend and mentioned the risk of early snowfall  towards the end of October so the gfs May be on to something.. who knows.

[ItNeverSnowsInWindsor]

Great 6z run! Also backed up somewhat by the MetO