Model Output Discussions 12z 01/09/2016

[Ali1977]

Another good GFS mean in FI, NH PV weakest in the Greenland area which is exactly what we need for chances of cold further down the line.

Lets see if today's EC monthly supports this !!

Edited October 20, 2016 by Ali1977

[Severe Siberian icy blast]

The vortex in absolute tattors on this mornings gfs, a marked move away from yesterday's charts it was chucking out. 

we always get this, the mods pick upon a new signal and completely over react to it then settle down once more and the reality is a much more watered down version of it. 

Still on course for a blocked start to November. . .

[Severe Siberian icy blast]

You can see the models struggling to deal with the affect of the next tropical storm moving north up the coast of America and how this interacts with the Atlantic and which route it takes is vital, if it moves north and joins with the weak vortex segment just west of Greenland it could pull the vortex northwest toward Canada opening the door for the mid Lat high to move north sending WAA into the pole really promoting a strong -NAO signature, however if it doesn't reach southern Greenland and comes straight over the Atlantic then it means a more zonal spell of weather for us, although stil not particularly wet just a more flat approach. Even then think once that tropical storm clears we will move toward a more northerly spell because the vortex still seems vacant from Greenland this year.

[Summer Sun]

ECM shows it turning a good deal milder for a time next week before a cool down again at the end of the month as we pick up an NW'ly flow - warming up for the majority of western Europe too

 

Edited October 20, 2016 by Summer Sun

[Chris.R]

The NHC  are less keen on potential development of the low in the Bahamas today before it merges with a cold front, so perhaps it won't act as a catalyst to the jet as was  suggested yesterday? 

[mb018538]

You just can't believe how quiet the Atlantic is! Such a complete lack of low pressure activity heading for the UK it's crazy. Could this finally be the building blocks of something special - everyone would be so gutted if everything flipped to wet and windy after the most promising start for ages!

[Matthew.]

14 minutes ago, mb018538 said:

You just can't believe how quiet the Atlantic is! Such a complete lack of low pressure activity heading for the UK it's crazy. Could this finally be the building blocks of something special - everyone would be so gutted if everything flipped to wet and windy after the most promising start for ages!

Really agree! The models showing cyclonic systems just walking across the Atlantic with no enthusiasm really. ENSO could be behind it so we shouldn't have a sudden surge as to last years Super El Niño

[carinthian]

48 hours ago the Numerical snowfall model we use with a spatial resolution of 3km x3km forecast 21 cm at this location. I can report a spot on prediction. Very impressed and so helpful with our forward planning. OK we are up to 1 mile in the atmosphere here , so marginal errors less likely compared with UK snow forecasting, but never the less the timing and predictive amounts is just amazing. We can now access snowfall predictions with-in the shorter time span of 6 hours almost to my back door location.

 C

[weirpig]

will at 198h  on Gfs the high still in control  and heights going into the pole.

[Cheshire Freeze]

18 minutes ago, weirpig said:

will at 198h  on Gfs the high still in control  and heights going into the pole.

Gets very interesting deep in FI

[weirpig]

youve got to love the gfs ,  Well  if this happens  ill be very happy  atlantic  what atlantic!  what a different position we are in to this time last year.

Edited October 20, 2016 by weirpig

[Tamara]

Equanimity, amidst plenty of uncertainties as stated in the previous update, is burgeoning further into cautious optimism in the seasonal count down as we turn the page into Autumn Part II

The road to Nina is stuttering.

Relative Angular Momentum tendency is now testing parity levels in a way not since the late Spring when an increasingly Nina-ish framework developed across the Pacific as the atmospheric circulation started responding to easterly wind momentum across the Pacific,scrubbing out the Nino westerlies and helping to upwell colder sub surface waters.

   

The Global Wind Oscillation,, which is a key measure of both tropical and extra tropical wind-flows, has responded with an orbit coming close to breaching the Nino threshold of Phases 5/6 and 7

The ocean has been saying tomato, but the atmosphere has been more inclined to want to say tomahto. Will they call the whole thing off?

The SOI index has dropped back sharply within ENSO neutral levels (+ or - 7) and is further prohibitive of any official weak Nina status being declared at any time before close of play 2016. Its probably curtains then into the New Year anyway. Another good reason for the UK winter fan to be cheerful, in my opinion, in terms of extended prognosis.

 

 The importance of this fine balance in ocean/atmosphere relationship is that the more weighting that can be given towards rising AAM through autumn, the more pre-empts the cyclical pole-ward wave breaking processes to be set in motion that take advantage of what is increasingly looking like an early season vortex  struggling to get out of its traps as we get closer and closer to the nitty gritty period closing down on winter. As fully and well documented on the stratosphere thread.

We should be aware that whilst the active Pacific and Atlantic tropical storm season is currently assisting pole-ward wave train eddies that help create meridionality in the pattern, it is the initial rossby waves courtesy of westerly wind momentum through rising AAM that helps plump up the mid-latitude ridges in the first place which can transfer poleward when the arctic troposphere/stratosphere boundary is compliantly sanguine to do so.   Recent/current modelling has well illustrated this with the very non zonal profiles of the pattern and the heights eagerly developing to the NE.

So I maintain we will do better this season if the trend stays our friend and the atmosphere/ocean signal does call off any attempts towards a Nina signal. We might not have all the cards this year in terms of solar/QBO  such as we did in 2009. But we could still do with an atmosphere loading towards rising AAM as a destabilising factor on the vortex. Autumn 2009 was also an ENSO neutral season, with the atmosphere tanking towards higher AAM as the crucial winter period was about to arrive.

There is evidence courtesy of MJO related tropical convection, that suggests ammunition might be available to sustain vortex destabilisation during November - just as the traditional tropical storm season starts to dwindle and the positive "destructive" meridional aspect on the jet stream starts being lost through that mechanism. Also, as discussed in the stratosphere thread, the low pressure anomaly developing in the Pacific, as a vortex destabilising factor, in the two week model forecasts is also what we want to see in terms of counter evidence that La Nina will establish.

If we want sustained chances of cold through winter beyond early season cold salvo attempts then "steady as she goes" is the hoped for mantra over the coming weeks, as wave lengths eventually tighten the coupling of the Northern Hemisphere annular mode heading into winter - and when the relationship between the trends of the AO and NAO (whether +ve or -ve) becomes more and more tightly forged

 

Edited October 20, 2016 by Tamara

[Seasonality]

Thank you Tamara for your beautifully written post. I hope I can approach your level of knowledge one day and it is a real pleasure to have your well thought out responses available to us. My own humble contribution is this little chart from the 6z. FI starting to look chilly, which pleases me no end. despite the caution needed at that range.

 

Edited October 20, 2016 by Seasonality
Typo

[fergieweather]

9 minutes ago, Seasonality said:

Thank you Tamara for your beautifully written post. I hope I can approach your level of knowledge one day and it is a real pleasure to have your well thought out responses available to us. My own humble contribution is this little chart from the 6z. FI starting to look chilly, which pleases me no end. despite the caution needed at that range.

 

Caution indeed, but not altogether surprising given signals (albeit presently not majority) in some extended M-R output from other centres. Glosea remains firm on early Nov blocking... BUT as I mentioned previously, we can't (yet) be clever re respective positions of high/low centres and resultant outcome re temperature regime here.

[feb1991blizzard]

Either way, looking at the GEFS extended ens, whether blocked or not, they nearly all look fairly chilly, so definitely no chance of the searing heat endured during recent Novembers.

[fergieweather]

Just now, feb1991blizzard said:

Either way, looking at the GEFS extended ens, whether blocked or not, they nearly all look fairly chilly, so definitely no chance of the searing heat endured during recent Novembers.

Yes, 00z EC ENS (15d meteograms) agree on a return to avg/slightly above avg TMax as next week progresses, followed by a bias slipping back to below avg into first few days of Nov.

[carinthian]

Afternoon all, just an update from this mornings report on how our Numerical Snow forecasting Model is performing. The shorter range spatial resolution for 6 hours as from 0900 today indicated a further 18 cm. As of this instant the total depth now is 35cm. That equates to 14 cm fall with another 1 hour to go. Its not going to be far off the mark.. This is turning out to be a major snow event for Mid October. Picture taken from balcony.

 C

[joggs]

1 hour ago, CreweCold said:

Gets very interesting deep in FI

That would cool things down lol.

[bluearmy]

The London 00z eps meteogram for week 2 shows a quite chilly regime becoming favoured once the declining number of less cold runs are discounted 

 

[Mucka]

Steady as she goes indeed, but not in a Titanicesque way one hopes.

GFS ensembles clearly showing high pressure influence over the UK slipping away in the latter stages of October.

That in itself could be a precursor to a more mobile and unsettled spell if high pressure were to slip away S/SE with the jet over the top as with some members (Generally depicting cool zonal/ low pressure crossing NW - E/SE temps around or a little below normal) or as has been signaled for some time a trough setting up close to E or SE of the UK with accompanying Atlantic ridge which could draw in much colder Arctic air (though as others point out, not necessarily, depending on placement, orientation and persistence of any ridge - non of which can be predicted even if we get the initial synoptic in place)

The 850 temps are also predicted to slowly fall away but not dramatically so and no prospect of any wintry weather away from high ground in the North as yet though the mean for early Nov could change substantially yet, especially once the large divergence between members is ironed out.

 

ECM going for some late October warmth before temps begin to fall away back toward normal which suggests the Op may be a little progressive this morning when compared to its ensemble suit.

 

We are probably getting close to resolving jet-stream ambiguity in the mid term which is an important phase of interaction between N Atlantic trough and declining Scandinavian high and once this has been nailed down a much clearer picture should begin to emerge as to whether Atlantic ridging will form and what shape that may take. That will make for some excellent early season model watching over the next couple of days for all weather geeks.

 

[bobbydog]

I know it's the far reaches of the GFS but it puts forward the strange suggestion that on bonfire night, some of us could be witness to an unusual phenomenon... Snow...

I'm not getting excited yet but I did allow myself to raise an eyebrow....

[Ali1977]

Much better charts so far today, albeit the good ones are beyond the period you'd class as probable!! I feel they could keep getting better, and I'm still going for an unusually cold bonfire night. 

[MP-R]

1 hour ago, bobbydog said:

I know it's the far reaches of the GFS but it puts forward the strange suggestion that on bonfire night, some of us could be witness to an unusual phenomenon... Snow...

I'm not getting excited yet but I did allow myself to raise an eyebrow....

That would be a bit of fun. There was some wet snow around on the morning of November 04th 2012 but unfortunately I was living abroad then.

[Mucka]

GFS 12z FI

A glancing blow...

Followed by trigger cocked for the coup de grace

Dare I say, "potential"?

Edited October 20, 2016 by Mucka

[The PIT]

3 minutes ago, Mucka said:

GFS 12z FI

A glancing blow...

Followed by trigger cocked for the coup de grace

Dare I say, "potential"?

At time frame just pure fantasy tomorrows run may show record temperatures instead.