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Model Output Discussions 06z 04/11/16

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Been spending some time reviewing latest models. Signals give me a feel of deja vu. Likely to start the month slightly cooler than average, with a more atlantic driven influence. Then chance, and only a chance, of becoming v mild for a few days. Thereafter; current indications of colder, more settled conditions with fog and frost!

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53 minutes ago, Ali1977 said:

Yes seen this, I mentioned yesterday it backtracked slightly although others didn't agree.  Today's write up for 1st week into Dec definitely looks like the Atlantic wins out - but for how long is anyone's guess.  Still NO sign of a proper block to any sector of the North, up until the end of Dec week one that is.

The disappointing aspect re their update is that end Nov/early Dec was (only 10 days or so ago) being touted as the period 'to watch for' height rises to our North.

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5 minutes ago, Bristle boy said:

The disappointing aspect re their update is that end Nov/early Dec was (only 10 days or so ago) being touted as the period 'to watch for' height rises to our North.

Yes, it doesn't give us much confidence for mid December despite these favourable NH patterns and whose to say any  energy exiting the States etc, won't throw a further spanner in the works. Still the next few days should be relatively cool/cold with some overnight frosts for those who can avoid the plates of cloud.

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There is every chance that when the Atlantic does come in it could be from a NW-SE Axis.    There are indications that the high pressure will drift to the east this could allow the pattern below to unfold

Its states likely to be milder overall than the preceding week does,nt necessarily mean Mild Weather, and with the metoffice using the word likely makes me believe they are very unsure themselves.

 

gensnh-19-1-192.png

gensnh-19-1-240.png

gensnh-19-1-264.png

gensnh-19-1-288.png

gensnh-19-1-312.png

gensnh-19-1-336.png

gensnh-19-1-360.png

gensnh-19-1-384.png

Edited by booferking

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love it when the models make me look silly well the gfs anyway not a bad run perhaps sliders might be the theme into december but i remain skeptical for now.

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mpkio2 - I like your post a lot! The one thing that stands out for me by T240 - a wedge of heights just to the west of Greenland. It's coming up over and over again. It doesn't guarantee a northerly, but it may well be a precursor to one.

I would agree though, looking at the ensemble clusters for T240, not to get too carried away with the idea that a northerly is imminent, because the evolution even before that point is quite scattered (as you mention).

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2 minutes ago, booferking said:

There is every chance that when the Atlantic does come in it could be from a NW-SE Axis.

Its states likely to be milder overall than the preceding week does,nt necessarily mean Mild Weather, and with the metoffice using the word likely makes me believe they are very unsure themselves.

 

gensnh-19-1-192.png

gensnh-19-1-240.png

gensnh-19-1-264.png

gensnh-19-1-288.png

gensnh-19-1-312.png

gensnh-19-1-336.png

gensnh-19-1-360.png

gensnh-19-1-384.png

I would have to agree. Very uncertain times.

Just reading what the latest Meto 16 - 30 day forecast says, taken from Meto 16-30day forum for period after 6th Dec:

"However, some milder, windy and unsettled weather is likely at times, and as this bumps into the cold air, this would bring the risk of some snow. On balance, despite the potential for incursions of milder weather into the south at times, temperatures will probably average out on the cold side, with further frosts expected."

So perhaps, there is a HP to North with lows coming off the Atlantic bumping into cold air:

Like what yesterdays GFS 12z FL showed at end of run:

gfsnh-0-360_oqy7.png

gfsnh-0-384_tmf6.png

~mpkio2~

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4 hours ago, warrenb said:

I agree, look at the charts for mid December 1962 for example. Flat as a pancake pattern. Even the best winters have a few goes before getting there.

 

Rrea00119621216.gif

I wouldn't say completely flat as in zonal mush from the SW (not that you did either!).  Looking at the air source for the majority of the UK, that wouldn't have been all that mild. Pretty raw in a WNW strong gusty breeze if not gale for many, with frequent showers I'd say, looking at that...

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11 minutes ago, Man With Beard said:

mpkio2 - I like your post a lot! The one thing that stands out for me by T240 - a wedge of heights just to the west of Greenland. It's coming up over and over again. It doesn't guarantee a northerly, but it may well be a precursor to one.

I would agree though, looking at the ensemble clusters for T240, not to get too carried away with the idea that a northerly is imminent, because the evolution even before that point is quite scattered (as you mention).

Quite a spread there in the ensembles at t240 on the 06z GEFS, Man With Beard! But yes, some do show some some heights to the west of Greenland:

gensnh-6-1-240_jhs5.png

gensnh-10-1-240_mhn2.png

gensnh-19-1-240_pmm5.png

Some still don't so evolution to pattern is very specalative. Interesting, nontheless.

I'm surprised that no one has mentioned the GEFS 06z Controll run:
gensnh-0-1-144_pmd4.png

And goes on to a GH end Nov, going aginst OP run:
gensnh-0-1-192_jyr1.png

:):cold:

Again, all for fun and speculation; just interesting the signal is still there in the ensembles (Even if there is no UK cold) :pardon:

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2 minutes ago, Nick B said:

I wouldn't say completely flat as in zonal mush from the SW (not that you did either!).  Looking at the air source for the majority of the UK, that wouldn't have been all that mild. Pretty raw in a WNW strong gusty breeze if not gale for many, with frequent showers I'd say, looking at that...

Yep, not far off the sort of air source everybody is bemoaning as not cold enough showing in the models at the moment.

Edited by warrenb

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@fergieweather

@NathanC45706937 correct but with milder (& windy!) phases possible into early Dec. Generally below avg then signalled further through Dec.

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34 minutes ago, Catacol said:

Not really. What he actually says in his headlines at the start is:

What I was referring to was the medium term; I agree this Winter has the potential to be significant with respect to mid-latitude cold. However Dr Cohen had been very keen on a warming event late November and this has now been delayed a month or so. That was the "downbeat" comments I was referring to. I think many on here were expecting something significant before mid-late December (may still happen, but now unlikely). I would not dare to delve into Jan-March forecasts and I suspect nor would Dr Cohen.

So you believe we will have severe cold in the next few weeks?

Edited by IDO

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h850t850eu.png

T+96  and if the HP over the uk extending northwards was able to really dig in for a few weeks, that would potentially provide us with lots of fun!

Edited by Gavin Hannah

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1 hour ago, Catacol said:

Not really. What he actually says in his headlines at the start is:

 

"The stratospheric PV remains weak due to an early split of the PV and as of yet no meaningful recovery is predicted.  In fact the models are predicting further weakening of the PV through the end of the month.  The ongoing weak PV is likely to elevate the risk of wintry weather across the NH continents, especially Siberia but also including East Asia, Europe and the US during much of December."

 

And this para is about as excited a para as you will read anywhere about the current setup. Downbeat? You must be joking.

 

"It is my opinion that it has been a fall season of superlatives not the least of which is the anemic growth of sea ice in the Arctic during October and November.  Sea ice extent actually decreased this past week in the Arctic, which may be unprecedented (admittedly I am not a sea ice expert) but regardless Arctic sea ice remains at record low extent.  In contrast, Eurasian snow cover has remained consistently well above normal and has been at decadal highs since the middle of October.  To me these are strong signals that the Arctic is a much more dynamic region than in the past in large part due to rapid rise of temperatures and moisture.  It is in my opinion that the extensive Eurasian snow cover and limited Arctic sea ice contributed to an unprecedented early PV split and more weakening of the PV is predicted for this week with no foreseeable reversal.   Extended periods of time in the fall where the PV is continuously weak is rare and I believe complicates the forecast.  We have overlapping PV weakenings, downward propagation and upward energy transfer that constructively and destructively interfere with each other.  This has not only made it difficult to discern the signals that I like to monitor but has made it difficult for the operational weather models to accurately forecast the weather patterns and atmospheric circulation in the medium range.  I expect the forecast challenges to continue in the near term.  But regardless the extensive Eurasian snow cover, the reduced Arctic sea ice and the stronger than normal Siberian high all indicate at least one significant PV weakening event/SSW during the winter months followed by an extended period of severe winter weather across the NH continents including East Asia and/or Europe and/or the Eastern US."

 

 

Pretty obvious what the post you're responding to is up to, like they say in internet land 'don't feed the...' 12z GFS trickling out and the cold plunge into Europe now into the reliable, and it looks like the UK is coming into play more. *edit or maybe not, will it or won't it push west!

 

gfs-1-138.png

Edited by Seasonality

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Icelandic low leaving the are faster?

 

gfsnh-0-162_mnj2.png

 

Previous

gfsnh-0-168_cjr1.png

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It does look like we've got settled and reasonably cold for the next 5 days nailed on. The cold pool looks slightly further east on the 12z at t.144. Stronger HP signal extending over Nova Scotia also compared with the 06z run. It's all in the details.....

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9 minutes ago, Seasonality said:

Pretty obvious what the post you're responding to is up to, like they say in internet land 'don't feed the...' 12z GFS trickling out and the cold plunge into Europe now into the reliable, and it looks like the UK is coming into play more. *edit or maybe not, will it or won't it push west!

 

gfs-1-138.png

You do realise that for this cold pool to effect the UK there will have to be strong movement west between now and T94, and that ship has sailed a few days ago. There is no retrogression forecast and that UK high has been modelled to sink SE for many runs. We are within the reliable so this is very doubtful to change.

I think the story has moved on from that missed cold shot to what follows from the next Azores pulse of WAA in the Atlantic from around D6?

 

 

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Looking much better this run, more effective WAA into Greenland due to a better tilt in the low

 

gfsnh-0-198_gie3.png

 

Previous

gfsnh-0-204_opz6.png

 

Much more amplified this time

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More drama upstream! GFS doesn't phase the Greenland low with the one exiting Newfoundland, the UKMO does. And these differences are at T120hrs.

The differences at that stage mean completely different evolutions past that point. Putting that aside even the UKMO re-amplifies the flow upstream at T144hrs.

Edited by nick sussex

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3 minutes ago, nick sussex said:

More drama upstream! GFS doesn't phase the Greenland low with the one exiting Newfoundland, the UKMO does. And these differences are at T120hrs.

So we can safely set FI at t120 then. Big differences moving forward if UKMO solution verifies.

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As @nick sussex says, it's probably academic by this stage as FI is earlier, but interesting how on the GFS 12Z at t192 the low to the SW of Greenland comes up against the 'block' and just stalls for a few frames at least.

t192 gfsnh-0-192.png?12  t216 gfsnh-0-216.png?12

 

By t234 it's still sort of 'stuck' and the difference between it and the 6Z is stark

12Z gfsnh-0-234.png?12  6Z gfsnh-0-240.png?6

Volitility'R'us at the moment.

Edited by Ravelin

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