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The hunt for cold - Model discussion (late November)


Message added by Paul

If you're hunting for cold potential in the model output, this thread is for you. But if you'd like to look more widely at the models, please head over to the general model discussion thread.

This is a model related thread, so a general, frequent theme of the model output is a given, but it will not be strictly enforced:

  • Some topic drift, humorous responses etc are fine
  • Posts likely to lead the thread off on an entirely off topic tangent are not ok. For example (but not solely limited to): Posts entirely or mainly about Met Office, BBC or media forecasts with little or no model context, and posts solely asking for a weather forecast in a specific location.
  • Posts which start with something like 'I know this is off topic but ...' are not ok.
  • Posts which break the forum guidelines are not ok (eg trolling, troll-hunting, weather guilt tripping, overly defensive/aggressive, abusive, disrespectful to others)

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1 hour ago, Leon1 said:

This happened with this cold snap though didn't it and at the last minute it suddenly appeared back on the charts. 

This isn't aimed at you @blizzard81 BTW but everyone on here needs to realise that it's all still to play for. Let's pray for the 6z runs. ? 

I certainly haven't given up lol. Just commenting on the latest runs. Onwards and upwards! 

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6 minutes ago, Mike Poole said:

All but one GEFS member showing a technical SSW by the end of the run, so now up to 20/21:

image.thumb.jpg.860952293d95a5871e07a8a84163ab59.jpg

Pretty sure there's only one there that doesn't dip below the line!

 

So from my untrained understanding, zonal winds will reverse between Dec 24 & Dec 29 (as per GEFS variations) and then maybe up to 14 days for a trop response? So by mid-next-week, we should see something showing in the GEFS that we could attribute to the SSW? We are heading into prime Wintertime, so for once an SSW can deliver some wintriness, rather than be wasted on a cool Spring! 

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1 hour ago, Bristle boy said:

Yep! Been banging on about this for last couple of weeks. May be a spoiler for blighty, even if any SSW occurs.

As many on here say when a HP establishes itself it can be a git to shift. Those heights have been there or thereabouts for a couple of weeks now and are likely to stay in pos for next 2 weeks.

Yes, we need these heights to get sucked up to mid Atlantic heights rather than meandering over southern Europe. 

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2 minutes ago, IDO said:

So from my untrained understanding, zonal winds will reverse between Dec 24 & Dec 29 (as per GEFS variations) and then maybe up to 14 days for a trop response? So by mid-next-week, we should see something showing in the GEFS that we could attribute to the SSW? We are heading into prime Wintertime, so for once an SSW can deliver some wintriness, rather than be wasted on a cool Spring! 

GFS is now showing effects currently. SSW displaces PV which allows Pacific WAA up into pole for negative AO2FCF7238-5AFA-421F-AC52-3AC580B9500B.thumb.png.a054f43118d4dc5f12f87c9f0834396d.png

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5 minutes ago, KyleHenry said:

GFS is now showing effects currently. SSW displaces PV which allows Pacific WAA up into pole for negative AO2FCF7238-5AFA-421F-AC52-3AC580B9500B.thumb.png.a054f43118d4dc5f12f87c9f0834396d.png

I thought the current cycle was WAFz going from the trop to strat leading to the PV push in the strat. That downwelling from strat to trop (PCH's) will come within a quick to 14-day time window after the reversal? Is that wrong?

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54 minutes ago, claret047 said:

Good Morning everyone.

As a relative novice I was surprised at the reaction to the 00Z run with all the negativity it had caused.

I believe it was John Holmes that has stated in the past that it is all about trends. We will know soon enough if our excitement was premature, but I suggest that we wait at least another two (possibly three) runs before we throw in the towel. 

In any event there will be plenty of excitement later today for our friends in the north of the UK and hope you enjoy it.

Kind Regards

Dave

If I had the time I would be doing a check 00 and 12Z outputs for at least 168h ahead from today, say, in fact I will find the time to do just the 12 z at 168h from 12Z today then 24 off each day to see how one run is dealing what 'may' happen 1 week or so away.

I have no idea how this will turn out so it will be interesting to follow it, well it will for me.

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6 minutes ago, johnholmes said:

I am rather surprised IDO you are comparing run to run at quite extended ranges! You would be on more sure ground if you were quoting the same run time with 24 hours difference.

Yes, certainly would not get into any scientific paper as it is rather a poor example. However I was trying to make a small point, that flip-flops are more likely when the theme is inconsistent, rather than seemingly a trend as the GFS (may) currently show! I don't even think the experts can be decisive on the late December pattern so most of us are just drawing on experience and amateur knowledge to get a grasp of things. 

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22 minutes ago, IDO said:

So from my untrained understanding, zonal winds will reverse between Dec 24 & Dec 29 (as per GEFS variations) and then maybe up to 14 days for a trop response? So by mid-next-week, we should see something showing in the GEFS that we could attribute to the SSW? We are heading into prime Wintertime, so for once an SSW can deliver some wintriness, rather than be wasted on a cool Spring! 

That is apart from March 2013 and last third of Feb and March this year which were freezing certainly not cool.

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Quick one to all those far FAR more knowledgeable than I...

are there any other winters past that have had a similar timed SSW falling over our little isle with a split rather than a displacement?

and if yes then what was that January/February/March period like for us?

in other news... based in Strensall near York at the moment waiting for the snow but this wind is more of an issue than I thought it might be!!! Guess I got too caught up in chasing the snow to factor in anything else!!! Oops!!!??‍♂️

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11 minutes ago, IDO said:

I thought the current cycle was WAFz going from the trop to strat leading to the PV push in the strat. That downwelling from strat to trop (PCH's) will come within a quick to 14-day time window after the reversal? Is that wrong?

No not at all. Trop lead with EAMT event that sends energy up(20-22nd Dec) Downwelling following reversal  from approx 23-24th Dec to oust the upper PV. Then Trop lead again 24th-26th into pole.

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1 hour ago, bluearmy said:

I expect if we had access to the modelling that Exeter do then we too would be excited ........ the stuff we can see isn’t showing us the route to deep cold just yet ..... it feasible that the met office modelling is also headed in the same direction as the final blocks are put into their expected places for the scenario that the cold glosea and ec 46 clusters show ...... but we can’t see that route so we remain in a state of ‘meh’.  Will be notable if/when the 30 dayer drops its suggestion that the onset could be brought forward to the turn of the year 

Precisely my point Blue. The free to the public stuff we get to make our prognostications on is probably no more than 30 per cent of what the met have available to them.

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3 minutes ago, ryanoroo said:

Quick one to all those far FAR more knowledgeable than I...

are there any other winters past that have had a similar timed SSW falling over our little isle with a split rather than a displacement?

and if yes then what was that January/February/March period like for us?

in other news... based in Strensall near York at the moment waiting for the snow but this wind is more of an issue than I thought it might be!!! Guess I got too caught up in chasing the snow to factor in anything else!!! Oops!!!??‍♂️

2013 was the last time we had a split around this time of year, happened on the 6th of Jan. The 2nd half of January saw a weak block to our NorthEast but it gave tonnes of snow to some places. The main cold spell happened in March though.

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3 minutes ago, Mike Poole said:

The bigger picture is that we've taken giant steps

 

Hope you're right mate, you were spot on about the recent hot summer!..hoping for better operational output as the new year comes into range!?❄️:santa-emoji:

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5 minutes ago, Mike Poole said:

Slightly surprised at some of the negative comments this morning, although there's a reason I don't tend to comment on the 0z runs - well, apart from being asleep!  

The bigger picture is that we've taken giant steps over the last 24 hours alone.  The SSW is nailed on.  It was one ensemble member on yesterday's 6z suite that got me excited, the first to show a split in the strat vortex following the SSW - now that split is all over the model output like a pi**ing puppy!  

FV3 6z at T360, just as on the 0z run:

image.thumb.jpg.62907860db831a5136ae5f7fefbeef39.jpg

My negative thoughts are solely based on the fact I was getting excited about a white Christmas and that seems to have imploded.

Still hopeful for late December and January though.

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5 minutes ago, lorenzo said:

 

Anyone looking for some HLB ? these MJO plots should satisfy...

3.thumb.jpg.58a9e4761480929334e2d1355bee3ea5.jpg4.thumb.jpg.eb3db303d72582811203e18259489462.jpg5.thumb.jpg.523158c9237d2a9e1ff8b122ad617617.jpg

 

Going to need to be a huge change around from the current ens guidance at  the end of week 2 for week 3 to be right re anomolys in ne Canada 

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2 hours ago, markw2680 said:

How is it hard to see them flip back? The models are chopping and changing every run and as there’s still 10 days to go I’d say they will flip loads between now and then. There is no consistency at all.

too much doom in here today tbh

i totally agree so much data for the models to process final out come wont be clear until we see where the strat events take us and other background signals like the amm and mjo.

i think its blooming exciting personally and not a common in december either.

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