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Model output discussion 25th Jan - The final third of winter beckons..

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3 hours ago, Tim Bland said:

Hmm personally I'm not buying it. Will be very impressed with that forecast of a cold spell starting end of nxt week if it happens though...time will tell i suppose.

Our northern blocking is gone completely from the models this morning. IMO we will have to wait longer for the trop response to any SSW and MJO phase 8 - meaning blocking will not return for another couple of weeks, perhaps early march before we see the effects on our weather. 

Certainly it's a bold call but I can't help but appreciate the fact @Steve Murr is often prepared to stick his neck out. Looking at the ensembles this morning it'd be quite some turnaround, and whilst shenanigans are still expected up high it'd need to produce a very quick response for such a prediction to come right. Either way, I'd rather hope Steve's right than what appears to be an early start to Spring, even if the data before us currently suggests the latter. I guess that's what makes this forum so compelling, FI is never far away!

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Morning all :)

After yesterday's angst and anguish, more of a sense of resignation this morning I sense.

There's no point arguing the toss - the 00Z Output was poor or very poor for cold and for a continuation of the cold spell past next Monday or Tuesday.

As has been suggested, the secondary displacement of the PV from Canada/Greenland back to Scandinavia has taken energy into the northern arm of the jet and caused the HP to sink.

This would be fine if the flushing out of the vortex enabled a height rise in Greenland but after some encouraging signs yesterday, GFS in far FI is much less encouraging today and indeed rubs salt in the proverbial by sending the PV back to Greenland - this could be the response to another forecast Eurasian side warming.

gfsnh-10-384.png?6

The PV is weaker and less organised - no question - the 10HPA temperature down to -64 is a good sign - but time is against us and IF the next warming requires a further 10-14 day response as the PV shunts back to the Atlantic side, then we are looking at early March for the tropospheric response which might be another attempt at a Scandinavian HP.

The frustrating thing is we are very close to the Greenland HP solution:

gfsnh-0-192.png?6

At this stage you couldn't rule out enough correction to orientate the Greenland ridge further south, send the Atlantic LP a bit NW and try to dig the Scandinavian trough a bit south. Unfortunately, it doesn't happen this time on this output. It will be interesting to see if the Greenland HP has any support in the 06Z GEFS and whether it's an option we'll see on the 12Z.

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I would certainly expect some wintry surprises as the Easterly digs in accentuating the chill with temps only  two or three degrees c above freezing and freezing or sub-zero overnight so showers feeding in from the north sea will have an increasingly wintry element with a risk of slight falls, especially over hills. 

Edited by Frosty.

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2 hours ago, Bring Back1962-63 said:

.

ADDITIONAL COMMENT: 

I have just had a chance to look more closely at the 0z model output. This is so illogical, that I cannot accept it. I have banged on about the Euro cold block for over 6 weeks now. The models have been dreadful in factoring in the persistence of this block even when we had a powerful Jet Stream. By this weekend, the block will be further west, much more extensive and more intense than it has been at any time this winter. It will take a great deal to shift it. The Atlantic is extremely weak. The favourable background signals will be the powerful driving forces during the next few weeks. The latter part of the strat warming impacts, probably the PV migrating to Siberia (rather than a split vortex) and the MJO set to be in its most favourable phases and strongest amplitude since March 2013. At worst we will see a less cold (possibly slightly milder in the UK) interlude during the transition but not for "all" of Europe. Finally,, south-south-easterly winds will NOT be mild - read my post last night on this. The models almost always under estimate surface temperatures under slack or quite hpressure following a cold spell. Show me a powerful Jet Stream firing directly towards us and I'll back down on my strong opinion!

Agree with you 100%,the block looks to strong for it to just slip away, I know the cross model out puts are saying a different thing, but I've still got confidence in the HP to be a bit more unpredictable  

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The models appeared to be reading the script a couple days ago re the retrogression and dropping the Siberian fed vortex into scandi

But the gfs ops seem to have lost that for the time being (this often happens only for them to get it back after a few days) - the gefs and gem ens have also drifted away to a more euro high solution in the longer term and the ext eps whilst looking reasonable to our north can't shake off the euro high anomoly.

So either the nwp is going to shift back in response to upstream telecon changes or this weekend will indeed be winters last hurrah (though a cold march which teases is easily possible and given our luck, entirely likely!) 

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Just spent ten minutes deleting some really lovely snow laden charts taken from various models from November through to the end of January.  What a pity - so much promise but so little delivery.  Still, the way I see it is that we have had no farms cut off by rising floodwaters, no towns and city centres flooded for days by overtopping rivers, no bridges washed away, no coastal rail lines cut by storm surges and very few power outages.  From this perspective the winter has been memorable for me, at least.  And all is not yet lost by a long way.  The CFS for one is showing that the cold could continue right through to the end of February.  These images are only 14 days away....

image.thumb.png.6e0ccc0dbeaaf39fb7b6a1d3ed2315dc.png

image.thumb.png.212ca0b9e84efe9f8167a018e3f7432e.png

image.thumb.png.4dea9882f3389a583f033eaec8dc72cf.png

Now this is way out beyond FI even so little chance of accuracy but the CFS is a serious computer model so these predictions are at least possible, and may even be more likely than not.  All to play for then in the second half of February?  I'm not giving up yet.

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25 minutes ago, snowflakey said:

Agree with you 100%,the block looks to strong for it to just slip away, I know the cross model out puts are saying a different thing, but I've still got confidence in the HP to be a bit more unpredictable  

The problem is that we have a deep cold pool over Northern Canada which is stubbornly remaining there. This will continue throwing out cold air outbreaks into the NW Atlantic. Until you remove that cold pool it doesn't matter what those background signals are... the block will struggle to build over Greenland as a result.

Saying that though I believe there are two factors that I believe are comprimising this winter:

- The QBO pattern.

- North Atlantic cold blob.

High pressure seems to be sticking to Central Europe like a magnet this winter. We seem to be falling into the same trap as what we did at the start of the winter, we keep saying the background signals favour cold therefore it will be cold. This however is not the case, often it is just observing where the cold and warm areas are in the relevant parts of the world within a reliable timeframe. In the reliable timeframe unfortunately we have cold pools in the wrong place (when moving away from the UK!).

Sometimes the teleconnections can be strong enough to overwhelm the formation of the PV around the NW Atlantic but not at this point!

Edited by Quicksilver1989
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24 minutes ago, bluearmy said:

The models appeared to be reading the script a couple days ago re the retrogression and dropping the Siberian fed vortex into scandi

But the gfs ops seem to have lost that for the time being (this often happens only for them to get it back after a few days) - the gefs and gem ens have also drifted away to a more euro high solution in the longer term and the ext eps whilst looking reasonable to our north can't shake off the euro high anomoly.

So either the nwp is going to shift back in response to upstream telecon changes or this weekend will indeed be winters last hurrah (though a cold march which teases is easily possible and given our luck, entirely likely!) 

I suppose everyone's interpretation of whether March is a spring or a winter month will vary and the atmosphere doesn't care much!

IF we are looking at a second Eurasian warming in mid month or later, that will mean the PV moving back into Canada/Greenland for 10-14 days before we see a tropospheric response. and that means into March before we get another bite at some blocking. IF we get a clean lift of the PV into Siberia (the very thing which is causing the Scandinavian HP to sink) the opportunity for height rises over Greenland exists as I explained in my previous.

The problem is, if enough PV energy remains to prevent a Greenland height rise we will be stuck waiting for the next warming.

The tropospheric response to the second warming will be another attempt at HLB blocking in Scandinavia in mid March - it would be "better" if the Greenland option played out with the trough dipping into Scandinavia as yesterday's 06Z OP FI showed but that isn't being shown as strongly this morning for reasons I can't fathom at this time. It might be a consequence if the second warming displaces the PV further into Canada - the new warming has a more European than Siberian hint so the possibility for me is the displacement will be further west and we would be back in the game.

As ever, more runs are needed...

 

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Latest Euro 4   show showers developing widely across the UK .  Also usual caution advised however a rash of precipitation developing in the North Sea   a few could get quite lucky  

17021006_0806.gif

17021006_0806 (1).gif

Edited by weirpig
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Good agreement on the short-term ens out to the 16th with the mean, control and Op all close together

graphe3_1000_306_141___Londres.gif

Spot the rouge run :rofl:

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4 minutes ago, Summer Sun said:

Good agreement on the short-term ens out to the 16th with the mean, control and Op all close together

graphe3_1000_306_141___Londres.gif

Spot the rouge run :rofl:

Or trend setter 

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The ENS have a few tasty Arctic blasts in FI between them, 4 or 5 looking good but are the minority.

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In terms of the stratosphere, it is a shame that the GFS has abandoned the split vortex idea that it was advertising for around mid month. It vanished from the output 2 days ago and got replaced with a displaced vortex to Siberia. The 6z is the most uninspiring so far as it doesn’t even show the displacement.

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41 minutes ago, fulham snow said:

Super computers,what is the point

Indeed. Humans plugging in algorithms that reach the wrong answers even quicker than the humans can.

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21 minutes ago, weirpig said:

Latest Euro 4   show showers developing widely across the UK .  Also usual caution advised however a rash of precipitation developing in the North Sea   a few could get quite lucky  

17021006_0806.gif

17021006_0806 (1).gif

I've checked a few of the higher res precip models and I have a feeling this won't just be the North getting the flurries, some show the south has just as good a chance.  Could still be a few surprises of a cm or 2 in places anywhere in England I think.

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5 minutes ago, Ali1977 said:

I've checked a few of the higher res precip models and I have a feeling this won't just be the North getting the flurries, some show the south has just as good a chance.  Could still be a few surprises of a cm or 2 in places anywhere in England I think.

Yep i agree Ali  Northern and eastern England the best chance drifting into middle England  however showers will develop widely  i expect a few surprises.  Surely it cant be rain?

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Locking this now, new thread open shortly. 

New thread is up:

 

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