Model Output Discussion - Spring Has Sprung

[Met4Cast]

The ECM isn't showing a QTR, best estimates place the SSW on the 18th possibly 19th February, that would be an instantaneous trop response which unfortunately, isn't possible. 

In any case - I remain unconvinced of anything prolonged or sustained, the SSW is certainly a wildcard but I think it'll be rather difficult to see anything proper in terms of cold before the SSW takes place, and even after then I'd be cautious on any possible impacts re: UK specific cold hopes. 

Notice how through December these anomalies were propagating poleward, this led to the early January cold spell. Compared to now these anomalies are moving subtly equatorward, i.e no HLB. The sudden change on todays UKMO & ECM towards wedges is an interesting one, but given the ridiculous spread within all ensemble suites at the moment it's not worth putting too much emphasis or hope into that just yet.

It may not seem like it but I'm really trying to find a reason to be optimistic about cold, but I can't just see it currently. Post SSW might be a different story though.

[bluearmy]

 Daniel* yep - it was over retrogression in 2018 

until we get a handle on what reversal we are likely to see then can’t really speculate 

[Daniel*]

3 minutes ago, Met4Cast said:

The ECM isn't showing a QTR, best estimates place the SSW on the 18th possibly 19th February, that would be an instantaneous trop response which unfortunately, isn't possible. 

It’s possible the trop pattern can be already primed and be a catalyst to major SSW and very rapid downwell they are ultimately related. So I would say the ECM 12z is QTR in my opinion. 

[Mike Poole]

 Daniel* Yes, the way the strat and trop have been in step this year, it has been quite difficult to tease out what is cause and what is effect.  Should the split vortex SSW happen, I would expect a very quick trop response, even to the extent of both impacts appearing to happen pretty much simultaneously.  

[Met4Cast]

8 minutes ago, Daniel* said:

It’s possible the trop pattern can be already primed and be a catalyst to major SSW and very rapid downwell they are ultimately related. So I would say the ECM 12z is QTR in my opinion. 

You can't see a trop response to an SSW on the same day the SSW is happening, that is impossible. The trop could already be in a position where blocking is happening during an SSW but that would be unrelated to the downwelling impacts of the SSW.

Complicated, but I don't think this can be classed as a QTR to be honest. Surely a QTR is a direct response to downwelling easterlies? Pre-primed trop patterns that happened to produce blocking as an SSW occurs, whilst you could argue is loosely related to the SSW happening in the first place, isn't a response to the SSW in of itself.

Either way. Given the huge amount of spread I think it's largely irrelevant what any det run is showing at day 10 currently.

[stodge]

11 minutes ago, Met4Cast said:

The ECM isn't showing a QTR, best estimates place the SSW on the 18th possibly 19th February, that would be an instantaneous trop response which unfortunately, isn't possible. 

Indeed, I see very little this month but I think March is looking more "interesting" and while some on here don't consider it a "winter" month, 2013 and 2018 would disagree.

The chips will fall where they may as a wise man once said and we may get an early spring out of the SSW but the likelihood of northern blocking in March and April is there and could work even at this late stage to the advantage of those looking for a final hurrah from a winter which has disappointed many.

Again, I'm watching the synoptic pattern consistently trying to build heights to the north east and disrupting LP in the vicinity of the British Isles.

[Daniel*]

6 minutes ago, Mike Poole said:

Yes, the way the strat and trop have been in step this year, it has been quite difficult to tease out what is cause and what is effect.  Should the split vortex SSW happen, I would expect a very quick trop response, even to the extent of both impacts appearing to happen pretty much simultaneously.  

As said the AO is already on side, I think it’s a good indicator to a quick response. Much less possible interference and the need to break down stubborn +AO.

 

[Met4Cast]

Whilst pointless analysing beyond day 5, the GFS is not interested in the idea of a wedge of heights to the north and if anything the 18z has flattened the pattern more than the already flat 12z.

[joggs]

 Met4Cast Yes,a truly awful chart. Only saving grace is the op has been on the fairly mild side of the pack frequently.

Them blasted Iberian heights

Edited February 8 by joggs

[Met4Cast]

 Daniel*

It seems a "QTR" isn't something that appears in literature so it's difficult to actually define. 

In my mind a QTR simply refers to rapid impacts from downwelling -ve SSW anomalies, something which still takes time & therefore cannot be instantaneous. 

[Met4Cast]

Trying to diagnose a potential way forward is proving impossible. The aforementioned equatorward fluxing of +AAM anomalies suggests a strengthening Iberian/S European high however the MJO likely transitioning into a weak amplitude phase 8 combined with an increasingly unstable polar profile (SSW) suggests a likelihood of high latitude blocking. 

Two rather opposing signals fighting for dominance, no wonder modelling is struggling to the degree that it is. From a forecasting point of view, the mid-extended range at the moment is nigh on impossible. Getting cold into the UK with an Iberian high in the game though really will be a struggle, the ECM shows this reasonably well with both HLB and an Iberian heigh. 

@Kasim Awan might have to change his name again.

Edited February 8 by Met4Cast

[Mike Poole]

I think we may see a lot of this sort of evolution over the next few suites, GFS T318:

What I will be looking for is for the transfer of heights north to occur to our west in the Atlantic, rather than through Spain up through the UK.  There is enough time for this shift to happen as the shenanigans associated with the SSW (if it occurs, still not sure) kicks in, I think. 

[johnholmes]

 Met4Cast What on earth is a QTR please?

[WYorksWeather]

Quick look at where things are this evening. ECM 12z ensembles just look very benign. Probably modestly above average for the most part until at least 16th, then a lot of scatter.

The mean at day 10 still seems to have far too much influence from Iberian heights for anything interesting to happen.

By day 15, the mean just drops a trough through the UK. Probably wet but not overly cold.

 

[Met4Cast]

 johnholmes Quick Trop Response. 

[*Stormforce~beka*]

 Met4Cast We are still non the wiser ...

On 24/01/2024 at 12:17, ANYWEATHER said:

ou can actually Quote what you want by using the Quote function by keeping your finger for a few moments on the sentence etc . I’ve had a go and it works really well, as Paul said gets rid of a lot of cl

 

[Met4Cast]

7 minutes ago, *Stormforce~beka* said:

We are still non the wiser ...

A Quick Trop Response (QTR) simply means a rapid response to a SSW. I.e impacts from the SSW reach the trop faster than what would ordinarily be expected. 

But.. I’d argue a QTR cannot be instantaneous, i.e the same day an SSW happens. Imo you’re looking at about a week, rather than hours. As Simon Lee said though, the idea of a QTR doesn’t appear in scientific literature on SSW’s so the actual definition is open to interpretation. 

Might be helpful if we agree on a definition for future use of the term though.. 

Edited February 8 by Met4Cast

[Singularity]

A QTR is quite probably a misinterpretation of cases where a major SSW occurs at the same time that a -NAM (stratospheric -AO) exists in the lower to mid stratosphere. The -NAM higher up can then, in a sense, connect within less than a day & reinforce the -NAM, hence -AO beneath.

So it’s really a ‘quick tropospheric reinforcement’, dependant on the troposphere being forced the right way (-AO) by e.g. an MJO event in the run up to the major SSW. 

[*Stormforce~beka*]

 Met4Cast Interesting! Thanks for that!

[Paul White.]

 johnholmes Hi John I think QTR = Quick Trop Response, in other words the splitting Strat  will work its way down to the Trop quickly  

[Don]

1 hour ago, Met4Cast said:

Two rather opposing signals fighting for dominance, no wonder modelling is struggling to the degree that it is. From a forecasting point of view, the mid-extended range at the moment is nigh on impossible. Getting cold into the UK with an Iberian high in the game though really will be a struggle, the ECM shows this reasonably well with both HLB and an Iberian heigh. 

That appears to have been the main issue in the last few years where the Iberian High has led to the UK to struggling to get cold via HLB.  It seems this didn't occur very often in years past, where you had HLB and Iberian blocking at the same time or frequently as now? 

[WYorksWeather]

 Met4Cast I'm still quite pessimistic about any looking further ahead into March. The reason is that the lack of any cold to work with means that we really have to imagine we're 2-3 weeks ahead in the year in terms of temperature. The temperature over the Northern Hemisphere is already more characteristic of a typical late February or early March. By the time we get a major SSW, and even with a QTR of say a week, and then assuming it works out in our favour as far as blocking and cold goes (already essentially granting that we get a near perfect dice roll), at the absolute earliest you're looking at the last few days of February. 

From there, you then take that the NH cold pool at that stage is likely, if current trends hold, to be more characteristic of mid to late March. When was the last time we got a notable, long-lasting cold spell in mid to late March?

Not ruling out an additional dose of something wintry - maybe a similar event to today with some wet snow for northern areas and accumulations over hills. But I really think we'd need something to kick in well before the end of February if we're going to get anything significant out of it.

Frankly, if nothing comes up on the ensembles that looks significant and notable in the next 10 days (by which point the extended range will run into early March), I'm done.

[MP-R]

 Don It’s often the responsible setup for some of our worst summer months, sending lows straight through the UK. Instead we’ve had a few winter versions which are even more depressing.

[Dancerwithwings]

 Met4Cast

I love to abruptly call some on hear that *QTR*….Quick Trolling Responses

[WYorksWeather]

Done waiting for the GFS 18z, still incomplete but nothing below average up to T+312 / day 13. Not overly mild at the surface particularly between 12th-15th and from 18th onwards but still slightly above average. Nothing cold in the outlook going by the mean.