Singularity

Thanks for the response. You prompted me to take a look at where 1.2 is exactly... turns out I forgot that it's actually displaced a little south of the equator That explains 1.2 having greater anomalies - currently +2.8*C compared with just under +2.4*C for 3.4. Having located the latest advisory (http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.pdf) I can see that the situation has changed quite a bit since Dr M. Ventrice's webinar [corrected - cheers Nouska], with 1.2 overtaking 3.4 during the past month. I imagine that's due to some large sub-surface anomalies extending up to the surface. This is why I often regret posts I make later than around 11 pm... I tend not to research them properly

Apologies for self-quoting but my questions seem to have been overlooked If a new thread starts it can be moved over there if you like, mods

http://www.weatherscientific.co.uk/2015/10/10/winter-2015-16-analogue-years-assessment/ Some compilation-based analysis here, a handy compilation of analogue years too. Unsure about some of the methodology but it seems to make sense generally. The use of 'solar activity falling after a maximum' as a criterion is intriguing, while the points regarding the possible impacts of the low Arctic sea ice minimum are cause for some thought... what do the peeps on here make of all this? For my part, I'm surprised not to see a mention of the possible impacts of having the strongest positive anomalies focused more toward the central pacific, which can still be seen in the global maps such as this one: Those near-neutral 'blobs' in the far-eastern Pacific seem pretty noteworthy, as if there's some kind of wave event - in fact I recall I watched a webinar by M. Ventrice a number of weeks back which spoke of a possible oceanic Rossby Wave. Here's a link: https://wsi.wistia.com/medias/j27zqgbtom The webinar goes on to detail the fact that with the peak anomalies further west, the downstream impacts change substantially, with a move toward positive height anomalies to the northwest of the UK. However, this effect appears to be much reduced with strong events - though I'm not sure we have any past examples of a strong central-Pacific type El Nino event to work with? This winter is starting to seem particularly unclear

Interesting that this October seems to correspond better to wENSO in general rather than just those that have a westerly QBO as well. Or so it seems having just read this for example: http://www.weatherscientific.co.uk/2015/10/10/winter-2015-16-analogue-years-assessment/ It also looks like Arctic sea ice (and perhaps falling solar activity?) could change the game a bit in November... but not necessarily. I'm wondering what you make of the potential sea ice/solar flux influence, but of course that's best answered in the winter discussion thread! . . . . . . . Some striking model output on offer so far today, which is a nice progression from the fairly uninspiring charts of the past couple of days. This is largely down to the high looking to have more of a chance of retrogression west of the UK for a time... but what are the odds that the changes to a more zonal regime not only manifest but do so at just the right time to topple the high before anything much comes out of it The GFS 06z det. still manages to finish on a fascinating note though. Imagine of the model was being under-progressive...! ECM'z 00z det. may be a reflection of some over-amplification but you never know I suppose. That +240 sure is a teasing chart.

It's nice to see the return of model corrections in favour of disrupting troughs and blocking highs persisting... for a number of years now we've spent a lot of the time seeing corrections go in the other direction. As I just posted in the winter discussion thread, this seems to reflect the state of the background forcing to some extent i.e. when the broad setup is favourable for blocking, the models underestimate the magnitude to which blocking actually occurs, whereas when forcing is unfavourable, the opposite occurs. I suppose I should ask - is it just me who sees this behaviour or is this a genuine model trait? Anyway, ECM's det. runs have first delayed and now toned down the push of westerlies from the Atlantic, enough so that we're no longer looking at the 'backside' of a trough combining with a mid-Atlantic ridge in 10 days time. GFS's det. runs continue in steadier form, as they hold on to the theme of slowly retrogressing the mean position of the high across the UK. It looks likely that if ECM was to continue making corrections along the lines seen over the past few days, it too would end up showing us a slowly retrogressing high, as each trough disruption/undercutting low allows the ridge to take a step to the west/northwest. This time last year, we had the pre-upgrade GFS det. runs to look at, and it was entirely reasonable to expect that for much of the time, whatever was shown beyond +192 hours was too progressive one way or another, with ridges toppling fast when in reality they would hold on for a bit longer. Now, we have the upgraded GFS det. (and any day now GEFS), and having followed this during the latter stages of last winter, I noticed it seemed to spend a roughly equal amount of time being too 'flat zonal' or too amplified with its solutions in the longer range. I actually reckon that some ways this could make it more tricky to anticipate the overall trend beyond a week's range

One thing I've noticed over the years is that when background drivers are favourable for blocking scenarios, the models tend to under-amplify the pattern beyond 6 or 7 days range, whereas then the drivers are unfavourable, they over-amplify. Back in 2009/10 it was almost guaranteed that blocking highs and an absence of the usual westerly flow would persist for longer than originally modeled. We seem to be seeing that sort of thing in the model output at the moment, though not as dramatic as it could be back then - a consequence of GFS having been upgraded I suspect. If anything it's ECM doing more of the corrections at the moment, with a strong burst of westerlies first put back by several days and now toned down to the point where it's unable to displace blocking highs from our vicinity.

CFSv2 seems to be taking the 'super El Nino' response over Europe as far as it possibly can... with the huge positive height anomaly preventing what would otherwise be quite a tasty February pattern in the multi-run means. The March pattern is starting to look pretty chilly though. If there truly is momentum toward more in the way of high-latitude blocking in February (all ready starting to show up in the multi-run means, in fact even January hints at it now) then I'd expect to see the +ve heights anomaly over Europe suppressed further south, toward the Mediterranean. It is interesting that although 2009/10 doesn't qualify as a strong or even east-Pacific (i.e. classic) El Nino, it is the only standing example with an El Nino of some kind occurring alongside cold SSTs in the N. Atlantic and a sea ice extent minimum close to 4.5 million square kilometers. The plummeting solar activity may also be another step in the right direction, though it can hardly be compared with where we were in 2009, which was in the latter stages of an unusually long, strong solar minimum.

Here's a question for the big-brains on here; Ex-hurricane Oho is currently on its way to Alaska as what will soon be a powerful ex-tropical system. Next week, another system has the potential to track right up to the high-latitudes as well (again, ex-tropical by that time). Such behaviour was seen last year but before then only once since 1949 (according to Jeff Masters via http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=3150). So my question is, what sort of impacts could this have in the troposphere and, more importantly wrt to this thread, could there be effects on the stratosphere as well? Would I be right in thinking that strat. impacts depend largely on whether the relatively warm air associated with the system encounters high land or some other forcing to lift it upward? Many thanks in advance for your response, I look forward to reading what you have to say

Next year looks ripe for a highly active Atlantic hurricane season, what with that SST anomaly pattern and neutral to La Nina conditions developing. As for the cold pool, CFS was killing that off before the winter when I checked it out about a month ago... how things have changed!

Cheers BFTV and Nouska, this is a real puzzler but thankfully probably not a huge player in our winter patterns based on the fact that when I create composites of +ve and -ve AMO years since 1948 they turn out to be very similar, with anomalies generally pretty weak anyway.

Yawn. Settled for the foreseeable and still a risk of a nagging easterly here in the south next week, although the GFS det. runs have backed off from that now. Interesting signals emerging for mid-October as the polar vortex attempts to establish in the vicinity of Siberia with a cross-polar high attempting to extend through Greenland to connect with a mid-Atlantic ridge, but also with a trough over Canada threatening to break it all down before it really gets started. ECM's +240 det. chart as an example: Oddly reminiscent of last winter's struggles isn't it? Yet we have many drivers in opposite states to last year so we should expect to see different setups evolving in a month or two... for better or worse. That's all I'll dare say about the winter in this thread. Looking at the example chart above a second time, I'm struck by the lack of 'flat' patterns anywhere in the N. Hemisphere, as in regions across which the jet and hence the 546 dam line aren't wiggling about like a distressed python.

A staggeringly informative post from Tamara... I was in the background last winter and followed the strat. developments every step of the way. I even began to grasp what AAM is and how mountain torque events drive large changes (and frictional torque events smaller ones). Reading about the positive QBO, Snowy L's post on the previous page of this thread highlighted the possibility that the westerly QBO could actually correlate with a slightly weaker vortex when occuring within an El Nino configuration. So I wonder how that might interact with solar activity? I do see the low Arctic sea ice as a significant factor this winter, as the high-latitude temps and moisture levels (hence latent heat amounts) are so very much higher than during the strong El Nino events of past. Curiously, I had a glance at years with similar sea ice minimums to this year and they tend to feature a prominent high latitude blocking signal in January, following not much of a signal in December and with February a sort of vague high/mid-lat blocking merger. Here's the January pattern. Not a lot of years behind it of course but interesting nonetheless.

Knocker and Recretos have more or less convinced me to do with a negative AMO when thinking about winter composites... many thanks for your informative posts. I'm officially a big fan of your work The jet stream behaviour this month is starting to catch my eye, with GFS in particular tending to keep it fairly weak and meandering across much of the N. Atlantic (and into Europe) for the foreseeable future. It seems to me that most of the stronger segments have tended to be very close to the SE side of Greenland... where the 'warm' Atlantic contrasts with the very cold ice sheet, and GFS suggests this continuing. ECM also has similar ideas from the looks of its 500 mb height progression. Prior to the autumn getting underway, I was thinking that the region of unusually low SSTs would encourage the jet stream to develop strong segments down near the Azores (the southern reaches of the neg. anomalies), based on what happened in past years with such cold pools, but this year is showing little sign of that so far. The atmospheric temp. gradients driven by seasonal cooling in the Arctic seems to be by far the dominant player. I'm not exactly surprised though, as in my investigation of winters from 1990 to 2014, only 3/4 of the years showed much of a relationship between the SST anomalies and the jet stream, leaving plenty of room for alternative behaviour driven by other forcing.

Some brisk easterlies are now looking very likely for the south this weekend and for at least part of next week. Temps look a bit mediocre but nothing too chilly for the most part, just a nagging wind. Further north the outlook features lighter winds, with a better feel by day but a higher risk of frost overnight. All in all, very benign. The only real suggestion of much change again comes from ECM in the 8-10 day range, as the jet stream kicks up a gear with a brief surge of westerlies flattening the high pressure. GFS maintains an unusually weak, meandering jet stream for the most part, with high pressure incredibly dominant - hardly any rain for most parts throughout the 16 days covered by the det. run! Not a lot of rain spikes in the ensembles, even: ...and even ECM's westerly push looks less convincing this morning, with signs that the jet could quickly return to a meandering state.

Hmmn that is one to watch in terms of being a heavy rain threat. A fairly slow moving remnant low could be Joaquin's final act. Meanwhile GFS's 12z det. keeps the remnants to the west than northwest for the most part, but trough disruption sees a secondary circulation splitting and heading SE to bother SW England for a time. The ECM det. runs are being persistent with the theme of low heights really getting going in the vicinity of Greenland in the 7 to 10 day period, but the GFS det. runs have tended to maintain a more inconsistent area of trough activity. Not that the ECM version looks all that convincing in terms of relentless westerlies powering across the Atlantic.

Ah! Yes, thank you very much Nouska Cheers for the paper too, even if the technicality makes my eyes water a bit

The pattern over the last week or so has had high pressure ideally positioned to feed a lot of relatively warm air across the cold pool region, diminishing the seasonal release of heat from the ocean a bit. I doubt it explains the whole of the change we've seen though. The coming four days flip that around with some cold air over the region so that may have some effect as the ocean-atmosphere exchange steps up a notch. Beyond that, signals are a bit mixed really. As air has a hard time heating the ocean but the ocean can easily release heat to the air (as the ocean has a much higher specific heat capacity), I reckon the presence of anomalously cold air tends to have a bigger impact than the presence of anomalously warm air at this time of year. Shortwave radiation is the only thing that can really put heat into the oceans, which is why I suspect recent patterns haven't had much of an impact other than slowing the seasonal cooling. Please don't hesitate to correct me if I'm wrong

On one of the American weather forums someone posted a screen shot of a CFS SST prediction for next July, and it had positive SST anomalies in the tropics and extratropics, with the subtropics nearer to average (corrected as I originally thought cooler than average). That's basically the reverse of this year's dominant pattern. If anyone knows where such long-range charts can be obtained I'd be grateful for a link, regardless of how little stock I put behind that model beyond a month or two's range If that did take place, the idea of a negative AMO would surely have to be binned for a little while longer, with this year's behaviour a fluctuation in an overall positive AMO. I may as well check out the importance of the AMO to our winter patterns; Having used the westerly QBO to narrow down the years, the positive AMO cases then give the composite on the left while the negative AMO cases give the one on the right: The signal seems to be for the pattern to feature more of a negative NAO when the AMO is positive and a positive NAO when the AMO is negative. However, the anomalies are very weak, too much so to read much into. An anomalous year or two could easily be distorting the picture from what is essentially a neutral outcome. In light of which, it seems the AMO is of little concern, and quite probably the QBO forcing tends to overwhelm it.

Well this thread has managed to leave me confused about the AMO state... I seem to recall that Met Office were saying last month that it had most likely changed to negative? Aha - found an article with the answer within (http://www.theactuary.com/news/2015/09/2015-likely-to-be-warmest-year-on-record-says-met-office/) "AMO – a fluctuation in the sea surface temperatures in the North Atlantic – would likely be entering a “negative†or cooling phase, which could temporarily cool the climate. - See more at: http://www.theactuary.com/news/2015/09/2015-likely-to-be-warmest-year-on-record-says-met-office/#sthash.EacrltnU.dpuf " On here, it seems to be more a matter of opinion with respect to how its analysed.

ECM does try to ramp up a vortex of sorts to our north between +192 and +240 of the det. run (surprising given how Joaquin heads SW of the UK on this run) but the dominant signal from the det. runs and ensembles is for a rather benign setup to return, this time it could be less 'stunning' than what we had last week, but I suppose some dry air could get pulled in to create lots of crystal clear skies again. Low pressure slipping in place over NW Europe could bother the south with some rain though. Elsewhere, the next couple of days look to be a blip in a predominantly dry theme, though if any Atlantic frontal systems due make it to the UK against that blocking high then some prolonged rainfall would be a likely result so that's something to keep an eye on. The blocking high seems favoured to stay in control, though. That chilly air to our east may well lead to a nagging chill in the wind what with the low pressure being signaled for NW Europe. I can't say I'm looking forward to such prospects, but if the associated blocking high to the north of the low can drive warm air advection up into the Arctic and mess with that vortex then it may well be worth enduring for the longer term gains. This perspective won't work for everyone of course (e.g. I gather that Knocker is not a fan of winter cold?).

https://www.youtube.com/watch?v=TBrt99MnHmE#t=43 This is the first 'in the storm' video I've come across. Looks... like some kind of watery hell on earth. I'm a big fan of extreme weather but I think I'd have to be in a bomb shelter, on an island with nothing to lose (i.e. uninhabited!) to enjoy that level of event.

Okay, perhaps not 180 mph generally, but perhaps briefly in a convective downburst? Actually what am I on about, the gusts are to 190 mph anyway, and in any case they're not what makes a category 5 Anyway, just read this comment on wunderground: " Joaquin has closed off a ring of -70C convection. Given that the pressure was quickly falling when recon departed, the storm is probably peaking near or at Category 5 intensity right now. " With this supporting image: As you can probably tell, I really want this to be recognised as a Category 5 at this point in time (not when nearing Bermuda, by that time weaker is better!), purely for the historical significance; it would be the furthest north Cat. 5 ever recorded, and possibly the only one ever to have originated from a cold-core upper level low as opposed to a warm-core disturbance.

Sheesh. This thing just won't quit! Check out these two lines from one of the latest vortex messages: D. Estimated (by SFMR or visually) Maximum Surface Wind: 138kts (~ 158.8mph) H. Minimum Sea Level Pressure: 934mb (27.58 inHg) - Extrapolated That's Category 5 strength. I did suspect this sort of thing might happen when Joaquin suddenly spun up a full wraparound of very intense convection at around 10:00 this morning (BST). The NHC has chosen 155 mph for the official status though. I believe 156 mph is the Category 5 limit so, with all due respect, this seems a bit unfair of the NHC to Joaquin. I get why though - they only ever work in 5 mph increments so it would have to hit 160 mph to qualify in that manner. Here's the update information: SUMMARY OF 1200 PM EDT...1600 UTC...INFORMATION ----------------------------------------------- LOCATION...26.0N 71.6W ABOUT 595 MI...960 KM SW OF BERMUDA ABOUT 230 MI...365 KM NE OF SAN SALVADOR MAXIMUM SUSTAINED WINDS...155 MPH...250 KM/H PRESENT MOVEMENT...NE OR 50 DEGREES AT 16 MPH...26 KM/H MINIMUM CENTRAL PRESSURE...933 MB...27.55 INCHES I believe that when the eye wobbled violently, that was a burst of particularly strong winds, when surface speeds may have been as high as 180 mph based on similar behaviour observed in Hurricane Wilma of 2005. The true peak of this cyclone may never truly be recorded.

To be honest, when it comes to blocking highs over Scandinavia or Russia, I find longer-range model output to be pretty much useless. Just my opinion of course! Certainly some fascinating prospects on offer from ECM yet again this evening, in fact the 12z det. seems to be the most extreme run so far in terms of how that cold progresses across Scandinavia by day 10. It's achieved via development of a large low south of the blocking ridge. The GFS det. runs have been reluctant to develop this feature, and although the 18z does, it has a low over Siberia creating a break in the blocking high through which the former low escapes. With out support to the south, the blocking high sinks slowly south and things end up looking a lot like the 12z det. which was very benign for much of the time from +192 to +384. If it turns out that quiet I'll be dozing off each evening

'1000 year flood' sounds like a flood that will last a thousand years, imagine if the media got hold of that idea Of course the real definition - an event on a scale that 'on average' you wouldn't expect to see more than once every 1000 years - is still very alarming. Thoughts are with those who face destructive weather conditions of some kind or other.