summersnow

Good graph! We're straying way off topic here, so I've copied and pasted onto the General Weather Discussion Forum under the topic, "Melting Ice Key to cold winters", where I've already made some comment on this. This shows clearly the plateau in global temps I was referring to in my earlier post!

Good graph! We're straying way off topic here, so I've copied and pasted onto the Weather Discussion & Chat Forum under the topic, "Melting Arctic Key to cold winters", where I've already made some comment on this.

It's interesting to see ECM now picking up the PM trend post 168hrs that GFS suggested fairly consistently for several days towards the back end of last week for the same time frame ie last week GFS had this trend consistently post 240 hrs.

Here's another one! Just for reference, so far this winter the mid troposphere has been very slightly colder than the 2008 bar on the graph below! See the previous link to confirm what I mean... remember, we're on a par with Jan-March 2008!

Try this! These are temps recorded at 14000 ft, so not suseptible to having the data "smoothed" which is what has to happen with land based temps due to contamination by changes in land use/ urban heat island effects etc. If you can't open the link, get back to me and I'll direct you to the web site! http://discover.itsc...h?amsutemps+002 And for added interest......some pretty pictures!

Almost certainly will change! Although possibly not the way we think! Huge amount of variables currently for models to deal with. Although I do suspect another 10 days or so phase of dominance from the Azores, due to the reasons I have explained above, there are still alot of cards on the table!

Just eyeballing the North Atlantic SST anomolies again and it's clear that at least 80% of the North Atlantic has stayed warmer or much warmer than average all winter. In particular, there has been an exceptionally warm anomoly continually pumping east/north eastwards from around the Eastern Seaboard of the US. This has probably served to reinforce the western side of the Azores ridge, which has been by far the most domiinant feature this winter. In terms of the model output, I suspect solutions have on occasion responded to height rises to the north and flirted with colder scenarios, but the constant warm signal from the west Atlantic has always caused model output to default back to showing continued dominance of the Azores HP. This may well be some of the data the Met O have also had at their disposal in seemingly being able stay one step ahead of the model output available to the general public, most of the time. Why there should have been such a warm anomoly being sourced from the west Atlantic is interesting - probably something to do with being in a weak La Nina phase, which has also delivered a very mild winter to US lower 48. This warm air has simply continued its jouney eastward/NE, reinforcing the jet in the process. The jet has been so strong in fact,that it has very much inhibited the build up of sea in the Barents Sea, where again there has been a winter long very warm anomoly. Most other areas of the Arctic have had close to average sea ice with the Bering Sea notable in being above average. Global temps have actually been relatively low this winter, so no obvious link to Anthropogenic Global Warming to explain our mild winter and the warm anomalies to which I have referred. IMO, in general, the model output has been good, if looking for basic patterns and trends, with 5 or fewer runs virtually never likely to constitute a trend. The odd few runs flirting with pattern change should normally be viewed with suspicion unless fully supported by the the vast majority of the models within the suite.

GFS trending back towards a win yet again for the Azores HP as it effects UK weather. That has been quite a formidible feature this winter - quite resolute with its dominance, even into the Spring Equinox. Might well change again, but the signs are that the Azores HP is not for relaxing its grip just yet!

GFS 18z shows right good messy old dog fight between the air masses, with the Azores HP unwilling to go without a mother of all scraps, while cold HP builds to our NE. Agressive low pressure development the result & sandwiched in between, winds itself into a proper late winter storm. All looks very plausible for early/mid March, while GFS 12z was a colder outlier, both ECM 12z and GFS 18z look the more likely but different scenarios. Expect alot more change in the next few runs - nothing nailed at all! Azores HP might well yet have one final victory this winter but then again..... it's all ripe for a pattern change!

This is a really interesting situation developing! It's really telling the way GFS has moved more towards the recent ECM output but 10 days ago, GFS was actually hinting at something of this nature and this theme has recurred consistently in GFS output, albeit apparently erratic at times. The aspect of all this I find really interesting is the battle of the air masses - cold block to our NE vs the ever present Azores HP. While it's beginning to look increasingly like the cold air is likely to get the upper hand at least for a while, the Azores HP refuses to be pushed too far away or eroded too much. In all models, it remains a force to be reckoned with and can not be discounted - especially given its track record this winter! While there does appear to be a strong building of pressure in the Arctic, will it materialise or will it yet again be swamped by the power of the Azores HP? Just a few hours ago, GFS was suggesting the latter, so I do believe it to be very much in the balance. Spring equinox is a prime time of year for pattern change though!

Steady as she goes folks! This is a classic battle scenario with the low being sandwiched between the cold HP over N Scandi and the warm & so far very dominant Azores HP. As I've stated on several occasions, I do honestly think that this is the time of year for pattern change and this all looks quite plausible for early March - the classic winter sting in the tail as ocean currents start to shift around. But just keep in mind how powerful the Azores HP has been all winter and how easily it could just take control again here. It is about time for a bit of erosion of the dominant winter system but that's no guarantee that it will actually happen. It will all be a bit knife edge for at least the next 48 hrs.

Subtle but massive difference in GFS 12z compared to 06z by T+180hrs. Instead of the Scandi ridge being swamped by the Azores HP, the Scandi HP establishes itself further north and a classic stand off emerging between northern Scandi block and the Azores HP. Exciting stuff with GFS moving towards the ECM solution and a classic battle being depicted. This is what model watching is all about!

Agreed! ECM only really deals with the reliable time frame or at least doesn't go as far into FI as GFS. I'm sure the Met O have access to more data, but it must always be a forecasting nightmare at this time of year to try 1 month ahead predictions. I reckon they're on a pretty safe bet suggesting drier south/more unsettled north in the longer term though as this is pretty much the default pattern. I still think there is a reasonable chance of something a bit different happening 10 days hence, as GFS has for a while suggested.

I think the arctic blast later in FI might end up being very different to the way GFS is currently modelling it. What GFS shows is the agressive meeting of warm air from the Azores and cold air from the Pole, causing a strong north Atlantic Low to form. This could form virtually anywhwere between Iceland and the Azores, with very different outcomes. All very volatile... watch thi space!

Agreed - although a reasonably consistent theme from GFS on a PM flow after about 10 days. Also a sign of the season, sea ice melting, sun dipping its head into the Northern Hem, warming continent etc - all likely to throw the models into conflicting solutions. Oh, and I also forgot to mention gradually coming out of La Nina phase, heading towards neutral will also be a factor for the models to deal with!

GFS 06z continues deep in FI to suggest a a more PM flow, with eventual ridging into Greenland ....and finally an erosion of the Azores HP and fragmenting of the PV. A long way off but it has been quite consistent with a similar theme to this for a while now and the set up looks quite plausible for mid March - as is virtually any set up!

This is all a bit odd really. So, now what we're being told is that Global Warming means colder winters!! Just a few years ago, I remember the rhetoric being very different! And what is causing the Arctic to shrink in summer anyway? OK, if it's global warming, why is the same not true of Antarctica, where sea ice has been on an increasing trend for decades? Don't believe the media hype about massive ice shelves breaking away from Antartica being to do with global warming, because it has always happened. Look instead at the NSIDC website and you will see very clearly that this summer in Antarctica, sea ice is currently running above the mean for 1979-2000, while the Arctic shows the opposite. This has been the case now for a long time. There are a great many reasons as to why the Arctic might be melting more quickly in the summer months and global warming is just one possible explanation of many. To suggest however, that global warming is now causing colder winters in the Northern Hemisphere seems to me to be desperation on the part of scientists to explain at all costs why every single climatic change that we see must be attributed to global warming - what nonsense! Just think about it for a minutel. The big problem we are told is that less ice means less albedo so less ice to relflect light & heat from the sun. But how strong is the arctic sun even in summer? Yes, there's also a little less sea ice in winter but of course, there's no sun at those latitudes in winter, so the albedo thing is irrelelevant. What we do have however, is much larger parts of Asia and North America covered in snow until late spring, which way more than compensates for the loss of albedo from the Arctic ocean. Snow cover relflects radiation just as well as arctic ice after all. For me, a much more rational explanation is that we are seeing a natural cycle, probably driven ultimately by the sun and more directly by the oceans. More snow cover over continental masses will eventually cool the northern hemisphere enough for the arctic to recover its sea ice at which point the cycle will probably start again. We are more likely now to see a period of relative cooling, roughly equivalent to the late 20th Century warming, which has effectively plateaued for the last decade. Now beginning the slide off the other side of that plateau, what can we expect in the next 20 years? Time will tell!

For most of the country, the cold pool did actually prove vulnerable and so the models were technically correct. Much talk went on as to how the undercut might be achieved, but it never happened - again, as depicted in advance by the models! The cold that was experienced by parts of the country was only really the cold spilling over from the continent - as was modelled. The reason the cold wasn't more extensive and didn't become more sustained is because there was no undercut, no troughing and the Azores HP won the battle - as predicted by the models. In this coming scenario, it is very reminiscent, as you say, with GFS showing a brief colder incursion followed yet again by the Azores HP regaining control. ECM continues however, to show a more sustained period of cold. There is now a fair bit of divergence between these two models and it will be really interesting to see which wins this time around. I would have said this time one month ago an easy win for the Azores HP and therefore the current GFS 00z, but given the time of year, I do think a pattern change is much likely in the next couple of weeks or so. Obviously any cold that does arrive will be hugely moderated by the time of year but as I've said in previous posts, both the north an upland areas might be in line for some significant snowfall. On the other hand, we are just as likely to end up with balmy continental air from a more southerly/s'easterly quarter.

GFS 06z appearing to fall in line to a degree with ECM 00z. Interesting! It looks like the chances of something a bit colder on the horizon are increasing with the possibility of snow. My own interpretation of this for early March is that there may well be significant snow for upland and northern areas - although any snow at lower levels in the north will tend to not last - unless in sheltered locations. 60/40 in favour of such a scenario IMO. Still a long way to go however, and with Azores HP still close by, it could easily take charge again in future runs - as it has done pretty much all winter. As I've stated before though, this is one of the more likely times of year for regime change, so more likely in early/mid March than before.

ECM indeed looking to introduce something a bit different - almost bang on time for the beginning of spring equinox. GFS however, still keen to maintain a powerful and dominant Azores HP, which is never too far away. GFS continues in FI, to show he Azores HP sliding further west and orientating itself so that the jet alignment brings about a more polar maritime flow. GFS has been quite consistent with this theme for several runs now, so I'm beginning to suspect something similar will verify. ECM looks to be over doing things a little but it wouldn't surprise me to see a similar set up to this verify later in the month.

This time of year is actually for me the most interesting as regards model watching. Sometimes we see the most massive flips from a full on balmy spring scenario to sustained north or north westerly airstrems in the course of 24 hrs. I suspect this spring will produce some fireworks in that sense - although I still believe more balmy conditions will predominate.

GFS though quite keen now to put a slightly different orientation on the Azores HP, again introducing o much cooler west.north west airstream in FI. This is actually where I do think the models start playing around with a huge array of solutions - just as we approach the spring equinox, virtually anything can happen!

Into FI and there seems to be a bit of a wobble going on, from the consistently mild theme of the past several days. With some suggestion of a more northwesterly airstream, ECM in particular is going for height rises to our north. Probably just a wobble but it wouldn't surprise me to see this change in regime in early/mid March. I've explained my reaoning for this on a few occasions now but I'll need to see several runs confirming this trend before I start coming to any firm conclusions.

Agreed! I don't see this pattern changing much over the next couple of weeks or so. After mid March however, anything could happen as I explained above. Watch this space!

Well folks! I reckon in broad trend terms (which is what model watching is all about) the models have actually performed very well this winter and primarily in their ability to show the dominance of the Azores HP. In late January, I stated that I reckoned the models were making it more than clear that the Azores HP would remain the dominant theme and I suggested then that we might be in for an early spring. That is exactly what has happened despite an enormous amount of conjecture suggesting much colder scenarios. As regards, the current model outlook, it still looks like the Azores HP is going nowhere in a hurry but I would expect some sort of change by mid March as this is when the sun starts to exert a very different effect on the north Atlantic while at the same time sea ice starts to melt meaning that one of the main drivers behind the NAD is often disrupted. Of course quite what this effect will be is still pretty much pot luck, anything from warm dry continental airstream through to chunks of seriously cold arctic air. Any cold from an easterly direction will certainly subside as the continent begins to warm, so it will need to come from either the north or northwest. I think the much more likely scenario however, is HP setting up over N. Europe/ S Scandi and giving us mainly dry and pleasant conditions through March - the exception being possibly the far northwest of Scotland. By the way, if anyone considers our mild winter is anything to do with Global Warming, UAH Global average temps have recently dropped to the lowest ever on the satellite record!