Wow...it's been quite awhile since I've been able to post here. I appreciate you coming by and I apologize for the lack of posts lately. I'm excited to sink our collective teeth into the pattern in this post, and...
I'll also be updating some of the topic related posts in time, and will backdate them appropriately, so you may notice some topic posts (not forecast discussions) appearing before this one over the next couple of days as I work to catch the site up with the interesting stories I've seen in the past several days but haven't been able to post. I remain optimistic that things will quiet enough in the future that I'll be able to post more regularly here, though I do hope you've been enjoying some of the extras on the NECN Weather Blog. There'll be more like that to come on my NECN broadcasts on-air - lots of 6 to 10 day stuff, Weather Features in the forecast nationally, more weather video from across the country and the globe - an overall process of stepping up the presentation as our new meteorologist, Danielle Niles, is on board and doing a great job, helping to buy me some time to start thinking creatively once again, and certainly adding her own creativity and intelligence to the process, as well!
Weatherwise, the longwave pattern is one that has been painstaking! If storms don't go too far south, swept out to sea by confluent flow, they go too far west, pulled that way by the recurring upper low over the Great Lakes and Southern Canada. As I look at the pattern in the days to come, it's certainly as if we have too MANY shortwaves that are strong. One wouldn't think that's a problem at first, but when you realize that the trough axis can't shift east because yet another shortwave is digging into the longwave trough, it comes to light that we're having problems properly amplifying each shortwave. Having said that, we're having no problem amplifying the longwave trough as a whole, with cold air diving all the way into Florida and the Panhandle on Monday seeing a colder diurnal maximum than Boston - a sad statement for the month of December. The thing is, when you look at individual features, the map is downright menacing - I mentioned in the general weather discussion on the NECN weather blog today (in simpler terms for those who aren't quite as weather savvy as the regular reader here) that the 500 mb chart really is one that makes you do a double take. The vorticity maximum digging over the Pacific Northwest, the upper low digging across South-Central Canada, and the presence of southern moisture in a well defined southern stream all are alarm signals, but if you can't phase them, you can't have much fun, meteorologically speaking. This is the deal on Thursday - a good front, and one that, on the casual glance at the 500 mb chart, has me thinking secondary coastal low development along the front in the Southeastern US, then tracking up the coast and getting us on the cold side of the front as it stalls off the coastline. Most times, such a setup would verify. But in the year of the upper low over Eastern Canada (so far) keep dreaming for such a scenario - reality says the streams can't merge and we get a convective line briefly late Thursday as mostly rain, then more westerly flow with cold air advection.
The cold has had no problem holding its own as it moves into New England, though, nor do I expect it to run into many problems this weekend. A strong downsloping component will be present for most of us on a westerly wind, but of course, that means upsloping in the favored west-facing mountainslopes where upslope snow squalls are expected from late Thursday night onward, with some Lake Ontario enhancement in the Greens. Of course, there's another strong shortwave digging into New England this weekend, and while the ECMWF continues to go off on this thing, making a doozie of a storm for New England...AND while I do have a lot of respect for the ECMWF...it is completely by itself on this one. There's not a single GGEM Ensemble member that agrees, and all other ensemble and operational solutions suggest the trough is simply too deep, too far east for amplification of this system and that it will be ushered - you guessed it - out to sea for a strengthening east of New England.
Of course, with vorticity maximums flying overhead, upslope snows should be able to continue, and we know snow guns will blast day and night across most of Northern and Central New England with temperatures cold enough around the clock. So, skiers can delight in that but bundle up with an active wind, especially Friday and Saturday.
Amidst the bleak forecast for snow lovers, however, there are a few beacons of hope (or despair for those of you who read this in trepidation of the first snow - not many of you reading this, based on your comments over the years). What we need to do is get the strong northern stream energy to already be phasing - or at least interacting, more accurately - with southern stream moisture and energy early in the game. This early interaction has been happening already, which is why these storms wind up over the Central US and Great Lakes, but the problem has been a broad southeast flow scouring out the cold for Southern and Central New England, leaving leftover cold for Northern New England to play with, then even diminishing it there. So, we need ample antecedent cold as another ingredient. I have to admit that it's never a great sign for snow lovers when you're just hoping old cold is strong enough to survive, but I also have to admit that it's a good setup for some big New England snowstorms because you can get a good warm/moist conveyor belt, a coastal front, and all the fixins for some good eatin'! We have an early phaser next week when a chunk of the upper low sitting off Baja breaks east and interacts with strong northern stream energy. This northern stream shortwave isn't some imaginary vort max that has to develop - rather, you can see it for yourself, today - check out the water vapor image I've attached from the FY2C satellite.
The vort max is up over Siberia/East-Central Russia, and is pinwheeling around an upper low. This vort will eject east, dump into the displaced Aleutian low sitting over the North-Central Pacific, then eject east again, ripping into the Pacific Northwest this weekend and beginning its interaction by late Sunday. This should really juice up as it taps the Gulf of Mexico by Monday, then lift into the Ohio Valley and Northeast Tuesday into Wednesday and be packed with tons of Pacific and Gulf Moisture. There's a problem here, though, at least preliminarily, and it should sound familiar: the upper flow goes southwesterly, the high moves, and warm air comes flooding north. The confluent flow is pretty far east on Tuesday morning already, so the high is migrant and the surface flow is also going southerly. This isn't the final writing on the tombstone for this one, though, because it does hold a ton of potential...we just have to see a change in the guidance to hold the cold longer in the northeast, which I think will happen...but even that would end up being enough to get a shot of warm advection snow in Central/Southern areas Monday night or Tuesday, but no extended thumping of snow as the atmosphere would then warm up with the possible exception of Northern New England.
That's not the end, however, as another monster shortwave will eject out of Siberia only a few days after today's comes steaming out. This next one actually is progged to be so intense that it turns the semi-permanent North Pacific upper low into a highly amplified, very sharp trough by late this weekend, as seen in the H5 ensemble plot here.
That energy unloads into the Central US - YES, I really did say CENTRAL US trough - by sometime either side of December 15, and this is the next big window of opportunity to watch. Yet another early phaser, yet another loaded system with Pacific and Gulf Moisture, and with antecedent cold left behind by the last big storm.
So...it becomes clear that we're entering a volatile pattern with plenty to watch, and plenty of opportunity for exciting storms, though ptype will be a challenge with these storms right down to the wire, I would imagine. Skiers, however, should be quite excited, because even the warmer of the upcoming solutions would still deliver dumpings of snow to the northern mountains, plus cold enough weather in between storms that even if a change to rain does occur, the guns go blasting for days to follow.
Enjoy!
Matt
Matt, did miss your info greatly over the past few weeks. I always tell my clients that we live in the "safest" area of the country because yu need so many ingrediants as you explain for anything major to happen. As a Arborist the weather has a tramendous effect on my business. Here in central Connecticut our plows are idle and our salters are ready and frankly looking to new. Would love to see some of these systems really turn into something so us plowers can eat. No one even comes close in regards to the knowledge you bring to us followers welcome back! Terry
Posted by: Terry Ryan | Wednesday, December 03, 2008 at 08:23 AM