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Wednesday, November 25, 2009

El Nino battles a rapid expanse of snow/ice for control of our 09-10 winter

The amount of emails I have received would either indicate either an unusually high outbreak of the "winter itch" or simply a friendly nudge to commence the bloggings. Well, commencement time is here and ski season at MRG is likely only a few weeks away. The winter forecast has by no means been sorted out (Let's not kid ourselves here it never is !!) but expectations for this winter have been interesting to say the least. Off the heels of the coldest "North American" winter this decade there has been hype and then more hype for the upcoming winter. Much of it no doubt generated from those hungry for a bit of publicity and print. What seems lost in all this is the strengthening El Nino which in recent weeks has indicated it intends to be worthy variable this winter and one certainly that will earn plenty of mention in our annual pre-season post.

El Nino Comes Alive
To recap, the last two winters have been free of any El Nino. 2007-2008 featured a moderate La Nina, 2008-2009 was a weaker version of '07-'08. Both winters fit nicely in to the New England winter stereotype which included some big highlights, some forgettable lowlights and a few deep freezes. Sea surface temperature patterns in the tropical pacific have undergone a rapid transition over the last several months and by autumn, an El Nino event has been born. This ENSO event has more recently turned into a more significant event as sea surface temperatures in the critical regions of the tropcial pacific have warmed to 1.7 C above what is considered normal. Typically I deem a significant ENSO event to be anything 1.5 above (El Nino) or 1.5 below (La Nina). If your interested in learning more bout El Nino or La Nina then hit up Wikipedia for anwers. For the blog, and the winter forecast, we are more interested in actual impacts as opposed to definitions. Historically El Nino's of a moderate to strong variety produce a lot of mild weather centered mostly over the mid-continent and mostly over the higher latitudes. The central provinces of Canada for example such as Manitoba and Saskatchewan typically see the warmest temperatures relative (in North America) to normal in a moderate to strong El Nino. Across interior New England the impacts of mild weather are felt to a lesser extent but one would find it tough in the last half a century to find a moderate or strong El Nino that would produce a colder than average winter. It is therefore, statistically a bad bet to expect a winter like last in terms of cold. In terms of snow however it is a entirely different story. The jet stream in a typical El Nino behaves very distinctly and brings very moist systems across the southern tier of the country. Flooding across the south is very common and the storms eventually tend to interact with the highly baraclinic Atlantic Coast and evolve into big time precipitation producers across both coastal and interior areas of the northeast. The lack of cold can be a recurring problem for coastal areas as far as the receiving of natural new snow but is less so for interior areas and even less for interior areas with the advantage of favorable oragraphy. It is for this reason that El Nino can get me very excited. With even a limited supply of cold air, El Nino is capable fo producing some fantastic results for the interior northeast and snowy winters such as 06-07, 02-03, 92-93 and 69-70 are in play again. Preferrably I would like to see El Nino weaken a touch as the heart of winter approaches and the supply of cold air is always going to be a concern but so long as we have access to cold, the snow will not be far behind.

Moving on to another favorite variable the PDO, we have watched this make its long awaited decadal switch in the last few years. This will allow La Nina events to occur more frequently than El Nino events over the course of a few decades but this yeah appears to be one of the exceptions with the development of an El Nino and the slightly positive PDO. The biggest months of snow and cold in Vermont tend to occur when the PDO is more positive as opposed to negative although this didn't stop some of the good periods of snow and cold that we got the last two years when the PDO was negative. Generally though, to achieve a sustainable period of rain-free, lots of powder, lots of cold one would want a positive PDO and I am thus happy to see it slightly above zero.

Snow and Ice expansion
And we go to the expanse of ice and snow that earned itself a headline in the headline. I have been indeed very impressed this year with the increases in snow and ice this autumn. In October the total area of snow and ice across the Northern Hemisphere was over 20 millions of square km. This has only happened a handful of times since this data has been recorded in the early 70's. The Rutgers snow lab also tracks this on a weekly basis and the most recent week ranked 6th of 42 in total area of Northern Hemisphere snow/ice coverage. We saw some similar readings in another semi El Nino winter of 06-07 and similar results in the El Nino winter of 02-03. Both winters saw good snow although 06-07 was the one winter of the top 6 which saw above normal temperatures. The other 5 can be categorized as normal or below normal. The impacts of snow and ice on the outcome of winter has been debated amongst forecasters although I maintain that although its effects are very indirect they are still quite profound. Cold air pools more efficiently over snow and ice and thus cold air in a cold pattern can be amplified and a warm pattern mitigated. The winter of 07-08 featured a relatively normal expanse of snow and ice but by January, the extent of snow and ice had grown to a seasonal record and helped turn what looked to be a mild February into a relatively normal one in the eastern U.S. and a very cold one in the central United States. If the snow continues to expand as it has so far this winter it will be just the medicine we need to combat the mild forces of El Nino.

In my circles, there has been talk and references to the QBO or the Quasi-Biennial Oscillation. This in short measures the direction of the stratospheric wind in the tropical pacific. I tried to do some homework on this and found some good work on its relationship to tropical activity in the Pacific and Atlantic. I also found it to have some relationship to ENSO. I had a tough time being convinced of its effects on a mid latitude winter. I therefore am not using it but it has been referenced as a justification for a cold and snowy forecast in 2009-2010. Look it up on Wikipedia if you would like to learn more.

I have not yet been in advanced discussion with the folks at MRG about a joint blog-mountain sponsorship campaign. If however you have a local business (lodge, restaurant, retail) and would like a way to get the word out to the MRG demographic than send me an email. I would imagine money going to some MRG project and space to the right of the blog dedicated to your business. I have been slightly hesitant about doing this but I think it might have the effect of ensuring that I get off my lazy rear-end and post a few updates. More on this to follow if there continues to be interest.

Summary and a final and very fearless forecast for 2009-2010
The post must include a short summary and this must include an actual forecast so the details are as follows. El Nino tilts the range of possible temperature scenarios to the warm side but within this range I think temperatures will be on the cold side (did I say that right ??) thanks to the rapid expanse of snow cover. Temperatures will thus fall in the normal to perhaps slightly above normal range. Snowfall on the other hand will be outstanding and I am going to predict the snowiest winter since the blog began and will include one lone epic period similar to what happened in February of 2007 and Christmas/New Years 2002-2003. Snowfall in the end will exceed 300 inches. I have gotten a few emails about the weekend which looks stormy through early Saturday. The storm will develop in the Ohio Valley and intensify upon interaction with the Atlantic Coast. Rain will turn to a wet snow Friday evening and Friday night and accumulate significantly at the high elevations while somewhat more insignificantly in the valley's. It will surely not be enough to open MRG since mild weather is on its heels. I will post more on the next two weeks this upcoming weekend but I typically don't overextend my blogging until the mountain opens and this remains a few weeks away.


TQ said...

QBO-e favors a weak polar vortex...arctic outbreaks... negative phase of arctic oscillation...and stratospheric warming events.

Moderate +ENSO year ending @BTV
1966 - 111.6"
1969 - 96.3"
1987 - 67.6"
1995 - 60.5"
2003 - 83"

72.6" period-or-record average

All but 1995 had a quasi-biennial oscillation (QBO) in its east phase…just like this year!

Todd said...

nice to have you back. It means it's winter!