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Friday, March 30, 2012

Winter 2012 - The winter that wasn't

The record breaking weather that defined half of the month of March, making it the warmest in the last 120 years is over. The first two weeks of April will be more seasonable and with the AO having attained a negative footing, we may actually see an occasional taste of winter. At this point however, most of us have mentally tuned out of winter either refocusing on NCAA basketball or perhaps gardening since the warmth has certainly caused many of those to spring to life.

In the pre-season extravaganza of 2010-2011 I devoted a chunk of time discussing the split personality of La Nina winters in Vermont. We had highlighted several winters going back over the last 50 years which had illustrated how La Nina can be either feast or famine in northern Vermont. This point was obviously underscored during the past two winters. 2010-2011, although we did miss a few storms, was generally a strong winter featuring consistent cold weather and deep snow persisting well into April. 2011-2012 by way of comparison was a complete abomination. I thought we might avoid the embarrassing distinction of having to live through the warmest November to March period in northern Vermont (we were actually slightly colder than 2001-2002 through February), but then we got a March heatwave and what amounted to some of the most anomalous weather ever recorded in Vermont from a temperature standpoint. By the end of the month, the winter of 2011-2012 as defined by the period beginning in November and ending in March was rather easily the warmest ever recorded. From a snowfall standpoint the winter was close to being one of the worst ever. For many ski areas, the combination of lack of snow and outbreaks of above-freezing temperatures made it the worst ski season ever. Only a handful of winters can rival this past winter for lack of snow. Mad River Glen recorded about 150 inches of snow, 100 less than average. 1990-91, 88-89, and 79-80 were all similar. The lack of snow in 1979-80 brought the region some notoriety with the 1980 Olympics being held in Lake Placid. I have some pictures somewhere of crews frantically spreading artificial snow in preparation for the various Nordic skiing events that year. This year would have been similar but in many ways worse because of the added effect of the invariable relative warmth.

The explanation behind the massive failure of the 2011-2012 can be boiled down to a few key points. For a La Nina winter to achieve some success in Vermont, it needs the support of a negative AO for key stretches of the winter. We got such support for about two weeks in late January and early February. The average daily AO index from November to March was roughly a positive 0.9. I would have to do some further analysis on this data but a rough glance indicates that the standard deviation of these results going back 100 years is probably about a 0.5 or so making this years number very statistically significant. The 2010-2011 winter was approximately negative 0.4 while the incredibly "blocked" winter of 2009-2010 was well below a negative 1 (My other weathergeek friend is currently telling me the 09-10 winter featured the most negative AO ever recorded over this period). We might have been able to endure the lack of high latitude blocking in the jet stream but repeatedly this was coupled with a very tight and vigorous jet stream across the mid-latitude Pacific Ocean. Though the jet tightening can be partially attributed to the positive AO there are other contributing factors. The more obvious would be the presence of La Nina since the tight Pacific Jet is one of its defining characteristics. The other factor I have heard mentioned is the MJO or Madden-Julian Oscillation. This is the term used to describe the cycle of convection in lower latitude regions ranging from the Indian Ocean to the Atlantic. It is complicated but phases of the MJO are determined by areas of enhanced and suppressed convection in these regions. In this particular winter we went through an extended period of time where it was difficult to determine a phase. Specifically there was a glaring lack of tropical convection in the Pacific and no mechanism to either divide or loosen the torrent of flow in the Pacific that largely killed our winter. This was very evident in the ensemble data where it seemed impossible to breakdown the prevailing ridge which dominated the lower latitudes of the Pacific.

Finally, it is inevitable that those in the field will be asked about "global warming", "climate change" or whatever other trendy term is being used to describe the warming global temperatures trend that seems to have matched the beginning of the industrial revolution. More specifically though is how to place this recent winter in the context of global warming. My answer and advice to this is to try and avoid it. Statistical noise and variability that is location specific, even spanning the course of a season, is insignificant in this conversation and proves very underwhelming when looking at trends that include the entire globe. Extreme weather events when spoken of individually and in one location should also not be part of the conversation. Temperatures across the eastern half of the U.S. between November and March were in many areas the warmest ever recorded over that period. Across the globe however temperatures in January and February of 2012 were very similar to and perhaps even colder than 2011. In other words, the warmth this year was location specific and was not part of a upward global temperature trend upward. In addition, there are much more ambient factors in a season that will dictate the outcome of a winter in a "globally warmed" winter and one that isn't. In other words, this winter if dominated by the same ambient forces would have also been mild and void of snow in 1912 just as it was in 2012.

If one is to frame the above-question a little differently however and ask the following. Would 2011-2012 been less warm without the impacts of global warming ? This I would have to answer a little differently. The data demands it does. It is estimated that winters in Vermont since 1990 are about 2-degrees warmer than winters in the 100-years prior to 1990. It is as clear as night and day. Yes, the data is still location specific and even periods spanning 20-year increments can feature statistical noise, but not that much statistical noise. Standard deviations for temperatures data spanning of 5-month cold season are between a degree and a degree and a half. This means more than half of the winters after 1990 are beyond a full standard deviation above the statistical mean. These things don't occur by accident, they don't occur because one anomalous winter such as the recent winter is skewing the data. It is in this case that Vermont is part of a larger global trend toward warmer temperatures. It means that yes the 2011-2012 winter would have been warm regardless but was likely warmer because of the effects of global warming. It means that the winter of 2010-2011 would have been colder without the effects of global warming. Fortunately, at least so far, the warming that has been prevalent the last 20 years is not translating to less snow. There is no evidence as of now, to suggest that the trend toward warmer temperatures is also part of a trend toward less snow. Snowfall in Vermont has remained relatively consistent.

Anyway, that is enough for this year. Thanks again to the Mad River Glen & Vermont skiing community for again being such a great audience to talk weather with. I couldn't motivate myself to do this without all of you. It has been a tough stretch thanks to Hurricane Irene and the warm snowless winter but better times are ahead. Have a great summer !!!

Sunday, March 25, 2012

Ugly season undergoes total meltdown

Weather more typical of June perhaps even July struck MRG the lethal blow. It was perhaps the most anomalous stretch of temperatures I have seen in the last 20 years or so. Anyway temperatures are back on the downward trend and we are about to enter a stretch of dare I say, winter-like temperatures. It will start Monday with temperatures hovering near the freezing mark and then dropping to near 5 across the interior Vermont high country Monday night. Temperatures will climb back into the 40's during the middle to later part of the week but snow is possible over the weekend from what could evolve into a significant late season winter storm.

With the season ended, we won't spend too much time sorting through the drama. I will do a season wrap-up in the coming days and then call it a year.

Sunday, March 18, 2012

Amazing stretch of March warmth to gain even greater stature this week

Temperatures for the last week have averaged 12-15 degrees above normal, reaching the 60's twice and the 50's on 3 other occasions. Statistically, that is pretty remarkable but it will be surpassed in the coming days by another incredible stretch of warmth. I always think it is kind of silly to describe events as "record breaking" since there is a big distinction between "recorded history" which stretches back about 100-150 years and actual history which stretches back billions of years. More accurately, we can describe the coming days as weather more typical of early June, nearly 3 months from now. Temperatures will reach the 70's in low lying areas on three successive days beginning Tuesday. These types of temperatures will not only end the ski season prematurely but it will likely initiate the 2012 growing season a good month before last year.

March is most certainly an "anything goes" type of period in the calendar. Many times, March is the highlight of the ski season with winter storms providing big time powder and average bases often times peaking in the middle to later part of the month. In 1998 we had a few big dumps in late February and early March. Toward the end of the month we had a similar push of warmth which brought temperatures to 75 on successive days and I remember skiing "chute" in shorts. Unfortunately, the warmth has already done a number on the limited snow in Vermont but shorts is nonetheless the advised attire.

Cooler Canadian air will bring temperatures back into the 50's this upcoming Friday. This happens in front of a more organized weather system which will bring rain to the region Saturday. By Sunday, arctic air will return to the region and the period that follows (the last full week of March) could actually get a little winter-like.

Monday, March 12, 2012

Maritime air to finally slow the advance of Spring

The mild air has done a number on the snow cover in low lying areas. The remnants of winter 2012 are now confined to the high country. Where the snow remains, the skiing has been great from what I hear with warm sunshine providing some of the softest snow of the season.

The warm weather and sunshine combination is likely at an end this week. Clouds and rain will prevail for much of the day Tuesday and this precipitation could end as a little wet snow Tuesday night as cooler "maritime" air backdoors its way into interior New England. Much of the rest of the week will likely stay on the cloudy side and although temperatures will remain above freezing for the most part, readings should stay in the 30's and 40's. The next system will brings its moisture into the region Friday in the form of a cold rain (maybe some ice in the highest elevations).

The rain should clear out by midday Saturday and the clouds by Sunday. After that, temperatures will again turn very warm with the help of sunshine and wherever the snow remains, some good spring skiing could certainly be had. 60-degree temperatures are again possible next week before the mild pattern finally breaks down and gives way to an extended period of more typical March weather.

Thursday, March 8, 2012

A bit of powder for Saturday, believe it or not

This comes less than 48 hours after 60-degree temperatures at the base of MRG and it will come before another extended round of spring-like weather. In the meantime cold weather is interrupting an incredibly mild March pattern. It will be a fitting encore of sorts.

The system responsible for the Saturday powder will arrive late Friday. It is a rather vigorous piece of upper level energy but it will move in and move out very quickly and has limited moisture. After temperatures hover near the freezing mark on the mountain Friday, flurries and snow showers will begin during the evening and continue into the overnight. By Saturday morning, the snow will be over and out and be replaced by wind and a very modest bit of chill. Overall, we can expect to see between 3-6 inches of powder, enough for a few decent turns Saturday morning. Temperatures will remain below freezing through Saturday night but sunshine and southwesterly breezes will move readings into the 40's again on Sunday afternoon.

A back door front could bring some maritime air into Vermont next week keeping temperatures within ten degrees of normal. Other than that though it will be mild with temperatures reaching 50 on at least 2 days next week and a good chance for rain on Monday. The upper ridge responsible for all this is capable of bringing record breaking high temperatures to many areas. It is the strongest upper level feature in the northern hemisphere over the next 7-10 days and it will leave its mark and potentially end many ski seasons across the eastern United States.

Sunday, March 4, 2012

Cold weather to quickly give way to an early round of Spring

Cold weather returned to the mountain today but that is about as much positive news I have if your still hoping for snow. As far as winter weather is concerned, the pattern going forward is just putrid. Anchored mostly by a very positive AO and another tightening of the jet in the Pacific, the weather will turn spring-like on the mountain. Over the next 2 weeks we can expect 4-5 days where temperatures exceed 50 and probably one day where readings reach the 60 degree mark. It will be a very embarrassing way for the month to conduct itself since over the years we have been accustomed to some of our best powder days in March.

A clipper system rotating through the eastern North American trough was the one real chance for snow in the near term. This system however will travel well south of New England and spread some unusual snow to southern Virginia. The system will help maintain the generally below freezing temperatures through Wednesday morning but with the help of sunshine and strengthening southwesterly winds, temperatures Wednesday afternoon could approach 50 in valley locations. Thursday will also be very spring-like with readings surging well into the 50's at the base and into the 40's at the summits.

The first round of mild weather will be interrupted by the arrival of a cold front Thursday evening. This weather feature will bring a period of rain to the mountain followed by more seasonable temperatures for Friday. The mild weather will make a quick return however with 40 degree temperatures again possible by as early as Saturday afternoon and the latest Sunday. More 50-degree temperatures are then possible throughout next week. By that point, the unsettled weather will become focused on the west coast allowing a very large ridge to develop across the center of the country. Mild weather will thus dominate not only the east coast but a large section of the eastern two-thirds of the United States. If the ridge does shift to the central U.S. it could open the door for cooler temperatures to thwart the warm-up in northern New England for a few days next week. That however is about the only thing that could save us from a record-breaking March blow torch, one certainly capable of making a very pathetic 2011-2012 winter, a memory.

Friday, March 2, 2012

Some snow early Saturday Morning, big thaw looking more likely next week

The next weather system, with its big warm push of air will eventually bring some ice and then some rain on Saturday. The cold air however will be able to hold its ground just long enough for what could be a brief but significant burst of snow in the early morning hours Saturday. Significant enough for a few inches before the lifts start churning and since temperatures will remain close to the freezing mark Saturday morning, a few good turns could still be had. By the afternoon we should see temperatures soar in to the 40's and this will be accompanied by some rain.

Beyond Saturday the outlook has not changed too much. Much colder weather along with some snow showers will move back into Vermont Sunday and Monday. The snow showers could dust the mountain with a light accumulation but I would not expect much. After a dry and seasonable day Tuesday, the big thaw is looking more likely. So long as the base holds up, the spring skiing could be quite good. Fundamentally however, the pattern could not be much worse with the three major teleconnection indices aligning in a very unfavorable way. Even when the mild weather abates toward next weekend, a second round of very warm weather will be poised to make another big dent into the winter.