Think Snow, Tweet Snow !!!

Monday, November 24, 2014

Quick hitting 5-10 incher Thanksgiving eve/day followed by an early season body-blow

The near-60 degree temperatures took the wind out of our November sails so to speak. The pattern has one more good amplification left in its stash however and that comes Thanksgiving-eve into Thanksgiving day. More than anything, I hope its a preview of things to come since this jet amplification will tap into the more active El Nino fueled southern branch of the jet stream. The weather system will cross north-central Florida late Tuesday and progress up the Atlantic coast Wednesday. The storm will undergo some rapid deepening particularly late in the day Wednesday and this combined with it's already attained moisture will make the weather system a formidable one albeit quick moving.

Wednesday is a massive travel day, and the storm prospects of a storm and its potential impact on East Coast metropolis conglomerate has many weather personalities and forecasting outfits debating the potential impacts. For the I95 corridor it  is an interesting debate of whether some of the impressive dynamics associated with this storm, can on its own, overwhelm a very limited supply of available cold air at the surface. I will leave this debate for others to partake. Our debate pertains only to amounts of snow, which is a much more preferable argument to the rain/snow argument. Snow, and only snow, should begin mid-afternoon Wednesday and continue through about half the overnight. Some of the heaviest precipitation is likely to fall south and east of North-Central Vermont but snowfall of the light to moderate intensity for several hours will be good enough for a 5-10 inch snowfall.

Thursday and Friday are both dominated by chilly weather, at least for November standards. Terrain induced snow showers on Friday could bring an additional few inches to parts of northern Vermont. After that we head into early December and some early season rough-sledding. We will lose support from nearly all of our favorite teleconnections, particularly the PNA which will reverse signs by late November. Cold will fight for partial control of the weather across interior New England but we will have several mild days between at least the 1st and 9th of December. To be perfectly blunt. We will not be able to continue this early season momentum and will have to endure a break.

I think mild pattern will run it's course by around the time of December 10th. Ensembles are only showing some weak signs of a more neutral set up by then but it's early.

Friday, November 21, 2014

Lots of signs pointing in a similar direction - A big 2014-2015 !!

Winter 2014-2015 is coming in with a vengeance, the Green Mountains have been whitened and the mood is clearly appropriate for some preseason prognosticating. This is year 10 of the SCWB. It started with sporadic emails to Eric in 2004 and it continues now with blogspot, twitter and our own urban dictionary of weather terminology designed specifically for the avid New England powder hounds. The blog continues this year and will at least start with plenty of anticipation. The pattern, currently anchored by a magnificent looking positive PNA structure has delivered widespread cold to eastern North America. But even more intriguing is the combination of what appears to be at least a mild El Nino, a positive PDO and another impressive expansion of snow/ice in the Northern Hemisphere. Are these the ingredients for a round of 1977-1978 style fireworks ? Or will the welcomed addition of the southern branch of the jet stream deliver all of its goodies to Pennsylvania, New Jersey and points south like 2009-2010 or even worse, will the winter STB like 1991-1992 after a chilly November. Worthy of some discussion at the very least. I have added some links to further explain some terminology. Most of them go to Wiki (And I encourage contributions to them). 

After a 4-year hiatus, El Nino has returned, and over recent weeks has been gathering strength. The state of the ENSO continues to be one of the more reliable ways to predict behavioral patterns of weather in a given season, particularly winter. It can be particularly useful when trying to pinpoint the frequency of specific occurrences. And it is especially relevant  this year given its 4-year absence and the general presence of La Nina at varying degrees of intensity over the past 4 years. The strength of an El Nino is determined by the strength of positive sea surface temperature anomalies in the equatorial Pacific Ocean. There has been much discussion from the National Weather Service's Climate Prediction Center about the potential ENSO event this year and in spite of much discussion, El Nino, has been slow to manifest.  In the last 30 days however, sea surface temperatures in key regions of the equatorial Pacific have warmed to about 1 C above normal. Typically this is about the threshold where we see miner ENSO impacts become more significant. These impacts include a suppressed and active jet stream in the Pacific fueling a potent southern branch of the jet stream. A jet stream capable of relieving California of its 2-year drought, bring significant snows to the southern Rockies and heavy rainfall from Texas to the southeastern states. Quite often, these many juicy weather systems culminate their trip across North America by evolving into major East Coast weather systems. Temperature impacts have also proven to be substantial, especially during the bigger ENSO events. The persistent throng of energy in the Pacific can counteract the southward advance of arctic air. Much of the Northern Plains, Upper Midwest and most of the eastern two thirds of Canada typically see above normal temperatures during a significant El Nino. The most egregious example was 1998, where water temperatures warmed to over 2C above average. Mad River enjoyed a fun-filled winter with plenty of juicy winter storms, but it was warm and the season was interrupted by a damaging ice storm in early January which required herculean efforts by many coop volunteers to clean the woods of debris. This year's El Nino, like all the others since,  won't even be half the strength of 1998 and the result of this, we hope, is that we see more of the typical impacts of precipitation as opposed to temperature. I will point out that 1998 is often used as a reference point for many global warming/climate change deniers. "We haven't globally warmed since 1998 !" you will hear, or some version of that. Statistically that is true when using 1998 as a reference point since the 3-Sigma El Nino of that year provided for additional and significant temperatures perturbations globally and thus many years since have been cooler than that globally. Statistics have been and will continue to be manipulated to suit all sides of every argument but that is one that has always bothered me. Back to our present weather situation. Many might remember 2009-2010, the last El Nino winter and the heart-ache in northern Vermont as the snow piled up well to our south while General Stark enjoyed mostly dry weather for long stretches of time.  Yes that could happen again but the adverse storm track of  2009-2010 was primarily due to the extremely negative Arctic Oscillation that accompanied that El Nino that year. We like negative AO's but not that negative ! It is unlikely that combination will prevail again this year.

The PDO has earned its place in the preseason discussion and like the ENSO, the index is defying the most recent 4 year history. The PDO (Pacific Decadal Oscillation) describes the configuration of sea surface temperatures in the mid-latitude Pacific, above the equator where we monitor ENSO. Around the time of 2007, the PDO had its multi-decadal shift going from an index that was mostly positive to an index mostly negative. It is not a rule without exceptions, the PDO can be in a negative decadal phase and have a positive year and vice-versa. It just has decadal tendencies, which is how the phenomenon was discovered and although we are in a negative tendency, it appears we will have a positive year. We went into last season with a negative index but it turned in January and the index remained positive through March. The index could switch this year but will at least start the season positive. The sign of the index does have a tendency to be correlated with the ENSO but not entirely. In the case of this year, the development of the El Nino seems to have gone hand in hand with the evolving positive PDO. Why is the positive PDO significant ? The long wave or jet stream pattern can often have a difficult time locking in place with a negative PDO as illustrated during the winters of 2011-2012 and 2012-2013. Often times, cold and snowy weather can occur only to be abruptly interrupted by a intrusive thaw. A positive PDO favors the ridge west/trough east regime and these regimes can remain in place for longer periods uninterrupted.

I want to bring up an important side note related somewhat to the PDO. I want to aknowledge an important driving force behind last years cold weather, the repeated PV invasions and I also want to aknowledge an individual who pointed this fact out on more than one occasion last year. We mentioned the persistent Alaskan jet stream ridge as the catalyst behind much of the cold, but an old colleague of mine, Joe Bastardi, referenced that a driving force behind that particular weather feature was a large area/bubble of warm water in the Gulf of Alaska. This very large bubble of warmth blossomed in December of last year as the PDO switched from a negative to a positive phase. Bastardi style of self-promotional forecasting is something I take issue with at times and I particularly don't like his invariable bashings of the National Weather Service, which employs many talented meteorologists, who by law are not allowed to defend themselves against his repeated attacks. That said, Bastardi did point out the importance of this bubble of warmth in the Pacific and I think he's right, it was significant. This large area of warmth remains positioned in the Gulf of Alaska but it has shifted eastward slightly and the configuration of water temperatures now resembles the classic "red-horseshoe" look of the traditional positive PDO. 

The real fun begins when we start talking about the autumnal expansion of snow and ice in the Northern Hemisphere this year. It wasn't going to be easy but it was achieved. We actually bested last year's monster October snow cover number of 21.01 millions of square km and chimed in this year with a 22.88 number this year. The 2nd highest in the very brief 47-year history of recorded data. Some of the recent November weeks are running almost 4 millions of square km above last year according to our friends at the Rutgers University Snow Lab - . Lets dumb this down a bit this year and look at some big years in this 47 year history of recorded data. Here are a list of big autumn snow cover years (at least 1 STDEV above normal)  in the Northern Hemisphere and the corresponding result in Vermont. 

Year    Snowcover      Temp         Snow 
1970    21.84          Cold         Totally Epic
1971    21.53          Cold         Snowy
1972    21.52          Mild         Sucky
1976    25.72          Ext/Cold     Snowy
2002    23.24          Cold         Snowy
2009    21.01          Warm         Normal 
2013    21.01          Ext/Cold     Slightly Snowy 

By contrast here are some low snow cover years and the corresponding result. 
1979    14.68          Normal       Sucky
1980    13.61          Cold         Normal 
1987    13.35          Warm         Sucky
1988    12.78          Warm         Beyond Sucky
1990    15.58          Warm         2x Beyond Sucky
1994    14.23          Warm         Sucky

There are a few exceptions on both sides of course and it is hardly a perfect relationship. In fact, there are some recent years where snow cover was within a standard deviation of normal (but still above or below the normal) in the northern hemisphere and the weather in Vermont did the opposite of what this illustration is trying to display. That said, the 22.88 number is a strong signal and if past history is any indication, the colder weather will win a majority of the battles this year as it did last year. 

In a poker game, players use the term "tell" to describe a behavior or a demeanor that might give competitors a clue as to the nature of a players hand. I look at the weather the same way. By early November, it starts to exhibit a behavior that typically foreshadows the nature of the winter. It doesn't work all the time but it earns it's place as a contributing variable in the preseason discussion. This year it is a pretty obvious one. We have just been slammed with the strongest attack of November cold in more than a decade across the eastern half of North America. Lake Effect snows totaling over 8 feet and temperatures that are as much as 25 below average all supported by a classic positive PNA structure. It is a pattern I would expect we should see repeated a few times this winter since it is one that we do typically see in positive PDO years. What we need to really hope for is the support from the active southern branch of the jet stream, which will be catalyst for several monster east coast events 1978 and 1994 style. 

Needless to say I am pretty stoked about the upcoming winter. And yeah I am inherently stoked before every winter and I try and provide that disclaimer to account for the bias, but this to me is the most impressive collection of indicators we have seen in the last 10 years for a cold and snowy winter. It will also likely be a collection of indicators  not surpassed in the 2nd 10 years of the SCWB, if we can achieve that longevity. El Nino is providing us with some needed added southern stream juice, PDO is having a counter-tendency positive year, there is a mammoth amount of early Northern Hemispheric snow cover and the weather pattern has already exhibited a need for a big positive PNA outburst. Could we crap out like '91 ? Anything can happen and preseason forecasts can be inaccurate. I am probably about 60 percent confident about this forecast as opposed to my normal 55 percent preseason confidence. 1991, by the way, was a stronger El Nino year with a widespread and rather strong attack of November cold. The winter then proceeded to fall completely flat and turned out to be quite warm with a glaring lack of snow. The snow cover number that October though was 15.58 millions of square km. We were over 7 million square km above that this past October. With all that said, I expect, only for the 2nd time, for Vermont to see a colder than average winter and I expect some above average snowfall along with that. An additional shorter term update will follow in the coming days which will include some snow around Thanksgiving and a temperature moderation for the early part of December as we lose teleconnection support.  

Saturday, April 19, 2014

2013-2014: A cold winter with a satisfying finish

The winter 2013-2014 is reaching a conclusion and if nothing else has earned a distinctiveness that should set it apart in our memory. 2011-12 will be remembered for all the wrong reasons and 2012-2013 was hardly distinctive at all. 2013-2014 however was remarkable in many ways. Most notable is the persistent cold. The period starting November 1st and ending March 31st was approximately 4 degrees below average and every month within that period was below average, culminating in March which was nearly 10 below average. All of those 3 occurrences are statistically impressive. The winter of 2013-14 defined by those 5 months is the coldest in over a quarter century and going back 50 years, only the winter of 2002-2003 featured 5 months of below normal temperatures in succession. March of 2014 was truly the grand finale. Relative to normal, it was the coldest in Vermont since the commencement of the blog 10 years ago. 

For some of our recent down years, the cold has been the missing ingredient in the weather pattern. This was not the case for much of 2013-14 but in spite of that, we had some struggles on the snow side that seemed to become statewide household knowledge. Every discussion relating to the weather seemed to refer to Vermont's lack of snow relative to the rest of the geographic world. This was very much an intuitive observation and was made by some very casual weather observers to say the least, even from people outside the state.  Intuition or not, the observation proves to be quite astute statistically in a relative sense, and is the 2nd most notable characteristic of the recent winter. Consider New York City receiving 56 inches of snow, Philadelphia 66", Detroit 94" and Chicago 81" all between 180 and 300 percent of normal. In the case of Michigan, many locations saw the snowiest winter ever recorded. Thanks to a big late season push, Vermont also saw above average snowfall but it wasn't by much and we were below average for the first two-thirds of the season. The big snow season in the Great Lakes region compared to the near normal season in Vermont I find particularly strange since the two regions are often on the receiving end of the same big storms, evidenced by the recent winters of 2010-2011 and 2007-2008. 

In spite of this, the season finished on a strong note and ranked better than the previous two. The mountain saw no rain in March until the very end of the month and only witnessed three 40-degree days. Compare that to 2012 which saw near 80-degree temperatures and a quick end to a miserable season by the early to middle part of the month. In a relative sense, we performed poorly but it was a solid season statistically that continues for portions of the high country both in Vermont and New Hampshire. 

There were two very important factors driving the particularly intense cold weather this season. I always tell people that from the standpoint of temperature, a winter is measured by the strength of the cold during the coldest periods. Outbreaks of cold this past winter were especially strong relative to normal and exceeded almost anything we have seen since January 2004. There will be differing opinions as to what root cause prevailed on the atmosphere during the winter but my opinion is that one relates to a feedback that started early last autumn. An unusually high build-up of early-mid autumn snow in the northern hemisphere helped the pooling efficiency of the polar air masses at high latitudes. The cold air effectively worked its way into mid-latitude North America early in the year, freezing the Hudson Bay on the earliest date in a decade and ultimately freezing 80 percent of the Great Lakes aggregate by late January. Freezing large bodies of water such as the Hudson Bay or the Great Lakes turns them into an additional breeding ground for cold. I felt as if almost every cold front this winter marked the leading edge of not just garden variety cold, but extreme cold of 20-30 degrees below average. The outbreak of cold and snow we received this past April 16th underscores this point. 

The second factor refers to a much talked about topic in recent winters the "Evil Empire". The "Evil Empire" coined a few years ago describes the phenomena of large upper trough over large upper ridge in the vastness of the Pacific Ocean. The tightened jet stream which results from such an occurrence is so destructive for all of eastern ski country including Vermont and it was especially destructive during all of 2011-2012 and for a large portion of 2012-2013. There is a teleconnection index that essentially measures the strength of the "Evil Empire" called the Eastern Pacific Oscillation. A positive index indicates tightness in the Pacific Jet and the presence of the "EE" while a negative index refers to a looseness in the jet over the Pacific and the absence of the "EE". In spite of a flare-up here and there, the "Evil Empire" was largely a non-factor and the predominant feature in the up-stream jet configuration was a large upper ridge covering Alaska. There were interruptions but the Alaskan ridge was an incredibly persistent force throughout the winter, channeling cold from that region, straight into the middle part of North America, specifically the central provinces of Canada and the Midwest. The cold attacked the northeast as well but the brunt of it was felt across the central third of North America. The Alaskan ridge was a welcome change from winters of recent past but still at times was the catalyst for a detrimental storm track. The most ideal storm track for interior New England places a ridge over the western part over the Yukon or even the Northwest Territories of Canada. The placement of the ridge so far west allowed storms to ride up through the Great Lakes on several occasions both in late December and then again in that devastating thaw we saw between January 10th and 14th. The aforementioned January thaw was especially destructive since it consisted of nearly 80 hours of above-freezing temperatures there was no quick recovery to be found "In the wake of the flood" (Small GD reference but necessary since I am listening to some random GD concert as I write this). 

Ultimately the cold won the day and the months of February and March. The long wave pattern was able to flatten just enough to allow storms to take a more favorable track for snow across interior New England. The two big storms basically occurred exactly a month apart and on the anniversary of two of our favorite snow blitzes of the last quarter century. The first was a big, moist coastal bomb on Valentines Day and the second came at us from the Ohio Valley and occurred on March 12/13. Both delivered snowfall amounts just shy of 2 feet and produced outstanding stretches of skiing at MRG. 

We finally have some hard-earned warm weather to enjoy and with that the SCWB signs off for another season. I was fortunate enough to ski at MRG 8-days this winter (more than the previous two) and met some more great people. If you read the blog but typically ski or ride elsewhere you should certainly make plans to visit MRG in 2014-2015. It's a special place, especially in an era where skiing has experienced some hyper-commercialization. Enjoy the summer everyone, we will meet again come late this fall. 

Tuesday, April 8, 2014

MRG season to conclude with warm temperatures, soft snow and mostly rain-free

I have to confess I am a little tuned out on winter and snow thus the blog got a bit neglected. In spite of that, and the recent stretch of above-freezing days, deep snow remains across the high country of interior New England. MRG appears to be skiing quite nicely in spite of some recent rains and if you have been waiting for that sunny, good visibility day to attack the spring skiing then your wait will soon be over. Both Wednesday and Thursday should feature healthy doses of sunshine and warm afternoon temperatures, particularly Thursday where readings should climb into the 50's. Clouds will be more prevalent and we could see some light rain Thursday night or Friday but it shouldn't amount to much.

This brings us to the conclusion of the season at MRG and the weather appears as if it will cooperate. Clouds will gradually give way to some sunshine early Saturday, visibility will improve and temperatures will surge toward the 50-degree mark. On Sunday, clouds and moisture associated with a stronger push of warm temperatures will skirt northern New England but I think much of the wet weather will be confined to the St Lawrence Valley. There remains some disagreement amongst the models regarding this question but my educated guess is that the mountain stays dry although there could be more in the way of clouds. Once again, Sunday's temperatures should at least approach the 50 degree mark.

MRG will end its season Sunday, just in time for some 60 degree temperatures Monday followed by heavy rain possibly thunderstorms Monday night or Tuesday. A strong push of below normal temperatures along with some snow is then likely for the middle of the week. I know the skiing will continue for some but the blog will conclude with a final season wrap-up early next week.

Friday, March 28, 2014

Challenging forecast Saturday night involving exploding east coast storm

Very tricky forecast for Saturday night as a storm is expected to explode in the vicinity of the Delmarva and spread precipitation deep into New England. Temperatures are very, very marginal this weekend but the National Weather Service is concerned enough about a potential "heavy wet snow event" that they have posted a Winter Storm Watch for much of the region, MRG included. The justification for this comes from data released by successive runs of a higher resolution short term model. Other data from the more globally gridded, lower resolution medium range models suggest a warmer storm and mostly rain for areas below 2,000 feet. I am inclined to believe that this is a elevation sensitive event, especially when talking about snowfall totals. When some of the heaviest stuff is falling overnight Saturday, precipitation should be a gloppy snow but accumulations will be most significant across the high country, particularly from the mid-station up. When precipitation is not as heavy, it will likely fall as rain in the valley's and remain snow or mixed precipitation across the high country. There is a substantial amount of moisture associated with this storm and if we can keep most of this snow on top of the mountain, it could get very deep, even upwards of 10 or more inches. I don't expect Rt 100 to receive more than a gloppy inch or two and the base of MRG might even struggle to get anything more than a few wet inches. There are also indications of some invasive warm layers in the atmosphere that could change everyone to rain Sunday as precipitation lessens in intensity.

This remains a much more "spring" oriented pattern which means plenty of above freezing days over the next week. Monday through Wednesday will see readings into the 40's during the afternoons. By then end of the week, another significant storm system could impact the region. Temperatures may not be cold enough to support snow but I would not completely rule it out, especially this winter. The weekend of April 5th and 6th should see a return to below average temperatures and this could extend through part of the following week. Blogging for the duration of the season will be dependent on how late the mountain decides to stay open. I know there is some deep snow out there still but if MRG decides to ramp down the hours, the SCWB will do the same.

Tuesday, March 25, 2014

Some spring thawing is finally eminent beginning late this week

The big noreaster swirling off the New England coast did not provide the fireworks we hoped it would but this wasn't entirely unexpected. Meanwhile, unusually intense late-season cold is keeping the mountain quite frozen. We saw widespread sub zero temperatures Tuesday morning and we should see more of the same Thursday morning before temperatures finally take a late-day run at the freezing mark. The exiting cold will allow a more spring-like weather and temperature regime to commence over the mountain. There will be extended periods, beginning Friday, of above freezing temperatures thus allowing for the significant amounts of March snow to corn up and soften quite nicely. This being said, the warm weather does not appear to be particularly anomalous nor does it appear to be as significant as what I had advertised a few days ago. Nonetheless, it will mark the first significant shift toward spring-like weather on the mountain and most notably, will provide the opportunity for the "R" word to re-enter the vocabulary. 

Incredibly, the mountain has only touched 40-degrees one time this month which is quite an achievement in March and would be noteworthy even in January and February. Friday will be the second such day. Model data is suggesting that clouds would keep temperatures in the 40's but a few hours of sunshine could certainly boost readings to 50 near the base.  The extensive cloudiness and numerous weather systems over the next week is the big reason why the mild weather will be mitigated verses some of my own earlier expectations. A weather system Friday will weaken as it makes its approach late in the day but will bring a period of light rain to the mountain anyway. Temperatures will remain above freezing (high 30's or low 40's)  throughout Saturday underneath more cloudiness. Another and stronger storm system will then approach from the southwest and promises to bring more rain Saturday night which could end as some wet snow Sunday morning. 

The weather continues to look mild through the early part of the week with at least two days of 45 and perhaps one of these above 50. Another storm system could spread rain into the region Tuesday which yet again could end as some wet snow before colder weather arrives for the middle of the week. The break in the cold can somewhat be attributed to a huge surge in the AO index (The NAO also made a less significant surge). The index of both of these teleconnection indices is expected to be neutralized and perhaps even go negative by the first weekend in April. This would provide a brief window where we could see another round of wintry weather. Overall though, the thaw will finally be on across interior New England after one of the coldest month of March in half a century. 


Friday, March 21, 2014

Some snow and lots of cold for next 5 days but finally hints at some spring warmth on the horizon

Friday's snowfall brings the mountain to the 200-inch benchmark for the season. March has been nothing short of tremendous. We have yet to receive a drop of rain and have nearly 50 inches of new snow to play in. Saturday's storm track has moved north since the last update and it puts the mountain at the bottom edge of some of the best moisture which appears a bit more limited. Snow should begin around 9 AM Saturday morning and persist through a good part of the ski day. Total snowfall should be in the 3-5 inch range by Saturday evening.

The very impressive outbreak of late-March cold arrives for Sunday sending temperatures back into the teens and then back below zero Sunday night. More snow showers are possible for Sunday adding to the light accumulation from Saturday. The 25-30 degree below normal temperatures will solidify March of 2014 as one of the coldest in the last 100 years for interior New England. Records and statistics aside, the cold has been axiomatic as much of the state has added to snow depths this month as opposed to seeing any significant melt.

There has been a considerable amount of chatter regarding a storm in the middle of next week. As each day passes, it appears as if the storm is a threat mainly for the Mid-Atlantic states along with coastal New England. The storm will have an inverted trough (as some call it) that will progress east along its northern flank and may spread some snow into Vermont and New Hampshire on Tuesday night into Wednesday, but the snow appears to be light in nature. Mainly the Monday-Wednesday time frame will be cold. Depending on cloud cover, temperatures may struggle to reach 20 all three days.

There is finally some significant signs of a major shift in the overall pattern and one that would lead to the first substantial thaw of the spring season. Part of it can be attributed to the NAO which will shift into positive territory. Most of it however appears to be related to energy in the jet stream that is anticipated to be trapped across the mountain-west late next week. Temperatures will begin to moderate Thursday slightly but more so Friday. A storm system around the 30th may thwart part of this warm-up but ultimately there will be some very warm days toward the end of the month and into early April. The mountain has not seen anything close to 50 since the January thaw more than two months ago and certainly hasn't sniffed 60 since autumn. This stretch of warmth, which should peak very early in April will probably allow readings to eclipse both marks and finally provide the region with spring thaw and some spring skiing.