43 degree dewpoints, heavy rain and a tarnished MRG base is not exactly putting me in the Christmas spirit early this week. The Sunday/Monday storm turned into a fiasco and a major setback to what was a promising start to December. In truth, this resembles much of what was expected this winter, a roller coaster ride of weather results and in this case it was 30 inches of snow followed by over an inch of rain. The proverbial "silver lining" does exist and the high terrain of northern Vermont should make a rapid and an eventual full recovery.
Rain becomes light snow by Monday evening as temperatures slowly make a return to the freezing mark. We will then watch the sequel to last week and hope the sequel is as good as the original. Sunday's big rain-maker will get caught underneath all the high latitude jet stream blocking and a second piece of energy with a fresh supply of Atlantic Ocean moisture will migrate northwestward toward interior Quebec. Moisture from this system will arrive Wednesday and this should occur after an initial few inches of backlash snows Monday night into Tuesday. Snow totals between Monday night and Thursday will be in the 8-14 inch range and the high elevation areas will have a big edge.
Heavier snow showers will taper to flurries later Thursday and continue into Friday. Much of the country will have experienced some well below normal temperatures this week but readings in Vermont will be very ordinary ranging between the teens and low 20's. By this weekend, a weather system will be tracking into the Tennessee Valley and will bring both rain and snow to the Ohio Valley. Most of the model runs have taken this system well out over the Atlantic Ocean but we did get a European run this afternoon which allowed this system to develop into a major coastal storm and a big snow producer for most of New England. Its worth watching for sure but we should wait for more evidence before getting our hopes too elevated.
Even should any hypothetical late weekend storm turn into a "non-event" we should remain optimistic as the pattern remains anchored by a very negative Arctic Oscillation. The negative AO will peak in the next 7-10 days as a massive block covers the Baffin Bay and much of the southern Arctic Ocean. Another weaker block will remain in place across the Bering Sea. Much of the U.S. will thus remain in the firm grip of below normal temperatures as a result of all this. Temperatures across Vermont will remain close to normal but smaller disturbances should allow for powder possibilities through the Christmas holiday. Stay dry this Monday, new snow and a return to winter is not far away.
Sunday, December 12, 2010
Thursday, December 9, 2010
Storm Sunday/Monday to bring rain than snow....
but the pattern will be generally favorable through the time of the winter solstice and this sets the mountain up rather well for the holidays. The storm in question is a "BC bruiser", and a rather innocent looking one it will be as it crosses into southern Alberta and dives southeastward from there. The storm will get turbo charged by a huge injection of polar jet energy which will more or less bomb the system out before it even interacts with the Atlantic Ocean. This is a bit problematic for interior New England since surface pressure's associated with this weather system will be so low before it even crosses the Appalachian Mountains thus making it difficult for a successful transformation off the Atlantic Coast. Many storms that track in this fashion lay flatter and are initially weaker but this one will be quite strong and will be standing quite upright and thus envelop warm Atlantic Ocean marine air across New England. The result will be a widespread rain event across southern New England and a mixed precipitation to some rain type of event across northern Vermont. Since the mountain has yet to open, it isn't the end of the world but it be good if we can keep dewpoints close to the freezing mark and keep the wind down. Both are huge factors relating to the rate at which snow can melt. The former appears better than the latter as I would guess dewpoints remain in the 30's but the wind gets whipped up pretty good by early Monday morning.
This storm, like the prior event will also get caught underneath the mammoth block over Greenland and as temperatures rapidly turn colder late Monday, moisture from the trapped system will rotate back over New England and deposit some additional snows across the region between late Monday and Wednesday. Snow totals in this period could approach a foot but its a bit early to tell for sure. With a solidified base and some additional snow next week, the mountain could be in good enough shape for an opening on MRG's target date but much will depend on the damages done Monday morning.
Teleconnection indices remain rather favorable as I mentioned above let mostly by the Arctic Oscillation which will remain very negative. The block over Greenland will migrate into eastern Canada a bit and will limit the region's access to any fresh supply of cold air after Tuesday even though it is not expected to be extremely mild (just above normal). The prevailing storm track however should be good enough to allow for the chances for additional snow from another storm toward the weekend of the 18th and 19th. More on that in a subsequent post Sunday.
This storm, like the prior event will also get caught underneath the mammoth block over Greenland and as temperatures rapidly turn colder late Monday, moisture from the trapped system will rotate back over New England and deposit some additional snows across the region between late Monday and Wednesday. Snow totals in this period could approach a foot but its a bit early to tell for sure. With a solidified base and some additional snow next week, the mountain could be in good enough shape for an opening on MRG's target date but much will depend on the damages done Monday morning.
Teleconnection indices remain rather favorable as I mentioned above let mostly by the Arctic Oscillation which will remain very negative. The block over Greenland will migrate into eastern Canada a bit and will limit the region's access to any fresh supply of cold air after Tuesday even though it is not expected to be extremely mild (just above normal). The prevailing storm track however should be good enough to allow for the chances for additional snow from another storm toward the weekend of the 18th and 19th. More on that in a subsequent post Sunday.
Monday, December 6, 2010
Snow totals adding up, big storm to watch Sunday/Monday
Light to moderate snow will continue through Tuesday before tapering to flurries Wednesday. With 10-plus inches of new snow the mountain will have a powdery finish and an appealing look but the base will remain shallow and appropriate only for your pair of rock ski's you would have otherwise advertised on Craigslist for $20. We do have a weather pattern anchored by a nasty Greenland Block and negative NAO and this will allow for the continuation of below freezing temperatures and is certainly setting the stage for an early season big storm and we will get our chance on the 12th or 13th of the month.
There will be two jet stream disturbances that will move quickly eastward out of the Pacific Northwest late this week and the weekend. The first, can be described as an alberta clipper which will spread light snow across the Great Lakes and ultimately interior New England early Saturday. This first feature can be compared to trying to start your lawn mower for the first time in two weeks. It will pull hard but the mower won't start and the moisture and upper air support will be lacking and so will the snowfall. We will hardly notice its presence in the end and will instead be focused on the second feature which will dig and dig hard as it progresses into the middle of the country. The amplification with this second feature (originating from the BC coast) will be very rapid and occur very quickly. Too quick for comfort perhaps as the surface low pressure center will gather steam in the Ohio Valley and like many storms during La Nina winters, head into New York state and interior New England. It will be a track that promises to bring the threat of all types of precipitation and although we have a chance for a major snow storm, precipitation could change to a sleet/freezing rain mixture and perhaps even rain. Hopefully this system can make an important jump to the coast before tracking up toward the St Lawrence Valley. Many storms which encounter a mammoth Greenland block such as this one will make this jump and we will need it here to make this event a big success.
Colder weather and snow showers will follow for early next week and with the negative NAO dominating the field of play, below freezing temperatures and continuous chances for snowfall will continue through 17th-18th of December.
There will be two jet stream disturbances that will move quickly eastward out of the Pacific Northwest late this week and the weekend. The first, can be described as an alberta clipper which will spread light snow across the Great Lakes and ultimately interior New England early Saturday. This first feature can be compared to trying to start your lawn mower for the first time in two weeks. It will pull hard but the mower won't start and the moisture and upper air support will be lacking and so will the snowfall. We will hardly notice its presence in the end and will instead be focused on the second feature which will dig and dig hard as it progresses into the middle of the country. The amplification with this second feature (originating from the BC coast) will be very rapid and occur very quickly. Too quick for comfort perhaps as the surface low pressure center will gather steam in the Ohio Valley and like many storms during La Nina winters, head into New York state and interior New England. It will be a track that promises to bring the threat of all types of precipitation and although we have a chance for a major snow storm, precipitation could change to a sleet/freezing rain mixture and perhaps even rain. Hopefully this system can make an important jump to the coast before tracking up toward the St Lawrence Valley. Many storms which encounter a mammoth Greenland block such as this one will make this jump and we will need it here to make this event a big success.
Colder weather and snow showers will follow for early next week and with the negative NAO dominating the field of play, below freezing temperatures and continuous chances for snowfall will continue through 17th-18th of December.
Friday, December 3, 2010
2010-11 season to start with a huge bang
Thanks largely to a well established upper-air block in the jet stream across Greenland and the very negative NAO which is a direct result. This is the very same feature which dominated the weather pattern last year, a year where the blocking was so severe and the southern branch so powerful that a succession of storms tracked well to the region's south. A similar pattern this year will yield much more fruitful results as the upcoming week will prove. Our live look at the MRG base might not show much in the way of snow at the moment but the view will be very different in a week's time and discussions of a very grand opening will pick up in earnest !!
Colder weather, which is dominating much of the central part of North America has been a little sluggish in its eastward progression leaving much of interior New England "above normal" though readings have fallen below the critical freezing mark across higher terrain. This will remain the case over the next few days as we witness the Midwest and deep south get a surge of chill by the 5th of the month. As the cold moves south, a storm will take shape across the Gulf of Maine and intensify very quickly. I alluded to this feature in the last post as a possible snow maker and it should prove to be of much greater significance than originally thought. As we progress into early next week, this storm will get caught under the all important Greenland block and retrograde into Quebec. As it does so, a moist conveyor will rotate into the northern Green Mountains and snow will begin to accumulate across much of northern Vermont although the high country will receive the biggest benefits. Between Monday and Wednesday snowfall totals could range in the 1-2 foot category.
The upper trough axis will shift east later in the week and temperatures should fall dramatically by Wednesday. Snowfall late in the week will largely depend on the available low level instability because the Champlain powder machine should be open for business (with the lake being unfrozen). It is tough to tell this early how deep that layer of instability will be but a subsequent post can fine tune that forecast.
Of more significance could be a more potent weather system which should exit the Rockies late next week and have a bit more moisture to work with as it proceeds east toward the region. This storm will be a product of a more consolidated jet stream this year and like many systems this year, the question will be its ultimate track and its ability to gather moisture from the Gulf Mexico since many such weather systems can struggle somewhat in this regard. Even at this early juncture I feel relatively confident for additional snows next weekend and this will make for a fantastic 7-10 days of early season skiing across northern New England. The even better news is the recent indication from the European Ensemble package which suggests a continuation of a blocked up and negative NAO dominated pattern through the 15th to 17th of the month. This will really limit the chances for any significant thaw or rain through the middle of December.
Lastly, I wanted to expand on this whole "favorability index" theme which will be a more objective measure of the three teleconnection indices that the SCWB keeps an eye on. The index is a cumulative measure of the NAO, PNA and AO over the next two weeks with the signs of the NAO and AO flipped. More importantly, a favorability rating of over "2" is excellent while anything under -2 is rather unfavorable. Hopefully this will keep me honest and perhaps keep me out of trouble !! Enjoy the early season turns.
Colder weather, which is dominating much of the central part of North America has been a little sluggish in its eastward progression leaving much of interior New England "above normal" though readings have fallen below the critical freezing mark across higher terrain. This will remain the case over the next few days as we witness the Midwest and deep south get a surge of chill by the 5th of the month. As the cold moves south, a storm will take shape across the Gulf of Maine and intensify very quickly. I alluded to this feature in the last post as a possible snow maker and it should prove to be of much greater significance than originally thought. As we progress into early next week, this storm will get caught under the all important Greenland block and retrograde into Quebec. As it does so, a moist conveyor will rotate into the northern Green Mountains and snow will begin to accumulate across much of northern Vermont although the high country will receive the biggest benefits. Between Monday and Wednesday snowfall totals could range in the 1-2 foot category.
The upper trough axis will shift east later in the week and temperatures should fall dramatically by Wednesday. Snowfall late in the week will largely depend on the available low level instability because the Champlain powder machine should be open for business (with the lake being unfrozen). It is tough to tell this early how deep that layer of instability will be but a subsequent post can fine tune that forecast.
Of more significance could be a more potent weather system which should exit the Rockies late next week and have a bit more moisture to work with as it proceeds east toward the region. This storm will be a product of a more consolidated jet stream this year and like many systems this year, the question will be its ultimate track and its ability to gather moisture from the Gulf Mexico since many such weather systems can struggle somewhat in this regard. Even at this early juncture I feel relatively confident for additional snows next weekend and this will make for a fantastic 7-10 days of early season skiing across northern New England. The even better news is the recent indication from the European Ensemble package which suggests a continuation of a blocked up and negative NAO dominated pattern through the 15th to 17th of the month. This will really limit the chances for any significant thaw or rain through the middle of December.
Lastly, I wanted to expand on this whole "favorability index" theme which will be a more objective measure of the three teleconnection indices that the SCWB keeps an eye on. The index is a cumulative measure of the NAO, PNA and AO over the next two weeks with the signs of the NAO and AO flipped. More importantly, a favorability rating of over "2" is excellent while anything under -2 is rather unfavorable. Hopefully this will keep me honest and perhaps keep me out of trouble !! Enjoy the early season turns.
Sunday, November 28, 2010
Big block over Greenland will ensure cold and some snow after Dec 1
A large upper air "block" has certainly established itself across Greenland over the past week. It has tag teamed with another high latitude blocking feature centered over the Bering Sea to allow arctic air to flood the country and will ensure a generally favorable early season pattern for the beginning of December. The benefits of the negative NAO will unfortunately not be felt until after the 2nd or 3rd of the month. The Bering Sea block has allowed a large trough to form across the inter-mountain west and this in turn will allow a large fetch of mild southerly to flow to establish itself across the east and this will flood the region with mild air very quickly on Tuesday. The rain will soon follow and rain it will to the tune of 1-2 inches. We might as well get this out of the way now because an event like this would have a devastating impact on skiing were it to come prior to the Christmas holiday.
So speaking from the standpoint of the MRG "base" we will be starting from scratch on December 2nd but a sustained period of cold weather will begin on that day. Temperatures will be seasonable through the upcoming weekend and by the looks of it, we will not have the instability for a big terrain induced snow event. There will be a lingering "baraclinic" area (you could say front) in the Gulf of Maine and this has the chance to stir up a bit of snow though the chances for accumulations will be best over coastal regions though much is left to be determined. The combination of better instability and even weak weather systems should result in some new snow early next week and hopefully by then we can start discussing a opening day party.
There is evidence that the block over Greenland will begin to break down around December 10th but our Bering Sea blocking feature will remain. The pattern will thus turn more variable but we should begin to churn out a few weather systems as we approach the middle of the month. There are a few additions or side features which should help to provide more of a numerical summary. Included will be seasonanal and 7-day snowfall totals at MRG and expected snowfall over the upcoming 7-day period. I will also include a favorability index. This will be a very generic, cumulative measure of the three teleconnection indices: the Arctic Oscillation (AO) the North Atlantic Oscillation (NAO) and Pacific-North American (PNA index. The AO and NAO index is favorable when negative while the PNA is favorable when positive. Thus for the purposes of the "favorability index", the signs of the AO and NAO will be flipped and added to the PNA index for a final total. This approach has weaknesses but it will be a simple non-subjective and numerical way of looking at the next two weeks since our newly devised "FI" will be calculated at 7 and 14 days.
So speaking from the standpoint of the MRG "base" we will be starting from scratch on December 2nd but a sustained period of cold weather will begin on that day. Temperatures will be seasonable through the upcoming weekend and by the looks of it, we will not have the instability for a big terrain induced snow event. There will be a lingering "baraclinic" area (you could say front) in the Gulf of Maine and this has the chance to stir up a bit of snow though the chances for accumulations will be best over coastal regions though much is left to be determined. The combination of better instability and even weak weather systems should result in some new snow early next week and hopefully by then we can start discussing a opening day party.
There is evidence that the block over Greenland will begin to break down around December 10th but our Bering Sea blocking feature will remain. The pattern will thus turn more variable but we should begin to churn out a few weather systems as we approach the middle of the month. There are a few additions or side features which should help to provide more of a numerical summary. Included will be seasonanal and 7-day snowfall totals at MRG and expected snowfall over the upcoming 7-day period. I will also include a favorability index. This will be a very generic, cumulative measure of the three teleconnection indices: the Arctic Oscillation (AO) the North Atlantic Oscillation (NAO) and Pacific-North American (PNA index. The AO and NAO index is favorable when negative while the PNA is favorable when positive. Thus for the purposes of the "favorability index", the signs of the AO and NAO will be flipped and added to the PNA index for a final total. This approach has weaknesses but it will be a simple non-subjective and numerical way of looking at the next two weeks since our newly devised "FI" will be calculated at 7 and 14 days.
Thursday, November 25, 2010
Winter 2010-2011: The revenge of La Nina !!!
It is the middle of November and the weather has been excruciatingly mild so it must be time to kick off the seventh season of Single Chair Weather Blogging. Preseason forecasts can be a mess to evaluate in hindsight for their inexactitudes, inaccuracies and unquantifiable subjectivities. It can generate some excitement an for me induce a sudden craving for Magic Hat's Single Chair ale, which seems to be in short supply during Vermont's stick season (someone will have to clue me in on where to find some out of season SCA).
The emails I have gotten, which can now be sent to josh.aaron.fox@gmail.com (as opposed to yahoo) suggest that the SCWB reader continues is getting more and more weather literate asking the tough questions months ahead of the time when they usually get answered. We have an impressive audience of "in the closet" and "out of the closet" weather geeks and this helps to make running the SCWB a lot more fun. The talk this year has mostly revolved around La Nina and rightly so. It has blossomed quickly, decisively and promises to be a dominating force throughout the winter months. Its development also underscores how sharply the upcoming winter promises to deviate from the outcome last winter which featured a moderate El Nino, a vigorous and very moist southern branch of the jet stream and a season that I will now referred to as "the great inversion of 2009-2010" for its tendency to provide snow and cold to our friends down south and agony due to the lack of snow in Vermont. Preseason forecasts may be mostly famous for vagueness (I confess to share the guilt on this) but I can stress, even in mid November that the upcoming winter will be a striking contrast to the last and will quickly display a very different personality. If nothing else, it will keep the prognosticators on our toes, since frequent updates will be required to what should be a rapidly changing and volatile weather pattern. It will prove to be fun and challenging if nothing else.
La Nina's return
The ENSO conversation is typically the easiest part of the preseason discussion. Its associations and relationships are known and a ENSO event is easily quantifiable. This years La Nina has already received a ton of discussion and for good reason. As an aggregate measure, the current La Nina in September-October (-1.59 SST anomaly)is the strongest since 1955. I was somewhat surprised that we didn't blow right through the tropical storm alphabet since La Nina's of such ferocity usually are associated with very active hurricane seasons (this year's actually was but we did not see any major land falling storms in the U.S. and we didn't blow through the alphabet, at least not yet). Two other La Nina event that comes close developed in 1988 a winter we would just assume forget and 2007 a winter where I was pleasantly surprised. The winter of 1970-71 also featured a strong La Nina (although one that developed very late) and this winter turned out like a dream with incredible snowfall amounts across northern Vermont. This may seem like a pointless range of possibilities to discuss (since the range includes seemingly everything) but La Nina winters have a distinct personality that ties them together as opposed to specific snowfall amounts. Two features that seem most persistent and most influential tend to be a large and potent ridge across the Gulf of Alaska and a persistent ridge across the southeastern United States. This often dreaded southeast ridge can make winter's non-existent in our southern mid-latitudes below 38-40 north. Ski areas that received the high snowfall amounts last year like Seven Springs in PA or Snowshoe in West Virginia will not be so lucky this year. It is a different ball game up north however. Storm systems, and many of them, get deflected up through the Ohio or Mississippi Valleys toward the eastern Great Lakes and then often proceed to split New England into pieces in terms of the weather that results including heavy snow across northern areas, ice, ice and more ice across southern interior areas and rain along the coasts. This line of rain to ice to snow is by no means a constant and tends to fluctuate from north to south based on the storm track or readily available fresh supply of cold air. During some winters, MRG is on the favorable side of all the uncertainty (70-71), some they are not and most fall in between. This means some weeks turn out very snowy but there are several where ice and rain can greatly damage our skiing enjoyment. It is often unfortunate because there is not much even a little elevation can do to stop surges of mid-level warmth that often become so prevalent during these type of winters. Latitude does greatly help however and we do have that working for us (44 north thank you very much !!
2007-2008 winter forecast got suffocated much to our delight !!
The discussion about the current La Nina should also include a look at the 2007-2008 winter. That season was predicted to be a poor one since it was thought that the La Nina strength combined with the slow autumn buildup of northern hemisphere snow cover would be tough to overcome. That forecast was terrible but in retrospect revealing. For one, it is another in an invariable string of reminders of how inaccurate these forecasts can be. Secondly, it did provide a bit of inspiration for some preseason research. The results are interesting in a study that involved looking at strong ENSO events (strong La Nina's or strong El Nino's) and snowfall and temperatures across northern New England. The temperature results are not surprising. The strong El Nino events are dominated by milder temperatures and strong La Nina events feature above normal temperatures of a lesser degree. Snowfall in winters featuring significant ENSO events was a bit suprising. Both strong La Nina's and El Nino's featured above normal snow which to some might seem like a counter-intuituve result. It would be healthy to maintain a bit of cynicism regarding the results since the sample size which spanned 60 years and 21 qualifying winters is rather small. Still it is fair to suggest that the winter forecast made in 2007-2008 was a bit too pessimistic. The premises were right and many of those premises will remain this year.
The build up of snow and a further look at other strong La Nina winters
Looking at the buildup of snow across the northern hemisphere is our empirical method for assessing the hypothetical magnitude of cold airmasses through the upcoming winter. It is very inexact and can change over the course of the season. Snow cover area however often proves to be an important thermal feedback especially when trying to predict the sign of temperature. It helps cold air pool more efficiently especially early in the season when large expanses of high latitude land can either be covered in snow or snowless. The 10 most recent strong La Nina winters featured the following coverage of snow (in millions of square km) across the northern hemisphere during October and November. The end result of each winter is included on the right.
Year Snow Result
1970-71 28.6 Very cold, much above normal snow
1973-74 27.6 Slightly mild and above normal snow
1975-76 23.8 Slightly cold and above normal snow
1984-85 25.4 Slightly cold and above normal snow
1988-89 22.1 Slightly mild, way below normal snow
1998-99 26.6 Very mild, normal snow
1999-00 25.5 Very mild, below normal snow
2007-08 24.4 Mild, much above normal snow
2010-11 ~25.3 ??
The average snow cover area for the northern hemisphere during this period is 25.3. The period ending this November 30th will come in just at or slightly over that number. It is interesting that that the year with the highest autumn snow cover turned out to be the best and the year with the lowest (1988) turned into the worst as far as skiing goes. Somewhat circumstantial perhaps but probably not entirely so. This winter has seen a healthy buildup of snow and a rapid expansion in the last week or two across the North America but its not much better than average over a two month period so therefore difficult to draw any conclusions.
Our friend the PDO
The Pacific Decadal Oscillation (PDO) is another variable we have factored in to the preseason forecasts. The PDO refers to the configuration of temperatures across the mid-lattitude Pacific Ocean as opposed to the ENSO which refers to the equatorial Pacific. A positive or warm phase is often but not always teamed up with an El Nino and tends to feature a long-wave or jet stream pattern consisting of a trough in eastern North America and a ridge in western North America. A negative phase of the PDO is often prevalent during a La Nina and has the opposite effect. Data in recent years suggests that we have moved into a prevailing negative PNA and that last years strong El Nino was tag teamed with a very weak positive PDO. This year the PDO has swung back to negative and it appears it will remain there through the winter. This comes as no surprise and supports a pattern we are already expecting given the strength of the current La Nina.
The Quasi-Biennial Oscillation
Just like with the PDO, 10 years ago, there has been work and increased discussion over the last several years regarding the Quasi-Biennial Oscillation and its relationship to the behavior of weather patterns in the northern hemisphere winter. I hope to keep most of the in-season discussions focused on more benign terminology but I did learn enough from emails and other discussions to provide a brief blurb. The QBO refers to the oscillation of the equatorial zonal wind in the stratosphere and is measured as an westerly or easterly index with westerly having a positive index and easterly negative. Some work has been done to establish a relationship between the phase of the QBO and Sudden Stratospheric Warming Events (another lengthy term). The SSWE have their own lengthy description and definition but they are associated with mid latitude jet stream blocks that are often the cause of sustained periods of cold weather. The easterly phase of the QBO for instance last year was said to encourage the persistent negative NAO. It has since moved to westerly perhaps suggesting less frequent negative NAO events and a more zonal pattern. None of this really contradicts anything that we might expect in a strong La Nina year such as this.
A summary and a prediction
So in summary, La Nina will win the day and win it decisively. It will mean that temperatures will average above normal but not as much as they did last winter - lets call it 1-2 degrees above for the ski season. Many places south of 40 degrees north latitude will experience a winter dramatically milder than last and dramatically less snow. We will get outbreaks of some severe cold but they will be interrupted and very abruptly by intrusions of milder weather. The milder weather will in many cases be accompanied by rain or ice which will at times be damaging. On the flip side there will be many other storm systems that bring snow and we should see a few epic periods. The southern branch of the jet stream will not be as influential and we will instead see a consolidated west to east jet stream send storm systems in our direction and few should miss. This should be enough to allow snowfall to come in above average - lets say 290 inches. This is around 110 percent of average at the mountain. The winter will require our full attention since many of the best periods will be simply wet or icy along the coast and conditions will change very quickly. Enjoy the thanksgiving holiday and think snow.
The emails I have gotten, which can now be sent to josh.aaron.fox@gmail.com (as opposed to yahoo) suggest that the SCWB reader continues is getting more and more weather literate asking the tough questions months ahead of the time when they usually get answered. We have an impressive audience of "in the closet" and "out of the closet" weather geeks and this helps to make running the SCWB a lot more fun. The talk this year has mostly revolved around La Nina and rightly so. It has blossomed quickly, decisively and promises to be a dominating force throughout the winter months. Its development also underscores how sharply the upcoming winter promises to deviate from the outcome last winter which featured a moderate El Nino, a vigorous and very moist southern branch of the jet stream and a season that I will now referred to as "the great inversion of 2009-2010" for its tendency to provide snow and cold to our friends down south and agony due to the lack of snow in Vermont. Preseason forecasts may be mostly famous for vagueness (I confess to share the guilt on this) but I can stress, even in mid November that the upcoming winter will be a striking contrast to the last and will quickly display a very different personality. If nothing else, it will keep the prognosticators on our toes, since frequent updates will be required to what should be a rapidly changing and volatile weather pattern. It will prove to be fun and challenging if nothing else.
La Nina's return
The ENSO conversation is typically the easiest part of the preseason discussion. Its associations and relationships are known and a ENSO event is easily quantifiable. This years La Nina has already received a ton of discussion and for good reason. As an aggregate measure, the current La Nina in September-October (-1.59 SST anomaly)is the strongest since 1955. I was somewhat surprised that we didn't blow right through the tropical storm alphabet since La Nina's of such ferocity usually are associated with very active hurricane seasons (this year's actually was but we did not see any major land falling storms in the U.S. and we didn't blow through the alphabet, at least not yet). Two other La Nina event that comes close developed in 1988 a winter we would just assume forget and 2007 a winter where I was pleasantly surprised. The winter of 1970-71 also featured a strong La Nina (although one that developed very late) and this winter turned out like a dream with incredible snowfall amounts across northern Vermont. This may seem like a pointless range of possibilities to discuss (since the range includes seemingly everything) but La Nina winters have a distinct personality that ties them together as opposed to specific snowfall amounts. Two features that seem most persistent and most influential tend to be a large and potent ridge across the Gulf of Alaska and a persistent ridge across the southeastern United States. This often dreaded southeast ridge can make winter's non-existent in our southern mid-latitudes below 38-40 north. Ski areas that received the high snowfall amounts last year like Seven Springs in PA or Snowshoe in West Virginia will not be so lucky this year. It is a different ball game up north however. Storm systems, and many of them, get deflected up through the Ohio or Mississippi Valleys toward the eastern Great Lakes and then often proceed to split New England into pieces in terms of the weather that results including heavy snow across northern areas, ice, ice and more ice across southern interior areas and rain along the coasts. This line of rain to ice to snow is by no means a constant and tends to fluctuate from north to south based on the storm track or readily available fresh supply of cold air. During some winters, MRG is on the favorable side of all the uncertainty (70-71), some they are not and most fall in between. This means some weeks turn out very snowy but there are several where ice and rain can greatly damage our skiing enjoyment. It is often unfortunate because there is not much even a little elevation can do to stop surges of mid-level warmth that often become so prevalent during these type of winters. Latitude does greatly help however and we do have that working for us (44 north thank you very much !!
2007-2008 winter forecast got suffocated much to our delight !!
The discussion about the current La Nina should also include a look at the 2007-2008 winter. That season was predicted to be a poor one since it was thought that the La Nina strength combined with the slow autumn buildup of northern hemisphere snow cover would be tough to overcome. That forecast was terrible but in retrospect revealing. For one, it is another in an invariable string of reminders of how inaccurate these forecasts can be. Secondly, it did provide a bit of inspiration for some preseason research. The results are interesting in a study that involved looking at strong ENSO events (strong La Nina's or strong El Nino's) and snowfall and temperatures across northern New England. The temperature results are not surprising. The strong El Nino events are dominated by milder temperatures and strong La Nina events feature above normal temperatures of a lesser degree. Snowfall in winters featuring significant ENSO events was a bit suprising. Both strong La Nina's and El Nino's featured above normal snow which to some might seem like a counter-intuituve result. It would be healthy to maintain a bit of cynicism regarding the results since the sample size which spanned 60 years and 21 qualifying winters is rather small. Still it is fair to suggest that the winter forecast made in 2007-2008 was a bit too pessimistic. The premises were right and many of those premises will remain this year.
The build up of snow and a further look at other strong La Nina winters
Looking at the buildup of snow across the northern hemisphere is our empirical method for assessing the hypothetical magnitude of cold airmasses through the upcoming winter. It is very inexact and can change over the course of the season. Snow cover area however often proves to be an important thermal feedback especially when trying to predict the sign of temperature. It helps cold air pool more efficiently especially early in the season when large expanses of high latitude land can either be covered in snow or snowless. The 10 most recent strong La Nina winters featured the following coverage of snow (in millions of square km) across the northern hemisphere during October and November. The end result of each winter is included on the right.
Year Snow Result
1970-71 28.6 Very cold, much above normal snow
1973-74 27.6 Slightly mild and above normal snow
1975-76 23.8 Slightly cold and above normal snow
1984-85 25.4 Slightly cold and above normal snow
1988-89 22.1 Slightly mild, way below normal snow
1998-99 26.6 Very mild, normal snow
1999-00 25.5 Very mild, below normal snow
2007-08 24.4 Mild, much above normal snow
2010-11 ~25.3 ??
The average snow cover area for the northern hemisphere during this period is 25.3. The period ending this November 30th will come in just at or slightly over that number. It is interesting that that the year with the highest autumn snow cover turned out to be the best and the year with the lowest (1988) turned into the worst as far as skiing goes. Somewhat circumstantial perhaps but probably not entirely so. This winter has seen a healthy buildup of snow and a rapid expansion in the last week or two across the North America but its not much better than average over a two month period so therefore difficult to draw any conclusions.
Our friend the PDO
The Pacific Decadal Oscillation (PDO) is another variable we have factored in to the preseason forecasts. The PDO refers to the configuration of temperatures across the mid-lattitude Pacific Ocean as opposed to the ENSO which refers to the equatorial Pacific. A positive or warm phase is often but not always teamed up with an El Nino and tends to feature a long-wave or jet stream pattern consisting of a trough in eastern North America and a ridge in western North America. A negative phase of the PDO is often prevalent during a La Nina and has the opposite effect. Data in recent years suggests that we have moved into a prevailing negative PNA and that last years strong El Nino was tag teamed with a very weak positive PDO. This year the PDO has swung back to negative and it appears it will remain there through the winter. This comes as no surprise and supports a pattern we are already expecting given the strength of the current La Nina.
The Quasi-Biennial Oscillation
Just like with the PDO, 10 years ago, there has been work and increased discussion over the last several years regarding the Quasi-Biennial Oscillation and its relationship to the behavior of weather patterns in the northern hemisphere winter. I hope to keep most of the in-season discussions focused on more benign terminology but I did learn enough from emails and other discussions to provide a brief blurb. The QBO refers to the oscillation of the equatorial zonal wind in the stratosphere and is measured as an westerly or easterly index with westerly having a positive index and easterly negative. Some work has been done to establish a relationship between the phase of the QBO and Sudden Stratospheric Warming Events (another lengthy term). The SSWE have their own lengthy description and definition but they are associated with mid latitude jet stream blocks that are often the cause of sustained periods of cold weather. The easterly phase of the QBO for instance last year was said to encourage the persistent negative NAO. It has since moved to westerly perhaps suggesting less frequent negative NAO events and a more zonal pattern. None of this really contradicts anything that we might expect in a strong La Nina year such as this.
A summary and a prediction
So in summary, La Nina will win the day and win it decisively. It will mean that temperatures will average above normal but not as much as they did last winter - lets call it 1-2 degrees above for the ski season. Many places south of 40 degrees north latitude will experience a winter dramatically milder than last and dramatically less snow. We will get outbreaks of some severe cold but they will be interrupted and very abruptly by intrusions of milder weather. The milder weather will in many cases be accompanied by rain or ice which will at times be damaging. On the flip side there will be many other storm systems that bring snow and we should see a few epic periods. The southern branch of the jet stream will not be as influential and we will instead see a consolidated west to east jet stream send storm systems in our direction and few should miss. This should be enough to allow snowfall to come in above average - lets say 290 inches. This is around 110 percent of average at the mountain. The winter will require our full attention since many of the best periods will be simply wet or icy along the coast and conditions will change very quickly. Enjoy the thanksgiving holiday and think snow.
Sunday, April 4, 2010
Warm weather ends an uneven season
Uneven would be a generous way of putting it, disappointing might be the blunt way. There were some high expectations going into the year as it appeared we would have the right mix of high octane jet energy in the south and cold weather from the north to produce some big things. In fact, that is exactly what we saw, but all the fun was well to Vermont's south. The snow would have been more welcomed in our neck of the woods since it caused unprecedented disruptions in air traffic and costly clean-up projects in our major U.S. cities.
It is funny to look at the compiled data and how it illustrates how 2007-2008 got turned upside down thanks largely to a flip in the ENSO from La Nina to El Nino. Take a look at how we left 2007-2008 at the SCWB.
"Montreal, Quebec - 142 inches (169 % of average)
Burlington, VT - 100 inches (131 % of average)
Boston, MA - 51 inches (113 % of average)
Philadelphia, PA - 6 inches (25 % of average)
In the language of anomalies that is quite a contrast. In other words, some pain and suffering had to be endured by skiers/riders who stayed at Seven Springs or Snowshoe WV this year. Lattitude was key at we had it at MRG and this proved to save our season."
Pain and suffering is not the word to describe the season at Seven Springs or Snowshoe this past winter. Both mountains received over 200 inches of snow which in the case of Seven Springs was a record. Most importantly, the conditions were epic for the first three weeks of February in all of those locations as record snow was combined with consistent cold.
At Mad River Glen, we did not have a winter as futile as 2005-2006 or 2001-2002. We were pleasantly surprised early in the season as several storms pronged to move well to our south took an 11th hour turn northward to yield some powder. The mountain missed the Megalopitan storm "I" but did get a multi-day powder fest on New Years as a storm retrograted westward out of the Gulf of Maine. This was arguably the best event of the season for the mountain and was meteorologically fascinating since the event caused Champlain induced powder to fall over Burlington to the tune of 3 feet.
There was much anticipation after a quiet end to January since the pattern in early February looked as stormy as any I have ever seen in winter. The pattern was fueled by a plethora of blocking mechanisms across the high latitudes and an extremely energetic southern branch of the jet stream. The blocking was so ferocious that the storm track was forced unusually far to our south. Interestingly, so was the cold weather. Florida was not the place to visit during the winter as frequent outbreaks of intense cold resulted in the coldest winter in over 30 years. At Mad River glen, the cold weather never reached a level we would consider "intense" and although the winter was free of large scale "thaws" temperatures averaged above normal for the season. It was an unusual combination of circumstances to say the least but one that caused back to back major storms across the Mid-Atlantic States in early February. The seasonal snowfalls in cities like Baltimore, MD and Philadelphia climbed to 400 % of normal but much of Vermont continued to be plagued with a snow drought. Not only did MRG miss both Megalopitan events in February, but terrain induced events were non-existent as northern branch jet energy was locked up across Canada and southern branch energy was causing unprecedented snow farther south.
The big event of the winter at MRG occurred late in February. It was a very convoluted system flush with moisture but initially disorganized and ultimately quite mighty but very occluded. The initial burst of snow resulted in a swath of 50 inch totals up the spine of the Berkshires and Green Mountains but as the storm matured, it brought a conveyor of warmth into interior New England while cold advanced east into areas like Maryland, Pennsylvania and New Jersey. There were several hours during this event where you could've driven south on the New York State Thruway and the weather would have transitioned from heavy rain to heavy snow. In many ways it underscored the personality of the entire winter as an imaginary line within a few degrees of 40 north seemed to divide areas that received record snow from areas that consistently seemed to receive little snow. The storm in late February was a great one for MRG and would have been epic were it not for that warm intrusion which made conditions very changeable as you moved down the mountain.
In the end an El Nino of moderate strength such as the one that was present for much of the season, combined with the consistent presence of mid latitude cold are certainly the ingredients necessary for a winter such as the one we received. My conventional wisdom was perhaps wish casting for a winter more similar to 1992-1993 or 1977-1978 but the winter turned out to be a more exaggerated version of 1986-1987 or 1987-1988. The year perhaps most similar was 1957-1958. In that winter, record snow hit portions of Maryland and Pennsylvania late in the season in another year where the El Nino was very prevalent.
On a more personal note, I once again enjoyed the opportunity to talk weather to the greatest weather audience perhaps in the world. I felt the quality of the blog perhaps suffered at times since at times I found it challenging to combine my work load with blogging responsibilities. To make a long story short, it was easier to maintain the blog when you are unemployed and in search of things to do. I got a lot of emails, mostly positive and many I never got a chance to respond to. I appreciate the comments even if I never got a chance to craft a response. Enjoy the summer, stay safe think big snow for next winter.
-Josh Fox of the SCWB
It is funny to look at the compiled data and how it illustrates how 2007-2008 got turned upside down thanks largely to a flip in the ENSO from La Nina to El Nino. Take a look at how we left 2007-2008 at the SCWB.
"Montreal, Quebec - 142 inches (169 % of average)
Burlington, VT - 100 inches (131 % of average)
Boston, MA - 51 inches (113 % of average)
Philadelphia, PA - 6 inches (25 % of average)
In the language of anomalies that is quite a contrast. In other words, some pain and suffering had to be endured by skiers/riders who stayed at Seven Springs or Snowshoe WV this year. Lattitude was key at we had it at MRG and this proved to save our season."
Pain and suffering is not the word to describe the season at Seven Springs or Snowshoe this past winter. Both mountains received over 200 inches of snow which in the case of Seven Springs was a record. Most importantly, the conditions were epic for the first three weeks of February in all of those locations as record snow was combined with consistent cold.
At Mad River Glen, we did not have a winter as futile as 2005-2006 or 2001-2002. We were pleasantly surprised early in the season as several storms pronged to move well to our south took an 11th hour turn northward to yield some powder. The mountain missed the Megalopitan storm "I" but did get a multi-day powder fest on New Years as a storm retrograted westward out of the Gulf of Maine. This was arguably the best event of the season for the mountain and was meteorologically fascinating since the event caused Champlain induced powder to fall over Burlington to the tune of 3 feet.
There was much anticipation after a quiet end to January since the pattern in early February looked as stormy as any I have ever seen in winter. The pattern was fueled by a plethora of blocking mechanisms across the high latitudes and an extremely energetic southern branch of the jet stream. The blocking was so ferocious that the storm track was forced unusually far to our south. Interestingly, so was the cold weather. Florida was not the place to visit during the winter as frequent outbreaks of intense cold resulted in the coldest winter in over 30 years. At Mad River glen, the cold weather never reached a level we would consider "intense" and although the winter was free of large scale "thaws" temperatures averaged above normal for the season. It was an unusual combination of circumstances to say the least but one that caused back to back major storms across the Mid-Atlantic States in early February. The seasonal snowfalls in cities like Baltimore, MD and Philadelphia climbed to 400 % of normal but much of Vermont continued to be plagued with a snow drought. Not only did MRG miss both Megalopitan events in February, but terrain induced events were non-existent as northern branch jet energy was locked up across Canada and southern branch energy was causing unprecedented snow farther south.
The big event of the winter at MRG occurred late in February. It was a very convoluted system flush with moisture but initially disorganized and ultimately quite mighty but very occluded. The initial burst of snow resulted in a swath of 50 inch totals up the spine of the Berkshires and Green Mountains but as the storm matured, it brought a conveyor of warmth into interior New England while cold advanced east into areas like Maryland, Pennsylvania and New Jersey. There were several hours during this event where you could've driven south on the New York State Thruway and the weather would have transitioned from heavy rain to heavy snow. In many ways it underscored the personality of the entire winter as an imaginary line within a few degrees of 40 north seemed to divide areas that received record snow from areas that consistently seemed to receive little snow. The storm in late February was a great one for MRG and would have been epic were it not for that warm intrusion which made conditions very changeable as you moved down the mountain.
In the end an El Nino of moderate strength such as the one that was present for much of the season, combined with the consistent presence of mid latitude cold are certainly the ingredients necessary for a winter such as the one we received. My conventional wisdom was perhaps wish casting for a winter more similar to 1992-1993 or 1977-1978 but the winter turned out to be a more exaggerated version of 1986-1987 or 1987-1988. The year perhaps most similar was 1957-1958. In that winter, record snow hit portions of Maryland and Pennsylvania late in the season in another year where the El Nino was very prevalent.
On a more personal note, I once again enjoyed the opportunity to talk weather to the greatest weather audience perhaps in the world. I felt the quality of the blog perhaps suffered at times since at times I found it challenging to combine my work load with blogging responsibilities. To make a long story short, it was easier to maintain the blog when you are unemployed and in search of things to do. I got a lot of emails, mostly positive and many I never got a chance to respond to. I appreciate the comments even if I never got a chance to craft a response. Enjoy the summer, stay safe think big snow for next winter.
-Josh Fox of the SCWB
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