Adam Adkins
EF3
Here are my basic thoughts along with a lot of background for those unfamiliar with winter weather. I am focusing these thoughts on the Denver/Colorado area because that is where I have spent most my time of study, but the overall ideas presented at the end apply to the nation as a whole. Any help from others or ideas and opinions are greatly appreciated!
The probability of Denver getting a big blizzard during the snowy season is elevated or lowered depending on global circulation patterns. Such patterns include MJO (the Madden Julian Oscillation, small effect), PDO (the Pacific Decadal Oscillation, moderate effect), and ENSO (El Nino Southern Oscillation, large effect). We'll leave MJO out of the discussion for now because of its smaller effect. These global circulation patterns all effect the strength and positioning of the Polar Jet Stream and the Subtropical Jet Stream. When Denver gets its big winter storms, the Subtropical Jet Stream is usually the bigger player.
To begin, PDO (the Pacific Decadal Oscillation) is a long-lived pattern of cooling or warming of the North Pacific ocean just west of North America. Apart from the significant effects on marine life, PDO effects the U.S. in similar ways to ENSO (below paragraph). A warm phase (positive) PDO will bring a wet winter to northern North American and the southern United States. A negative PDO will do the opposite. A positive PDO in itself enhances the risk of a major winter storm for eastern Colorado.
The El Nino Southern Oscillation (ENSO) is the large-scale warming or cooling of the waters of the equatorial Pacific Ocean, and has the largest effect on winter weather patterns. It can be in three phases: El Nino (warming), Neutral (normal), or La Nina (cooling). The warm El Nino phase increases thunderstorm activity over the ocean and periodically enhances the strength and moisture transport of the Subtropical Jet Stream (which brings Denver its big blizzards). La Nina does the opposite. With El Nino, amount of warming also effects climate, and a very strong El Nino can provide even more moisture transport and strength to the Southern Jet Stream on occasion. Therefore, El Nino (the stronger the better) enhances the risk of a big storm in Denver (as well as southern California), and La Nina does the opposite.
So where are we at this year? We are currently dealing with a warming, increasingly positive PDO. This enhances Denver's risk for a big snow. It is also continuing to elevate throughout the fall. In addition, we not only are entering into an El Nino phase, but we are entering into one of the strongest El Ninos on record! The combination of these two is alarming! Together, the positive PDO and strong El Nino dramatically increase our risk of "the big one".
It must be said that El Nino and a positive PDO to NOT mean it might snow more frequently - it mean that when it snows, it is more likely that it will be significant. The last El Nino of this strength was in 1997, and in October of that year Colorado had one of its worst blizzards on record, with southern sections of Denver receiving nearly 5' of snow and 60mph winds.
Because of the strength of the El Nino and the positive PDO, I predict a 90% chance that "the big one" will slam Denver this snowy season. It is possible there may be 2 or even 3 big blizzards, but there is a 90% likelihood of at least one. That is my winter prediction based on global circulation patterns and a century of data analysis.
However,
the only wildcard in the forecast is the recent years development of the winter Polar Vortex, which many scientists, including myself, think may be caused by the tremendous loss of arctic sea ice. The loss of ice causes the cold dome of air over the arctic to become unstable, and large chucks of arctic air can break off and swing across the lower latitudes (the Polar Vortex). Will the Polar Vortex re-emerge for a third year in a row? (If it does continue to re-emerge year after year, this breakup of arctic air will be the first MAJOR consistent worldwide weather effect of climate change.) And also if it does, could it combined with El Nino and PDO enhance the likelihood of a 100-year blizzard in Denver? How will the strong Subtropical Jet be impacted? These are all questions we don't know the answer to, but it will be a very informative and interesting snowy season to study in the grand scheme of climate change.
My overall prediction for the winter: It is likely Denver will get its blizzard. But in general we are heading into unknown territory with record strength ENSO, PDO, and climate change knocking heads this year. Expect the unprecedented.
The probability of Denver getting a big blizzard during the snowy season is elevated or lowered depending on global circulation patterns. Such patterns include MJO (the Madden Julian Oscillation, small effect), PDO (the Pacific Decadal Oscillation, moderate effect), and ENSO (El Nino Southern Oscillation, large effect). We'll leave MJO out of the discussion for now because of its smaller effect. These global circulation patterns all effect the strength and positioning of the Polar Jet Stream and the Subtropical Jet Stream. When Denver gets its big winter storms, the Subtropical Jet Stream is usually the bigger player.
To begin, PDO (the Pacific Decadal Oscillation) is a long-lived pattern of cooling or warming of the North Pacific ocean just west of North America. Apart from the significant effects on marine life, PDO effects the U.S. in similar ways to ENSO (below paragraph). A warm phase (positive) PDO will bring a wet winter to northern North American and the southern United States. A negative PDO will do the opposite. A positive PDO in itself enhances the risk of a major winter storm for eastern Colorado.
The El Nino Southern Oscillation (ENSO) is the large-scale warming or cooling of the waters of the equatorial Pacific Ocean, and has the largest effect on winter weather patterns. It can be in three phases: El Nino (warming), Neutral (normal), or La Nina (cooling). The warm El Nino phase increases thunderstorm activity over the ocean and periodically enhances the strength and moisture transport of the Subtropical Jet Stream (which brings Denver its big blizzards). La Nina does the opposite. With El Nino, amount of warming also effects climate, and a very strong El Nino can provide even more moisture transport and strength to the Southern Jet Stream on occasion. Therefore, El Nino (the stronger the better) enhances the risk of a big storm in Denver (as well as southern California), and La Nina does the opposite.
So where are we at this year? We are currently dealing with a warming, increasingly positive PDO. This enhances Denver's risk for a big snow. It is also continuing to elevate throughout the fall. In addition, we not only are entering into an El Nino phase, but we are entering into one of the strongest El Ninos on record! The combination of these two is alarming! Together, the positive PDO and strong El Nino dramatically increase our risk of "the big one".
It must be said that El Nino and a positive PDO to NOT mean it might snow more frequently - it mean that when it snows, it is more likely that it will be significant. The last El Nino of this strength was in 1997, and in October of that year Colorado had one of its worst blizzards on record, with southern sections of Denver receiving nearly 5' of snow and 60mph winds.
Because of the strength of the El Nino and the positive PDO, I predict a 90% chance that "the big one" will slam Denver this snowy season. It is possible there may be 2 or even 3 big blizzards, but there is a 90% likelihood of at least one. That is my winter prediction based on global circulation patterns and a century of data analysis.
However,
the only wildcard in the forecast is the recent years development of the winter Polar Vortex, which many scientists, including myself, think may be caused by the tremendous loss of arctic sea ice. The loss of ice causes the cold dome of air over the arctic to become unstable, and large chucks of arctic air can break off and swing across the lower latitudes (the Polar Vortex). Will the Polar Vortex re-emerge for a third year in a row? (If it does continue to re-emerge year after year, this breakup of arctic air will be the first MAJOR consistent worldwide weather effect of climate change.) And also if it does, could it combined with El Nino and PDO enhance the likelihood of a 100-year blizzard in Denver? How will the strong Subtropical Jet be impacted? These are all questions we don't know the answer to, but it will be a very informative and interesting snowy season to study in the grand scheme of climate change.
My overall prediction for the winter: It is likely Denver will get its blizzard. But in general we are heading into unknown territory with record strength ENSO, PDO, and climate change knocking heads this year. Expect the unprecedented.
