FILE PHOTO JEB WALLACE-BRODEUR
Most of us will also remember January 2009 for its bone-chilling temperatures, which set new records across the state and forced many of us to jump-start our cars on some of the coldest mornings. New record-low temperatures were set at St. Johnsbury (-30) and Burlington (-21) on Jan. 16, and at Rutland (-20) the next day.
Statewide, the average monthly temperature was 11.1 degrees – the 21st coldest January since 1895. Many of Lake Champlain’s bays froze over (and remained so until the first week of March), with ice fishing enthusiasts reporting some of the thickest ice seen in years.
Winter weather was wild
By LESLEY-ANN DUPIGNY-GIROUX and LAURA KIESEL
The 2008-2009 winter across Vermont and much of the North Country was wild, marked by temperature swings, lots of precipitation and even a rare weather phenomenon on Lake Champlain.
In December the most dramatic event was the ice storm that moved through the region on Dec. 11-12. This storm played havoc with air travel in southern New England and left millions without electricity. Unlike the infamous ice storm of January 1998, which began as a rain event that changed over to freezing rain from north to south, the ice storm this winter was much more complex. It began as snow across much of northern Vermont and surroundings, changed over to freezing rain in the southern parts of the state, and continued as snow to the north.
Snowfall totals were heaviest on either side of the Green Mountains. The National Weather Service in Burlington reported 0.25 to 0.5 inches of ice accumulation in Rutland and Windsor counties, while Bennington and Windham counties saw higher amounts. This pattern reflected the northeast-southwest orientation of a cold front that stalled off the New England coast during the evening of Dec. 10. Along the frontal boundary, cold air from southern Québec met with warm, moist air from the south. By the following evening, the stalled front started moving northwestward back toward New England, this time as a warm front.
December 2008 was also marked by the passage of several other frontal systems that brought the total statewide precipitation to 4.77 inches. This number represents what is called the “liquid water equivalent,” or the sum of what the snowfall would amount to if it fell as rain, plus the actual rain that also fell. This 4.77-inch total was 149 percent of the average December precipitation, making 2008 the 13th wettest December since 1895. Most of this precipitation fell in western Vermont.
January 2009 saw more flip-flops, both in terms of temperature, as well as in the amount of precipitation around the state. Compared to the abundance of December, Vermont as a state only received 50 percent (1.57 inches) of its average in January, making it the 16th driest January since 1895. These dry conditions were most prevalent in the northeastern and southeastern portions of the state, while western Vermont (including the Champlain Valley) actually received about 3.14 inches or 128 percent of average. The apparent dichotomy illustrates why climatologists seldom use averages alone, as they can hide important patterns.
Most of us will also remember January 2009 for its bone-chilling temperatures, which set new records across the state and forced many of us to jump-start our cars on some of the coldest mornings. New record-low temperatures were set at St. Johnsbury (-30) and Burlington (-21) on Jan. 16, and at Rutland (-20) the next day. These records capped off a week of cold, dry weather that persisted as an arctic front moved eastward across the North Country and caused temperatures across the region to plunge by 30 to 40 degrees. In fact, this cold snap was so severe that some ski resorts either closed early or restricted slopes, and most of them posted frostbite warnings. Statewide, the average monthly temperature was 11.1 degrees – the 21st coldest January since 1895. Many of Lake Champlain’s bays froze over (and remained so until the first week of March), with ice fishing enthusiasts reporting some of the thickest ice seen in years.
Why these temperature swings? One clue lies to the west, the other to our east. Most of our weather originates to our west – the numerous fronts that move through, as well as the high pressure patterns associated with clear skies but frigid conditions. The January cold snap was marked by an unusually strong and very extensive high pressure system that formed over the central states and expanded to encompass the entire eastern half of North America.
How did this extraordinarily high pressure – with its frigid, dense air – develop and persist? The second clue, to our east, is known as the North Atlantic Oscillation. When the North Atlantic Oscillation is in its positive phase (characterized by the presence of a low-pressure system near Iceland and a high pressure system further south near Gibraltar), temperatures across the eastern part of North America are moderate. However, when the system near Iceland is dominated by high pressure and that near Gibraltar by low pressure, we experience the negative phase of the North Atlantic Oscillation. In this case, cold Arctic air invades eastern North America and Europe, as we saw here in January.
On a somewhat different note, Jan. 15 also marked the rare occurrence of a waterspout in Lake Champlain, the second one on record since 1954. A waterspout is a micro-scale tornado resembling a funnel-shaped cloud that stays concentrated over a body of water and causes the water to shoot upwards. The lake temperature that morning was 33, and the air temperature over the southern portion of the lake was zero. This large difference in temperature between the air and water below it contributed to the formation of steam (evaporation) fog. This and the resulting updraft likely caused the waterspout to form.
After the excitement of December and January, February was quieter. Statewide, 2.26 inches of precipitation fell – 97 percent of the average for that month.
One of the month’s highlights was the blizzard of Feb. 22-23. The heaviest snowfall was recorded in an east-west band across the northern part of the state from Eden (13 inches) to East Haven (16 inches) and Island Pond (12 inches) in the Northeast Kingdom. The town of Sutton was at the center of this swath of snow, where 20.6 inches fell on that day alone. For Chelsea, Corinth, East Haven, Eden, and Sutton, these 24-hour snowfall amounts set new daily records that were only superseded as a monthly record by the Valentine’s Day blizzard of 2007.
Are we out of the woods? March is a time of transition. The air masses and storm systems are beginning to shift from winter-like patterns to those that will dominate the summer. Expect the unexpected!
Lesley-Ann Dupigny-Giroux is an associate professor at UVM and the Vermont state climatologist. She can be contacted at state.climatologist @uvm.edu. Laura Kiesel is a graduate student at UVM who works as a research assistant in the Vermont State Climate Office.
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