ADDISON COUNTY — Rain, snow, sleet, freezing rain and even some hail pummeled Addison County residents this past year.
“We had a lot of extremes, mostly in precipitation,” said Nathan Foster, the observing program leader for the National Weather Service’s (NWS) Burlington office. “It was one of our wettest years on record for Vermont.”
Looking back over the past 12 months, there were certainly instances of extreme precipitation. Last January and February Addison County was slammed with snow; NWS monitors in Cornwall, Salisbury and South Lincoln measured an average of 66 inches of snow in those two months.
The single wettest day of 2011 came on Aug. 29, when Tropical Storm Irene hit. In that one day, 2.88 inches of rain fell in Cornwall, 4.08 fell in Salisbury, and 5.36 fell in South Lincoln, according to NWS data.
2011 was the wettest year on record for Salisbury, with 54.87 inches of precipitation, and the third wettest year on record for Cornwall and South Lincoln, where precipitation totals were 46.8 and 58.53 inches, respectively.
Irene, for sure, was the biggest weather story of the year. The tropical storm caused the most flooding in Vermont since at least 1927. Numerous bridges and roads in Addison County were washed out, and 2,500 area power customers lost electricity. The damages caused by the flooding were the most expensive in Vermont history.
Although the effects of the increased precipitation are clear, singling out exactly one cause for the unusually high levels of precipitation proves challenging.
“We had a very active jet stream, which means more storm systems coming through the region,” said Foster. “This was especially true early in the year with all our snowfall. We did have ‘La Nina’ conditions, or cooler than normal temperatures off equatorial South America. This could have contributed. Overall though, years vary from one extreme to another so pinpointing one particular cause would be difficult.”
Irene played a role in altering the amount of precipitation, simply because of the storm’s magnitude.
“Irene accounted for some of the above average precipitation amounts late in the summer and that didn’t have anything to do with the jet stream,” said Foster.
East Middlebury resident Charlie Hohn, who writes a weather blog on addisonindependent.com, also believes the exact cause of the increased precipitation is difficult to find, but he points to a long-growing trend.
“There actually is a really strong trend on record toward the weather getting wetter,” said Hohn. “The average (annual) precipitation has increased by an average of 7 inches over the last 100 years. This increase could be related to climate getting warmer, or other cyclical trends that happen naturally.”
Despite the extremely wet first 10 months of the year, 2011 closed out with about two months with minimal precipitation.
Rain and snowfall in the towns measured by the NWS was recorded as consistently lower than normal.
The long wait the area had for a substantial snowfall probably wasn’t due to the temperature, but rather to moisture levels.
“We’ve gotten our cold spells; they just haven’t been when there’s been moisture in the air,” said Hohn. “We’ve never had more than two or three inches of snow at a time.”
The lack of precipitation in the past two months is probably connected to the jet stream.
“It’s just been drier in general,” said Hohn. “Right now this is the pattern we’re in. It’s connected to shifts in the jet stream.”
In addition, Addison County hasn’t experienced the frigid temperatures that usually come with a dry winter.
“Most dry winters are really cold winters, but this one has been warmer than ever,” said Hohn. “For whatever reason, something changed in the jet stream.”
Temperatures overall in Addison County were fairly close to normal levels. However, in the last four months of 2011 temperatures were above normal averages.
The hottest day of the year came on July 22, when temperatures in Salisbury reached 98 degrees F, and hit 96 and 91 degrees in Cornwall and South Lincoln, respectively. 2011 was the second warmest year on record for South Lincoln, and the fifth warmest for Salisbury.
The coldest day in Addison County in 2011 was last Jan. 24. In Cornwall thermometers bottomed out at –23 degrees, in Salisbury –24, and in South Lincoln –18 degrees.
Overall, the most remarkable aspect of 2011’s weather was the unusually high precipitation. While a large portion of it can be chalked up to Irene, levels still were higher than the norm.
“It’s definitely been an unusual year all across the country,” said Hohn. “It’ll be interesting to see what the next few years bring.”
CORRECTION 1/19/12: “Gulf Stream” originally appeared in the text of this article; it should have read “Jet Stream.”