ADDISON COUNTY — Those who sensed that the first five months of this year were wetter than normal were correct. Precipitation at the Burlington International Airport so far in 2011 is 24.4 inches — almost double the 12.41 inches in a typical year.
“Last year was close to normal,” said National Weather Service meteorologist Jessica Neiles. “We were 0.32 inches below normal. Now we’re 11.99 inches above normal.”
That 24.4 inches from Jan. 1 through May 31 set a record for precipitation in Burlington, and amounts measured around Addison County tracked with that figure. According to figures provided to the NWS by Addison County observers, during that same 151-day period the available local numbers for precipitation (rain, plus snow converted to the equivalent) are:
• South Lincoln: 25.11 inches.
• Salisbury: 23.68 inches.
• Cornwall: 20.02 inches.
• Middlebury: 18.44 inches.
The weather service has been tracking climate data in Vermont since 1850, Neiles said. The first five months of this year at the NWS station have been more than four inches wetter than the runner-up (20.21 inches in 1983) and more than six-and-a-half inches wetter than the bronze-medal winner (17.74 inches in 2000.)
“It’s been a pretty rare year,” Neiles said.
Through the end of March, the year 2011 was the third snowiest winter on record, but rainfall in April and especially May — more than 7 inches — pushed the precipitation numbers over the top, she said. And Neiles also noted that three of the five years with the wettest first 151 days have come since 2000 — 2000, 2006 and now 2011.
Normal is just an average, she said, that could be changed when new information is fed into the system.
“Normal is such a strange thing to think about it,” Neiles said. “It changes every 10 years when we get 10 years of new data. I guess there has to be a standard way to look at it.”
Although it rained steadily throughout May, Lake Champlain began flooding early in the month. On May 5 the Rouse’s Point, N.Y., gauge hit 103.20 feet above sea lever and the Burlington gauge read 103.27. Experts consider the lake to be at flood level when the gauges hit 100 feet.
Neiles said prevailing winds typically lead to higher readings on the eastern shore. On Tuesday, the Rouse’s Point gauge stood at 101.55 feet, and Burlington’s at 101.63, still more than a foot-and-a-half above flood stage. Several roads in Addison County near the lake are still closed, and lakefront property owners are dealing with any number of flood-related problems.
The readings were higher early in the month because of snowpack melt blending with rain, even though there was as much or more rain later in May, Neiles said.
“It was a combination of higher than normal snow depth that was still remaining, and a really rainy spring,” she said.
Still, despite its watery start, 2011 has a long way to go to hit the all-time record books.
In 1998, 50.42 inches of precipitation soaked the NWS station, edging 1983 (50.16) for the dubious distinction as the wettest year.
Rounding out the top — or bottom, depending on one’s point of view — five are 2006 (46.99 inches), 1973 (46.28) and 1955 (42.67).
In earlier interviews, NWS meteorologist Brooke Tabor said the region’s high snowfall total came from an unusually volatile jet stream, the always-blowing east-west airflow across North America. This winter, he said, it was fueled by a more-active-than-usual duel between cold polar air from the north, and warm, moister-than-typical sub-tropical air from the south. He described the ongoing clashes between the air masses as a “battle zone.”
This spring, the jet stream was still doing Vermont no favors. Not only were those air masses from the north and south still dueling — with the temperature contrast creating favorable conditions for rain — but the jet stream, which usually wanders in its course, was locked in place over Vermont, Tabor said, “steering these storm systems right across our region.”
The good news, Neiles said this week, is two-fold: For now, the rain has departed. The jet stream has returned to its more typically wandering ways, and summer weather — bringing what she called less dramatic and often “widespread rain events” — has finally arrived.
“I think that pattern has broken down,” she said.
Still, on Tuesday Neiles said the forecast “looks a little unsettled for the weekend,” with some rain possibly moving in on Saturday and lingering through Sunday.
For longer-range forecasting, meteorologists in Burlington rely on their colleagues at the NWS Climate Prediction Center, whose weather maps for the region look at two- and three-month forecasts. Neiles said the maps offer little of predictive value: They are covered in coded colors that indicate Vermont has equal chances for above-normal, normal and below-normal temperatures and rain this summer.
“They have equal chances for any of the three,” Neiles said. “It’s not really cluing us in very much what to expect yet.”
Andy Kirkaldy may be reached at email@example.com.