Northeast region reeling from erratic weather 


Staff Writers

Published: 08-07-2023 12:12 PM

NORTHAMPTON — In a town reporting $2.2 million in road damage last month, the “fun fact” tweeted out recently by the National Weather Service in Boston might come as no surprise: The highest July rainfall total in the U.S., Canada and Puerto Rico was in Conway, Massachusetts, with 21.42 inches.

Not far behind, and also in the top 5, was Northampton, with 18.93 inches.

The data come from the Community Collaborative Rain, Hail and Snow Network — CoCoRaHS for short — a group of volunteers who measure and report precipitation. The reported totals can vary quite widely within a small area, but the organization’s map shows a foot of rain or more falling last month in a 15-mile swath west of the Connecticut River, from Colrain in the north to Westfield in the south.

Much of the Northeast was drenched in July, with several major weather stations reporting record or near-record rainfall.

Hartford, Conn., and Albany, N.Y., along with Barre, Vt., and Berlin, N.H., saw the most July rain ever, while Boston, Worcester and Providence, R.I., had their second-wettest July on record, according to Cornell University’s Northeast Regional Climate Center.

July 2021 also passed into the record books as the wettest July on record in Massachusetts up to that point, followed by a severe drought in 2022, then this year’s weekly deluges.

While scientists typically look at historical averages over long period of times to examine a changing climate, these extreme shifts in weather variability each year may be a signal of climate change that the average person may observe, according to Jennifer Francis, a senior scientist at the Woodwell Climate Research Center in Falmouth.

“Climate scientists have long expected to see increased weather swings associated with a warming globe,” Francis wrote in an email. “Hot/dry spells are now hotter and drier, wet spells are bringing heavier downpours, and weather regimes of all sorts are expected to become more persistent.”

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“Weather whiplash,” as Francis calls it, is the abrupt change in the weather after a long spell of stability and seems to be increasingly common on a weekly, monthly or yearly scale. Day-to-day variability, however, has “generally decreased over time.”

Michael Rawlins, associate director of the Climate System Research Center at the University of Massachusetts Amherst, cautioned that a four-year stretch of extreme swings in precipitation are a weather trend, while climate trends are based on decades of data.

“Around the globe, this summer and in recent years, we’ve seen extreme precipitation events consistent with a warming climate,” Rawlins said. “Is that a trend that will continue? Time will tell.”

A variety of factors can play in the variable weather seen year to year and Francis said a key aspect is the shifting of jet streams, which are the narrow bands of strong wind blowing west to east 30,000 feet up in the atmosphere. Other factors include abnormally warm ocean temperatures, early loss of spring snow and ice melt in the Arctic, among others.

Francis explained the jet stream shifts, or “meanders,” north and south as it travels around the Earth, which create the highs and lows seen on TV weather maps, and that weather patterns are typically sticking around longer due to the effect humans are having on the winds.

“Human-caused climate change is expected to make the jet stream take wide meanders more often, which causes weather systems to move more slowly and lead to long-duration weather conditions,” Francis said.

Rawlins, emphasizing his expertise is on climate, not weather variability, said dramatic swings between “wet and dry are consistent with an intensification of the hydrological cycle,” the process of how precipitation is circulated around the planet.

“An intensification of the hydrological cycle is most certainly simulated in models and that’s what we’re experiencing,” Rawlins said. “Wet areas of the globe are projected to get wetter and dry areas are predicted to get drier.”

As for August? Keep the umbrella handy as the National Oceanic and Atmospheric Administration’s monthly outlook is projecting an above-normal amount of rain.