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La Niña and Local Weather Patterns: An Interview with Meteorologist Roger Hill

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Abnormally colder Pacific sea temperatures push the polar jet stream northward and create a low-pressure zone in the Pacific Northwest, resulting in heavier rainfall and colder temperatures in the north and drier, warmer conditions in the south. Image courtesy of the National Oceanic and Atmospheric Association.
By Eliana Moorhead

The week of the 2024 summer solstice was abnormally sweltering as the city of Burlington, Vermont, reached temperatures ten degrees higher than those in Miami, Florida. Heat indexes across Vermont climbed to 105°F, breaking record highs from the mid-1990s. According to the National Oceanic and Atmospheric Association (NOAA), normal highs for the week of June 17 in Montpelier are between 73°F and 76°F. Vermonters are living in the throes of the climate crisis, between flood recovery and extreme heat waves, and the effects are becoming increasingly harder to predict.

Roger Hill, a deeply experienced weather forecaster from Worcester, shared his insights for the summer of 2024 with The Bridge. This year marks Hill’s 50th in the field of meteorology. He worked with the National Weather Service for over a decade, has worked in stations in Los Angeles, Montana, and North Carolina, and has been a long-time forecaster for Radio Vermont. 

Hill’s summer weather predictions include warmer and wetter trends, with an increased risk of tropical storms in August and September due to La Niña, which, according to NOAA, is “characterized by unusually cold ocean temperatures in the Equatorial Pacific.”

“We’ve moved from an El Niño to a La Niña, which means cold sea surface temperatures are moving off of Ecuador and South America across the Pacific side,” Hill says.

In La Niña conditions, Hill explains, powerful tropical cyclones are not broken up as much. Colder water temperatures mean there is less vertical wind shear — less fluctuation in wind speed and direction with height — to bust through developing hurricanes. 

“The theory right now is that we’re going to see uninterrupted tropical cyclones coming off of West Africa, and it could be a very active hurricane year. The sea surface temperatures are following a super warm trend, which means these cyclones could come up the eastern seaboard with heavy rain.” 

These powerful tropical cyclones are born in the turbulent clockwise winds of the Azores High, a high-pressure system in the eastern central Atlantic Ocean, before winding up the coast to Vermont.

Satellite image of Hurricane Irene taken August 26, 2011. Maximum wind speeds reached 121 miles per hour as the storm severely impacted millions of people across the United States. Image courtesy of GOES-East Satellite/NOAA/NASA.
“There’s typically a strong Azores High pressure center bridging from Bermuda to North Carolina,” Hill notes. “The high-pressure zone affects the warmer ocean currents and stronger winds at southern latitudes in Florida and the Caribbean, which become very active. These storms are already affecting the Gulf of Mexico and at some point, they turn north, and a lot of times these systems exit through New England. But that’s an inland track.

“The real threats to watch out for are the well-developed ones that stay along the coast,” he continues. “The lack of a jetstream blowing apart these tropical storms, in addition to when they are symmetric, like a circle, the better the chances are of these storms holding together, strengthening, and becoming super hurricanes. There is a threat of some of them working their way up the coast or inland from the Gulf Coast. The threat will be higher this year than it was last year, but it is difficult to nail down these predictions.”

Hill says that weather predictability is becoming more challenging in a changing climate with extreme sea surface temperatures. He also anticipates that lake and pond temperatures will be warmer than normal.

Hill predicts Vermont is not likely to experience the same catastrophic flooding as in the summer of 2023, but he explains the effects of increased temperatures on flood risk. 

“When it gets warm, there are more thunderstorms. The updrafts of the thunderstorms are stronger, leading to additional severe weather. This means we have to watch for daily heavy downpours that add up to increased runoff and potential flooding. This is going to be with us for the rest of our lives in Vermont. But on occasion, it will go the other way, too, and we will get droughts.”

Hill expressed concern about how fossil fuel usage exacerbates extreme weather patterns. “I’ve seen a lot of weather and the scarier aspects of climate, and we need to get off fossil fuels. We are going to see a lot of bad weather due to fossil fuels, and it will affect our climate significantly. It is only going to get a lot worse. We need to stop treating the atmosphere like an open sewer because the ramifications come back and bite us. 

Ecological resilience through floodplain restoration is another focus of Hill’s. “We have to value our floodplains, now we are going to get more flooding because of the higher water vapor and warmer microphysics holding more water in the atmosphere as the temperatures warm. “There is no normal, there is no static picture. We’re going to have to be resilient, we’re going to have to value our rivers and streams that fill up with floodwaters and try to work with nature rather than against it. We need to stop narrowing our rivers and work with floods.” 

Hill will be speaking about the “Theory of Change” at the Unitarian Church of Montpelier on Aug. 14 from 6 to 8 p.m. 

350VT describes the talk on its website: “It can feel like we’ve passed the point of hope for our climate. But for centuries, social movements have defied expectations, to create change where none was thought possible. Join meteorologist Roger Hill to learn the latest science on where we’re at — and discuss how grassroots organizing can be a tool to respond with the urgency our crisis requires.”

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