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Does the 'Cape May Bubble' really exist?

Does the 'Cape May Bubble' really exist?


EDITOR"S NOTE: This story was originally posted on May 13, 2019

It’s a scenario that happens on occasion in Cape May County: You’re sitting on the beach and see black clouds in the distance.

But as soon as it looks like a downpour is coming, it doesn’t.

“We live in a precarious position, surrounded by water on all three sides,” said Marty Pagliughi, Cape May County emergency management coordinator and mayor of Avalon.

Cape May County, the only county in New Jersey on a peninsula, does see significantly different weather than other portions of the state.

Thunderstorms fizzle away, the sun is out more and more would-be snow turns to rain. While places like Hammonton and Upper Deerfield Township can get caked with 6 inches of snow in a nor’easter, the Wildwoods and Sea Isle City will be all or mostly rain.

The different weather than the rest of the state has led some Cape residents to believe the storms will bypass them.

“The old-time county people kind of know about the phenomenon. I’ve heard of the ‘Cape May Umbrella’ before. It’s not just hurricanes, it’s low-pressure systems,” Pagliughi said.

The northeast winds, which give the nor’easter its name, are an icy, cold breeze the closer to the Interstate 95 corridor you are, because the chillier land is to the northeast.

Along the shore, and especially in Cape May County, that northeast wind is an onshore flow. With water temperatures above freezing, that air will come onto land above freezing, turning snow into rain.

The three bodies of water that surround Cape May County are the key to this phenomenon.

“You get the double sea-breeze. You get cooler water off the bay and ocean and the clouds will clear out of Cape May County and southern Cumberland,” said Jim Eberwine, retired National Weather Service forecaster for Mount Holly.

According to Frederic Fabry, director of the radar observatory at McGill University in Canada, South Jersey experiences six hours’ worth of thunderstorms per year, with one exception: The Cape May-to-Vineland corridor sees four.

Thunderstorm reflectivity between May and August between 12 p.m. to 6 p.m.

Radar reflectivity above 40 dBZ (thunderstorm intensity) between May and August from 12 p.m. to 6 p.m. The Cape May Bubble is clearly in play here, though Cape May County does see thunderstorms later than the rest of the region. 

Between October and March, Cape May averages temperatures more than a degree above Atlantic City International Airport in Egg Harbor Township, which has no body of water to moderate the icy, Canadian air.

Records show Cape May averages warmer weather through May, as temperatures closely follow the temperature curve of the Delaware Bay, which heats up more slowly than the drier land.

Temperatures then even out into June and July. In fact, Cape May has cooler high temperatures from roughly Memorial Day weekend until early August.

“It’s cooler in the summer when you have blasts of hot air coming in,” New Jersey State Climatologist David Robinson said.

This parlays into the biggest truth about this weather anomaly — thunderstorm activity.

“It’s always that exciting hour, hour-and-a-half wait. We’d always be checking the radar on our phones, refreshing the feed to see if thunderstorms over the Delaware Bay were going to hit us. ... You think it’s going to start pouring, and you’re like, ‘Oh crap,’ but then it goes away,” said Whitney Garrison, 33, of Cape May.

Fabry said Cape May and eastern Cumberland counties are heavily influenced by the Delaware Bay. If storms pass west to east, as they typically do, the cooler bay during these months helps stabilize the storms, weakening them to below the thunderstorm threshold used in the Fabry’s study.

Echo Frequency.png

“In the late afternoon or evening, the lower part of the storm has been destroyed by the cooler Delaware Bay, and you only get the mid- and upper-level part of it, which is the ‘steady’ storm,” Eberwine said.

This means a better chance at a dry day at the shore.

Contact: 609-272-7247 Twitter @ACPressMartucci

Sunset Beach Shelf Cloud June 2017

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