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“Local” storm threatens US coast. What is it?


“Local” storm threatens US coast. What is it?

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A storm currently brewing off the southeast coast that may or may not become Tropical Storm Helene when it makes landfall is an example of what meteorologists call a “home-made” storm.

These tropical storms and hurricanes are those that can form quickly near the coast of the United States, as opposed to those that move slowly across the Atlantic over a period of days or even weeks.

And surprisingly, the storm threat in the U.S. mostly comes from these so-called man-made storms, said meteorologist Jonathan Erdman of Weather.com.

In fact, only ten of the 55 hurricanes that hit the United States between 1995 and 2023 first developed into hurricanes in the Atlantic between the Lesser Antilles and Africa, he said.

“The vast majority of them first developed into hurricanes in the Caribbean Sea, the Gulf of Mexico or near the southeast coast,” he noted in an online forecast post.

What’s going on with the storm? Will it be Helene?

At 11 a.m. ET, the center of the storm was about 75 miles south-southwest of Cape Fear, North Carolina.

According to the hurricane center, strong winds and heavy rains continue to spread across parts of southeastern North Carolina as the storm approaches land.

The storm would reach tropical depression status as a center emerges and winds become circular before landfall. Tropical storm status named Helene would be reached if sustained winds reach 39 mph, but that seems less likely according to the hurricane center’s 11 a.m. ET update.

Although this storm had consistent winds of 50 miles per hour, it did not have a closed center of circulation, which is required for a named storm. In addition, meteorologists noted that the storm had a frontal boundary, which is not the case with tropical cyclones.

“With little time left before the system moves inland, the likelihood of it developing into a tropical or subtropical cyclone is decreasing,” the center said in a statement.

Even if the storm does not develop into a named storm, significant localized flash flooding and urban flooding, as well as minor river flooding, are possible through this evening in southeastern North Carolina and northeastern South Carolina, the National Hurricane Center said Monday morning. “There is also a risk of isolated flash flooding and flooding across much of the Mid-Atlantic region through Wednesday.”

What is a homemade storm?

According to AccuWeather, a “homemade” or “homebrew” storm is a storm that forms near the coast of the United States and most commonly occurs early in hurricane season. (The official Atlantic hurricane season runs from June 1 to November 30.)

Inland hurricanes pose a greater threat than longer-duration hurricanes from more distant regions of the eastern Atlantic, Weather.com reports, simply because they either form or intensify closer to the United States.

“They do this because the Caribbean Sea and the southern Gulf of Mexico typically have the most abundant supplies of warm, deep water. In the absence of other negative factors, warmer water leads to a stronger hurricane,” Erdman said.

What comes after Helene?

If this storm does not become Helene, the good news is that there are no tropical systems in either the Atlantic or Pacific basins other than Tropical Depression Gordon, which is currently swirling harmlessly out to sea far from land. The system that will become Tropical Storm Helene is not yet known. Storm names after Helene are Isaac, Joyce, and Kirk.

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