The United States Is Facing Four Simultaneous Tropical Threats - Pacific Standard

The United States Is Facing Four Simultaneous Tropical Threats

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In a year of record temperatures, the U.S. has a surplus of storms heading its way — and Hawaii might have to get used to more hurricanes.

By Eric Holthaus

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Hurricane Iselle hits the Big Island of Hawaii as a tropical cyclone in August 2014. (Photo: Johnny Silvercloud/Flickr)

It’s peak hurricane season, so it’s no surprise that the tropics are heating up. This time of year, Northern Hemisphere ocean temperatures are among their warmest annual levels, and upper atmospheric winds are generally calm enough to allow storms to organize with little interference.

In 2016 — during what’s likely to be the planet’s warmest year in history — all that is happening right on cue. Global tropical cyclone activity is running just a bit above average so far this year, but not unusually so.

What is a little surprising, though, is how many of these storms are headed toward American soil at the moment. As of Tuesday morning, no less than four tropical cyclones have the United States in their sights.

The only one that will unavoidably make landfall — technically defined as its center crossing over land — is Tropical Depression Nine, formerly known as Invest 99L. Meteorologists have been tracking this system for at least 11 days now, since it emerged off the coast of West Africa. Recent weather models have become less ominous about the system, and the National Hurricane Center expects it to reach land in northwest Florida as a mid-strength tropical storm.

There’s still a small chance — I’d say 10 percent or so — that this storm will intensify beyond that and reach hurricane status before landfall. No matter its final intensity, it will be headed toward some of the most storm-surge-prone coastline in the country, thanks to the gentle slope of the continental shelf in northwest Florida. The National Hurricane Center expects a few parts of Florida to bear more than six feet of water above ground level when the storm hits. According to meteorologists Bob Henson and Jeff Masters, in a worst-case scenario, the storm could bring nearly 10 feet of seawater ashore if it hits at high tide as a category-one hurricane.

The current situation points toward a changing relationship between Hawaii and hurricanes.

In contrast, Tropical Depression Eight, headed toward the North Carolina Outer Banks, is expected to struggle on its approach to land. At worst, it will be a minimal tropical storm, and could bring heavy surf that further erodes the fragile barrier islands — already under threat from rising seas. (Hermine and Ian are the next two names on the Atlantic list, and will be assigned to TD 8 and TD 9 in the order of which one strengthens first.)

Meanwhile, in the Pacific, two strong hurricanes — Madeline and Lester — are currently heading toward Hawaii. To say that a double hurricane landfall in Hawaii in the span of less than a week is rare would be a serious understatement: It has never happened in history, according to Hawaiian hurricane records that date back to 1949. Hawaii as a whole has seen only two hurricane landfalls during that entire period — Dot (1959) and Iniki (1992).

It’s possible that neither Madeline nor Lester makes landfall, but the current situation points toward a changing relationship between Hawaii and hurricanes. As the Pacific Ocean warms, hurricanes are drifting a bit further north toward Hawaii, currently at the northern edge of a zone that’s favorable for their formation. Two of the five Hawaii landfalls of tropical storm strength or greater on record have occurred in the past three years.

And these four aren’t all that may be headed our way. On the edge of reliable forecasts, about a week from now, a tropical system currently emerging off West Africa may also head toward the Caribbean or the southeastern U.S. As I said, it’s peak season.

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