Tropical Storm Bret aims for the Caribbean with another system on its heels

It’s the middle of June and the tropics are acting like it’s August.

Tropical Storm Bret formed deep in the tropical Atlantic Ocean on Monday, becoming one of just a tiny handful of storms on record to form east of the Lesser Antilles this early in hurricane season.

Bret is a classic storm…for the middle of hurricane season. The storm formed from a tropical wave that rolled off the western coast of Africa. Faced with warmer-than-usual sea surface temperatures and favorable moisture and wind shear, the disturbance grew into our second named storm of the year.

Forecasters with the National Hurricane Center (NHC) expect Bret to hit the Lesser Antilles as a high-end tropical storm on Thursday. Tropical storm watches are in effect for Barbados and Dominica ahead of the the storm’s arrival, where high winds and heavy rains could cause some flooding and power outages.

Bret’s on borrowed time, fortunately, as increasing wind shear over the eastern Caribbean should tear the storm to shreds by the end of the week.

Hot on its heels, though, is a similar disturbance that forecasters give an 80 percent chance of developing over the next couple of days. This system, dubbed Invest 93L for tracking purposes, will probably follow a track a little farther north than the one Bret is on, and it should suffer a similar fate by the weekend, falling apart in the face of disruptive wind shear. If that system becomes a tropical storm, it would earn the name Cindy.

What on earth is going on?

It’s extremely unusual for storms to develop this far out in the Atlantic Ocean this early in the year. Hurricane activity tends to follow a predictable trend as the season progresses. Systems that form in June tend to develop close to the U.S. and Mexico, sprouting from seeds like stalled cold fronts and decaying clusters of thunderstorms that roll offshore.

Usually it’s not until July and August that we start to see tropical activity pull farther out into the Atlantic basin, with conditions over the Atlantic becoming more hospitable to the tropical waves that roll off the western coast of Africa during the sub-Saharan summer monsoon.

Things happened to line up just right this year, defying the odds to give us at least one—possibly two—named storms far outside where they’re supposed to form in June.

Sea surface temperatures across the entire Atlantic Ocean are exceptionally toasty, with much of the basin coming in 1-2°C warmer than normal for the middle of June. This kind of abnormal warmth across the Atlantic is unprecedented in its intensity and coverage.

We’re also entering a formidable El Niño in the eastern Pacific Ocean. This pattern of warmer-than-normal sea surface temperatures off the west coast of South America tends to generate destructive wind shear that disrupts the Atlantic hurricane season.

However, given just how toasty the Atlantic is this year, it’s hard to tell how much El Niño will actually affect hurricane activity this year. If the Atlantic’s warm spell keeps up, we could have a busy season on our hands despite the historical odds against it.

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