Waters in the tropical Atlantic Ocean are at their warmest levels on record, which could help fuel an exceptionally early seasonal hurricane by the middle of the week.
A tropical disturbance 1,000 miles west of the coast of Africa is predicted to steadily organize over the coming days, with high chances of it becoming a named storm over the next 48 to 72 hours. It comes about two months ahead of schedule for a storm to form in that part of the Atlantic Ocean, but record-warm ocean waters are probably jump-starting a season that could turn out stormier than initial forecasts.
The National Hurricane Center estimates the system, now dubbed Invest 92L, has an 80 percent chance of formation within the next 48 hours, and a 90 percent chance this week. Its long-term prospects include the potential to affect the Lesser Antilles and Leeward Islands in the Caribbean about six or seven days from now.
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Most computer models project this system will reach hurricane strength.
Assuming the system earns a name, it would be called Bret, and would be the third tropical storm of 2023. (The first was an unnamed subtropical storm that formed over the open North Atlantic in January; the National Hurricane Center determined it was a storm in post-analysis several months later.)
The warmth of the Atlantic and other oceans has astonished meteorologists and climate scientists alike. Brian McNoldy, a tropical weather researcher at the University of Miami, tweeted that the Atlantic warmth was “beyond extraordinary” with just a “1-in-256,000 chance of observing.”
Early-season advance forecasts called for a slightly below-average hurricane season in 2023, owing to the emergence of an El Niño weather pattern, which is known to bring sinking air and strong high-altitude winds over the tropical Atlantic; both would be less conducive to storm formation. Now, however, most forecasting agencies are expecting an average or even above-average season, mainly because of how warm the water is.
The system now
On Sunday morning, Invest 92L was several hundred miles southwest of the Cape Verde islands. An overnight flare-up downpour and thunderstorm activity within the roiling mass of clouds has since diminished. The system lacks persistent thunderstorms, but does posses an organized circulation, or broad spin.
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It’s unclear why 92L is struggling to sustain thunderstorms; while dry air at the mid-levels is present north of the nascent storm, it’s neither intruding on nor choking the circulation. Wind shear, or a disruptive change of wind speed and/or direction with height known to weaken developing systems, is also modest.
The next steps for 92L to develop would be twofold. First, the system would need to “fill in” with thunderstorms. That may happen in the next 24 to 36 hours. It also would need a more defined center of circulation spanning multiple layers of atmosphere that the remainder of the storm could develop around. Thunderstorms are often integral in vertically stretching and intensifying a pocket of broader surface spin, jump-starting this process, so overcoming the second obstacle is sort of predicated on overcoming the first.
Where the system is going
Weather models are in a consensus that the storm system will drift westward. Its rate of strengthening, assuming it does develop, is key in determining its specific path, though.
If its showers and thunderstorms strengthen and blossom more quickly, it will be a taller system, since it will have more thunderstorms reaching higher into the atmosphere. This would cause the storm to feel high-altitude winds, which would tug the system more quickly to the north, causing it to curve out to sea before reaching the Lesser Antilles. (Picture being in a sailboat and hoisting the sails — the higher you raise them, the more wind you’re going to catch, and the faster you’re going to move.)
If it organizes more slowly, however, which is appearing increasingly likely, it would continue its westward course. That would eventually spell concerns for the Lesser Antilles. The storm’s effects there could include high seas, torrential rain and damaging winds, but they wouldn’t arrive until late in the workweek.
How strong could it get?
Most computer models project this system will become a tropical storm, with winds of at least 39 mph, by Monday night or Tuesday. Between Wednesday and Friday, they generally forecast it to become a Category 1 or 2 hurricane, although there are a couple that predict it could become a major Category 3 storm.
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The intensity forecast is less certain as time wears on because it depends on the system’s track. If the storm passes over the Lesser Antilles and into the Caribbean next weekend, conditions may become less hospitable than if it stays over the open waters of the Atlantic.
How typical is this?
This map highlights (🟡) where current sea surface temperatures are warmer than they would typically be during *September*!
In other words, yellow areas indicate where the sea is as warm right now as it would normally* be in three months time!
It includes large swaths of the… pic.twitter.com/kkd0GS5SJG
— Ben Noll (@BenNollWeather) June 17, 2023While June tropical storms are common, they’re usually either “homegrown” storms that form at the tail of cold fronts in the Gulf of Mexico, or fleeting subtropical swirls over the open Atlantic. For a classic system to form in June from an African easterly wave — or the seeds of tropical systems that roll off the continent during peak hurricane season — is rare. The so-called MDR, or “main development region,” doesn’t usually awaken until late July or early August.
In fact, there have only been four MDR tropical storms on record that have formed during the month of June. The most recent was Elsa in 2021, which eventually became a hurricane in the eastern Caribbean before weakening back into a tropical storm and affecting Florida, then riding up the Eastern Seaboard.
That said, ocean waters are as warm as they’d be in September and the atmosphere is responding accordingly. The current conditions portend ominously for the late-August-to-September peak of hurricane season, as the waters still have another two-plus months to warm, and the atmosphere will probably become increasingly hospitable for strong storms.
Jason Samenow contributed to this report.
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