Hurricane season starts on June 1, and like the last two seasons, it is expected to be busier than normal.
Water temperatures in the Atlantic Ocean have spiked, and are now warmer than normal, which can provide fuel for the storms.
Jhordanne Jones researches tropical meteorology at Purdue University and took notice of the increase, as did many of her colleagues. Earlier in the year, the temperatures were actually below normal. But it changed quickly.
“We did a complete 180 between March and April.”
Average water temperatures in the tropical Atlantic Ocean. Data: NOAA. Graphic: Climate Central.
Tropical cyclones are the more generic term for tropical storms and hurricanes. Atlantic storms are called hurricanes, and western Pacific ones are called typhoons, but they are structurally the same type of storm.
Before tropical cyclones can develop, the atmosphere needs to be prepared as well. This season, a large-scale La Niña phenomenon is in place. La Niña is a paired connection between the atmosphere and the Pacific Ocean that leads to colder than normal water in the central and eastern Pacific near the equator.
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The atmospheric component leads to more uniformity in the direction of the winds across the tropics, including in the Atlantic. A uniformity in direction allows tropical systems to organize and remain intact more easily.
The opposite case, El Niño, leads to more wind shear, or less uniformity, making it more difficult for tropical systems to develop and thrive.
So in general, La Niña years are more active than El Niño years. For the curious, these are two ends of an even broader circulation known as ENSO — the El Niño-Southern Oscillation.
Several organizations produce outlooks for the Atlantic hurricane season, but some of the pioneering work began at Colorado State University from William Gray in 1984. One of his graduate students, Philip Klotzbach, continues to lead the research and outlooks today.
In an average year, there are about 14 storms that reach tropical storm or hurricane status in the Atlantic basin (Atlantic Ocean, Caribbean Sea and Gulf of Mexico) with an active storm on 70 days during the season. This year, the CSU team expects another year above average, with 19 storms and 90 days during the season with an active storm somewhere in the Atlantic basin.
NOAA, the parent agency of the National Weather Service, will announce its hurricane season outlook on May 24, and the CSU team will update its outlook on June 2.
Figuring out where a tropical system will hit before the season even starts remains a game involving statistics, history and climatology. The Gulf Coast, Florida and the Southeast have historically been at greatest risk. But there is emerging evidence that areas farther north will be at greater risk as the climate continues to warm.
Even so, there are reliable locations to look for the storms to form at different times in the season. For example, the Gulf of Mexico is shallower than the open Atlantic, which plays a role.
Jones notes, “Earlier in the season, there will be more forming in the Gulf …….