What the 2019 Atlantic Basin hurricane season revealed

Sissel Mosvold embraces a volunteer who helped rescue her mother from her home, flooded by the waters of Hurricane Dorian, in the outskirts of Freeport, Bahamas, Wednesday, Sept. 4, 2019. Sissel's 84-year-old mother was taken to a hospital in Freeport.

Advanced technology has become a game-changer in the field of hurricane forecasting and the 2019 Atlantic Basin hurricane season is further proof.

Seven of the 17 Atlantic Basin storms in 2019 lasted 24 hours or less as a named storm - "the most extremely short-lived named storms [in one season] on record," according to Colorado State University meteorologist Philip Klotzbach, who specializes in Atlantic Basin hurricane forecasts. The old record was six set in 2005.

Also, eight of the 17 named storms had maximum sustained wind readings of 52 mph (45 knots) or lower. Winds of that speed are categorized in the lower end of the tropical storm category, which ranges from 40 to 73 mph (34 to 63 knots).

"You go back 25 or 30 years and there probably would have only been 10 storms named this year," said AccuWeather Founder and CEO Dr. Joel N. Myers.

Only five seasons in the last 50 years had more named storms, and four of those seasons have occurred since 2005 (2012, 2011, 2010, 2005).

The National Oceanic and Atmospheric Administration (NOAA) acknowledges there has been "a rather large increase in short-lived tropical storms and hurricanes in the last decade ... that may be influencing the climatological average number of tropical cyclones in the Atlantic basin." Meteorologists recognize 12 as the average number of named storms during the Atlantic Basin hurricane season.

"What has changed is the technology," said AccuWeather Hurricane Expert Dan Kottlowski. "We have much higher-resolution satellite imagery than we had then. When the first satellite was launched back in the ‘60s, we'd get maybe one swath over the ocean every couple of days, so we would rarely see if a storm lasted only for 24 hours. It was never detected."

Satellite imagery was first used for forecasting in 1966. The 30-year average for named storms from 1936-65 was 9.8; it was also 9.8 from 1966-95. However, in the 23 years since, the average number of named storms is 14.5 a year, not counting 2019's 17.

"It wasn't until the 1970s when we launched geostationary satellites that we were able to see more," Kottlowski said. "And the resolution has increased since; in the last 10 years, we've had finer resolution than ever before. For example, maybe a storm that we didn't know had an eye, now we can see has an eye and we didn't think it did in the past."

AccuWeather predicted in April that there would be 12 to 14 named storms including tropical storms and hurricanes. NOAA predicted a much broader range of 10 to 17 named storms. AccuWeather also forecast for five to seven hurricanes (there have been six), two to four major hurricanes (three so far), two to four landfalling named storms (four so far), and an Accumulated Cyclone Energy (ACE) forecast of 100-120 units (the total so far is 124). NOAA predicted five to 9 hurricanes and two to four major hurricanes.

"The Polar Orbiting Satellite Images (POES) that we're getting now are very important because they use a device called a scatterometer, which allows us to better estimate what the winds are around a system," Kottlowski said. "That wasn't even around until 1999."

The Atlantic hurricane season officially lasts from June 1 through Nov. 30, when 98.4 percent of hurricanes have occurred in the Atlantic Basin, though hurricanes can form in any month. Counting 2019, all 297 hurricanes that have made landfall in the continental U.S. since 1851 occurred during hurricane season.

The start of November means "for all practical purposes, the threat of a significant hurricane hitting the United States mainland in November is extremely small," said Myers. Since 1851 there have been only three Atlantic Basin hurricanes in November that have reached landfall in the continental U.S., according to records from NOAA's Hurricane Research Division.