Another tropical record broken, but numbers don’t tell full story

Josephine becomes earliest J-named storm to develop in a parade of weak systems this season

Tropical Depression 11 forecast cone.
Tropical Depression 11 forecast cone.

JACKSONVILLE, Fla. – Tropical Storm Josephine, formed Thursday morning setting a new record for the earliest J-named storm in the Atlantic basin.

If it seems like there have been more tropical storms this season you are correct. Many storms have set early-season records this year including Edouard, Fay, Gonzalo, Hanna and Isaias.

The season’s third storm, Cristobal, which soaked downtown Jacksonville with flash flooding June 7, was also the second-earliest landfalling named storm on record to strike Louisiana.

Josephine developed earlier than the previous record set by Jose on Aug. 22 during the infamous 2005 hurricane season. That year had 28 tropical cyclones, the most on record and managed to extend the list of names into the Greek alphabet and saw several powerful and long-lived hurricanes.

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Many storms, many weak ones

While the nine named storms so far have been remarkable, the number does not tell the whole story. Josephine, like most of the numerous storms this season, will -- fortunately -- not have much longevity or strength. Dry air to the north and increasing shearing winds by the weekend is expected to prevent the storm from becoming a hurricane.

So far this season storms have been weak and short-lived with very low levels of accumulated energy; a characteristic measured by an index called ACE.

The ACE index is used to calculate the intensity of the hurricane season and is a function of the wind speed and duration of each tropical cyclone.

While there’s been a high number of storms this year, the total amount of energy produced this season is a low 23.

The 2019 Atlantic hurricane season had an ACE of about 130 which is greater than the 1981-2010 average value of 104. Only eight of the 18 storms lasted more than 72 hours, and seven of them lasted 24 hours or less.

The remainder of the season could make up the difference in low ACE levels with activity forecasted to pick up by late August and into the Sept. 10 peak.

Just a couple of strong storms like last year’s Dorian and Lorenzo could make up the ACE deficit. Those two storms combined for more than 60% of 2019′s ACE, or about 75% of the ACE observed in an average season.

Dorian’s winds were among the strongest of any Atlantic hurricane in history before it made landfall in the Bahamas

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