Andrea kicks off Atlantic hurricane season

On Monday afternoon, a low pressure system south of Bermuda was upgraded to Subtropical Storm Andrea, the first of the 2019 hurricane season, and 11 days before the official beginning of the season.

This makes 2019 the fifth consecutive year that a named storm has formed before the official start of Atlantic hurricane season on June 1.

Andrea has a very brief window of time to exist before getting absorbed by an approaching cold front. Increasing wind shear — which is disruptive to the storm’s circulation, nearby dry air, and cool ocean temperatures will combine to dissipate this storm within a couple of days.

The forecast from the National Hurricane Center is for Andrea to turn to the northeast on Tuesday, which will bring it close to Bermuda. The impacts there will be minimal though — with just some breezy rain showers possible today.

Andrea in historical context

Andrea, which formed on May 20, becomes the sixth preseason storm to develop in the last 10 years. Here are the other storms that have formed prior to June 1 over the past decade: Alberto 2012 (May 19), Beryl 2012 (May 25), Ana 2015 (May 8), Bonnie 2016 (May 28), Arlene 2017 (April 20), and Alberto 2018 (May 26).

This list omits Alex which formed on Jan. 16, 2016. While it may be technically part of the 2016 season, it was meteorologically a remnant of the 2015 season. But if you wish to include it in your list, then we’ve seen seven preseason storms in the last decade.

There is clearly a trend toward earlier instances of first storm formation over the past five decades. The median date over this period is June 20, with a range spanning from April 20 to August 30.

Clearly, there’s nothing magical about the official June 1 start of hurricane season. The start and end dates of the official hurricane season were never intended to contain all of the activity, just the vast majority of it.

When an official “hurricane season” was first defined about 85 years ago, it spanned June 15 to Oct. 31, then it was adjusted to June 15 through Nov. 15, then June 1 through Nov. 15, and finally to June 1 through Nov. 30 in 1965 where it has remained. It could certainly be adjusted again. If it is ever expanded to May 15 through Nov. 30, it would conveniently match the East Pacific hurricane season.