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Alberto's Early Formation Has No Bearing on How Active the 2018 Hurricane Season Will Be

At a Glance

Alberto, the first named storm of the 2018 Atlantic hurricane season, developed May 25.
Storms that form before the June 1 start of the season have no bearing on what happens the rest of the year.

The formation of Alberto last week marked an early start to hurricane season, but that doesn't foretell anything about how active the Atlantic Basin will be this season.

June 1 is the official start to hurricane season, but storms occasionally develop before then, including in five of the past seven years (2012-2018).

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Subtropical Storm Alberto in the Gulf of Mexico on May 27, 2018. (NASA)

To answer the question of whether the formation of a preseason storm has any effect on how active hurricane season will be, let's first examine 2015, 2016 and 2017, all of which had named storms before June 1.

This is best done by using a measure of hurricane season activity called the ACE (Accumulated Cyclone Energy) index, which adds each tropical storm or hurricane's wind speed through its life cycle.

The ACE takes into account the number, strength and duration of all the tropical storms and hurricanes in a season. The higher the ACE value, the more active a season was. That said, the ACE value doesn't necessarily reflect the severity of impacts to land in a given season.

As you can see, there is quite a disparity in the ACE indices for the last three years with preseason storms, ranging from a low of 63 to a high of 226.

2017: Arlene developed in April; Season ACE: 226
2016: Alex developed in January and Bonnie in May; Season ACE: 141
2015: Ana developed in May; Season ACE: 63
Average Seasonal ACE (1981-2010): 92

To put this in perspective, 2017 was the seventh-most active hurricane season dating to 1851 when using the ACE metric. The 2015 season had an ACE of 63, which puts it in the bottom half of the most active seasons on record. In between was 2016, which had above-average activity.

An initial look at those three years indicates there is no correlation between preseason storms and whether a hurricane season will be active or inactive.

For more proof, let's expand out and look at years where the first named storm developed in May.

Not including 2018, a total of 14 years since 1950 have had the first named storm in May. Those seasons were half above and half below the 1981-2010 ACE average, according to Dr. Phil Klotzbach, a tropical scientist at Colorado State University.

"Since 1950, there is no relationship between date of first Atlantic named storm formation and overall Atlantic seasonal hurricane activity," Klotzbach said in a tweet before Alberto formed.

Take 2004, for instance, when Alex wasn't named until Aug. 1. Alex was followed by 14 named storms that year, including the big four hurricanes – Charley, Frances, Ivan and Jeanne – that hammered Florida in 45 days from mid-August to late September.

The ACE for the 2004 season ranked in the top six highest dating to 1851 despite the slow start with no named storms in that season's first two months.

Various seasonal forecasts are predicting that the 2018 hurricane season will have near- or above-average activity. Regardless of what seasonal forecasts project, it's important for coastal residents to be prepared every year.

(MORE: 2018 Hurricane Season Outlook)