Tropical Storm Andres Continued Recent Stretch of Early Hurricane Season Starts

 Jonathan Erdman

Published: May 10, 2021

Tropical Storm Andres launched the 2021 Eastern Pacific hurricane season early in what's been a tendency over the past several years in the Atlantic Basin as well.

Andres spun up on Mother's Day several hundred miles off Mexico's Pacific Coast, the earliest a tropical storm in the Eastern Pacific Basin has formed in reliable records dating to the early 1970s.

The Eastern Pacific hurricane season runs from May 15 through Nov. 30, a period that captures the large majority, but not all of, the tropical cyclones in that basin.

Recently, we've seen a number of such preseason tropical cyclones in the Eastern Pacific.

In 2020, the basin produced its first April tropical depression on record, T.D. One-E, on April 25.

Satellite images of Tropical Depression One-E on April 25, 2020 (left), and Tropical Storm Andres on May 9, 2021 (right).

In 2018, the season's first tropical depression jumped the official start of the season by five days.

And in 2017, Adrian became the record-earliest Eastern Pacific tropical storm on May 9, only to be leapfrogged by 2021's Andres, which became a tropical storm about 12 hours earlier than Adrian.

(MORE: Why the Eastern Pacific Hurricane Season Matters to the U.S.)

We've also had some intense Eastern Pacific hurricanes early in the season in recent years.

In 2015, Andres, then Blanca, each reached Category 4 intensity on May 31 and June 3, respectively.

Blanca was the earliest second Eastern Pacific hurricane on record in the Eastern Pacific Basin. Blanca then became the record-earliest storm to landfall in the Baja Peninsula but weakened to a tropical storm before doing so.

Zoomed-in infrared satellite image of Hurricane Blanca on June 3, 2015, over the Eastern Pacific Ocean.

Finally, in 2014, Amanda became the most intense May Eastern Pacific hurricane on record, with winds estimated at 155 mph – just shy of Category 5 strength – on May 25, only 10 days into the season.

As we've written about previously, the Atlantic Basin has also generated at least one named storm before the June 1 official hurricane season kickoff each of the past six years.

A Real Trend?

Is climate change playing a role in this flurry of early activity in recent years?

In 2017, Colorado State University tropical scientist Phil Klotzbach noted there was no noticeable trend in the date the Eastern Pacific hurricane season's first tropical storm formed since 1971.

That lack of a trend still seems to be holding.

Despite 2021's early Andres, 2019's first Eastern Pacific named storm, Alvin, wasn't born until June 26, almost six weeks after the start of hurricane season.

In general, the link between the planet's total number of tropical cyclones and climate change is quite uncertain.

Warming oceans would provide more fuel for tropical storms and hurricanes.

However, a warmer world could also produce a drier atmosphere with less instability for thunderstorms and increased shearing winds that would act to suppress tropical cyclones from forming.

Atlantic preseason activity, while occasionally producing flooding rainfall, usually is more of a curiosity than impactful.

"Many of the May (Atlantic) systems are short-lived, hybrid (subtropical) systems that are now being identified because of better monitoring and policy changes that now name subtropical storms," Dennis Feltgen, National Hurricane Center spokesman and meteorologist, told weather.com in February.

Tracks of all Atlantic named storms that have formed before June 1 in each hurricane season from 2015 through 2020. The black segments of tracks denote when each system was either a remnant low-pressure center or an area of low pressure before becoming a depression or storm.

While not officially moving up the Atlantic hurricane season's start date, the NHC announced it will begin issuing its regular tropical weather outlooks for the Atlantic Basin on May 15, instead of June 1.

And, as Klotzbach has pointed out, when the first Atlantic storm forms doesn't tell you anything about how active the rest of the hurricane season will be.

If anything, it's just another reminder that it's time to firm up your hurricane plan if you live along or near the coast.

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.