Eastern Pacific's First Storm of Hurricane Season May Develop This Week at an Unusually Late Date

Jonathan Erdman
Published: June 25, 2019

The first tropical storm of the 2019 Eastern Pacific hurricane season may form this week and awaken a basin at an unusually late date for the season's first named storm.

The National Hurricane Center (NHC) has highlighted an area several hundred miles off the Pacific coast of Mexico where there is a high chance of tropical development this week.

Potential Tropical Development Area

Weather forecast models over the past several days have indicated the potential of low pressure to form within the typical east-west band of thunderstorms known as the monsoon trough, and then gain strength.

(MORE: 2019 Atlantic Hurricane Season Outlook

These forecast models also suggest that this system, which would be named "Alvin" if it gains at least tropical storm intensity, won't threaten land and track west-northwestard away from the Mexican coast.

Dr. Michael Ventrice, an atmospheric scientist at The Weather Company, an IBM Business, said a disturbance known as a convectively coupled Kelvin wave passing over the Eastern Pacific Ocean may contribute to the system's tropical development.

Unusually Late 'A' Storm

It's not unusual for the opening month of the Atlantic hurricane season to be quiet. While we already had short-lived Subtropical Storm Andrea in late May, a typical Atlantic season may not see its first named storm until the second week of July, according to the NHC.

(MORE: Here's What Typically Happens Early in the Hurricane Season

The Eastern Pacific hurricane season begins in mid-May, about two weeks earlier than the Atlantic season's official June 1 start.

This is because strong, shearing winds and dry air present in the Atlantic Basin early in the season aren't typically in place over the Eastern Pacific Basin.

By late June, one or two named storms forms in the Eastern Pacific in an average season, according to Dr. Phil Klotzbach, tropical scientist at Colorado State University.

This year's Eastern Pacific "A" storm date is nearing a record.

Only once has the Eastern Pacific Basin failed to produce a single named storm through June in reliable data since 1971.

That happened just three years ago, when Tropical Storm Agatha checked off the "A" storm box on July 2, 2016.

Why the Slow Start?

Why the Eastern Pacific Basin is slumbering so late is a tough question to answer.

Ventrice told weather.com it's probably driven by something other than either the Kelvin waves or a 30- to 60-day oscillation of rising and sinking air, known as the Madden-Julian Oscillation, that can give a boost to tropical cyclone activity around the globe.

Not even El Niño is giving the basin a boost.

Typically, El Niño years lead to very active Eastern Pacific hurricane seasons.

However, this El Niño is weak and exhibiting more warming in the equatorial waters of the Central Pacific, near and south of Hawaii, than farther eastward, which may be one factor keeping a lid on the Eastern Pacific activity.

(MORE: Hawaii Set More Than a Dozen Record Highs in the Past Month

Sea-surface temperature anomalies in degrees Celsius from June 9-15, 2019. The pool of warmer-than-average water in the central equatorial Pacific Ocean south of Hawaii is highlighted by the red arrow. Less warmer-than-average water well south of Mexico is highlighted by the black arrow.

The late start had no impact on the rest of the 2016 season. Nineteen named storms, 11 of which were hurricanes, formed in the Eastern Pacific Basin that year.

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.