What Impacts Should the U.S. Expect from Eastern Pacific Tropical Weather

While most Americans are understandably focused on the June 1 official start date of the Atlantic hurricane season, there is already one tropical weather season underway. The Eastern Pacific hurricane season started on May 15. What does this season have in store? Read on for all of the details.

Start of Eastern Pacific Hurricane Season is Here

The tropical weather season has begun in the Eastern Pacific basin. However, this part of the world's oceans often gets overlooked, as it is not generally as active as the Atlantic nor does it impact as many major masses of land. It is important to realize that tropical weather that originates in the Eastern Pacific can impact the southwestern corner of the U.S. as well as Hawaii, Mexico, and Central America.

The Eastern Pacific hurricane season starts over two weeks prior to the official start date of the Atlantic hurricane season. This earlier start date is because of the warmer waters in this part of the ocean and the more supportive upper-level winds.

Going back through the 1991 - 2020 year average, there have been 15 named storms that come to life each year in the Eastern Pacific. The first name up on this year's predetermined list is Alvin, followed by Barbara, Cosme, Dalila, and Erick.

The bulk of the tropical events that form in the Eastern Pacific remain in the waters to the west of Mexico. Most of these features track to the west and out into the open waters of the Pacific, rarely impacting land. When they do make landfall, they tend to strike Mexico with the greatest frequency. The impacts can also be felt as far as the Desert Southwest and Hawaii.

Mexico is coming off two consecutive years of devastating tropical weather events. Hurricane Otis hit Acapulco as a monster Category 5 storm in October 2023. Otis is now distinguished as Mexico's costliest storm. Tragedy struck again in September of 2024 when Hurricane John impacted Michoacán and Guerrero states. Once again, Acapulco was in the line of fire for the flooding and mudslides. John was responsible for at least 29 fatalities.

The southwestern corner of the U.S. is generally well protected from tropical weather due to the storms usually breaking apart before they reach the U.S. coastline. However, this is not always the case. Sometimes the weather patterns allow the energy and moisture associated with these features to sneak to the north and dump torrential rain over the Southwest.

You only have to go back to August of 2023 to find the last time that a storm from the Eastern Pacific resulted in significant impacts for the mainland U.S. What was left of Hurricane Hilary was responsible for about $900 million worth of damage across California and the interior portions of the West.

Some of the storms that are born in the Eastern Pacific can also go on to impact Hawaii. Hurricane Iniki in 1992 made landfall on the island of Kauai as a Category 4 storm. The end result was damaging winds and high storm surge.

The Hawaiian islands have also seen a number of close calls more recently. This includes brushes by Hurricane Douglas in July of 2020 and Hurricane Lane in August of 2018.

Other Interesting Facts About the Impacts of Eastern Pacific Storms on the U.S.

Despite its warmer location, why is the West Coast more protected from tropical weather when compared to its East Coast counterparts? The answer lies in the cooler waters that churn off the coast of the western U.S. Sea-surface temperatures fall significantly from the area north of Mexico's southern Baja Peninsula and into U.S. territory. Any tropical storms or hurricanes that survive the trip to the north tend to weaken and break apart when they reach the colder water closer to the U.S. coastline.

As such, California has only seen a few landfills. The only known hurricane to strike Southern California goes back to October of 1858. The hurricane-force winds caused widespread property damage at a time when structures were not as protected. A tropical storm is also on record for coming ashore at Long Beach in September of 1939.

While the U.S. does not see the wrath of the Eastern Pacific storms, that does not make them any less concerning. This part of the Pacific is home to the strongest storm that has ever sprung up in the Northern Hemisphere. This award goes to Hurricane Patricia from October of 2015. Patricia boasted maximum sustained winds of 215 mph when it churned off the Pacific Coast of Mexico. Keep in mind that the wind speed threshold for a Category 5 destination is 157 mph.

Hurricane Patricia made landfall as a Category 4 storm in a rural area located to the north of Manzanillo. Two small villages known as Emiliano Zapata and Chamela took the brunt of the storm.

We will continue to monitor what is happening in the Eastern Pacific in the months to come. Meanwhile, the National Hurricane Center (NHC) is also ratcheting up its operations to keep tabs on what is going on in the Atlantic basin as the official start of this season is just two weeks away.

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