Eastern Pacific Hurricane Season Begins Monday – Here's How It Impacts The US

Why the Eastern Pacific season starts earlier than the Atlantic: The Eastern Pacific season's start date is just over two weeks earlier than the official beginning of the Atlantic season. This is due to warmer waters and the fact that wind shear is typically weaker earlier in the season compared to the Atlantic.

B​ut as we've seen in recent years, the Atlantic can also see storms before its official start date of June 1. An unnamed subtropical storm even formed in January of this year.

T​his year's Eastern Pacific names list starts with Adrian. This year's list is the same one used in 2017. Lists are repeated every six years unless a storm name is retired because of the severity of its impacts.

A​n average of 15 named storms form in the Eastern Pacific each season, based on the 1991-2020 average. That number of storms this year would get the basin to the name Otis.

H​ow The US Is Impacted

Many Eastern Pacific tropical storms and hurricanes move away from land and are only a concern to shipping interests. But sometimes, the weather pattern can allow these systems to affect the southwestern U.S. and Hawaii.

Last year's former Hurricane Kay was a fresh reminder of Southwest U.S. impacts. Kay tracked northward near Mexico's Baja California Peninsula while weakening from a hurricane to a tropical storm and then a remnant low in September 2022.

Even though Kay didn't reach the U.S. as an intact tropical cyclone, its moisture still triggered flooding in parts of Southern California and neighboring Arizona. Here are a few examples of impacts the region experienced, according to the National Hurricane Center report:​

-Debris flows caused by heavy rain falling on wildfire burn scars damaged or ​destroyed 30 homes and contributed to one death in San Bernardino County, California.

-​More than 50 people had to be rescued because of a mudslide near Lake Hughes, California.

-​Roads were damaged or washed out in Death Valley National Park, leaving about 40 vehicles stranded.

-​Flash flooding in Getz, Arizona, required multiple water rescues and inundated several homes.

Arizona is the Southwest state with the most tropical storm encounters. According to the National Weather Service in Tucson, eight tropical storms or depressions have remained intact and impacted Arizona directly since 1965. Five of these were tropical storms with sustained winds of 39 mph or higher.

Moisture from the remnants of storms is more often a concern. The remnants of numerous other storms have affected Arizona and other parts of the Southwest over the years. T​hat's because even though storms often fall apart well to the south, the leftover moisture and energy can still reach the region.

E​astern Pacific storms can sometimes flirt with a Hawaii encounter. Hurricane Iniki in 1992 might be the most serious example of the impacts Eastern Pacific tropical cyclones can generate in Hawaii. Iniki is the costliest hurricane in Hawaii's history; It originated in the Eastern Pacific on Sept. 5 and moved into the Central Pacific, where it became a powerful hurricane.

The island of Kauai was hit especially hard by damaging winds when Iniki made landfall there as a Category 4. Many structures were wiped out by storm surge flooding and large, battering waves along the southern coast.

Hurricane Douglas was the last close call for the Hawaiian Islands in July 2020.

Unlike a number of other hurricanes that originated in the Eastern Pacific, Douglas didn't lose its intensity that quickly as it tracked into the Central Pacific toward Hawaii.

Luckily, the southern eyewall of Douglas passed just north of Maui, Oahu and Kauai, sparing those islands from seeing the worst of the hurricane's strong winds and heavy rainfall.

Hurricane Lane's Hawaii approach in 2018 was another close shave for the nation's 50th state. Lane developed over the Eastern Pacific in August 2018 and crossed into the Central Pacific Ocean.

After intensifying to a Category 5 hurricane southeast of Hawaii, Lane weakened significantly as it passed more than 100 miles south of the island chain. Parts of the islands were swamped by flooding.

California has seen rare landfalls. Southern California is the only portion of the Pacific coastline in the Lower 48 that could see a tropical storm or hurricane landfall from the Eastern Pacific. Although such an event is extremely rare, history shows it can happen.

On Oct. 2, 1858, the only known hurricane to hit Southern California slammed into San Diego. Sustained hurricane-force winds resulted in extensive property damage.

Only one tropical storm has made landfall in Southern California since then. In September 1939, a tropical storm with 50-mph winds hit Long Beach. Flooding caused moderate crop and structural damage, according to the NWS in Oxnard. High winds surprised the shipping industry in the area, killing 45 people.

Cool ocean temperatures in the path of the tropical systems trying to reach the Pacific coast are the primary reason landfalls are so rare in Southern California. Coastal waters get dramatically cooler as you move northward along the coast from Mexico.

As in 1858, any hurricane would have to be moving fast enough, over waters just warm enough, to maintain its intensity on the way northward to have a California landfall.

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