Frenzy of tropical activity in Pacific could create rare weather phenomenon

A cluster of tropical activity has developed across the Pacific Ocean, as three features battle for dominance and hold the potential for a phenomenon called the Fujiwhara Effect to occur.

"Tropical activity has picked up across the eastern Pacific," said AccuWeather Meteorologist Alex DaSilva.

The three main areas of interest are Tropical Rainstorm 9-E, Hurricane Hilda and Tropical Storm Ignacio.

The good news is that all three features are generally moving away from Mexico and will pose no threat to land except for some minor increased wave activity in western Mexico, according to DaSilva.

On Saturday evening local time, a tropical storm in the East Pacific Ocean strengthened into Hurricane Hilda. As of Monday morning, Hilda was a Category 1 hurricane on the Saffir-Simpson Hurricane Wind Scale, located nearly 1,000 miles west-southwest of the southern tip of Baja California.

As Hilda continues to move to the northwest this week, the storm will encounter drier air, stronger wind shear and cooler ocean water.

Hurricanes thrive in moist, warm environments, so each of these will work to degrade Hilda's wind intensity, which could cause it to become a tropical storm again. While Hilda is not anticipated to impact land, shipping interests should be aware of higher seas from the hurricane.

A tropical depression located to the west of Hilda became Tropical Rainstorm 9-E early Sunday morning, local time, about 1,405 miles west-southwest of Baja California and is remaining nearly stationary.

"Due to the lack of organization and convection associated with 9-E, the system has been classified as post tropical," said AccuWeather Senior Meteorologist Adam Douty. Though it was poorly organized on Sunday morning, there is a possibility of the rainstorm becoming a tropical depression again or even a tropical storm before moving into cooler waters.

There is also an area of low pressure on the opposite side of Hilda, which became Tropical Depression 10-E early Sunday afternoon, battling Tropical Rainstorm 9-E to be the next named storm. During early Monday morning, Depression 10-E won that battle and was designated Tropical Storm Ignacio.

"There looks to be a small window for additional tropical development through Monday," said Douty. Then, it is possible Ignacio will get close to Hilda, which can inhibit strengthening or even lead to the loss of wind intensity.

Ignacio is anticipated to interact with Hilda and could get "sucked in" by the hurricane sometime this week, according to DaSilva. This would occur in a process called the Fujiwhara Effect.

The Fujiwhara Effect happens when two tropical systems spinning in the same direction pass close enough to each other that they begin to "dance" around a common center, according to the National Weather Service. Oftentimes, the two systems can approach each other and merge.

This phenomenon occurred earlier this year off the coast of Western Australia, when two systems, known as Seroja and Odette, interacted.


"Seroja was the dominant feature, with the system formally known as Tropical Low Odette rotating in the clockwise fashion around Seroja," AccuWeather Meteorologist Mary Gilbert said in April.

Seroja absorbed what was left of Odette in a Fujiwhara dance. Now, such an event could happen in the East Pacific basin.

"While it is possible there is a Fujiwhara interaction between the storms, I think it is too early to say this with much confidence that this specific type of interaction will happen," said Douty.

Elsewhere, another developing storm could make waves in the Pacific later this week.

This image, captured on Monday, August 2, 2021, shows Hurricane Hilda (middle), Tropical Storm Ignacio (right) and Tropical Rainstorm 9-E (left) all bunched up over the eastern Pacific Ocean. (CIRA at Colorado State/GOES-West)

"There is indication that another storm could develop west of Mexico late in the week or next weekend," said DaSilva. This storm has the potential to become a hurricane, though it is also expected to stay far off the coast, bringing few, if any, impacts to Mexico. The next name on the list of tropical storms in the eastern Pacific after Ignacio is Jimena.

Meanwhile, either Hilda or 9-E could bring an increase in moisture to Hawaii around Aug. 8 through Aug. 10, but cooler waters and wind shear mean the systems should dissipate around then, according to Douty.

While the East Pacific buzzes with activity, the Atlantic Ocean remains quiet, but not for long, according to DaSilva. The middle of the month, however, is looking to be a more active period for the Atlantic basin, and the peak of the season doesn't arrive until September, so there is plenty of time for the tropics to heat up.

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