Dora Now A Tropical Storm As Unusually Long Pacific Voyage Continues

While the Atlantic Basin continues its hurricane season slumber, Hurricane (now Tropical Storm) Dora crossed the International Date Line, triggering a rare name change on its long voyage across the Pacific Ocean.

A​n abundance of dry, sinking air is currently keeping the lid on development in the tropical Atlantic Basin, despite record warm ocean water for this time of year.

S​o, let's discuss the oddity that is Dora, as well as another remnant that brought an unusual August soaking to parts of California.

A​ strange crossing prompts a name change. We’re used to seeing name changes from, say, tropical storm to hurricane. But a rare shift in nomenclature happened with Dora. Dora, once a hurricane, became a typhoon.

Hurricanes are called “typhoons” in the Western Pacific Basin, which stretches from Asia to the International Date Line, the line that separates two calendar days about 1,400 miles west of Honolulu.

H​urricane Dora wasn't a typical Pacific storm. Tropical Depression Five-E formed on July 31 a few hundred miles off Mexico's Pacific Coast. It rapidly intensified into Hurricane Dora the following day, and eventually reached Category 4 intensity.

A​s we discussed earlier this season with Hurricane Calvin, most hurricanes from the Eastern Pacific Basin weaken when they enter the Central Pacific Ocean.

T​hat's because ocean currents usually bring cooler water southward off the California coast, then southwestward to an area of the basin east of Hawaii. It's also because there's usually more dry, sinking, stable air in that area. Wind shear that can weaken and rip apart hurricanes and tropical storms also usually increases closer to Hawaii.

H​owever, Dora tracked farther south than Calvin, due to its synergy with upper-level high pressure to its north moving along with it. That kept it over warmer ocean water, as you can see in the map above, and also avoided typically stronger wind shear it would have had earlier.

A​lso, when Dora reached Cat. 4 intensity, its structure became what's known as an annular hurricane. That means it has a ring of strong convection completely surrounding its eye, but few or no outer rainbands, taking on the appearance of a truck tire or doughnut.

T​hat's important because annular tropical cyclones can wall off the negative factors such as dry air or wind shear longer. They tend to weaken slower than more conventional tropical cyclones. That appeared to be the case for a time with the rather small Hurricane Dora, though it has since lost that structure.

D​ora has already traveled about 4,800 miles since it was first dubbed it T.D. Five-E. That's about the distance between Washington D.C. and Honolulu.

T​he latest forecast from the Central Pacific Hurricane Center suggests Dora could last into early this week, but will face increased wind shear.

I​ts long voyage is unusual. As you can see in the forecast map above, Dora's track could extend another 1,300+ miles.

T​hat's a rare feat.

Five years ago, Hurricane Hector maintained hurricane strength in both the Eastern and Central Pacific basins, before crossing the International Date Line as a tropical storm.

Ironically, a​nother "Hurricane Dora" in August 1999 accomplished the same thing as Hector, but barely missed crossing the date line as a hurricane.

T​he champion of Pacific long-lasting tropical cyclones, though, was John in 1994. Over 31 days, John traveled 8,189 miles over all three Pacific basins. That's more than double the distance between Tampa, Florida, and America's northernmost city, Utqiagvik – formerly known as Barrow – in Alaska.

Once John crossed the International Date Line, it became known as a typhoon, what hurricanes are called in the Western Pacific Basin. After that it stalled, executed a hairpin loop while weakening, then tracked northeast back over the date line to become Hurricane John once again.

J​ohn appears to have been the only case in reliable modern day records of a hurricane in the Eastern Pacific and Central Pacific Basins that was also a typhoon in the Western Pacific Basin.

Dora brought indirect impacts to Hawaii. Dora passed hundreds of miles south of Hawaii, but despite that, it helped influence weather conditions in the islands.

Together with high pressure to the north, Dora enhanced the difference in pressure over the islands. That means it helped create the strong winds that fanned damaging, deadly wildfires on Maui.

A​ fizzled storm's "ghost" brought rain to Southern California. In contrast with Dora, Tropical Storm Eugene didn't last long off the Mexican coast; just over 48 hours, to be exact.

B​ut even though Eugene withered away over that cooler Pacific water we alluded to earlier, its remnant spin and moisture pushed toward Southern California.

T​hose remnants wrung out showers and isolated thunderstorms in Southern California Wednesday and Thursday. One location in Ventura County picked up just over an inch of rain, according to the National Weather Service. Rainfall in the L.A. Basin and San Diego is fairly unusual in August.

T​hese tropical remnants drawn north into the Desert Southwest are quite common in summer.

L​ast September, Kay flirted with Southern California just south of the Mexican border, but its moisture brought flooding rain to the Interstate 8 corridor.

Jonathan Erdman is a senior meteorologist at weather.com and has been an incurable weather geek since a tornado narrowly missed his childhood home in Wisconsin at age 7. Follow him on X/Twitter, Facebook and Threads.

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