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Super Typhoon Haishen to be one of the most intense storms on record for Japan, South Korea

The storm currently exhibits a 36-mile-wide eye, surrounded by towering thunderstorms.

Infrared satellite image of Super Typhoon Haishen on Sept. 4. (CIRA/RAMMB)
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Super Typhoon Haishen is roiling the unusually warm waters of the Western Pacific Ocean, having reached the equivalent of high-end Category 4 intensity, with 155 mph maximum sustained winds. The storm rapidly intensified on Thursday Eastern time, vaulting from Category 2 to super typhoon status with sustained winds of 150 mph or greater in about 24 hours.

The storm is forecast to remain at the cusp of Category 5 intensity on Friday and stay at super typhoon strength, with sustained winds of 150 mph or higher, through at least Saturday.

Super Typhoon Haishen is poised to strike the same areas as Typhoon Maysak, which hit South Korea early Thursday local time, to become the second typhoon to make landfall there and in southwestern Japan in just one week. The back-to-back typhoon strikes may worsen the damage, since infrastructure has been weakened by strong winds, heavy rains and storm-surge flooding, only to be hit again.

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In fact, assuming that Super Typhoon Haishen makes landfall in South Korea this weekend as a Category 2 storm or greater, it would become only the seventh storm to do so on record there. It would also be the fifth typhoon to strike there this season, which would be a new record, according to NHK World meteorologist Sayaka Mori as well as a historical storm database maintained by the National Oceanic and Atmospheric Administration.

The storm currently exhibits a 36-mile-wide eye, surrounded by towering thunderstorms, which is where its most powerful winds and heaviest rains are located. According to the Joint Typhoon Warning Center (JTWC), it is expected to undergo an eyewall replacement cycle during the next day or two. This is a process that takes place in the most intense typhoons and hurricanes and temporarily weakens a storm. Once this cycle is completed and the eyewall is fully rebuilt, the storm can ramp its intensity back up.

The Japan Meteorological Agency (JMA) predicts that Haishen will pass across the country’s southwestern islands on Sunday local time as a “very strong” to “violent” typhoon, which are the two highest categories on its storm rating scale.

The JTWC forecast shows the potential for a direct hit on the island of Amami Oshima in southwestern Japan.

In fact, should Haishen weaken only slightly until it encounters these islands, it’s possible that Haishen will make a run at the all-time record for the lowest central pressure recorded in a storm striking Japan since record-keeping began there in 1951, Mori wrote. In general, the lower the pressure, the stronger the storm.

The storm is moving over unusually warm waters of around 88 degrees, and the warmth extends deep within the water column, making for high amounts of ocean heat content — a major determinant of tropical cyclone potential intensity. So far, the storm has avoided moving over the cool water wake left behind by the previous storms this season.

According to the JTWC, the storm is unlikely to weaken significantly until it begins to move over slightly cooler waters and encounters stronger upper-level winds that could alter its structure, potentially causing a slackening to the surface winds this weekend.

After the storm’s potentially damaging encounter with Japan, the current forecast calls for a landfall near Busan, South Korea, the country’s second-largest city and the world’s sixth-largest port. Busan was hard-hit by Typhoon Maysak earlier this week, which would make another direct hit especially dangerous.

Forecasters at the JTWC cautioned that Haishen may come ashore farther to the west in South Korea than currently forecast, depending on how surrounding weather systems evolve.