Typhoon Surigae strengthened from a modest tropical storm into a super typhoon in about three days, and it is now weakening as it curves toward the waters south of mainland Japan. As of 12:45 p.m. Japan Standard Time (JST) on Monday, Sept. 28, the Japan Meteorological Agency (JMA) still rated Surigae a "very strong" typhoon, with 10-minute sustained winds of 90 knots (104 mph), gusts to 130 knots (150 mph) and a central pressure of 955 hectopascals, according to Weathernews, which cited JMA observations.

The storm's center was about 110 kilometers (68 miles) north of Kitadaito Island in Okinawa Prefecture and moving east-northeast at about 15 km/h (9 mph). It passed well east of Okinawa's main island, but Weathernews forecast waves up to 7 meters (23 feet) across the Okinawa region, including the Daito Islands, on Monday.

The bigger question is what happens later this week. The Japan Times reported that Surigae could possibly make landfall in Japan's Tokai and Kanto regions, which include Tokyo, around Thursday, after weakening. Kanto is still recovering from Typhoon Dujuan, whose death toll rose to 14 on Monday, a week after its heavy rain struck Kanagawa and Chiba prefectures, according to Jiji Press. Forecasts differ on how close the center will come, and that uncertainty should shape how residents and travelers read any headline about Tokyo.

From Tropical Storm to Super Typhoon in Three Days

At 12:45 p.m. JST on Sept. 25, JMA data showed Surigae as a tropical storm with sustained winds of 40 knots (46 mph) and a central pressure of 1,000 hectopascals, about 715 kilometers southeast of Naha, according to an earlier Weathernews bulletin. That bulletin already forecast rapid intensification over warm tropical water, with a peak near 80 knots.

The storm exceeded that forecast, and quickly. The U.S. military's Joint Typhoon Warning Center (JTWC) upgraded Surigae to a super typhoon on Sunday night Japan time, The Japan Times reported. JTWC applies that label to storms with one-minute sustained winds of at least 130 knots (150 mph). In a summary of JTWC data, meteorologist Fred Pickhardt reported that the agency estimated Surigae jumped from 75 knots to 130 knots in 24 hours while centered about 119 nautical miles east of Okinawa. Forecasters generally treat a gain of 30 knots in 24 hours as rapid intensification, so that pace was well beyond the threshold.

The super typhoon phase was short. Storm-tracking data compiled by RainViewer show the peak at 3 a.m. JST Monday and a drop below super typhoon strength within six hours. Readers comparing numbers should note that JMA and JTWC measure differently. JMA averages winds over 10 minutes while JTWC uses one-minute averages, so JTWC figures run higher for the same storm. JMA remains the official warning authority for Japan.

Waves and Wind Across the Nansei Islands

Okinawa is not within Surigae's forecast path, but JMA still warned of high waves and violent winds there, The Japan Times reported. Weathernews forecast Okinawa-region waves of 7 meters on Monday and 5 meters (16 feet) on Tuesday, with 4-meter (13-foot) seas in the Amami region Monday. It projected sustained winds near 49 knots (56 mph) with gusts to 68 knots (78 mph) across the Okinawa region Monday, easing on Tuesday.

The forecaster also warned of lightning, violent squalls and possible tornadoes in rain bands near the storm's edge. Inter-island ferries and fishing operations face the most immediate disruption, and the small, isolated Daito Islands are the most exposed communities because the storm's core passed closest to them.

Two Forecasts for the Kanto Region

The two main sources behind this story describe the Kanto risk differently. According to The Japan Times, Surigae is expected to move east-northeast before approaching the Izu Islands and could possibly make landfall in the Tokai and Kanto regions around Thursday, by which time it will likely have weakened into a severe tropical storm that can still damage property and make travel on foot or by car difficult.

The Japan Meteorological Agency's own outlook, issued Monday afternoon, falls between those two. It said Surigae would likely move over waters south of the Shikoku and Tokai regions on Tuesday and Wednesday and travel northeast near the Izu Islands on Thursday, and that it may approach Shizuoka Prefecture and the Kanto region on Thursday if it veers north, Jiji Press reported. At 3 p.m. JST Monday, JMA placed the storm about 160 kilometers (99 miles) north-northeast of Minamidaitojima, moving east-northeast at 15 km/h.

Weathernews expected a steady weakening trend to begin Tuesday as the storm meets cooler ocean water and stronger wind shear south of Honshu. It forecast Surigae to fall to severe tropical storm strength, about 55 knots (63 mph), by 9 a.m. JST Thursday, skirt the Izu Islands that day, and become an extratropical low over the North Pacific by Saturday. That outlook describes a track over the waters south of Honshu rather than a landfall on the Kanto coast.

Both outlooks agree that Surigae will be much weaker by the time it nears the Tokyo area. The disagreement is over distance, and a center passing just offshore can still bring heavy rain to land. Japan's land ministry warned that Surigae could lead to heavy rain warnings in western and eastern Japan later this week, The Japan Times reported.

That rain would fall on saturated ground. The Kanto-Koshin region set records for September rainfall and 24-hour rainfall during Dujuan's peak on Sept. 21, and Monday was central Tokyo's 33rd straight day with precipitation, tying the longest such streak since records began in 1886, set in 2019. With rain expected to continue in the capital through Thursday, JMA said the record could be broken. Dujuan's landslides damaged hundreds of houses, and Japan Times coverage of the aftermath described a levee breach at Lake Inba in Chiba Prefecture that flooded homes and stores. About 470 households were still without water service as of Monday, The Japan Times reported.

Travelers, U.S. Connections and What to Watch

For U.S. readers, the most direct links are travel and the American military presence in Okinawa. Anyone with flights or rail plans involving Tokyo, Okinawa, or the Izu Islands late this week should check with their carriers, since typhoon-season schedule changes can come on short notice. Americans in Japan should follow JMA warnings and instructions from their local municipality, which issues evacuation information in Japan.

The greatest risk falls on households near steep slopes and rivers in Kanto areas that flooded or slid during Dujuan, residents still without water service, and island communities facing high surf. Warning signs of landslides include muddy or suddenly changing streams, new cracks in slopes and small rockfalls, and anyone who sees them should move away and follow local evacuation guidance.

JMA updates its typhoon track forecasts regularly, and its cone of probable positions widens several days out, which is why no Kanto landfall time should be treated as fixed. The next key signal will be whether JMA's midweek forecasts shift the track toward the coast or keep it offshore. The latest data show a storm past its peak, but a rain-soaked Tokyo region cannot rule out another round of heavy rain before the week ends.

What Readers Want to Know

Is Surigae still a super typhoon?

No. Storm-tracking data show Surigae peaked as a super typhoon early Monday Japan time, and dropped below that threshold within hours. JMA still classified it as a very strong typhoon as of 12:45 p.m. JST Monday.

Will Surigae hit Tokyo?

It is not certain. JMA said Monday that Surigae would likely pass near the Izu Islands on Thursday and may approach Shizuoka and the Kanto region if it veers north. The Japan Times reported a possible Tokai or Kanto landfall as a severe tropical storm, while Weathernews forecast a track south of Honshu.

Why do JMA and JTWC report different wind speeds?

JMA averages sustained winds over 10 minutes, while JTWC uses one-minute averages. The one-minute method produces higher numbers for the same storm.

Is Okinawa in danger?

Surigae's center passed well east of Okinawa's main island, but JMA warned of high waves and violent winds. Weathernews forecast waves up to 7 meters in the Okinawa region Monday.

Why is Kanto especially vulnerable right now?

Typhoon Dujuan brought record September rainfall to the Kanto-Koshin region, and its death toll rose to 14 as of Monday. Soil remains saturated, and Monday marked Tokyo's 33rd straight day of rain.

What should travelers do?

Travelers with plans involving Tokyo, Okinawa, or the Izu Islands late this week should check with airlines and rail operators and follow JMA and local government guidance.

When will Surigae lose its tropical characteristics?

Weathernews expects Surigae to become an extratropical low over the North Pacific by Saturday, Oct. 3.