A forecast that comes in stronger than itself is a particular kind of morning. Through the weekend this storm was read as a weakening system whose wind was easing on the way in — the danger, every desk agreed, would be the rain. Both halves turned out to be true at once. By 10 AM local the analysed centre had deepened to 960 hPa, with maximum sustained winds near 40 m/s on a ten-minute averaging period and gusts near 55 m/s, described as large and strong about 100 km west-south-west of Hachijojima. The averaging period is part of the figure and is not converted onto anybody else's scale here; a satellite cross-check read three hours earlier ran lower on wind, so the intensity is carried as a range rather than a point. The track, which is the part the decisions hang on, held exactly.
The water is not a forecast any more. Izu Oshima logged 426.5 mm in 24 hours, with 58 mm inside a single hour, and more than 300 mm has landed at several Pacific-coast sites since Saturday. That is falling onto ground that came into this window on roughly two weeks of record rain, and saturated ground is a different instrument entirely: it converts rainfall into runoff and slope failure at a far lower threshold than dry ground does. Which is why the operational picture is a level-five landslide warning on the northern Izu chain and level four across Kanto rather than a wind bulletin. The storm passes nearest the Izu Islands early this afternoon, comes closest to Kanto this evening, tracks offshore east of the Boso coast and goes extratropical about Tuesday — and its danger stays in the hillsides after it leaves.
What the lead time bought is worth stating plainly, because it is the whole argument. At least 275 flights were cancelled — 120 domestic and 15 international at one carrier, 140 domestic at another — before the water arrived rather than during it. Rail was suspended on the same clock. A games show gave up its final day and an Asian Games equestrian programme was postponed, both called early. More than 4,000 homes in Chiba are without power and crews are working access on slopes under a landslide warning. No casualties have been reported at the hour this page was compiled, and that sentence is a finding and not a guarantee — a level-five warning means the hazard is still live tonight. A holiday weekend lost its plans instead of its people, days in advance, on a storm that then came in harder than the guidance said. (Handled with care.)
THE RECORD
7 turning points on record since Sep 15.
Sep 21cresting → peak
Sep 20peak → cresting
Sep 19cresting → peak
Sep 18building → cresting
Sep 17↑ firmed
Sep 16emerging → building · intensified sharply
Sep 15appeared, emerging
THE FACTS
THE RAIN IS THE MEASUREMENT; THE WIND IS A RANGE426.5 mm in 24 hours on Izu Oshima with a 58 mm hour is an observation. The intensity is not: the relayed analysis reads 960 hPa and 40 m/s sustained on a ten-minute average, while a satellite cross-check three hours earlier read nearer 120 km/h sustained. Both are printed, neither is merged into the other, and the decision-useful half — track and rainfall — is the well-corroborated half.
WHY SATURATED GROUND CHANGES THE ANSWEREastern Japan came into this window on roughly two weeks of record rain. Saturated ground converts rainfall into runoff and slope failure at a far lower threshold than dry ground, which is why the live products are a level-five landslide warning on the northern Izu chain and level four across Kanto rather than a wind story. Antecedent wetness, not storm total, is the number that decides tonight.
WHAT THE LEAD TIME BOUGHTAt least 275 flights cancelled — 120 domestic plus 15 international at one carrier, 140 domestic at another — rail suspended, a games show's final day cancelled, the Asian Games equestrian programme postponed, and more than 4,000 Chiba homes without power. Every cancellation was made ahead of the water. No casualties reported at the hour of compilation. (Handled with care.)
AND ELSEWHERE — A TROPICAL STORM WITH A MAJOR-HURRICANE CEILINGOff south-west Mexico a 40-mph tropical storm about 270 miles south of Manzanillo is forecast to rapidly intensify into a Category-4 major hurricane inside about 72 hours, with the south-west coast told to monitor; a second storm becomes a hurricane over open water with no land threat; a new area near the Gulf of Tehuantepec holds 30 percent over seven days and a disturbance east-south-east of Hawaii has risen to about 70 percent.
AND ELSEWHERE — A RED ALERT OVER 699 BRAZILIAN MUNICIPALITIESSouthern Brazil escalated rather than eased: a red alert over about 699 municipalities across Rio Grande do Sul, Santa Catarina and Parana for rain above 100 mm a day, gusts past 100 km/h, hail and a tornado risk, with the coastal cyclone at its peak — and Argentina opened the first day of spring under an orange severe-storm alert over Buenos Aires.
WHO IT TOUCHES
Public safetyfive warning systems live at once, and the distance between the warning and the water is different in every one
Aviationat least 275 flights already cancelled on a holiday weekend, with three more boards to buffer
Maritimea fishing fleet with a 72-hour window, an island ferry network inside a transitioning typhoon, and a coastal wind pulse firming to about 80 km/h
Supply chainsrail suspended through a holiday weekend, a Rhine at 16.0 cm, and a coast that may lose its ports inside three days
Energymore than 4,000 homes already dark, and three grids facing wind, hail or flood inside the day
Eventsa games show's final day and an equestrian programme already cancelled, and a spring holiday under an orange storm alert
CONNECTED
The hazard is the soil, not the rainfall total — two boards on opposite sides of the planet where ordinary rain is doing extraordinary work.
WHAT THEY'RE SAYING
searched 34 vetted voices and the open field — nothing said about this system cleared the screen.
THE ATMOSPHERE TODAY · EVENT← TODAY'S COVER