Tropical Storm Dujuan — named, recurved, and aimed at eastern Japan

On Sunday it was an unnamed area of convection with a number instead of a name. This morning the joint typhoon centre's 00Z warning puts Tropical Storm Dujuan at 19.0 N 150.4 E, about 449 nautical miles north-east of Guam, with maximum sustained winds of 50 knots gusting to 65 and a north-north-east track at 15 knots. It is forecast to peak near 70 knots — a marginal typhoon — Friday into Saturday, then weaken and go extratropical near 40 N by Monday. Japan's own agency classifies it a Severe Tropical Storm; the Philippine service logs it outside its area of responsibility. And it recurved clean of the Marianas: there are no watches for Guam, Saipan, Tinian or Rota, so the islands that spent three days inside the forecast cone are not the story. Four days, invest to named storm to a target — the ramp did exactly what it was carried to do.

The story is the ground it is aimed at. Tokyo desks report that Kantō-Kōshin has taken about 365 percent of its normal rainfall since September 1, with the least sunshine in records kept since 1961 — a newspaper figure rather than an agency product, and marked reported here for that reason. Two and a half weeks of rain with almost no sun to dry it leaves a hillside that has stopped absorbing and a drainage system with no headroom. Dujuan's rain reaches Ogasawara on Saturday, the Izu Islands on Sunday, and eastern Japan including Tokyo behind them — across Silver Week, the stretch when the country is travelling. A marginal typhoon is an ordinary storm; that is the honest description of its wind field. An ordinary storm's rain onto that particular ground is not an ordinary rainfall event, and the difference is not in the storm at all.

It is also worth saying plainly what is and is not knowable this morning. The apparatus that watched an unnamed invest become a named storm on a clean four-day ramp can also tell you what the ground beneath its forecast path has been doing for a fortnight, and the two readings together are the actual forecast — a modest storm read against a saturated antecedent. What a cross-agency aggregator cannot carry is that second reading: the board rates Dujuan green, which is true and nearly useless, because it is counting people exposed to Category-1 wind at scan time and the hazard here is rain on loaded soil. Nobody can say this morning what the weekend costs any particular household in Izu or Kantō, and this page will not pretend to — there is no toll to print, because nothing has happened yet. What is on the record today is a track, a peak, a holiday, and two and a half weeks of accumulated rain. Three of those four were knowable before the storm had a name. (Handled with care.)

2 turning points on record since Sep 15.

The forecast committed in one ocean and let go in the other, on the same morning — an unnamed invest became a named storm with a Tokyo target on a clean four-day ramp, while an Upper-Midwest event this page re-dated for three consecutive editions simply washed out and the water that killed people fell a continent-width away from where the story had been living.

In both of these the storm is the smaller half of the problem — Dujuan's ordinary rain is dangerous because Kantō-Kōshin has taken about 365 percent of normal since Sep 1, and southern Vietnam's five-day spell starts on a region whose northern half flooded overnight.