Typhoon Dujuan shut Yokohama for 45 hours, the backlog sailed within four days, and the September customs flash still rose.

Why these three series belong together

A typhoon becomes an economic story only if cargo is lost rather than late. Three public series test which Dujuan was: daily rain at the Japan Meteorological Agency's Yokohama station, daily port calls estimated by IMF PortWatch from ship positions, and the tonnage PortWatch estimates was loaded on container ships for export. Customs values for vehicles, the port's largest export, give the monthly check.

What the sky did

The station recorded 117.0 mm on 20 September [F1] and 223.0 mm on 21 September [F2], the wettest day since July. That day's highest ten-minute mean wind, 13.7 m/s, passed the 10 m/s at which Keihin port gantry cranes stop work. The peak gust, 21.1 m/s [F3], is a separate measure: the rules are written for ten-minute means, and the gust stayed below the 30 m/s at which cranes must be lashed. Rain alone does not shut the port: 116.5 mm on Sunday 6 September [F28] came with 27 calls [F29].

What the port did

PortWatch counted 10 calls on 19 September [F4], 3 on 20 September [F5] and 9 on 21 September [F6], against 36.3 a day over 1 July to 16 October [F10]. Container exports went from 10,678 t [F18] to zero [F11] and 14,573 t [F12]. Then the queue drained: 37 calls [F7], 49 [F8], 61 on 24 September [F9], the window's high, and 35 on 25 September [F30]. Container exports reached 115,333 t on 22 September [F13], then 56,279 t [F15], 62,163 t [F16] and 65,256 t [F17]; measured against the window's daily mean [F14], those four days recovered about 1.7 times the closure's shortfall. Car-carrier calls went from zero on 19 to 21 September to eight and ten, against about four a day before. September container exports, 1,127,052 t, topped August's 1,122,720 t.

What the customs flash shows

Yokohama Customs' September flash, released on 21 October, puts the port's automobile exports at 173.1 billion yen, up 9.1 percent on a year earlier, on 70,364 vehicles, down 5.7 percent; trucks fell 14.0 percent, passenger cars 4.0. National units fell 0.5 percent, a gap of 5.2 points, inside the 2026 range without typhoons, from 11.6 points below in May to 12.7 above in August. The wider HS 87 series, with parts and motorcycles, ran from 157.2 billion yen in January [F20] to 223.5 billion in June [F21], 220.8 billion in August [F22]; September is due about 30 October.

The mechanism, and what else could explain it

Hypothesis · The series support a shift. Cranes stopped, ships left their berths, and the port lost 45 hours, about a quarter of a week; with Tokyo shut by the same rain and Nagoya a day's trucking away, cargo waited and sailed within four days. Japan records an export on its ship's departure day, so a lot that sailed on 24 rather than 21 September is a September export either way.

Hypothesis · Three other explanations stay open. The closure fell on a weekend and three public holidays, and holidays can lower calls: 23 on 11 August [F23], though 44 on 20 July [F24]. The 115,333 t could partly be a payload-model artefact, although container calls that day were above usual. And the truck-led fall in vehicle units looks more like demand and model mix than the storm.

Who sits on the chain

Evidenced: the terminal companies (YKIP, Yokohama Port Megaterminal, Nissin), the carriers listed at the container berths (Maersk, CMA CGM, ONE, Hapag-Lloyd, MSC, Evergreen, COSCO), the car-carrier lines NYK and K Line at Daikoku, and Nissan, which loads at its own Honmoku wharf. Their place on the chain is documented; what each paid is not.

Hypothesis · Deduced: Isuzu, whose Fujisawa plant builds trucks in Yokohama's hinterland, and Isuzu Australia as importer. Tokyo's terminals and Nagoya are competitors, but Tokyo counted 2 calls on 20 September and Nagoya's record September continued a rise visible since June. No beneficiary was found: every alternative gateway closed on the same days.

A conditional sensitivity, not a forecast

Scenario · Suppose an exporter collected an empty container just as the port closed. Under Hapag-Lloyd's Japan export tariff it had 5 days of detention free time, holidays excluded; 1.875 days of closure and an assumed 1.5 days of waiting would leave 1.6 days. Only a box with no free time left would pay, at 4,000 yen a day for a 40-foot box, about 13,500 yen for the 3.4 days. On this arithmetic the delay cost sat with the carriers' ship time.

What would change this reading

Hypothesis · The October Yokohama flash, due about 19 November, will show whether units rebound, meaning lots slipped into October, or stay down, pointing to demand. The HS 8703 unit table will say whether the fall is Yokohama's alone. PortWatch will show whether November has a non-holiday day below 15 calls. The two readings differ on where that threshold sits: below 29 calls, November 2025's lowest day, was crossed in seven of the last eight months without a closure; below 15, only on the three closure days and 31 December 2025. The hypotheses use 15.