An area of disturbed weather developed within the monsoon trough, located over the East China Sea, on August 4.

The tropical storm lashed the Japanese archipelago with heavy rains, strong winds, and waves up to 7.9 m (26 ft) high.

Tropical Storm Winona originated from a monsoon trough that was displaced 550 km (340 mi) north of its climatological position.

[1] An area of enhanced convection developed within the monsoon trough in the East China Sea around 00:00 UTC on August 4.

Six hours later, the Joint Typhoon Warning Center (JTWC) started tracking the system as a weak low-pressure area developed.

Following a Dvorak classification of T1.0/50 km/h (30 mph), the JTWC issued a Tropical Cyclone Formation Alert (TCFA) at 11:00 UTC on August 5.

[1] The depression initially moved northeast,[5] skirting past the southern tip of Kyushu,[6] only to turn southeast under the influence of the monsoonal flow.

By 00:00 UTC on August 8, Winona abruptly turned north in response to a building ridge to its southeast.

[1] At noon on August 9, the JMA estimated that Winona peaked in intensity with winds of 115 km/h (70 mph) and a barometric pressure of 975 mbar (28.8 inHg).

After landfall, it began to accelerate northeastward and by 12:00 UTC, Winona was embedded in the mid-latitude westerlies and started a transition into an extratropical cyclone.

[2] Tropical Storm Winona brought strong winds and heavy rains to the Japanese archipelago.

[12] Due to stormy weather, more than 60 scheduled domestic flights between Tokyo and western Japan were delayed or cancelled.

River embankments were breached in 710 locations while 221 ha (550 acres) of arable land was damaged, totaling 89.5 million yen ($617,000 USD).

[29] In Ibaraki Prefecture, the storm dropped heavy rainfall, which resulted in four downed power lines, while one individual was injured.

[23] Two people were hurt, a 56-year-old fractured his leg and a 78-year-old female fell due to strong winds, six embankments were breached, and thirty-two roads sustained damage.

[20] The capital city of Tokyo was lashed with strong winds and heavy rain for several hours, with damage estimated at 34.9 million yen ($241,000 USD).