Tropical Storm Co-May (11W) – Tropical Cyclone Advisory #13: 1200 UTC 29 July 2025

Co-May strengthens a little and turns northwestward. Forecast to make landfall near Shanghai late Wednesday.

Author

Will Weaver
July 29, 2025

…Co-May strengthens a little and turns northwestward… …Forecast to make landfall near Shanghai late Wednesday…

Himawari-9 shortwave infrared satellite image (Weathernerds)

Current storm information:

  • Position: 28.6°N 123.6°E

  • Movement: NW at 8 knots (15 km/h)

  • Intensity: 40 knots (75 km/h)

  • Central pressure: 990 hPa

Trend:

  • Some slight additional strengthening is possible during the next 24 hours.

Watches and warnings:

  • There are no land-based watches or warnings in effect.

Hazards affecting land:

  • NoneCo-May is likely to produce heavy rainfall and gusty winds over portions of eastern China beginning on Wednesday evening. This rainfall could cause widespread flooding. For additional information, refer to products from your local weather office.

Discussion:

Himawari-9 shortwave infrared satellite image. Note the swirl of low clouds located just southeast of the convection. (Weathernerds)

Radar data from China indicates that Co-May appears to be getting better organized. The system is showing signs of redeveloping an inner core of convection, including a partial eyewall feature. On the outside, though, Co-May appears to be a vertically tilted (sheared) system with the mid-level and low-level circulations not vertically aligned. The low-level circulation appears to be exposed to the southeast of the overcast, although the circulation itself is much better defined than it was this time yesterday. The intensity is nudged upward slightly to 40 kts, hedged between Dvorak fixes ranging from T2.0 to T3.0 and a CIMSS ADT estimate of 37 kts.

Composite radar image. Note the developing inner core feature with a ring of convection surrounding the (mid-level) center. (CyclonicWx)

The forecast is generally unchanged. Co-May is forecast to continue moving generally northwestward for the next couple of days under the influence of a rapidly decaying monsoonal circulation over eastern China and some weak ridging located to the northeast. On this track, Co-May should make landfall in the Shanghai area late Wednesday or very early Thursday. At this point, it appears the ridging will not be strong enough to cause Co-May to recurve northward and northeastward nearly as quickly as previous forecasts have shown, and the forecast now indicates dissipation after 72 hours.

Forecast positions and maximum winds

  • 00 hrs: 28.6°N 123.6°E – 40 kts

  • 12 hrs: 30.1°N 123.0°E – 45 kts

  • 24 hrs: 31.5°N 121.6°E – 45 kts

  • 48 hrs: 32.9°N 118.9°E – 35 kts inland

  • 72 hrs: 33.8°N 119.3°E – 25 kts inland

  • 96 hrs: Dissipated

JMA forecast map