Tropical Storm Co-May (#11W) – Tropical Cyclone Advisory #15: 1200 UTC 30 July 2025

…Co-May inland over Shanghai… …Likely to become a remnant low on Thursday…

Current storm information:

• Position: 31.0°N 121.1°E

• Movement: NW at 8 knots (15 km/h)

• Intensity: 35 knots (65 km/h)

• Central pressure: 980 hPa

Trend:

• Rapid weakening is forecast during the next 24 hours, and Co-May is expected to weaken to a tropical depression on Thursday.

Discussion:

Co-May made its second and likely final landfall almost directly over Shanghai at about 0730 UTC. It is probably a good thing Co-May did not have much time over water after its previous landfall because the tropical storm had nearly formed a complete eyewall, and it is likely Co-May may have been a bit stronger than the 40 kt intensity it was given at the time. Since landfall, Co-May’s convection has more or less evaporated. Although radar indicates some fragmented bands of convection present mainly to the northwest of the center, these are weakening quite rapidly, and the circulation is quickly becoming embedded in dry air. The intensity is lowered to 35 kts, mainly based on Co-May’s decay and surface observations that show winds in the 30 to 35 kt range. The central pressure remains quite low for a system with such a low intensity, and Shanghai recently reported a pressure of 981 hPa.

Now that Co-May is rapidly losing its convection, its circulation should spin down fairly quickly as it pushes further inland over China. With dry air firmly entrenched within the circulation, Co-May will likely weaken to a tropical depression within the next few hours and degenerate into a remnant low on Thursday. It is highly unlikely the remnant low will make a second comeback, as most of the model guidance dissipates the low fairly quickly. 

Forecast positions and maximum winds

• 00 hrs: 31.0°N 121.1°E – 35 kts inland

• 12 hrs: 31.9°N 119.5°E – 25 kts inland

• 24 hrs: 32.0°N 118.2°E – 25 kts Post-tropical/remnant low inland

• 48 hrs: Dissipated