Tropical Storm Co-May (11W) – Tropical Cyclone Advisory #10: 0000 UTC 28 July 2025

Center of Co-May stalls out over Okinawa.

Author

Will Weaver
July 27, 2025

…Center of Co-May stalls out over Okinawa…

Himawari-9 visible satellite image (Weathernerds)

Current storm information:

  • Position: 26.2°N 128.0°E

  • Movement: Nearly stationary

  • Intensity: 40 knots (75 km/h)

  • Central pressure: 992 hPa

Trend:

  • Some strengthening is possible during the next 24 hours.

Watches and warnings:

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

Hazards affecting land:

  • Co-May is likely to produce heavy rainfall and gusty winds over portions of the Ryukyu Islands, including Okinawa, beginning on later today. U.S. military interests in Okinawa can get additional information from the Stars & Stripes Pacific Storm Tracker: https://www.stripes.com/theaters/asia_pacific/storm_tracker/

Discussion:

Himawari-9 visible satellite image (Weathernerds)

Co-May has become poorly organized again. Its circulation center has become fully exposed again well to the west of a large band of convection well to the east of Okinawa. The circulation itself has also become elongated from west to east, likely due to the flattening out of the monsoon gyre. Scatterometer data also indicates that the wind field is elongated, with the strongest winds located mainly to the north and northeast of the center. There is also a great deal of dry air entrained within the circulation, which is probably preventing new convection from developing over the center. Although Dvorak fixes are not particularly impressed with Co-May, the Oceansat-3 data indicates that the storm is still producing winds of 35 to 40 kts, so the intensity remains 40 kts.

F-17 SSMIS 91GHz microwave image (RAMMB/CIRA)

Co-May is located in the middle of the large monsoonal circulation centered west of Okinawa, which is devoid of steering currents, which is why Co-May has become quasi-stationary. As the monsoonal circulation breaks down, Co-May should resume a west-northwestward motion into the East China Sea as subtropical ridging takes over as the main steering mechanism. The environment ahead appears favorable for strengthening, and some gradual intensification appears likely before Co-May makes landfall in Eastern China on Wednesday. After landfall, Co-May should quickly weaken, becoming a tropical depression by Thursday and dissipating shortly after.

It should be noted that some model guidance regenerates Co-May yet again as its remnants move out over the southern Yellow Sea on Friday. This appears unlikely, but it already came back from the dead once before, so who knows?

Forecast positions and maximum winds

  • 00 hrs: 26.2°N 128.0°E – 40 kts

  • 12 hrs: 27.1°N 126.2°E – 45 kts

  • 24 hrs: 27.8°N 123.9°E – 50 kts

  • 48 hrs: 29.6°N 121.5°E – 45 kts inland

  • 72 hrs: 31.6°N 120.1°E – 35 kts inland

  • 96 hrs: 32.5°N 119.5°E – 25 kts inland

  • 120 hrs: 33.9°N 118.9°E – 25 kts inland

JMA forecast map