Typhoon Co-May (11W/#Emong) – Tropical Cyclone Advisory #4: 0000 UTC 24 July 2025

Co-May becomes a typhoon. Additional rapid strengthening is likely before approaching northwestern Luzon.

Author

Will Weaver
July 23, 2025

…Co-May becomes a typhoon… …Additional rapid strengthening is likely before approaching northwestern Luzon…

Himawari-9 visible satellite image (Weathernerds)

Current storm information:

  • Position: 16.5°N 117.9°E

  • Movement: SSE at 5 knots (10 km/h)

  • Intensity: 70 knots (130 km/h) - Category 1

  • Central pressure: 975 hPa

Trend:

  • Additional strengthening is likely before Co-May makes landfall. Rapid weakening is forecast thereafter.

Watches and warnings:

PAGASA wind signal map (click to enlarge)

  • TCWS #3 (Philippines): Western La Union, far northwestern Pangasinan

  • TCWS #2 (Philippines): Ilocos Norte, Apayao, far northwestern and western Cagayan, Ilocos Sur, Abra, Kalinga, Mountain Province, Ifugao, eastern La Union, Benguet, western Nueva Vizcaya, northern Pangasinan

  • TCWS #1 (Philippines): Batanes Islands, Babuyan Islands, Western and central Isabela, central and eastern Nueva Vizcaya, Quirino, southern Pangasinan, northern Zambales, Tarlac, northern and central Nueva Ecija

Hazards affecting land:

  • Co-May is expected to produce extremely heavy rainfall over much of Luzon and Mindoro, particularly along the western coasts. Many of these areas have already seen rainfall of up to 300 mm. Additional rainfall of up to 350 mm is possible through Saturday before the monsoon gyre finally breaks down, and this rainfall is expected to cause widespread severe to catastrophic flooding. In addition, Co-May is expected to bring tropical storm or typhoon conditions to portions of northwestern Luzon. This is a particularly dangerous and life-threatening situation! For additional information, including rainfall and flood warnings, refer to Weather Advisories and Severe Weather Bulletins from PAGASA or products from your local weather office.

Discussion:

Himawari-9 visible satellite image (Weathernerds)

Co-May’s intensification appears to have leveled off somewhat during the past few hours. F-17 SSMIS microwave satellite imagery indicates that the eyewall has become open on its northeastern side and Co-May’s outflow has become restricted east of the center, and this seems to be due to an increase in northeasterly mid-level shear. Despite this, Co-May’s inner core remains mostly intact, and intense convective hot towers have begun wrapping around the center again. Dvorak fixes range from T4.0 to T4.5 and CIMSS ADT recently estimated 77 kts; the intensity is increased accordingly to 70 kts. JMA is showing a slightly better but still unrealistically low intensity of 50 kts.

F-17 SSMIS 91 GHz microwave satellite image

Co-May’s forecast track has been nudged westward as model guidance indicates that southwesterly inflow into Tropical Storm Francisco to the northeast will be stronger than previously indicated. Notably, the track no longer indicates landfall on northwestern Luzon. However, any slight deviation to the east of the current forecast would result in landfall. As Co-May passes by the northwestern tip of Luzon, dramatically increasing shear and the breakdown of the monsoon gyre should cause Co-May to weaken at a spectacular rate as it accelerates northeastward toward Miyakojima and Okinawa, and although the JMA forecast has a forecast point near Okinawa, it is unlikely that Co-May will be a distinct entity by then as it will have been absorbed into a broad low pressure area over the East China Sea.

Although the forecast no longer indicates landfall, Co-May is expected to pass close enough to Luzon to produce typhoon force winds along portions of its western coast. This remains a dangerous and life-threatening situation, and all necessary precautions should be taken.

Forecast positions and maximum winds

  • 00 hrs: 16.5°N 117.9°E – 70 kts

  • 12 hrs: 16.4°N 119.2°E – 85 kts

  • 24 hrs: 18.7°N 120.5°E – 80 kts

  • 48 hrs: 24.7°N 125.8°E – 45 kts 

  • 72 hrs: Dissipated

JMA forecast map