Typhoon Ragasa (24W/Nando) – Tropical Cyclone Advisory #8: 0000 UTC 21 September 2025

…Extremely dangerous Category 4 Ragasa continues to intensify and could become a Category 5 super typhoon on Monday… …Signal #2 hoisted for portions of northern Luzon…

Current storm information:

• Position: 17.9°N 127.0°E

• Movement: WNW at 8 knots (15 km/h)

• Intensity: 120 knots (220 km/h) [Category 4] 

• Central pressure: 933 hPa

Trend:

• Additional rapid intensification is expected during the next 24 hours and Ragasa could become a Category 5 super typhoon on Monday.

Discussion:

Ragasa is continuing to rapidly intensify this morning. The central dense overcast has expanded since the previous advisory, consisting of a nearly symmetric ring of intense convection surrounding a small, well-defined, and clear eye feature. In addition, Ragasa continues to sport impressive radial outflow in all quadrants, Microwave satellite imagery from GMI and GCOM-W1 continues to indicate the presence of concentric eyewalls, and the inner eyewall appears to be open on its southeastern side. This may be an indication that an eyewall replacement cycle is imminent, and in fact the CIMSS MPERC eyewall replacement index indicates an 84% chance of an eyewall replacement cycle. Dvorak estimates range from T6.0 to T6.5 while CIMSS ADT, D-PRINT, and SATCON estimates range from 119 to 127 kts. The intensity is therefore increased to a potentially conservative 120 kts.

The track forecast has been nudged slightly to the south of the previous one. Model guidance has come into better agreement and there is much less spread in the short-term portion of the forecast, but unfortunately this agreement is on a track closer to northern mainland Luzon. The intensity forecast, meanwhile, depends on whether an eyewall replacement cycle occurs and how quickly it completes. The HWRF model, which tends to have a good handle on eyewall replacement cycles, suggests this process will be fairly quick and strengthens Ragasa to Category 5 status. Given that the environment remains exquisitely favorable for strengthening, this forecast assumes that will be the case, and Ragasa is forecast to peak at 140 kts on Monday as it enters the Luzon Strait. Some fluctuations in intensity are likely on Monday and Tuesday due to inner core dynamics and the potential for land interaction (especially if the forecast track continues to shift southward). By Tuesday, increasing shear and interaction with a northeasterly gap wind event in the Taiwan Strait should induce a final weakening trend, but Ragasa is expected to remain a very intense typhoon as it passes just south of Hong Kong and Macau on Wednesday. Ragasa should turn west-southwestward and move across the Leizhou Peninsula on Thursday before making its final landfall in northern Vietnam on Friday.

The current forecast track will likely result in potentially catastrophic typhoon conditions in the Batanes and Babuyan Islands on Monday. In addition, tropical storm conditions are likely along the northern coast of mainland Luzon and the southern coast of Taiwan. Higher elevations on Taiwan could see typhoon force winds. Typhoon conditions cannot yet be ruled out for the northern coast of mainland Luzon, as well. It is absolutely imperative that preparations to protect life and property be rushed to completion.

Forecast positions and maximum winds

• 00 hrs: 17.9°N 127.0°E – 120 kts

• 12 hrs: 18.6°N 125.5°E – 130 kts

• 24 hrs: 19.5°N 123.1°E – 140 kts

• 48 hrs: 20.3°N 118.1°E – 135 kts

• 72 hrs: 21.4°N 113.6°E – 115 kts

• 96 hrs: 21.0°N 108.7°E – 80 kts

• 120 hrs: 20.4°N 105.3°E – 45 kts inland