Tropical Depression 23W (Mirasol) – Tropical Cyclone Advisory #2: 0000 UTC 17 September 2025

Mirasol weakens to a depression as it crosses northern Luzon

Author

Will Weaver
September 16, 2025

…Mirasol weakens to a depression as it crosses northern Luzon…

Himawari-9 visible satellite image (Weathernerds)

Current storm information:

  • Position: 16.4°N 121.8°E

  • Movement: WNW at 8 knots (15 km/h)

  • Intensity: 30 knots (55 km/h)

  • Central pressure: 1004 hPa

Trend:

  • Little change in strength is forecast during the next 24 hours.

Watches and warnings:

PAGASA wind signal map (click to enlarge)

  • TCWS #1 (Philippines): Batanes Islands, Babuyan Islands, Ilocos Norte, Apayao, Cagayan, Ilocos Sur, Abra, Kalinga, Mountain Province, Ifugao, Isabela, Nueva Vizcaya, Quirino, northern Aurora

Hazards affecting land:

  • TD 23W is likely to produce areas of heavy rainfall over portions of northeastern Luzon, as well as the Batanes and Babuyan Islands and the southern coast of Taiwan, during the next couple of days. This rainfall could cause isolated flooding in low-lying areas. For additional information, refer to products from your local weather office.

  • Interests in southern China, including Hong Kong and Macau, should monitor the progress of this system.

Discussion:

Prior to 23W/Mirasol’s landfall in Aurora at about 1920 UTC, the tropical cyclone had increased significantly in organization, and scatterometer data and automated estimates supported an increase of its intensity to 45 kts. This is backed up by microwave satellite imagery from shortly after landfall that indicated the formation of a partial eye feature. Although the eye is no longer evident on any available imagery, 23W’s circulation remains quite well defined, although some decoupling has occurred due to interaction with the Cordillera Central - the mid-level circulation is displaced to the northeast of the surface center with some convective bands flaring around it. Given how disrupted and vertically distorted 23W’s structure has become, combined with the general lack of tropical storm force observations, 23W’s intensity is lowered to 30 kts, making it a tropical depression again.

The forecast is a bit complicated because of 23W’s current structure. Most of the model guidance appears to be tracking 23W’s mid-level circulation, and their initial positions do not seem to correspond to 23W’s current position. The guidance generally suggests a straight north-northwestward track, which doesn’t seem particularly likely since the surface circulation is being deflected south of the mountains. However, once the surface circulation moves west of the mountains, it should turn northwestward and realign with the mid-level circulation as 23W moves back out over water. 23W should emerge over the western end of the Luzon Strait tonight. Once there, the environment should be conducive for steady strengthening, and 23W should become a tropical storm again on Thursday. By Friday evening, increasing shear and shallower shelf waters should put an end to any strengthening, and 23W will likely weaken to a tropical depression just inland near Hong Kong by Saturday morning and dissipate by Sunday.

Forecast positions and maximum winds

  • 00 hrs: 16.4°N 121.8°E – 30 kts inland

  • 12 hrs: 19.0°N 120.4°E – 30 kts

  • 24 hrs: 19.7°N 118.5°E – 40 kts

  • 48 hrs: 21.5°N 115.7°E – 50 kts

  • 72 hrs: 22.9°N 113.9°E – 30 kts inland

  • 96 hrs: Dissipated

JMA forecast map