Tropical Storm Mitag (23W/ex-Mirasol) – Tropical Cyclone Advisory #6: 1200 UTC 18 September 2025

Depression becomes Tropical Storm Mitag as it continues moving northwestward toward Hong Kong.

Author

Will Weaver
September 18, 2025

…Depression becomes Tropical Storm Mitag as it continues moving northwestward toward Hong Kong…

Himawari-9 infrared satellite image (Weathernerds)

Current storm information:

  • Position: 20.3°N 117.5°E

  • Movement: NW at 10 knots (20 km/h)

  • Intensity: 35 knots (65 km/h)

  • Central pressure: 1002 hPa

Trend:

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

Watches and warnings:

  • No. 1 Standby Signal (HKO/SMG): Hong Kong and Macau

Hazards affecting land:

  • Mitag will likely produce areas of heavy rain and gusty winds along the southern coast of China, including Hong Kong and Macau, beginning on Friday evening and continuing through Sunday.

Discussion:

TD 23W has generally recovered from its passage over Luzon. The system has redeveloped a rather healthy mass of convection over and to the east of an increasingly well defined circulation center. The convection has also continued to organize into discrete bands that are evident on both conventional and microwave satellite imagery. The system is a bit lopsided due to northwesterly subsidence associated with a strong mid- to upper-level ridge situated over China, Myanmar, and Bangladesh. The intensity is increased to 35 kts based on consensus T2.5 Dvorak fixes from all the agencies and CIMSS ADT and D-PRINT estimates of 37 and 33 kts, and JMA has upgraded the system to Tropical Storm Mitag.

Although Mitag is in an outwardly favorable environment, it is not expected to strengthen much, if at all, during the next 24 hours or so. Although shear is low and SSTs are warm, Mitag will soon be moving over shallow shelf waters off the coast of China and the subsidence associated with that strong ridge is expected to persist. Therefore, no significant change in strength appears likely before Mitag makes landfall east of Hong Kong on Friday evening. After landfall, Mitag should turn westward as it gets captured by the ridge, and its small circulation should quickly spin down and dissipate by Saturday.

Forecast positions and maximum winds

  • 00 hrs: 20.3°N 117.5°E – 35 kts 

  • 12 hrs: 21.9°N 115.8°E – 35 kts

  • 24 hrs: 22.7°N 114.8°E – 35 kts inland

  • 48 hrs: 23.1°N 113.1°E – 25 kts inland

  • 72 hrs: Dissipated

JMA forecast map