Severe Tropical Storm Krosa (#12W) – Tropical Cyclone Advisory #15: 0000 UTC 30 July 2025

Krosa strengthens but still moving very, very slowly.

Author

Will Weaver
July 30, 2025

…Krosa strengthens but still moving very, very slowly…

Himawari-9 infrared satellite image (Weathernerds)

Current storm information:

  • Position: 29.2°N 143.3°E

  • Movement: NE at 2 knots (3 km/h)

  • Intensity: 50 knots (95 km/h)

  • Central pressure: 981 hPa

Trend:

  • Some gradual strengthening is forecast during the next 24 hours.

Watches and warnings:

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

Hazards affecting land:

  • Interests in mainland Japan should monitor the progress of Krosa. Krosa could make a close approach to southeastern Honshu this weekend, which could result in heavy rain and gusty winds, mainly east of Tokyo. U.S. military interests can get additional information from the Stars & Stripes Pacific Storm Tracker: https://www.stripes.com/theaters/asia_pacific/storm_tracker/

Discussion:

F-16 SSMIS 91GHz microwave satellite image (RAMMB/CIRA)

Krosa continues to creep northward very, very slowly as it remains in a region of very weak steering currents. However, it appears to be moving out of its large cold wake - and what a cold wake it is, as there is a small area of SSTs as cool as 24°C near the Ogasawara Islands as a result of Krosa’s lack of motion. Convection has redeveloped primarily to the north and northeast of the center with signs of a redeveloping eyewall feature, although the circulation center itself remains partially exposed. Although shear is quite low, dry air continues to plague the system, and parts of the extremely dry air mass over Japan continue to filter into the circulation. Krosa’s poleward outflow is also being enhanced by a small TUTT cell located just off the coast of Honshu. The intensity is increased to 50 kts, which is above most Dvorak and other estimates but is backed up by a RCM-1 SAR pass that found winds of about 52 kts in the northeastern quadrant of the system.

The long-lived monsoonal circulation that has dominated the Western Pacific for days now is finally breaking down, and an upper-level ridge is beginning to build over northern Japan. As this ridge strengthens, it should finally kickstart Krosa into a northwestward track toward Honshu. Environmental conditions should be conducive for some strengthening, and Krosa is forecast to strengthen fairly gradually through Saturday morning when the storm will make a very close approach to southeastern Honshu, possibly even making landfall. By this point, an approaching trough should cause Krosa to turn sharply east-northeastward and accelerate out to sea. Although the forecast goes the full 120 hours, it is looking increasingly likely that Krosa will become post-tropical on Monday and be absorbed into a large extratropical low on Tuesday.

Forecast positions and maximum winds

  • 00 hrs: 29.2°N 143.3°E – 50 kts

  • 12 hrs: 29.6°N 143.0°E – 50 kts

  • 24 hrs: 31.0°N 142.0°E – 55 kts

  • 48 hrs: 33.4°N 139.7°E – 60 kts

  • 72 hrs: 36.2°N 140.9°E – 50 kts

  • 96 hrs: 38.4°N 148.0°E – 45 kts Post-tropical/extratropical

  • 120 hrs: 40.3°N 155.8°E – 40 kts Post-tropical/extratropical

JMA forecast map