Severe Tropical Storm Krosa (12W) – Tropical Cyclone Advisory #17: 1200 UTC 31 July 2025

Krosa drifting north-northwestward with no change in strength.

Author

Will Weaver
July 31, 2025

…Krosa drifting north-northwestward with no change in strength…

Replace this image with a current satellite image of the storm (Source)

Current storm information:

  • Position: 31.4°N 142.5°E

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

  • Intensity: 50 knots (95 km/h)

  • Central pressure: 982 hPa

Trend:

  • Fluctuations in intensity are possible during the next 24 hours.

Watches and warnings:

  • Yokosuka Naval Base is under TCCOR 4.

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:

RCM-1 Synthetic Aperture Radar image, showing a well defined ring of 50 to 55 knot winds surrounding the relatively calm (deep blue) center

Krosa is certainly not winning any beauty pageants tonight. The system once again has a very disheveled appearance, consisting of a ring of fragmented convective bands surrounding the circulation center. While an eye-like feature appears to be present, it too is quite fragmented and probably does not qualify as a true eye. Despite Krosa’s appearance - which is resulting in rather unimpressive automated estimates and Dvorak fixes - recent SAR passes from the RCM-1 and Sentinel-1 satellites indicate the system is producing a tight ring of 50 to 55 kt winds, mainly to the north and east of the center. The intensity is therefore held at 50 kts.

Krosa has drifted back into the large cold wake it left behind while it was quasi-stationary, and this is why its convection has become so ragged. A deep-layered trough currently located over Japan should finally kickstart Krosa into motion later tonight. Although conditions seem to be favorable for strengthening with warm SSTs and low shear, dry air entrained within the system will likely preclude the system from strengthening much during the next couple of days. Krosa will make its closest approach to Honshu late Friday night before turning sharply east-northeastward as it rounds the periphery of a subtropical ridge located to the southeast. By Monday, Krosa should cross the northern edge of 26°C SSTs and become entangled within a frontal system, which should result in Krosa becoming post-tropical by Tuesday.

Forecast positions and maximum winds

  • 00 hrs: 31.4°N 142.5°E – 50 kts

  • 12 hrs: 32.7°N 142.0°E – 55 kts

  • 24 hrs: 34.1°N 141.2°E – 55 kts

  • 48 hrs: 37.1°N 145.0°E – 55 kts

  • 72 hrs: 38.7°N 154.2°E – 50 kts

  • 96 hrs: 40.5°N 160.1°E – 40 kts Post-tropical/extratropical

  • 120 hrs: 41.2°N 164.6°E – 35 kts Post-tropical/extratropical

JMA forecast map