Subtropical Depression 07W – Special Tropical Cyclone Advisory #1: 2100 UTC 12 July 2025

…Subtropical depression off the coast of Shanghai expected to begin moving northeastward toward South Korea and Kyushu later today…

Current storm information:

• Position: 30.8°N 123.6°E

• Movement: ENE at 7 knots (10 km/h)

• Intensity: 30 knots (55 km/h)

• Central pressure: 1002 hPa

Trend:

• Some strengthening is possible during the next 24 hours, and the system could become a subtropical storm later today.

Watches and warnings:

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

Hazards affecting land:

• The subtropical depression is likely to bring heavy rain and gusty winds to portions of Kyushu and South Korea, including Jeju Island, beginning late tonight into Monday. For additional information and possible warnings, refer to products from your local weather office.

• Additional information for U.S. military interests can be found at the Stars & Stripes Pacific Storm Tracker: https://www.stripes.com/theaters/asia_pacific/storm_tracker/

Discussion:

The “tropical depression” (invest 92W) that has been meandering off the eastern coast of China has continued to increase in organization during the past 24 hours or so. However, it has a rather broad and somewhat elongated circulation, with a broad swath of 25 to 30 kt winds located along the eastern and southern periphery. Given the system is co-located with an upper-level low centered just to the north and is producing some convective banding relatively near and to the northeast of the center, the system is being classified as a subtropical depression (a system with characteristics of both tropical and extratropical cyclones). Its initial intensity of 30 kts is based on both Oceansat-3 scatterometer data and local observations of 25 to 30 kts in the Shanghai area. The pressure of 1002 hPa is similarly based on surface observations.

SubTD 07W has begun moving toward the east-northeast along with the upper-level low currently supporting it, with steering from an upper-level trough digging down from northeastern China. As the upper-level low deepens, SubTD 07W will perform a wide loop along its outer periphery, passing south of Jeju Island tonight and making landfall east of Busan on Monday. Although SSTs are not particularly warm and shear is moderately strong, SubTD 07W could strengthen some due to baroclinic influences, and it is forecast to become a low-end subtropical storm before landfall. After landfall, 07W should gradually weaken before dissipating outright over North Korea on Tuesday night or Wednesday. It should be noted that if 07W manages to remain over water longer as suggested by some of the model guidance, it could strengthen a bit more than currently indicated, but hostile environmental conditions should still cause dissipation within the same time frame.

Forecast positions and maximum winds

• 00 hrs: 30.8°N 123.6°E – 30 kts Subtropical depression

• 12 hrs: 31.4°N 125.6°E – 35 kts Subtropical storm

• 24 hrs: 33.2°N 128.0°E – 40 kts Subtropical storm

• 48 hrs: 37.4°N 129.0°E – 30 kts Subtropical depression inland

• 72 hrs: 39.0°N 127.5°E – 30 kts Subtropical depression inland

• 96 hrs: Dissipated