Tropical Depression 01W - Tropical Cyclone Advisory #2, 1200 UTC 6/10/25

…Tropical Depression 01W forecast to bring heavy rainfall to Hainan Island beginning on Thursday…

Current storm information:

• Position: 15.4°N 113.7°E

• Movement: WNW at 6 knots (10 km/h)

• Intensity: 30 knots (55 km/h)

• Central pressure: 996 hPa

Trend:

• Some strengthening is forecast during the next 24 hours, and the depression will likely become a tropical storm later tonight or tomorrow.

Watches and warnings:

• No land-based watches or warnings are currently in effect, although Hong Kong and Macau will both be issuing the No. 1 standby signal early Wednesday morning.

Hazards affecting land:

• The depression is likely to produce very heavy rainfall over portions of Hainan Island beginning on Thursday. This rainfall is expected to spread over southern China, including Macau and Hong Kong, by the end of the week and over the weekend. Since 01W will be relatively slow-moving, this rainfall is likely to cause widespread severe flooding. For further information, including possible warnings, refer to products from your local weather office.

Discussion:

The tropical depression, now designated Tropical Depression 01W by JTWC, has gotten somewhat better organized since the previous advisory, although its circulation is still struggling to become better defined. Satellite imagery suggests that the low-level and mid-level circulations are not vertically aligned, with a much broader swirl of low clouds located to the northeast of the estimated center position. Despite this, the convection has become better organized with discrete bands present to the south and southwest of the estimated center location. Scatterometer data suggests that TD 01W still has a fairly broad wind field, with a large swath of 25 to 30 kt winds present in the western and northern semicircles and lighter winds to the southeast. The intensity is held at 30 kts based on this data, and is ahead of a blend of available T1.0 to T2.0 Dvorak estimates from PGTW and RJTD.

Most of the model guidance has shifted westward from the previous advisory time, showing a slightly delayed turn toward the northwest as subtropical ridging builds in to the northeast. This has resulted in the forecast track being nudged somewhat to the west. 01W is now forecast to pass over Hainan Island on Friday before briefly emerging over the Gulf of Tonkin on Saturday and making a final landfall in southern China on Sunday. The environment appears to be favorable for strengthening, and assuming 01W’s circulation is able to consolidate, it is forecast to strengthen at a steady rate and likely reach severe tropical storm status as it makes landfall on Hainan. By Saturday, increasing shear and interaction with land will likely offset the very warm SSTs in the Gulf of Tonkin, resulting in a gradual weakening trend that will continue through the end of the forecast period. At the end of the forecast period on Sunday, 01W is expected to be undergoing extratropical transition as it interacts with the meiyu/tsuyu front over southeastern China. This interaction could result in 01W remaining at tropical storm strength longer than one would typically expect after landfall.

Forecast positions and maximum winds

00 hrs: 15.4°N 113.7°E - 30 kts

12 hrs: 15.6°N 112.5°E - 35 kts

24 hrs: 16.0°N 111.5°E - 45 kts

48 hrs: 17.2°N 110.0°E - 55 kts

72 hrs: 19.8°N 109.0°E - 45 kts 

96 hrs: 22.0°N 109.9°E - 35 kts (inland)

120 hrs: 24.5°N 114.0°E - 35 kts Becoming extratropical (inland)