Current Snapshot

The Pacific Disaster Center’s (PDC Global) Friday, September 1, 2023, Tropical Cyclone Activity Report…for the Pacific Ocean, the Indian Ocean, and adjacent Seas

Current Tropical Cyclones:

Tropical Cyclone 09W (Saola)…is located approximately 87 NM west-southwest of Hong Kong

Tropical Cyclone 10W (Haikui)…is located approximately 281 NM south-southwest of Kadena AB

Tropical Cyclone 11W (Kirogi)…is located approximately 1052 NM east-southeast of Sasebo, Japan

Northeast Pacific Ocean:

>>> Central East Pacific…

Disorganized showers and thunderstorms located over the far eastern Pacific south of the coasts of El Salvador and Guatemala are associated with a tropical wave.

Environmental conditions are forecast to be conducive for gradual development of this system during the next several days, and a tropical depression is likely to form by the middle portion of next week.

The system is forecast to move westward to west-northwestward, passing well south of the coasts of southern and southwestern Mexico.

* Formation chance through 48 hours…low…10 percent
* Formation chance through 7 days…high…80 percent

Central North Pacific…

>>> Approximately 650 miles south-southwest of Honolulu, Hawaii…

A weak area of low pressure located far south-southwest of Honolulu, Hawaii is producing disorganized showers and thunderstorms.

As this area moves northwestward, there is a short window for possible development over the next day or so before upper level conditions become unfavorable.

* Formation chance through 48 hours…low…10 percent
* Formation chance through 7 days…low…10 percent

Western Pacific, Indian Ocean and adjacent Seas:

Western Pacific…

Tropical Cyclone 09W (Saola)

According to the JTWC Warning number 38…

Sustained winds were 85 knots…with gusts to near 105 knots

Animated enhanced infrared satellite imagery shows the system has maintained a highly symmetrical and dense central convection even as the northern half has made landfall into Hong Kong and inland China; an eyewall replacement cycle has failed to transpire as the outer eyewall has mostly eroded leaving the inner eyewall intact with its well-defined but constricting 8 NM pinhole eye.

Analysis indicates a favorable environment with very warm sea surface temperatures in the South China Sea and strong radial outflow offset by moderate to strong vertical wind shear.

TY Saola will track more west-southwestward under the steering influence of the ridge to the north, passing just 12 NM south of Hong Kong over the next two hours. After 12 hours, a secondary ridge to the west will assume steering and drive the cyclone southwestward. Increasing vertical wind shear and land interaction with the eastern seaboard of China, in addition cool dry air intrusion from the Chinese interior will rapidly weaken 10W down to 45 knots by 48 hours.

After 48 hours, a more gradual erosion is expected as 09W will loop counterclockwise over Hainan Island, then track northeastward back into the South China Sea, steered by a shallow near-equatorial ridge to the south, leading to dissipation over land by 120 hours. There is a distinct possibility that 09W will dissipate before 120 hours.

Tropical Cyclone 10W (Haikui)

According to the JTWC Warning number 19…

Sustained winds were 85 knots…with gusts to near 105 knots

Animated enhanced infrared satellite imagery shows a medium-sized system that has maintained deep convective banding wrapping into a central dense overcast that has obscured a developing eye.

Analysis indicates a favorable environment with very warm sea surface temperatures and moderate equatorward outflow offset by moderate to strong vertical wind shear.

TY Haikui will continue west-northwestward Under the steering influence of the ridge to the northeast, tracking over southern Taiwan around 48 hours, cross the Taiwan Strait, then makes a secondary landfall over the Chinese eastern seaboard around 96 hours.

The favorable environment will fuel a steady intensification to a peak of 100 knots by 24 hours. Afterward, increasing vertical wind shear and later on, land interaction will gradually then rapidly erode the system down to 30 knots by 120 hours as it tracks further inland.

Tropical Cyclone 11W (Kirogi)

According to the JTWC Warning number 13…

Sustained winds were 35 knots…with gusts to near 45 knots

Tropical storm 11W continues to be sheared, with a ragged mass of deep convection displaced largely northeast of the low-level circulation center (llcc), evident in animated enhanced infrared. Total precipitable water imagery depicts a wedge of dry air entrenched across the northern side of the system, and beginning to wrap in closer to the core from the northwest.

The environment is assessed as marginally unfavorable, with warm sea surface temperatures and moderate poleward outflow offset by moderate to high vertical wind shear.

Tropical storm 11W (Kirogi) will continue tracking northwestward for the next 36 hours, along the western periphery of the steering ridge to the east. After 36 hours, the ridge is expected to extend to the west, which will turn the system west-northwestward initially, then generally westward through 120 hours.

In terms of intensity, no significant environmental changes are expected in the first 24 hours of the forecast, with supportive sea surface temperatures and robust outflow competing with persistent high vertical wind shear. The system is forecast to maintain a steady weakening trend as outflow becomes less favorable and dry air entrainment increases.

Thus, the environment will become increasingly unfavorable, and 11W is expected to begin dissipation south of Honshu before ultimately weakening below 25 knots by 96 hours as the system enters the East China Sea.