Tropical Cyclone 11E / Tropical Cyclone 10W (Haikui) / Tropical Cyclone 11W (Kirogi) / Invest 99W
Monday, September 4, 2023

Current Snapshot

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By PDC’s Senior Weather
Specialist Glenn James

The Pacific Disaster Center’s (PDC Global) Monday, September 4, 2023, Tropical Cyclone Activity Report…for the Pacific Ocean, the Indian Ocean, and adjacent Seas

Current Tropical Cyclones:

Tropical Cyclone 11E…is located approximately 760 NM south-southeast of the southern tip of Baja California

Tropical Cyclone 10W (Haikui)…is located approximately 191 NM east-northeast of Hong Kong – Final Warning

Tropical Cyclone 11W (Kirogi)…is located approximately 227 NM south-southeast of Iwakuni, Japan – Final Warning


Northeast Pacific Ocean:

Tropical Cyclone 11E


According to the NHC Advisory number 2

The depression is moving toward the west near 12 mph (19 km/h). A generally west-northwestward motion is expected during the next several days. The system is forecast to pass well south and west of Mexico.

Maximum sustained winds are near 35 mph (55 km/h) with higher gusts.
Some gradual strengthening is expected during the next day or so,
followed by more significant strengthening through midweek. The system is forecast to become a hurricane by Wednesday night.

Central North Pacific…

There are no tropical cyclones, nor any areas of disturbed weather under investigation by the CPHC.


Western Pacific, Indian Ocean and adjacent Seas:

Western Pacific…

Tropical Cyclone 10W (Haikui) – Final Warning

According to the JTWC Warning number 28…

Sustained winds were 30 knots…with gusts to near 40 knots

Animated enhanced infrared satellite imagery depicts a system that is struggling to survive. After moving away from the coast of Taiwan and into the relatively open waters of the Taiwan Strait, the structure of tropical storm 10W (Haikui) has become increasingly disorganized. Animated radar imagery showed a clear cut center six hours ago, but that has now eroded to the point where it is difficult to locate. Likewise in the best available visible satellite imagery. The most recent microwave image showed a sharply tilted vortex with the low-level rotation hanging back while the upper-levels moved quickly off to the west.

The environment remains favorable overall, but the system does not have enough time remaining over water to recover from the terrain induced disruptions from Taiwan and will in any course begin to be disrupted by terrain influences from the Chinese coast in short order.

TS 10W is forecast to continue tracking slowly to the west-northwest along the southwest side of the steering ridge for the next 12 to 18 hours. Uncertainty in the initial position and thus track speed, leads to relatively low confidence in the timing of the expected landfall along the Chinese coast, though still expected within the next 12 hours.

The system is not likely to be able to intensify in the tight confines of the Taiwan Strait, for while environmental conditions remain conducive, disruption of the low-level inflow and vortex tilt will inhibit consolidation of the inner core and convective organization. The system will make landfall as a weak tropical storm, between 40-45 knots.

After landfall, the system will turn towards the west as a strong, deep-layer anticyclone develops over central China and assumes the steering role. Frictional effects will steadily weaken the remnants of TS 10W through the forecast, with dissipation expected no later than 48 hours to the north of Guangzhou.


Tropical Cyclone 11W (Kirogi – Final Warning

According to the JTWC Warning number 19…

Sustained winds were 25 knots…with gusts to near 35 knots

Available meteorological data supports a resumption of tropical cyclone warnings. Animated enhanced infrared satellite imagery depicts flaring convection, but which has already begun to rapidly weaken. The previous exposed low level circulation center (llcc) was tracked westward and tucked under the convective envelope.

The environment is marginal at best, with warm sea surface temperatures, moderate to high vertical wind shear and strong dual channel outflow. The system is positioned in a unique spot on northwest side of a strong tropical upper-tropospheric trough (tutt) cell, at the inflection point where the easterly flow splits both poleward and equatorward, generating a dual channel outflow regime which has allowed for the uptick in intensity and organization.

Tropical Depression 11W (Kirogi) will continue to track westward for the next 12 hours or so, before turning sharply northward and moving into the Bungo Channel by 24 hours and continuing northeastward over northern Shikoku Island by the end of the forecast period. The aforementioned tutt cell is moving northward and over the next 12 to 24 hours, the two systems will align as they move north then northeast along the western side of a deep subtropical ridge to the east.

The general marginal conditions will not support intensification and in fact, conditions become increasingly hostile over the next 12 hours. The system will steadily weaken as it moves directly under the tutt cell and is torn apart by the frictional effects of the rugged terrain of Kyushu and Shikoku. Dissipation below 20 knots is expected no later than 36 hours, but potentially could occur within the next 24 hours.

>>> There’s an area of disturbed weather being referred to as Invest 99W…which is located approximately 224 NM southeast of Kadena AB

Animated multi-spectral satellite imagery depicts a partly obscured low level circulation center (llcc) with building convection to the southwest and lower level clouds wrapping around the llcc.

Upper-level analysis reveals a favorable environment with dual channel outflow to the north and south, low vertical wind shear (5-10 knots) and warm sea surface temperatures.

Global models are in good agreement that 99W will track north-northeast and continue to develop over the next 12-36 hours.

Maximum sustained surface winds are estimated at 17 to 22 knots.

The potential for the development of a significant tropical cyclone within the next 24 hours is upgraded to high.