Tropical Cyclone 09W (Saola) / Tropical Cyclone 10W (Haikui) / Tropical Cyclone 11W (Kirogi) / Invest 98W / Invest 99W
Sunday, September 3, 2023

Current Snapshot

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By PDC’s Senior Weather
Specialist Glenn James

The Pacific Disaster Center’s (PDC Global) Sunday, September 3, 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 175 NM east of Hanoi, Vietnam – Final Warning

Tropical Cyclone 10W (Haikui)…is located approximately 147 NM southwest of Taipei, Taiwan

Tropical Cyclone 11W (Kirogi) – Final Warning…is located approximately 659 NM east-southeast of Sasebo, Japan – Final Warning


Northeast Pacific Ocean:

>>> Central East Pacific…

Invest 93E

A broad area of low pressure associated with a tropical wave is producing shower and thunderstorm activity with some signs of organization a few hundred miles south of the southern coast of Mexico.

Environmental conditions are expected to be conducive for further development of this system, and a tropical depression is expected to form during the next couple of days or so while the system moves westward to west-northwestward at 10 to 15 mph, passing well south of mainland Mexico.

* Formation chance through 48 hours…medium…60 percent
* Formation chance through 7 days…high…90 percent

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 09W (Saola) Final Warning

According to the JTWC Warning number 44…

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

Tropical depression 09W (saola) has weakened considerably after moving into the northern Gulf of Tonkin, primarily as a result of dry mid-level air and moderate southeasterly shear. Animated enhanced infrared satellite imagery shows a broad low level circulation comprised of low-level stratus and stratocumulus clouds, devoid of significant convection.

The system is drifting southward along the southeastern side of a low to mid-level ridge over central China. TD 10W will continue to slowly spin down over the next 12 to 24 hours as it tracks south-southwestward, fully dissipating as a tropical cyclone by 24 hours, to the west of Hainan Island.


Tropical Cyclone 10W (Haikui)

According to the JTWC Warning number 27…

Sustained winds were 75 knots…with gusts to near 90 knots

Typhoon 10W (Haikui) has traversed the rugged central mountain range of Taiwan, and already moved back out over water roughly between Tainan and Kaohsiung. While the system has been degraded to significant degree, the low-level eye is still relatively intact according to radar imagery.

Animated enhanced infrared and shortwave infrared satellite imagery, along with a series of microwave imagery however show the vortex is tilted to the west with height, with an eye quite a bit further west than where the radar and microwave data show it to be. This is not surprising given the fact that the vortex would have been torn apart when passing over the high terrain as well as by the presence of moderate easterly shear.

The environment remains overall marginally favorable, with moderate easterly shear and land interaction tempering the warm sea surface temperatures and decent radial outflow.

While TY 10W has now moved back over water and begins to transit away from the coast of Taiwan, it will steady up on a more west-northwest track under the steering influence of the ridge to the north. A second landfall is forecast between 24 and 36 hours along the coast of far southern Fujian Province, China.

While overall conditions remain favorable, multiple factors will preclude the system from intensifying; first, an influx of downslope wind will flow west off the coast of Taiwan and inject into the northern portion of the circulation through the next few hours. Second, sea surface temperatures while warm, are not as warm as those east of Taiwan and get cooler closer to the Chinese coast. This reduction is sea surface temperatures will rob the system of the fuel needed to intensify. Lastly, the system will move into an area of very weak upper-level outflow.

The combination of these factors will gradually weaken the system for the duration of its remaining time over water with landfall expected as a minimal typhoon. After landfall, the system slowly turns westward, then southwestward along the southern side of a developing anticylcone over central China while steadily weakening. Dissipation over land to the northwest of Hong Kong is expected by 96 hours.


Tropical Cyclone 11W (Kirogi) Final Warning

According to the JTWC Warning number 17…

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

Animated multi-spectral satellite imagery depicts a fully exposed shallow circulation center with brisk upper level diffluent winds providing ample vertical wind shear and fanning isolated thunderstorm activity to the northwest.

While a few convective pockets in the periphery may have some higher winds associated, these are likely outside of the analyzed 145 NM radius of outermost closed isobars. TC Kirogi should continue tracking west-northwest to westward as it dissipates over water due to strong (30 knot) vertical wind shear and relatively low mid-level relative humidity conditions.

>>> There’s an area of disturbed weather being referred to as Invest 98W…which is located approximately 1344 NM east of Yokosuka, Japan

The system is currently classified as a subtropical storm, generally characterized as having both tropical and mid-latitude cyclone features. Animated IR imagery depicts an asymmetric system with a partially-exposed low level circulation (llcc) center and convection sheared to the south.

The environment is marginally unfavorable for development as there is a strong upper-level cutoff low just to the south causing increased vertical wind shear (40-50 knots) across the llcc, hindering outflow but slightly offset by warm sea temperatures.

Global models agree that Invest 98W will track generally westward, weaken and dissipate within the next 72 hours.

Maximum sustained surface winds are estimated at 28 to 33 knots.

The potential for the development of a significant tropical cyclone within the next 24 hours remains low.

>>> There’s an area of disturbed weather being referred to as Invest 99W…which is located approximately 390 NM south-southeast of Kadena AB

Maximum sustained surface winds are estimated at 15 to 20 knots.

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