By PDC’s Senior Weather
Specialist Glenn James
The Pacific Disaster Center’s (PDC Global) Saturday, September 30, 2023, Tropical Cyclone Activity Report…for the Pacific Ocean, the Indian Ocean, and adjacent Seas
Current Tropical Cyclones:
Tropical Cyclone 14W (Koinu)…is located approximately 518 NM north-northeast of Manila, Philippines
Northeast Pacific Ocean:
>>>South of Southwestern Mexico…
An area of disorganized showers and thunderstorms associated with a tropical wave is located several hundred miles south of the coast of southern Mexico.
Environmental conditions appear favorable for gradual development of this system, and a tropical depression is likely to form during the middle to latter part of next week while it moves generally northwestward.
* Formation chance through 48 hours…low…20 percent
* Formation chance through 7 days…high…70 percent
Central North Pacific:
There are no tropical cyclones, nor any areas of disturbed weather under investigation by the CPHC at the time of this writing.
Western Pacific, Indian Ocean and adjacent Seas:
Tropical Cyclone 14W Koinu
According to the JTWC Warning number 7…
Sustained winds were 55 knots…with gusts to near 70 knots
Animated enhanced infrared satellite imagery depicts a steadily growing central dense overcast (cdo) feature that is obscuring the low level circulation center beneath. A microwave image reveals better organized low level cloud lines and a single dominant convective band wrapping around the southern semicircle.
TS 14W (Koinu) is forecast to continue on a north-northwesterly heading as the steering ridge to the northeast continues to break down. By 48 hours however, this ridge builds back
westward and forces 14W towards the southern tip of Taiwan and into the very northern region of the South China Sea through the forecast period.
In terms of intensity, vertical wind shear (vws) remains the primary limiting force preventing considerable intensification. As evidenced by the growing cdo, the system is improving its vertical alignment and core structure ever more rapidly. If this trend continues over the next 36 hours, the system will continue to intensify, eventually reaching 70 knots by 36 hours.
By 48 hours, the chances for rapid intensification may increase, as the system crosses the 20th parallel. GFS is indicating that 14W may tap into vigorous dual channel outflow, both poleward and equatorward, which when coupled with decreased vertical wind shear and warm sea surface temperatures, will quickly intensify 14W to around 95 knots by 72 hours.
In the extended track forecast, as the system passes the southern tip of Taiwan, the vigorous outflow aloft is generally lost, resulting in a slightly reduced intensification trend through the forecast period and a resultant peak intensity of 110 knots by 120 hours.