By PDC’s Senior Weather
Specialist Glenn James
The Pacific Disaster Center’s (PDC Global) Monday, August 14, 2023, Tropical Cyclone Activity Report…for the Pacific Ocean, the Indian Ocean, and adjacent Seas
Current Tropical Cyclones:
Tropical Cyclone 07E (Fernanda)…is located about 780 miles west-southwest of the southern tip of Baja California
Tropical Cyclone 08E (Greg)…is located about 985 miles southeast of Hilo, Hawaii
Tropical Cyclone 05E (Dora)…is located about 100 miles northeast of Wake Island
Tropical Cyclone 07W (Lan)…is located approximately 220 NM west-southwest of Yokosuka, Japan
Northeast Pacific Ocean:
Tropical Cyclone 07E (Fernanda)
FERNANDA BEGINNING TO WEAKEN
According to the NHC advisory number 10…
Fernanda is moving toward the west-northwest near 9 mph (15 km/h) and a westward to west-northwestward motion with an increase in forward speed is expected during the next several days.
Maximum sustained winds have decreased to near 120 mph (195 km/h) with higher gusts. Fernanda is a category 3 hurricane on the Saffir-Simpson Hurricane Wind Scale. Additional weakening is forecast during the next several days.
Hurricane-force winds extend outward up to 30 miles (45 km) from the
center and tropical-storm-force winds extend outward up to 90 miles
>>> Off the coast of southern Mexico and SW Mexico…
A broad area of low pressure associated with a tropical wave is producing widespread showers and thunderstorms off the southern coasts of Mexico, Guatemala, and El Salvador. Environmental conditions appear conducive for development, and a tropical depression is expected to form within the next two days or so, while the system moves west-northwestward, roughly parallel to the coast of southern and southwestern Mexico.
* Formation chance through 48 hours…high…80 percent
* Formation chance through 7 days…high…90 percent
>>> South of Central America and Southern Mexico…
An area of low pressure could form south of the Gulf of Tehuantepec over the weekend. Some gradual development of this system is possible thereafter while it moves generally westward.
* Formation chance through 48 hours…low…near 0 percent
* Formation chance through 7 days…low…20 percent
Central Pacific Ocean:
Tropical Cyclone 08E (Greg)
LITTLE CHANGE IN GREG AS IT CONTINUES TO MOVE TO THE WEST
According to the CPHC advisory number 5…
Greg is moving toward the west near 12 mph (19 km/h). A general westward trend is expected over the next few days.
Maximum sustained winds are near 45 mph (75 km/h) with higher gusts.
Some slight strengthening is forecast during the next couple of days.
Tropical-storm-force winds extend outward up to 35 miles (55 km) from the center.
Western Pacific, Indian Ocean and adjacent Seas:
Tropical Cyclone 05E (Dora)
According to the JTWC warning number 59…
Sustained winds are 30 knots…with gusts to 40 knots
Animated enhanced infrared satellite imagery shows a system with its flaring central convection severely sheared northeastward, intermittently exposing the low level circulation.
Analysis indicates a marginal environment with warm sea surface temperatures and strong poleward outflow greatly offset by strong southwesterly vertical wind shear.
TS Dora will continue on a northwestward track passing approximately 105 NM northeast of wake island. After 12 hours, the cyclone will track northward as the ridge recedes eastward.
The marginal environment will sustain the current intensity up to 48 hours. Afterward, increased outflow ahead of a mid-latitude trough will weaken the ridge and drive the system northeastward, increase the poleward outflow and slightly intensify the system to 45 knots up to 96 hours before strong vertical wind shear once again offsets the strong outflow, reducing it to 35 knots by 120 hours.
There is a distinct possibility that strong vertical wind shear will be overwhelming and dissipate the system before 120 hours.
Tropical Cyclone 07W (Lan)
According to the JTWC Warning number 30…
Sustained winds were 60 knots…with gusts to near 75 knots
Animated enhanced infrared satellite imagery shows a medium-sized symmetrical cyclone that has maintained its overall convective and wrap structure with a large 40 NM banding eye, exposing a ragged and irregular but defined low level circulation center.
Analysis indicates a marginal environment with low vertical wind shear and moderate outflow offset by localized low sea surface temperatures, due to oceanic upwelling and dry air intrusion.
Typhoon Lan will continue on its current northwestward track and make landfall before 12 hours over Wakayama Prefecture, then inland just to the west of Kyoto, exit into the Sea of Japan by 12 hours. Afterward, it will track more northward, crest the ridge axis before 24 hours then accelerate northeastward as the ridge recedes in response to a mid-latitude trough approaching from the northwest, and clipping the northern tip of Hokkaido just before 72 hours.
The marginal environment will become unfavorable with dry air intrusion, increasing vertical wind shear, then land interaction reducing it to 60 knots by 24 hours. Despite the relatively warm sea surface temperatures in the Sea of Japan, increasing vertical wind shear then interaction with the baroclinic zone as TY 07W begins extra-tropical transition by 48 hours will gradually erode it to a 40 knot cold core low by 72 hours.