By PDC’s Senior Weather
Specialist Glenn James
Tropical Cyclone 04W (Chaba) is located approximately 177 NM southwest of Hong Kong
Tropical Cyclone 05W (Aere) is located approximately 181 NM southeast of Kadena AB
Central East Pacific:
Afternoon satellite-derived surface wind data indicated that a small, well-defined surface circulation has formed several hundred miles southwest of the southern tip of the Baja California peninsula.
Showers and thunderstorms are limited, however, and further development of this system is not likely to occur while it moves westward at 10 to 15 mph over gradually decreasing sea surface temperatures and into a less favorable environment.
* Formation chance through 48 hours…low…30 percent
* Formation chance through 5 days…low…30 percent
>>> Northwest and Southwest Pacific Ocean, Indian Ocean, Arabian Sea
Tropical Cyclone 04W (Chaba)
According to the JTWC Warning number 10, sustained winds were 75 knots with gusts to near 90 knots.
Animated enhanced infrared satellite imagery depicts spiral bands of deep convection wrapping into a defined low level circulation center (llcc). Another image depicted formative banding wrapping into the llcc with a broad and fragmented microwave eye feature, although the image showed that small eye feature seen in earlier imagery has become more ragged and less defined within the last 6 hours.
Environmental conditions are favorable with warm sea surface temperatures, low (10-15 knot) easterly vertical wind shear and moderate to strong equatorward outflow.
TS 04W (Chaba) is forecast to continue tracking northwestward, being pushed toward the Chinese coast by the mid-level steering ridge currently over the northern Philippines. The system is expected to make landfall near the Luichow Peninsula near 24 hours.
As the ridge weakens and erodes from the west, TS 04W will turn into the resulting weakness in the ridge and turn more poleward after making landfall.
In the near-term, the system looks to potentially cash in on some divergent flow aloft, weakening the already low shear, which will allow for convective consolidation and intensification to a peak of 70 knots prior to landfall.
Some rapid intensification guidance is still triggering with this run, and thus it is still possible to see a slightly higher peak occur just prior to landfall as the system moves over shallow, warm coastal waters. Once ashore, the will rapidly weaken due to terrain interaction, ultimately dissipating over southern China by 48 hours.
Tropical Cyclone 05W (Aere)
According to the JTWC Warning number 7, sustained winds were 45 knots with gusts to near 55 knots.
Satellite imagery over the past six hours depicts a mass of flaring convection developed just east of the low level circulation center (llcc) but never consolidated over the llcc due to the persistent strong westerly winds aloft.
The environment is marginally favorable with divergent outflow offsetting high vertical wind shear.
Over the next 12 hours, the system is expected to take on a more northwestward track while maintaining an 10-12 knot speed of advance, moving through the Ryuku chain between 24 and 36 hours.
After crossing into the East China Sea, the system is expected to slow down as the steering pattern begins to shift, with an extension of the ridge building in across north of the system, across the Korean Peninsula.
The ridge extension pinches off as a separate area of high heights by 60 hours with an induced trough between this new ridge center over North Korea and the ridge southeast of Tokyo, enticing TS 05W to turn into the weakness in the ridge by 72 hours.
The system will then begin to pick up speed once more as it moves eastward along the northwest periphery of the ridge southeast of Japan. the system is expected to skirt the northwest coast of Kyushu then track along the northwestern coast of Honshu through the end of the forecast period.
While upper-level winds remain strong to the west-southwest of the system, the forecast fields call for a relaxation of the vertical wind shear gradient in vicinity of TS 05W, which should allow for some intensification over the next 24 hours before passing the Ryukus, though this will depend in large part on the ability of the vortex to consolidate
Decreased shear and increased poleward outflow into the base of an upper-level trough will allow for a short burst of additional intensification to a peak of 55 knots before increased shear, dry air entrainment and cooler sea surface temperatures conspire to weaken the system.
by 96 hours the system will begin to weaken more rapidly as the terrain of Honshu disrupts the low level inflow and shear continues to increase.