Tropical Storm Tembin dropped heavy rain on Mindanao on Thursday. At 4:00 p.m. EST on Thursday the center of Tropical Storm Tembin was located at latitude 7.9°N and longitude 126.1°E which put it near Monkayo, Philippines. Tembin was moving toward the west-southwest at 12 m.p.h. (19 km/h). The maximum sustained wind speed was 60 m.p.h. (95 km/h) and there were wind gusts to 75 m.p.h. (120 km/h). The minimum surface pressure was 990 mb.
Tropical Storm Tembin intensified on Thursday before it made landfall on Mindanao. More thunderstorms developed near the core of the circulation and those storms generated stronger upper level divergence which pumped mass away from the tropical storm. The removal of mass allowed the surface pressure to decrease and the wind speed to increase. Although the circulation became much better organized, the distribution of thunderstorms was still asymmetrical. There were far fewer thunderstorms forming in the eastern half of the circulation.
The center of Tropical Storm Tembin will be moving across Mindanao for another day or so. The mountains on the island will disrupt the lower levels of the circulation and increased friction will slow the wind speed. Tropical Storm Tembin will weaken while the center is over Mindanao. However, the middle and upper parts of the circulation are likely to remain intact, and Tropical Storm Tembin will move through a favorable environment when it reaches the Sulu Sea. Tembin will move over water where the Sea Surface Temperature is near 29°C. An upper level ridge north of Tropical Storm Tembin is producing easterly winds which are blowing toward the top of the circulation. The winds in the middle and lower levels are also blowing from the east and the vertical wind shear will not be strong enough to prevent intensification of Tropical Storm Tembin once the center gets back over water. Temping could strengthen into a typhoon when it reaches the South China Sea.
The ridge north of Tembin is steering the tropical storm toward the west-southwest. A general motion toward the west is expected during the next two to three days. On its anticipated track Tropical Storm Tembin will move east to west over Mindanao during the next 24 hours. Afterwards, Tropical Storm Tembin will move across the Sulu Sea toward Palawan. Tembin could be near Palawan in about 48 hours and it could be over the South China Sea shortly thereafter.
Tropical Storm Tembin represents a serious hazard for Mindanao and nearby locations in the southern Philippines. Tembin is dropping heavy rain and it has the potential to cause serious floods. Water levels could rise quickly and flash floods could develop. Saturated soils could result in mudslides in areas of steeper terrain.
Farther to the west, Tropical Storm Kai-tak continued to move across the South China Sea. At 4:00 p.m. EST on Thursday the center of Tropical Storm Kai-tak was located at latitude 5.7°N and longitude 106.9°E which put it about 250 miles (400 km) east of Kuala Terengganu, Malaysia. Kai-tak was moving toward the west-southwest at 5 m.p.h. (8 km/h). The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h). The minimum surface pressure was 1000 mb.
Tropical Storm Kai-tak moved west of the Philippines and over the South China Sea on Tuesday. At 10:00 p.m. EST on Tuesday the center of Tropical Storm Kai-tak was located at latitude 8.2°N and longitude 112.0°E which put it about 425 miles (685 km) east-southeast of Ho Chi Minh City, Vietnam. Kai-tak was moving toward the west-southwest at 12 m.p.h. (19 km/h). The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h). The minimum surface pressure was 1000 mb.
The organization of the circulation of Tropical Storm Kai-tak improved on Tuesday. More thunderstorms developed near the center of circulation. The two stronger rainbands were north and west of the center. However, thunderstorms also developed in a couple of bands southeast of the center of circulation. These storms were the first to form in the eastern half of the circulation in several days. The distribution of the rainbands was still asymmetrical, but storms were occurring in more quadrants of Kai-tak. The storms in the two stronger rainbands were generating some upper level divergence which was pumping mass away to the west of the tropical storm.
Tropical Storm Kai-tak will be moving through an environment somewhat favorable for intensification during the next day or two. Kai-tak will move over water where the Sea Surface Temperature is near 29°C. Kai-tak is moving near the southwestern portion of a subtropical ridge. The ridge is producing easterly winds which are blowing toward the top of the circulation. The easterly winds are causing moderate vertical wind shear, but they have weakened somewhat during the past 24 hours. Less wind shear has allowed Tropical Storm Kai-tak to become better organized. Tropical Storm Kai-tak could strengthen during the next 24 to 36 hours.
The western end of the subtropical ridge is strengthening and the ridge is steering Tropical Storm Kai-tak toward the west-southwest. A general motion toward the west-southwest is expected to continue for the next two or three days. On its anticipated track the center of Tropical Storm Kai-tak is expected to pass south of the southern tip of Vietnam. Kai-tak is forecast to stay north of Borneo. The center of Tropical Storm Kai-tak could approach the region near the border between Thailand and Malaysia in about 72 hours.
Upper level wind shear decreased over the remnants of Jangmi on Thursday and thunderstorms redeveloped on the western side of the circulation. At 11:00 p.m. EST on Thursday the center of circulation of the remnants of Jangmi was located at latitude 5.8°N and longitude 112.0°E which put it about 360 miles northeast of Kuching, Malaysia on the island of Borneo and about 600 miles east of Kuala Terengganu, Malaysia. The center of circulation was moving just slightly south of due west at 8 m.p.h. The maximum sustained wind speed was 35 m.p.h. with gusts to 45 m.p.h. The minimum surface pressure was 1007 mb.
The subtropical ridge that was pushing strong southeasterly winds in the upper levels over the top of the remnants of Jangmi weakened slightly on Thursday. As the upper level winds slowed down, it allowed more thunderstorms to develop around the western half of the circulation. The increase of convection also increased the vertical extent of the circulation and created the potential for Jangmi to redevelop as a tropical cyclone. The circulation is over Sea Surface Temperatures near 28°C, which provide sufficient energy to support a tropical cyclone.
As the circulation has grown taller, it has been steered more toward the west. That pushed the center of circulation north of the northern tip of Borneo and kept it over the South China Sea. Guidance suggests that the remnants of Jangmi will continue to move in a generally westerly direction which would take it toward Malaysia.
Wind shear continues to prevent reintensification of former Tropical Storm Jangmi and the circulation consists primarily of shallow convection. The system still possesses a well developed cyclonic circulation in the lower atmosphere that is clearly apparent on visible satellite imagery. At 11:00 p.m. EST on Wednesday the center of the remnants of Jangmi were located at latitude 6.8°N and longitude 118.8°E which put it about 175 miles west-northwest of Jolo in the Philippines, about 140 miles east of Kudat, Malaysia and about 150 miles northeast of Sandakan, Malaysia. The center was moving toward the west-southwest at 6 m.p.h. The maximum sustained wind speed was 30 m.p.h. and there were gusts to 40 m.p.h. The minimum surface pressure was 1007 mb.
A subtropical ridge to the north of Jangmi continues to generate southeasterly winds with speeds near 35 m.p.h. in the upper levels over the system. The strong upper level winds are shearing the tops of thunderstorms which start to develop near the center and are preventing the redevelopment of Jangmi. The center of circulation is over warm Sea Surface Temperatures and so convection continues to develop but the strong wind shear keeps it shallow.
Since circulation is comprised almost entirely of shallow convection it is being steered by the winds in the lower level of the atmosphere. Those winds are likely to continue to carry the circulation in a generally west-southwesterly direction, which would bring it near the northern coast of Borneo in 18 to 24 hours. It could produce locally heavy rainfall and some flooding may be possible where it makes landfall.
Increased vertical wind shear blew the tops off of thunderstorms and Tropical Storm Jangmi weakened to a tropical depression, At 11:00 p.m. EST on Tuesday the center of Tropical Depression Jangmi was located at latitude 8.0°N and longitude 120.8°E which put it about 150 miles north of Jolo, Philippines and about 300 miles east-northeast of Kudat, Malaysia on the northern end of Borneo. Jangmi was moving toward the west-southwest at 7 m.p.h. The maximum sustained wind speed was 30 m.p.h. and there were gusts to 40 m.p.h.
A subtropical ridge north of Jangmi intensified southeasterly winds in the upper levels and increased the wind shear over the top of the tropical storm. The stronger upper level winds blew away the upper portions of thunderstorms and the circulation contained mainly shallower convection during the most recent 12 hours. Recent satellite images show the redevelopment of some thunderstorms southwest of the center of circulation, but some wind shear continues. Jangmi is over Sea Surface Temperatures that are warm enough to support some intensification, but that will not happen if the wind shear continues. If Jangmi continues to move southwestward, interaction with the island of Borneo could weaken the circulation and possibly cause it to dissipate entirely. If the center passes just west of Borneo, then some intensification may be possible, unless the wind shear remains too strong.
Since the circulation of Jangmi consisted mainly of shallower convection, it was steered toward the southwest by northeasterly winds in the lower levels of the atmosphere. Even though a few thunderstorms have redeveloped, most of the convection is still shallow and Jangmi is likely to continue to be steered in a generally west-southwesterly direction. The projected track could bring Jangmi or its remnants near the northern end of Borneo in 24-48 hours.