Tropical Cyclone Diane formed north of La Reunion on Friday. At 10:00 a.m. EST on Friday the center of Tropical Cyclone Diane was located at latitude 19.3°S and longitude 56.2°E which put it about 110 miles (175 km) north-northeast of St. Denis, La Reunion. Diane was moving toward the east-southeast at 18 m.p.h. (30 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 997 mb.
A distinct low level center of circulation developed in an area of low pressure east of Madagascar on Friday and the system was designated as Tropical Cyclone Diane. The distribution of thunderstorms around Tropical Cyclone Diane was asymmetrical. Many of the stronger thunderstorms were occurring northwest of the center of circulation. Bands of showers and thunderstorms were developing east of the center of Diane. Storms near the center of circulation were beginning to generate upper level divergence which was pumping mass away to the southeast of the tropical cyclone.
Tropical Cyclone Diane will move through an environment somewhat favorable for intensification during the next 24 to 36 hours. Diane will move over water where the Sea Surface Temperature is near 28°C. An upper level trough west of Madagascar and an upper level ridge east of Mauritius will interact to produce northwesterly winds which will blow toward the top of the tropical cyclone. Those winds will cause moderate vertical wind shear which will inhibit intensification. Tropical Cyclone Diane could intensify slowly during the next 24 to 36 hours.
The upper level trough and upper level ridge will steer Tropical Cyclone Diane toward the east-southeast during the next several days. On its anticipated track Tropical Cyclone Diane could bring wind and rain to Mauritius within 12 hours. Locally heavy rain could cause flash floods in some locations.
The organization of a small area of low pressure (also known as Invest 95S) south of Java increased early on Monday and the Badan Meteorologi Klimatologi Dan Geofisika (BMKG) Tropical Cyclone Warning Center in Jakarta designated the system as Tropical Cyclone Cempaka. At 7:00 a.m. EST on Monday the center of Tropical Cyclone Cempaka was located at latitude 8.8°S and longitude 110.8°E which put it about 70 miles (115 km) south-southeast of Yokyakarta, Indonesia. Cempaka was moving toward the east- northeast 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 997 mb.
Tropical Cyclone Cempaka has a small but well developed center of circulation. Radar images from BKMG showed an eyelike feature at the center of circulation. The strongest winds are occurring in a ring of showers and thunderstorms that surrounds the center. The stronger storms are in the eastern half of the ring. Other narrow rainbands are developing outside the core of Cempaka. Thunderstorms around the center are generating some upper level divergence which is pumping mass away from the tropical cyclone. Winds to tropical storm force extend out about 40 miles (65 km) from the center of circulation.
Tropical Cyclone Cempaka will be in an environment somewhat favorable for intensification during the next 24 to 48 hours. Cempaka will move over water where the Sea Surface Temperature is near 29°C. Tropical Cyclone Cempaka is under an upper level ridge and the upper level winds are weak. There is little vertical wind shear over the tropical cyclone. The core of Tropical Cyclone Cempaka is near Java. Part of the circulation is flowing over Java and nearby islands and friction from those islands is slowing the winds. Interaction with land is the primary factor inhibiting intensification. If the center of Tropical Cyclone Cempaka remains south of Java, then it has a chance to intensify. If Cempaka moves closer to Java, then it could weaken. Also, since Cempaka is a very small tropical cyclone, an increase in the speed of the upper level winds could blow the top off of the circulation.
Since Tropical Cyclone Cempaka is underneath an upper level ridge, the steering winds are weak. Cempaka is south of the center of the ridge and weak westerly winds are steering the tropical cyclone slowly toward the east-northeast. Tropical Cyclone Cempaka is forecast to meander south of Java for several more days because of the weak stearing winds.
Tropical Cyclone Cempaka is producing locally heavy rain over parts of Java, Bali and nearby islands. The locally heavy rain could cause flash floods as Cempaka meanders south of Java during the next day or two.
A small, but well organized area of low pressure developed just to the south of Java on Sunday. The low pressure system is currently designated as Invest 95S, but it could become a tropical cyclone during the next several days. At 10:00 p.m. EST on Sunday the center of Invest 95S was located at latitude 8.9°S and longitude 109.8°E which put it about 100 miles (160 km) southwest of Yogyakarta, Indonesia. It was moving toward the northeast at 4 m.p.h. (6 km/h). The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were gusts to 45 m.p.h. (75 km/h). The minimum surface pressure was 998 mb.
The circulation of Invest 95S is small but well formed. There is a distinct low level center of circulation. Two well formed narrow rainbands wrapped around the southern and northeastern sides of the center. Other rainbands developed just outside the core of the circulation. Storms near the center of circulation were generating some upper level divergence which was pumping out mass and allowing the surface pressure to decrease.
Invest 95S will move through an environment that is mostly favorable for intensification. It will move over water where the Sea Surface Temperature is near 29°C. Invest 95S is near the center of an upper level ridge. The upper level winds blowing over the top of the low pressure system are weak and there is not a lot of vertical wind shear. The proximity of the circulation to Java is the only factor likely to inhibit intensification. If the center of circulation remains south of Java, then there is a good chance it could intensify into a tropical cyclone.
The ridge north of Invest 95S is steering the system slowly toward the northeast and a general easterly motion is expected to continue during the next 24 hours. Guidance from numerical models diverges in a day or so. Some models to suggest the northeasterly motion will continue and the low pressure system will move across Java. Other models predict a turn toward the south in a day or so. There is a high degree of uncertainty about the future track of Invest 95S.