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Tropical Cyclone Ditwah Forms Near Sri Lanka

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Tropical Cyclone Ditwah formed over the southwestern Bay of Bengal on Thursday.  At 10:00 a.m. EST on Thursday the center of Tropical Cyclone Ditwah was located at latitude 7.8°N and longitude 81.6°E which put the center about 10 miles (15 km) northwest of Batticaloa, Sri Lanka.  Ditwah was moving toward the northwest at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 40 m.p.h. (50 km/h) and there were wind gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 1002 mb.

A low pressure system over the southwestern Bay of Bengal near Sri Lanka intensified on Thursday and the India Meteorological Department designated the system as Tropical Cyclone Ditwah.

The center of Tropical Cyclone Ditwah was near the east coast of Sri Lanka.  About half of Ditwah’s circulation was over Sri Lanka.  A band of thunderstorms was wrapped around the northern and western sides of the center of Tropical Cyclone Ditwah.  Other bands of showers and thunderstorms were revolving around the center of Ditwah’s circulation.  Storms near the center of Ditwah generated upper level divergence that pumped mass away to the west of the tropical cyclone.  The removal of mass caused the surface pressure to decrease slowly.

The distribution of wind speeds in Tropical Cyclone Ditwah was asymmetrical.  Winds to tropical storm force extended out 175 miles (280 km) in the southern half of Ditwah’s circulation.  Winds to tropical storm force extended out 80 miles (130 km) in the northern side of Tropical Cyclone Ditwah.

Tropical Cyclone Ditwah will move through an environment somewhat favorable for intensification during the next 24 hours.  Ditwah will move over water where the Sea Surface Temperatures are near 29°C.  It will move under the western part of an upper level ridge that is over Southeast Asia and the Bay of Bengal.  The upper level ridge will produce southeasterly winds that will blow toward the top of Ditwah’s circulation.  Those winds will cause moderate vertical wind shear.  The vertical wind shear will inhibit intensification.  The fact that almost half of Ditwah’s circulation is over Sri Lanka will also inhibit intensification.  Tropical Cyclone Ditwah could intensify during the next 24 hours even with moderate vertical wind shear, if the center of its circulation remains over water.

Tropical Cyclone Ditwah will move around the southwestern part of a high pressure system over the Bay of Bengal.  The high pressure system will steer Ditwah toward the northwest during the next 24 hours.  On its anticipated track, the center of Tropical Cyclone Ditwah will move along the coast of northeastern Sri Lanka.  Ditwah could approach the coast of India near Chennai within 72 hours.

Tropical Cyclone Ditwah will produce strong winds and heavy rain over Sri Lanka.  Heavy rain will cause flash floods in some locations.

Tropical Cyclone Could Form East of Sri Lanka

A tropical cyclone could form over the Bay of Bengal east of Sri Lanka during the next 24 hours. A low pressure system over the southern Bay of Bengal was designated as Invest 90B on Monday. At 10:00 p.m. EST on Monday the center of the low pressure system was located at latitude 8.5°N and longitude 84.5°E which put it about 185 miles (300 km) east-northeast of Batticaloa, Sri Lanka. The low pressure system was moving toward the west at 8 m.p.h. (13 km/h). The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were wind gusts to 45 m.p.h. (75 km/h). The minimum surface pressure was 1004 mb.

The circulation around a low pressure system over the Bay of Bengal east of Sri Lanka strengthened on Monday. More thunderstorms formed near the center of the low pressure system and the inner end of a rainband wrapped partly around the center of circulation. More thunderstorms formed in bands revolving around the center. Storms near the center of circulation generated upper level divergence that pumped mass away to the west of the low pressure system.

The low pressure system will move through an environment favorable for the formation of a tropical cyclone during the next 24 hours. The low pressure system will move over over water where the Sea Surface Temperatures are near 27˚C. It will move under the western end of an upper level ridge centered over Southeast Asia. The ridge will produce southeasterly winds that will blow toward the top of the low pressure system. Those winds will cause vertical wind shear and the shear will inhibit somewhat the formation of a tropical cyclone. However, the wind shear may not be strong enough to prevent the low pressure system from strengthening into a tropical cyclone. Invest 90B could strengthen to a tropical cyclone during the next 24 hours.

The low pressure system will move south of a strong high pressure system over southern Asia. The high pressure system will steer the low pressure system toward the west-southwest. On its anticipated track the low pressure system could reach the east coast of Sri Lanka within 24 hours. The low pressure system will bring gusty winds and locally heavy rain to Sri Lanka. Heavy rain could cause flash floods in some locations.