Tag Archives: 90S

Tropical Depression Forms Northeast of Comoros

A tropical depression formed over the South Indian Ocean northeast of Comoros on Tuesday morning. At 11:00 a.m. EDT on Tuesday the center of a tropical depression was located at latitude 7.7°S and longitude 45.0°E which put it about 250 miles (400 km) northeast of the Comoros. The tropical depression was moving toward the southwest at 11 m.p.h. (17 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 1003 mb.

A low pressure system over the South Indian Ocean northeast of Comoros exhibited more organization on Tuesday morning and Meteo France La Reunion designated the system as a tropical depression. More thunderstorms formed near the center of the tropical depression. Thunderstorms also developed in bands revolving around the center of circulation. Storms near the center began to generate upper level divergence that pumped mass away from the tropical depression.

The tropical depression will move through an environment favorable for intensification during the next 24 hours. The tropical depression will move over water where the Sea Surface Temperatures are near 29°C. It will move under the western end of the axis of an upper level ridge over the South Indian Ocean. The upper level winds are weak near the axis of the ridge and there will be little vertical wind shear. The tropical depression is likely to intensify to the equivalent of a tropical storm during the next 24 hours.

The tropical depression will move around the northern side of a high pressure system over the South Indian Ocean. The high pressure system will steer the tropical depression toward the west-southwest during the next 24 hours. On its anticipated track the tropical depression will move over Comoros on Wednesday. It will bring gusty winds and locally heavy rain to Comoros. Locally heavy rain is likely to cause flash floods in some locations. The tropical depression could approach the coast of Africa near southern Tanzania and northern Mozambique later this week.

Tropical Low Forms Over Western Australia

An area of low pressure system has been moving across northern Australia during the past few days.  The low remains organized and the Australian Bureau of Meteorology classified the system as a Tropical Low on Wednesday because of the potential for it to develop into a tropical cyclone.  At 10:00 a.m. EST on Wednesday the center of the Tropical Low was located at latitude 15.9°S and longitude 127.0°E which put it about 80 miles (130 km) west-southwest of Wyndham, Australia.  The Tropical Low was moving toward the west at 9 m.p.h. (15 km/h).  The maximum sustained wind speed was 30 m.p.h. (50 km/h) an there were wind gusts to 40 m.p.h. (65 km/h).  The minimum surface pressure was 1002 mb.

There is a well defined cyclonic circulation in the lower levels of the atmosphere, but there are not many thunderstorms in the core of that circulation.  Most of the thunderstorms are developing in bands that are on the periphery of the circulation.  The strongest thunderstorms are forming in bands in the western portion of the circulation as that part of the Tropical Low begins to moves over water.  The strongest winds are also occurring in these thunderstorms that are over water.  The Tropical Low is moving underneath an upper level ridge and the ridge is causing upper level divergence which is pumping out mass.

The core of the Tropical Low is still over Western Australia and moving over land is the primary factor inhibiting intensification of the system.  The atmospheric environment is favorable for intensification.  The upper level ridge is producing light winds over the Tropical Low and there is little vertical wind shear.  The Sea Surface Temperature of the water west of Australia is near 30°C and there will be plenty of energy in the ocean to support strengthening when the core of the circulation moves west of Australia.  Some slow organization of the circulation is possible during the next 12 hours as the core of the Tropical Low moves closer to the coast of Western Australia.  Further intensification is likely during the next several days once the core of the Tropical Low moves over the warm water.  The Tropical Low could strengthen into the first named tropical cyclone of 2017 later this week.

The upper level ridge is producing light easterly winds which are slowly steering the Tropical Low toward the west.  That general motion is expected to continue for another day or so.  Eventually, the Tropical Low is forecast to move on a west-southwesterly track that would paralle, but keep it to the west of the coast of Western Australia during the next several days.