Tag Archives: Invest 99S

Tropical Low Forms West of Darwin

A Tropical Low formed west of Darwin, Australia on Wednesday night. At 10:00 p.m. EST on Wednesday the center of the Tropical Low was located at latitude 12.5°S and longitude 128.5°E which put it about 160 miles (255 km) west of Darwin, Australia. The Tropical Low was nearly stationary. The maximum sustained wind speed was 30 m.p.h. (50 km/h) and there were wind gusts to 40 m.p.h. (65 km/h). The minimum surface pressure was 1006 mb.

The circulation around a small low pressure system over the Timor Sea west of Darwin, Australia exhibited more organization on Wednesday night and the Australian Bureau of Meteorology designated the system as a Tropical Low. The strongest thunderstorms were occurring in bands northwest of the center of the circulation. There was also a band of thunderstorms in the southwestern part of the Tropical Low. Bands in the northeastern part of the circulation consisted primarily of showers and lower clouds.

The Tropical Low will be in an area where the steering winds are weak during the next 36 hours and it is forecast to remain nearly stationary. The Tropical Low will be in an environment somewhat favorable for intensification. The Tropical Low will be over water where the Sea Surface Temperatures are near 30˚C. It will be under the northern part of an upper level ridge centered over northern Australia. The ridge will produce easterly winds that will blow toward the top of the Tropical Low. Those winds will cause moderate vertical wind shear and the shear will inhibit intensification. The Tropical Low could gradually strengthen during the next 36 hours.

The Tropical Low is forecast to move toward Australia during the weekend. A Watch has been issued for the portion of the coast from Point Stuart to Kalumburu. The Watch includes Darwin, Wyndham, Wadeye and the Tiwi Islands.

Tropical Cyclone Berguitta Intensifies Into Equivalent of a Hurricane

Tropical Cyclone Berguitta intensified into the equivalent of a hurricane/typhoon on Sunday.  At 10:00 p.m. EST on Sunday the center of Tropical Cyclone Berguitta was located at latitude 17.8°S and longitude 63.1°E which put it about 415 miles (670 km) east-northeast of Port Louis, Mauritius.  Berguitta was nearly stationary.  The maximum sustained wind speed was 75 m.p.h. (120 km/h) and there were wind gusts to 90 m.p.h. (145 km/h).  The minimum surface pressure was 985 mb.

The circulation of Tropical Cyclone Berguitta continued to get better organized on Sunday.  An eye appeared intermittently at the center of circulation.  The eye was surrounded by an elliptical ring of thunderstorms and the strongest winds were occurring in those storms.  Bands of showers and thunderstorms were revolving around the core of the circulation.  Storms near the center of Berguitta were generating upper level divergence which was pumping mass away from the center of circulation.

Tropical Cyclone Berguitta will continue to move through an environment favorable for intensification during the next several days.  Berguitta will move over water where the Sea Surface Temperature is near 28°C.  The upper level winds are weak and there is little vertical wind shear.  Tropical Cyclone Berguitta will continue to strengthen and it could intensify into the equivalent of a major hurricane.

Tropical Cyclone Berguitta is moving in a region where the steering winds are weak.  Berguitta moved little on Sunday.  A subtropical ridge south of Berguitta is forecast to steer the tropical cyclone slowly westward during the next 24 to 48 hours.  Berguitta will near the western end of the ridge in about two days and it is likely to move toward the southwest after that time.  On its anticipated track Tropical Cyclone Berguitta could reach Mauritius within 72 hours.

The core of Tropical Cyclone Berguitta could move very close to Mauritius and La Reunion.  Berguitta could be the equivalent of a major hurricane at that time.  It has the potential to cause major wind damage, a storm surge, heavy rain and floods.

Elsewhere over the South Indian Ocean microwave images of Invest 99S depicted a structure that looked very much like a tropical cyclone.  At 10:00 p.m. EST on Sunday the center of Invest 99S was centered at latitude 15.1°S and longitude 41.6°E which put it about 75 miles (120 km) east of Lumbo, Mozambique.  Microwave satellite images showed a clear area at the center of circulation surrounded by broken ring of showers and thunderstorms.  A primary rainband wrapped around the eastern side of the circulation and secondary bands of showers and thunderstorms existed in all quadrants of the circulation.  However, no official government agency is classifying the system as a tropical cyclone at the current time.