Tropical Cyclone Oma Forms Northwest of Vanuatu

Tropical Cyclone Oma formed over the Coral Sea northwest of Vanuatu on Tuesday.  At 10:00 a.m. EST on Tuesday the center of Tropical Cyclone Oma was located at latitude 13.8°S and longitude 165.6°E which put it about 330 miles (535 km) northwest of Port Vila, Vanuatu.  Oma was moving toward the east at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 50 m.p.h. (80 km/h) and there were wind gusts to 65 m.p.h. (105 km/h).  The minimum surface pressure was 988 mb.

A distinct low level center of circulation formed within a broader area of low pressure northwest of Vanuatu on Tuesday and the Fiji Meteorological Service designated the system as Tropical Cyclone Oma.  The distribution of thunderstorms around Oma was asymmetrical.  Many of the stronger thunderstorms were occurring in bands northwest of the center of circulation.  Bands southeast of the center consisted primarily of showers and lower clouds.  The thunderstorms northwest of the center were generating upper level divergence which was pumping mass away to the northwest of the tropical cyclone.

An upper level ridge northeast of Vanuatu was producing southeasterly winds which were blowing toward the top of Tropical Cyclone Oma.  Those winds were causing moderate vertical wind shear and they were inhibiting upper level divergence to the southeast of Oma.  The wind shear was the probable cause of the asymmetrical distribution of thunderstorms.

Tropical Cyclone Oma will move through an environment somewhat favorable for intensification during the next several days.  The upper level ridge will continue to cause vertical wind shear.  However, Oma will move over water where the Sea Surface Temperature is near 30°C.  Tropical Cyclone Oma could slowly strengthen during the next day or two.

Tropical Cyclone Oma is currently embedded in a monsoon trough that is steering it toward the east.  A subtropical ridge is forecast to strengthen east of Vanuatu.  Oma will slow down while the ridge builds east of Vanuatu and it could linger northwest of Vanuatu for several days.  The ridge will eventually turn Tropical Cyclone Oma toward the south.  The timing and location of that turn will be important.  If Oma moves farther east before it turns southward, then it could approach northwest Vanuatu in 24 to 36 hours.  If Oma stalls and then turns southward, then the strongest part of the tropical cyclone could pass west of Vanuatu.  Tropical Cyclone Oma could eventually move near New Caledonia in a few days.

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