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March 09, 2021,
12:00 UTC

Tropical Cyclone
New Caledonia
March 03-07, 2021

Tropical Cyclone NORAN during its rapid intensification
04.03., NASA

Severe Tropical Cyclone NIRAN was the sicth tropical cyclone and the second severe tropical cyclone of the 2020–21 Australian region cyclone season. It reached Category 5 with 10-minute sustained wind speeds of up to 245 kph and a minimum pressure of 931 hPa. It formed in the proximity of northern Queensland (Autralia) and moved very close along New Caledonia but did not make landfall.

On 25 February, the Bureau of Meteorology (BOM), the Australian weather service, registered a tropical depression in the northwestern part of the Coral Sea. In a pressure field favourable for cyclogenesis, it developed into a tropical cyclone on 01 March, which was named NIRAN by the BOM. Extremely favourable environmental conditions such as a sea surface temperature of 28°C, low vertical wind shear and a moist mid-troposphere led to the storm reaching category 2 tropical cyclone status on the same day.

Sea surface temperature, 07.03.: NOAA

NIRAN moved away from mainland Australia to the west and underwent rapid intensification, reaching category 3 by the late evening of 3 March. At 12 UTC on 5 March, the system reached its peak intensity as a strong category 5 tropical cyclone (on both the Australian scale and the Saffir-Simpson hurricane wind scale). At this time, NIRAN had 10-minute sustained winds of up to 245 kph and a strong, well-defined eye. The minimum air pressure of the system was 931 hPa.

NORANs trajectory: Background image from NASA, tracking information from NOAA

On its further trajectory, the storm moved into the Fiji Meteorological Service (FMS) area of responsibility as it moved in a southeasterly direction towards New Caledonia. On the evening of 05 March, NIRAN began an eyewall replacement cycle and entered an area of increasing vertical wind shear, which caused a weakening trend to begin. At 12:00 UTC on 06 March, NIRAN approached the main island of Grande Terre in New Caledonia as a category 3 tropical cyclone. The centre of the storm passed only about 20km south of the capital of New Caledonia, Nouméa. At this time, the system already showed a clear asymmetry with decreased convection in the northern part. Under increasing wind shear, the storm weakened to category 2 in the evening of 06 March. By the night of 7 March, NIRAN already underwent extratropical transition and dissipated rapidly.

Satellite image (visible) from GORAN, 05.03., 06 UTC: Himawari-8 NICT

Text: FS
March 09, 2021

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