WTIO30 FMEE 221307
RSMC / TROPICAL CYCLONE CENTER / LA REUNION
TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN)

0.A WARNING NUMBER: 3/4/20202021
1.A ZONE OF DISTURBED WEATHER 4

2.A POSITION 2020/12/22 AT 1200 UTC:
WITHIN 20 NM RADIUS OF POINT 13.7 S / 61.8 E
(THIRTEEN DECIMAL SEVEN DEGREES SOUTH AND
SIXTY ONE DECIMAL EIGHT DEGREES EAST)
MOVEMENT: SOUTH-WEST 4 KT

3.A DVORAK ANALYSIS: 1.0/1.0/S 0.0/24 H

4.A CENTRAL PRESSURE: 1004 HPA
5.A MAX AVERAGE WIND SPEED (10 MN): 25 KT
RADIUS OF MAXIMUM WINDS (RMW): NIL

6.A EXTENSION OF WIND BY QUADRANTS (KM):
NIL

7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1009 HPA / 1000 KM
8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION: SHALLOW

1.B FORECASTS (WINDS RADII IN KM):
12H: 2020/12/23 00 UTC: 13.9 S / 61.2 E, VENT MAX= 025 KT, ZONE OF
DISTURBED WEATHER

24H: 2020/12/23 12 UTC: 13.9 S / 60.3 E, VENT MAX= 025 KT, ZONE OF
DISTURBED WEATHER

36H: 2020/12/24 00 UTC: 13.9 S / 59.5 E, VENT MAX= 025 KT, TROPICAL
DISTURBANCE

48H: 2020/12/24 12 UTC: 13.8 S / 58.9 E, VENT MAX= 030 KT, TROPICAL
DEPRESSION
28 KT NE: 100 SE: 140 SW: 165 NW: 45

60H: 2020/12/25 00 UTC: 13.8 S / 57.9 E, VENT MAX= 035 KT, MODERATE
TROPICAL STORM
28 KT NE: 120 SE: 140 SW: 165 NW: 85
34 KT NE: 110 SE: 110 SW: 75 NW: 75

72H: 2020/12/25 12 UTC: 14.1 S / 56.5 E, VENT MAX= 040 KT, MODERATE
TROPICAL STORM
28 KT NE: 130 SE: 140 SW: 165 NW: 85
34 KT NE: 120 SE: 120 SW: 75 NW: 75

2.B LONGER-RANGE OUTLOOK:
96H: 2020/12/26 12 UTC: 15.3 S / 53.0 E, VENT MAX= 055 KT, SEVERE
TROPICAL STORM
28 KT NE: 155 SE: 150 SW: 165 NW: 95
34 KT NE: 150 SE: 140 SW: 85 NW: 85
48 KT NE: 85 SE: 85 SW: 75 NW: 75

120H: 2020/12/27 12 UTC: 16.1 S / 49.5 E, VENT MAX= 060 KT, OVERLAND
DEPRESSION
28 KT NE: 175 SE: 165 SW: 165 NW: 100
34 KT NE: 165 SE: 155 SW: 85 NW: 95
48 KT NE: 90 SE: 90 SW: 70 NW: 80

2.C ADDITIONAL INFORMATION:

OVER THE LAST 24 HOURS, THE ORGANIZATION OF THE ZONE OF DISTURBED
WEATHER 04 SEEMS TO BE LESS DEFINED. ON THE LATEST IMAGES, CONVECTIVE
ACTIVITY IS MAINLY PRESENT ONLY IN THE SOUTHERN SEMICIRCLE. THE
LATEST SCATTEROMETER DATA RATHER SHOW A VERY LONG CIRCULATION,
WITHOUT A WELL DEFINED CENTER. MAXIMUM WINDS ARE AROUND 20 TO 25KT,
FAR FROM THE CENTER.

IN TERMS OF INTENSITY, UNTIL THURSDAY, THE SYSTEM SHOULD REMAIN WEAK
ON THE EDGE OF THE UPPER RIDGE, AHEAD OF AN UPPER TROUGH MOVING FROM
THE SOUTH-WEST, UNDERGOING A MODERATE NORTH-WESTERLY SHEAR.
THEREAFTER, THE LOW COULD AGAIN EVOLVE BELOW THE UPPER RIDGE AND
BENEFIT FROM AN EXCELLENT DIVERGENCE IN THE NORTHWEST QUADRANT. IT
COULD THEN ENTER A DEEPENING PHASE. THIS FORECAST IS A CONSENSUS OF
THE LATEST TRENDS REFLECTED BY THE NUMERICAL MODELS. NEVERTHELESS, IN
VIEW OF THE STRONG UNCERTAINTIES, ESPECIALLY CONCERNING THE PERIOD
AFTER THURSDAY, NO SCENARIO CAN BE RULED OUT. THE SYSTEM COULD REMAIN
OF LOW INTENSITY AS WELL AS IT COULD BECOME A TROPICAL CYCLONE.

IN TERMS OF TRACK, THE SYSTEM IS CURRENTLY MOVING ON THE NORTHERN
FACADE OF THE MASCARENE HIGH, CURRENTLY DRIVING A WEAK SHALLOW
EASTERLY FLOW THAT FAVOR A SLOW WESTWARD MOVEMENT. AT LONGER RANGE, PARTICULARLY IF THE DEEPENING OCCUR, THE SYSTEM WILL BE DRIVEN BY THE NORTHWESTERN SIDE OF THE SUBTROPICAL RIDGE FAVOURING A
WEST-SOUTHWESTERLY TRACK.

THIS SYSTEM IS NOT LIKELY TO PRESENT A DIRECT THREAT TO THE
MASCARENES ISLANDS. AT LONGER RANGE, THE EASTERN COAST OF MADAGASCAR
MAY BE THREATEN BUT THE SITUATION IS STILL TOO UNCERTAIN TO REFINE
THIS RISK FURTHER.

THIS 04 SYSTEM DOES NOT REQUIRE FOR THE MOMENT THE ELABORATION OF
REGULAR BULLETINS.

NEXT BULLETIN TOMORROW AROUND 12UTC OR EARLIER IF NECESSARY.
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