WTIO30 FMEE 281217
RSMC / TROPICAL CYCLONE CENTER / LA REUNION
TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN)

0.A WARNING NUMBER: 3/9/20202021
1.A TROPICAL DEPRESSION 9

2.A POSITION 2021/01/28 AT 1200 UTC:
WITHIN 30 NM RADIUS OF POINT 18.0 S / 84.8 E
(EIGHTEEN DECIMAL ZERO DEGREES SOUTH AND
EIGHTY FOUR DECIMAL EIGHT DEGREES EAST)
MOVEMENT: WEST 15 KT

3.A DVORAK ANALYSIS: NIL
4.A CENTRAL PRESSURE: 1003 HPA
5.A MAX AVERAGE WIND SPEED (10 MN): 30 KT
RADIUS OF MAXIMUM WINDS (RMW): NIL

6.A EXTENSION OF WIND BY QUADRANTS (KM):
28 KT NE: 0 SE: 205 SW: 165 NW: 0

7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1007 HPA / 700 KM
8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION: SHALLOW

1.B FORECASTS (WINDS RADII IN KM):
12H: 2021/01/29 00 UTC: 17.5 S / 80.7 E, VENT MAX= 030 KT, TROPICAL
DEPRESSION
28 KT NE: 0 SE: 150 SW: 150 NW: 0

24H: 2021/01/29 12 UTC: 16.8 S / 76.9 E, VENT MAX= 025 KT, FILLING UP

36H: 2021/01/30 00 UTC: 16.0 S / 73.4 E, VENT MAX= 025 KT, FILLING UP

48H: 2021/01/30 12 UTC: 15.6 S / 70.2 E, VENT MAX= 020 KT, FILLING UP

60H: 2021/01/31 00 UTC: 15.2 S / 66.8 E, VENT MAX= 020 KT, FILLING UP

72H: 2021/01/31 12 UTC: 14.8 S / 64.5 E, VENT MAX= 020 KT, FILLING UP

2.B LONGER-RANGE OUTLOOK:
96H: 2021/02/01 12 UTC: 14.3 S / 59.6 E, VENT MAX= 015 KT, FILLING UP

120H: 2021/02/02 12 UTC: 14.2 S / 56.0 E, VENT MAX= 015 KT, FILLING
UP

2.C ADDITIONAL INFORMATION:
THE CLOUD CONFIGURATION IS A SHEARED CONFIGURATION.CONVECTIVE
ACTIVITY YET PRESENT AT THE END OF THE NIGHT, FAR FROM THE CENTER IN
THE SOUTHERN QUADRANT OF THE CIRCULATION HAS CLEARLY WEAKEN AND
REMAINS VERY FLUCTUATING.
THE LOW LEVELS CLOCKWISE CIRCULATION, ALWAYS COMPLETELY EXPOSED ON
THE VISIBLE SATELLITE IMAGES, SEEMS NOW ILL-DEFINED.
ACCORDING TO THE LAST ASCAT-C PASS OF 03UTC, IT APPEARS THAT THE
STRONGEST WINDS ARE OF THE ORDER OF 30KT AND ARE LOCATED ONLY FAR
FROM THE CENTREWITHIN THE GRADIANT IN THE SOUTHERN SEMICIRCLE OF THE CIRCULATION.
THE 09 SYSTEM IS IN AN ENVIRONMENT UNFAVORABLE TO INTENSIFICATION
WITH DRY AIR PRESENT AT HIGH ALTITUDE (MAINLY IN THE WESTERN AND
NORTHERN SECTOR). THE NORTHERLY VERTICAL WIND SHEAR HAFROM SUNDAYS
WEAKEN A BIT ACCORDING TO THE CIMMS DATA, BUT CONTRIBUTS A LITTLE
MORE TO LOCALIZE THE CONVECTION ONLY IN THE SOUTHERN QUADRANT.

IN TERMS OF TRACK FORECAST, THE 09 SYSTEM IS UNDER THE INFLUENCE OF
THE SUBTROPICAL RIDGE WHICH IS LOCATED IN THE SOUTHEAST OF THE BASIN
AND WHICH IS WELL PRESENT AT ALL LEVELS OF THE ATMOSPHERE. IN THE
COURSE OF THE TIMES, THIS RIDGE STRENGTHENS AND MAINTAINS A
WEST-NORTHWEST DIRECTIONAL FLOW ON THE TROPICAL DEPRESSION WHICH WILL
KEEP GLOBALLY THIS TRACK THROUGHOUT ITS LIFE. ALL THE GUIDES ARE IN
GOOD AGREEMENT ON THIS SCENARIO.

AS REGARDS THE FORECAST OF INTENSITY, THE 09 SYSTEM IS EXPECTED TO
REMAIN IN AN ENVIRONMENT UNFAVOURABLE TO INTENSIFICATION FOR THE NEXT
DAYS:
DESPITE THE WEAKNESS OF VERTICAL WIND SHEAR FOR THE NEXT 12H, IT
SHOULD STRENGTHEN AGAIN UNTIL MONDAY.
IN ADDITION, DRY AIR WILL REMAIN PRESENT ABOVE THE CICULATION IN THE
MIDDLE TROPOSPHERE AND HIGHER AND SHOULD BE THE MAIN LIMITING FACTOR
TO THE INTENSIFICATION OF THE SYSTEM.
THE MAXIMUM WINDS WILL REMAIN CLOSE TO 25/30 KNOTS BEFORE WEAKENING PROGRESSIVELY DURING THE WEEK-END TO LET THE SYSTEM FILL UP
PROGRESSIVELY DURING ITS TRANSIT NORTH OF THE MASCARENES ISLANDS.

FOR THE MOMENT, THIS LOW INTENSITY SYSTEM DOES NOT PRESENT ANY
PARTICULAR RISK FOR THE INHABITED LANDS.

THIS IS THE LAST WARNING ABOUT THIS SYSTEM UNLESS REINTENSIFIED.
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