WTIO30 FMEE 271236
RSMC / TROPICAL CYCLONE CENTER / LA REUNION
TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN)

0.A WARNING NUMBER: 2/15/20202021
1.A TROPICAL DEPRESSION 15

2.A POSITION 2021/03/27 AT 1200 UTC:
WITHIN 20 NM RADIUS OF POINT 10.4 S / 66.1 E
(TEN DECIMAL FOUR DEGREES SOUTH AND
SIXTY SIX DECIMAL ONE DEGREES EAST)
MOVEMENT: EAST-SOUTH-EAST 6 KT

3.A DVORAK ANALYSIS: 2.0/2.0/D 1.0/24 H

4.A CENTRAL PRESSURE: 998 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: 95 SE: 0 SW: 0 NW: 165

7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1009 HPA / 700 KM
8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION: MEDIUM

1.B FORECASTS (WINDS RADII IN KM):
12H: 2021/03/28 00 UTC: 10.7 S / 67.2 E, VENT MAX= 035 KT, MODERATE
TROPICAL STORM
28 KT NE: 85 SE: 0 SW: 75 NW: 100
34 KT NE: 45 SE: 0 SW: 0 NW: 95

24H: 2021/03/28 12 UTC: 10.9 S / 68.3 E, VENT MAX= 035 KT, MODERATE
TROPICAL STORM
28 KT NE: 75 SE: 0 SW: 165 NW: 150
34 KT NE: 45 SE: 0 SW: 0 NW: 65

36H: 2021/03/29 00 UTC: 10.1 S / 69.4 E, VENT MAX= 030 KT, TROPICAL
DEPRESSION
28 KT NE: 100 SE: 0 SW: 75 NW: 75

48H: 2021/03/29 12 UTC: 9.4 S / 70.4 E, VENT MAX= 030 KT, TROPICAL
DEPRESSION
28 KT NE: 100 SE: 0 SW: 75 NW: 75

60H: 2021/03/30 00 UTC: 8.9 S / 70.6 E, VENT MAX= 030 KT, TROPICAL
DEPRESSION
28 KT NE: 0 SE: 0 SW: 75 NW: 95

72H: 2021/03/30 12 UTC: 8.6 S / 70.6 E, VENT MAX= 025 KT, REMNANT LOW

2.B LONGER-RANGE OUTLOOK:
96H: 2021/03/31 12 UTC: 8.2 S / 69.5 E, VENT MAX= 025 KT, REMNANT LOW


2.C ADDITIONAL INFORMATION:
FT=2.0 CI=2.0+

DUE TO THE DIURNAL CYCLE AND SHEAR, CONVECTIVE ACTIVITY NEAR THE
CENTER HAS BECOME MORE FLUCTUATING AND HAS MOVED AWAY FROM THE
LOW-LEVEL CENTER. THE AMSR2 IMAGERY FROM 0902Z SHOWS HOWEVER THAT THE DEFINITION OF THE LOW LEVEL CIRCULATION CONTINUES TO IMPROVE. THE
INTENSITY REMAINS ESTIMATED AT 30 KT, ABOVE THE LAST AVAILABLE DVORAK
ESTIMATES OF 2.0 BUT IN THE CONTINUITY OF THE WINDS ESTIMATED BY THE
ASCAT PASSES THIS MORNING.

THE CURRENT AND FORECAST ENVIRONMENTAL CONDITIONS FOR THE NEXT FEW
DAYS ARE MIXED TO UNFAVORABLE: THE LOW LEVEL CONVERGENCE IS CURRENTLY
GOOD ON THE NORTHERN AND SOUTHERN SIDES OF THE SYSTEM. IT WILL BECOME
VERY INDIRECT FROM MONDAY, WHERE THE STRENGTHENING OF THE EQUATORIAL
WESTERLIES IS NOT EXPECTED TO FEED THE CIRCULATION DIRECTLY. THE
SYSTEM IS CURRENTLY EXPERIENCING AN EASTERLY SHEAR AT THE NORTHERN
EDGE OF THE UPPER LEVELS RIDGE. THIS CONSTRAINT SHOULD CONTINUE
DURING THE NEXT FEW DAYS AND EVEN STRENGTHEN FROM MONDAY ONWARDS
DEPENDING ON THE FORECAST TRACK (POSSIBLE NORTHEASTWARD TREND KEEPING
THE SYSTEM OUT OF PHASE WITH THE UPPER LEVELS RIDGE FURTHER SOUTH).
IN THIS SHEAR CONTEXT, THE MID-LEVELS DRY AIR OF AVERAGE COULD ALSO
THWART THE INTENSIFICATION. THE OCEANIC POTENTIAL IS SUFFICIENT OVER
WATERS AT 28-29C AT THE SURFACE WITHOUT HOWEVER A DEEP WARM WATER
RESERVE. CONSIDERING THE IMPROVEMENT OF THE LOW LEVEL CIRCULATION ON
THE LAST AMSR2 PASS, A SLIGHT INTENSIFICATION IS NOW ENVISAGED IN THE
SHORT TERM, BEFORE THE STRENGTHENING OF THE SHEAR. THE LAST GUIDANCE
SHOWS A LITTLE LESS SPREAD AROUND THIS INTENSITY FORECAST.

IN TERMS OF TRACK, THIS ONE IS DRIVEN OVER A GOOD PART OF THE PERIOD
BY THE DYNAMIC OF THE NEAR EQUATORIAL WESTERLY FLOW WHILE THE
SUBTROPICAL RIDGE, TO THE SOUTH, IS NOT VERY MARKED, NOT VERY THICK
AND TENDS TO WEAKEN IN THE SHORT TERM, BEFORE STRENGTHENING DURING
THE PERIOD. A SIGNIFICANT DISPERSION EXISTS AROUND THIS SCENARIO
AMONG THE GUIDANCE AND THE UNCERTAINTY ON THE FUTURE TRACK IS HIGHER
THAN NORMAL.

THIS SYSTEM HAS NO IMPACT ON THE INHABITED LANDS OF THE BASIN DURING
THE NEXT 5 DAYS.
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