WTIO30 FMEE 201931 CCA
***************CORRECTIVE**************
RSMC / TROPICAL CYCLONE CENTER / LA REUNION
TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN)

0.A WARNING NUMBER: 4/16/20202021
1.A MODERATE TROPICAL STORM 16 (JOBO)

2.A POSITION 2021/04/20 AT 1800 UTC:
WITHIN 30 NM RADIUS OF POINT 10.3 S / 49.8 E
(TEN DECIMAL THREE DEGREES SOUTH AND
FORTY NINE DECIMAL EIGHT DEGREES EAST)
MOVEMENT: WEST 11 KT

3.A DVORAK ANALYSIS: 2.5/2.5/D 1.0/24 H

4.A CENTRAL PRESSURE: 999 HPA
5.A MAX AVERAGE WIND SPEED (10 MN): 40 KT
RADIUS OF MAXIMUM WINDS (RMW): 24 KM

6.A EXTENSION OF WIND BY QUADRANTS (KM):
28 KT NE: 75 SE: 150 SW: 165 NW: 95
34 KT NE: 35 SE: 75 SW: 75 NW: 55

7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1010 HPA / 200 KM
8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION: DEEP

1.B FORECASTS (WINDS RADII IN KM):
12H: 2021/04/21 06 UTC: 9.8 S / 48.1 E, VENT MAX= 050 KT, SEVERE
TROPICAL STORM
28 KT NE: 65 SE: 100 SW: 110 NW: 85
34 KT NE: 55 SE: 30 SW: 55 NW: 45
48 KT NE: 45 SE: 20 SW: 45 NW: 35

24H: 2021/04/21 18 UTC: 9.7 S / 46.8 E, VENT MAX= 065 KT, TROPICAL
CYCLONE
28 KT NE: 65 SE: 100 SW: 100 NW: 110
34 KT NE: 55 SE: 35 SW: 55 NW: 55
48 KT NE: 45 SE: 30 SW: 45 NW: 45
64 KT NE: 20 SE: 20 SW: 20 NW: 35

36H: 2021/04/22 06 UTC: 9.6 S / 45.6 E, VENT MAX= 065 KT, TROPICAL
CYCLONE
28 KT NE: 65 SE: 110 SW: 95 NW: 95
34 KT NE: 55 SE: 30 SW: 55 NW: 55
48 KT NE: 45 SE: 20 SW: 45 NW: 45
64 KT NE: 20 SE: 10 SW: 20 NW: 35

48H: 2021/04/22 18 UTC: 9.4 S / 44.5 E, VENT MAX= 050 KT, SEVERE
TROPICAL STORM
28 KT NE: 65 SE: 100 SW: 110 NW: 85
34 KT NE: 55 SE: 30 SW: 55 NW: 45
48 KT NE: 45 SE: 20 SW: 45 NW: 35

60H: 2021/04/23 06 UTC: 9.1 S / 43.7 E, VENT MAX= 040 KT, MODERATE
TROPICAL STORM
28 KT NE: 45 SE: 85 SW: 85 NW: 85
34 KT NE: 35 SE: 10 SW: 20 NW: 35

72H: 2021/04/23 18 UTC: 9.0 S / 42.8 E, VENT MAX= 035 KT, MODERATE
TROPICAL STORM
28 KT NE: 45 SE: 75 SW: 85 NW: 85
34 KT NE: 35 SE: 10 SW: 10 NW: 35

2.B LONGER-RANGE OUTLOOK:
96H: 2021/04/24 18 UTC: 8.6 S / 41.1 E, VENT MAX= 025 KT, FILLING UP

120H: 2021/04/25 18 UTC: 7.9 S / 39.4 E, VENT MAX= 020 KT, OVERLAND
DEPRESSION

2.C ADDITIONAL INFORMATION:
T=CI=2.5+

DURING THE LAST 6 HOURS, CONVECTION HAS CLEARLY INTENSIFIED, WITH
STRONG CONVECTIVE BURSTS IN THE VICINITY OF THE SURFACE CENTER (CDO
WITH CLOUD TOPS TEMPERATURES BELOW -80C). RECENT MICROWAVE PASSES
(SSMIS 1532Z) SHOW AN INCREASING ORGANIZATION. WITH WINDS MEASURED AT
30/35 KT THIS MORNING AND TAKING INTO ACCOUNT THE CURRENT
INTENSIFICATION OF THE SYSTEM, WINDS ARE NOW ESTIMATED AT 40 KT AT
1800Z. THE STAGE OF MODERATE TROPICAL STORM IS THUS CONFIRMED, WITH A
SYSTEM NAMED "JOBO" SINCE 1500Z.

THE WESTWARD TO WEST-NORTHWESTWARD TRACK IS CONFIRMED, WITH A FAIRLY
GOOD AGREEMENT BETWEEN MODELS FOR THE NEXT 48 HOURS. THE SYSTEM IS
MOVING ON THE NORTHERN SIDE OF THE LOW TROPOSPHERIC SUBTROPICAL RIDGE
AND SHOULD PASS NEAR THE SOUTH OF THE OUTER ISLANDS OF THE SEYCHELLES
DURING WEDNESDAY AND THE FOLLOWING NIGHT WHILE GRADUALLY SLOWING
DOWN. FROM THURSDAY ONWARDS, UNCERTAINTY ABOUT THE TRACK INCREASES
WITH STEERING FLOWS BECOMING WEAKER AND THE TRACK ALSO DEPENDING ON
THE INTENSITY THAT THE SYSTEM WILL HAVE AT THAT TIME. THE PRESENT
FORECAST IS BASED ON A MEDIAN SCENARIO BUT WILL HAVE TO BE CONFIRMED.

ENVIRONMENTAL CONDITIONS REMAIN RELATIVELY FAVORABLE FOR DEVELOPMENT
IN THE SHORT RUN, UNTIL WEDNESDAY NIGHT : IN THE LOW LAYERS, THE
TRADEWINDS SURGE IS REINFORCED BY THE ACCELERATION RELATED TO THE
NORTHERN BYPASS OF MADAGASCAR WHICH INCREASES THE POLEWARD
CONVERGENCE. MEANWHILE, THE EQUATORIAL CONVERGENCE REMAINS WEAK TO
VERY WEAK, WHICH BRINGS UNCERTAINTY ON THE MORE OR LESS EFFECTIVE
CONSOLIDATION OF THE STORM'S CORE. ALOFT, THE DEEP-LAYER
SOUTH-WESTERN SHEAR IS DECREASING AND DOES NOT SEEM TO AFFECT TOO
MUCH THE DEVELOPMENT OF THE SYSTEM IN THE SHORT RUN, IN AN
ENVIRONMENT REMAINING SUFFICIENTLY MOIST AND UNDER GOOD UPPER
DIVERGENCE. ON WEDNESDAY EVENING, THIS UPPER DIVERGENCE WILL EVEN
INCREASE A BIT AT THE EDGE OF A SUBTROPICAL TROUGH CIRCULATING
FURTHER SOUTH WHICH COULD ALLOW THE SYSTEM TO REACH TROPICAL CYCLONE
STAGE. BUT THEN, FROM THURSDAY ONWARDS, A NORTH-WESTERN SHEAR SHOULD
SET UP AND SHOULD ATTACK THE CONVECTIVE CORE BY ADVECTING DRY AIR
OVER IT. THIS SHOULD LEAD TO THE WEAKENING OF THE SYSTEM IN THE
SECOND PART OF THE WEEK.
THE SMALL SIZE OF THE STORM'S CORE MAKING IT VERY REACTIVE TO ITS
ENVIRONMENT INDUCES A HIGHER THAN AVERAGE UNCERTAINTY ON THE PRESENT
INTENSITY FORECAST.

POSSIBLE IMPACTS EXPECTED ON THE OUTER ISLANDS OF THE SEYCHELLES
(ASTOVE, COSMOLEDO, ALDABRA) :
-VERY INTENSE RAINFALL THAT COULD EXCEED 150 TO 200 MM IN 24 HOURS.
-STRONG WINDS (DEPENDING ON THE EXACT TRACK OF THE STORM): CYCLONIC
CONDITIONS (GUSTS OVER 150 KM/H) CAN'T BE RULED OUT.
-DANGEROUS SEA CONDITIONS: WAVES EXCEEDING 5 METERS LOCALLY.
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