WTIO30 FMEE 171910
RSMC / TROPICAL CYCLONE CENTER / LA REUNION
TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN)

0.A WARNING NUMBER: 2/8/20202021
1.A MODERATE TROPICAL STORM 8 (JOSHUA)

2.A POSITION 2021/01/17 AT 1800 UTC:
WITHIN 20 NM RADIUS OF POINT 19.2 S / 88.7 E
(NINETEEN DECIMAL TWO DEGREES SOUTH AND
EIGHTY EIGHT DECIMAL SEVEN DEGREES EAST)
MOVEMENT: WEST-SOUTH-WEST 7 KT

3.A DVORAK ANALYSIS: 3.0/3.0/D 0.5/24 H

4.A CENTRAL PRESSURE: 991 HPA
5.A MAX AVERAGE WIND SPEED (10 MN): 45 KT
RADIUS OF MAXIMUM WINDS (RMW): 24 KM

6.A EXTENSION OF WIND BY QUADRANTS (KM):
28 KT NE: 75 SE: 185 SW: 185 NW: 0
34 KT NE: 0 SE: 75 SW: 75 NW: 0

7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1005 HPA / 400 KM
8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION: DEEP

1.B FORECASTS (WINDS RADII IN KM):
12H: 2021/01/18 06 UTC: 19.4 S / 86.8 E, VENT MAX= 040 KT, MODERATE
TROPICAL STORM
28 KT NE: 55 SE: 95 SW: 100 NW: 0
34 KT NE: 0 SE: 55 SW: 55 NW: 0

24H: 2021/01/18 18 UTC: 19.2 S / 84.9 E, VENT MAX= 030 KT, REMNANT
LOW
28 KT NE: 35 SE: 85 SW: 45 NW: 0

36H: 2021/01/19 06 UTC: 19.1 S / 82.8 E, VENT MAX= 025 KT, FILLING UP

48H: 2021/01/19 18 UTC: 19.5 S / 80.5 E, VENT MAX= 025 KT, FILLING UP

60H: 2021/01/20 06 UTC: 20.2 S / 77.9 E, VENT MAX= 020 KT, FILLING UP

72H: 2021/01/20 18 UTC: 20.9 S / 75.8 E, VENT MAX= 020 KT,
DISSIPATING

2.B LONGER-RANGE OUTLOOK:
NIL


2.C ADDITIONAL INFORMATION:
T=CI=3.0-

DEEP CONVECTION HAS BEEN VERY BLURRED IN THIS SYSTEM, BUT MICROWAVE
IMAGING SHOWS THAT A CENTRAL CORE HAS FORMED. THE SCATSAT PASS OF
1330Z SHOWS WINDS OF 45 KT IN AGREEMENT WITH THE OBJECTIVE ESTIMATES
AT 40/45 KT. THE FINAL INTENSITY IS THEREFORE INCREASED TO 45KT.

IN TERMS OF TRACK FORECASTS, JOSHUA IS UNDER THE INFLUENCE OF THE END
OF THE SUBTROPICAL RIDGE PRESENT ON THE WESTERN PART OF THE
AUSTRALIAN BASIN AND WHICH IS SHIFTING WESTWARD IMPOSING A GLOBAL
DIRECTIONAL FLOW TOWARDS THE WEST. ALL THE GUIDES ARE IN GOOD
AGREEMENT WITH THIS TRACK WHICH SHOULD EVOLVE LITTLE DURING THE NEXT
48 HOURS.

FOLLOWING THIS TRACK, JOSHUA FINDS ITSELF WITH MARGINALLY FAVORABLE INTENSIFICATION CONDITIONS (LOW WIND SHEAR AND GOOD POLAR DIVERGENCE)
WITH A MAINTENANCE OR EVEN A SLIGHT INTENSIFICATION FOR THE NEXT
HOURS. TOMORROW THE MID LEVELS SHEAR WILL INCREASE AND THE DRY AIR
ALREADY PRESENT IN THE WESTERN SECTOR WILL GRADUALLY ERODE THE
CONVECTION AND WEAKEN THE SYSTEM. THE SYSTEM SHOULD THEN EVOLVE QUITE
RAPIDLY INTO A REMNANT LOW.
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