WTIO30 FMEE 181834
RSMC / TROPICAL CYCLONE CENTER / LA REUNION
TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN)

0.A WARNING NUMBER: 6/8/20202021
1.A TROPICAL DEPRESSION 8 (JOSHUA)

2.A POSITION 2021/01/18 AT 1800 UTC:
WITHIN 20 NM RADIUS OF POINT 19.4 S / 85.6 E
(NINETEEN DECIMAL FOUR DEGREES SOUTH AND
EIGHTY FIVE DECIMAL SIX DEGREES EAST)
MOVEMENT: WEST 7 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): 65 KM

6.A EXTENSION OF WIND BY QUADRANTS (KM):
28 KT NE: 0 SE: 0 SW: 95 NW: 0

7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1007 HPA / 400 KM
8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION: DEEP

1.B FORECASTS (WINDS RADII IN KM):
12H: 2021/01/19 06 UTC: 19.2 S / 83.2 E, VENT MAX= 025 KT, FILLING UP

24H: 2021/01/19 18 UTC: 19.6 S / 80.9 E, VENT MAX= 025 KT, FILLING UP

36H: 2021/01/20 06 UTC: 20.4 S / 78.7 E, VENT MAX= 020 KT,
DISSIPATING

48H: 2021/01/20 18 UTC: 21.2 S / 76.7 E, VENT MAX= 020 KT,
DISSIPATING



2.B LONGER-RANGE OUTLOOK:
NIL


2.C ADDITIONAL INFORMATION:
T=CI=NIL

THE NORTHWESTERN ALTITUDE SHEAR IS WELL PRESENT AS WELL AS DRY AIR.
THESE TWO FACTORS HAVE OVERCOME THE CONVECTION ASSOCIATED WITH JOSHUA
WHICH HAS TOTALLY COLLAPSED DURING THE LAST 6 HOURS. THE LAST ASCAT
SWATH OF 1536UTC STILL PROVIDES WINDS OF 30KT IN THE SOUTHWEST
QUADRANT.

NO CHANGE IN TERMS OF TRACK FORECAST: JOSHUA IS UNDER THE INFLUENCE
OF THE WESTERN EXTREMITY OF THE SUBTROPICAL RIDGE CENTERED ON THE
WESTERN PART OF THE AUSTRALIAN BASIN AND WHICH IS SHIFTING WESTWARD
IMPOSING A GLOBAL WEST-SOUTHWEST DIRECTIONAL FLOW. ALL THE GUIDES ARE
IN GOOD AGREEMENT ON THIS TRACK WHICH SHOULD EVOLVE LITTLE DURING THE
NEXT 48 HOURS.

THE SHEAR ALREADY PRESENT IN ALTITUDE WILL ALSO INCREASE IN THE
AVERAGE TROPOSPHERE. THUS, THE DRY AIR ALREADY PRESENT IN THE WESTERN
SECTOR WILL CONTINUE TO PROGRESSIVELY ERODE THE HOT CORE AND WEAKEN
THE SYSTEM. THE SYSTEM SHOULD THEN EVOLVE QUITE RAPIDLY IN DEPRESSION DISSIPATING.
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