WTIO30 FMEE 201222
RSMC / TROPICAL CYCLONE CENTER / LA REUNION
TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN)

0.A WARNING NUMBER: 1/4/20202021
1.A ZONE OF DISTURBED WEATHER 4

2.A POSITION 2020/12/20 AT 1200 UTC:
WITHIN 20 NM RADIUS OF POINT 12.6 S / 65.5 E
(TWELVE DECIMAL SIX DEGREES SOUTH AND
SIXTY FIVE DECIMAL FIVE DEGREES EAST)
MOVEMENT: SOUTH-EAST 4 KT

3.A DVORAK ANALYSIS: 1.5/1.5/S 0.0/24 H

4.A CENTRAL PRESSURE: 1008 HPA
5.A MAX AVERAGE WIND SPEED (10 MN): 20 KT
RADIUS OF MAXIMUM WINDS (RMW): 352 KM

6.A EXTENSION OF WIND BY QUADRANTS (KM):
NIL

7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1010 HPA / 1200 KM
8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION: SHALLOW

1.B FORECASTS (WINDS RADII IN KM):
12H: 2020/12/21 00 UTC: 13.0 S / 65.3 E, VENT MAX= 020 KT, ZONE OF
DISTURBED WEATHER

24H: 2020/12/21 12 UTC: 13.4 S / 64.4 E, VENT MAX= 025 KT, TROPICAL
DISTURBANCE

36H: 2020/12/22 00 UTC: 13.8 S / 63.2 E, VENT MAX= 025 KT, TROPICAL
DISTURBANCE

48H: 2020/12/22 12 UTC: 14.1 S / 62.0 E, VENT MAX= 030 KT, TROPICAL
DEPRESSION
28 KT NE: 85 SE: 140 SW: 165 NW: 45

60H: 2020/12/23 00 UTC: 14.1 S / 60.8 E, VENT MAX= 030 KT, TROPICAL
DEPRESSION
28 KT NE: 85 SE: 140 SW: 165 NW: 45

72H: 2020/12/23 12 UTC: 14.2 S / 59.9 E, VENT MAX= 030 KT, TROPICAL
DEPRESSION
28 KT NE: 95 SE: 140 SW: 165 NW: 45

2.B LONGER-RANGE OUTLOOK:
96H: 2020/12/24 12 UTC: 14.6 S / 58.2 E, VENT MAX= 035 KT, MODERATE
TROPICAL STORM
28 KT NE: 140 SE: 140 SW: 165 NW: 85
34 KT NE: 130 SE: 130 SW: 75 NW: 75

120H: 2020/12/25 12 UTC: 14.9 S / 55.0 E, VENT MAX= 040 KT, MODERATE
TROPICAL STORM
28 KT NE: 155 SE: 155 SW: 165 NW: 85
34 KT NE: 150 SE: 150 SW: 75 NW: 75

2.C ADDITIONAL INFORMATION:

WITHIN THE MONSOON TROUGH, A LARGE LOW-PRESSURE CIRCULATION HAS
DEVELOPED IN THE NORTH-EAST OF THE MASCARENE ISLANDS AND WAS
MONITORED THROUGH THE CYCLONIC ACTIVITY BULLETINS (ITCZ) FOR THE LAST
TWO DAYS. THIS FAIRLY WIDE CIRCULATION IS ASSOCIATED WITH A MODERATE
TO STRONG CONVECTIVE ACTIVITY BUT QUITE FLUCTUATING. OVER THE LAST 24
HOURS, THE CONFIGURATION HAS CHANGED FROM CONVECTIVE ACTIVITY MAINLY
ON THE NORTH FACE OF THE MONSOON TROUGH NEAR THIS ZONE OF DISTURBED
WEATHER, TO A TDC AND THEN RECENTLY TO A CURVED BAND FOLLOWING THE
BREAKDOWN OF THE CENTRAL CONVECTION. IN THIS NEW CONFIGURATION, A
VALUE OF 1.5 IN DVORAK ANALYSIS COULD BE GIVEN ESTIMATING WINDS OF
THE ORDER OF 20/25KT. THE LAST AVAILABLE ASCAT PASSES ALLOW TO
VALIDATE THESE VALUES AT 20KT QUITE FAR FROM THE CENTER, ESTIMATED
AROUND 12.6AOS/65.5AOE. THIS ZONE OF DISTURBED WEATHER THUS DEFINES
THE 4TH SYSTEM OF THE 2020/2021 SEASON.

IN TERMS OF FORECASTING, THE TRACK AND INTENSITY FORECASTING ARE
CLOSELY LINKED. WITH A CIRCULATION THAT IS NOT YET WELL CONSOLIDATED
AND LOCATED AT THE SOUTHERN EDGE OF A STRONG EASTERLY WIND SHEAR THAT
IS DISTURBING THE SYSTEM, IT WILL TAKE ALMOST TWO DAYS FOR THE SYSTEM
TO ORGANIZE ITSELF. IN THIS CURRENT SLOW EVOLUTION PERSPECTIVE
CHOSEN, THE ZONE OF DISTURBED WEATHER WILL MOVE SLOWLY IN A GENERAL
WESTERLY DIRECTION DURING THE NEXT FEW DAYS UNDER THE INFLUENCE OF
THE LOW LEVEL FLOW STEERED IN THE HIGH PRESSURES FURTHER SOUTH. SOME
MODELS PREDICT A FASTER CONSOLIDATION OF THE CIRCULATION, PLACING THE
STEERING FLOW HIGHER UP, GIVING A WESTWARD TRACK SHIFTED A LITTLE
FURTHER NORTH THAN THE ONE CHOSEN BY THE RSMC.

DURING THIS MOVEMENT, THE 04 SYSTEM WILL INTENSIFY VERY SLOWLY,
PASSING TO THE NORTH OF THE MASCARENE ISLANDS AT THE STAGE OF
TROPICAL DEPRESSION AND THEN OF MODERATE TROPICAL STORM AT THE
APPROACH OF CHRISTMAS.

DUE TO ITS INTENSITY, THIS METEOR DOES NOT PRESENT A THREAT TO THE
INHABITED LANDS AT THE MOMENT, BUT ITS PROXIMITY REQUIRES A
PARTICULAR MONITORING, JUSTIFYING THE EARLY ELABORATION OF THESE
BULLETINS. THIS 04 SYSTEM DOES NOT REQUIRE FOR THE MOMENT THE
ELABORATION OF REGULAR BULLETINS.

NEXT BULLETIN TOMORROW AROUND 12UTC OR EARLIER IF NECESSARY.
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