WTIO30 FMEE 301825



RSMC / TROPICAL CYCLONE CENTER / LA REUNION

TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN)



0.A WARNING NUMBER: 9/9/20172018

1.A SEVERE TROPICAL STORM  9  (FLAMBOYAN)



2.A POSITION 2018/04/30 AT 1800 UTC:

WITHIN 25 NM RADIUS OF POINT 16.4 S / 84.4 E

(SIXTEEN    DECIMAL FOUR   DEGREES SOUTH AND EIGHTY FOUR    DECIMAL

FOUR   DEGREES EAST)

MOVEMENT : SOUTH 7 KT



3.A DVORAK ANALYSIS: 3.5/4.0/W 0.5/6 H



4.A CENTRAL PRESSURE: 985 HPA

5.A MAX AVERAGE WIND SPEED (10 MN): 60 KT

RADIUS OF MAXIMUM WINDS (RMW) :46 KM



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

28 KT NE: 240 SE: 430 SW: 430 NW: 200

34 KT NE: 160 SE: 260 SW: 260 NW: 120

48 KT NE: 70 SE: 90 SW: 90 NW: 70





7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1009 HPA / 700 KM

8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION : DEEP



1.B FORECASTS:

12H: 2018/05/01 06 UTC: 18.2 S / 84.4 E, MAX WIND=055 KT, SEVERE

TROPICAL STORM

24H: 2018/05/01 18 UTC: 19.9 S / 84.5 E, MAX WIND=050 KT,

POST-TROPICAL DEPRESSION

36H: 2018/05/02 06 UTC: 21.1 S / 85.0 E, MAX WIND=045 KT,

POST-TROPICAL DEPRESSION

48H: 2018/05/02 18 UTC: 23.0 S / 86.6 E, MAX WIND=040 KT,

POST-TROPICAL DEPRESSION

60H: 2018/05/03 06 UTC: 25.5 S / 88.9 E, MAX WIND=035 KT,

POST-TROPICAL DEPRESSION

72H: 2018/05/03 18 UTC: 27.9 S / 92.6 E, MAX WIND=040 KT,

EXTRATROPICAL DEPRESSION



2.B LONGER-RANGE OUTLOOK :







2.C ADDITIONAL INFORMATION:

T=3.5 CI=4.0-



AFTER AN IMPROVEMENT EARLIER TODAY, FLAMBOYAN CLOUD PATTERN SUGGEST

MORE AND MORE CLEARLY, THE INCREASE OF THE NORTH-WESTERN UPPER

CONSTRAINT (ANALYSED AT 15Z AROUND 20 KT BY CIMSS). LAST MICROWAVE

DATA SEEM CONFIRM THAT (SSMIS 1306Z AND AMSU 1543Z) WITH A POSSIBLE

TILT BETWEEN THE UPPER AND LOWER CIRCULATIONS. WEAKENING PHASE LIKELY

STARTED. NEVERTHELESS, GIVEN PARTIAL 1543Z ASCAT SWATH AND 1220Z SMAP

DATA, MAXIMUM WINDS ARE MAINTAINED AT 60KT DUE TO INERTIA.



FLAMBOYAN DO NOT BENEFIT ANYMORE FROM A CONDUCIVE ENVIRONMENT FOR

TROPICAL DEEPENING, WITH THE INCREASE OF THE VERTICAL WIND SHEAR.

MOREOVER, OCEANIC CONTENT WILL DECAY SOUTH OF 18S. HOWEVER, DUE TO

BAROCLINIC PROCESSES WHEN INTERACTING WITH UPPER ANOMALIES, TEMPORARY

DEEPENING ARE POSSIBLE TOMORROW AND ON THURSDAY.



FLAMBOYAN IS ON ITS TRACK TO ROUND THE LOW TO MID LEVEL SUBTROPICAL

RIDGE LOCATED TO IT EAST WITH A GRADUAL SOUTH-EASTWARDS TURN EXPECTED

DURING THE WHOLE FORECAST PERIOD. FROM WEDNESDAY, IT SHOULD

ACCELERATE AHEAD OF A DEEP MID-LATITUDES TROUGH.=