WTIO30 FMEE 291255



RSMC / TROPICAL CYCLONE CENTER / LA REUNION

TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN)



0.A WARNING NUMBER: 4/9/20172018

1.A SEVERE TROPICAL STORM  9  (FLAMBOYAN)



2.A POSITION 2018/04/29 AT 1200 UTC:

WITHIN 25 NM RADIUS OF POINT 12.9 S / 86.1 E

(TWELVE    DECIMAL NINE   DEGREES SOUTH AND EIGHTY SIX    DECIMAL ONE

DEGREES EAST)

MOVEMENT : WEST-SOUTH-WEST 15 KT



3.A DVORAK ANALYSIS: 4.0/4.0/D 1.0/12 H



4.A CENTRAL PRESSURE: 988 HPA

5.A MAX AVERAGE WIND SPEED (10 MN): 55 KT

RADIUS OF MAXIMUM WINDS (RMW) :28 KM



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

28 KT NE: 190 SE: 280 SW: 310 NW: 170

34 KT NE: 90 SE: 190 SW: 190 NW: 70

48 KT NE: 50 SE: 60 SW: 60 NW: 50





7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1007 HPA / 500 KM

8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION : DEEP



1.B FORECASTS:

12H: 2018/04/30 00 UTC: 14.2 S / 84.4 E, MAX WIND=065 KT, TROPICAL

CYCLONE

24H: 2018/04/30 12 UTC: 15.2 S / 83.7 E, MAX WIND=055 KT, SEVERE

TROPICAL STORM

36H: 2018/05/01 00 UTC: 16.4 S / 83.4 E, MAX WIND=045 KT, MODERATE

TROPICAL STORM

48H: 2018/05/01 12 UTC: 17.6 S / 83.3 E, MAX WIND=040 KT,

POST-TROPICAL DEPRESSION

60H: 2018/05/02 00 UTC: 19.3 S / 83.6 E, MAX WIND=040 KT,

POST-TROPICAL DEPRESSION

72H: 2018/05/02 12 UTC: 20.7 S / 84.3 E, MAX WIND=035 KT,

POST-TROPICAL DEPRESSION



2.B LONGER-RANGE OUTLOOK :

96H: 2018/05/03 12 UTC: 25.3 S / 87.1 E, MAX WIND=030 KT,

POST-TROPICAL DEPRESSION





2.C ADDITIONAL INFORMATION:

T=CI=4.0-



THE DRY AIR MASS LOCATED THIS MORNING AROUND THE CORE, APPEARS TO

HAVE BEEN COMPENSATED BY THE CONVECTIVE ACTIVITY. CURRENTLY, THE

COMPACT INNER CIRCULATION IS EMBEDDED WITHIN A BROAD AREA OF DEEP

CONVECTION AS IN THE 1051Z GMI SWATH.THEREFORE, THE DEEPENING THAT

SLOWED THIS MORNING, APPARENTLY RESUMED.



DURING THE NEXT HOURS, WITH A HIGHER STEERING LEVEL AND THE WEAKENING

OF THE RIDGE AT SOUTH, THE SYSTEM IS FORECAST TO BEND SOUTH-WESTWARD

THEN SOUTHWARD. SO, FLAMBOYAN SHOULD FOLLOW A CLASSIC PARABOLIC TRACK

CIRCUMVENTING BY WEST THE RIDGE. THE DISPERSION OF THE AVAILABLE

DETERMINISTIC AND ENSEMBLE MODELS INCREASES FROM TUESDAY, AS THE

ARRIVAL OF A MID-LATITUDES TROUGH IN THE SOUTH-WEST COULD ACCELERATE

(OR NOT) THE EVACUATION OF THE SYSTEM TOWARDS THE SOUTH-EAST. THE

RSMC TRACK FORECAST IS BASED ON A MODEL CONSENSUS.



FLAMBOYAN IS CURRENTLY LOCATED UNDER THE AXIS OF THE NEAR EQUATORIAL

UPPER RIDGE, WINDSHEAR THUS REMAINS LOW AND THE UPPER DIVERGENCE

STRONG. GIVEN ITS SMALL SIZE, THE SYSTEM MAY UNDERGO RAPID INTENSITY

CHANGES DURING THE NEXT HOURS , IN THIS CONDUCIVE ENVIRONMENT.

TROPICAL CYCLONE STATUS MAY BE REACH TEMPORARILY TONIGHT.



BY TOMORROW MORNING, THE INCREASE OF A NORTHWESTERLY CONSTRAINT IN

MID-TROPOPSHERE THEN HIGHER MAY ADVECT RAPIDLY DRY AIR WITHIN THE

SMALL INNER CORE, TRIGERRING A RATHER QUICK WEAKENING. FROM TUESDAY,

THIS VERTICAL WIND SHEAR AND THE DECREASE OF THE OCEANIC CONTENT

SOUTH OF 20S IS FORECAST TO START THE EXTRA-TROPICALISATION OF

FLAMBOYAN. THE SYSTEM MAY THEN SLOWLY FILL-UP WHILE TRACKING

SOUTHWARD.=