WTIO30 FMEE 290639



RSMC / TROPICAL CYCLONE CENTER / LA REUNION

TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN)



0.A WARNING NUMBER: 3/9/20172018

1.A SEVERE TROPICAL STORM  9  (FLAMBOYAN)



2.A POSITION 2018/04/29 AT 0600 UTC:

WITHIN 20 NM RADIUS OF POINT 12.4 S / 87.6 E

(TWELVE    DECIMAL FOUR   DEGREES SOUTH AND EIGHTY SEVEN    DECIMAL

SIX   DEGREES EAST)

MOVEMENT : SOUTH-WEST 17 KT



3.A DVORAK ANALYSIS: 3.5/3.5/D 1.0/12 H



4.A CENTRAL PRESSURE: 995 HPA

5.A MAX AVERAGE WIND SPEED (10 MN): 50 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: 130

34 KT NE: 90 SE: 170 SW: 170 NW: 60

48 KT NE: 40 SE: 50 SW: 50 NW: 40





7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1009 HPA / 900 KM

8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION : DEEP



1.B FORECASTS:

12H: 2018/04/29 18 UTC: 13.8 S / 85.7 E, MAX WIND=060 KT, SEVERE

TROPICAL STORM

24H: 2018/04/30 06 UTC: 14.8 S / 84.3 E, MAX WIND=060 KT, SEVERE

TROPICAL STORM

36H: 2018/04/30 18 UTC: 15.6 S / 83.7 E, MAX WIND=050 KT, SEVERE

TROPICAL STORM

48H: 2018/05/01 06 UTC: 16.8 S / 83.5 E, MAX WIND=045 KT, MODERATE

TROPICAL STORM

60H: 2018/05/01 18 UTC: 17.8 S / 83.5 E, MAX WIND=040 KT,

POST-TROPICAL DEPRESSION

72H: 2018/05/02 06 UTC: 19.6 S / 84.0 E, MAX WIND=035 KT,

POST-TROPICAL DEPRESSION



2.B LONGER-RANGE OUTLOOK :

96H: 2018/05/03 06 UTC: 23.1 S / 85.5 E, MAX WIND=030 KT,

POST-TROPICAL DEPRESSION

120H: 2018/05/04 06 UTC: 28.3 S / 89.9 E, MAX WIND=030 KT,

EXTRATROPICAL DEPRESSION



2.C ADDITIONAL INFORMATION:

T=CI=3.5+



DURING THE LAST HOURS, CONVECTIVE ACTIVITY IS MAINLY LOCATED FAR FROM

THE CENTER, AND IN A CURVED BAND, SURROUNDED BY DRY AIR, WRAPPING

RAPIDLY AROUND THE INNER CORE. FLAMBOYAN IS VERY COMPACT SYSTEM WITH

MAXIMUM WINDS VERY CLOSE TO THE CENTER. MICROWAVE IMAGERY (SSMIS

0043Z AND WINDSAT 0026Z) CONFIRM THAT, AND SHOW A WELL DEFINED EYE

ESPECIALLY IN 37GHZ. THE SYSTEM IS UPGRADED TO SEVERE TROPICAL STORM

50 KT AT MINIMUM, UNTIL THE ARRIVAL OF NEW DATA.



FLAMBOYAN SHOULD FOLLOW A CLASSIC PARABOLIC TRACK STEERED BY A

MID-TROPOSPHERE RIDGE CURRENTLY LOCATED IN THE SOUTH-EAST. 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 RATHER CONDUCIVE ENVIRONMENT.

TROPICAL CYCLONE STATUS MAY BE REACH TEMPORARILY BEFORE MONDAY

MORNING.



BY THE END OF THE NIGHT, THE INCREASE OF A NORTHWESTERLY CONSTRAINT

IN MID-TROPOPSHERE THEN HIGHER IS LIKELY TO ADVECT DRY AIR WITHIN THE

INNER CORE OF THE LOW. FROM TUESDAY, THIS VERTICAL WIND SHEAR AND THE

DECREASE OF THE OCEANIC CONTENT SOUTH OF 20S IS FORECAST TO TRIGGER

THE EXTRA-TROPICALISATION OF FLAMBOYAN. THE SYSTEM MAY THEN SLOWLY

FILL-UP WHILE TRACKING SOUTHWARD.=