WTIO30 FMEE 211221



RSMC / TROPICAL CYCLONE CENTER / LA REUNION

TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN)



0.A WARNING NUMBER: 42/8/20152016

1.A SEVERE TROPICAL STORM  8  (FANTALA)



2.A POSITION 2016/04/21 AT 1200 UTC:

WITHIN 20 NM RADIUS OF POINT 12.6 S / 56.3 E

(TWELVE    DECIMAL SIX   DEGREES SOUTH AND FIFTY SIX    DECIMAL THREE

DEGREES EAST)

MOVEMENT : EAST-SOUTH-EAST 7 KT



3.A DVORAK ANALYSIS: 4.0/4.0/S 0.0/6 H



4.A CENTRAL PRESSURE: 985 HPA

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

RADIUS OF MAXIMUM WINDS (RMW) :28 KM



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

28 KT NE: 140 SE: 90 SW: 100 NW: 110

34 KT NE: 110 SE: 90 SW: 90 NW: 90

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





7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1008 HPA / 300 KM

8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION : DEEP



1.B FORECASTS:

12H: 2016/04/22 00 UTC: 13.1 S / 56.7 E, MAX WIND=060 KT, SEVERE

TROPICAL STORM

24H: 2016/04/22 12 UTC: 13.5 S / 56.0 E, MAX WIND=050 KT, SEVERE

TROPICAL STORM

36H: 2016/04/23 00 UTC: 13.5 S / 55.0 E, MAX WIND=045 KT, MODERATE

TROPICAL STORM

48H: 2016/04/23 12 UTC: 13.3 S / 53.2 E, MAX WIND=040 KT, MODERATE

TROPICAL STORM

60H: 2016/04/24 00 UTC: 12.5 S / 51.3 E, MAX WIND=035 KT, MODERATE

TROPICAL STORM

72H: 2016/04/24 12 UTC: 11.3 S / 49.5 E, MAX WIND=035 KT, MODERATE

TROPICAL STORM



2.B LONGER-RANGE OUTLOOK :

96H: 2016/04/25 12 UTC: 10.2 S / 46.9 E, MAX WIND=025 KT, LOW

120H: 2016/04/26 12 UTC: 9.7 S / 44.7 E, MAX WIND=020 KT, LOW



2.C ADDITIONAL INFORMATION:

T=CI=4.0



DURING THE LAST 6 HOURS, FANTALA'S CLOUD PATTERN HAS NOT MUCH

EVOLVED. SINCE 1100Z, INFRARED IMAGERY SHOWS A CDO MORE SYMETRIC WITH

COLDER CLOUD TOPS.



THE WIDE MID/UPPER TROPOPHERE MID-LATITUDE TROUGH, SOUTH OF SYSTEM,

WHICH STEERS EASTSOUTHEASTWARD FANTALA, IS FORECAST TO SHIFT

EASTWARD. BEHIND, THE ARRIVAL OF A HIGHT GEOPOTENTIAL CELL IS

EXPECTED TO BUILD A LOW/MID LEVEL SUBTROPICAL RIDGE OVER THE BASIN.

THIS PATTERN SHOULD GENERATE PROGRESSIVELY A SOUTHEASTWARD STEERING

FLOW. SO, FANTALA IS FORECASTED TO SLOW DOWN THIS NIGHT, BEND

SOUTHWARD AND THEN ACCELERATE NORTHWESTWARD FRIDAY AND SATURDAY.

FOR THE FOLLOWING DAYS, THE SYSTEM IS LIKELY TO REMAIN STEERED BY

THIS HIGH SUBTROPICAL CELL IN THE LOW AND MID TROPOSPHERE, AND SHOULD

KEEP ON A NORTH-WESTWARD TRACK. FANTALA IS EXPECTED TO TRANSIT NORTH

OF MADAGASCAR SUNDAY. BUT THE MEMBERS OF THE ECMWF ENSEMBLE SHOW A

LATITUDE DISPERSION THAT SPREADS FROM FARQUHAR ISLAND TO MASOALA

PENINSULA IN THE NORTHEASTERN COASTS OF MADAGASCAR.



FANTALA IS CURRENTLY PASSING OVER AN OCEANIC AREA PREVIOUSLY COOLED

BY ITSELF SEVERAL DAYS AGO AND WITH A NEW FORECASTED SLOW DOWN, THE

LACK OF OCEANIC ENERGY SHOULD GRADUALLY WEAKEN THE SYSTEM. MOREOVER,

THE

ATMOSPHERIC CONDITIONS SHOULD BECOME LESS FAVORABLE WITH A WEAKENING

OF THE UPPER LEVEL DIVERGENCE ESPECIALLY EVEN ON THE POLAR SIDE, THE

INCREASE OF THE NORTHERLY SHEAR MORE SIGNIFICANTLY FROM SATURDAY WHEN

IT TURNS WESTERLY, VERY DRY MID-LEVEL AIR MASS SURROUNDING THE SYSTEM

FROM FRIDAY AND BEYOND, FANTALA'S ENVIRONMENT SHOULD LEAD TO A

SUSTAINED WEAKENING OVER THE PERIOD.=