WTIO30 FMEE 010020



RSMC / TROPICAL CYCLONE CENTER / LA REUNION

TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN)



0.A WARNING NUMBER: 20/5/20172018

1.A INTENSE TROPICAL CYCLONE  5  (CEBILE)



2.A POSITION 2018/02/01 AT 0000 UTC:

WITHIN 15 NM RADIUS OF POINT 15.5 S / 76.5 E

(FIFTEEN    DECIMAL FIVE   DEGREES SOUTH AND SEVENTY SIX    DECIMAL

FIVE   DEGREES EAST)

MOVEMENT : WEST 2 KT



3.A DVORAK ANALYSIS: 5.5/5.5/D 1.0/6 H



4.A CENTRAL PRESSURE: 955 HPA

5.A MAX AVERAGE WIND SPEED (10 MN): 90 KT

RADIUS OF MAXIMUM WINDS (RMW) :37 KM



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

28 KT NE: 240 SE: 330 SW: 410 NW: 200

34 KT NE: 200 SE: 270 SW: 190 NW: 180

48 KT NE: 140 SE: 170 SW: 130 NW: 120

64 KT NE: 90 SE: 100 SW: 100 NW: 90



7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1007 HPA / 1000 KM

8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION : DEEP



1.B FORECASTS:

12H: 2018/02/01 12 UTC: 15.9 S / 75.7 E, MAX WIND=095 KT, INTENSE

TROPICAL CYCLONE

24H: 2018/02/02 00 UTC: 16.5 S / 75.4 E, MAX WIND=085 KT, TROPICAL

CYCLONE

36H: 2018/02/02 12 UTC: 17.3 S / 75.5 E, MAX WIND=085 KT, TROPICAL

CYCLONE

48H: 2018/02/03 00 UTC: 17.8 S / 76.0 E, MAX WIND=080 KT, TROPICAL

CYCLONE

60H: 2018/02/03 12 UTC: 18.4 S / 77.4 E, MAX WIND=070 KT, TROPICAL

CYCLONE

72H: 2018/02/04 00 UTC: 19.4 S / 78.9 E, MAX WIND=060 KT, SEVERE

TROPICAL STORM



2.B LONGER-RANGE OUTLOOK :

96H: 2018/02/05 00 UTC: 22.0 S / 80.4 E, MAX WIND=050 KT, SEVERE

TROPICAL STORM

120H: 2018/02/06 00 UTC: 25.1 S / 80.6 E, MAX WIND=050 KT,

POST-TROPICAL DEPRESSION



2.C ADDITIONAL INFORMATION:

T=CI=5.5



OVER THE LAST 6 HOURS, CONVECTION STRENGTHENED IN THE WESTERN

SEMI-CIRCLE EVEN IF THE CONVECTION RING SURROUNDING CEBILE'S EYE

REMAINS NARROWER THERE. THE EYE ALSO TIGHTENED SLIGHTLY, ALLOWING THE

RSMC DVORAK ESTIMATES TO INCREASE. MW IMAGES FROM THE AMSR2 2007Z

SWATH REVEALS A FEW WEAKNESSES IN THE CONVECTION RING NOW BUT THE

CORE STRUCTURE OF CEBILE STILL REMAINS SOLID.



CEBILE CLEARLY SLOWED DOWN, AND EVEN STOPPED OVER THE LAST 2 HOURS.

THE SYSTEM IS CAUGHT BETWEEN A SUBTROPICAL RIDGE IN THE SOUTH-WEST

AND THE NEAR-EQUATORIAL RIDGE IN THE NORTH-EAST. THESE TWO SYNOPTIC

STRUCTURES ARE DRIVING OPPOSITE STEERING FLOWS. TODAY, THE

SUBTROPICAL RIDGE IS EXPECTED TO WEAKEN AND SLIDE WESTWARD. THE NEAR

EQUATORIAL RIDGE SHOULD THUS TAKE OVER CEBILE'S STEERING FLOW. THIS

CHANGE WILL LEAD TO A SHARP SOUTH-EASTWARD TURN FOLLOWED BY A GRADUAL

ACCELERATION. THE GUIDANCE DISPERSION BECAME RELATIVELY LOW IN THE

LAST MODELS RUNS. AFTER THE TURN, THE MAIN UNCERTAINTY CONCERNS THE

CYCLONE'S SPEED. THE CURRENT TRACK FORECAST IS MOSTLY BASED ON A

CONSENSUS OF RECENT IFS AND GFS GUIDANCE.



CEBILE IS CURRENTLY WITHIN QUASI-PERFECT CONDITIONS CONCERNING WIND

SHEAR, UPPER DIVERGENCE AND OCEANIC HEAT CONTENT. A SLIGHT INTENSITY

GAIN IS STILL POSSIBLE AT SHORT RANGE, UNLESS THE CONVECTION BECOMES

TOO AFFECTED BY DRY AIR ON CONVECTION OR THE UNDERLYING WATERS COOLED

BY A LONGER STOP THAN EXPECTED. FROM FRIDAY, EQUATORWARD UPPER LEVEL

DIVERGENCE IS EXPECTED TO WEAKEN AND A WESTERLY WINDSHEAR CONSTRAINT

BEGINS TO APPEAR IN THE EVENING. FROM SATURDAY, A ROSSBY WAVE

BREAKING LOCATED WEST OF THE SYSTEM WILL QUICKLY STRENGTHEN THE

WESTERLY THEN NORTHWESTWERLY WINDSHEAR. CEBILE'S INTENSITY IS

FORECAST TO QUICKLY DROP, AS IT WILL ALSO TRACK OVER COOLER SURFACE

SEA TEMPERATURES. LASTLY, THE SYSTEM MAY THEN BEGIN ITS

EXTRA-TROPICALISATION PHASE AS THE UPPER TROUGH MATERIALIZING THE

ROSSBY WAVE IS COMING CLOSER TO THE SYSTEM'S CORE.=