WTIO30 FMEE 041230



RSMC / TROPICAL CYCLONE CENTER / LA REUNION

TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN)



0.A WARNING NUMBER: 19/1/20172018

1.A SEVERE TROPICAL STORM  1  (AVA)



2.A POSITION 2018/01/04 AT 1200 UTC:

WITHIN 20 NM RADIUS OF POINT 17.4 S / 51.5 E

(SEVENTEEN    DECIMAL FOUR   DEGREES SOUTH AND FIFTY ONE    DECIMAL

FIVE   DEGREES EAST)

MOVEMENT : WEST 5 KT



3.A DVORAK ANALYSIS: 4.0/4.0/D 1.0/18 H



4.A CENTRAL PRESSURE: 983 HPA

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

RADIUS OF MAXIMUM WINDS (RMW) :37 KM



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

28 KT NE: 190 SE: 190 SW: 190 NW: 110

34 KT NE: 130 SE: 130 SW: 130 NW: 90

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





7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1004 HPA / 1200 KM

8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION : DEEP



1.B FORECASTS:

12H: 2018/01/05 00 UTC: 17.6 S / 50.3 E, MAX WIND=060 KT, SEVERE

TROPICAL STORM

24H: 2018/01/05 12 UTC: 18.3 S / 49.4 E, MAX WIND=065 KT, TROPICAL

CYCLONE

36H: 2018/01/06 00 UTC: 19.3 S / 48.8 E, MAX WIND=050 KT, OVERLAND

DEPRESSION

48H: 2018/01/06 12 UTC: 20.7 S / 48.7 E, MAX WIND=035 KT, MODERATE

TROPICAL STORM

60H: 2018/01/07 00 UTC: 22.5 S / 48.6 E, MAX WIND=040 KT, MODERATE

TROPICAL STORM

72H: 2018/01/07 12 UTC: 23.7 S / 48.7 E, MAX WIND=045 KT, MODERATE

TROPICAL STORM



2.B LONGER-RANGE OUTLOOK :

96H: 2018/01/08 12 UTC: 25.6 S / 47.7 E, MAX WIND=045 KT, MODERATE

TROPICAL STORM

120H: 2018/01/09 12 UTC: 27.7 S / 46.9 E, MAX WIND=040 KT, MODERATE

TROPICAL STORM



2.C ADDITIONAL INFORMATION:

T=CI=4.0-



OVER THE LAST 6 HOURS, DEEP CONVECTION ALWAYS ORGANIZED INTO CDO

STRUCTURE HAS BECOME COLDER, ATTESTING THE INTENSIFICATION OF THE

SYSTEM IS GOING ON.



TODAY, THE ARRIVAL OF A FAST RIDGE SOUTH OF MADAGASCAR SHOULD ALLOW

TO THE SYSTEM  TO KEEP ON ITS WESTSOUTHWESTWARD TRACK. ON THIS TRACK,

A LANDFALL OVER THE MALAGASY COASTLINE, NEAR TAMATAVE REMAINS

POSSIBLE FRIDAY AT MID-DAY. A CYCLONIC SURGE OF ABOUT 1.5M TO 2M IS

EXPECTED NEAR VATOMANDRY, SOUTH OF THE AREA OF LANDFALL.



FROM FRIDAY NIGHT TO SATURDAY, AVA IS FORECASTED TO RE-CURVE

SOUTHWARD BEHING THE FAST RIDGE AND TOWARD A NEW MID-TOPOSPHERIC

TROUGH. A LARGE UNCERTAINTY EXISTS ON THE TRACK OF THE SYSTEM OVER

LAND AND SO ABOUT THE INTENSITY OF THE SYSTEM AT ITS COME BACK OVER

SEAS ON SATURDAY. THIS FORECAST IS BASED ON A CEP/GFS CONSENSUS.



ENVIRONMENTAL CONDITIONS ARE RATHER CONDUCIVE FOR AN INTENSIFICATION

UP TO THE LANDFALL WITH A GOOD UPPER DIVERGENCE IN THE NORTH-WESTERN

QUADRANT. MINIMAL TROPICAL CYCLONE STATUS IS NOW FORECAST AT THE

LANDFALL PERIOD. FROM SATURDAY, THE TRACK WILL BE DECISIVE FOR THE

FORECAST INTENSITY.

 AT ITS EXIT OVER OCEAN, AVA MAY ENCOUNTER ENVIRONMENTAL CONDITIONS

VERY FAVORABLE FOR A NEW PHASE OF INTENSIFICATION WITH A GOOD UPPER

LEVEL DIVERGENCE AHEAD AN UPPER LEVEL TROUGH AND A LOW VERTICAL

WINDSHEAR. ALONG THE FORECAST TRACK, THE OCEANIC HEAT POTENTIAL

UNDERNEATH REMAIN FAVORABLE AND ONLY THE VICINITY OF MADAGASCAR

DURING THE PERIOD AND UP TO TUESDAY A MODERATE WESTERN VERTICAL

WINDSHEAR SHOULD PREVENT THE SYSTEM INTENSITY SOUTH OF 25S. A TRACK

FOR LONGER OVER LAND WILL LIMIT THE LIKELIHOOD OF REINTENSIFICATION.



THE PERIPHERAL THUNDERSTORMS BANDS ASSOCIATED TO THE SYSTEM ARE

AFFECTING THE WEATHER ON THE MALAGASY LANDS EAST TO 47E AND GOING ON

OVER THE MASCARENES ARCHIPELAGO.=