WTIO30 FMEE 060729



RSMC / TROPICAL CYCLONE CENTER / LA REUNION

TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN)



0.A WARNING NUMBER: 26/1/20172018

1.A OVERLAND DEPRESSION  1  (AVA)



2.A POSITION 2018/01/06 AT 0600 UTC:

WITHIN 20 NM RADIUS OF POINT 19.9 S / 47.8 E

(NINETEEN    DECIMAL NINE   DEGREES SOUTH AND FORTY SEVEN    DECIMAL

EIGHT   DEGREES EAST)

MOVEMENT : SOUTH-SOUTH-WEST 7 KT



3.A DVORAK ANALYSIS: NIL



4.A CENTRAL PRESSURE: 992 HPA

5.A MAX AVERAGE WIND SPEED (10 MN): 35 KT

RADIUS OF MAXIMUM WINDS (RMW) :NIL



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

28 KT NE: 170 SE: 330 SW:  NW:









7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1003 HPA / 1300 KM

8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION : MEDIUM



1.B FORECASTS:

12H: 2018/01/06 18 UTC: 21.3 S / 48.4 E, MAX WIND=035 KT, OVERLAND

DEPRESSION

24H: 2018/01/07 06 UTC: 23.1 S / 48.4 E, MAX WIND=035 KT, MODERATE

TROPICAL STORM

36H: 2018/01/07 18 UTC: 24.5 S / 48.3 E, MAX WIND=045 KT, MODERATE

TROPICAL STORM

48H: 2018/01/08 06 UTC: 25.3 S / 47.5 E, MAX WIND=050 KT, SEVERE

TROPICAL STORM

60H: 2018/01/08 18 UTC: 26.3 S / 47.1 E, MAX WIND=055 KT, SEVERE

TROPICAL STORM

72H: 2018/01/09 06 UTC: 27.8 S / 47.2 E, MAX WIND=055 KT, SEVERE

TROPICAL STORM



2.B LONGER-RANGE OUTLOOK :

96H: 2018/01/10 06 UTC: 29.2 S / 52.1 E, MAX WIND=035 KT, MODERATE

TROPICAL STORM

120H: 2018/01/11 06 UTC: 28.7 S / 57.3 E, MAX WIND=030 KT, TROPICAL

DEPRESSION



2.C ADDITIONAL INFORMATION:

THE SYSTEM HAS TRACKED WELL INLAND OVER THE LAST HOURS. CONVECTION

WEAKENED BUT THE SYSTEM'S STRUCTURE REMAINS RATHER WELL DEFINED WITH

A SYMMETRICAL CIRCULATION AND A WELL-DEFINED CENTER. SSMIS 0303Z MW

IMAGES CONFIRM THAT THE INTERNAL STRUCTURE IS RESISTING WELL TO THIS

PASSAGE OVERLAND FOR NOW. THE AREA INFLUENCED BY AVA REMAINS LARGE

WITH FREQUENT THUNDERSTORMS OVER THE MAIN PART OF MADAGASCAR AND

OUTER RAINBANDS AFFECTING THE COMOROS AND MASCARENES ARCHIPELAGOS.



STEERED BY THE RIDGE IN THE EAST AND A MID-LATITUDE TROUGH ATTRACTING

IT IN THE SOUTH, AVA SHOULD SLIGHTLY RECURVE SOUTH-SOUTH-EASTWARD AND

COME BACK OVER SEA BY THE END OF THE WEEK-END. FROM TUESDAY, THE

ENSEMBLE PREDICTION SHOWS TWO POSSIBLE SCENARIOS : EITHER THE SYSTEM

IS BLOCKED BY THE ARRIVAL OF THE NEW HIGH PRESSURE CELL IN THE SOUTH

OR TAKEN AWAY BY THE WESTERLIES. THUS, THE UNCERTAINTY REMAINS HIGH

EVEN IF THE LAST MODEL RUNS SEEM TO FAVOUR THE SECOND OPTION, WHICH

HAS BEEN CHOSEN TO BE THE RSMC OFFICIAL FORECAST.



WHEN EXITING OVER THE OCEAN, AVA MAY ENCOUNTER VERY FAVORABLE

CONDITIONS, WHETHER ATMOSPHERIC OR OCEANIC, FOR A NEW INTENSIFICATION

PHASE. A SHORTEST TRACK ON MALAGASY LANDS MAY MAINTAIN MORE IMPORTANT

INTENSITY IN THE SYSTEM. FROM TUESDAY, A MODERATE TO STRONG EASTERLY

SHEAR IS AFFECTING AVA WHILE THE OCEANIC POTENTIAL BECOMES LIMITED

SOUTH OF 25S. THE SYSTEM SHOULD THEN BEGIN TO WEAKEN GRADUALLY.=