WTIO30 FMEE 071244



RSMC / TROPICAL CYCLONE CENTER / LA REUNION

TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN)



0.A WARNING NUMBER: 31/1/20172018

1.A MODERATE TROPICAL STORM  1  (AVA)



2.A POSITION 2018/01/07 AT 1200 UTC:

WITHIN 30 NM RADIUS OF POINT 23.1 S / 49.3 E

(TWENTY THREE    DECIMAL ONE   DEGREES SOUTH AND FORTY NINE

DECIMAL THREE   DEGREES EAST)

MOVEMENT : SOUTH-EAST 7 KT



3.A DVORAK ANALYSIS: NIL



4.A CENTRAL PRESSURE: 987 HPA

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

RADIUS OF MAXIMUM WINDS (RMW) :28 KM



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

28 KT NE: 370 SE: 460 SW: 370 NW:

34 KT NE: 280 SE: 280 SW:  NW:







7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1006 HPA / 1000 KM

8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION : MEDIUM



1.B FORECASTS:

12H: 2018/01/08 00 UTC: 24.7 S / 49.0 E, MAX WIND=035 KT, MODERATE

TROPICAL STORM

24H: 2018/01/08 12 UTC: 26.0 S / 48.2 E, MAX WIND=035 KT, MODERATE

TROPICAL STORM

36H: 2018/01/09 00 UTC: 27.4 S / 47.7 E, MAX WIND=035 KT, MODERATE

TROPICAL STORM

48H: 2018/01/09 12 UTC: 28.8 S / 48.2 E, MAX WIND=040 KT,

POST-TROPICAL DEPRESSION

60H: 2018/01/10 00 UTC: 29.8 S / 50.2 E, MAX WIND=040 KT,

POST-TROPICAL DEPRESSION

72H: 2018/01/10 12 UTC: 30.7 S / 52.9 E, MAX WIND=040 KT,

POST-TROPICAL DEPRESSION



2.B LONGER-RANGE OUTLOOK :

96H: 2018/01/11 12 UTC: 33.0 S / 61.4 E, MAX WIND=040 KT,

POST-TROPICAL DEPRESSION

120H: 2018/01/12 12 UTC: 34.6 S / 70.4 E, MAX WIND=040 KT,

POST-TROPICAL DEPRESSION



2.C ADDITIONAL INFORMATION:

SINCE ITS COMEBACK OVER SEA, MODERATE CONVECTIVE ACTIVITY IS LOCATED

NEAR THE CENTER. 0925Z AMSR2 MICROWAVE DATA SHOW THE EXISTENCE A

DEFINED LOW LEVEL INNER CORE. MAXIMAL WINDS NEAR THE CENTER MAY BE

BELOW GALE FORCE BUT FAR FROM THE CENTER, ASCAT DATA STILL SUGGEST

THE PRESENCE OF GALE FORCE WINDS.



STEERED BY A MID-LATITUDE TROUGH ATTRACTING IT IN THE SOUTH, AVA

STARTED TO TRACK SOUTHWARD. FROM TUESDAY UNCERTAINTY BECOME VERY

IMPORTANT WITH TWO MAIN SCENARIOS : EITHER THE SYSTEM IS BLOCKED BY

THE ARRIVAL OF THE NEW HIGH PRESSURE CELL IN THE SOUTH OR TAKEN AWAY

BY THE WESTERLIES. THE ARRIVAL OF IRVING MAY ALSO INFLUENCE AVA'S

TRACK. THE RSMC OFFICIAL FORECAST FOLLOW AN INTERMEDIATE SCENARIO

BASED ON SEVERAL ECMWF EPS MEMBERS.



AVA IS EXPECTED TO HAVE RATHER CONDUCIVE CONDITIONS IN THE NEXT HOURS

BUT ITS LONG TRACK ON MALAGASY LANDS HAS STRONGLY WEAKENED THE

SYSTEM. ITS REINTENSIFICATION PHASE NEEDS THE REBUILDING OF A DEEP

FLOW. FROM TUESDAY, A MODERATE TO STRONG WESTERLY SHEAR IS FORECAST

TO IMPACT AVA. THE SYSTEM SHOULD THEN BEGIN TO TRANSFORM INTO A

BAROCLINIC LOW UNDER THE INFLUENCE OF AN UPPER TROUGH COMING FROM THE

WEST.=