WTIO30 FMEE 090050



RSMC / TROPICAL CYCLONE CENTER / LA REUNION

TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN)



0.A WARNING NUMBER: 37/1/20172018

1.A MODERATE TROPICAL STORM  1  (AVA)



2.A POSITION 2018/01/09 AT 0000 UTC:

WITHIN 30 NM RADIUS OF POINT 27.0 S / 47.2 E

(TWENTY SEVEN    DECIMAL ZERO   DEGREES SOUTH AND FORTY SEVEN

DECIMAL TWO   DEGREES EAST)

MOVEMENT : EAST 6 KT



3.A DVORAK ANALYSIS: NIL



4.A CENTRAL PRESSURE: 989 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: 670 SE: 520 SW: 220 NW: 0

34 KT NE: 300 SE: 330 SW: 0 NW: 0







7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1004 HPA / 1100 KM

8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION : MEDIUM



1.B FORECASTS:

12H: 2018/01/09 12 UTC: 28.4 S / 48.7 E, MAX WIND=035 KT,

POST-TROPICAL DEPRESSION

24H: 2018/01/10 00 UTC: 30.8 S / 51.6 E, MAX WIND=035 KT,

POST-TROPICAL DEPRESSION

36H: 2018/01/10 12 UTC: 34.9 S / 56.8 E, MAX WIND=040 KT,

EXTRATROPICAL DEPRESSION

48H: 2018/01/11 00 UTC: 41.0 S / 64.7 E, MAX WIND=040 KT, DISSIPATING







2.B LONGER-RANGE OUTLOOK :







2.C ADDITIONAL INFORMATION:

AVA'S STRUCTURE HAS REMAINED BASICALLY UNCHANGED OVER THE LAST 6

HOURS: THUNDERSTORM ACTIVITY REMAINS FAR AWAY FROM THE CENTER OVER

THE EASTERN SEMI-CIRCLE. THE INTENSITY ESTIMATES REMAINS UNCERTAIN

BUT SCATSAT PASS AT 1720Z SUGGEST BELIEVABLE 30-35 KT OVER THE

EASTERN SEMI-CIRCLE.



AVA HAS MADE A LOOP OVERNIGHT AND IS CURRENTLY DRIFTING EASTWARDS.

TODAY, THE RIDGE IS FORECASTED TO SHIFT EASTWARD AND AVA SHOULD

GRADUALLY ACCELERATE SOUTHEASTWARD STEERED BY A MID-LATITUDE TROUGH

ARRIVING BY ITS SOUTH-WEST. MODELS ARE NOW IN GOOD AGREEMENT IN THIS

SCENARIO.



A MODERATE TO STRONG VERTICAL WESTERLY WINDSHEAR SHOULD IS GRADUALLY

AFFECTING THE SYSTEM WHILE OCEAN HEAT CONTENT BECOME INSUFFICIENT.

TODAY, AVA SHOULD BEGIN TO INTERACT WITH THE SUBTROPICAL JETSTREAK,

AND SHOULD BEGIN ITS EXTRATROPICAL TRANSITION. AVA'S

EXTRATROPICALISATION PROCESS IS FORECASTED TO BE ACHIEVE BY

WEDNESDAY. AFTER THAT THE CLOCLWISE CIRCULATION IS EXPECTED TO MERGE

WITHIN THE COLD FRONT ASSOCIATED WITH THE MID-LAT TROUGH.=