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WTIO30 FMEE 031322
RSMC / TROPICAL CYCLONE CENTER / LA REUNION
TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN)
0.A WARNING NUMBER: 23/11/20112012
1.A MODERATE TROPICAL STORM 11 (IRINA)
2.A POSITION 2012/03/03 AT 1200 UTC:
WITHIN 20 NM RADIUS OF POINT 25.8 S / 35.5 E
(TWENTY FIVE DECIMAL EIGHT DEGREES SOUTH AND THIRTY FIVE DECIMAL FIVE
DEGREES EAST)
MOVEMENT : SOUTH-WEST 8 KT
3.A DVORAK ANALYSIS: 3.0/3.0/D 0.5/6 H
4.A CENTRAL PRESSURE: 986 HPA
5.A MAX AVERAGE WIND SPEED (10 MN): 40 KT
RADIUS OF MAXIMUM WINDS (RMW) :37 KM
6.A EXTENSION OF WIND BY QUADRANTS (KM):
28 KT NE: 60 SE: 590 SW: 410 NW: 110
34 KT NE: 50 SE: 110 SW: 130 NW: 80
7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 998 HPA / 400 KM
8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION : MEDIUM
1.B FORECASTS:
12H: 2012/03/04 00 UTC: 26.5 S / 34.6 E, MAX WIND=050 KT, SEVERE TROPICAL STORM
24H: 2012/03/04 12 UTC: 28.4 S / 34.2 E, MAX WIND=050 KT, SEVERE TROPICAL STORM
36H: 2012/03/05 00 UTC: 29.9 S / 34.5 E, MAX WIND=050 KT, SEVERE TROPICAL STORM
48H: 2012/03/05 12 UTC: 30.5 S / 36.0 E, MAX WIND=050 KT, SEVERE TROPICAL STORM
60H: 2012/03/06 00 UTC: 30.0 S / 37.3 E, MAX WIND=050 KT, SEVERE TROPICAL STORM
72H: 2012/03/06 12 UTC: 29.0 S / 38.2 E, MAX WIND=050 KT, SEVERE TROPICAL STORM
2.B LONGER-RANGE OUTLOOK :
96H: 2012/03/07 12 UTC: 26.6 S / 37.3 E, MAX WIND=050 KT, SEVERE TROPICAL STORM
120H: 2012/03/08 12 UTC: 26.2 S / 35.4 E, MAX WIND=070 KT, TROPICAL CYCLONE
2.C ADDITIONAL INFORMATIONS:
T=3.0- CI=3.0-
BOTH CONVECTIVE AND WINDS FIELD STRUCTURES REMAINS ASYMMETRIC WITH
STRONGEST WINDS EXTENDING FAR AWAY IN THE SOUTHERN SEMI-CIRCLE DUE TO
THE GRADIENT EFFECT WITH SUBTROPICAL HIGH PRESSURES.
WINDS EXTENSION HAS BEEN RECALIBRATED THANKS TO 03/0716Z ASCAT SWATH.
WITHIN THE NEXT 24 HOURS, IRINA IS EXPECTED TO SHIFT SOUTHWESTWARDS
THEN SOUTHWARDS ON THE WESTERN EDGE OF THE THE SUBTROPICAL HIGHPRESSURES TRANSITING SOUTH OF MADAGASCAR.
IN RELATIONSHIP WITH THE LARGE FETCH IN THE SOUTHERN SEMI-CIRCLE, A 4
METERS TO 6 METERS CYCLONIC SWELL IS EXPECTED TO THREATEN AFRICAN
COASTLINES FROM 24S TO 33S WITHIN THE NEXT 24 HOURS.
FROM TAU24 TO TAU48, SYSTEM IS EXPECTED TO PROGRESSIVELY RECURVE
SOUTHEASTWARDS TOWARDS A POLAR TROUGH TRANSITING BETWEEN THE TWO
SUBTROPICAL HIGH PRESSURES AREAS.
THE FIRST AFOREMENTIONED ONE IS MOVING EASTWARDS AWAY AND A NEW ONE
IS REBUILDING IN THE SOUTHWEST.
BEYOND TAU48, IRINA IS EXPECTED TO MAKE A LOOP LEFT-HAND NORTHWARDS
THEN WESTWARDS UNDER THE STEERING INFLUENCE OF THIS REBUILDING
SUBTROPICAL HIGHS.
WITHIN THE SOUTHWARDS MOTION, ENVIRONMENTAL CONDITIONS ARE NEUTRAL
(LACK OF LOW LEVEL INFLOW, MARGINAL SST) AND TEMPORARILY
UNFAVOURABLE (WESTERLY WINDSHEAR CONSTRAINT IS EXPECTED ON MONDAY
05 AND TUESDAY 06), SYSTEM IS THEREFORE NOT EXPECTED TO INTENSIFY AND
SHOULD TEMPORARILY WEAKEN.
ON AND AFTER WEDNESDAY 07, AS SYSTEM RECURVES NORTHWESTWARDS THEN
WESTWARDS, ENVIRONMENTAL CONDITIONS BECOME BACK FAVOURABLE FOR
INTENSIFICATION.
RSMC OFFICIAL FORECAST CONSIDER THIS SCENARIO AS THE MOST LIKELY
(PURPOSED BY ECMWF, ARPEGE AND NOGAPS NWP MODELS).
AN ALTERNATIVE SCENARIO EXISTS HOWEVER TO FORECAST A GLOBALLY
WESTWARDS TRACK TOWARDS THE MOZAMBIQUE COASTLINE AND THEREFORE AN
EXPECTED LANDFALL NEXT NIGHT OR SUNDAY (GFS, ALADIN AND GFDN NWP
MODELS OPTION).
A RATHER STRONG UNCERTAINTY KEEPS ON EXISTING RELATED TO THE OFFICIAL
FORECAST.
A LANDFALL OVER MOZAMBIQUE COASTLINE AT SHORT OR MEDIUM RANGE CAN
NOT BE EXCLUDED.
DESPITE CURRENT FORECAST, ALL INHABITANTS ALONG AFRICAN COASTLINE
BETWEEN 23S AND 30S ARE INVITED TO CLOSELY MONITOR THE EVOLUTION OF
IRINA.