WTIO30 FMEE 161308



RSMC / TROPICAL CYCLONE CENTER / LA REUNION

TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN)



0.A WARNING NUMBER: 10/6/20142015

1.A SEVERE TROPICAL STORM  6  (CHEDZA)



2.A POSITION 2015/01/16 AT 1200 UTC:

WITHIN 20 NM RADIUS OF POINT 19.9 S / 43.9 E

(NINETEEN    DECIMAL NINE   DEGREES SOUTH AND FORTY THREE    DECIMAL

NINE   DEGREES EAST)

MOVEMENT : EAST-SOUTH-EAST 8 KT



3.A DVORAK ANALYSIS: 3.5/3.5/D 0.5/6 H



4.A CENTRAL PRESSURE: 975 HPA

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

RADIUS OF MAXIMUM WINDS (RMW) :56 KM



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

28 KT NE: 280 SE: 190 SW: 220 NW: 300

34 KT NE: 170 SE: 130 SW: 170 NW: 200

48 KT NE: 100 SE: 80 SW: 100 NW: 110





7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1006 HPA / 1200 KM

8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION : DEEP



1.B FORECASTS:

12H: 2015/01/17 00 UTC: 20.6 S / 45.2 E, MAX WIND=030 KT, INLAND

24H: 2015/01/17 12 UTC: 21.6 S / 48.6 E, MAX WIND=030 KT, TROPICAL

DEPRESSION

36H: 2015/01/18 00 UTC: 22.0 S / 50.8 E, MAX WIND=035 KT, TROPICAL

DEPRESSION

48H: 2015/01/18 12 UTC: 22.3 S / 51.9 E, MAX WIND=040 KT, MODERATE

TROPICAL STORM

60H: 2015/01/19 00 UTC: 22.9 S / 52.7 E, MAX WIND=040 KT, MODERATE

TROPICAL STORM

72H: 2015/01/19 12 UTC: 23.3 S / 53.1 E, MAX WIND=040 KT, MODERATE

TROPICAL STORM



2.B LONGER-RANGE OUTLOOK :

96H: 2015/01/20 12 UTC: 24.7 S / 53.9 E, MAX WIND=035 KT, MODERATE

TROPICAL STORM

120H: 2015/01/21 12 UTC: 26.2 S / 55.3 E, MAX WIND=035 KT, MODERATE

TROPICAL STORM



2.C ADDITIONAL INFORMATIONS:

T=CI=3.5



THE CLOUD PATTERN OF CHEDZA HAS IMPROVED OVER THE LAST 6 HOURS BUT

THE IMMINENT LANDFALL IS LIKELY TO STOP FURTHER SIGNIFICANT

INTENSIFICATION. THE CURRENT POSITION IS BASED ON GEOSTAT FIX WITH AN

EVIDENT CENTER. THE CURRENT INTENSITY (VMAX, PMIN) IS BASED ON OBS

FROM MORONDAVA AT 12Z (10 MIN WINDS AT 54 KT AND MSLP AT 980.7 HPA)

THAT WAS ALSO HELPFUL TO ASSESS THE RADIUS OF MAX WINDS.



LANDFALL IS EXPECTED WITHIN A FEW HOURS BETWEEN BELO AND MORONDAVA.

NUMERICAL STORM SURGE SIMULATIONS GIVE AS RESULTS : 1M50 TO 2M WITHIN

THE AREA NORTH OF THE TRACK BETWEEN MAINTIRANO AND BELO.

NOTE THAT THIS STORM SURGE FORECAST IS TO TAKE WITH CAUTION AND DOES

NOT TAKE IN ACCOUNT THE ADDITIONAL SUBMERSION EFFECTS DUE TO THE

CYCLONIC SWELL AND ASTRONOMIC TIDE.





MOST OF THE AVAILABLE NWP MODELS SUGGEST THAT THE LOW LEVEL

CIRCULATION COULD RE-DEVELOP AS THE SYSTEM GET BACK OVERSEA ON THE

SOUTH-EAST OF MADAGASCAR ON SATURDAY.

ENVIRONMENTAL CONDITIONS ARE EXPECTED TO BE MARGINAL BY THAT TIME

WITH  A MODERATE WEST-NORTH-WESTERLY VERTICAL WINDSHEAR HOWEVER

WEAKENING ON SUNDAY AND IN THE SAME DIRECTION THAN THE SYSTEM'S

MOTION,

BUT IN A VERY GOOD LOW LEVEL CONVERGENCE ENVIRONMENT OVER FAVORABLE

HEAT OCEANIC CONTENTS AND SUSTAINED BY AN EFFICIENT POLEWARD

UPPER-LEVEL OUTFLOW. FROM TUESDAY AND BEYOND, A RISING WINDSHEAR

SHOULD PREVENT SIGNIFICANT INTENSIFICATION. SURPRISINGLY, MOST NWP

GUIDANCE CONTINUE TO STRENGTHEN THE SYSTEM BY THAT TIME.



UNTIL SUNDAY, THE SYSTEM IS EXPECTED TO MOVE GENERALLY EASTWARDS ON

THE SOUTHERN EDGE OF THE NEAR EQUATORIAL RIDGE.

ON AND AFTER MONDAY, A MID-LEVEL TROUGH ARRIVES IN THE SOUTH AND

CHEDZA IN THEN EXPECTED TO RECURVE SOUTH-SOUTH-EASTWARDS. HOWEVER THE

LATEST ENSEMBLE FORECAST SHOW SOME SIGNIFICANT SPREAD OF THE TRACK

WHEN THE SYSTEM WILL EVOLVE TO THE SOUTHWEST OF THE MASCAREIGNES.=