WTIO30 FMEE 081831



RSMC / TROPICAL CYCLONE CENTER / LA REUNION

TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN)



0.A WARNING NUMBER: 22/4/20162017

1.A SEVERE TROPICAL STORM  4  (CARLOS)



2.A POSITION 2017/02/08 AT 1800 UTC:

WITHIN 20 NM RADIUS OF POINT 23.0 S / 52.9 E

(TWENTY THREE    DECIMAL ZERO   DEGREES SOUTH AND FIFTY TWO

DECIMAL NINE   DEGREES EAST)

MOVEMENT : SOUTH-SOUTH-EAST 6 KT



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



4.A CENTRAL PRESSURE: 980 HPA

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

RADIUS OF MAXIMUM WINDS (RMW) :28 KM



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

28 KT NE: 110 SE: 190 SW: 110 NW: 60

34 KT NE: 80 SE: 120 SW: 80 NW: 50

48 KT NE: 40 SE: 50 SW: 40 NW: 30





7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1007 HPA / 500 KM

8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION : DEEP



1.B FORECASTS:

12H: 2017/02/09 06 UTC: 24.0 S / 53.4 E, MAX WIND=060 KT, SEVERE

TROPICAL STORM

24H: 2017/02/09 18 UTC: 25.2 S / 54.3 E, MAX WIND=060 KT, SEVERE

TROPICAL STORM

36H: 2017/02/10 06 UTC: 26.7 S / 55.9 E, MAX WIND=055 KT, SEVERE

TROPICAL STORM

48H: 2017/02/10 18 UTC: 28.1 S / 58.7 E, MAX WIND=050 KT, SEVERE

TROPICAL STORM

60H: 2017/02/11 06 UTC: 28.9 S / 60.8 E, MAX WIND=045 KT, MODERATE

TROPICAL STORM

72H: 2017/02/11 18 UTC: 29.6 S / 62.3 E, MAX WIND=035 KT, MODERATE

TROPICAL STORM



2.B LONGER-RANGE OUTLOOK :

96H: 2017/02/12 18 UTC: 30.4 S / 62.5 E, MAX WIND=035 KT,

POST-TROPICAL DEPRESSION

120H: 2017/02/13 18 UTC: 30.4 S / 60.7 E, MAX WIND=035 KT,

POST-TROPICAL DEPRESSION



2.C ADDITIONAL INFORMATION:

T=CI=3.5+



OVER THE PAST HOURS, CLOUD TOPS REMAINED VERY COLD OVER CARLOS'

CENTER, WITH A STILL SMALL CORE STRUCTURE. RADAR DATA HAVE EVEN

EXHIBITED A TEMPORARY EYE PATTERN. 1527Z F18 MW DATA CONFIRM THIS NEW

ORGANISATION IMPROVEMENT BY SHOWING A NICE STRONG CONVECTION RING ON

THE 91GHZ IMAGES. WV IMAGERY ALSO DEPICTS THE PRESENCE OF DRY AIR

CLOSE TO THE SOUTH-WESTERN QUADRANT.



DURING THE NEXT HOURS, CARLOS IS EXPECTED TO KEEP ON ACCELERATING

TOWARDS THE SOUTH-EAST, UNDER THE GROWING INFLUENCE OF A

MID-TROPOSPHERIC RIDGE IN THE NORTH-EAST AND A TROUGH COMING FROM THE

MID-LATITUDES. FROM FRIDAY, THERE IS A LARGE SPEED DISPERSION IN THE

NUMERICAL GUIDANCE PROBABLY CAUSED BY DIFFERENT IMPACTS OF VERTICAL

WIND SHEAR. FROM SUNDAY, CARLOS SHOULD BE BLOCKED BY A HIGH CELL

CIRCULATING EASTWARDS IN ITS SOUTH. THE TRACK UNCERTAINTY IS

INCREASING WITH A FEW MODELS LOOPING NORTHWARD (GFS) BUT A MAJORITY

FORECASTING A SOUTHWARD U-TURN (ECMWF MODEL). THIS TRACK FORECAST IS

BASED ON THE SECOND SCENARIO.



FROM TOMORROW, CARLOS SHOULD TRACK AHEAD OF AN UPPER TROUGH COMING

FROM THE MID-LATITUDES. AT FIRST, THE DIVERGENCE IN THE SOUTH-EASTERN

QUADRANT AND CARLOS' SOUTH-EASTWARD TRACK SHOULD MITIGATE THE

INFLUENCE OF THE MODERATE WESTERLY SHEAR. BUT IT SHOULD QUICKLY

BECOME TOO STRONG ESPECIALLY GIVEN CARLOS SIZE, AS A MID-TROPOSPHERIC

DRY AIR LAYER COULD ALSO SLITHER IN CARLOS CORE. THE SYSTEM INTENSITY

IS THUS FORECAST TO DECAY (POSSIBLY QUICKLY). FURTHER MORE, THE

PROXIMITY OF THE UPPER TROUGH COULD TRIGGER AN EXTRATROPICALISATION

PHASE.=