WTIO30 FMEE 171231
RSMC / TROPICAL CYCLONE CENTER / LA REUNION
TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN)

0.A WARNING NUMBER: 8/7/20202021
1.A MODERATE TROPICAL STORM 7 (ELOISE)

2.A POSITION 2021/01/17 AT 1200 UTC:
WITHIN 20 NM RADIUS OF POINT 13.0 S / 61.4 E
(THIRTEEN DECIMAL ZERO DEGREES SOUTH AND
SIXTY ONE DECIMAL FOUR DEGREES EAST)
MOVEMENT: WEST-SOUTH-WEST 8 KT

3.A DVORAK ANALYSIS: 2.5/2.5/D 0.5/12 H

4.A CENTRAL PRESSURE: 994 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: 185 SE: 425 SW: 425 NW: 270
34 KT NE: 0 SE: 150 SW: 185 NW: 110

7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1005 HPA / 900 KM
8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION: DEEP

1.B FORECASTS (WINDS RADII IN KM):
12H: 2021/01/18 00 UTC: 13.5 S / 58.4 E, VENT MAX= 035 KT, MODERATE
TROPICAL STORM
28 KT NE: 165 SE: 285 SW: 305 NW: 110
34 KT NE: 85 SE: 95 SW: 120 NW: 65

24H: 2021/01/18 12 UTC: 14.3 S / 55.7 E, VENT MAX= 040 KT, MODERATE
TROPICAL STORM
28 KT NE: 185 SE: 315 SW: 280 NW: 165
34 KT NE: 95 SE: 120 SW: 110 NW: 65

36H: 2021/01/19 00 UTC: 15.2 S / 53.4 E, VENT MAX= 045 KT, MODERATE
TROPICAL STORM
28 KT NE: 165 SE: 280 SW: 240 NW: 155
34 KT NE: 85 SE: 110 SW: 75 NW: 65

48H: 2021/01/19 12 UTC: 15.7 S / 52.0 E, VENT MAX= 050 KT, SEVERE
TROPICAL STORM
28 KT NE: 175 SE: 240 SW: 250 NW: 140
34 KT NE: 85 SE: 95 SW: 100 NW: 110
48 KT NE: 45 SE: 35 SW: 65 NW: 65

60H: 2021/01/20 00 UTC: 15.9 S / 50.9 E, VENT MAX= 060 KT, SEVERE
TROPICAL STORM
28 KT NE: 165 SE: 230 SW: 185 NW: 110
34 KT NE: 75 SE: 95 SW: 85 NW: 100
48 KT NE: 55 SE: 45 SW: 65 NW: 65

72H: 2021/01/20 12 UTC: 15.9 S / 48.4 E, VENT MAX= 020 KT, OVERLAND
DEPRESSION

2.B LONGER-RANGE OUTLOOK:
96H: 2021/01/21 12 UTC: 18.0 S / 44.0 E, VENT MAX= 030 KT, ZONE OF
DISTURBED WEATHER
28 KT NE: 95 SE: 250 SW: 110 NW: 85

120H: 2021/01/22 12 UTC: 20.3 S / 40.2 E, VENT MAX= 045 KT, MODERATE
TROPICAL STORM
28 KT NE: 280 SE: 350 SW: 240 NW: 175
34 KT NE: 120 SE: 220 SW: 155 NW: 110

2.C ADDITIONAL INFORMATION:
T=2.5-;CI=2.5

OVER THE LAST 6HRS, CONVECTION MAINTAINED OVER THE CIRCULATION CENTER
BUT WEAKENED OVERALL, PROBABLY BECAUSE OF THE DIURNAL CYCLE. THE
EASTERLY SHEAR KEEPS ON SLOWING THE DEVELOPMENT OF ELOISE (25KT
ACCORDING TO CIMSS ANALYSIS). ON THE VERY LAST SAT IMAGES AVAILABLE,
THE LOW-LEVEL CENTER SEEMS TO BECOME VISIBLE UNDER THE CIRRUS CLOUDS, SOUTH-EAST OF THE MAIN CONVECTION.

OVER THE NEXT FEW DAYS THE ENVIRONMENTAL CONDITIONS REMAIN
AMBIVALENT. THE EASTERLY SHEAR REMAINS OMNIPRESENT WITH
MID-TROPOSPHERE DRY AIR LOCATED IN THE EASTERN EDGE OF THE
CIRCULATION, WHILE THE UPPER DIVERGENCE REMAINS GOOD IN THE
NORTHWESTERN QUADRANT. IN THIS CONTEXT, A SLOW INTENSIFICATION OF THE
SYSTEM IS EXPECTED IN AGREEMENT WITH MOST NUMERICAL GUIDANCE. FROM
MONDAY EVENING, THE SHEAR CONSTRAINT COULD EASE OFF, FIRST IN THE
UPPER LEVELS THEN AT THE MID-LEVELS. CONSEQUENTLY, THE DEVELOPMENT OF
ELOISE COULD ACCELERATE BEFORE LADNFALL AS SUGGESTED BY SOME MODELS
(HWRF, ARPEGE, IFS). THE DEGREE OF CONFIDENCE IN THIS INTENSITY
PREDICTION IS LOW.

THE SYSTEM IS EXPECTED TO KEEP ON HEADING WEST-SOUTH-WESTWARD ON THE NORTH-WESTERN SIDE OF THE LOW/MID-LEVEL SUTROPICAL RIDGE. TUESDAY,
THE PASSAGE OF A TROUGH IN THE SOUTH WILL TEMPORARILY WEAKEN THE
RIDGE AND COULD DRIVE A SLIGHT SOUTHWESTWARD INFLECTION OF THE TRACK.
HOWEVER, THE RIDGE STRENGTHENS BACK UP AS SOON AS WEDNESDAY WHICH
SOULD PREVENT ELOISE FROM SIGNIFICANTLY DIVING SOUTHWARDS. THE EURO
ENSEMBLE AND DETERMINISTIC GUIDANCE DISPERSION IS WEAKER THAN NORMAL,
WHICH YIELDS A GOOD CONFIDENCE IN THIS TRACK FORECAST.

IT IS TOO EARLY TO PINPOINT LOCATION AND INTENSITY AT LANDFALL BUT
THERE IS A RISK OF STRONG WINDS, FLOODS AND STORM SURGE OVER SOME
COASTAL AREAS OF EASTERN MADAGASCAR MAINLY BETWEEN SAMBAVA TO THE
NORTH AND TAMATAVE TO THE SOUTH. A LANDFALL AT TROPICAL CYCLONE
INTENSITY REMAINS A REAL POSSIBILITY.

THURSDAY, ELOISE SHOULD COME BACK OVER SEA ON THE MOZAMBIQUE CHANNEL.
A NEW INTENSIFICATION PHASE IS AWAITED WITHIN CONDUCIVE ENVIRONMENTAL CONDITIONS.
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