WTIO30 FMEE 181839
RSMC / TROPICAL CYCLONE CENTER / LA REUNION
TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN)

0.A WARNING NUMBER: 11/11/20202021
1.A SEVERE TROPICAL STORM 11 (GUAMBE)

2.A POSITION 2021/02/18 AT 1800 UTC:
WITHIN 20 NM RADIUS OF POINT 23.4 S / 37.1 E
(TWENTY THREE DECIMAL FOUR DEGREES SOUTH AND
THIRTY SEVEN DECIMAL ONE DEGREES EAST)
MOVEMENT: SOUTH-WEST 4 KT

3.A DVORAK ANALYSIS: 3.5/3.5/S 0.0/12 H

4.A CENTRAL PRESSURE: 982 HPA
5.A MAX AVERAGE WIND SPEED (10 MN): 50 KT
RADIUS OF MAXIMUM WINDS (RMW): 37 KM

6.A EXTENSION OF WIND BY QUADRANTS (KM):
28 KT NE: 280 SE: 280 SW: 185 NW: 315
34 KT NE: 295 SE: 185 SW: 55 NW: 55
48 KT NE: 55 SE: 55 SW: 0 NW: 0

7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1006 HPA / 900 KM
8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION: DEEP

1.B FORECASTS (WINDS RADII IN KM):
12H: 2021/02/19 06 UTC: 24.2 S / 36.6 E, VENT MAX= 055 KT, SEVERE
TROPICAL STORM
28 KT NE: 370 SE: 360 SW: 350 NW: 155
34 KT NE: 270 SE: 250 SW: 205 NW: 100
48 KT NE: 110 SE: 110 SW: 85 NW: 75

24H: 2021/02/19 18 UTC: 24.8 S / 36.1 E, VENT MAX= 060 KT, SEVERE
TROPICAL STORM
28 KT NE: 305 SE: 325 SW: 295 NW: 175
34 KT NE: 230 SE: 230 SW: 185 NW: 165
48 KT NE: 130 SE: 120 SW: 85 NW: 95

36H: 2021/02/20 06 UTC: 25.7 S / 35.8 E, VENT MAX= 070 KT, TROPICAL
CYCLONE
28 KT NE: 345 SE: 390 SW: 325 NW: 155
34 KT NE: 240 SE: 270 SW: 220 NW: 150
48 KT NE: 140 SE: 150 SW: 110 NW: 110
64 KT NE: 75 SE: 55 SW: 55 NW: 75

48H: 2021/02/20 18 UTC: 27.0 S / 35.9 E, VENT MAX= 080 KT, TROPICAL
CYCLONE
28 KT NE: 335 SE: 360 SW: 280 NW: 195
34 KT NE: 240 SE: 260 SW: 205 NW: 185
48 KT NE: 130 SE: 150 SW: 110 NW: 100
64 KT NE: 75 SE: 55 SW: 45 NW: 75

60H: 2021/02/21 06 UTC: 28.6 S / 36.9 E, VENT MAX= 085 KT, TROPICAL
CYCLONE
28 KT NE: 370 SE: 350 SW: 315 NW: 260
34 KT NE: 260 SE: 260 SW: 230 NW: 220
48 KT NE: 150 SE: 155 SW: 130 NW: 110
64 KT NE: 85 SE: 55 SW: 55 NW: 85

72H: 2021/02/21 18 UTC: 30.6 S / 39.7 E, VENT MAX= 090 KT, INTENSE
TROPICAL CYCLONE
28 KT NE: 400 SE: 335 SW: 455 NW: 360
34 KT NE: 270 SE: 260 SW: 295 NW: 280
48 KT NE: 140 SE: 165 SW: 140 NW: 120
64 KT NE: 85 SE: 55 SW: 65 NW: 75

2.B LONGER-RANGE OUTLOOK:
96H: 2021/02/22 18 UTC: 34.9 S / 51.2 E, VENT MAX= 070 KT, TROPICAL
CYCLONE
28 KT NE: 470 SE: 435 SW: 405 NW: 400
34 KT NE: 285 SE: 270 SW: 325 NW: 260
48 KT NE: 150 SE: 130 SW: 100 NW: 130
64 KT NE: 110 SE: 95 SW: 75 NW: 85

120H: 2021/02/23 18 UTC: 37.8 S / 61.7 E, VENT MAX= 035 KT,
POST-TROPICAL DEPRESSION
28 KT NE: 455 SE: 335 SW: 315 NW: 260
34 KT NE: 260 SE: 230 SW: 270 NW: 185

2.C ADDITIONAL INFORMATION:
T=CI=3.5

THE CLOUDY CONFIGURATION OF GUAMBE IN CDO WAS MAINTAINED COMPARED TO
THE PREVIOUS 6 HOURS. THE LAST MICROWAVE DATA FROM GMI OF 13H04 AND
SSMIS OF 14H15 AND 14H44, ALLOWED TO RELOCATE THE CENTRE MORE TO THE
WEST THAN FOR THE PREVIOUS WARNING.

A DVORAK ANALYSIS IN CDO ALLOWS TO DEFINE A CI OF 3.5- OR EVEN 3.5.
GUAMBE IS THUS MAINTAINED AT THE MINIMAL STAGE OF STRONG TROPICAL
STORM WITH MAXIMUM WINDS RATHER LOCALIZED IN THE EASTERN SECTOR
ACCORDING TO THE PASS HY-2C OF 12H30.

THE SYSTEM MOVES SLOWLY, UNDER THE INFLUENCE OF OPPOSITE DIRECTIONAL
FLOWS: A SOUTHEASTERLY FLOW GENERATED BY SUBTROPICAL GEOPOTENTIAL
HIGHS AND A NORTHWESTERLY FLOW BY A NEAR EQUATORIAL RIDGE. THE
TRAJECTORY OF GUAMBE HAS RECENTLY TAKEN A MORE SOUTH-WESTERLY
ORIENTATION ON THE WESTERN FACE OF THIS RIDGE. THE DIFFERENT
GUIDANCES ARE MORE AND MORE IN AGREEMENT ON THE GENERAL ORIENTATION
OF THE TRAJECTORY, THE OPTICS OF A RAPPROCHEMENT OF THE MOZAMBICAN
COASTS BEING GLOBALLY LESS PRESENT. THE PRESENT FORECAST OF THE CMRS
FOLLOWS THIS PHILOSOPHY.

AT THE END OF THE WEEK, THE PRESENCE OF A DEEP MID-LATITUDE TROUGH
SOUTH OF THE CANAL SHOULD FAVOR A SOUTH-EASTWARD EVACUATION OF GUAMBE
BUT THE CHRONOLOGY ON THIS ACCELERATION REMAINS UNCERTAIN BETWEEN THE
MODELS FROM SUNDAY ON.

THE ENVIRONMENT OF GUAMBE IS RATHER FAVORABLE TO A REGULAR
INTENSIFICATION, ONLY THE CONVERGENCE OF LOW LEVELS IS STILL
LIMITING. NO CHANGE IN TERMS OF INTENSITY FORECAST: A SLOWER AND THEN
MORE INTENSE INTENSIFICATION OF THE SYSTEM IS EXPECTED. THESE
FAVORABLE CONDITIONS ASSOCIATED WITH A SUFFICIENT OCEANIC POTENTIAL
EVEN AT THESE LATITUDES, SHOULD ALLOW GUAMBE TO REACH THE STAGE OF A
TROPICAL CYCLONE OR EVEN AN INTENSE TROPICAL CYCLONE. AT THE END OF
THE FORECAST PERIOD, ON THE EDGE OF THE MID-LATITUDE TROUGH, THE
NORTHWESTERN SECTOR SHEAR COULD GRADUALLY STRENGTHEN LEADING TO THE
WEAKENING OF THE SYSTEM. AS FOR THE TRACK, THE SPEED OF MOVEMENT OF
THE SYSTEM, WHICH IS INCREASINGLY RAPID IN THE DIRECTION OF THE
SHEAR, MAINTAINS AN UNCERTAINTY ON THE TIMING OF THE WEAKENING. AT
THE END OF THE PERIOD A POST-TROPICAL EVOLUTION IS POSSIBLE DEPENDING
ON THE DEGREE OF INTERACTION WITH THE SUBTROPICAL JET.

EVEN IF THIS PREDICTION MAKES GUAMBE PASS OFF THE MOZAMBICAN COAST,
GUAMBE MAY SIGNIFICANTLY AFFECT THE WEATHER CONDITIONS IN SOUTHERN
MOZAMBIQUE, ESPECIALLY ON FRIDAY AND SATURDAY BETWEEN VILANKULO IN
THE NORTH AND XAI-XAI IN THE SOUTH. HEAVY RAINS THAT CAN REACH AND
LOCALLY EXCEED 150 MM IN 24 HOURS ARE POSSIBLE ON THESE SECTORS.
STRONG WINDS THAT CAN REACH 100 KM/H IN GUSTS ON THE COAST ARE
POSSIBLE FROM FRIDAY. THE RISK OF STORM SURGE IS GLOBALLY LOW IN THE
SECTOR SINCE IN THE WORST CASE SCENARIO, IT IS ESTIMATED AT 1M
(INFERIOR TO 50 CM IN THE MOST PROBABLE SCENARIO) ON THE MAIN PART OF
THE COASTE, BUT MORE ABOUT 1.5 TO 2M AT THE BOTTOM OF THE BAY OF
INHAMBANE. IT COULD BE MORE SIGNIFICANT IF THE TRACK OF THE SYSTEM
WOULD THREATEN MORE DIRECTLY INHAMBANE.
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