Indian-S: TD4 W5
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Weather Alert@21:1/175 to
All on Wed Dec 23 16:00:00 2020
WTIO30 FMEE 231242
RSMC / TROPICAL CYCLONE CENTER / LA REUNION
TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN)
0.A WARNING NUMBER: 5/4/20202021
1.A TROPICAL DEPRESSION 4
2.A POSITION 2020/12/23 AT 1200 UTC:
WITHIN 20 NM RADIUS OF POINT 14.7 S / 60.4 E
(FOURTEEN DECIMAL SEVEN DEGREES SOUTH AND
SIXTY DECIMAL FOUR DEGREES EAST)
MOVEMENT: WEST 5 KT
3.A DVORAK ANALYSIS: 2.0/2.5/W 0.5/6 H
4.A CENTRAL PRESSURE: 999 HPA
5.A MAX AVERAGE WIND SPEED (10 MN): 30 KT
RADIUS OF MAXIMUM WINDS (RMW): NIL
6.A EXTENSION OF WIND BY QUADRANTS (KM):
28 KT NE: 0 SE: 390 SW: 335 NW: 0
7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1008 HPA / 1300 KM
8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION: MEDIUM
1.B FORECASTS (WINDS RADII IN KM):
12H: 2020/12/24 00 UTC: 14.8 S / 59.3 E, VENT MAX= 030 KT, TROPICAL
DEPRESSION
28 KT NE: 0 SE: 240 SW: 360 NW: 0
24H: 2020/12/24 12 UTC: 15.1 S / 57.7 E, VENT MAX= 035 KT, MODERATE
TROPICAL STORM
28 KT NE: 100 SE: 240 SW: 360 NW: 75
34 KT NE: 0 SE: 45 SW: 45 NW: 0
36H: 2020/12/25 00 UTC: 15.3 S / 56.2 E, VENT MAX= 035 KT, MODERATE
TROPICAL STORM
28 KT NE: 120 SE: 240 SW: 360 NW: 75
34 KT NE: 0 SE: 45 SW: 45 NW: 0
48H: 2020/12/25 12 UTC: 15.4 S / 54.8 E, VENT MAX= 040 KT, MODERATE
TROPICAL STORM
28 KT NE: 140 SE: 240 SW: 360 NW: 75
34 KT NE: 35 SE: 55 SW: 55 NW: 65
60H: 2020/12/26 00 UTC: 15.5 S / 53.4 E, VENT MAX= 040 KT, MODERATE
TROPICAL STORM
28 KT NE: 150 SE: 240 SW: 360 NW: 75
34 KT NE: 35 SE: 65 SW: 65 NW: 65
72H: 2020/12/26 12 UTC: 15.6 S / 52.1 E, VENT MAX= 045 KT, MODERATE
TROPICAL STORM
28 KT NE: 165 SE: 240 SW: 360 NW: 75
34 KT NE: 35 SE: 65 SW: 65 NW: 65
2.B LONGER-RANGE OUTLOOK:
96H: 2020/12/27 12 UTC: 15.8 S / 49.2 E, VENT MAX= 035 KT, MODERATE
TROPICAL STORM
28 KT NE: 205 SE: 240 SW: 360 NW: 75
34 KT NE: 35 SE: 85 SW: 0 NW: 0
120H: 2020/12/28 12 UTC: 18.1 S / 45.0 E, VENT MAX= 020 KT, OVERLAND
DEPRESSION
2.C ADDITIONAL INFORMATION:
THE UNFAVORABLE PHASE OF THE DIURNAL CYCLE OF OCEANIC CONVECTION,
REVEALED A LOW LEVELS VORTEX QUITE WELL DEFINED BUT TOTALLY EXPOSED
TO THE NORTH OF THE DEEP CONVECTION. RECENTLY, DEEP CONVECTION HAS
TRIED TO RESTART NEAR THE CENTER. THE SATELLITE CONFIGURATION HAS
THEREFORE NOT IMPROVED DURING THE LAST 6 HOURS AND THE INTENSITY IS
MAINTAINED AT 30 KT. THESE STRONG WINDS REMAIN ONLY PRESENT IN THE
SOUTHERN SEMICIRCLE OF THE SYSTEM.
THE EAST-NORTH-EASTERLY SHEAR CONSTRAINT AND ESPECIALLY THE PRESENCE
OF DRY AIR IN THE MID-LEVELS, CONTINUE TO MAKE THE CYCLOGENESIS
PROCESS EXTREMELY LABORIOUS .... FOR THE NEXT TWO DAYS, A SLOW
INTENSIFICATION REMAINS EXPECTED. THEREAFTER, THE SYSTEM SHOULD
EVOLVE IN A MOISTER ENVIRONMENT, LESS SHEAR WITH AN EXCELLENT
EQUATORIAL UPPER LEVELS DIVERGENCE. IT COULD THEN UNDERGO A MORE
MARKED INTENSIFICATION PHASE BEFORE REACHING THE EAST COAST OF
MADAGASCAR. THE INTENSITY FORECAST REMAINS MORE UNCERTAIN THAN
NORMAL. IT LIES BETWEEN THE DYNAMICAL GUIDANCE WHICH SHOW LITTLE OR
NO STRENGTHENING AND THE STATISTICO-DYNAMICAL GUIDANCE WHICH PROPOSE
A MORE FRANK DEEPENING.
LITTLE CHANGE IN THE TRACK FORECAST: THE SYSTEM SHOULD MOVE ON THE
NORTH TO NORTH-WESTERN EDGE OF THE LOW TO MID LEVELS SUBTROPICAL
HIGHS.
THE INHABITANTS OF THE NORTHERN HALF OF THE EAST COAST OF MADAGASCAR
(MAINLY NORTH OF 20S, NOTABLY BETWEEN THE CITIES OF TAMATAVE IN THE
SOUTH AND SAMBAVA IN THE NORTH) ARE INVITED TO MONITOR THE PROGRESS
OF THIS SYSTEM DURING THE NEXT FEW DAYS.
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