WTIO30 FMEE 301828
RSMC / TROPICAL CYCLONE CENTER / LA REUNION
TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN)

0.A WARNING NUMBER: 29/4/20202021
1.A OVERLAND DEPRESSION 4 (CHALANE)

2.A POSITION 2020/12/30 AT 1800 UTC:
WITHIN 60 NM RADIUS OF POINT 18.9 S / 31.2 E
(EIGHTEEN DECIMAL NINE DEGREES SOUTH AND
THIRTY ONE DECIMAL TWO DEGREES EAST)
MOVEMENT: WEST 15 KT

3.A DVORAK ANALYSIS: NIL
4.A CENTRAL PRESSURE: 1005 HPA
5.A MAX AVERAGE WIND SPEED (10 MN): 25 KT
RADIUS OF MAXIMUM WINDS (RMW): NIL

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

7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): NIL
8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION: MEDIUM

1.B FORECASTS (WINDS RADII IN KM):
12H: 2020/12/31 06 UTC: 19.8 S / 27.6 E, VENT MAX= 025 KT, OVERLAND
DEPRESSION

24H: 2020/12/31 18 UTC: 20.9 S / 24.4 E, VENT MAX= 025 KT, OVERLAND
DEPRESSION

36H: 2021/01/01 06 UTC: 21.3 S / 21.7 E, VENT MAX= 025 KT, OVERLAND
DEPRESSION

48H: 2021/01/01 18 UTC: 21.5 S / 19.2 E, VENT MAX= 025 KT, OVERLAND
DEPRESSION

60H: 2021/01/02 06 UTC: 21.5 S / 16.7 E, VENT MAX= 025 KT, OVERLAND
DEPRESSION


2.B LONGER-RANGE OUTLOOK:
NIL


2.C ADDITIONAL INFORMATION:
OVER THE LAST 6 HOURS, THE DEEP CONVECTION ASSOCIATED WITH THE CORE
OF THE SYSTEM HAS COLLAPSED RAPIDLY. IT IS DEVELOPING LOCALLY,
HOWEVER, FAR FROM THE CENTER, ON THE PERIPHERY OF THE CIRCULATION IN INTERACTION WITH THE HIGHLANDS INLAND. WHILE SATELLITE IMAGERY SHOWS
ONLY THE MID TO UPPER TROPOSPHERE CIRCULATION, PROBABLY SHIFTED TO
THE WEST DUE TO THE STRONG EAST-SOUTHEAST WIND SHEAR, IT IS NO LONGER
POSSIBLE TO DISTINGUISH THE LOW-LEVEL CIRCULATION. THE INITIAL
POSITION IS THEREFORE VERY UNCERTAIN.

CHALANE CONTINUES TO TRACK RAPIDLY WESTWARD, ON THE NORTHERN FACE OF
THE SUBTROPICAL RIDGE WHICH WILL BE REPLACED TOMORROW BY AN OTHER
RIDGE CENTERED OVER THE SOUTHERN ATLANTIC. AVAILABLE TRACK GUIDANCE
BECOME MORE ERRATIC AS THE SYSTEM LOOSES ITS DEFINITION OVER LAND,
MAKING THE TRACK FORECAST RATHER UNCERTAIN. HOWEVER, THERE IS STILL A
CONSENSUS OVER A GLOBALLY WESTWARD TRACK.

IF RAINFALL DIRECTLY RELATED TO CHALANE HAS DECREASED AT THE MOMENT,
IT COULD AT TIMES RESUME NEAR THE RESIDUAL LOW PRESSURE SYSTEM OVER
THE NEXT 2-3 DAYS. CUMULATIVE RAINFALL COULD THEN REACH 50 TO 100 MM
IN 24 HOURS ON SOME AREAS ALONG THE FORECAST TRACK AND LOCALLY EXCEED
150 MM. THESE RAINS MAY CAUSE FLASH FLOODS AND FLOODS. THEY WILL
SPREAD FAR INLAND OVER ZIMBABWE, BOTSWANA FROM DECEMBER 31, AND EVEN
NAMIBIA (EASTERN PART IN PARTICULAR) ON JANUARY 1.

THIS IS THE LAST ADVISORY ON THIS SYSTEM. ADDITIONAL INFORMATION WILL
BE AVAILABLE ON OUR DAILY TROPICAL WEATHER DISCUSSION BULLETIN AWIO20
FMEE ISSUED AT 12Z.
=
--- SBBSecho 3.11-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (21:1/175)