Subject: Indian-S: 1. Tropical Cyclone 12s (alda) Warning Nr 004

From: SIU Weather Processor <[email-masked]>
Date: Mon, 18 Jan 1999 08:18:02 -0600

999
WTXS31 PGTW 181500
IMMEDIATE DELIVERY REQ TO AMEMBASSY PORT LOUIS
1. TROPICAL CYCLONE 12S (ALDA) WARNING NR 004
   02 ACTIVE TROPICAL CYCLONES IN SOUTHEB#35)###-M;GKUKS)M;W4JS-U#; O
NE-MINUTE AVERAGE
    ---
   WARNING POSITION:
   181200Z2 --- NEAR 28.0S0 39.2E4
     MOVEMENT PAST SIX HOURS - 170 DEGREES AT 09 KTS
     POSITION ACCURATE TO WITHIN 090 NM
     POSITION BASED ON CENTER LOCATED BY SATELLITE
   PRESENT WIND DISTRIBUTION:
   MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT
   RADIUS OF 050 KT WINDS - 025 NM
   RADIUS OF 035 KT WINDS - 110 NM EAST SEMICIRCLE
                            085 NM ELSEWHERE
   REPEAT POSIT: NEAR 28.0S0 39.2E4
    ---
   FORECASTS:
   12 HRS, VALID AT:
   190000Z0 --- 29.6S7 39.7E9
   MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT
   BECOMING EXTRATROPICAL
   RADIUS OF 035 KT WINDS - 120 NM NORTHEAST SEMICIRCLE
                            075 NM ELSEWHERE
   VECTOR TO 24 HR POSIT: 145 DEG/ 10 KTS
    ---
   24 HRS, VALID AT:
   191200Z3 --- 31.3S7 41.0E5
   MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT
   BECOMING EXTRATROPICAL
   RADIUS OF 035 KT WINDS - 120 NM NORTHEAST SEMICIRCLE
                            070 NM ELSEWHERE
   VECTOR TO 36 HR POSIT: 125 DEG/ 14 KTS
    ---
   36 HRS, VALID AT:
   200000Z2 --- 32.9S4 43.6E3
   MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT
   EXTRATROPICAL
    ---
REMARKS:
181500Z5 POSITION NEAR 28.4S4 39.3E5.
TROPICAL CYCLONE 12S (ALDA) HAS TRACKED SOUTHWARD AT 9 KNOTS OVER
THE PAST 6 HOURS WEST-SOUTHWEST OF MADAGASCAR. THE WARNING POSITION
IS BASED UPON 181100Z1 ANIMATED VISIBLE SATELLITE IMAGERY AND IS
CONSISTENT WITH EARLIER MICROWAVE IMAGERY FIXES. THE WARNING
INTENSITY IS BASED UPON AN 181100Z1 VISIBLE SATELLITE CURRENT
INTENSITY ESTIMATE OF 55 KNOTS. TROPICAL CYCLONE 12S (ALDA) IS
CURRENTLY UNDER THE STEERING INFLUENCE OF A RIDGE TO ITS EAST AND
SOUTH. WITHIN THE NEXT 12 TO 24 HOURS, THE RIDGE IS FORECAST TO
BECOME NORTHWEST TO SOUTHEAST ORIENTED, AND TC 12S (ALDA) WILL BEGIN
TO TRACK SOUTHEASTWARD. AS TC 12S (ALDA) MOVES POLEWARD OF THE
RIDGE, IT WILL ACCELERATE INTO THE SOUTHERN INDIAN OCEAN AND BEGIN
ITS EXTRATROPICAL TRANSITION. TROPICAL CYCLONE 12S (ALDA) SHOULD
WEAKEN SLIGHTLY IN INTENSITY AS THE SYSTEM MOVES INTO COLDER WATERS
AND BEGINS EXTRATROPICAL TRANSITION. ALTHOUGH TROPICAL CYCLONE 12S
(ALDA) APPEARS TO HAVE BOTH TROPICAL AND SUBTROPICAL HARACTERISTICS,
IT HAS YET TO UNDERGO  EXTRATROPICAL TRANSITION. SINCE TC 12S (ALDA)
HAS INDEED INTENSIFIED OVER THE PAST 24 HOURS BEFORE UNDERGOING
TRANSITION, JTWC HAS REGENERATED THE WARNINGS UNTIL TC 12S (ALDA)
UNDERGOES FULL EXTRATROPICAL TRANSITION. MAXIMUM SIGNIFICANT WAVE
HEIGHT AT 181200Z2 IS 20 FEET. NEXT WARNINGS AT 190300Z3 (DTG
190153Z9) AND 191500Z6 (DTG 191353Z2). REFER TO TROPICAL CYCLONE 11P
(DANI) WARNINGS (WTPS31 PGTW) FOR TWELVE-HOURLY UPDATES.//

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