Subject: Indian-S: 01 Active Tropical Cyclone In Southern Hemisphere

From: SIU Weather Processor <[email-masked]>
Date: Sat, 6 Feb 1999 02:31:51 -0600

948
WTXS31 PGTW 060900 AA
1. TROPICAL CYCLONE 18S WARNING NR 007
   01 ACTIVE TROPICAL CYCLONE IN SOUTHERN HEMISPHERE
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
    ---
   WARNING POSITION:
   060600Z2 --- NEAR 18.4S3 110.3E5
     MOVEMENT PAST SIX HOURS - 295 DEGREES AT 09 KTS
     POSITION ACCURATE TO WITHIN 060 NM
     POSITION BASED ON CENTER LOCATED BY SATELLITE
   PRESENT WIND DISTRIBUTION:
   MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT
   RADIUS OF 035 KT WINDS - 120 NM SOUTHWEST SEMICIRCLE
                            060 NM ELSEWHERE
   REPEAT POSIT: 18.4S3 110.3E5
    ---
   FORECASTS:
   12 HRS, VALID AT:
   061800Z5 --- 17.9S7 109.2E2
   MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT
   RADIUS OF 035 KT WINDS - 120 NM SOUTHWEST SEMICIRCLE
                            060 NM ELSEWHERE
   VECTOR TO 24 HR POSIT: 270 DEG/ 06 KTS
    ---
   24 HRS, VALID AT:
   070600Z3 --- 17.9S7 107.9E7
   MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT
   RADIUS OF 035 KT WINDS - 120 NM SOUTHWEST SEMICIRCLE
                            060 NM ELSEWHERE
   VECTOR TO 36 HR POSIT: 265 DEG/ 08 KTS
    ---
   36 HRS, VALID AT:
   071800Z6 --- 18.0S9 106.3E0
   MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT
   RADIUS OF 035 KT WINDS - 130 NM SOUTHWEST SEMICIRCLE
                            070 NM ELSEWHERE
   VECTOR TO 48 HR POSIT: 265 DEG/ 09 KTS
    ---
   EXTENDED OUTLOOK:
   48 HRS, VALID AT:
   080600Z4 --- 18.1S0 104.5E0
   MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT
   RADIUS OF 035 KT WINDS - 130 NM SOUTH SEMICIRCLE
                            070 NM ELSEWHERE
   VECTOR TO 72 HR POSIT: 270 DEG/ 09 KTS
    ---
   72 HRS, VALID AT:
   090600Z5 --- 18.2S1 100.9E0
   MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT
   RADIUS OF 035 KT WINDS - 130 NM SOUTH SEMICIRCLE
                            070 NM ELSEWHERE
    ---
REMARKS:
060900Z5 POSITION NEAR 18.3S2  110.0E2.
TROPICAL CYCLONE 18S HAS TRACKED TOWARDS THE WEST-NORTHWEST AT 9
KNOTS DURING THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON
060530Z4 VISIBLE SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED
ON SATELLITE CURRENT INTENSITY ESTIMATES AND A 051534Z8
SCATTEROMETER PASS REFLECTING A MINIMUM OF 35 KNOTS WITH A
SOUTHWESTWARDLY DISPLACED LOW LEVEL WINDFIELD. TC 18S HAS CONTINUED
TO MOVE UNDER THE STEERING INFLUENCE OF THE SUBTROPICAL RIDGE TO THE
SOUTH. SINCE THE LOW LEVEL CIRCULATION IS FULLY EXPOSED AND SHEARED
EAST FROM THE SIGNIFICANT CONVECTION, THE SYSTEM HAS ENCOUNTERED
WEAKER STEERING FLOW FROM THE LOW TO MID LEVELS OF THE ATMOSPHERE.
TC 18S IS FORECAST TO SLOW WHILE CONTINUING TO TRACK WEST-
NORTHWESTWARD DURING THE INITIAL 12 HOURS OF THE FORECAST. THE
SYSTEMS IS EXPECTED TO RETURN TO MORE OF A WESTWARD TRACK AFTER THE
12 HOUR POSITION AND THROUGHOUT THE REMAINDER OF THE 72 HOUR
FORECAST PERIOD. DUE TO MODERATE SHEAR AND FAIR OUTFLOW ALOFT, THE
SYSTEM IS NOT FORECAST TO INCREASE INTENSITY DURING THE FIRST 36
HOURS. AFTERWARDS, THE SYSTEM IS EXPECTED TO INTENSIFY SLIGHTLY
UNDER CONDITIONS OF DECREASING SHEAR AND IMPROVED OUTFLOW. AN
ALTERNATE SCENARIO WOULD INVOLVE WEAKER STEERING FLOW CAUSING AN
EVEN SLOWER FORWARD SPEED AND POSSIBLY A SHORT TERM CYCLONINC TURN
IN THE TRACK. AFTERWARDS, THE SYSTEM WOULD AGAIN TRACK TOWARDS THE
WEST AS CURRENTLY FORECASTED. MAXIMUM SIGNIFICANT WAVE HEIGHT AT
060600Z IS 15 FEET. REFER TO WWIO30 PGFW FOR ADDITIONAL SEA HEIGHT
INFORMATION. NEXT WARNINGS AT 061500Z2 (DTG 061355Z0), 062100Z9 (DTG
061955Z6), 070300Z0 (DTG 070155Z8) AND 070900Z6 (DTG 070755Z4).
//
BT
#7662

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
To unsubscribe from WX-TROPL send e-mail to [email-masked] with
"unsub wx-tropl" in the body of your message.  For help with the
WX-TROPL or WX-TALK discussion groups write to [email-masked] or see
http://www.inlink.com/~landmb/intro.html.  For more information on
tropical weather products, see the NCEP Products Homepage at
http://www.nhc.noaa.gov/nhcprod.html.