1. TROPICAL STORM 01W (SONAMU) WARNING NR 015
01 ACTIVE TROPICAL CYCLONE IN NORTHWESTPAC
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
WIND RADII VALID OVER OPEN WATER ONLY
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WARNING POSITION:
070000Z --- NEAR 6.7N 107.9E
MOVEMENT PAST SIX HOURS - 250 DEGREES AT 06 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
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 034 KT WINDS - 070 NM NORTHEAST QUADRANT
065 NM SOUTHEAST QUADRANT
065 NM SOUTHWEST QUADRANT
085 NM NORTHWEST QUADRANT
REPEAT POSIT: 6.7N 107.9E
REMARKS:
070300Z POSITION NEAR 6.6N 107.6E.
TROPICAL STORM 01W (SONAMU), LOCATED APPROXIMATELY 250 NM SOUTH-
SOUTHEAST OF HO CHI MINH CITY, VIETNAM, HAS TRACKED WEST-
SOUTHWESTWARD AT 06 KNOTS OVER THE PAST SIX HOURS. MAXIMUM
SIGNIFICANT WAVE HEIGHT AT 070000Z IS 15 FEET. NEXT WARNINGS AT
070900Z, 071500Z, 072100Z AND 080300Z.//
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WDPN31 PGTW 070300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 01W (SONAMU) WARNING NR
15//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM 01W (SONAMU), LOCATED APPROXIMATELY 250 NM SOUTH-
SOUTHEAST OF HO CHI MINH CITY, VIETNAM, HAS TRACKED WEST-
SOUTHWESTWARD AT 06 KNOTS OVER THE PAST SIX HOURS. ANIMATED
MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS AN INCREASE IN DEEP
CONVECTION BUILDING ALONG THE SOUTHERN HALF OF THE BROADENING LOW
LEVEL CIRCULATION CENTER (LLCC) OVER THE PAST SIX HOURS. THE OVERALL
STRUCTURE OF THE LLCC STILL APPEARS TO OPENING ALONG THE EASTERN
HALF. THE TOTAL PRECIPITABLE WATER LOOP CONTINUES TO INDICATE A
POCKET OF DRY AIR IS WRAPPING ALONG THE EASTERN HALF OF THE LLCC
TOWARDS THE SYSTEM CENTER. UPPER LEVEL ANALYSIS HAS BEEN CONSISTENT
OVER THE PAST 12 HOURS WITH THE LLCC REMAINING SOUTH OF A
SUBTROPICAL RIDGE (STR) AXIS IN A MODERATE TO HIGH VERTICAL WIND
SHEAR (VWS) ENVIRONMENT (20 TO 30 KNOTS). THE CURRENT INTENSITY HAS
BEEN MAINTAINED BASED ON THE WEAKENING OF THE LLCC IN MSI OFFSETTING
THE IMPROVED CONVECTION. SEA SURFACE TEMPERATURES HAVE BEEN STEADY
AT 27 TO 28 DEGREES CELSIUS, SUPPORTING THE SLOW WEAKENING TREND
OVER THE PAST 24 HOURS.
3. FORECAST REASONING.
A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
B. TS 01W WILL TRACK SLOWLY ALONG THE SOUTHERN PERIPHERY OF THE
LOW- TO MID-LEVEL STR OVER THE ANDAMAN SEA IN A GENERALLY WEST-
SOUTHWESTWARD DIRECTION THROUGH TAU 48, AFTER WHICH THE WEAKENED
LLCC IS FORECAST TO DEFLECT EQUATORWARD. VWS IS EXPECTED TO REMAIN
HIGH THROUGHOUT THE REMAINDER OF THE FORECAST PERIOD. THE HIGH VWS
AND DRY AIR ENTRAINMENT WILL MAKE THE ENVIRONMENT INCREASINGLY
UNFAVORABLE. MESOSCALE MODEL GUIDANCE INDICATES TS 01W WILL CONTINUE
A GRADUAL WEAKENING TREND AND DISSIPATE BELOW WARNING INTENSITY BY
TAU 72 AS A RESULT OF THESE NEGATIVE FACTORS. CONDITIONS WILL BE
CLOSELY MONITORED FOR ANY SIGNS OF IMPROVEMENT IN THE ENVIRONMENTAL
CONDITIONS OR THE ORGANIZATION OF THE LLCC, AND THE FORECAST LENGTH
MAY BE ADJUSTED IF WARRANTED. THE AVAILABLE DYNAMIC MODEL GUIDANCE
IS IN FAIR AGREEMENT WITH A WEST-SOUTHWESTWARD TRACK. THE OFFICIAL
FORECAST IS TO THE WEST OF THE CONSENSUS OF AVAILABLE MODEL GUIDANCE
TO ACCOUNT FOR THOSE MEMBERS SHOWING A MORE AGGRESSIVE TURN TO THE
SOUTHEAST (GFS AND GFDN). DUE TO THE LARGE SPREAD IN THE GUIDANCE,
THERE IS LOW CONFIDENCE IN THE JTWC FORECAST.//
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