WDPN31 PGTW 250300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 10W (MA-ON) WARNING NR 
015//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.1N 111.7E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 157 NM WEST-SOUTHWEST OF HONG KONG
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 19 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS TREMENDOUS
VERTICAL WINDSHEAR WORKING ON TROPICAL STORM MA-ON. THE LOW LEVEL
CIRCULATION CENTER (LLCC) IS PARTLY EXPOSED WITH THE SYSTEM CENTER
UNDER THE NORTHERNMOST BANDS OF THE CONVECTIVE SHIELD. A 242251Z
SSMIS 37H ALLOWS FOR PRECISE POSITIONING AND VERIFIES THAT THE
SYSTEM MAINTAINS DEEP CONVECTIVE BANDING AROUND MOST OF ITS CORE.
THERE IS A SLIGHT BREAK OVER THE NORTHEAST QUADRANT BUT FOR THE
MOST PART THE SYSTEM REMAINS VIGOROUS. SURFACE REPORTS AND AN
OBSERVATION FROM AN UNFORTUNATE SHIP NEAR THE CENTER CONFIRM THE
INTENSITY. WARM SEA WATERS AND HIGH OCEAN HEAT CONTENT ALONG TRACK
ARE HELPING MA-ON FIGHT THE WINDSHEAR.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK BLEDNED WITH
PERSISTENCE FROM A 
241355Z SCATTEROMETRY PASS OVER THE EASTERN SEMICIRCLE.

CURRENT STEERING MECHANISM: THE SOUTHERN FLANK OF THE SUBTROPICAL
RIDGE OVER EASTERN CHINA. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T3.5 - 55 KTS
   KNES: T3.5 - 55 KTS
   CIMSS SATCON: 48 KTS AT 242252Z
   CIMSS ADT: 39 KTS AT 242350Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 30+ KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: LOW

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TROPICAL STORM MA-ON WILL CONTINUE STEADILY
ALONG A WEST-NORTHWESTWARD BEARING UNTIL IT DIES IN NORTHERN
VIETNAM. ALONG THE WAY IT WILL CROSS THE EXTREME NORTHERN PART OF THE 
LUICHOW PENINSULA WITHOUT LOSING MUCH INTENSITY AND RE-GATHER ITSELF 
OVER THE EXTREMELY WARM WATERS OF THE GULF OF TONKIN. THE STORM IS
ZEROING IN ON A LANDFALL IN THE VICITY OF FANGCHENGANG NEAR THE
VIETNAMESE BORDER. VERTICAL WINDSHEAR WILL INCREASE ALONG THE WAY
BUT THE WARM WATERS WILL SUPPORT THE SYSTEM THROUGH LANDFALL. THE
MOUNTAINOUS TERRAIN OF SOUTHEASTERN CHINA AND NORTHERN VIETNAM WILL
TEAR THE SYSTEM APART WITHIN 15 HOURS OF MAKING LANDFALL, AND IT
WILL BE HARD TO LOCATE THE VORTEX SOONER THAN THAT.   

MODEL DISCUSSION: THERE IS EXCELLENT MODEL AGREEMENT REGARDING BOTH
TRACK AND INTENSITY AND THE SCENARIO OF WESTWARD MOVEMENT ONTO A
LAND MASS IS SIMPLE. THEREFORE THE JWTC TRACK FORECAST CONTINUES TO
RIDE STRAIGHT ON TOP OF THE MULTI-MODEL CONSENSUS AND THE INTENISTY
FORECAST STAYS NEAR THE MEAN UNTIL THE LAST POSITION, WHEN THE
TERRAIN IS CONSIDERED AND THE FORECAST INTENSITY IS DROPPED BELOW 
GUIDANCE. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   INTENSITY 0 - 72 HR: MEDIUM//
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