WDPN32 PGTW 100300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 25W (MAN-YI) WARNING NR 
005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.2N 156.1E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 598 NM EAST OF SAIPAN
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS TROPICAL STORM
25W (MAN-YI) IS ENTERING THE PEAK PHASE OF ITS RUN. EIR ANIMATION
SHOWS COOLING TOPS IN THE CORE AND IMPROVING ORGANIZATION DURING
THE PAST SIX HOURS. AGENCY FIXES ARE STILL HAVING DIFFICULTY
PINNING DOWN THE EXACT CENTER BUT GENERALLY AGREE THAT THE LOW LEVEL 
CIRCULATION CENTER IS ON THE NORTHWESTERN PERIPHERY OF THE DEEP 
CONVECTION.  THE CURRENT INTENSITY IS BASED ON DVORAK ESTIMATES OF 
T2.5 (42KTS) FROM RJTD AND T3.0 FROM RCTP. OBJECTIVE ASSESSMENTS FROM 
CIMSS ARE SOLIDLY IN THE 40 TO 50KT RANGE. WATER VAPOR ANIMATION 
SHOWS THE EARLIEST HINTS OF ENCROACHING WESTERLY SHEAR ON THE 
POLEWARD FLANK OF THE SYSTEM ARE SHOWING AND OVERALL VERTICAL WIND 
SHEAR HAS INCREASED TO THE 15-20KT RANGE. THERE IS DISCERNABLE 
IMPINGEMENT SHOWING ON THE NORTHWEST QUADRANT OF THE SYSTEM. TOTAL 
PRECIPITABLE WATER LOOPS ALSO SHOW THE DEEP MOISTURE FIELD BETWEEN 
INVEST 94W AND TS 25W BECOMING STRETCHED, FORESHADOWING A DRIER AND 
MORE HOSTILE ENIVORNMENT UPSTREAM.

INITIAL WIND RADII BASIS: PERSISTENCE. 

CURRENT STEERING MECHANISM: TS 25W IS MOVING THROUGH A WEAKNESS
BETWEEN THE SOUTHWESTERN FLANK OF THE MAIN SUBTROPICAL RIDGE.  


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T3.0 - 45 KTS
   CIMSS SATCON: 47 KTS AT 092041Z
   CIMSS ADT: 51 KTS AT 092330Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   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 MAN-YI WILL ATTAIN PEAK
INTENSITY DURING THE NEXT 12 HOURS. THE ENVIRONMENT IMMEDIATELY
UPSTREAM REMAINS MODERATELY FAVORABLE BUT IT WILL NOT BE LONG
BEFORE THE SYSTEM MOVES INTO A REGION OF DRIER AIR AND HIGHER
WESTERLY VERTICAL WIND SHEAR.  MAN-YI HAS LOST ITS PUSH FROM THE
SUBTROPICAL RIDGE FAR TO EAST AND IS CURRENTLY TRACKING THROUGH A
WEAKNESS BETWEEN THE MAIN RIDGE AND THE PHILIPPINE SEA RIDGE. THE
JTWC STREAMLINE ANALYSIS SHOWS A STABLE ANTICYCLONE ANCHORED JUST
TO THE NORTHEAST OF LUZON. AS THE SYSTEM TRACKS TOWARDS THE PHILSEA
IT WILL ENCOUNTER INCREASING WESTERLY SHEAR AND SUBSTANTIALLY
INCREASING DRY AIR ENTRAINMENT. GUIDANCE HAS BEEN STEADY THAT THE
SYSTEM WILL CLEAR SAIPAN TO THE NORTH, CROSSING THE MARIANAS VERY
NEAR THE 20TH LATITUDE WHILE AT MINIMAL TROPICAL STORM STRENGTH IF
THAT.  INCREASING SHEAR AND DRY AIR ENTRAINMENT MAY KILL THE SYSTEM
IN THE PHILIPPINE SEA, ALTHOUGH THAT IS NOT A CERTAINTY AT THIS
POINT. SOME OF THE MOST AGGRESSIVE GUIDANCE INDICATES A POTENTIAL
THAT THE VORTEX MAY SURVIVE BUT EVEN IF THAT OCCURS THE SYSTEM WILL
REMAIN VERY WEAK.  

MODEL DISCUSSION: CROSS-TRACK SPREAD HAS INCREASED SINCE THE LAST
RUN BUT THAT IS DUE TO THE DECREASING INTENSITY.  NONETHELESS THE
TRACK GUIDANCE REMAINS REASONABLY TIGHT. THE INTENSITY GUIDANCE HAS
COME DOWN A LITTLE BUT IS SHOWING THE SAME TREND, WITH A SYSTEM
PEAK DURING THE NEXT 12 HOURS AND A STEADY DECLINE THEREAFTER. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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