WDPN32 PGTW 121500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 25W (MAN-YI) WARNING NR 
015//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.0N 146.3E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 105 NM EAST-NORTHEAST OF NAVSTA GUAM
   MOVEMENT PAST 6 HOURS: WESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
STORM (TS) 25W (MAN-YI) WITH FLARING CONVECTION IN CLOSER PROXIMITY
TO THE LOW-LEVEL CIRCULATION CENTER (LLCC), HOWEVER, REMAINS OFFSET
TO THE SOUTHEAST QUADRANT. THE LLCC HAS BECOME INCREASINGLY
OBSCURED WITH INCREASING CONVECTION BUT HAS ONLY BEEN PARTIALLY
OBSCURED OVER THE LAST FEW HOURS, LENDING HIGH CONFIDENCE TO THE
INITIAL POSITION DURING THE SYSTEMS WESTWARD TRACK TOWARD THE
MARIANAS ISLANDS. THE ANIMATED WATER VAPOR LOOP CONTINUES TO
ILLUSTRATE MODERATE UPPER-LEVEL OUTFLOW EQUATORWARD WITH THE
ASSISTANCE FROM A POINT-SOURCE ALOFT, AIDING IN THE SLOW
INTENSIFICATION OF MAN-YI. ON ANIMATED EIR, THE WESTERN SEMICIRCLE
REMAINS VOID OF ENHANCED CONVECTION, SHOWING LOW-LEVEL CLOUD LINES
WRAPPING INTO THE ASSESSED CENTER, PROVIDING EVIDENCE OF CONTINUED
DRY-AIR ENTRAINMENT. AS STATED ABOVE, THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON THE AFOREMENTIONED PARTIALLY
OBSCURED LLCC ON ANIMATED EIR IMAGERY AND A 120804Z 89 GHZ WSFM
MICROWAVE IMAGE. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON SUBJECTIVE AGENCY ESTIMATES LISTED BELOW, WHILE
CIMSS OBJECTIVE ESTIMATES RANGE BETWEEN 33 KTS AND 39 KTS. LASTLY, A
PARTIAL 121137Z ASCAT-B IMAGE HAS REVEALED A SWATH OF 35 KTS WITHIN
THE EASTERN SEMICIRCLE, IN CLOSE PROXIMITY TO THE PRIMARY
CONVECTIVE STRUCTURE.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE NORTH,
EXTENDING WESTWARD TOWARD TAIWAN. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T3.0 - 45 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 39 KTS AT 121130Z
   CIMSS AIDT: 37 KTS AT 121230Z
   CIMSS D-PRINT: 33 KTS AT 121230Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL STORM 25W IS FORECASTED TO MAINTAIN A
WESTWARD TRACK ALONG THE SOUTHERN PERIPHERY OF THE SUBTROPICAL
RIDGE (STR) LOCATED JUST NORTH OF THE SYSTEM UNTIL TAU 72.
FOLLOWING TAU 72, TS 25W WILL BEGIN AN ANTICYCLONIC NORTHWEST TRACK
ALONG THE SOUTHWESTERN EDGE OF THE STR UNTIL THE END OF THE
FORECAST PERIOD AS THE SYSTEM APPROACHES LUZON AT TAU 120. WITH
REGARD TO INTENSITY, MAN-YI IS EXPECTED TO STEADILY INTENSIFY
DURING THE WESTWARD TRACK, REACHING 50 KTS AS TS 25W NEARS GUAM AND
ROTA WITHIN THE NEXT 12 HOURS. FOLLOWING TAU 12, TS 25W WILL
CONTINUE INTENSIFYING STEADILY TO 105 KTS BY TAU 72 AS DRY AIR
LESSENS WITHIN THE CORE AND VERTICAL WIND SHEAR (VWS) MAINTAINS A
MAGNITUDE BELOW 15 KTS. BETWEEN TAU 72 AND TAU 96, 25W WILL
CONTINUE AT A MAXIMUM INTENSITY OF 105 KTS WITHIN A RELATIVELY
CONDUCIVE ENVIRONMENT. FOLLOWING TAU 96, WESTERLY VWS WILL AGAIN
INCREASE ABOVE 15 KTS WHILE DRY AIR BEGINS ADDING PRESSURE INTO THE
WESTERN SEMICIRCLE. WITH THE ADDITION OF THE AFOREMENTIONED VWS AND
DRY AIR, COOLER SEA SURFACE TEMPERATURES LEFT BEHIND IN THE WAKE OF
TS 27W WILL BEGINS THE SYSTEMS (TS 25W) INITIAL WEAKENING PHASE TO
90 KTS BY TAU 120 AS TROPICAL STORM 25W APPROACHES THE LUZON
STRAIT.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT
OVER THE NEXT 72 HOURS, WITH A CROSS-TRACK SPREAD OF 181 NM. AFTER
TAU 72, MODEL SOLUTIONS BEGIN TO DIVERGE, INCREASING THE
CROSS-TRACK SPREAD TO OVER 500 NM NEAR THE END OF THE FORECAST
PERIOD AS A SLIGHT BIFURCATION IN MODEL SOLUTIONS IS INTRODUCED INTO 
THE NUMERICAL MODEL GUIDANCE. AS OF NOW, NAVGEM AND GFS ILLUSTRATE 
THE NORTHERN MOST SOLUTIONS, SHOWING A RECURVE SCENARIO TOWARD THE 
NORTHERN PHILIPPINE SEA, WHILE THE MAJORITY OF THE OTHER JTWC 
CONSENSUS MEMBERS SHOW A CONTINUED TRACK INTO LUZON. DUE TO THE 
BIFURCATION AFTER TAU 72, CONFIDENCE IS LOW BETWEEN TAU 72 AND TAU 
120. WITH REGARD TO INTENSITY, THE FORECAST IS IN MEDIUM AGREEMENT 
THROUGH THE INITIAL 72 HOURS, WITH EXPECTED STEADY INTENSIFICATION TO 
105 KTS. FOLLOWING TAU 72, THE JTWC FORECAST REMAINS JUST BELOW THE 
INTENSITY CONSENSUS DUE TO AN EXPECTED NON-CONDUCIVE ENVIRONMENT, 
LENDING LOW CONFIDENCE TO THE INTENSITY FORECAST BETWEEN TAU 72 AND 
TAU 120. 

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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