WDPN32 PGTW 112100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 25W (MAN-YI) WARNING NR 
012//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.0N 151.0E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 375 NM EAST OF NAVSTA GUAM
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
STORM 25W (MAN-YI) WITH A COMPACT APPEARANCE AND DISORGANIZED
CONVECTION OBSCURING THE LOW-LEVEL CIRCULATION CENTER (LLCC).
ENVIRONMENTAL ANALYSIS INDICATES THAT 25W IS IN A MARGINALLY
FAVORABLE ENVIRONMENT FOR DEVELOPMENT CHARACTERIZED BY MODERATE
EQUATORWARD OUTFLOW ALOFT, MODERATE (15-20 KTS) VERTICAL WIND
SHEAR, DRY AIR TO THE NORTHWEST, AND WARM (29-30 C) SEA SURFACE
TEMPERATURES. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE
BASED ON THE LOW-LEVEL CLOUD LINES IN THE ANIMATED EIR IMAGERY. THE
INITIAL INTENSITY OF 40 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON THE AGENCY DVORAK AND OBJECTIVE INTENSITY ESTIMATES LISTED
BELOW.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A SUBTROPICAL
RIDGE (STR) TO THE NORTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T2.5 - 35 KTS
   CIMSS ADT: 45 KTS AT 111800Z
   CIMSS AIDT: 39 KTS AT 111800Z
   CIMSS DPRINT: 36 KTS AT 111800Z
   CIMSS DMINT: 41 KTS AT 111558Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD
   OTHER FACTORS: DRY AIR TO THE NORTHWEST OF THE LLCC.

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: AFTER TAU 48, INTENSITY IS RAISED
WITH A PEAK INTENSITY OF 90 KTS RATHER THAN 65 KTS AS DEPICTED IN
THE PREVIOUS WARNING. 

FORECAST DISCUSSION: 25W IS FORECAST TO TRACK GENERALLY WESTWARD
THROUGH TAU 96 ALONG THE SOUTHERN PERIPHERY OF THE STR TO THE NORTH
WITH LANDFALL IN GUAM EXPECTED JUST BEFORE TAU 36. AFTER TAU 96,
THE STR WILL REORIENT AND PROPAGATE EASTWARD, ALLOWING 25W TO BEGIN
TRACKING MORE NORTHWESTWARD. REGARDING INTENSITY, THE SYSTEM IS
EXPECTED TO GRADUALLY INCREASE TO AROUND 55 KTS AT TAU 48 AS THE
VERTICAL WIND SHEAR REMAINS MODERATE AND DRY AIR CONTINUES TO BE
PRESENT. HOWEVER, AFTER TAU 48, THE ENVIRONMENT IS FORECAST TO
IMPROVE WITH LOWER SHEAR AND HIGHER MOISTURE CONTENT. AS A RESULT,
25W IS FORECAST TO INTENSIFY TO A PEAK OF AROUND 90 KTS AT TAU 96.
AFTER TAU 96, THE SYSTEM WILL BEGIN TO TRAVERSE THROUGH THE COOLER
AND LOWER OHC WATERS LEFT BEHIND FROM 26W AND 27W. THIS WILL CAUSE
A STAGNANT INTENSITY THROUGH THE REMAINDER OF THE FORECAST PERIOD. 

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN TIGHT AGREEMENT
THROUGH TAU 72, WITH THE EXCEPTION OF NAVGEM, WHICH TRACKS THE
VORTEX MORE NORTHWARD THAN THE REMAINDER OF GUIDANCE. WITHIN THE
MAIN GROUPING THERE IS A 70 NM CROSS-TRACK SPREAD AT TAU 72. AFTER
TAU 72, MODELS BEGIN TO DIVERGE WITH A CROSS-TRACK SPREAD OF 280 NM
AT TAU 120 AS THE TRACK AROUND THE SOUTHWESTERN PERIPHERY OF THE
STR VARIES. DUE TO THIS, THE JTWC TRACK FORECAST IS PLACED CLOSE TO
CONSENSUS WITH HIGH CONFIDENCE THROUGH TAU 72 AND MEDIUM CONFIDENCE
THEREAFTER. INTENSITY GUIDANCE IS IN WORSE AGREEMENT WITH A LARGE
SPREAD IN GUIDANCE AFTER TAU 72. COAMPS-TC SUGGESTS A PEAK OF
AROUND 70 KTS WHILE GFS, HAFS-A, AND HWRF SUGGEST A PEAK OF 95-115
KTS. THE JTWC INTENSITY FORECAST IS PLACED CLOSE TO CONSENSUS
THROUGH TAU 48 AND SLIGHTLY BELOW THE MAIN GROUPING THROUGH TAU
120.

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