WDPN32 PGTW 162100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 25W (MAN-YI) WARNING NR 032//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.3N 123.8E
   INITIAL INTENSITY: 120 KTS
   GEOGRAPHIC REFERENCE: 164 NM EAST OF MANILA, PHILIPPINES
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 40 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TYPHOON
25W (MAN-YI) WITH A SLIGHTLY DEGRADED APPEARANCE OVER THE PAST 6
HOURS. THE WESTERN SEMICIRCLE OF THE SYSTEM HAS BECOME LESS
ORGANIZED AND CLOUD TOPS HAVE WARMED, SUGGESTING A BIT OF WEAKENING
SINCE THE PREVIOUS LANDFALL ON CATANDUANES ISLAND. HOWEVER, THE EYE
APPEARS TO BE STARTING TO RECOVER AND CLEAR OUT AS THE SYSTEM
PASSES NORTH OF THE BICOL PENINSULA. ENVIRONMENTAL ANALYSIS
INDICATES THAT 25W IS IN A FAVORABLE ENVIRONMENT CHARACTERIZED BY
STRONG RADIAL OUTFLOW ALOFT, LOW (5-10 KTS) VERTICAL WIND SHEAR,
AND WARM (28-29 C) SEA SURFACE TEMPERATURES. THE INITIAL POSITION
IS PLACED WITH HIGH CONFIDENCE BASED ON THE EYE IN ANIMATED EIR
SATELLITE IMAGERY. THE INITIAL INTENSITY OF 120 KTS IS ASSESSED
WITH MEDIUM CONFIDENCE BASED ON AGENCY DVORAK AND OBJECTIVE
INTENSITY ESTIMATES LISTED BELOW. ADDITIONALLY, A PARTIAL 160959Z
RCM-3 SAR IMAGE SHOWED A MAX OF 122 KNOTS IN THE NORTHERN SECTOR OF
THE EYEWALL.

INITIAL WIND RADII BASIS: SAR DATA 

CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTHEAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.5 - 127 KTS
   RJTD: T7.0 - 140 KTS 
   RCTP: T7.0 - 140 KTS 
   KNES: T6.0 - 115 KTS
   CIMSS ADT: 122 KTS AT 161800Z
   CIMSS AIDT: 118 KTS AT 161800Z
   CIMSS DPRINT: 117 KTS AT 161800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG RADIAL
   OTHER FACTORS: MARGINAL TERRAIN INTERACTION WITH THE BICOL
PENINSULA.

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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: 25W IS FORECAST TO CONTINUE TRACKING
NORTHWESTWARD ALONG THE SOUTHWESTERN PERIPHERY OF THE STR TO THE
NORTHEAST THROUGH TAU 12 AS IT APPROACHES THE EASTERN COAST OF
LUZON. LANDFALL IS EXPECTED TO OCCUR RIGHT TAU 12 NEAR BALER. AFTER
25W EMERGES IN THE SOUTH CHINA SEA, RIDGING THAT EXTENDS WESTWARD
OVER TO HONG KONG WILL BECOME THE PRIMARY STEERING MECHANISM THAT
WILL DRIVE THE SYSTEM FURTHER NORTHWESTWARD THOUGH TAU 36. AROUND
TAU 36, A STRONG COLD SURGE FLOWING SOUTHWESTWARD NEAR TAIWAN WILL
PREVENT THE VORTEX FROM GAINING LATITUDE. A WESTWARD TRACK IS
FORECAST TO PERSIST THROUGH TAU 72. AT TAU 72, 25W WILL TURN MORE
SOUTHWESTWARD AS IT FOLLOWS THE LOW-LEVEL STEERING PATTERN AS IT
DISSIPATES. REGARDING INTENSITY, 25W IS FORECAST TO SLIGHTLY
DEGRADE, BUT STILL MAKE LANDFALL AT 100-110 KTS NEAR TAU 12.
TERRAIN INTERACTION OVER LUZON WILL RAPIDLY WEAKEN THE SYSTEM AND
BORDERLINE TYPHOON INTENSITY IS EXPECTED AS IT ENTERS THE SOUTH
CHINA SEA. INCREASING VERTICAL WIND SHEAR ALONG WITH THE COLD DRY
AIR BROUGHT IN FROM THE COLD SURGE WILL INHIBIT ANY CHANCES FOR
INTENSIFICATION AS THE SYSTEM TRACKS WESTWARD. NEAR TAU 72, THE
ENVIRONMENT QUICKLY WORSENS DUE TO SHEAR INCREASING TO AROUND 35
KTS AND DRY AIR ENTRAINING INTO THE CORE. AS A RESULT, DISSIPATION
SOUTH OF HAINAN IS FORECAST NEAR TAU 96. 

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT
THROUGH TAU 48. A 14 NM CROSS-TRACK SPREAD AT THE TIME OF LANDFALL
OPENS TO AROUND 100 KTS AT TAU 48. AFTER TAU 48, MODELS BEGIN TO
DIVERGE DUE TO DIFFERENCES IN THE TIMING OF DISSIPATION AND THE
SHARPNESS OF THE SOUTHWESTWARD TURN. THE JTWC TRACK FORECAST IS
PLACED CLOSE TO CONSENSUS THROUGH THE ENTIRE FORECAST PERIOD WITH
HIGH CONFIDENCE THROUGH TAU 48 AND LOW CONFIDENCE THEREAFTER.
INTENSITY GUIDANCE IS IN MODERATE AGREEMENT WITH AN EVEN SPREAD OF
ABOUT 15-20 KTS THROUGHOUT THE FORECAST. THE JTWC INTENSITY
FORECAST IS PLACED SLIGHTLY HIGHER THAN CONSENSUS THROUGH TAU 48
AND THEN SLIGHTLY LOWER THEREAFTER WITH OVERALL MEDIUM CONFIDENCE.

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