WDPN32 PGTW 130900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 25W (MAN-YI) WARNING NR 
018//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.3N 142.6E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 134 NM WEST-SOUTHWEST OF NAVSTA GUAM
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A
DISORGANIZED, WEAK AND PARTIALLY EXPOSED LOW LEVEL CIRCULATION
CENTER (LLCC), WITH MODERATE CONVECTIVE ACTIVITY CONFINED TO THE
EASTERN PORTION OF THE CIRCULATION. A 130329Z AMSR2 COLOR-ENHANCED
91GHZ MICROWAVE IMAGERY SHOWED LOW-LEVEL BANDS WRAPPING INTO AN
ILL-DEFINED AND IRREGULAR LLCC, AND DEEP CONVECTION DEVELOPING
ALONG A CONVERGENT ASYMPTOTE IN THE SOUTHEASTERN QUADRANT. THE
INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE
PARTIALLY EXPOSED LLCC AND EXTRAPOLATION OF THE MICROWAVE-DERIVED
CENTER. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE,
ON THE HIGHER END OF THE SUBJECTIVE AND OBJECTIVE INTENSITY
ESTIMATES OUTLINED ABOVE. THE ENVIRONMENT IS GENERALLY FAVORABLE,
BUT THE DISORGANIZED NATURE OF THE LOW-LEVEL VORTEX AND THE WEAK
OUTFLOW ALOFT ARE OFFSETTING THE OTHERWISE FAVORABLE CONDITIONS OF
LOW NORTHERLY SHEAR AND ZESTY SSTS.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SOUTHEASTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) TO THE NORTHWEST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 39 KTS AT 130530Z
   CIMSS AIDT: 34 KTS AT 130530Z
   CIMSS D-MINT: 28 KTS AT 130331Z
   CIMSS D-PRINT: 27 KTS AT 130700Z

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

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: THE STR TO THE NORTH WILL BE THE PRIMARY
STEERING MECHANISM FOR THE DURATION OF THE FORECAST PERIOD. THE STR
IS CURRENTLY CENTERED TO THE NORTHWEST, TO THE SOUTH OF KYUSHU AND
IS EXPECTED TO REMAIN QUASI-STATIONARY FOR THE NEXT 24 HOURS. THUS,
TS 25W WILL TRACK WEST-SOUTHWESTWARD THROUGH TAU 24. BY TAU 36, THE
RIDGE BEGINS TO SLIDE EASTWARD, AND BY TAU 48 WILL BE POSITIONED TO
THE NORTHEAST OF TS 25W AND THE SYSTEM WILL BEGIN TRACKING TOWARDS
THE WEST-NORTHWEST AFTER THIS POINT. THE MAIN DETERMINANT IN THE
FORECAST TRACK AFTER TAU 48 IS HOW FAR THE RIDGE MOVES TO THE EAST
AND HOW DEEP A MID-LATITUDE TROF PASSING OVER KOREA AND JAPAN WILL
BE. IF THE RIDGE PUSHES FURTHER EAST AND THE TROF PENETRATES
FURTHER SOUTHWARD, THE TRACK OF TS 25W WILL BE MORE NORTHWESTWARD.
IF THE RIDGE DOES NOT GO AS FAR EASTWARD AND THE TROF IS SHALLOWER,
THEN THE TRACK WILL REMAIN MORE WEST-NORTHWESTWARD. THE CURRENT
FORECAST A MORE NORTHWESTWARD TRACK. LANDFALL IS EXPECTED AROUND
TAU 96 IN NORTHERN LUZON, FOLLOWED BY A QUICK TRANSIT ACROSS THE
ISLAND AND INTO THE SOUTH CHINA SEA BY TAU 120. IN TERMS OF
INTENSITY, THE SYSTEM WILL SLOWLY INTENSIFY OVER THE NEXT 36 HOURS
AS THE VORTEX CONTINUES TO CONSOLIDATE UNDER FAVORABLE LOW SHEAR
CONDITIONS. RAPID INTENSIFICATION IS EXPECTED AFTER TAU 48 AS THE
SYSTEM MOVES OVER AN AREA OF EXTREMELY HIGH OHC (EXCEEDING 175 KJ
PER CM3). THE SYSTEM WILL LIKELY PEAK BETWEEN TAU 72 AND TAU 96,
WITH THE 115 KNOTS IN THE FORECAST BEING THE FLOOR OF THE POTENTIAL
INTENSITY. THE SYSTEM WILL LIKELY SLOW DOWN AS IT APPROACHES THE
SIERRA MADRE MOUNTAINS ON THE EAST COAST OF LUZON AND WEAKEN
SLIGHTLY AS IT STARTS TO FEEL THE IMPACT OF INCREASED FRICTION AND
OFFSHORE, DOWNSLOPE WINDS AS IT APPROACHES LANDFALL. AFTER CROSSING
LUZON, THE SYSTEM IS EXPECTED TO EMERGE INTO THE SOUTH CHINA SEA AS
A MINIMAL TYPHOON. 

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN MODERATE
AGREEMENT, THOUGH ALL OF THE CONSENSUS MEMBERS CONCUR ON THE
GENERAL TRACK SCENARIO. CROSS-TRACK SPREAD STEADILY INCREASES TO
100NM AT TAU 48 AND 200NM AT TAU 72, WITH THE GFS ON THE NORTHERN
EDGE OF THE ENVELOPE AND THE UKMET ENSEMBLE MEAN ON THE SOUTHERN
EDGE. A WEAK BIFURCATION BEGINS TO EMERGE AFTER TAU 72, WITH TWO
DISTINCT GROUPINGS OF MODELS TRACKERS DIVERGING FROM ONE ANOTHER.
THE SOUTHERN GROUP THE UKMET ENSEMBLE, THE EGRR, GALWEM, JGSM AND
ECMWF ON THE NORTHERN EDGE, TAKE THE SYSTEM ON A MORE WESTWARD
TRACK ROUGHLY CENTERED ON A TRACK PASSING VERY CLOSE TO MANILA BY
TAU 96. THE OTHER GROUP CONSISTING OF GFS, GEFS ENSEMBLE MEAN,
NAVGEM AND THE HAFS-A AND HWRF, TAKE THE SYSTEM ON A TRACK CENTERED
NEAR PALANAN, LUZON. THE GFS IS THE OUTLIER, KEEPING THE SYSTEM
OVER WATER OFF THE NORTHEAST TIP OF LUZON. THE JTWC FORECAST LIES
ON THE SOUTHERN EDGE OF THIS NORTHERN GROUP, JUST A BIT NORTH OF
THE 0000Z ECENS MEAN TRACK. CONFIDENCE IS HIGH THROUGH TAU 72,
DECREASING TO MEDIUM THEREAFTER. INTENSITY GUIDANCE IS IN GOOD
AGREEMENT THAT THE SYSTEM WILL STEADILY INTENSIFY FOR THE FIRST 24
TO 36 HOURS, FOLLOWED BY RAPID INTENSIFICATION (RI) THROUGH TAU 72.
THE HAFS-A AND CTCX PEAK THE SYSTEM AT 110-115 KNOTS. THE CTCX
ENSEMBLE INTENSITY PROBABILITIES INDICATE A 95 PERCENT PROBABILITY
OF RI BETWEEN TAU 48 AND TAU 72. THE JTWC IS ABOUT 5-10 KNOTS BELOW
THE CONSENSUS MEAN TO TAU 48, THEN TRACKS THE HWRF THROUGH THE
REMAINDER OF THE FORECAST. CONFIDENCE IS MEDIUM TO TAU 72 THEN LOW
THEREAFTER. 

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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