WDPN32 PGTW 130300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 25W (MAN-YI) WARNING NR 
017//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.6N 143.4E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 85 NM SOUTHWEST OF NAVSTA GUAM
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 16 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
STORM 25W (MAN-YI) WITH A PARTIALLY EXPOSED LOW-LEVEL CIRCULATION
CENTER (LLCC) AND SCATTERED CONVECTION OVER THE SOUTHEASTERN
QUADRANT. ENVIRONMENTAL ANALYSIS INDICATES THAT 25W IS IN A
MARGINALLY FAVORABLE ENVIRONMENT CHARACTERIZED BY WEAK RADIAL
OUTFLOW ALOFT, LOW (10-15 KTS) VERTICAL WIND SHEAR, DRY AIR TO THE
NORTHWEST OF THE SYSTEM, AND WARM (29-30 C) SEA SURFACE
TEMPERATURES. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE
BASED ON THE PARTIALLY EXPOSED LLCC IN THE ANIMATED MSI. THE
INITIAL INTENSITY OF 45 KTS IS ASSESSED WITH LOW CONFIDENCE
BASED ON THE UPPER END OF THE AGENCY DVORAK AND OBJECTIVE INTENSITY
ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 43 KTS AT 130000Z
   CIMSS AIDT: 37 KTS AT 130000Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK RADIAL
   OTHER FACTORS: DRY AIR TO THE NORTHWEST OF THE LLCC.

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: TRACK AFTER TAU 96 HAS BEEN BROUGHT
SOUTHWARD WHEN COMPARED TO THE PREVIOUS FORECAST.

FORECAST DISCUSSION: 25W IS FORECAST TO TRACK GENERALLY WESTWARD
THROUGH TAU 48 ALONG THE SOUTHERN PERIPHERY OF THE STR TO THE
NORTH. NEAR TAU 72, THE SYSTEM IS FORECAST TO BEGIN TRACKING
NORTHWESTWARD AS IT ROUNDS THE SOUTHWESTERN PERIPHERY OF THE STR
AND HEAD TOWARD LUZON. REGARDING INTENSITY, 25W IS FORECAST TO
STEADILY INTENSIFY TO AROUND 60 KTS AT TAU 24. AFTERWARDS, THE
SYSTEM IS FORECAST TO BEGIN A RAPID INTENSIFICATION
PHASE THROUGH TAU 48 DUE TO THE HIGHLY CONDUCIVE ENVIRONMENT. A
PEAK INTENSITY OF 115 KTS IS PLACED NEAR TAU 72. AFTER TAU 72, THE
SYSTEM IS EXPECTED TO BEGIN INTERACTING WITH THE COOLER WATERS LEFT
BEHIND FROM THE UPWELLING OF 26W AND 27W WHICH WILL INITIATE A
SLIGHT WEAKENING TREND BEFORE LANDFALL. TERRAIN INTERACTION WILL
THEN RAPIDLY WEAKEN THE SYSTEM AS IT TRACKS OVER LUZON NEAR THE END
OF THE FORECAST PERIOD.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT
REGARDING THE TRACK OF 25W THROUGH TAU 72. AFTER TAU 72, THE MODELS
BEGIN TO SPREAD CONSIDERABLY. GALWEM AND UKMET MAKE UP THE
SOUTHERNMOST TRACKERS WITH LANDFALL IN THE CENTRAL PHILIPPINES
WHILE GFS IS THE NORTHERNMOST TRACKER WITH A SKIRT ALONG THE
NORTHEASTERN COAST OF LUZON. THE JTWC TRACK FORECAST IS PLACED
CLOSE TO CONSENSUS THROUGH TAU 72 AND CLOSER TO THE AVERAGE OF
ECMWF, GFS, AND THEIR ENSEMBLE MEANS THROUGH THE REMAINDER OF THE
FORECAST. INTENSITY GUIDANCE HAS SHIFTED SLIGHTLY WITH LESS RAPID
INTENSIFICATION (RI) INDICATIONS. MESOSCALE MODELS (HWRF, HAFS-A,
AND COAMPS-TC) STILL SUGGEST VERY QUICK INTENSIFICATION,
PARTICULARLY FROM TAU 24 TO 60. THE JTWC INTENSITY FORECAST
REFLECTS THAT. IN THE EXTENDED FORECAST, THE VARYING AMOUNT OF LAND
INTERACTION BETWEEN MODELS CAUSES A SIGNIFICANT SPREAD IN
INTENSITIES AFTER TAU 96. 

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