WDPN32 PGTW 120900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 25W (MAN-YI) WARNING NR 
014//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.1N 147.6E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 180 NM EAST-NORTHEAST OF NAVSTA GUAM
   MOVEMENT PAST 6 HOURS: WESTWARD AT 16 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
STORM (TS) 25W (MAN-YI) WITH A FULLY-EXPOSED LOW-LEVEL CIRCULATION
CENTER (LLCC) AND STRUGGLING TO INTENSIFY AS PERSISTENT AND EVIDENT
DRY AIR CONTINUES TO LEAVE THE CORE VOID OF ANY SUPPORTIVE
CONVECTION. VERTICAL WIND SHEAR (VWS) OF 15-20 KTS HAS ALSO
PERSISTED OVER THE LAST SIX HOURS, DISLOCATING AN AREA OF FLARING
CONVECTION TO THE SOUTHEAST QUADRANT. ANIMATED WATER VAPOR IMAGERY
HAS ALSO SHOWN WEAK TO MODERATE EQUATORWARD OUTFLOW, WITH A
SOUTHWARD EXTENDING CHANNEL OF CONTINUOUS CONVECTION. THE
ENVIRONMENT HAS BEEN CHARACTERIZED AS MARGINAL DUE TO AMPLE DRY AIR
BATTERING TS 25W FROM THE WEST AND WRAPPING CYCLONICALLY INTO
CENTER. WITH THAT BEING SAID, WELL-DEFINED LOW-LEVEL CLOUD LINES
CAN BE OBSERVED WRAPPING NEATLY INTO THE AFOREMENTIONED LLCC AS THE
CONVECTION REMAINS DISPLACED. THE INITIAL POSITION IS PLACED WITH
HIGH CONFIDENCE BASED ON THE FULLY-EXPOSED AND OBSERVABLE LLCC ON
ANIMATED MSI. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON THE SUBJECTIVE AGENCY ESTIMATES LISTED BELOW
AND CIMSS OBJECTIVE ESTIMATES RANGING BETWEEN 29 KTS AND 39 KTS.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) LOCATED TO THE
NORTH AND EXTENDING WESTWARD TOWARD TAIWAN. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   KNES: T2.5 - 35 KTS
   CIMSS ADT: 39 KTS AT 120540Z
   CIMSS AIDT: 37 KTS AT 120540Z
   CIMSS D-PRINT: 29 KTS AT 120500Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 15-20 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: TS 25W IS FORECASTED TO REMAIN ON A GENERALLY
WESTWARD TRACK THROUGH THE INITIAL 72 HOURS OF THE FORECAST PERIOD
ALONG THE SOUTHERN AND SOUTHWESTERN PERIPHERY OF THE SUBTROPICAL
RIDGE LOCATED DIRECTLY TO THE NORTH. FOLLOWING TAU 72, MAN-YI IS
EXPECTED TO BEGIN THE ANTICYCLONIC TRACK ALONG THE WESTERN
PERIPHERY OF THE AFOREMENTIONED STR, MOVING NORTHWESTWARD. AFTER
TAU 72, TROPICAL STORM 25W WILL CONTINUE ITS NORTHWESTWARD TRACK,
NEARING LUZON BY TAU 120 AS THE SYSTEM STARTS TO NEAR THE STR AXIS.
WITH REGARD TO FORECAST INTENSITY, THE STRUGGLING SYSTEM IS
EXPECTED TO STEADILY INTENSIFY TO 45 KTS IN CLOSE PROXIMITY TO GUAM
AND ROTA BY TAUS 12-18. AS TS 25W PASSES THROUGH THE MARIANAS, SLOW
INTENSIFICATION IS FORECASTED INTO 96 WHILE SEA SURFACE
TEMPERATURES REMAIN BETWEEN 29 C AND 30 C, DRY AIR DECREASES
SUBSTANTIALLY AFTTER TAU 36, REMOISTENING THE CORE, AND VWS
DECREASES TO BELOW 15 KTS. THROUGHOUT THIS PERIOD, TS 25W IS
FORECASTED TO INTENSIFY TO A MAXIMUM OF 100 KTS NEAR TAU 96 AS THE
ENVIRONMENT REMAINS CONDUCIVE FOR FURTHER DEVELOPMENT. AFTER TAU
96, SEA SURFACE TEMPERATURES BEGIN DECREASING TO LESS THAN 26 C
WHILE VWS INCREASES ABOVE 20 KTS FROM THE NORTHEAST, CREATING A
HOSTILE ENVIRONMENT AND INITIATING THE WEAKENING PHASE AS THE
SYSTEM NEARS THE LUZON STRAIT.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT
WITH A CROSS-TRACK SPREAD OF 85 NM BY TAU 48 WITH NAVGEM CONTINUING
TO REMAIN THE SINGLE OUTLIER DISPLACED TO THE NORTH OF THE JTWC
CONSENSUS MEMBERS. AFTER TAU 48, THE CROSS-TRACK BEGINS TO INCREASE
IMMENSELY, DIVERGING TO OVER 500 NM BY TAU 120. THE JTWC TRACK 
CONSENSUS ILLUSTRATES A WESTWARD TRACK INTO TAU 72, SHIFTING TO A 
NORTHWESTWARD TRACK AROUND THE PERIPHERY OF THE STR BY THE END OF THE 
FORECAST PERIOD, LENDING MEDIUM CONFIDENCE THROUGH TAU 72. SINCE THE 
TRACK SPREAD INCREASES GREATLY AFTER TAU 72, CONFIDENCE BETWEEN TAU 72 
AND 120 BECOMES LOW. THE JTWC INTENSITY FORECAST IS ALIGNED WITH THE 
CONSENSUS THROUGH THE INITIAL 36 HOURS OF THE FORECAST, AS THE 
ENVIRONMENT HAS REMAINED MARGINAL AT BEST. FOLLOWING TAU 36, THE JTWC 
FORECAST REMAINS JUST BELOW THAT OF THE CONSENSUS DUE TO A FEW 
EXCEEDINGLY HIGH SOLUTIONS OF 105 KTS TO 115 KTS. IN GENERAL, THE JTWC 
INTENSITY FORECAST IS PLACED WITH MEDIUM CONFIDENCE DURING THE INITIAL 
72 HOURS AND LOW BETWEEN TAU 72 AND TAU 120. 

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