WDPN32 PGTW 172100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 25W (MAN-YI) WARNING NR 036//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.7N 119.4E
   INITIAL INTENSITY: 75 KTS
   GEOGRAPHIC REFERENCE: 208 NM NORTH-NORTHWEST OF MANILA,
PHILIPPINES
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 17 KTS
   SIGNIFICANT WAVE HEIGHT: 24 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TYPHOON
25W (MAN-YI) WITH A PARTIALLY EXPOSED LOW-LEVEL CIRCULATION CENTER
(LLCC) AND FRAGMENTED CONVECTIVE BANDING ALONG THE SOUTHERN AND
EASTERN PERIPHERIES OF THE CIRCULATION. THE WESTERN PORTION OF THE
SYSTEM IS VOID OF CONVECTION, BUT THE LLCC SEEMS TO STILL BE
STRONG. ENVIRONMENTAL ANALYSIS INDICATES THAT 25W IS IN A
MARGINALLY FAVORABLE ENVIRONMENT CHARACTERIZED BY MODERATE RADIAL
OUTFLOW ALOFT, LOW TO MODERATE (15-20 KTS) VERTICAL WIND SHEAR, AND
WARM (28-29 C) SEA SURFACE TEMPERATURES. THE INITIAL POSITION IS
PLACED WITH MEDIUM CONFIDENCE BASED ON THE PARTIALLY EXPOSED LLCC
IN THE ANIMATED EIR IMAGERY. THE INITIAL INTENSITY OF 75 KTS IS
ASSESSED WITH LOW CONFIDENCE DUE TO THE SHORT TIME BACK OVER
WATER. AGENCY DVORAK FINAL T NUMBERS AND OBJECTIVE INTENSITY
ESTIMATES SUGGEST AN INTENSITY OF AROUND 70-75 KTS THOUGH.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF AN EXTENSION OF A
SUBTROPICAL RIDGE (STR) TO THE EAST THAT EXTENDS WESTWARD, NORTH OF
THE SYSTEM.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   RJTD: T5.5 - 102 KTS
   RCTP: T5.0 - 90 KTS
   KNES: T6.0 - 115 KTS
   DEMS: T4.5 - 77 KTS
   CIMSS SATCON: 77 KTS AT 171700Z
   CIMSS ADT: 94 KTS AT 171800Z
   CIMSS AIDT:71 KTS AT 171800Z
   CIMSS DMINT: 83 KTS AT 171800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE RADIAL
   OTHER FACTORS: PRESSURE FROM THE COLD SURGE FLOWING
SOUTHWESTWARD INTO THE SOUTH CHINA SEA.

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: LOW
   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 TRACK WEST-NORTHWESTWARD,
ALONG THE SOUTHERN PERIPHERY OF THE RIDGING TO THE NORTH THROUGH TAU
24. THE COLD SURGE FLOWING INTO THE SOUTH CHINA SEA ALONG WITH THE
MENTIONED RIDGING WILL INHIBIT 25W FROM GAINING MUCH LATITUDE. FROM
TAU 24 TO 48, 25W IS FORECAST TO TRACK GENERALLY WESTWARD TOWARD
HAINAN. AFTER TAU 48, THE WEAKENED VORTEX IS FORECAST TO TRACK
ALONG THE LOW-LEVEL STEERING PATTERN AS IT DISSIPATES NEAR TAU 72.
REGARDING INTENSITY, 25W IS FORECAST TO WEAKEN STEADILY THROUGH TAU
48 TO AROUND 35 KTS IN RESPONSE TO A MARGINAL ENVIRONMENT (25-30
KTS OF SHEAR AND COOLER SEA SURFACE TEMPERATURES). ADDITIONALLY,
THE COLD SURGE WILL BRING IN COLD, DRY AIR WHICH WILL AID IN
WEAKENING THE SYSTEM. AFTER TAU 48, THE ENVIRONMENT QUICKLY WORSENS
WITH AROUND 35 KTS OF SHEAR AND SIGNIFICANT DRY AIR ENTRAINMENT. AS
A RESULT, 25W IS FORECAST TO DISSIPATE SOUTH OF HAINAN AROUND TAU
72.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT
REGARDING THE TRACK OF 25W THROUGH TAU 48 WITH A 110 NM CROSS-TRACK
SPREAD AT THAT TIME. AFTER TAU 48 THE MODELS BEGIN TO DIVERGE AS
THE VORTEX WEAKENS. GALWEM IS A PRIMARY OUTLIER, TRACKING THE
VORTEX INTO SOUTHERN VIETNAM AT TAU 72. THE JTWC TRACK FORECAST IS
PLACED CLOSE TO CONSENSUS, DISREGARDING GALWEM, WITH OVERALL MEDIUM
CONFIDENCE. INTENSITY GUIDANCE IS IN MODERATE AGREEMENT WITH ALL
MODELS SUGGESTING WEAKENING THROUGH THE FORECAST PERIOD. THE JTWC
INTENSITY FORECAST IS PLACED CLOSE TO CONSENSUS THROUGHOUT THE
FORECAST WITH MEDIUM CONFIDENCE.

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