WDPN32 PGTW 181500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 25W (MAN-YI) WARNING NR 
039//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.6N 115.9E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 242 NM SOUTH-SOUTHEAST OF HONG KONG
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 26 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY INDICATES THAT
TROPICAL STORM (TS) 25W (MAN-YI) HAS HAD A LITTLE BIT OF A
COMEBACK. DEEP CONVECTION THAT FORMED AROUND 0600Z WAS ABLE TO WRAP
UPSHEAR AND THE LOCALIZED OUTFLOW FROM THE CONVECTIVE ACTIVITY
PUSHED BACK AGAINST THE SOUTHWESTERLY SHEAR VECTOR, AS EVIDENCED BY
THE TRANSVERSE BANDING TO THE SOUTH SEEN IN THE WATER VAPOR
IMAGERY. AT ANALYSIS TIME, THE CONVECTIVE APPEARS TO BE COLLAPSING
AND THE SYSTEM WILL RAPIDLY SUCCUMB TO THE PERSISTENT SHEAR. THE
LACK OF MICROWAVE PASSES OVER THE SIX HOURS PRECLUDES A HIGH
CONFIDENCE ASSESSMENT OF THE INITIAL POSITION DUE TO THE
OBSCURATION OF THE LOW LEVEL CIRCULATION CENTER (LLCC), AND THE
POSITION IS DETERMINED BASED SOLELY OFF THE AVAILABLE AGENCY FIX
POSITIONS. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM
CONFIDENCE, CONSISTENT WITH THE CIMSS ADT, AIDT AND SATCON, AND
HEDGED LOWER THAN THE AGENCY CURRENT INTENSITY ESTIMATES, WHICH ARE
BEING HELD HIGHER DUE TO CONSTRAINTS. THE ENVIRONMENT, WHILE HAVING
TEMPORARILY IMPROVED, IS IN THE AGGREGATE UNFAVORABLE, WITH
MODERATE AND INCREASING SOUTHWESTERLY SHEAR, COOL SSTS, AND DRY AIR
STARTING TO IMPINGE INTO THE WESTERN AND SOUTHERN PORTIONS OF THE
CIRCULATION.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A EXTENSION OF A
DEEP-LAYER SUBTROPICAL RIDGE THAT EXTENDS FROM NORTHERN VIETNAM,
THROUGH TAIWAN AND INTO THE PHILIPPINE SEA. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   RJTD: T4.5 - 77 KTS
   RCTP: T3.5 - 55 KTS
   KNES: T4.0 - 65 KTS
   DEMS: T4.0 - 65 KTS
   CIMSS SATCON: 56 KTS AT 181101Z
   CIMSS ADT: 61 KTS AT 181130Z
   CIMSS AIDT: 58 KTS AT 181130Z
   CIMSS D-PRINT: 30 KTS AT 181200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 10-15 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: MODERATE POLEWARD
   OTHER FACTORS: DRY LOW- TO MID-LEVEL AIR ON THE WESTERN SIDE OF
THE CIRCULATION. 

ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   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 SYSTEM IS CURRENTLY TRACKING JUST A FEW
DEGREES NORTH OF DUE WEST, ALONG THE SOUTHERN SIDE OF AN EXTENSION
OF THE STR TO THE NORTH. OVER THE NEXT 12 TO 24 HOURS, THE VORTEX
WILL DECOUPLE DUE TO THE PERSISTENT SHEAR, WHICH WILL FINALLY
OVERWHELM THE SYSTEM. ONCE THIS OCCURS, THE VERY DRY MID-LEVEL AIR
WILL RAPIDLY MOVE IN FROM THE SOUTHWEST, AND SMOTHER ANY REMAINING
HOPES FOR CONVECTIVE ACTIVITY. THE NAKED VORTEX WILL THEN TURN MORE
SOUTHWESTWARD, SKIRTING THE SOUTHERN COAST OF HAINAN BY TAU 36,
THEN TRACK TOWARDS THE COAST OF VIETNAM. IT WILL NOT REACH THE
COASTLINE HOWEVER, AS THE SYSTEM WILL RAPIDLY WEAKEN AFTER TAU 12,
DISSIPATING AS A TROPICAL CYCLONE OVER WATER TO THE NORTHEAST OF
HUE, VIETNAM BY TAU 48. 

MODEL DISCUSSION: TRACK GUIDANCE STRUGGLES AFTER TAU 12, WITH THE
VARIOUS CONSENSUS MODELS DIFFERING WILDLY ON WHEN THEY DISSIPATE
AND LOSE THE VORTEX. SOME GIVE UP THE GHOST AS EARLY AS TAU 24,
WHILE OTHERS HOLD ONTO IT FOR UP TO 72 HOURS. AT THE SAME TIME, THE
MODELS DIFFER SIGNIFICANTLY AS TO WHICH DIRECTION THE REMNANT
VORTEX WILL SPIN OFF TOWARDS, WITH SOME MODELS TAKING IT NORTH INTO
HAINAN, SOME SHOOTING SOUTH INTO SOUTHERN VIETNAM AND STILL OTHERS
LOOPING BACK TO THE EAST. THE JTWC FORECAST REMAINS A PARAGON OF
CONSISTENCY, STICKING CLOSE TO THE MULTI-MODEL CONSENSUS, THOUGH
CONFIDENCE IS ON THE LOWER SIDE DUE TO THE WIDE DISCREPANCIES IN
THE MODEL. INTENSITY GUIDANCE HOWEVER, IS IN GOOD AGREEMENT THAT
THE SYSTEM WILL STEADILY AND RAPIDLY WEAKEN THROUGH THE FORECAST
PERIOD. 

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