WDPS32 PGTW 080300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 11P (OSAI)
WARNING NR 006//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.6S 164.7W
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 309 NM EAST-NORTHEAST OF NIUE
   MOVEMENT PAST 6 HOURS: SOUTHEASTWARD AT 03 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
CYCLONE (TC) 11P (OSAI) CONTINUING TO BE HEAVILY INFLUENCED BY
STRONG (25-30KTS) VERTICAL WIND SHEAR (VWS) OVER THE PAST SIX
HOURS, AS REMAINING CONVECTIVE STRUCTURES BECOME COMPLETELY
DISLOCATED TO THE EAST AND SOUTHEAST OF THE LOW-LEVEL CIRCULATION
CENTER (LLCC) IN ANIMATED GOES-18 VISIBLE SATELLITE IMAGERY. SEA 
SURFACE TEMPERATURES REMAIN VERY HIGH, BETWEEN 28C-29C,
WHILE THE UPPER-LEVEL DIVERGENCE MECHANISM BECOMES INCREASINGLY 
DECOUPLED FROM THE PARTIALLY EXPOSED LLCC. THE INITIAL POSITION IS 
PLACED WITH HIGH CONFIDENCE BASED ON THE AFOREMENTIONED PARTIALLY 
EXPOSED CIRCULATION CENTER EVIDENT ON THE ANIMATED GOES-18 VISIBLE 
LOOP. THE INITIAL INTENSITY OF 45 KTS IS ASSESSED WITH MEDIUM 
CONFIDENCE BASED ON SUBJECTIVE INTENSITY ESTIMATES AND CIMSS 
INTENSITY
ESTIMATES.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: NER TO THE NORTHWEST AND STR TO THE
SOUTHWEST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   PHFO: T2.5 - 35 KTS
   CIMSS SATCON: 48 KTS AT 2240Z
   CIMSS ADT: 49 KTS AT 072340Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 25-30 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: WEAK POLEWARD

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: TC 11P IS FORECAST TO TRACK GENERALLY
SOUTH-SOUTHEASTWARD THROUGH TAU 36, FOLLOWING THE WEAKENING
STEERING INFLUENCE OF THE SUBTROPICAL RIDGE (STR) TO THE SOUTHWEST.
ALTHOUGH THE ENHANCED VWS IS EXPECTED TO BE STRONGEST AT TAU 6 AND
DECREASE STEADILY INTO THE REMAINDER OF THE FORECAST PERIOD, 
RELATIVELY STRONG TO MODERATE (GREATER THAN 20 KTS) VWS WILL FURTHER 
DISSIPATE TC 11P THROUGH TAU 36. AS ENVIRONMENTAL PARAMETERS REMAIN 
MARGINALLY UNFAVORABLE, THE TROPICAL CYCLONE IS EXPECTED TO GRADUALLY 
DECREASE IN INTENSITY INTO THE REMAINDER OF THE FORECAST PERIOD DUE 
TO THE AFOREMENTIONED STRONG TO MODERATE VWS WHILE AN EXTENSION OF A
LONGWAVE TROUGH CARRIES TC 11P EASTWARD, UNDER THE WESTERLIES INTO
DISSIPATION. PREVIOUSLY MENTIONED MODEL MEMBERS OF THE JTWC
INTENSITY CONSENSUS SHOW A STEADY DECAY IN INTENSITY THROUGH TAU
36, WHILE COMPETING STEERING INFLUENCES PROGRESS THE TRACK
GENERALLY TO THE SOUTH, AND THEN EAST WITH THE WESTERLIES BY TAU 36.

MODEL DISCUSSION: GLOBAL NUMERICAL MODEL GUIDANCE IS IN GOOD 
AGREEMENT
THAT TC 11P WILL TRACK GENERALLY TO THE SOUTH-SOUTHEAST THROUGH TAU
12, AND THEN MEMBERS OF THE JTWC CONSENSUS DIVERGE SIGNIFICANTLY,
OFFERING SEVERAL SOUTHWARD SOLUTIONS BY TAU 36 AS STEERING
MECHANISMS COMPETE. MOST CONSENSUS MEMBERS PROGRESS TC 11P TO THE
EAST, AS THE STR BEGINS TO BUILD BACK INTO THE AREA AND A LONGWAVE
TROUGH CARRIES THE SYSTEM EASTWARD UNDER THE WESTERLIES. BETWEEN
TAU 24 AND TAU 36, THE MODEL GUIDANCE PROJECTS THE BEGINNING OF THE
EASTWARD TRACK, WHILE INTENSITY AIDS ARE IN BETTER AGREEMENT THAT
TC 11P WHILE STEADILY DECREASE TO 30 KTS BY TAU 36 WITH A SPREAD OF
10-15 KTS.  

FORECAST CONFIDENCE:
   TRACK 0 - 36 HR: LOW
   INTENSITY 0 - 36 HR: MEDIUM//
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