WDIO31 PGTW 091500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 02A (BIPARJOY)   
WARNING NR 014//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.5N 67.3E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 558 NM SOUTH OF KARACHI, PAKISTAN
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A STEADILY 
WEAKENING CONVECTIVE CORE WITH A CLUSTER OF FLARING DEEP CONVECTION 
OBSCURING THE LOW-LEVEL CIRCULATION (LLC). EIR ALSO SHOWS A SECOND 
CLUSTER OF DEEP CONVECTION SEPARATED FROM THE CORE CONVECTION AND 
DISPLACED OVER THE WESTERN PERIPHERY OF THE SYSTEM. A 091146Z SSMIS 
91GHZ MICROWAVE IMAGE REVEALS DISORGANIZED CORE CONVECTION SHEARED 
WESTWARD OF A PARTIALLY-EXPOSED LLC WITH A CURVED CONVECTIVE BAND 
DISCONNECTED TO THE WEST. THE INITIAL POSITION IS PLACED WITH MEDIUM 
CONFIDENCE BASED ON THE SSMIS IMAGE. UPPER-LEVEL ANALYSIS CONTINUES TO 
INDICATE MODERATE TO HIGH EASTERLY VERTICAL WIND SHEAR (VWS) OFFSET 
SOMEWHAT BY BROAD DIFFLUENCE ALOFT. THE INITIAL INTENSITY OF 60 KTS IS 
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE PGTW DATA-T ESTIMATE OF 
T3.5 (55 KNOTS) AND AN AIDT OBJECTIVE ESTIMATE OF 62 KNOTS. DVORAK 
CURRENT INTENSITY ESTIMATES FROM ALL THREE AGENCIES ARE SLIGHTLY 
HIGHER AT 65 KNOTS.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) POSITIONED TO
THE EAST OVER WESTERN INDIA 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   KNES: T4.0 - 65 KTS
   DEMS: T4.0 - 65 KTS
   CIMSS SATCON: 68 KTS AT 090855Z
   CIMSS ADT: 59 KTS AT 091200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 20-25 KTS
   SST: 31-32 CELSIUS
   OUTFLOW: MODERATE WESTWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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: TROPICAL CYCLONE (TC) 02A IS STRUGGLING TO
CONSOLIDATE DUE TO THE PERSISTENT MODERATE TO HIGH EASTERLY VWS.
MODERATE WESTWARD OUTFLOW AND VERY WARM SEA SURFACE TEMPERATURES
HAVE HELPED MAINTAIN THE INCREASINGLY DISORGANIZED, UNIMPRESSIVE
CORE CONVECTION. GLOBAL MODELS HAVE BEGUN TO BACK OFF ON THE
DECREASING VWS SCENARIO AND NOW INDICATE PERSISTENT MODERATE TO
HIGH VWS, THEREFORE, THE PEAK INTENSITY HAS BEEN DECREASED TO 80
KNOTS AT TAU 36 AND WILL LIKELY BE LOWERED FURTHER. TC 02A IS
MEANDERING POLEWARD SLOWLY AND WILL CONTINUE TRACKING NORTHWARD TO
NORTH-NORTHEASTWARD THROUGH TAU 72. AFTER TAU 36, VWS IS FORECAST
TO INCREASE SLIGHTLY WITH UPPER-LEVEL EASTERLIES STRENGTHENING
SOUTH OF A BUILDING RIDGE TO THE NORTH. THIS IS EXPECTED TO PRODUCE
A STEADY WEAKENING TREND THROUGH TAU 120 AS THE SYSTEM CONTINUES TO
SLOWLY TRACK NORTH-NORTHWESTWARD INTO THE NORTHERN ARABIAN SEA.  

MODEL DISCUSSION: IN GENERAL, DETERMINISTIC GUIDANCE HAS COME INTO
BETTER AGREEMENT WITH GFS AND NAVGEM, IN PARTICULAR, ALIGNED CLOSER
TO THE ECMWF AND ECMWF ENSEMBLE MEAN SOLUTIONS. HOWEVER, THERE IS
STILL A 170NM CROSS-TRACK SPREAD IN SOLUTIONS AT TAU 72 AND A LARGE
385NM CROSS-TRACK SPREAD IN SOLUTIONS AT TAU 120 REFLECTING
INCREASING UNCERTAINTY (LOW CONFIDENCE) IN THE EXTENDED JTWC
FORECAST TRACK. THE 090600Z ECMWF AND GFS ENSEMBLES ARE ALSO BETTER
ALIGNED BUT ALSO REFLECT INCREASING UNCERTAINTY IN THE TRACK
FORECAST AFTER TAU 72. THERE IS ALSO MEDIUM CONFIDENCE IN THE JTWC
INTENSITY FORECAST THROUGH TAU 72 WITH A LARGE SPREAD IN RELIABLE
INTENSITY GUIDANCE. SEVERAL MODELS HAVE INDICATED AND CONTINUE TO 
INDICATE SOME POTENTIAL FOR A SHORT PERIOD OF RAPID INTENSIFICATION 
WITHIN THE NEXT 36 HOURS. THE 090600Z COAMPS-TC ENSEMBLE INDICATES 
INCREASING PROBABILITIES OF RAPID INTENSIFICATION FROM 80 TO 90 
PERCENT DURING THE NEXT 36 HOURS.   

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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