WDIO31 PGTW 132100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 02A (BIPARJOY)   
WARNING NR 031//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.6N 66.7E
   INITIAL INTENSITY: 80 KTS
   GEOGRAPHIC REFERENCE: 193 NM SOUTH OF KARACHI, PAKISTAN
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 03 KTS
   SIGNIFICANT WAVE HEIGHT: 34 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL CYCLONE (TC) 02A HAS REMAINED SURPRISINGLY RESILIENT AND
CONTINUES TO FIGHT A LOSING BATTLE WITH THE STRONG VWS. DESPITE
BRIEF BURSTS OF EXPANDING UPSHEAR OUTFLOW AND IMPROVED CORE
STRUCTURE, THE SYSTEM IS GRADUALLY WEAKENING WITH ERODING DEEP
CONVECTIVE BANDING OVER THE NORTHERN SEMICIRCLE. ANIMATED ENHANCED 
INFRARED (EIR) SATELLITE IMAGERY DEPICTS RAPIDLY PULSING CORE 
CONVECTION WITH A WEAK, SHORT-LIVED SMALL EYE EVIDENT AROUND 131600Z 
THEN A RAPIDLY DETERIORATING CORE THEREAFTER. EIR CONTINUES TO SHOW 
THE BULK OF THE DEEP CONVECTION SHEARED OVER THE SOUTHERN SEMICIRCLE. 
ENVIRONMENTAL CONDITIONS HAVE DEGRADED WITH STRONG (30-35 KNOT) 
NORTHEASTERLY VERTICAL WIND SHEAR (VWS) OFFSET SOMEWHAT BY MODERATE 
WESTWARD OUTFLOW AND VERY WARM SST VALUES. DUE TO THE STRONG VWS, 
DETERMINATION OF THE INITIAL POSITION HAS REMAINED CHALLENGING WITH 
THE UPPER-LEVEL CIRCULATION CENTER TILTED ABOUT 25NM TO THE SOUTHWEST 
OF THE LOW-LEVEL CIRCULATION CENTER (LLCC). THE INITIAL POSITION, 
WHICH IS BASED ON THE LLCC, IS PLACED WITH MEDIUM CONFIDENCE BASED ON 
A PARTIAL 131704 ASCAT-B IMAGE AS WELL AS A 131613Z MHS 89GHZ 
MICROWAVE IMAGE. THE INITIAL INTENSITY OF 80 KTS IS ASSESSED WITH 
MEDIUM CONFIDENCE BASED ON THE PGTW AND KNES DATA-T ESTIMATES AS WELL 
AS THE 131800Z ADT AND AIDT ESTIMATES NEAR 75 KNOTS. AS A SIDE NOTE, A 
131330Z RCM-1 SAR IMAGE INDICATED MAXIMUM WINDS OF 96 KNOTS OVER THE 
SOUTHEAST QUADRANT BUT WAS DISCOUNTED AS TOO HIGH BASED ON THE OVERALL 
WEAKENED CONVECTIVE STRUCTURE. 

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   KNES: T4.5 - 77 KTS
   CIMSS SATCON: 74 KTS AT 131527Z
   CIMSS ADT: 75 KTS AT 131800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 25-30 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: MODERATE WESTWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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: TC 02A IS FORECAST TO TRACK SLOWLY POLEWARD ALONG 
THE WESTERN PERIPHERY OF A NARROW, WEAK STR POSITIONED TO THE EAST 
WHILE STEADILY WEAKENING DUE TO PERSISTENT STRONG VWS. THE SYSTEM WILL 
GRADUALLY RECURVE NORTHEASTWARD AND APPROACH THE INDIA-PAKISTAN BORDER 
AREA WITH MORE SIGNIFICANT WEAKENING AFTER TAU 24 DUE TO INCREASED 
FRICTIONAL EFFECTS. AFTER TAU 36 WHEN THE SYSTEM MAKES LANDFALL, TC 
02A WILL RAPIDLY WEAKEN AND IS EXPECTED TO DISSIPATE BY TAU 72 OVER 
NORTHWEST INDIA.

MODEL DISCUSSION: WITH THE EXCEPTION OF NAVGEM, WHICH REMAINS THE
SOLE OUTLIER WITH A NORTH-NORTHEASTWARD TRACK, NUMERICAL MODEL
GUIDANCE IS IN GOOD AGREEMENT WITH A 40NM CROSS-TRACK SPREAD AT
LANDFALL (TAU 36). DUE TO UNCERTAINTY IN THE INITIAL POSITION AND
INCREASING CROSS-TRACK MODEL SPREAD AFTER TAU 36, OVERALL CONFIDENCE 
IN THE JTWC FORECAST TRACK IS MEDIUM. IN GENERAL, THE 131200Z ECMWF
AND GFS ENSEMBLES INDICATE A SIMILAR SPREAD OF SOLUTIONS AND REVEAL
A TIGHT GROUPING OF SOLUTIONS NEAR THE INDIA-PAKISTAN BORDER REGION.

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