WDIO31 PGTW 080300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 02A (BIPARJOY) WARNING 
NR 008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.7N 66.2E
   INITIAL INTENSITY: 80 KTS
   GEOGRAPHIC REFERENCE: 584 NM SOUTHEAST OF MASIRAH ISLAND
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 03 KTS
   SIGNIFICANT WAVE HEIGHT: 27 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
CYCLONE BEING SHEARED BY MODERATE EASTERLY VERTICAL WIND SHEAR
(VWS), WITH A RAGGED MASS OF DEEP CONVECTION DISPLACED LARGELY
SOUTHWEST OF THE LOW-LEVEL CIRCULATION CENTER (LLCC). THE INITIAL
POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON A COMBINATION OF
AGENCY POSITION FIXES. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM 
CONFIDENCE BASED ON A COMBINATION OF OBJECTIVE AND SUBJECTIVE 
INTENSITY ESTIMATES. THE SYSTEM CONTINUES TO TRACK TOWARD THE 
NORTHWEST ON THE WESTERN PERIPHERY OF AN EXTENSION OF THE SUBTROPICAL 
RIDGE (STR) OVER INDIA. ENVIRONMENTAL ANALYSIS IS ASSESSED AS 
MARGINAL, WITH GOOD MODERATE POLEWARD AND EQUATORWARD OUTFLOW ALOFT, 
WARM SEA SURFACE TEMPERATURES (SSTS) RANGING (29-30C) OFFSET BY 
MODERATE EASTERLY VERTICAL WIND SHEAR (VWS) WHICH IS TILTING THE 
SYSTEM WESTWARD.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: AN EXTENSION OF THE SUBTROPICAL RIDGE
(STR) OVER INDIA.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   KNES: T4.0 - 65 KTS
   DEMS: T4.0 - 65 KTS
   CIMSS SATCON: 58 KTS AT 072116Z
   CIMSS ADT: 59 KTS AT 080000Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

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 (BIPARJOY) IS EXPECTED TO CONTINUE
TRACKING NORTH-NORTHWESTWARD AS A SHORTWAVE TROUGH PASSES TO THE
NORTH WHILE A RIDGE BUILDS OVER INDIA. BY TAU 36, THE SYSTEM WILL 
PICK UP SPEED AS THE RIDGE OVER INDIA IS EXPECTED TO BECOME THE 
DOMINANT STEERING FEATURE. AFTER TAU 48, 02A WITH TRACK NORTHWESTWARD 
THROUGH THE REMAINDER OF THE FORECAST, AS THE RIDGE STRENGTHENS AND 
ELONGATES TO A NORTHWEST-SOUTHEAST ORIENTATION. TROPICAL CYCLONE 02A 
CONTINUES TO BATTLE EASTERLY VWS. WHICH EXPLAINS WHY 02A HAS STRUGGLED 
TO MAKE SIGNIFICANT GAINS IN INTENSITY OVER THE PAST 12 HOURS. 
HOWEVER, 02A IS FORECAST TO INTENSIFY TO A PEAK OF 95-100 KNOTS OVER
THE NEXT 24-36 HOURS. HOWEVER, AFTER TAU 36, THE SYSTEM IS
EXPECTED TO STEADILY WEAKEN DUE TO MULTIPLE NEGATIVE FACTORS, SUCH AS
INCREASING VWS, AND DECREASED OUTFLOW ALOFT. AFTER TAU 72, FURTHER
WEAKENING IS EXPECTED AS A RESULT OF DRY AIR ENTRAINMENT.


MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE CONTINUES TO SHOW
A BIFURCATION, BETWEEN THE UKMET, GALWEM, AND ECMWF TRACKING THE
SYSTEM ON THE RIGHT OF THE GUIDANCE ENVELOPE. WHILE THE GFS,
NAVGEM, AND THE GFS ENSEMBLE MEAN MAKE UP WESTERN PERIPHERY OF THE
GUIDANCE ENVELOPE TURNING TOWARD THE ARABIAN PENINSULA BY THE LATER
TAUS. ADDITIONALLY, ENSEMBLE MEMBERS FOR BOTH GFS AND ECMWF
CONTINUES TO SHOW A HIGH DEGREE OF UNCERTAINTY WITH LARGE SPREAD
ESPECIALLY IN THE LATER TAUS AS WELL. THEREFORE, THE JTWC TRACK
FORECAST IS PLACED WITH LOW CONFIDENCE BASED ON THE UNCERTAINTY IN
THE TRACK GUIDANCE. THE INTENSITY GUIDANCE IS MIXED, WITH RAPID
INTENSIFICATION (RI) GUIDANCE BEING TRIGGERED ALONG WITH THE HWRF
SHOWING AN INTENSIFICATION PHASE UP TO 110 KNOTS. WHILE GFS
CONTINUES TO REPRESENT THE LOW END OF THE INTENSITY GUIDANCE
ENVELOPE, WITH A PEAK OF 90 KNOTS. THE JTWC INTENSITY FORECAST IS
PLACED WITH LOW CONFIDENCE AND CLOSE TO THE MULTI-MODEL CONSENSUS.



FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: LOW
   INTENSITY 72-120 HR: LOW//
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