WDIO31 PGTW 062100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 02A (BIPARJOY) 
WARNING NR 003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.3N 66.2E
   INITIAL INTENSITY: 70 KTS
   GEOGRAPHIC REFERENCE: 646 NM SOUTHEAST OF MASIRAH ISLAND
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 01 KTS
   SIGNIFICANT WAVE HEIGHT: 21 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A VERY
COMPACT CENTRAL DENSE OVERCAST (CDO), WITH A WARM SPOT INDICATIVE
OF A NASCENT EYE FEATURE BEGINNING TO EMERGE. A TIMELY 061831Z GMI
89GHZ IMAGE SHOWED A CLEAR MICROWAVE EYE FEATURE, WITH STRONG
CONVECTIVE BANDS BEGINNING TO WRAP UPSHEAR ON THE EAST SIDE OF THE
LOW LEVEL CIRCULATION CENTER (LLCC). THE 37GHZ IMAGE SHOWED A
LOW-LEVEL MICROWAVE EYE AS WELL, DISPLACED SLIGHTLY TO THE
SOUTHWEST OF THE UPPER-LEVEL EYE FEATURE. THE INITIAL POSITION IS
ASSESSED WITH HIGH CONFIDENCE BASED ON THE MICROWAVE EYE, AND SHOWS
THAT THE SYSTEM HAS BECOME QUASI-STATIONARY OVER THE PAST SIX
HOURS. THE INITIAL INTENSITY FOR THE 061200Z BEST TRACK WAS
INCREASED TO 70 KNOTS BASED ON COINCIDENT SMAP AND SMOS L-BAND
RADIOMETER PASSES AROUND 1300Z, WHICH SHOWED MAX WINDS IN THE 70-75
KNOT RANGE. THE 061800Z INTENSITY IS HELD STEADY AT 70 KNOTS, WITH
HIGH CONFIDENCE, BASED ON PERSISTENCE WITH THE EARLIER SMAP AND
SMOS DATA, AND A CIMSS D-MINT ESTIMATE OF 70 KNOTS BASED ON THE GMI
MICROWAVE IMAGE ABOVE. SUBJECTIVE AND OBJECTIVE ESTIMATES CONTINUE
TO LAG BEHIND, AND CURRENTLY ARE IN THE 55-60 KNOT RANGE. ANALYSIS
REVEALS A FAVORABLE ENVIRONMENT, WITH LOW TO MODERATE EASTERLY
SHEAR, VERY WARM SSTS WITH HIGH OHC AND GOOD POLEWARD AND
EQUATORWARD OUTFLOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: NEAR EQUATORIAL RIDGE (NER) TO THE
SOUTH AND AN EXTENSION OF THE SUBTROPICAL RIDGE (STR) TO THE NORTH
IN A BLOCKING POSITION. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   KNES: T3.5 - 55 KTS
   DEMS: T2.5 - 35 KTS
   CIMSS ADT: 57 KTS AT 061800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: LOW

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: PEAK INTENSITY HAS BEEN INCREASED
SIGNIFICANTLY BASED ON RECENT RAPID DEVELOPMENT TREND. 

FORECAST DISCUSSION: OVER THE PAST FEW HOURS, TC 02A HAS SLOWED
DOWN SIGNIFICANTLY AND BASICALLY BECOME QUASI-STATIONARY BASED ON
THE RECENT MICROWAVE IMAGERY ANALYSIS. THE CULPRIT IN THIS
UNEXPECTED TRACK MOTION IS AN EXTENSION OF THE STR CENTERED OVER
ETHIOPIA, WHICH HAS BUILT EASTWARD AND LIES ROUGHLY ALONG THE 20N
LATITUDE LINE. THIS RIDGE IS EFFECTIVELY BLOCKING MUCH IN THE WAY
OF POLEWARD MOVEMENT FOR THE TIME BEING. HOWEVER, MODELS INDICATE
THAT THIS RIDGE WILL BREAK DOWN OVER THE NEXT 24 HOURS AS A
SHORTWAVE TROUGH PASSES BY TO THE NORTH AND A RIDGE COMPLEX BUILDS
OVER WESTERN INDIA. BY TAU 36, THE RIDGE OVER INDIA WILL BECOME THE
DOMINANT STEERING INFLUENCE, AND TC 02A WILL START TO PICK UP SPEED
ON A NORTHWARD TRACK. AFTER TAU 72, THE RIDGE OVER INDIA CONTINUES
TO STRENGTHEN, MOVE NORTHWEST AND BEGIN TO ELONGATE TO A MORE
NORTHWEST-SOUTHEAST AXIS. THIS CHANGE IN THE DEEP-LAYER PATTERN
WILL SUPPORT A SHIFT TO A NORTHWEST TRACK THROUGH THE REMAINDER OF
THE FORECAST PERIOD. FROM AN INTENSITY PERSPECTIVE, TC 02A CLEARLY
HAS OUTPERFORMED EXPECTATIONS UP TO THE CURRENT TIME. CIMSS AMV
ANALYSIS CLEARLY SHOWS THAT WHILE THE ENVIRONMENTAL SHEAR IS
RELATIVELY HIGH FROM THE EAST, THE RECENT UPSHEAR CONVECTIVE
DEVELOPMENT IS PUSHING BACK, AND COCOONING THE DEVELOPING CORE IN A
LOW SHEAR ENVIRONMENT. THUS, IN THE NEAR-TERM, RAPID
INTENSIFICATION IS EXPECTED TO CONTINUE, TO A PEAK OF 100 KNOTS BY
TAU 36. AFTER THIS POINT A SLOW BUT STEADY WEAKENING IS EXPECTED AS
A RESULT OF MULTIPLE FACTORS INCLUDING DECREASED OUTFLOW ALOFT,
INCREASING SHEAR AND AFTER TAU 72, ENTRAINMENT OF A SIGNIFICANT
AMOUNT OF DRY DESERT AIR FROM THE WEST. 

MODEL DISCUSSION: TRACK GUIDANCE CONTINUES TO SHOW A BIFURCATION,
WITH THE UKMET, GALWEM AND THEIR ENSEMBLES TRACKING THE SYSTEM DUE
NORTH THROUGH THE FORECAST PERIOD AND THE GFS, NAVGEM, AND ECMWF
AND THEIR ENSEMBLE MEANS, TRACKING THE SYSTEM GENERALLY NORTH
THROUGH TAU 72, THEN TURNING TOWARDS THE ARABIAN PENINSULA. THE
JTWC FORECAST LIES CLOSE TO THE CONSENSUS MEAN TO TAU 48, THEN
HEDGES WEST OF THE CONSENSUS AND CLOSE TO THE ECMWF SOLUTION
THEREAFTER. SIGNIFICANT UNCERTAINTY IN ECENS AND GEFS ENSEMBLE
MEMBERS COMBINED WITH THE BIFURCATION IN THE DETERMINISTIC
TRACKERS LEADS TO OVERALL LOW CONFIDENCE IN THE TRACK FORECAST,
PARTICULARLY AFTER TAU 72. INTENSITY GUIDANCE IS FRANKLY NOT
PROVIDING MUCH ASSISTANCE IN DETERMINING THE FORECAST INTENSITY,
WITH A VERY SIGNIFICANT DISAGREEMENT BETWEEN THE CONSENSUS MEMBERS,
WHICH RANGE FROM THE HWRF PEAKING AT THE PRESENT INTENSITY, ALL THE
WAY UP TO THE DTOP RAPID INTENSIFICATION (RI) AID PEAKING AT 130
KNOTS. BASED ON THE RECENT TREND IN CONVECTIVE DEVELOPMENT, AND THE
L-BAND RADIOMETER WIND MEASUREMENTS, IT IS CLEAR THAT THE SYSTEM IS
DOING BETTER THAN ANTICIPATED. AS LONG THE CONVECTION CAN CONTINUE
TO DEVELOP AND WRAP FURTHER UPSHEAR, IT IS EXPECTED THAT THE RI
TREND WILL CONTINUE AND THE JTWC FORECAST JUST A SHADE BELOW THE
RIPA GUIDANCE THROUGH TAU 36, THEN SLOWLY REJOINS THE BULK OF THE
GUIDANCE AND LIES RIGHT ON THE SHIPS (BOTH GFS AND NAVGEM)
INTENSITY TRACKER AFTER TAU 96. DUE TO THE VERY LARGE UNCERTAINTIES
SURROUNDING THE NEAR-TERM EVOLUTION OF THE INNER CORE OF THE SYSTEM
AND THE SIGNIFICANT SPREAD IN THE GUIDANCE, THERE IS LOW CONFIDENCE
IN THE JTWC FORECAST INTENSITY. 

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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