WDXS31 PGTW 060300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 03S (THREE) 
WARNING NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 9.7S 86.6E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 851 NM EAST-SOUTHEAST OF DIEGO GARCIA
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A LARGE
CLUSTER OF PERSISTENT DEEP CONVECTION OVER THE WESTERN SEMICIRCLE
OF A BROAD LOW-LEVEL CIRCULATION (LLC). EIR INDICATES INTENSE
FLARING CONVECTIVE TOPS OF -85C. A 052300Z SSMIS 89GHZ MICROWAVE
IMAGE DEPICTS FORMATIVE CONVECTIVE BANDING TO THE SOUTH AND WEST OF
THE LOW LEVEL CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS
PLACED WITH MEDIUM CONFIDENCE BASED ON THE EIR ALONG WITH THE SSMIS
MICROWAVE IMAGERY. A 051919Z AMSR2 WINDSPEED IMAGE SHOWS A SWATH OF
35-40 KNOT WINDS OVER THE WESTERN SEMICIRCLE WITH WEAKER WINDS OVER
THE CENTER AND EASTERN SEMICIRCLE. THE INITIAL INTENSITY OF 35 KTS
IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AMSR2 WINDSPEED
IMAGE, ALONG WITH THE IMPROVING CONVECTIVE STRUCTURE AS WELL AS A
COMBINATION OF AGENCY DVORAK INTENSITY ESTIMATES, WITH PGTW IN
PARTICULAR UP TO T2.0. HOWEVER, ENVIRONMENTAL CONDITIONS ARE
CURRENTLY MARGINALLY FAVORABLE WITH MODERATE POLEWARD OUTFLOW, WARM
(27-28C) SEA SURFACE TEMPERATURES (SSTS), OFFSET BY HIGH (25-30
KTS) VERTICAL WIND SHEAR.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: DEEP-LAYER SUBTROPICAL RIDGE (STR)
POSITIONED TO THE SOUTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   KNES: T2.5 - 35 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 25-30 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE POLEWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION: TC 03S WILL TRACK SOUTHWESTWARD OVER THE NEXT
24 HOURS, ALONG THE WESTERN PERIPHERY OF THE DEEP-LAYER SUBTROPICAL
RIDGE POSITIONED TO THE SOUTHEAST. THE STR IS EXPECTED TO REALIGN
TO A MORE SOUTHWEST TO NORTHEAST ORIENTATION AS A DEEP MID-LATITUDE
SHORTWAVE TROUGH IS FORECAST TO DIG IN NEAR THE SYSTEM AFTER TAU
48, WHICH COULD DRIVE TC 03S TO TRACK IN A MORE SOUTHWARD
DIRECTION. AS THIS OCCURS THE SYSTEM WILL ALSO TAP INTO INCREASED
POLEWARD OUTFLOW AND MOVE INTO A REGION OF LOWER VERTICAL WIND
SHEAR (VWS). THESE IMPROVED ENVIRONMENTAL FACTORS COULD ALLOW FOR A
BRIEF WINDOW OF INTENSIFICATION UP TO TAU 72. AFTER TAU 72, TC 03S
WILL BEGIN TO RAPIDLY SLOW DOWN IN FORWARD TRACK MOTION AND THEN
TURN SHARPLY WEST-NORTHWEST AS A TRANSITORY HIGH PRESSURE BUILDS
POLEWARD OF THE SYSTEM. BY TAU 96, 03S WILL CONTINUE TO TRANSIT
WEST-NORTHWEST ALONG THE NORTHERN EDGE OF THE STRONG HIGH, AS THIS
OCCURS THE SYSTEM WILL BEGIN TO GRADUALLY WEAKEN DUE TO THE
ENTRAINMENT OF COOLER, DRIER AIR.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT
WITH ONLY A 70NM CROSS-TRACK SPREAD THROUGH TAU 48, WITH A LARGE
SPREAD UP TO 200-300NM FROM TAU 72 TO TAU 120. THE PRIMARY OUTLIERS
ARE NAVGEM ON THE WESTERN EDGE OF THE AIDS ENVELOPE, AND EGRR ON
THE EASTERN EDGE. THEREFORE, THE JTWC TRACK IS POSITIONED CLOSE TO
THE MULTI-MODEL CONSENSUS. ADDITIONALLY, THE BULK OF THE ECMWF
ENSEMBLE (EPS) AND GFS ENSEMBLE (GEFS) SOLUTIONS ARE IN GOOD
AGREEMENT AND SUPPORT THE JTWC FORECAST TRACK WITH MEDIUM
CONFIDENCE. THE RELIABLE INTENSITY GUIDANCE IS LIMITED AS HWRF
INTENSITY GUIDANCE IS CURRENTLY NOT AVAILABLE, THE REST OF THE
GUIDANCE IS IN FAIR AGREEMENT. THEREFORE, THE JTWC INTENSITY
FORECAST FOLLOWS CLOSELY TO THE MULTI-MODEL INTENSITY CONSENSUS.   

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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