Tropical Storm IN-FA Advisory za, 17-07

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 09W (IN-FA) WARNING NR
008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 22.9N 132.3E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 327 NM SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 19 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A BROAD,
ELONGATED LOW-LEVEL CIRCULATION CENTER (LLCC) OBSCURED BY DEEP
FLARING CONVECTION. A 172310Z GMI 89GHZ MICROWAVE IMAGE DEPICTS
SHALLOW BANDING WRAPPING INTO AN ELONGATED LOW LEVEL CIRCULATION
WITH A BROAD SWATH OF CONVECTION TO THE EAST. THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON A 180029Z ASCAT-B IMAGE
SHOWING A BROAD SWATH 30-35 KT WINDS IN THE EASTERN SEMICIRCLE AND
25 KT WINDS WRAPPING INTO THE WESTERN SEMICIRCLE. THE INITIAL
INTENSITY OF 35 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE
ASCAT-B IMAGE AND DVORAK ESTIMATES FROM PGTW, RJTD AND KNES.
ENVIRONMENTAL ANALYSIS INDICATES MARGINALLY FAVORABLE CONDITIONS
WITH WEAKENING UPPER-LEVEL WESTERLIES OFFSET BY ROBUST EQUATORWARD
OUTFLOW AND WARM SST VALUES.
INITIAL WIND RADII BASIS: SCATTEROMETER DATA
CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) OVER THE
NORTHEASTERN AND EASTERN PERIPHERY OF THE SYSTEM.
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T2.0 - 30 KTS
   RJTD: T2.0 - 30 KTS
   KNES: T2.5 - 35 KTS
   CIMSS ADT: 34 KTS AT 172040Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG EQUATORWARD
ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: HIGH
3. FORECAST REASONING.
SIGNIFICANT FORECAST CHANGES: POSITIONING OF FORECAST TRACK SHIFTED
SOUTHWARD AFTER TAU 96.
FORECAST DISCUSSION: TS 09W IS TRACKING NORTHWESTWARD ALONG THE
PERIPHERY OF THE STR TO THE NORTH BUT WILL BEGIN GRADUALLY TURNING
WEST-NORTHWESTWARD AFTER TAU 24 AS THE STR BEGINS TO SHIFT
WESTWARD. AT THE SAME TIME, THE SYSTEM SHOULD BEGIN TO SLOWLY
INTENSIFY AS ENVIRONMENTAL CONDITIONS GRADUALLY IMPROVE WITH
CONVERGENCE ALOFT WEAKENING, ALLOWING THE SYSTEM TO DEVELOP MORE
ROBUST POLEWARD OUTFLOW. AFTER TAU 72, TS 09W WILL TURN WESTWARD AS
THE STR TO THE NORTH CONTINUES TO BUILD. AS IMPROVED ENVIRONMENTAL
CONDITIONS PERSIST, TS 09W WILL STEADILY INCREASE IN INTENSITY
THROUGHOUT THE REMAINDER OF THE FORECAST WITH A PEAK INTENSITY OF
85 KNOTS ANTICIPATED BY TAU 120. OF NOTE, THE FORECAST TRACK HAS
SHIFTED SOUTHWARD AFTER TAU 96 DUE TO MODEL GUIDANCE SHOWING THE
STR TO THE NORTH BEGINNING TO EXTEND TOWARDS THE SOUTHWEST.
MODEL DISCUSSION: THERE IS MEDIUM CONFIDENCE ON THE NUMERICAL MODEL
GUIDANCE IN THE FORECAST TRACK UP TO TAU 72, AT WHICH POINT THE
MODELS BEGIN TO BIFURCATE, WITH NVGM AND UKMET TURNING
NORTHWESTWARD AND GFS AND ECMWF TURNING SOUTHWESTWARD. THIS LENDS
LOW CONFIDENCE TO THE REMAINDER OF THE FORECAST TRACK BEYOND TAU
72.
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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