Advisories

WDPN32 PGTW 100900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 13W (PEILOU) WARNING NR 
014//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.1N 151.0E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 249 NM SOUTHWEST OF MINAMI TORI SHIMA
   MOVEMENT PAST 6 HOURS: EAST-NORTHEASTWARD AT 22 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
STORM (TS) 13W (PEILOU) AS A PARTIALLY EXPOSED LOW-LEVEL CIRCULATION 
CENTER (LLCC) WITH DRY AIR WRAPPING AROUND THE WESTERN PERIPHERY INTO 
THE CORE. THE 100546Z SSMIS MICROWAVE IMAGE REVEALS A SHALLOW SYSTEM 
WITH THE LOWER-LEVEL CLOUD LINES WRAPPING IN UNDER THE CENTRAL DEEP 
CONVECTION. THE CENTRAL CONVECTION HAS LITTLE TO NO STRUCTURE, AND 
HAS REMAINED RELATIVELY UNCHANGED OVER THE PAST 6 HOURS. 
ENVIRONMENTAL ANALYSIS REVEALS A MARGINAL ENVIRONMENT, CHARACTERIZED 
BY LOW (10-15 KTS) VERTICAL WIND SHEAR (VWS), WARM (28-29 C) SEA 
SURFACE TEMPERATURES (SST), AND GOOD POLEWARD OUTFLOW SUPPORTED BY AN 
UPPER-LEVEL TROUGH SITUATED TO THE NORTHWEST, OFFSET BY MODERATE 
AMOUNTS OF MID-LEVEL DRY AIR ENTRAINMENT FROM THE WEST. THE INITIAL 
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE AFOREMENTIONED 
100546Z SSMIS MICROWAVE DATA. THE INITIAL INTENSITY OF 40 KTS IS 
ASSESSED WITH HIGH CONFIDENCE BASED ON THE CIMSS AUTOMATED INTENSITY 
ESTIMATES AND AGENCY DVORAK FIXES LISTED BELOW, SUPPORTED BY THE 
100313Z AMSR2 WINDSPEED PRODUCT REVEALING 40 KT WINDS IN THE 
SOUTHEASTERN QUADRANT.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: LOW-LEVEL WESTERLY MONSOONAL FLOW AND
EASTERN EXTENSION OF A NEAR EQUATORIAL RIDGE (NER) CENTERED TO THE
SOUTHWEST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 47 KTS AT 100500Z
   CIMSS ADT: 49 KTS AT 100630Z
   CIMSS AIDT: 40 KTS AT 100630Z
   CIMSS D-MINT: 33 KTS AT 100546Z
   CIMSS D-PRINT: 30 KTS AT 100630Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: UPPER-LEVEL TROUGH POSITIONED TO THE NORTHWEST

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TS 13W IS FORECAST TO CONTINUE TRACKING
EAST-NORTHEASTWARD FOR THE DURATION OF THE FORECAST PERIOD, WHILE
THE SHALLOW VORTEX REMAINS UNDER THE STEERING INFLUENCE OF THE
STRONG MONSOONAL WESTERLIES AND THE NER CENTERED IN THE PHILIPPINE
SEA. REGARDING INTENSITY, 13W IS FORECAST TO GRADUALLY WEAKEN
THROUGH TAU 60 AS ITS ENVIRONMENT BECOMES INCREASINGLY UNFAVORABLE. 
THE UPPER-LEVEL TROUGH CURRENTLY SUPPORTING STRONG POLEWARD OUTFLOW 
IS EXPECTED TO PASS OVER THE SYSTEM BETWEEN TAU 24-36, INDUCING
STRONGER NORTHWESTERLY VWS AND SIGNIFICANT DRY AIR ENTRAINMENT. THE
COMBINATION OF THESE FACTORS, PLUS THE LOSS OF THE UPPER-LEVEL
SUPPORT PROVIDED BY THE TROUGH, IS ANTICIPATED TO INDUCE PEILOU'S
TERMINAL WEAKENING AND ULTIMATE DISSIPATION NO LATER THAN TAU 60.

MODEL DISCUSSION: DETERMINISTIC MODEL TRACK GUIDANCE IS IN STRONG
AGREEMENT THROUGH TAU 60, SUPPORTING THE JTWC TRACK FORECAST WITH
HIGH CONFIDENCE. LIKEWISE, RELIABLE INTENSITY GUIDANCE IS IN STRONG
AGREEMENT IN A GRADUAL WEAKENING TREND THROUGHOUT THE DURATION OF
THE FORECAST PERIOD, SUPPORTING THE JTWC INTENSITY FORECAST WITH
HIGH CONFIDENCE.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   INTENSITY 00-72 HR: HIGH//
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