WDPN32 PGTW 100900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 16W (PODUL) WARNING NR 
014//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.6N 137.3E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 598 NM EAST-SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: WESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS EXPOSED
LOW-LEVEL CLOUD BANDS ALONG THE NORTHERN PERIPHERY OF TROPICAL
STORM (TS) 16S. ANIMATED ENHANCED INFRARED IMAGERY (EIR) REVEALS
WARMING CLOUD TOPS AND COLLAPSING DEEP CONVECTION INDICATING A
WEAKENING PERIOD. THERE IS A DISTINCT VERTICAL TILT SOUTHWESTWARD
WITH HEIGHT DUE TO STRONG NORTHEASTERLY VERTICAL WIND SHEAR AND
ASSOCIATED DRY AIR. OUTFLOW ON WATER VAPOR IMAGERY IS MODERATE AND
EQUATORWARD WHILE DEEP CONVECTION CLEARLY FLARES UPSTREAM AGAINST
THE NORTHEASTERLY UPPER-LEVEL FLOW. THE INITIAL POSITION IS PLACED
WITH HIGH CONFIDENCE BASED ON A 100604Z DMSP F-18 SSMIS MICROWAVE
IMAGE HIGHLIGHTING THE SHALLOW BANDING ALONG THE NORTHERN
PERIPHERY. THE 91GHZ IMAGE FROM THE SAME SATELLITE PASS ACCENTUATES
THE SOUTHWARD VERTICAL TILT AND SHALLOW STRUCTURE. THE INITIAL
INTENSITY OF 50 KTS IS ASSESSED WITH LOW CONFIDENCE BASED ON THE
AGENCY AND OBJECTIVE FIXES LISTED BELOW.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: AN ELONGATED SUBTROPICAL RIDGE TO THE
NORTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   RJTD: T4.5 - 77 KTS
   KNES: T4.0 - 65 KTS
   CIMSS SATCON: 52 KTS AT 100500Z
   CIMSS ADT: 55 KTS AT 100700Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 25-30 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: LOW
   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 16W WILL TRACK WESTWARD OVER THE NEXT 48
HOURS UNDER THE STEERING INFLUENCE OF AN EXTENSION OF A SUBTROPICAL
RIDGE TO THE NORTH. AFTER TAU 72, THE ELONGATED RIDGE WILL CENTER
AND BUILD OVER THE EAST CHINA SEA. DURING THIS TIME, THE SYSTEM
WILL ASSUME A NORTHWESTERLY TRACK WHILE ROUNDING THE SOUTHWESTERN
QUADRANT OF THE RIDGE. 
HIGH VERTICAL WIND SHEAR WILL PERSIST THROUGHOUT THE FORECAST
PERIOD RESULTING IN A GRADUAL RATE OF INTENSIFICATION IN THE
EARLY-TERM INTENSITY FORECAST. THE HIGH SHEAR WILL BE COUNTERED BY
FAVORABLE UPPER-LEVEL DIFFLUENCE AND WARM SEA SURFACE TEMPERATURES,
CONTRIBUTING TO A PEAK OF 65KTS AT TAU 48 WHEN UPPER-LEVEL
DIFFLUENCE BECOMES SLIGHTLY MORE FAVORABLE. AS THE SYSTEM CURVES
NORTHWESTWARD BETWEEN TAU 48-72, TS 16W WILL BE INUNDATED BY
ENHANCED UPPER-LEVEL NORTHEASTERLY FLOW INJECTING DRY AIR INTO THE
CORE OF THE CIRCULATION AND ERODING THE VERTICAL STRUCTURE WITH
HIGH VERTICAL WIND SHEAR. WEAKENING WILL CONTINUE AS THE SYSTEM
PASSES INTO SHALLOWER AND COOLER WATER JUST PRIOR TO LANDFALL
BETWEEN TAU 72-96. TOPOGRAPHIC INTERACTION ON MAINLAND OF CHINA
WILL DISSIPATE THE SYSTEM FULLY BY THE END OF THE FORECAST PERIOD.

MODEL DISCUSSION: THERE IS SPREAD IN THE DETERMINISTIC AND ENSEMBLE
GUIDANCE WHICH REPRESENTS TRACK SOLUTIONS SPANNING FROM NORTH OF
TAIWAN TO SOUTH OF THE ISLAND. THERE IS A SIGNIFICANT POSSIBILITY
THAT IF TS 16W TRACK INTERACTS WITH NORTHEASTERN TAIWAN AROUND TAU
72, AND THERE MAY BE TRACK DEFLECTION AND IRREGULAR MOTION DUE TO
TERRAIN-INDUCED INTERACTION WITH THE CENTRAL MOUNTAIN RANGE (CMR).
THE TRACK GUIDANCE IS STRONGLY ASSOCIATED WITH THE INTENSITY
OUTCOME, SINCE TRACKS TO THE NORTH WILL BE STRONGLY INFLUENCED BY
VERTICAL WIND SHEAR AND DRY AIR FROM THE ENHANCED UPPER-LEVEL FLOW,
AND TRACKS TO THE SOUTH WILL REMAIN IN MORE ADVANTAGEOUS CONDITIONS
FOR DEVELOPMENT AND INTENSIFICATION WITH LOWER VERTICAL WIND SHEAR
AND HIGHER MOISTURE. AS SUCH, THE JTWC TRACK FORECAST IS LOW AFTER
TAU 72, AND THE INTENSITY FORECAST CONFIDENCE FOLLOWS SUIT.

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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