WDPN32 PGTW 110900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 16W (PODUL) WARNING NR 
018//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.7N 132.2E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 424 NM SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 25 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS PERSISTENT
DEEP CONVECTION RESISTING STRONG AND DRY NORTHEASTERLY VERTICAL
WIND SHEAR. THE DEEP CONVECTION OBSCURES THE LOW-LEVEL CIRCULATION
CENTER (LLCC), BUT THE CONVECTION REMAINS VERTICALLY STACKED. AN
EARLIER 110426Z GCOM W-1 AMSR2 37GHZ IMAGE REVEALS A DISTINCT
LOW-LEVEL BANDING. THE 89GHZ IMAGE FROM THE SAME SATELLITE PASS
DEPICTS DEEP CONVECTION OBSCURING THE CENTER BUT SHEARED TO THE 
SOUTH. UPPER-LEVEL DIFFLUENCE TO THE SOUTHEAST IS EVIDENT ON
WATER VAPOR IMAGERY. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON THE AFOREMENTIONED MSI. THE INITIAL INTENSITY
OF 55 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: T3.5 - 55 KTS
   RJTD: T4.0 - 65 KTS
   RCTP: T3.5 - 55 KTS
   KNES: T3.5 - 55 KTS
   CIMSS SATCON: 53 KTS AT 110055Z
   CIMSS ADT: 43 KTS AT 110220Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 25-30 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG 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: TROPICAL STORM (TS) 16W WILL CONTINUE WEST FOR
THE NEXT 12 HOURS BEFORE GRADUALLY CURVING NORTHWESTWARD FOR THE 
REMAINDER
OF THE FORECAST PERIOD. THE SUBTROPICAL RIDGE TO THE NORTH WILL
STEER THE SYSTEM AND BUILD DURING THIS TIME FRAME. IRREGULAR TRACK
MOTION MAY OCCUR IMMEDIATELY PRIOR TO LANDFALL AROUND TAU 48. THE
EASTERN TAIWAN COAST IS KNOWN FOR TRACK DEFLECTION RESULTING FROM
TERRAIN-INDUCED VORTICITY WITH THE CENTRAL MOUNTAIN RANGE (CMR).
HISTORICALLY, THIS HAS RESULTED IN UNUSUAL LOOPING AND CURVING OF
TROPICAL CYCLONES APPROACHING COASTAL TAIWAN. THE ENVIRONMENT WILL
REMAIN MARGINALLY FAVORABLE FOR DEVELOPMENT IN THE NEAR-TERM
FORECAST, LEADING TO A PEAK INTENSITY OF 70KTS BY TAU 24.
UPPER-LEVEL NORTHEASTERLY DIFFLUENCE WILL PROVIDE A FAVORABLE EXHAUST 
FOR TS 16W AND HIGHLY FAVORABLE WARM SEA SURFACE TEMPERATURES WILL 
FUEL THE STORM FROM THE OCEAN SURFACE. HIGH VERTICAL WIND SHEAR OF 25-
30KTS FROM AN ENHANCED UPPER-LEVEL RIDGE TO THE NORTH WILL PERSIST
THROUGHOUT THE FORECAST, RESULTING IN A RESTRICTED RATE OF
INTENSIFICATION TO THE PEAK. AT TAU 48, LANDFALL AND TOPOGRAPHIC
INTERACTION WITH THE HIGH ELEVATION OF THE CMR WILL INITIATE A
PERIOD OF WEAKENING. BETWEEN TAU 48-72, TS 16W WILL RE-EMERGE OVER
THE TAIWAN STRAIT WITH HIGH SHEAR AND LOW OCEAN HEAT CONTENT BEFORE
MAKING LANDFALL ON MAINLAND CHINA. THE MOUNTAINOUS TERRAIN WILL
WEAKEN THE CYCLONIC STRUCTURE OF TS 16W AND LEAD TO DISSIPATION BY
TAU 96.

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE IS IN GOOD AGREEMENT
THAT TS 16W WILL TRACK WESTWARD DURING THE NEXT 12 HOURS, AND THE 
CROSS TRACK SPREAD OPENS TO 100NM BY TAU 36. THE INTENSITY GUIDANCE IS 
HIGHLY SENSITIVE TO SLIGHT DEVIATIONS IN THE TRACK. ECMWF DEPICTS A 
STRONGER RATE OF INTENSIFICATION WITH A TRACK LYING TO THE SOUTH OF 
THE JTWC MULTI-MODEL CONSENSUS TRACK SOLUTIONS, WHILE GFS LIES NORTH 
OF THE CONSENSUS MEAN AND IS WEAKER DUE TO CLOSER INTERACTION WITH 
ENHANCED UPPER-LEVEL FLOW, HIGHER SHEAR, AND DRIER AIR ENTRAINMENT. 
THE CONFIDENCE FOR THE INTENSITY FORECAST IN THE LATE-TERM IS LESS
CONFIDENT THAN THE NEAR-TERM DUE TO THE SLIGHT DEVIATIONS IN THE
TRACK GUIDANCE.

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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