WDPN31 PGTW 080900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 05W (HAGUPIT) WARNING NR 
011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 8.7N 138.9E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 67 NM SOUTHEAST OF YAP
   MOVEMENT PAST 6 HOURS: WESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS POORLY
ORGANIZED DEEP CONVECTION DISPLACED EAST OF THE LOW-LEVEL
CIRCULATION CENTER (LLCC) AND A FEW BRIEF PULSES OF CONVECTION TO
THE WEST. MODERATE UPPER LEVEL OUTFLOW PRODUCING AMPLE CIRRUS
LEAVES THE LLCC COMPLETELY OBSCURED IN THE MSI. A 080437Z AMSR-2 89
GHZ MICROWAVE IMAGE EXPOSED SOME EVIDENCE OF LOW-LEVEL BANDS
WRAPPING INTO THE LLCC BENEATH THE CIRRUS CANOPY. THE INITIAL
POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED PRIMARILY ON
EXTRAPOLATION FROM THE AMSR-2 IMAGE. LACKING ANY RECENT WIND SPEED
DATA, THE INITIAL INTENSITY OF 40 KTS IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON A BLEND OF THE AGENCY DVORAK FIXES AND CIMSS
INTENSITY ESTIMATES LISTED BELOW. THE ENVIRONMENT IS CHARACTERIZED
AS MARGINALLY FAVORABLE WITH MODERATE POLEWARD OUTFLOW, WARM (29-30
C) SEA SURFACE TEMPERATURES, AND MODERATE VERTICAL WIND SHEAR
(VWS). A LAYER OF SIGNIFICANTLY DRIER AIR BETWEEN 600-300 MB AND
MODERATE MID-LEVEL WESTERLY SHEAR SERVE TO OFFSET THE FAVORABLE
ENVIRONMENTAL FACTORS.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) POSITIONED FAR TO THE NORTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T3.5 - 55 KTS
   KNES: T3.0 - 45 KTS
   CIMSS SATCON: 44 KTS AT 080600Z
   CIMSS ADT: 55 KTS AT 080600Z
   CIMSS AIDT: 44 KTS AT 080600Z
   CIMSS D-MINT: 33 KTS AT 080417Z
   CIMSS D-PRINT: 29 KTS AT 080600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD
   OTHER FACTORS: DRY MID-LEVEL AIR ALONG THE WESTERN FLANK AND
MODERATE MID-LEVEL WESTERLY SHEAR.

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   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) 05W (HAGUPIT) IS FORECAST
TO CONTINUE ON A STEADY WEST-NORTHWESTWARD TRACK UNDER THE STEERING
INFLUENCE OF THE STR TO THE NORTHEAST THROUGH TAU 48. THE EASTWARD
MIGRATION OF THE STR WILL RESULT IN A WEAKER STEERING ENVIRONMENT
FOR 05W, CAUSING ITS TRACK SPEED TO SLOW AND TURN GRADUALLY
POLEWARD THROUGH THE END OF THE FORECAST PERIOD. THE OFFSETTING
ENVIRONMENTAL FACTORS PREVIOUSLY DISCUSSED ARE EXPECTED TO ALLOW
THE SYSTEM TO MAINTAIN ITS INTENSITY THROUGH TAU 36. AFTER TAU 36,
FURTHER ENHANCED DRY AIR ENTRAINMENT OVER THE PHILIPPINE SEA WILL
BE THE PRIMARY MECHANISM TO INITIATE A WEAKENING TREND THAT IS
FORECAST TO RESULT IN DISSIPATION BY TAU 96. DISSIPATION WILL BE
AIDED BY STEADILY INCREASING WESTERLY MID-LAYER SHEAR, DRY AIR
ENTRAINMENT, AND LOSS OF UPPER LEVEL OUTFLOW SUPPORT IN THE LATER
TAUS.

MODEL DISCUSSION: MODEL TRACK GUIDANCE IS IN GENERALLY GOOD
AGREEMENT ABOUT THE WEST-NORTHWESTWARD TRACK WITH A GRADUAL
POLEWARD TURN AFTER TAU 72. THE CROSS-TRACK SPREAD AT TAU 96 IS 230
NM, HOWEVER, THE MAJORITY OF MODEL TRACKS ARE CLUSTERED AROUND THE
MULTI-MODEL CONSENSUS. THUS, THE JTWC TRACK FORECAST IS PLACED
CLOSE TO THE MULTI-MODEL CONSENSUS WITH HIGH CONFIDENCE THROUGH TAU
72, AND MEDIUM CONFIDENCE THEREAFTER OWING TO UNCERTAINTY ABOUT THE
DISSIPATING STRUCTURE AND POLEWARD TURN. THE INTENSITY GUIDANCE,
WITH THE EXCEPTION OF THE SHIPS MEMBERS, HAS COME INTO VERY GOOD
ALIGNMENT WITH THE LATEST MODEL RUN, WITH THE REST OF THE MEMBERS
REMAINING WITHIN AN ENVELOPE OF ABOUT 5 KTS THROUGH THE ENTIRE
FORECAST PERIOD. THE JTWC INTENSITY FORECAST IS PLACED ON THE
HIGHER END OF THIS ENVELOPE WITH HIGH CONFIDENCE THROUGH TAU 72 AND
MEDIUM CONFIDENCE THEREAFTER.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   TRACK 72-120 HR: MEDIUM
   INTENSITY 00-72 HR: HIGH
   INTENSITY 72-120 HR: MEDIUM//
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