WDPN31 PGTW 090300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 05W (HAGUPIT) WARNING NR 
014//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 8.7N 136.1E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 156 NM NORTHEAST OF ANGAUR
   MOVEMENT PAST 6 HOURS: WESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
THE INITIAL POSITION OF TROPICAL STORM (TS) 05W (HAGUPIT) IS PLACED
WITH HIGH CONFIDENCE BASED ON A 080022Z METOP-B ASCAT PASS THAT
CAPTURES THE SLIGHTLY ELONGATED LOW LEVEL CIRCULATION CENTER
(LLCC). THE WESTERN FLANK REMAINS EXPOSED INDICATING A DRY AIRMASS,
WITH STRONGER FLARING CONVECTION TO THE EAST OF THE LLCC.
ENVIRONMENTAL ANALYSIS REVEALS MIXED CONDITIONS WITH LOW TO MODERATE
(10-15 KTS) VERTICAL WIND SHEAR (VWS), WARM (29-30 C) SEA SURFACE
TEMPERATURES (SSTS), OFFSET BY SIGNIFICANT DRY AIR ENTRAINMENT
FROM THE WEST AND MODERATE TO HIGH (20-25 KTS) MID-LEVEL SHEAR.
THE INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH MEDIUM CONFIDENCE,
BASED ON A 082037Z RCM-2 SAR PASS, AND THE AGENCY DVORAK AND
INTENSITY AID FIXES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) CENTERED FAR TO
THE NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 35 KTS AT 082213Z
   CIMSS ADT: 41 KTS AT 082030Z
   CIMSS AIDT: 35 KTS AT 082030Z
   CIMSS D-MINT: 25 KTS AT 082212Z
   CIMSS D-PRINT: 27 KTS AT 090030Z

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

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 05W IS FORECAST TO CONTINUE ITS
WEST-NORTHWESTWARD TRACK THROUGHOUT THE REMAINDER OF THE FORECAST
PERIOD. THE STEERING HAS BEEN CONTROLLED PREDOMINANTLY BY THE
SUBTROPICAL RIDGE (STR) SITUATED FAR TO THE NORTHEAST THUS FAR.
HOWEVER, AS THE STR INCREASES DISTANCE FROM TS HAGUPIT, AND THE
SYSTEMS SLOWLY WEAKENS, THE STORM WILL BECOME INFLUENCED MAINLY BY
THE LOW-LEVEL EASTERLY FLOW. WEAK AND COMPETING STEERING
ENVIRONMENT WILL EVENTUALLY RESULT IN A POLEWARD TRACK SHIFT, WHILE
THE SYSTEM IS EXPECTED TO SLOW DOWN PRIOR TO TAU 72. TS 05W IS
FORECAST TO MAINTAIN ITS 35 KT INTENSITY UNTIL TAU 48, AT WHICH
POINT ENVIRONMENTAL EFFECTS OF SHEAR AND DRY AIR WILL RESULT IN ITS
DISSIPATION, WHICH IS EXPECTED TO COMPLETE BY TAU 72. 

MODEL DISCUSSION: CROSS TRACK SPREAD AMONGST THE MULTI MODEL
CONSENSUS REMAINS ABOUT 50 NM UNTIL TAU 72, BY WHICH IT WIDENS TO
130 NM. THE TRACK WAS LAID WITH MEDIUM CONFIDENCE FOR THE REMAINDER
OF THE FORECAST PERIOD, IN GOOD AGREEMENT WITH THE JTWC CONSENSUS
AND INTERPOLATED AIDS BUT CONSIDERING THAT THE COMPETING STEERING
ENVIRONMENT MAY CAUSE TS 05W TO TRACK MORE WESTWARD SHOULD THE STR
LOSE ITS STEERING INFLUENCE. THE INTENSITY AIDS SHOW FAR MORE
SPREAD, WITH HAFS AND COAMPS-TC FORECASTING A SLIGHTLY INCREASED
INTENSITY PEAK OF 50 KTS AT TAU 48. THE JTWC INTENSITY CONSENSUS IS
LOWER AND DEPICTS A SIMILAR FLATTENING TREND UNTIL DISSIPATION. THE
OFFICIAL JTWC INTENSITY FORECAST IS PLACED SLIGHTLY BELOW THE
CONSENSUS, WITH MEDIUM CONFIDENCE, DUE TO A 20-25 KTS GUIDANCE
ENVELOPE SPREAD.

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