WDXS33 PGTW 070900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 14S (TALIAH) WARNING 
NR 013//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.6S 99.5E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 254 NM SOUTHEAST OF THE COCOS ISLANDS
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 23 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
CYCLONE 14S (TALIAH) WITH A DEGRADED CONVECTIVE STRUCTURE COMPARED
TO 12 HOURS AGO. THE LOW-LEVEL CIRCULATION CENTER (LLCC) IS NOW
PARTIALLY EXPOSED ON THE EASTERN PORTION OF THE SYSTEM. THE CIRRUS
FILAMENTS THAT WERE ONCE VERY PROMINENT ARE NOW DISSIPATING.
ENVIRONMENTAL ANALYSIS INDICATES THAT 14S IS IN A MARGINAL
ENVIRONMENT CHARACTERIZED BY MODERATE EQUATORWARD OUTFLOW ALOFT,
MODERATE TO HIGH (20-25 KTS) EASTERLY VERTICAL WIND SHEAR, DRY AIR
ENTRAINMENT, AND WARM (27-28 C) SEA SURFACE TEMPERATURES. THE
INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE
PARTIALLY EXPOSED LLCC IN THE ANIMATED MSI. THE INITIAL INTENSITY
OF 45 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY
DVORAK AND OBJECTIVE INTENSITY ESTIMATES LISTED BELOW.
ADDITIONALLY, A 062253Z RCM-1 SAR IMAGE REVEALED 40-45 KTS IN THE
NORTHERN SEMICIRCLE WITH 35-40 KTS IN THE SOUTHERN SEMICIRCLE.

INITIAL WIND RADII BASIS: PERSISTENCE FROM THE MENTIONED SAR DATA.

CURRENT STEERING MECHANISM: NORTHWESTERN PERIPHERY OF A SUBTROPICAL
RIDGE (STR) POSITIONED TO THE SOUTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   KNES: T4.0 - 65 KTS
   DEMS: T3.5 - 55 KTS
   APRF: T3.0 - 45 KTS
   CIMSS SATCON: 47 KTS AT 070500Z
   CIMSS ADT: 49 KTS AT 070600Z
   CIMSS AIDT:39 KTS AT 070600Z
   CIMSS DPRINT: 46 KTS AT 070600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 20-25 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT 

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THE INITIAL INTENSITY DROPPED LOWER
THAN WHAT THE PREVIOUS FORECAST PORTRAYED. AS A RESULT, THE MAJORITY
OF THE FORECAST IS 15-20 KTS LOWER. 

FORECAST DISCUSSION: 14S IS FORECAST TO CONTINUE TRACKING
SOUTHWESTWARD OVER THE NEXT 12 HOURS AS A LONGWAVE TROUGH TO THE
SOUTH BREAKS DOWN THE CURRENT STEERING RIDGE. AFTER TAU 12, A RIDGE
TO THE SOUTHWEST IS EXPECTED TO BUILD, CAUSING THE SYSTEM TO TURN
NORTHWESTWARD THROUGH 48. AROUND TAU 48, THE RIDGE QUICKLY WEAKENS
AND CAUSES 14S TO ENTER A WEAK STEERING ENVIRONMENT THROUGH TAU 96.
TRACK SPEEDS ARE EXPECTED TO BE VERY SLOW WHILE THE SYSTEM IS
PLACED IN THE WEAKENED STEERING ENVIRONMENT. HOWEVER, AROUND TAU 96,
A RIDGE TO THE SOUTHEAST WILL BUILD, CAUSING 14S TO BEGIN
ACCELERATING SOUTHWESTWARD THOUGH THE REMAINDER OF THE FORECAST
PERIOD. REGARDING INTENSITY, 14S IS FORECAST TO MARGINALLY WEAKEN
FURTHER TO AROUND 40 KTS, IN RESPONSE TO THE DRY AIR BEING PULLED
INTO THE SYSTEM. THIS INTENSITY WILL THEN MAINTAIN THROUGH TAU 36.
AROUND TAU 36, THE ENVIRONMENT BEGINS TO MOISTEN, ALLOWING 14S TO
REINTENSIFY. POLEWARD OUTFLOW ALSO IMPROVES AROUND TAU 96, FURTHER
SUPPORTING INTENSIFICATION. AN INTENSITY OF 65 KTS IS FORECAST NEAR
TAU 120 AS THE VORTEX TRACKS SOUTHWESTWARD.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT
REGARDING THE TRACK OF 14S THROUGH TAU 48 WITH A 75 NM CROSS-TRACK
SPREAD AT THAT TIME. AFTER TAU 48, THE MAIN OUTLIER IS GFS WHICH
SLOWS TRACK SPEED SOONER THAN THE REMAINDER OF GUIDANCE. OVERALL,
GUIDANCE IS IN MUCH BETTER AGREEMENT AFTER TAU 48 THAN IN PREVIOUS
RUNS THOUGH. ALL GUIDANCE SHOWS THE SOUTHWESTWARD TURN STARTING
AROUND TAU 72. INTENSITY GUIDANCE IS IN WORSE AGREEMENT WITH
MESOSCALE MODELS SUGGESTING WEAKENING TO AROUND 30 KTS AT TAU 24-36
WHILE GFS SUGGESTS A STEADY 45 KTS. AFTER TAU 36, ALL GUIDANCE
DEPICTS INTENSIFICATION THROUGH THE END OF THE FORECAST PERIOD. THE
JTWC INTENSITY GUIDANCE IS PLACED WITH OVERALL MEDIUM CONFIDENCE,
NEAR THE MULTI-MODEL CONSENSUS.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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