WDPN31 PGTW 261500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 33W (KOTO) WARNING NR 
008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.5N 115.5E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 468 NM EAST-SOUTHEAST OF DA NANG, VIETNAM
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 26 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
STORM 33W (KOTO) WITH A LARGE, SYMMETRICAL CENTRAL DENSE OVERCAST
(CDO) OVER THE CENTER OF THE CIRCULATION. CIRRUS FILAMENTS CAN BE
SEEN EXPANDING OUTWARD FROM THE SYSTEM, INDICATIVE OF ROBUST
OUTFLOW. AS THE SYSTEM CONTINUES TO INTERACT WITH THE NORTHEASTERLY
SURGE, GALE-FORCE WIND RADII ARE EXPANDING, PARTICULARLY WITHIN THE
NORTHERN AND WESTERN SEMICIRCLES. THE INITIAL POSITION IS PLACED
WITH MEDIUM CONFIDENCE BASED ON THE ANIMATED EIR IMAGERY. THE
INITIAL INTENSITY OF 60 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
PRIMARILY ON THE AGENCY DVORAK ESTIMATES OF T3.5-4.0 (55-65 KTS)
DUE TO THE ABSENCE OF CIMSS OBJECTIVE INTENSITY ESTIMATES.
ENVIRONMENTAL ANALYSIS INDICATES THAT 33W IS IN A FAVORABLE
ENVIRONMENT CHARACTERIZED BY STRONG POLEWARD AND EQUATORWARD OUTFLOW
ALOFT, LOW (10-15 KTS) VERTICAL WIND SHEAR, AND WARM (28-29 C) SEA
SURFACE TEMPERATURES.

INITIAL WIND RADII BASIS: PERSISTENCE WITH SLIGHT ADJUSTMENTS BASED
ON THE OBJECTIVE BEST TRACK

CURRENT STEERING MECHANISM: A WEAK STEERING ENVIRONMENT WITH
RIDGING TO BOTH THE EAST AND WEST. 


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   RJTD: T4.0 - 65 KTS
   RCTP: T3.5 - 55 KTS
   KNES: T4.0 - 65 KTS
   DEMS: T4.0 - 65 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

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: 33W IS FORECAST TO TRACK GENERALLY WESTWARD
THROUGH TAU 48 WITH STEADILY DECREASING TRACK SPEEDS AS THE SYSTEM
TRACKS FURTHER INTO AN AREA OF WEAK STEERING INFLUENCE. AFTER TAU
48, A SLOW NORTHWESTWARD MOVEMENT IS FORECAST THROUGH TAU 96 AS
RIDGING OVER NORTHERN PHILIPPINES BUILDS BACK IN TO THE EAST OF THE
VORTEX. AFTER TAU 96, RIDGING OVER SOUTHEAST ASIA WILL BECOME THE
PRIMARY STEERING MECHANISM, CAUSING 33W TO TRACK WESTWARD TOWARD
THE COAST OF VIETNAM THROUGH TAU 120. REGARDING INTENSITY, 33W IS
FORECAST TO INTENSIFY THROUGH TAU 12 TO A PEAK OF AROUND 70 KTS AS
THE ENVIRONMENT REMAINS RELATIVELY FAVORABLE. HOWEVER, NEAR TAU 24,
SHEAR BEGINS TO QUICKLY INCREASE TO AROUND 25-30 KTS FROM THE
SOUTH. THIS SHEAR, ALONG WITH DRY AIR ENTRAINMENT ASSOCIATED WITH
THE NORTHEASTERLY SURGE, WILL CAUSE 33W TO WEAKEN THROUGH TAU 72.
AFTER TAU 72, SHEAR AND DRY AIR ARE EXPECTED TO LESSEN AS THE SURGE
BEGINS TO RETREAT, ALLOWING 33W TO GRADUALLY REDEVELOP AS IT
APPROACHES THE COAST OF VIETNAM. ADDITIONALLY, AROUND TAU 72,
GALE-FORCE WIND RADII ARE EXPECTED TO CONSIDERABLY SHRINK AS THE
SYSTEM DISTANCES ITSELF FROM THE INFLUENCE OF THE SURGE.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT THROUGH TAU 48, WITH THE EXCEPTION OF GALWEM, WHICH
TRACKS TE SYSTEM MUCH FURTHER NORTH. DISCOUNTING GALWEM, THERE IS
AN 85-NM CROSS TRACK SPREAD AT TAU 48. AFTER TAU 48, GFS BECOMES AN
ADDITIONAL OUTLIER, STALLING THE SYSTEM IN PLACE THROUGH TAU 96.
THE REST OF GUIDANCE GENERALLY AGREES ON A WESTWARD TRACK FOLLOWED
BY A SLOW NORTHWESTWARD JOG. THE JTWC FORECAST FOLLOWS THE BULK OF
GUIDANCE WITH MEDIUM CONFIDENCE THROUGH TAU 72 AND LOW CONFIDENCE
THEREAFTER. INTENSITY GUIDANCE AGREES ON INTENSIFICATION THROUGH
TAU 12-24 WITH WEAKENING AFTERWARD. HAFS-A AND GFS BOTH SUGGEST
INTENSIFICATION AFTER TAU 96, AS THE SYSTEM APPROACHES THE COAST OF
VIETNAM. THE JTWC INTENSITY FORECAST IS PLACED CLOSE TO THE HAFS-A
MODEL AND SLIGHTLY HIGHER THAN THE CONSENSUS WITH OVERALL MEDIUM
CONFIDENCE.

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