WDPN31 PGTW 210900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 01W (SANVU) WARNING NR 
008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 10.1N 156.2E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 156 NM NORTH-NORTHEAST OF OROLUK
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 02 KTS
   SIGNIFICANT WAVE HEIGHT: 17 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A SMALL
REGION OF PERSISTENT DEEP CONVECTION FULLY OBSCURING THE LLCC WHILE
LOW LEVEL FEATURES ARE EXPOSED TO THE WEST AS A RESULT OF DRY AIR
INTRUSION. A 230306Z SUITE OF AMSR2 MICROWAVE IMAGERY SPECIFICALLY
AN 89GHZ COLOR COMPOSITE IMAGE INDICATE A KIDNEY BEAN SHAPED DEEP
CONVECTIVE CORE WITH A SINGLE FRAGMENTED BANDING FEATURE TO THE
NORTH OF THE LLCC. THE INITIAL POSITION IS PLACED WITH MEDIUM
CONFIDENCE BASED ON EIR AND ASMR2 IMAGERY. THE INITIAL INTENSITY OF
45 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON A CONSENSUS
AMONGST REPORTING DVORAK AGENCIES OF T3.0 AND CIMSS OPEN-AIR WHICH
ALSO INDICATES 43KTS WHILE CIMSS SATCON AND ADT REMAIN SLIGHTLY
HIGHER.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WEAK STEERING FLOW AS THE SYSTEM
TRANSITIONS STEERING TO A SUB-TROPICAL RIDGE (STR) BUILDING TO THE 
NORTH. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T3.0 - 45 KTS
   KNES: T3.0 - 45 KTS
   CIMSS SATCON: 50 KTS AT 210319Z
   CIMSS ADT: 53 KTS AT 210630Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 5-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE RADIAL

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 01W (SANVU) IS FORECAST TO EXIT A WEAK
STEERING ENVIRONMENT OVER THE NEXT 12 HOURS AS A STR TO THE NORTH
CONTINUES TO BUILD ITS INFLUENCE. DURING THIS TIME, THE ENVIRONMENT
SURROUNDING 01W IS ANTICIPATED TO REMAIN A STALEMATE AS WARM SSTS
AND GOOD OUTFLOW ALOFT GENERALLY COUNTERACT STEADILY INCREASING
MIDLEVEL VERTICAL WIND SHEAR (VWS) AND DRY AIR ENTRAINMENT. IT IS
IMPORTANT TO KEEP IN MIND THAT A FEW DEGREES NORTH OF THE SYSTEM,
LIES A SHARP GRADIENT OF BOTH MOISTURE AND VWS AND AS THE SYSTEM
TRACKS INTO THAT GRADIENT THE INTENSITY WILL CONSEQUENTLY FALL.
NEAR TAU 48, AS THE SYSTEM APPROACHES THE 12TH PARALLEL, INTENSITIES 
WILL CONTINUE TO FALL AS 01W TRACKS GENERALLY WESTWARD. AS VWS AND DRY 
AIR ENTRAINMENT CONTINUE TO INCREASE, THE SYSTEM WILL BE TORN APART 
AND EVENTUALLY DISSIPATE NEAR TAU 96.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN GOOD AGREEMENT WITH ALL
MEMBERS INDICATING A GRADUAL WESTWARD TURN AS THE STR TAKES
STEERING CONTROL. WHILE BETTER THAN YESTERDAY, THERE IS STILL A
MILD AMOUNT OF CROSS TRACK SPREADING WITH NVGM, HWRF AND AFUM
POLEWARD OF THE CONSENSUS WHILE COAMPS-TC, ECMWF AND JGSM AND THEIR
RESPECTIVE ENSEMBLES ARE EQUATORWARD. FOR THIS REASON THE JTWC
FORECAST TRACK IS PLACED CLOSE TO THE MULTI-MODEL CONSENSUS WITH
MEDIUM CONFIDENCE. WITH THE EXCEPTION OF DECAY-SHIPS, RELIABLE
MODEL INTENSITY GUIDANCE IS IN GOOD AGREEMENT THAT 01W WILL
GENERALLY STAGNATE OVER THE NEXT 12 HOURS AFTER WHICH ALL MEMBERS
WEAKEN THE SYSTEM THROUGH THE FORECAST PERIOD. FOR THIS REASON THE
JTWC INTENSITY FORECAST IS PLACED INITIALLY WITH MEDIUM CONFIDENCE
AND EVENTUALLY WITH HIGH CONFIDENCE.

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