WDPN31 PGTW 181500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 24W (HAITANG)      
WARNING NR 003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 31.0N 159.0E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 487 NM NORTH-NORTHEAST OF MINAMI TORI
SHIMA
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 11 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
PARTIALLY-EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) ON THE
NORTHWESTERN EDGE OF A CURVED CONVECTIVE BAND. AN 181043Z MHS 89GHZ
MICROWAVE IMAGE SHOWS FRAGMENTED BANDING OVER THE SOUTHEAST
QUADRANT WITH A WEAKLY-DEFINED LLCC. HOWEVER, AN 180958Z ASCAT-C
IMAGE SHOWS AN ASYMMETRIC WINDFIELD WITH A DEFINED CIRCULATION AND
A SWATH OF 30-32 KNOT WINDS OVER THE SOUTHEASTERN QUADRANT. THIS
SUPPORTS THE INITIAL POSITION WITH HIGH CONFIDENCE. THE INITIAL
INTENSITY OF 35 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE
ASCAT IMAGE AND IS HEDGED SLIGHTLY HIGHER THAN THE 32 KNOT MAXIMUM
WINDS BASED ON ITS LOW BIAS. ENVIRONMENTAL CONDITIONS ARE
MARGINALLY FAVORABLE WITH LOW VERTICAL WIND SHEAR AND EASTWARD
OUTFLOW OFFSET BY DRY AIR ENTRAINMENT AND BORDERLINE SST VALUES
(26C).

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: NORTHWESTERN PERIPHERY OF A
DEEP-LAYERED SUBTROPICAL RIDGE (STR) POSITIONED TO THE EAST AND
SOUTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T1.5 - 25 KTS
   KNES: T1.5 - 25 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 25-26 CELSIUS
   OUTFLOW: MODERATE EASTWARD
   OTHER FACTORS: EXTENSIVE MID- TO UPPER-LEVEL DRY AIR

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 24W IS FORECAST TO RECURVE NORTHEASTWARD TO
EAST-NORTHEASTWARD THROUGH THE FORECAST PERIOD ALONG THE
NORTHWESTERN TO NORTHERN PERIPHERY OF THE STR. THE SYSTEM WILL
BEGIN EXTRA-TROPICAL TRANSITION (ETT) NEAR TAU 12 AS IT BEGINS TO
INTERACT WITH THE MIDLATITUDE WESTERLIES. TS 24W WILL COMPLETE ETT
BETWEEN TAU 24 AND TAU 36 AS IT MERGES WITH A STRONG FRONTAL ZONE
AND TRACKS OVER COOLER SST VALUES (24-25C).

MODEL DISCUSSION: WITH THE EXCEPTION OF AN ERRONEOUS AFUM TRACKER,
NUMERICAL MODEL GUIDANCE IS IN TIGHT AGREEMENT LENDING HIGH
CONFIDENCE TO THE JTWC FORECAST TRACK. RELIABLE INTENSITY GUIDANCE
SUPPORTS A BRIEF INTENSIFICATION TO 35-40 KNOTS THEN A STEADY
WEAKENING TREND THROUGH TAU 36. THERE IS A POSSIBILITY THAT THE
SYSTEM MAY DISSIPATE PRIOR TO COMPLETING ETT.

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