WDPS31 PGTW 182100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 26P (GINA) WARNING NR 
002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.1S 169.2E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 164 NM NORTH-NORTHEAST OF PORT VILA,
VANUATU
   MOVEMENT PAST 6 HOURS: WESTWARD AT 03 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY AND A 181704Z
SSMIS 91GHZ MICROWAVE IMAGE DEPICTS A PARTIALLY EXPOSED LOW LEVEL
CIRCULATION CENTER (LLCC) WITH THE BULK OF THE DEEP CONVECTION
BEING SHEARED TO THE SOUTHEAST. THE INITIAL POSITION IS PLACED
WITH HIGH CONFIDENCE BASED ON EIR AND SSMIS IMAGERY. THE INITIAL
INTENSITY OF 35 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON PGTW
AND KNES DVORAK INTENSITY ESTIMATES AND CIMMS ADT AS WELL AS AN 
EARLIER ASCAT PASS.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE SOUTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   KNES: T2.5 - 35 KTS
   CIMSS ADT: 35 KTS AT 181740Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD

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: TC 26P IS FORECAST TO CONTINUE TRACKING UNDER
THE STEERING INFLUENCE OF THE STR TO THE SOUTHEAST. BY TAU 24 CURRENT 
ENVIRONMENTAL CONDITIONS, CHARACTERIZED BY WARM SEA SURFACE 
TEMPERATURES (SST) AND STRONG OUTFLOW ALOFT, COULD ALLOW TC 26P TO 
REACH A PEAK INTENSITY OF 45 KNOTS. BETWEEN TAU 24 AND TAU 48, THE 
ENVIRONMENT DETERIORATES AS DRY AIR BECOMES ENTRAINED IN THE SYSTEM 
AND VWS INCREASES (30-35KTS) LEADING TO A STEADY WEAKENING TREND. 
BETWEEN TAU 48 AND TAU 72 THE SYSTEM IS FORECAST TO TRACK SOUTH-
SOUTHWEST AS INCREASING LEVELS OF DRY AIR BECOME ENTRAINED INTO THE 
SYSTEM, LEADING TO THE INITIAL STAGES OF DISSIPATION. BY TAU 96, 
GINA WILL TRACK SOUTHEAST AND FULLY DISSIPATE OVER WATER. 

MODEL DISCUSSION: NUMERICAL MODELS ARE IN FAIR AGREEMENT WITH A
170NM SPREAD AT TAU 72. THE MODELS AGREE TO SOME EXTENT ON A
SOUTH-SOUTHWESTWARD THEN SOUTHEASTWARD TRACK. RELIABLE MODEL
INTENSITY GUIDANCE SHOWS AN EQUALLY FAIR AGREEMENT IN INTENSITY.
BASED ON THIS FAIR AGREEMENT IN MODEL GUIDANCE JTWC TRACK AND
INTENSITY IS PLACED WITH MEDIUM CONFIDENCE.

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