WDPN31 PGTW 041500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (HINNAMNOR) 
WARNING NR 030//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 27.8N 124.7E
   INITIAL INTENSITY: 105 KTS
   GEOGRAPHIC REFERENCE: 183 NM WEST-NORTHWEST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 45 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A SMALL
10NM EYE WITH SLIGHTLY FRAGMENTED DEEP CONVECTIVE BANDING WRAPPING
INTO THE CIRCULATION CENTER. A 041202Z GMI 89GHZ MICROWAVE IMAGE
REVEALS THAT WHAT WAS ONCE A COMPLETE OUTER EYEWALL FEATURE HAS
SINCE FRAGMENTED AND IS NOW MORE INDICATIVE OF A BANDING FEATURE.
ANIMATED UPPER LEVEL WATER VAPOR IMAGERY REVEALS THAT MID-UPPER
LEVEL DRY AIR INTRUSION MAY BE THE CULPRIT FOR THIS FRAGMENTATION.
THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON EIR
AND GMI IMAGERY. THE INITIAL INTENSITY OF 105 KTS IS ASSESSED WITH
MEDIUM CONFIDENCE BASED ON PGTW, KNES AND CIMSS ADT INTENSITY
ESTIMATES MAINTAINING T5.5 WHILE RJTD DVORAK INTENSITY ESTIMATE IS
A T5.0.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) TO THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.5 - 102 KTS
   RJTD: T5.0 - 90 KTS
   KNES: T5.5 - 102 KTS
   CIMSS ADT: 105 KTS AT 041200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD
   OTHER FACTORS: DRY AIR ENTERTAINMENT FROM THE WEST

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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: STILL TRACKING GENERALLY NORTHWARD UNDER THE
STEERING INFLUENCE OF THE STR TO THE EAST, TY 12W HAS STARTED
SHOWING SIGNS OF DRY AIR ENTERTAINMENT WITHIN THE PREVIOUSLY FORMED
OUTER EYEWALL. WHILE THIS IS NOT A FAVORABLE OCCURRENCE, IF THE
INNER CORE OF THE SYSTEM CAN WITHSTAND THE DRY AIR, INTENSIFICATION
TO A MAXIMUM OF 115 KNOTS WITHIN THE NEXT 12 HOURS IS STILL
POSSIBLE. THIS IS BECAUSE IN THE SHORT TERM THE SYSTEMS ENVIRONMENT
REMAIN FAVORABLE, CHARACTERIZED BY WARM SEA SURFACE TEMPERATURES
(29C-30C), LOW VERTICAL WIND SHEAR (10-15KTS) AND VIGOROUS
DUAL-CHANNEL OUTFLOW BOTH POLEWARD AND EQUATORWARD. THIS
ENVIRONMENT WILL NOT LAST LONG HOWEVER, NEAR TAU 24 THE SYSTEM WILL
STEADY UP ON A GENERALLY NORTHEASTWARD TRACK AS IT ROUNDS THE STR
AND ACCELERATES TOWARDS THE KOREAN PENINSULA. NOW OVER COOLER
WATERS, 12W WILL START TO INTERACT WITH THE STRONG UPPER-LEVEL LOW
AND TROUGH MOVING IN FROM THE WEST WHICH WILL BOMBARD THE SYSTEM
WITH DRY AIR AND DRAMATICALLY INCREASE VERTICAL WIND SHEAR AS WELL
AS FURTHER ACCELERATE 12W NORTHEASTWARD. NEAR TAU 36 THIS
INTERACTION WITH THE PASSING TROUGH WILL BEGIN TO ROB THE SYSTEM OF
ITS TROPICAL CHARACTERISTICS AND THEREBY START EXTRATROPICAL
TRANSITION (ETT) AS THE SYSTEM PASSES OVER THE SOUTHERN COAST OF
SOUTH KOREA. BY TAU 48 THE SYSTEM WILL STILL HAVE MUCH OF ITS
FORMER INTENSITY AS IT IS STRIPPED OF ITS REMAINING TROPICAL
CHARACTERISTICS AND BECOMES FULLY INCORPORATED IN THE MIDLATITUDE
TROUGH THEREBY COMPLETING ETT.

MODEL DISCUSSION: WITH THE EXCEPTION OF JGSM, NUMERICAL MODELS ARE
IN TIGHT AGREEMENT WITH THE JTWC FORECAST TRACK SHOWING A 75NM
SPREAD AT TAU 48. FOR THIS REASON THE JTWC FORECAST TRACK IS PLACED
WITH HIGH CONFIDENCE. RELIABLE MODEL INTENSITY GUIDANCE IS IN POOR
AGREEMENT SHOWING A 20 KNOT SPREAD IN SOLUTIONS BY TAU 12. MODEL
OUTPUT IS NOW DEVOID OF RAPID INTENSIFICATION AIDS AND AS MENTIONED
MODEL OUTPUT IS SPREAD BETWEEN INTENSIFICATION, STAGNATION AND
IMMEDIATE WEAKENING. MODEL GUIDANCE DOES HOWEVER, ALL AGREE THAT
TAU 12 IS THE BEGINNING OF THE END FOR 12W AFTER WHICH ALL MEMBERS
TREND DOWNWARD THROUGH THE FORECAST PERIOD. BASED ON THE ABOVE
MENTIONED FAVORABLE ENVIRONMENTAL FACTORS IN THE SHORT TERM, AND
THE CONSENSUS AFTER TAU 12 THE JTWC INTENSITY FORECAST IS PLACED
WITH MEDIUM CONFIDENCE. 

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