Advisories

WDPN31 PGTW 302100Z 							
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON (IN-FA)     	
WARNING NR 030//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.5N 143.4E
   INITIAL INTENSITY: 115 KTS
   GEOGRAPHIC REFERENCE: 283 NM SOUTH-SOUTHEAST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 14 KTS
   SIGNIFICANT WAVE HEIGHT: 56 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TYPHOON
(TY) 30W (IN-FA) WITH A LARGE, WARM EYE MEASURING 42 NM ACROSS AND
MAINTAINING AN AVERAGE TEMPERATURE OF 19 C. THE CENTRAL DENSE 
OVERCAST (CDO) REMAINS SYMMETRICAL WITH A THICKNESS OF ROUGHLY 60 NM
AND DEVOID OF ANY OTHER DEEP CONVECTIVE BANDING. AN 301155Z METOP-C
ASCAT PASS REVEALED A MAXIMUM WIND SPEED OF 110 KTS, WITH THE 
SOUTHWESTERN QUADRANT HAVING SEVERAL AREAS OF ONLY 64 KT WINDS.
ENVIRONMENTAL CONDITIONS ARE ASSESSED AS FAVORABLE, WITH LOW 
(5-10 KTS) OF VERTICAL WIND SHEAR, WARM (28-29 C) SEA SURFACE
TEMPERATURES (SSTS), AND STRONG RADIAL OUTFLOW ALOFT. THE INITIAL
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE WELL-DEFINED 
EYE IN EIR. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE
IN GOOD AGREEMENT WITH THE AGENCY DVORAK FIXES AND CIMSS OBJECTIVE
ESTIMATES LISTED BELOW, SLIGHTLY ABOVE THE MOST RECENT SCATTEROMETER
DATA.

INITIAL WIND RADII BASIS: 301155Z METOP-C ASCAT DATA.

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE CENTERED TO THE
NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   RJTD: T6.0 - 115 KTS
   CIMSS SATCON: 108 KTS AT 301800Z
   CIMSS ADT: 97 KTS AT 301800Z
   CIMSS AIDT: 119 KTS AT 301800Z					

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

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TY 30W IS EXPECTED TO CONTINUE NORTH-
NORTHWESTWARD FOR THE NEXT 12 HOURS UNDER THE STEERING INFLUENCE OF
THE SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTHEAST. FROM TAUS 12
TO 24, THE SYSTEM IS EXPECTED TO TURN NORTHEASTWARD AS IT BEGINS 
ROUNDING THE STR AXIS AND THE PASSING OF A LONGWAVE TROUGH TO 
THE NORTH AT THIS SAME TIME. THIS WILL CAUSE A WEAKNESS IN THE 
STEERING RIDGE, RESULTING IN A SLOWER TRACK SPEED. A CLOCKWISE
LOOP IS PREDICTED BETWEEN TAUS 24 AND 48 AS THE QUICK PROPAGATION
OF THE TROUGH TO THE NORTH WILL QUICKLY ALLOW A SEPARATE STR
CENTERED TO THE NORTHWEST TO BUILD AND ASSUME STEERING INFLUENCE BY
TAU 48, CAUSING 30W TO RESUME A WEST-NORTHWESTWARD TRACK. BY TAU 72 
A SECOND, WEAKER TROUGH IS EXPECTED TO PROPAGATE NORTH OF THE SYSTEM
AND WEAKEN THE WESTERN STR, ALLOWING 30W TO ONCE AGAIN RECURVE THE 
AXIS OF THE ORIGINAL EASTERN STR BY TAU 72. REGARDING INTENSITY, 30W
IS EXPECTED TO CONTINUE A WEAKENING TREND FOR THE REMAINDER OF THE
FORECAST PERIOD AS IT WILL SOON MOVE INTO AN AREA OF LESS THAN 100
KJ PER CM SQUARED OF OCEAN HEAT CONTENT (OHC), EXACERBATED BY THE
SLOW IN TRACK SPEED AND LOOP THAT WILL CAUSE 30W TO UPWELL COOL SSTS.
MID-LEVEL VWS WILL ALSO RISE DURING THIS TIME PERIOD, CAUSING A 
STEEPER DECLINE IN INTENSITY BEFORE LEVELING OUT AS VWS ABATES AND 
TRACK SPEED INCREASES, ALLOWING 30W TO OUTRUN ITS COOL WAKE. BY TAU
72, VWS IS EXPECTED TO BEGIN INCREASING ONCE MORE AS 30W APPROACHES
THE STRONG UPPER-LEVEL WESTERLIES.


MODEL DISCUSSION: TRACK MODEL GUIDANCE IS IN GOOD AGREEMENT ON THE 
OVERALL SHAPE OF THE FORECAST TRACK WITH ALL MODELS DEPICTING AN
INITIAL NORTHEASTWARD RECURVE FOLLOWED BY A SHARP SOUTHWESTWARD 
TURN AND ULTIMATE POLEWARD TURN, HOWEVER DISAGREE ON THE TIMING AND
THUS LATITUDE OF THE INITIAL LOOP AND SHARPNESS OF THE SUBSEQUENT 
POLEWARD TURN. THIS RESULTS IN A CROSS-TRACK SPREAD OF 450 NM BY TAU 
120. A MAJORITY OF THE PHYSICS-BASED MODELS PORTRAY THE MOST 
EQUATORWARD TRACKS WHILE THE AI-BASED MODELS MAKE UP THE MOST 
EASTWARD AND POLEWARD SOLUTIONS. THE OFFICIAL JTWC FORECAST TRACK
IS PLACED WITH LOW CONFIDENCE THROUGHOUT BASED ON THE SPREAD OF
GUIDANCE, BUT HEDGED CLOSER TO THE AI CONSENSUS VICE THE MULTI-MODEL
CONSENSUS AS PHYSICS-BASED MODELS CONTINUE TO COME INTO AGREEMENT. 
INTENSITY MODEL GUIDANCE IS SPREAD AS THE DIFFERENCE IN MODEL TRACKS
IMPACTS THE RESULTANT INTENSITY, WITH GOOGLE DEEPMIND DEPICTING A
STEEPER WEAKENING TREND DUE TO ITS MORE POLEWARD TRACK INTO COOLER
SSTS WHILE HAFS-A PORTRAYS A PERIOD OF REINTENSIFICATION AS ITS 
TRACK TAKES 30W OVER AN AREA OF HIGHER OHC. THE OFFICIAL JTWC 
FORECAST INTENSITY IS ASSESSED WITH LOW CONFIDENCE THROUGHOUT, BUT
IN GOOD AGREEMENT WITH BOTH THE GOOGLE DEEPMIND AND THE GFS-BASED 
COAMPS-TC.

FORECAST CONFIDENCE:							
   TRACK 0 - 72 HR: LOW
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: LOW
   INTENSITY 72-120 HR: LOW//
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