Advisories

WDPN31 PGTW 280300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 30W (IN-FA) WARNING NR 019//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.9N 159.9E
   INITIAL INTENSITY: 120 KTS
   GEOGRAPHIC REFERENCE: 817 NM EAST OF SAIPAN
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 35 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: 
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TYPHOON (TY) 
30W WITH AN IMPRESSIVE 40 NM DIAMETER EYE THAT HAS ALMOST COMPLETELY 
CLEARED OUT AND WARMED TO 19 DEGREES CELSIUS OVER THE PAST 6 HOURS. 
THE SURROUNDING CENTRAL DENSE OVERCAST IS HIGHLY SYMMETRIC WITH 
UNIFORM COLD CLOUD TOPS. A 271859Z RCM-3 SAR PASS REVEALED THAT THE 
SYMMETRY IS ALSO REFLECTED IN THE RELATIVELY COMPACT SURFACE WIND 
FIELD. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON 
THE CENTER OF THE EYE IN THE MSI. THE INITIAL INTENSITY OF 120 KTS IS 
ASSESSED WITH MEDIUM CONFIDENCE BASED ON A BLEND OF THE AGENCY DVORAK 
FIXES AND CIMSS INTENSITY ESTIMATES, ALTHOUGH THERE IS SOME 
UNCERTAINTY IN THOSE ESTIMATES GIVEN THE LARGE EYE. THE ENVIRONMENT IS 
CHARACTERIZED AS FAVORABLE, WITH WARM SEA SURFACE TEMPERATURES, GOOD 
RADIAL OUTFLOW ALOFT, AND LOW VERTICAL WIND SHEAR.

INITIAL WIND RADII BASIS: SAR DATA 

CURRENT STEERING MECHANISM: SOUTHERN FLANK OF A SUBTROPICAL RIDGE
EXTENSION TO THE NORTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   RJTD: T6.5 - 127 KTS
   RCTP: T6.0 - 115 KTS
   PHFO: T6.5 - 127 KTS
   CIMSS SATCON: 130 KTS AT 280000Z
   CIMSS ADT: 129 KTS AT 280000Z
   CIMSS AIDT: 122 KTS AT 280000Z
   CIMSS D-MINT: 121 KTS AT 272315Z
   CIMSS D-PRINT: 133 KTS AT 280000Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE RADIAL

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: THE TRACK SPEED OF TY 30W HAS INCREASED TO 8 KTS 
OVER THE PAST 6 HOURS AS IT ACCELERATES WEST-NORTHWESTWARD UNDER THE 
STEERING INFLUENCE OF THE RIDGE EXTENSION TO THE NORTH. THE TRACK IS 
FORECAST TO CONTINUE WEST-NORTHWESTWARD AND CURVE POLEWARD THROUGH TAU 
72 IN THIS ENVIRONMENT. A SECONDARY STR WILL BUILD IN FROM THE WEST, 
CREATING A COL REGION AND WEAK STEERING ENVIRONMENT FROM TAU 72 
ONWARDS. THE SYSTEM IS EXPECTED TO HAVE A PERIOD OF ERRATIC AND 
SOMETIMES QUASI STATIONARY MOTION DURING THAT TIME, ALTHOUGH THAT 
CANNOT BE EXPLICITLY REPRESENTED IN THE TRACK FORECAST. THE TRACK 
FORECAST INSTEAD PLACES THE POSITION AT TAU 96 AND 120 IN THE GENERAL 
AREA OF THE MEAN MOTION VECTOR. THE INTENSITY OF TY 30W HAS REBOUNDED 
OVER THE PAST 12 HOURS AND IS FORECAST TO CONTINUE INCREASING TO A 
PEAK AROUND 130 KTS BEFORE LEVELING OFF. THE LARGE DIAMETER EYE AND 
SOME ATTEMPTS AT EYEWALL REPLACEMENT CYCLES ARE EXPLICITLY DEPICTED IN 
THE HAFS-A MODEL FIELDS WHICH WILL CONTRIBUTE TO THE INTENSITY CAP AND 
LATER GRADUAL WEAKENING. AFTER TAU 96, COLD WATER UPWELLING RESULTING 
FROM THE SLOW TRACK SPEED IS EXPECTED TO FURTHER CONTRIBUTE TO THE 
WEAKENING TREND.

MODEL DISCUSSION: MODEL TRACK GUIDANCE IS IN VERY GOOD AGREEMENT 
THROUGH TAU 72, WITH A CROSS-TRACK SPREAD OF 65 NM AT THAT TIME AND 
MINIMAL ALONG-TRACK SPREAD. AFTER TAU 72 THE GUIDANCE SUITE DEPICTS A 
VARIETY OF SOLUTIONS WITH A FAIRLY WIDE SPREAD, BUT GENERALLY WITH 
WESTWARD AND SOUTHWARD COMPONENTS. THE JTWC TRACK FORECAST IS PLACED 
NEAR THE CONSENSUS THROUGH TAU 72, THEN AT A SUBJECTIVE MEAN AMONG THE 
SPREAD OF GUIDANCE FOR THE LATE TAUS. THE LATEST INTENSITY GUIDANCE 
HAS COME INTO CLOSER AGREEMENT WITHIN A 20 KT ENVELOPE, WITH THE 
EXCEPTION OF GFS AS A LOW OUTLIER. THE JTWC INTENSITY FORECAST IS 
PLACED ON THE HIGHER END OF THE ENVELOPE IN RESPONSE TO THE RECENT 
INTENSIFICATION TREND.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   TRACK 72-120 HR: LOW
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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