WDPN34 PGTW 140300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 27W (USAGI) WARNING NR 
013//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.2N 123.1E
   INITIAL INTENSITY: 130 KTS
   GEOGRAPHIC REFERENCE: 106 NM SOUTHEAST OF APARRI, PHILIPPINES
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 52 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS THE
SYSTEM
HAS MAINTAINED ITS SUPER TYPHOON (STY) INTENSITY, AS EVIDENCED BY
ITS HIGHLY SYMMETRICAL AND COMPACT COLD CENTRAL COVER, THE ABSENCE
OF SIGNIFICANT FEEDER BANDS, AND A SHARPLY-OUTLINED PINHOLE 5NM
DIAMETER EYE THAT IS CYCLING THROUGH AN EYEWALL REPLACEMENT CYCLE
(ERC) AS INDICATED BY A LARGER EYE THAT IS TRYING TO FORM AROUND
IT. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON
THE WELL-DEFINED EYE. THE INITIAL INTENSITY OF 130KTS IS ALSO
PLACED WITH HIGH CONFIDENCE BASED ON IDENTICAL AND
TIGHTLY-CLUSTERED DVORAK INTENSITY ESTIMATES FROM THREE REPORTING
AGENCIES AND REFLECTS THE SUSTAINED 6-HR CONVECTIVE SIGNATURE IN
THE EIR LOOP. ANALYSIS INDICATES A HIGHLY FAVORABLE ENVIRONMENT
WITH VERY WARM ALONG-TRACK SST IN THE PHILIPPINE SEA, LOW VWS, AND
STRONG RADIAL OUTFLOW.

INITIAL WIND RADII BASIS: PERSISTENCE.

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE TO THE
NORTHEAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.5 - 127 KTS
   RJTD: T6.0 - 115 KTS
   RCTP: T6.5 - 127 KTS
   KNES: T6.5 - 127 KTS
   CIMSS ADT: 107 KTS AT 132330Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 05-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG RADIAL

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: STY USAGI WILL CONTINUE TO TRACK NORTHWESTWARD
AS IT BEGINS TO ROUND THE WESTERN RIM OF THE STEERING STR AXIS,
CLIP THE NORTHEASTERN TIP OF LUZON JUST EAST OF APARRI AROUND TAU
06 THEN TRACK INTO THE LUZON STRAIT AND MORE NORTHWARD AFTER TAU 24
AND CREST THE STR AXIS. A SECONDARY STR BUILDING IN FROM THE WEST
NEAR HAINAN WILL COMPETE FOR STEERING AND SLOW DOWN THE STORM
MOTION, RENDERING THE CYCLONE IN A QUASI-STATIONARY MODE IN THE COL
AREA BETWEEN THE TWO STRS AFTER TAU 48, AT BEST AT A VERY SLOW
NORTHEASTWARD PROGRESSION OFF THE SOUTHEASTERN COAST OF TAIWAN. THE
ENVIRONMENT WILL BECOME UNFAVORABLE AND LEAD TO A GRADUAL WEAKENING
DUE TO LAND INTERACTION WITH LUZON AND TAIWAN, COOLER SSTS AND
DECREASED OHC DUE TO UPWELLING IN THE COL, AND INCREASED VWS. BY
TAU 120, STY USAGI WILL BE REDUCED TO 45KTS. THERE IS A DISTINCT
POSSIBILITY THAT AROUND TAUS 36-48, THE SECONDARY STR WILL
ASSUME STEERING AND DRIVE THE SYSTEM SOUTHWESTWARD TOWARD THE SOUTH
CHINA SEA (BIFURCATION SCENARIO).   

MODEL DISCUSSION: NUMERICAL MODELS ARE IN TIGHT AGREEMENT WITH A
GRADUAL AND EVEN SPREAD TO A MERE 115NM AT TAU 36; HOWEVER, DUE TO
THE POTENTIAL BIFURCATION SCENARIO PROPOSED BY A SMALLER STRAND OF
MODELS INCLUDING NVGM, GFS, AND AEMN, THE MODEL ENVELOPE SPREADS
OUT SIGNIFICANTLY AND DIAMETRICALLY, LENDING OVERALL MEDIUM
CONFIDENCE IN THE JTWC TRACK FORECAST UP TO TAU 72 AND LOW
CONFIDENCE AFTERWARD. CONSEQUENTLY, THE CONFIDENCES AT BOTH TAUS
ARE THE SAME FOR THE INTENSITY FORECAST.  

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