Advisories

WDPN31 PGTW 040300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 30W (IN-FA) WARNING NR 047//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 24.4N 138.4E
   INITIAL INTENSITY: 85 KTS
   GEOGRAPHIC REFERENCE: 160 NM WEST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 28 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TYPHOON (TY) 30W IS HOLDING ITS OWN AGAINST MODERATE TO HIGH
VERTICAL WIND SHEAR (VWS). DEEP CONVECTION HAS MANAGED TO WRAP
AROUND THE 25-NM WIDE EYE, AND THE AVERAGE CLOUD TOP TEMPERATURE OF
THE CENTRAL DENSE OVERCAST (CDO) HAS GRADUALLY COOLED. ANIMATED
MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS OVERSHOOTING TOPS
ALONG THE EYEWALL AS THE SYSTEM TIGHTENS UP, WITH EXCELLENT
POLEWARD OUTFLOW FEEDING TO A JET STREAK TO THE NORTH. HOWEVER, THE
MSI AND A 032027Z SSMIS PASS INDICATE THAT THE VORTEX IS
SIGNIFICANTLY TILTED EASTWARD WITH HEIGHT. THIS TILT IS PRIMARILY
DUE TO 20-25 KTS OF MID-LEVEL WESTERLY SHEAR. DESPITE THIS SHEAR,
WARM SEA SURFACE TEMPERATURES (SST) NEAR 27 DEGREES CELSIUS AND
STRONG POLEWARD OUTFLOW HAVE BEEN SUFFICIENT FOR INTENSIFICATION
OVER THE PAST 12 HOURS. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON THE EYE IN MSI. THE INITIAL INTENSITY IS SET AT
85 KTS WITH MEDIUM CONFIDENCE NEAR THE HIGHER END OF THE OBJECTIVE
ESTIMATES. THE INITIAL WIND RADII ARE ASSESSED WITH LOW CONFIDENCE
BASED ON AN ASCAT PASS FROM 031156Z.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WESTERN FLANK OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED NEAR 26N 155E

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   RJTD: T4.5 - 77 KTS
   RCTP: T4.5 - 77 KTS
   CIMSS ADT: 94 KTS AT 040000Z
   CIMSS AIDT: 79 KTS AT 040000Z
   CIMSS D-MINT: 81 KTS AT 032028Z
   CIMSS D-PRINT: 79 KTS AT 040000Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 20-25 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: STRONG POLEWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THE FORECAST HAS BEEN TRUNCATED TO 48
HOURS.

FORECAST DISCUSSION: TY 30W CONTINUES TO TURN POLEWARD ALONG THE
WESTERN PERIPHERY OF THE STR. THE SYSTEM WILL CROSS THE RIDGE AXIS
BY TAU 12 AND TURN TOWARD THE EAST. NEAR TAU 24, A PROGRESSIVE
LONGWAVE TROUGH PASSING OVER THE KOREAN PENINSULA AND HONSHU WILL
DRAMATICALLY INCREASE THE MAGNITUDE OF THE STEERING FLOW ON THE
NORTHWESTERN PERIPHERY OF THE STR, CAUSING THE VORTEX TO RAPIDLY
ACCELERATE NORTHEASTWARD, REACHING A FORWARD SPEED NEAR 40 KTS BY
TAU 48. TY 30W IS LIKELY AT OR NEAR PEAK INTENSITY FOR THIS ROUND
OF INTENSIFICATION. WHILE SST WILL REMAIN ABOVE 26 DEGREES CELSIUS
THROUGH TAU 24, VWS ASSOCIATED WITH MID- TO UPPER-LEVEL WESTERLY
FLOW WILL INCREASE IMMINENTLY, RESULTING IN GRADUAL TO STEADY
WEAKENING. TOWARD THE END OF THE FORECAST, BAROCLINIC
REINTENSIFICATION IS FORECAST AS THE SYSTEM TRAVELS AT HIGH SPEED,
ENCOUNTERS STRONG TEMPERATURE ADVECTION AND UPPER-LEVEL SUPPORT,
AND UNDERGOES EXTRATROPICAL TRANSITION. THE SYSTEM SHOULD BECOME A
POWERFUL, TY-FORCE EXTRATROPICAL CYCLONE BY TAU 48.

MODEL DISCUSSION: TRACK GUIDANCE IS IN GOOD AGREEMENT, WITH
ALONG-TRACK SPREAD MARKEDLY IMPROVED OVER THE PREVIOUS CYCLE.
NAVGEM IS STILL THE SLOWEST MODEL, BUT GFS, ECMWF, AIFS, AND GOOGLE
DEEPMIND HAVE CONVERGED TOWARD A TIGHTER GROUPING AT TAU 48. THE
JTWC FORECAST TRACK HAS AGAIN SHIFTED SLIGHTLY WESTWARD FOR THE
FIRST 24 HOURS AND IS POSITIONED ALONG THE CENTER OF THE TIGHT
GUIDANCE ENVELOPE. BEYOND TAU 24, THE JTWC FORECAST TRACK HEDGES
TOWARD THE TIGHTER GROUP OF MODELS DESCRIBED ABOVE. ALL OF THE
INTENSITY AIDS EXCEPT FOR HWRF AND HAFS-A INDICATE WEAKENING
THROUGH TAU 36. HAFS-A AND HWRF HOLD THE INTENSITY STEADY FOR THE
FIRST 12 HOURS. FROM TAU 36 TO TAU 48, DEEPMIND IS FLAT, WHILE GFS
AND ECMWF DEPICT REINTENSIFICATION. THE JTWC INTENSITY FORECAST IS
SET NEAR THE DEEPMIND SOLUTION THROUGH TAU 36 AND NEAR GFS AND
ECMWF AT TAU 48.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: MEDIUM
   INTENSITY 00-72 HR: MEDIUM//
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