Advisories

WDPN31 PGTW 070900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 15E (NOLO) WARNING NR 067//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 25.9N 162.0E
   INITIAL INTENSITY: 70 KTS
   GEOGRAPHIC REFERENCE: 1682 NM WEST-NORTHWEST OF JOHNSTON ISLAND
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 18 KTS
   SIGNIFICANT WAVE HEIGHT: 33 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
BUFFETED BY 25-30 KTS OF NORTHEASTERLY VERTICAL WIND SHEAR (VWS),
THE CONVECTION ASSOCIATED WITH TYPHOON (TY) 15E HAS PERSISTED OVER
THE LOW-LEVEL CIRCULATION CENTER. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY (MSI) DEPICTS A COMPACT CENTRAL DENSE OVERCAST (CDO) THAT
HAS BECOME MORE RAGGED AND SLIGHTLY DISPLACED SOUTH OF THE LLCC. A
TIMELY 070526Z SSMIS PASS REVEALED AN INNER CORE OPEN TO THE NORTH,
WITH DEEP CONVECTION DISPLACED SOUTH OF THE LLCC, INDICATING
SOUTHWARD VORTEX TILT WITH HEIGHT. ALTHOUGH TY 15E IS TRACKING OVER
SEA SURFACE TEMPERATURES (SST) OF 28 DEGREES CELSIUS, HIGH VWS IS
OFFSETTING THIS OTHERWISE FAVORABLE CONDITION. THE INITIAL POSITION
IS PLACED WITH HIGH CONFIDENCE BASED ON THE MICROWAVE EYE FEATURE
IN THE SSMIS IMAGERY. THE INITIAL INTENSITY HAS BEEN LOWERED TO 70
KTS WITH MEDIUM CONFIDENCE, REFLECTING THE CONTINUED DETERIORATION
OF THE CONVECTIVE STRUCTURE. THIS ASSESSMENT IS NEAR THE T4.5
DVORAK CLASSIFICATIONS FROM PGTW, PHFO, RJTD, AND RCTP BUT LIES ON
THE HIGHER END OF THE OBJECTIVE ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR)

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   RJTD: T4.5 - 77 KTS
   RCTP: T4.5 - 77 KTS
   PHFO: T4.5 - 77 KTS
   CIMSS ADT: 59 KTS AT 070530Z
   CIMSS AIDT: 69 KTS AT 070530Z
   CIMSS D-MINT: 68 KTS AT 070526Z
   CIMSS D-PRINT: 70 KTS AT 070530Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 25-30 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE WESTWARD

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: TY 15E WILL CONTINUE WESTWARD TO
WEST-NORTHWESTWARD ALONG THE SOUTHERN FLANK OF AN AMPLIFIED STR.
DURING THE NEXT 60 HOURS, THE WESTERN EXTENSION OF THE RIDGE WILL
WEAKEN, ALLOWING THE SYSTEM TO GRADUALLY DECELERATE FROM 18 KTS TO
8 KTS BY TAU 60. CONCURRENTLY, TY 15E WILL TURN POLEWARD AS IT
ROUNDS THE STR AND CROSSES THE RIDGE AXIS AFTER TAU 60. FINALLY, IT
WILL ACCELERATE EAST-NORTHEASTWARD UNDER THE INCREASING INFLUENCE
OF DEEP-LAYER MID-LATITUDE WESTERLY FLOW. VWS WILL EASE TO 15-20
KTS BY TAU 12, WHICH WILL SLOW THE ONGOING WEAKENING TREND. AFTER
TAU 36, THE VORTEX WILL BRIEFLY GAIN ACCESS TO A FAVORABLE POLEWARD
OUTFLOW CHANNEL AND UPPER-LEVEL DIVERGENCE, SUPPORTING SLIGHT
INTENSIFICATION. AFTER THE SYSTEM ROUNDS THE STR AXIS, INCREASING
VWS, COOLER SSTS, AND INCREASING BAROCLINICITY WILL PROMOTE A
RENEWED WEAKENING TREND AND EXTRATROPICAL TRANSITION NEAR THE END
OF THE FORECAST PERIOD.

MODEL DISCUSSION: CROSS-TRACK SPREAD AMONG THE TRACK GUIDANCE IS
IMPROVING, PARTICULARLY SURROUNDING RECURVATURE. ALONG-TRACK SPREAD
GROWS AFTER TAU 72, REFLECTING UNCERTAINTY IN THE TIMING AND
LOCATION OF RECURVATURE. THE DYNAMICAL AIDS GENERALLY INITIATE THE
POLEWARD TURN FARTHER WEST AND MORE SLOWLY THAN THEIR AI
COUNTERPARTS. THE JTWC FORECAST TRACK IS POSITIONED USING A BLEND
OF THE MULTI-MODEL CONSENSUS AND GOOGLE DEEPMIND. THE INTENSITY
AIDS ARE IN GOOD AGREEMENT THROUGH THE FORECAST PERIOD, DEPICTING
WEAKENING THROUGH TAU 24 FOLLOWED BY SLIGHT INTENSIFICATION FROM
TAU 36 TO TAU 60. THE JTWC INTENSITY FORECAST IS SET NEAR THE
CENTER OF THE GUIDANCE ENVELOPE, NEAREST TO DEEPMIND AND GFS
THROUGH TAU 72, THEN NEAR THE AVERAGE OF THE DEEPMIND AND GFS
SOLUTIONS AT TAU 96 AND TAU 120.

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