Advisories

WDPN31 PGTW 100900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 15E (NOLO) WARNING NR 
079//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 30.9N 146.2E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 420 NM SOUTHEAST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A PARTIALLY
EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) THAT IS BECOMING
INCREASINGLY ELONGATED, WITH SHALLOW CONVECTION CONFINED TO THE
NORTHERN AND EASTERN PERIPHERY. THE CIRCULATION APPEARS TO HAVE
BEGUN A TIGHT POLEWARD TURN. A 100301Z AMSR3 PASS INDICATED THAT
THE CORE STRUCTURE HAS ERODED IN THE SOUTHWEST QUADRANT, AND A
100230Z OSCAT-3 PASS REVEALED AN ASYMMETRIC WIND FIELD WITH 40-45
KT WINDS CONFINED TO THE NORTHERN SEMICIRCLE. BASED ON THE OSCAT-3
DATA, THE INITIAL INTENSITY HAS BEEN LOWERED TO 45 KTS WITH HIGH
CONFIDENCE. THIS ASSESSMENT IS HIGHER THAN THE SUBJECTIVE AND
OBJECTIVE ESTIMATES. THE INITIAL POSITION IS PLACED WITH MEDIUM
CONFIDENCE, HEDGED TOWARD THE RJTD AND RCTP FIXES. THE ENVIRONMENT
IS LARGELY UNFAVORABLE, CHARACTERIZED BY 25-30 KTS OF VERTICAL WIND
SHEAR (VWS), DRY AIR ENTRAINMENT, AND SEA SURFACE TEMPERATURES
(SST) OF 25-26 DEGREES CELSIUS. STRONG POLEWARD OUTFLOW ALOFT
PROVIDES INSUFFICIENT SUPPORT TO OFFSET THE OTHERWISE UNFAVORABLE
ENVIRONMENT.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: WESTERN FLANK OF A LOW- TO MID-LEVEL
SUBTROPICAL RIDGE (STR) CENTERED NEAR 32N 165E

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T1.5 - 25 KTS
   CIMSS ADT: 39 KTS AT 100540Z
   CIMSS D-MINT: 35 KTS AT 100401Z
   CIMSS D-PRINT: 38 KTS AT 100540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 25-30 KTS
   SST: 25-26 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 15E WILL CONTINUE TO EXECUTE A TIGHT
POLEWARD TURN OVER THE NEXT 12 HOURS, ROUNDING THE STR AXIS AND
TRANSITIONING TO A NORTHEASTWARD MOTION BY TAU 24. THE STRONGER
DEEP-LAYER WESTERLIES WILL REMAIN FAR TO THE NORTH. THEREFORE, TS
15E WILL NOT GAIN SIGNIFICANT FORWARD SPEED AFTER RECURVATURE. OVER
THE NEXT 24 HOURS, THE SYSTEM WILL INCREASINGLY COME UNDER THE
INFLUENCE OF THE SOUTHERN PERIPHERY OF A JET STREAM AND LOW-LEVEL
COLD AIR ADVECTION. VWS WILL INCREASE TO 30-40 KTS, WHICH WILL
STRIP AWAY THE REMAINING CONVECTION AND LEAVE A FULLY EXPOSED LLCC.
THE SYSTEM WILL UNDERGO EXTRATROPICAL TRANSITION (ETT) AT TAU 12
AND COMPLETE ETT BY TAU 24. HOWEVER, IF THE CIRCULATION FAILS TO
REMAIN COHERENT, THE SYSTEM MAY DISSIPATE AND OPEN INTO A TROUGH.

MODEL DISCUSSION: TRACK GUIDANCE IS IN REASONABLY GOOD AGREEMENT,
WITH MOST MEMBERS DEPICTING A CONTINUED TURN TOWARD THE NORTH AND
NORTHEAST OVER THE NEXT 24 HOURS. GOOGLE DEEPMIND LOSES THE
CIRCULATION AFTER TAU 12, WHILE THE SPREAD AMONG THE DYNAMICAL AND
REMAINING AI MODELS INCREASES AFTER TAU 12 DUE TO UNCERTAINTY
ASSOCIATED WITH CONTINUED STRETCHING OF THE LLCC AND POTENTIAL
DISSIPATION INTO A TROUGH. THE JTWC FORECAST TRACK IS SIMILAR TO
THE PREVIOUS FORECAST AND IS POSITIONED NEAR THE MULTI-MODEL
CONSENSUS (CONW) AND AI-MODEL MEAN, WHICH ARE VERY CLOSE TO EACH
OTHER. THE INTENSITY AIDS DEPICT STEADY WEAKENING. THE JTWC
INTENSITY FORECAST IS IN LINE WITH THIS SCENARIO AND IS SET BETWEEN
THE DEEPMIND AND GFS SOLUTIONS.

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