Tropical Storm SANBA Advisory Mon Sep 17

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 17W (SANBA) WARNING NR 26//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 17W (SANBA), LOCATED APPROXIMATELY 75 NM SOUTHWEST
OF PUSAN, SOUTH KOREA, HAS TRACKED NORTHWARD AT 17 KNOTS OVER THE
PAST SIX HOURS. THE CURRENT POSITION IS BASED ON RECENT SATELLITE
FIXES FROM PGTW AND RJTD AND RADAR DATA FROM JAPAN AND KOREA. THE
CURRENT INTENSITY OF 80 KNOTS IS CONSISTENT WITH DVORAK ESTIMATES
FROM KNES, PGTW, AND RJTD. TY 17W IS TRACKING POLEWARD IN THE
GRADIENT BETWEEN A SUBTROPICAL STEERING RIDGE EAST OF JAPAN AND A
MIDLATITUDE TROUGH TO THE NORTHWEST OF THE CYCLONE. RECENT ANIMATED
MULTISPECTRAL SATELLITE IMAGERY INDICATES THAT EXTRATROPICAL
TRANSITION HAS BEGUN, WITH SOUTHWESTERLY VERTICAL WIND SHEAR AHEAD
OF THE APPROACHING TROUGH DISPLACING MOST OF THE CONVECTION TO
THE NORTH OF THE LOW LEVEL CIRCULATION CENTER (LLCC) AND
STRATOCUMULUS CLOUD LINES WRAPPING INTO THE LLCC FROM THE NORTHWEST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TY 17W WILL ACCELERATE NORTH-NORTHEASTWARD ACROSS THE KOREAN
PENINSULA OVER THE NEXT 24 HOURS AND COMPLETE EXTRATROPICAL
TRANSITION BY TAU 12. ALTHOUGH INTERACTION WITH THE TAEBAEK MOUNTAIN
RANGE AND INCREASING VERTICAL WIND SHEAR ARE EXPECTED TO INDUCE
STEADY WEAKENING, THE SYSTEM SHOULD MAINTAIN GALE-FORCE INTENSITY
UNDER THE INFLUENCE STRONG POLEWARD DIVERGENCE ALOFT DURING
EXTRATROPICAL TRANSITION. THE AVAILABLE NUMERICAL GUIDANCE REMAINS
IN VERY TIGHT AGREEMENT. THE CURRENT FORECAST LIES SLIGHTLY AHEAD OF
THE MODEL CONSENSUS IN ANTICIPATION OF A STRONGER STEERING FLOW THAN
DEPICTED IN MANY OF THE CONSENSUS MEMBER MODEL FIELDS. THERE IS HIGH
CONFIDENCE IN THE TRACK FORECAST.//
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