Tropical Storm NOCK-TEN Advisory Sa, 27.12.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 30W (NOCK-TEN) WARNING NR 23//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 30W (NOCK-TEN), LOCATED APPROXIMATELY 215 NM WEST OF
MANILA, PHILIPPINES, HAS TRACKED WEST-NORTHWESTWARD AT 12 KNOTS OVER
THE PAST SIX HOURS. AFTER A BRIEF PERIOD OF RE-ORGANIZATION,
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY INDICATES THAT
CONVECTION IS ONCE AGAIN BECOMING RAGGED AND ASYMMETRIC,
PARTICULARLY ALONG THE NORTHERN PERIPHERY. THE EIR ALSO INDICATES
THAT LOW LEVEL CLOUDS ARE NOW BUILDING TO THE SOUTHWEST. IN THE
ABSENCE OF RECENT MICROWAVE IMAGERY, THE INITIAL POSITION IS BASED
ON PGTW AND RJTD FIXES WITH FAIR CONFIDENCE. THE INITIAL INTENSITY
IS REDUCED TO 65 KNOTS BASED ON PGTW AND RJTD DVORAK T4.0 (65 KNOTS)
ESTIMATES. UPPER-LEVEL ANALYSIS INDICATES THAT TY 30W IS NEARLY
UNDERNEATH THE SUBTROPICAL RIDGE (STR) AXIS, WITH GOOD POLEWARD
OUTFLOW PARTIALLY OFFSETTING INCREASING VERTICAL WIND SHEAR (VWS).
THE CYCLONE CONTINUES TO TRACK WEST-NORTHWESTWARD ALONG THE
SOUTHWESTERN PERIPHERY OF A DEEP-LAYERED STR WHICH REMAINS
ENTRENCHED TO THE NORTH OF THE SYSTEM.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY NOCK-TEN IS FORECAST TO CONTINUE TRACKING WEST-
NORTHWESTWARD OVER THE NEXT 6-12 HOURS UNDER THE STEERING INFLUENCE
OF THE STR, AFTER WHICH THE LLCC WILL BECOME FULLY EMBEDDED IN
NORTHEASTERLY FLOW ASSOCIATED WITH A COLD SURGE EVENT AND TURN
SHARPLY SOUTHWESTWARD. AT THAT TIME, DEEP CONVECTION WILL BECOME
DECOUPLED AND MOVE OFF TO THE NORTH-NORTHEAST, FOLLOWING THE MID- TO
UPPER-LEVEL FLOW. PRIOR TO THE SOUTHWESTWARD TURN, FAVORABLE UPPER
LEVEL DIFFLUENCE WILL RESULT IN GRADUAL WEAKENING, AFTER WHICH HIGH
(25-30 KNOT) VWS AND THE CONVECTIVE DECOUPLING WILL RESULT IN RAPID
WEAKENING. THE FORECAST CALLS FOR DISSIPATION BY TAU 48, HOWEVER,
ANALYSIS OF LOW LEVEL MODEL VORTICITY FIELDS SUGGESTS DISSIPATION
MAY OCCUR EVEN SOONER. DYNAMICAL MODEL GUIDANCE IS IN GOOD AGREEMENT
THROUGHOUT THE FORECAST PERIOD. THE JTWC FORECAST TRACK IS
POSITIONED CLOSE TO THE MULTI-MODEL CONSENSUS AND REMAINS CONSISTENT
WITH PREVIOUS FORECASTS, LEADING TO HIGH CONFIDENCE IN THE JTWC
FORECAST TRACK.//
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