Tropical Storm YUTU Advisory 11月1日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 31W (YUTU) WARNING NR
42//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 31W (YUTU), LOCATED APPROXIMATELY 258 NM
SOUTHEAST OF HONG KONG, HAS TRACKED NORTH-NORTHWESTWARD AT 04 KNOTS
OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY
SHOWS SLIGHT RE-CONSOLIDATION WITH FLARING CONVECTION REVIVING ALONG
THE SOUTHERN HALF OF A BROAD CIRCULATION THAT REMAINS PARTIALLY
EXPOSED. THE INITIAL POSITION IS EXTRAPOLATED FROM A LOW BRIGHTNESS
TEMPERATURE CIRCULATION FEATURE IN THE 311516Z 36GHZ GPM WITH FAIR
CONFIDENCE. THE INITIAL INTENSITY OF 50 KNOTS IS AVERAGED FROM DVORAK
ESTIMATES OF T3.0/45KTS FROM RJTD AND T3.5/55KTS FROM PGTW AND
REFLECTS THE SLIGHT INTENSIFICATION. THE SYSTEM IS CURRENTLY IN
MODERATE (15-20 KNOT) VERTICAL WIND SHEAR (VWS), THAT IS BEING OFFSET
BY A STRONG POLEWARD OUTFLOW. SST AND OHC VALUES ARE CONDUCIVE. THE
CYCLONE IS TRACKING ALONG THE WESTERN PERIPHERY OF A DEEP-LAYERED
SUBTROPICAL RIDGE (STR) TO THE EAST.
3. FORECAST REASONING.
   A. THE FORECAST TRACK IS CUT TO 48 HOURS AND TURNS MORE
NORTHWESTWARD AT THE TERMINUS TO REFLECT A MORE RAPID DISSIPATION,
OTHERWISE, THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY
SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TS YUTU IS FORECAST TO CONTINUE ON A NORTH-NORTHWESTWARD TRACK
UP TO TAU 36 THEN NORTHWESTWARD AS IT COLLAPSES DOWN TO A LOWER LAYER
OF THE STEERING STR. INCREASING VWS THEN DECREASING SST AND OHC WILL
GRADUALLY THEN RAPIDLY WEAKEN THE SYSTEM TO DISSIPATION BY TAU 48,
POSSIBLY SOONER. MODEL GUIDANCE SIGNIFICANTLY SPREADS TO OVER 200 NM
BY TAU 48, LENDING LOW CONFIDENCE IN THE JTWC TRACK FORECAST THAT
FAVORS THE WEAKER LEFT SIDE OF THE MODEL ENVELOPE.//
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