Tropical Storm YUTU Advisory Wed Oct 24

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 31W (YUTU) WARNING NR 08//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 31W (YUTU), LOCATED APPROXIMATELY 269 NM NORTH-
NORTHWEST OF CHUUK, HAS TRACKED WEST-NORTHWESTWARD AT 10 KNOTS OVER
THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE
IMAGERY SHOWS DEEP CONVECTION AROUND THE LOW LEVEL CIRCULATION
CENTER (LLCC) WITH A PARTICULARLY LARGE CELL JUST NORTH OF THE LLCC.
THE EIR IMAGERY ALSO REVEALS EXCELLENT RADIAL OUTFLOW ALOFT,
PARTICULARLY POLEWARD. THE INITIAL POSITION IS PLACED WITH GOOD
CONFIDENCE BASED ON A LOW BRIGHTNESS TEMPERATURE AREA IN A 230457Z
SSMI 37 GHZ MICROWAVE IMAGE. THE INITIAL INTENSITY OF 75 KNOTS IS
CONSISTENT WITH PGTW AND RJTD DVORAK CURRENT INTENSITY ESTIMATES OF
T4.5 (77 KTS). TY 31W IS IN AN AREA OF LOW (10-15 KNOT) VERTICAL
WIND SHEAR (VWS), GOOD EQUATORWARD OUTFLOW, EXCELLENT POLEWARD
OUTFLOW, AND WARM (29-30 CELSIUS) SEA SURFACE TEMPERATURE. THE
CYCLONE IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF A
SUBTROPICAL RIDGE (STR).
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. THROUGH TAU 72, TY 31W IS FORECAST TO CONTINUE TRACKING
NORTHWESTWARD TO WEST-NORTHWESTWARD. CONDITIONS WILL REMAIN
FAVORABLE FOR RAPID INTENSIFICATION THROUGH TAU 24 AND CONTINUED,
MORE GRADUAL INTENSIFICATION THROUGH TAU 72. EVIDENCE OF A
BIFURCATION IN THE NUMERICAL MODEL GUIDANCE BECOMES APPARENT BY TAU
24 WITH GFS, THE GFS ENSEMBLE MEAN, AND COAMPS-GFS FAVORING A MORE
NORTHERLY COMPONENT TO THE TRACK AND RECURVATURE BEGINNING AROUND
TAU 72, WHILE THE REMAINING MEMBERS PREDICT A MORE WEST-
NORTHWESTWARD TRACK THROUGH TAU 72. THE JTWC FORECAST TRACK IS
CONSISTENT WITH THE WEST-NORTHWESTWARD MODELS BECAUSE THE MEMBERS IN
THAT CLUSTER INCLUDE OUR TRADITIONALLY MORE RELIABLE MEMBERS.
UNCERTAINTY IS HIGH FOR THIS PORTION OF THE JTWC FORECAST TRACK DUE
TO THE BIFURCATION IN THE GUIDANCE.
   C. BEYOND TAU 72, TY 31W IS FORECAST TO CONTINUE TRACKING WEST-
NORTHWESTWARD AND INTENSIFY TO 135 KNOTS BY TAU 96. AFTER TAU 96,
HIGH VWS IS ANTICIPATED TO CAUSE SLIGHT WEAKENING AS RECURVATURE
BEGINS. DYNAMIC MODEL GUIDANCE DIVERGES FURTHER FOR THIS PORTION OF
THE FORECAST AS MEMBERS IN THE WEST-NORTHWESTWARD GROUP SPLIT AGAIN.
UKMET, GALWEM, AND JGSM (CUTS OFF AT TAU 72) DEPICT A WEST-
SOUTHWESTWARD TURN WHILE THE NAVGEM, ECMWF ENSEMBLE MEAN, AND ECMWF
PREDICT RECURVATURE TO BEGIN AROUND TAU 120. THE JTWC TRACK FORECAST
IS PLACED NEAR THE LATE RECURVATURE GROUP. UNCERTAINTY REMAINS HIGH
FOR THIS PORTION OF THE FORECAST, WITH SPREAD APPROACHING 900 NM BY
TAU 120.//
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