Tropical Storm YUTU Advisory Thu Oct 25

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 31W (YUTU) WARNING NR
12//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   SUPER TYPHOON (STY) 31W (YUTU), LOCATED APPROXIMATELY 109 NM
SOUTHEAST OF SAIPAN, HAS TRACKED NORTHWESTWARD AT 10 KNOTS OVER THE
PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY
SHOWS A 20 NM WIDE ROUND EYE, SURROUNDED BY SYMMETRIC DEEP
CONVECTION WITH BANDS OF EXTREMELY DEEP CONVECTION TO THE NORTH AND
SOUTH. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON
THE EYE IN THE EIR IMAGERY. COMPARING THE 36 AND 89 GHZ CHANNELS IN
A 240354Z AMSR2 MICROWAVE PASS REVEALS THE EYE IS TILTED SLIGHTLY TO
THE NORTHEAST WITH HEIGHT. THIS IS ACCOUNTED FOR IN THE INITIAL
POSITION. THE INITIAL INTENSITY OF 145 KNOTS IS BETWEEN DVORAK
CURRENT INTENSITY ESTIMATES FROM KNES AND RJTD OF T7.0 (140 KTS) AND
PGTW OF T7.5 (155 KTS). THE ENVIRONMENT REMAINS FAVORABLE WITH
MODERATE (15-20 KNOT) VERTICAL WIND SHEAR (VWS), EXCELLENT RADIAL
OUTFLOW, AND WARM (29-30 CELSIUS) SEA SURFACE TEMPERATURE. THE
CYCLONE IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF A
SUBTROPICAL RIDGE (STR) TO THE NORTHEAST.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. THE STR TO THE NORTHEAST IS EXPECTED TO CONTINUE STEERING STY
31W NORTHWESTWARD TO WEST-NORTHWESTWARD THROUGH TAU 72.
ENVIRONMENTAL CONDITIONS WILL REMAIN FAVORABLE FOR CONTINUED GRADUAL
INTENSIFICATION THROUGH TAU 24, STEADY INTENSITY THROUGH TAU 48, AND
GRADUAL WEAKENING DUE TO HIGH VWS BY TAU 72. THE NUMERICAL MODEL
TRACKERS REMAIN IN GOOD AGREEMENT THROUGH TAU 24 BEFORE OUTLIERS
START TO DEVELOP TO THE NORTH (COAMPS-GFS AND NAVGEM) AND SOUTH
(UKMET, GALWEM, AND JGSM). THE SPREAD IS 275 NM BY TAU 72, THEREFORE
UNCERTAINTY IS HIGH FOR THIS PORTION OF THE FORECAST.
   C. BEYOND TAU 72, STY 31W IS FORECASTED TO BEGIN TURNING SLOWLY
AROUND THE STR AXIS WHILE CONTINUING TO WEAKEN. IN THE EXTENDED
PERIOD, THE GUIDANCE ENVELOPE IS HUGE WITH OVER 1000 NM OF SPREAD
BETWEEN THE NORTHERN AND SOUTHERN OUTLIERS. THERE ARE THREE CLUSTERS
IN THE GUIDANCE. THE SOUTHERN CLUSTER CONSISTS OF THE UKMET, GALWEM,
AND JGSM AND PREDICTS A WESTWARD TO WEST-SOUTHWESTWARD TRACK,
PRIMARILY DUE TO A STR TO THE NORTHWEST. THE NORTHERN CLUSTER
CONSISTS OF NAVGEM AND COAMPS-GFS AND PREDICTS RECURVATURE DUE TO AN
APPROACHING MID-LATITUDE TROUGH PRIOR TO TAU 72. THE MIDDLE CLUSTER
CONSISTS OF ECMWF, GFS, HWRF, AND THE ECMWF AND GFS ENSEMBLE MEANS.
FOR THE MOST PART, THIS CLUSTER PREDICTS A SLIGHT NORTHWARD TURN BY
TAU 120 AS A SECOND MID-LATITUDE TROUGH CREATES A WEAKNESS IN THE
STR. MOST MEMBERS OF THE ECMWF ENSEMBLE SUGGEST THE MIDDLE CLUSTER
IS THE MOST PLAUSIBLE SCENARIO. THE JTWC FORECAST TRACK FOLLOWS THE
MIDDLE CLUSTER. UNCERTAINTY IS VERY HIGH FOR THE EXTENDED PORTION OF
THE JTWC FORECAST.//
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