Tropical Storm YUTU Advisory Tue Oct 23

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 31W (YUTU)
WARNING NR 04//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 31W (YUTU), LOCATED APPROXIMATELY 638 NM
EAST-SOUTHEAST OF ANDERSEN AFB, GUAM, HAS TRACKED NORTHWESTWARD AT
12 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY SHOWS DEEP CONVECTION AROUND THE LOW LEVEL CIRCULATION
CENTER (LLCC) ALONG WITH AN EXPANDING CLOUD FIELD. THE INITIAL
POSITION IS PLACED WITH FAIR CONFIDENCE AND IS BASED ON A 220544Z
HMS 89GHZ MICROWAVE IMAGE WHICH SHOWS THE DEEPEST CONVECTION IS
LOCATED TO THE EAST AND THE SOUTH OF THE LLCC. THE INITIAL
INTENSITY OF 40 KNOTS IS HEDGED BETWEEN DVORAK INTENSITY ESTIMATES
OF T2.5 (35 KNOTS) FROM PGTW, KNES, AND RJTD AND A 220542Z SATCON
ESTIMATE OF 44 KNOTS AND AN ADT ESTIMATE OF T2.9 (43 KNOTS).
ENVIRONMENTAL ANALYSIS SHOWS THAT TS 31W IS EXPERIENCING FAVORABLE
VERTICAL WIND SHEAR (5 TO 10 KNOTS) AND HAS EXCELLENT RADIAL
OUTFLOW. SEA SURFACE TEMPERATURES REMAIN WARM (30 TO 32 DEGREES
CELSIUS) AND WILL ALLOW FOR CONTINUED DEVELOPMENT. TS 31W IS
TRACKING NORTHWESTWARD ALONG THE SOUTHWESTERN PERIPHERY OF
THE SUBTROPICAL RIDGE (STR) LOCATED TO THE NORTHEAST.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. THROUGH TAU 72, TS 31W WILL CONTINUE TRACKING TOWARD THE
NORTHWEST AROUND THE AFOREMENTIONED STR, WITH ENVIRONMENTAL
CONDITIONS REMAINING FAVORABLE FOR INTENSIFICATION. MODEL GUIDANCE
IS INDICATING RAPID INTENSIFICATION WHICH SEEMS LIKELY BASED ON
FAVORABLE VERTICAL WIND SHEAR AND SEA SURFACE TEMPERATURES ALONG
WITH EXCELLENT RADIAL OUTFLOW. BY TAU 24, TS 31W WILL REACH AN
INTENSITY OF 70 KNOTS. ADDITIONAL INTENSIFICATION TO 110 KNOTS WILL
OCCUR BY TAU 72. DYNAMIC MODEL GUIDANCE CONTINUES TO SHOW A
NORTHWESTWARD TRACK THROUGH TAU 72. ADDITIONALLY, MODEL GUIDANCE
HAS COME INTO BETTER AGREEMENT WITH A SMALLER SPREAD THROUGH TAU
72. THEREFORE, THERE IS HIGH CONFIDENCE IN THIS PORTION OF THE JTWC
FORECAST TRACK.
   C. BEYOND TAU 72, A WEAKNESS IN THE STR INDUCED BY AN
UPPER-TROPOSPHERIC TROUGH WILL ALLOW FOR A SLIGHTLY MORE NORTHWARD
TRACK. ENVIRONMENTAL CONDITIONS WILL REMAIN FAVORABLE FOR CONTINUED
INTENSIFICATION WITH LOW VERTICAL WIND SHEAR AND HIGH OCEAN HEAT
CONTENT. DYNAMIC MODEL GUIDANCE REMAINS IN POOR AGREEMENT BEYOND
TAU 72. AFUM AND ECMWF INDICATE A MORE WESTWARD TRACK WHILE GFS AND
NAVGEM INDICATE A CONTINUED NORTHWESTWARD TRACK. THE GFS AND ECMWF
ENSEMBLE TRACKERS ARE AT THE EDGES OF THE MODEL ENVELOPE WITH A
SPREAD OF 540NM BETWEEN THEM BY TAU 120. THE GFS ENSEMBLE FAVORS A
NORTHWARD TRACK WHILE THE ECMWF ENSEMBLE FAVORS A WESTWARD TRACK.
DUE TO THE WIDE SPREAD IN  MODEL GUIDANCE BY TAU 120 THERE IS LOW
CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST TRACK.//
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