Tropical Storm MANGKHUT Advisory Wed Sep 12

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 26W (MANGKHUT) WARNING
NR 19//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   SUPER TYPHOON (STY) 26W (MANGKHUT), LOCATED APPROXIMATELY 254 NM
NORTH OF YAP, FSM, HAS TRACKED WESTWARD AT 12 KNOTS OVER THE PAST SIX
HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY SHOWS A SYMMETRIC
AND HIGHLY CONSOLIDATED SYSTEM WITH COMPACT FEEDER BANDS SPIRALING
TIGHTLY INTO A SHARPLY-OUTLINED 23-NM EYE. THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON THE EYE FEATURE. THE INITIAL
INTENSITY OF 140 KNOTS IS BASED ON EQUIVALENT DVORAK ESTIMATES OF
T7.0 FROM PGTW AND RJTD. UPPER LEVEL ANALYSIS INDICATES STY 26W IS IN
AN AREA OF LOW VERTICAL WIND SHEAR AND EXCELLENT RADIAL OUTFLOW WITH
A STRONG EASTWARD CHANNEL INTO A TUTT CELL. ADDITIONALLY, ALONG TRACK
SEA SURFACE TEMPERATURES IN THE PHILIPPINE SEA AT 28-30 CELSIUS ARE
HIGHLY CONDUCIVE. THE CYCLONE IS TRACKING ALONG THE SOUTHERN
PERIPHERY OF A DEEP-LAYERED EAST-WEST ORIENTED SUBTROPICAL RIDGE
(STR) TO THE NORTH.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY FROM THE
PREVIOUS WARNING.
   B. STY 26W WILL TRACK MORE WEST-NORTHWESTWARD AFTER TAU 12 AS THE
STR WEAKENS IN RESPONSE TO AN APPROACHING MIDLATITUDE TROUGH. THE
FAVORABLE ENVIRONMENTAL CONDITIONS WILL PERSIST AND SUPPORT
CONTINUED INTENSIFICATION TO A PEAK OF 150 KNOTS BY TAU 36.
AFTERWARD, REDUCED OUTFLOW AS THE SYSTEM MOVES AWAY FROM THE TUTT
CELL WILL SLIGHTLY WEAKEN THE SYSTEM TO 135 KNOTS BY TAU 72 AS IT
APPROACHES NORTHERN LUZON. CONFIDENCE IN THIS PORTION OF THE JTWC
FORECAST TRACK REMAINS HIGH BASED ON THE TIGHT GROUPING IN THE
NUMERICAL MODEL GUIDANCE.
   C. AFTER TAU 72, STY MANGKHUT WILL CONTINUE ON A MORE
NORTHWESTWARD TRAJECTORY UNDER THE STEERING INFLUENCE OF THE WEAKENED
STR. THE CYCLONE WILL ENTER THE LUZON STRAIT AND PASS BETWEEN TAIWAN
AND THE PHILIPPINES INTO THE SOUTH CHINA SEA. INTERACTION WITH LAND
AND DIMINISHING OUTFLOW WILL PRIMARILY BE RESPONSIBLE FOR ITS GRADUAL
DECAY. HOWEVER, BY TAU 120, THE SYSTEM WILL STILL BE A SOLID 80-KNOT
TYPHOON WHEN IT MAKES LANDFALL TO THE WEST OF HONG KONG. THE TRACK
GUIDANCE REMAINS IN TIGHT AGREEMENT WITH CTCX AS THE LONE
LEFT-OF-TRACK OUTLIER. THERE IS ALSO HIGH CONFIDENCE IN THE EXTENDED
JTWC FORECAST TRACK THAT IS LAID JUST RIGHT OF MODEL CONSENSUS TO
OFFSET THE UNLIKELY CTCX SOLUTION.//
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