Tropical Storm MANGKHUT Advisory Thu Sep 13

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 26W (MANGKHUT) WARNING
NR 22//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   SUPER TYPHOON (STY) 26W (MANGKHUT), LOCATED APPROXIMATELY 826 NM
EAST OF MANILA, PHILIPPINES, HAS TRACKED WESTWARD AT 10 KNOTS OVER
THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS A
SYMMETRIC AND HIGHLY CONSOLIDATED SYSTEM WITH DEEP COMPACT FEEDER
BANDS SPIRALING TIGHTLY INTO A SHARPLY-OUTLINED 30-NM EYE. THE
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE EYE
FEATURE WITH MINOR TILT ADJUSTMENT AS EVIDENCED ON A MICROWAVE EYE
FEATURE IN THE 120545Z 37 GHZ SSMI IMAGE. THE INITIAL INTENSITY OF
150 KNOTS IS BASED ON THE HIGHER END OF DVORAK ESTIMATES OF T7.0/140
KTS FROM RJTD AND T7.5/155 KTS FROM PGTW. 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. ALONG-TRACK SEA SURFACE TEMPERATURES IN THE PHILIPPINE SEA AT
28-30 CELSIUS ARE ALSO 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 TOWARD THE NORTHERN
TIP OF LUZON AS THE STR REORIENTS IN RESPONSE TO AN APPROACHING
MIDLATITUDE TROUGH. THE EXCEPTIONALLY FAVORABLE ENVIRONMENTAL
CONDITIONS WILL PERSIST AND SUSTAIN THE CURRENT INTENSITY UP TO TAU
12. AFTERWARD, DIMINISHING EASTWARD OUTFLOW AS THE SYSTEM MOVES AWAY
FROM THE TUTT CELL AND ANTICIPATED INTERACTION WITH LUZON WILL SLOWLY
WEAKEN THE SYSTEM TO 120 KNOTS BY TAU 72 AS IT ENTERS THE SOUTH CHINA
SEA (SCS). INTENSITY FORECASTS REMAIN HIGHER THAN MODEL GUIDANCE,
WHICH HAS PROVEN EFFECTIVE THROUGHOUT THE CURRENT LIFESPAN OF STY
26W. 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 NORTHWESTWARD
TRAJECTORY UNDER THE STEERING INFLUENCE OF THE STR. THE CYCLONE WILL
TRACK ACROSS THE SCS TOWARD HONG KONG. DIMINISHING OUTFLOW AND
INTERACTION WITH LAND WILL PRIMARILY BE RESPONSIBLE FOR ITS GRADUAL
THEN RAPID DECAY. THE SYSTEM WILL MAKE LANDFALL SOUTHWEST OF HONG
KONG AROUND TAU 102 AT 90 KNOTS THEN WILL BE REDUCED TO A 50-KNOT
SYSTEM BY TAU 120 AS IT TRACKS FURTHER INLAND. 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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