Tropical Storm HALONG Advisory dom, 03-11

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 24W (TWENTYFOUR)
WARNING NR 01//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 24W (TWENTYFOUR), LOCATED APPROXIMATELY
713 NM EAST OF ANDERSEN AFB, GUAM, HAS TRACKED NORTHWESTWARD AT 08 KNOTS
OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY
DEPICTS A LARGE AREA OF ASYMMETRIC DEEP CONVECTION LOCATED OVER AN
OBSCURED, ELONGATED LOW-LEVEL CIRCULATION CENTER (LLCC). A 021031Z MHS
89GHZ MICROWAVE IMAGE DEPICTS A PARTIALLY-EXPOSED, BROAD LLCC WITH THE
BULK OF THE DEEP CONVECTION DISPLACED OVER THE EASTERN SEMICIRCLE. A
021112Z ASCAT-C IMAGE INDICATES THAT THE WINDFIELD HAS STRENGTHENED
QUICKLY AND FORMED INTO A CLOSED CIRCULATION WITH A LARGE SWATH OF
30 KNOT WINDS OVER THE EASTERN SEMICIRCLE AND AN ISOLATED POCKET OF
35-40 KNOT WINDS OVER THE SOUTHEAST QUADRANT. DUE TO THE BROAD LLCC,
THERE IS FAIR CONFIDENCE IN THE CURRENT POSITION AND TRACK MOTION. THE
CURRENT INTENSITY IS ASSESSED AT 30 KNOTS BASED ON AN OVERALL EVALUATION
OF THE WINDFIELD. UPPER-LEVEL ANALYSIS REVEALS A FAVORABLE ENVIRONMENT
WITH NEAR-RADIAL OUTFLOW AND LOW VERTICAL WIND SHEAR. ADDITIONALLY, SST
VALUES OF 29-30C ARE CONDUCIVE FOR DEVELOPMENT. TD 24W IS TRACKING ALONG
THE SOUTHWESTERN PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR).
3. FORECAST REASONING.
   A. THIS IS THE FIRST PROGNOSTIC REASONING MESSAGE AND SETS THE
FORECAST PHILOSOPHY.
   B. TD 24W IS FORECAST TO TRACK NORTHWESTWARD TO NORTH-NORTHWESTWARD
THROUGH TAU 72 AS IT TRACKS ALONG THE WESTERN PERIPHERY OF THE STR AND
APPROACHES THE STR AXIS. THE SYSTEM WILL INTENSIFY UNDER FAVORABLE
CONDITIONS TO A PEAK OF 105 KNOTS WITH INCREASING POTENTIAL FOR RAPID
INTENSIFICATION AFTER TAU 48 DUE TO ENHANCED POLEWARD OUTFLOW INTO THE
MIDLATITUDE WESTERLIES.
   C. IN THE EXTENDED PERIOD, TD 24W WILL RECURVE NORTHEASTWARD AND IS
FORECAST TO BEGIN EXTRA-TROPICAL TRANSITION (ETT) AS IT INTERACTS WITH
THE MIDLATITUDE WESTERLIES. THE SYSTEM SHOULD COMPLETE ETT BY TAU 120
AS IT GAINS FRONTAL CHARACTERISTICS AND BECOMES EMBEDDED WITHIN THE
MIDLATITUDE WESTERLIES. TD 24W WILL WEAKEN RAPIDLY DUE TO INCREASING
VERTICAL WIND SHEAR AND COOLER SST BY TAU 120. DUE TO THE BROAD NATURE
OF THE LLCC AND LARGE SPREAD IN SOLUTIONS IN THE EXTENDED PERIOD, THERE
IS OVERALL LOW CONFIDENCE IN THE JTWC FORECAST TRACK.//
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