Tropical Storm KALMAEGI Advisory Thu Sep 11

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 15W (FIFTEEN)
WARNING NR 04//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 15W (FIFTEEN), LOCATED APPROXIMATELY 267
NM NORTH-NORTHWEST OF YAP, HAS TRACKED WESTWARD AT 18 KNOTS OVER THE
PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS
A SLOWLY-CONSOLIDATING LOW-LEVEL CIRCULATION CENTER WITH A BROAD
AREA OF DEEP CONVECTION. AN 111243Z METOP-B MICROWAVE IMAGE REVEALS
BROKEN CONVECTIVE BANDING OVER THE NORTHERN AND SOUTHERN PERIPHERY
WRAPPING INTO THE CENTER. AN 111244Z ASCAT PASS SHOWS A 15 TO 20
KNOT CIRCULATION WITH STRONGER (30 TO 35 KNOT) WINDS OVER THE
NORTHERN SEMI-CIRCLE. THE CURRENT POSITION IS BASED ON THE ASCAT
IMAGE WITH GOOD CONFIDENCE. THE INITIAL INTENSITY IS REMAINED AT 25
KNOTS BASED ON AN OVERALL ASSESSMENT OF DVORAK INTENSITY ESTIMATES
FROM PGTW AND KNES. UPPER-LEVEL ANALYSIS INDICATES THE SYSTEM IS
LOCATED IN AN AREA OF MODERATE (15 TO 20 KTS) VERTICAL WIND SHEAR
(VWS) OFFSET BY EXCELLENT EQUATORWARD OUTFLOW. TD 15W IS CURRENTLY
TRACKING WESTWARD UNDER THE STEERING INFLUENCE OF THE SUBTROPICAL
RIDGE (STR) POSITIONED TO THE NORTHEAST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TD 15W IS FORECAST TO TRACK WESTWARD TO WEST-NORTHWESTWARD
UNDER THE STEERING INFLUENCE OF A MODIFYING STR DUE TO A MIGRATORY
UPPER-LEVEL TROUGH PASSES TO THE NORTH. FAVORABLE ENVIRONMENT
CONDITIONS ARE EXPECTED TO PERSIST ALLOWING TD 15W TO GRADUALLY
INTENSIFY AND REACHING TO TYPHOON STRENGTH BY TAU 72.
   C. TD 15W IS EXPECTED TO MAINTAIN A WEST-NORTHWESTWARD TRACK
THROUGH THE REMAINDER OF THE FORECAST PERIOD AS THE STR REBUILDS TO
THE NORTH. AVAILABLE MODEL GUIDANCE HAS IMPROVED OVER THE PAST SIX
HOURS AND IS OVERALL IN BETTER AGREEMENT. HOWEVER, DUE TO THE
UNCERTAINTY OF INTENSITY AND TRACK SPEEDS IN THE EXTENDED TAUS,
THERE IS LOW CONFIDENCE IN THE JTWC FORECAST WHICH IS POSITIONED
CLOSE TO MULTI-MODEL CONSENSUS.//
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