Tropical Storm KALMAEGI Advisory 12 Σεπ.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 15W (FIFTEEN)
WARNING NR 05//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 15W (FIFTEEN), LOCATED APPROXIMATELY 403
NM NORTH OF KOROR, HAS TRACKED WESTWARD AT 23 KNOTS OVER THE PAST
SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS
BROKEN BANDS OF DEEP CONVECTION FORMING ALONG THE NORTHEASTERN AND
SOUTHERN PERIPHERIES. A RECENT 111242Z ASCAT PASS SHOWS THE LOW
LEVEL CIRCULATION CENTER (LLCC) HAS IMPROVED ORGANIZATION WITH A
WEAK ELONGATION IN THE NORTH-SOUTH AXIS BUT WIND SPEEDS IN THE
NORTHEASTERN QUADRANT HAVE INCREASED TO BETWEEN 25 TO 30 KNOTS.
WEAKER WINDS BETWEEN 10 TO 20 KNOTS PERSIST IN THE REMAINING
QUADRANTS. UPPER LEVEL ANALYSIS INDICATES TD 15W REMAINS SOUTH OF A
SUBTROPICAL RIDGE (STR) AND IS IN A WEAKLY DIVERGENT REGION,
PROVIDING MARGINAL SOUTHWESTERLY OUTFLOW. VERTICAL WIND SHEAR (VWS)
HAS BEEN SLOWLY WEAKENING, CURRENTLY AT LOW TO MODERATE LEVELS (10
TO 15 KNOTS), AS THE TRACK SPEED FOR TD 15W REMAINS BETWEEN 18 TO 23
KNOTS AND IN PHASE WITH THE UPPER LEVEL FLOW. TD 15W CONTINUES
TRACKING WESTWARD UNDER THE STEERING INFLUENCE OF THE DEEP LAYERED
REFLECTION OF THE STR LOCATED TO THE NORTH OF THE SYSTEM.
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 THE STR, BUT WILL UNDERGO A PERIOD
OF DECREASED SPEEDS AS A MIGRATORY UPPER-LEVEL TROUGH PASSES TO THE
NORTH OF THE RIDGE BETWEEN TAU 36 AND 72. FAVORABLE ENVIRONMENTAL
CONDITIONS ARE EXPECTED TO PERSIST WITH HIGH SEA SURFACE
TEMPERATURES, IMPROVING UPPER LEVEL OUTFLOW, AND DECREASING VWS
ALLOWING TD 15W TO GRADUALLY INTENSIFY AND REACHING TO TYPHOON
STRENGTH BY TAU 60. TD 15W IS FORECAST TO MAKE LANDFALL IN EASTERN
LUZON SLIGHTLY BEFORE TAU 72, LEADING TO A TEMPORARY WEAKENING TREND
IN THE LATE TAUS.
   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. AS THE SYSTEM MOVES OVER LUZON THERE WILL BE FURTHER
WEAKENING DUE TO LAND INTERACTION, BUT WILL BE SHORT LIVED. BY TAU
120 THE FAVORABLE ENVIRONMENT WILL CAUSE TD 15W TO INTENSIFY AS IT
APPROACHES THE COAST OF CHINA. AVAILABLE MODEL GUIDANCE REMAINS IN
GOOD AGREEMENT. DUE TO THE UNCERTAINTY OF INTENSITY AND TRACK SPEEDS
IN THE EXTENDED TAUS, THERE IS LOW CONFIDENCE IN THE JTWC FORECAST.//
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