Tropical Storm KOPPU Advisory 15 Οκτ.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 24W (KOPPU) WARNING NR
08//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 24W (KOPPU), LOCATED APPROXIMATELY 685 NM
EAST OF MANILA, PHILIPPINES, HAS TRACKED WEST-SOUTHWESTWARD AT 10
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR)
SATELLITE IMAGERY DEPICTS PERSISTENT DEEP CONVECTION DISPLACED
SLIGHTLY WEST OF A LOW LEVEL CIRCULATION CENTER (LLCC). A 141750Z
AMSU-B MICROWAVE IMAGE REVEALS DEFINED SHALLOW SPIRAL BANDING
WRAPPING INTO THE LLCC WITH THE BULK OF THE DEEP CONVECTION OVER THE
SOUTHWESTERN QUADRANT. THE CURRENT POSITION IS BASED ON THE EIR LOOP
AND SATELLITE FIXES FROM PGTW AND RJTD WITH GOOD CONFIDENCE. THE
CURRENT INTENSITY HAS BEEN HELD AT 45 KNOTS BASED ON AN OVERALL
ASSESSMENT OF DVORAK INTENSITY ESTIMATES FROM ALL REPORTING
AGENCIES. UPPER LEVEL ANALYSIS INDICATES A MARGINALLY-FAVORABLE
ENVIRONMENT WITH AN ANTICYCLONE JUST NORTH OF THE SYSTEM, PROVIDING
STRONG DIVERGENT OUTFLOW. HOWEVER, MODERATE (20-25 KNOT)
NORTHEASTERLY VERTICAL WIND SHEAR (VWS) IS PREVENTING VERTICAL
ALIGNMENT AND SUBSEQUENT INTENSIFICATION. SEA SURFACE TEMPERATURES
(SSTS) ARE NEAR 30 CELSIUS. TS 24W IS TRACKING ALONG THE SOUTHERN
PERIPHERY OF THE DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO THE NORTH.
3. FORECAST REASONING.
   A. NO CHANGE TO FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC
REASONING MESSAGE.
   B. TS KOPPU WILL CONTINUE TO TRACK WESTWARD THROUGH TAU 72 ALONG
THE SOUTHERN PERIPHERY OF THE STEERING STR. EXPECT SLOW
INTENSIFICATION OVER THE NEXT 48 HOURS AS VWS REMAINS MODERATE;
HINDERING DEVELOPMENT AND PREVENTING VERTICAL ALIGNMENT. BEYOND TAU
48, VWS WILL RELAX AS THE UPPER LEVEL WIND FLOW BECOMES MORE IN-
PHASE WITH THE STORM MOTION. ADDITIONALLY, SSTS WILL INCREASE ABOVE
30 CELSIUS. THESE ENVIRONMENTAL CONDITIONS WILL SUPPORT A PERIOD OF
RAPID INTENSIFICATION AS THE STORM APPROACHES LUZON.
   C. IN THE EXTENDED FORECAST, TS 24W WILL SLOW AND TURN MORE
NORTHWESTWARD AS THE CYCLONE REACHES THE WESTERN EXTENT OF THE
STEERING STR. TS KOPPU WILL CONTINUE TO INTENSIFY UNTIL IT BEGINS TO
INTERACT WITH THE MOUNTAINOUS TERRAIN IN LUZON. THE STORM WILL PASS
OVER THE NORTHERN LUZON AS IT CONTINUES TO TURN POLEWARD AND ROUND
THE WESTERN PERIPHERY OF THE STR. DYNAMIC MODEL GUIDANCE IS OVERALL
IN GOOD AGREEMENT TROUGH TAU 72. HOWEVER, DUE TO SIGNIFICANT
DIFFERENCE AMONG AVAILABLE TRACKERS IN THE EXTENDED TAUS, THERE IS
LOW CONFIDENCE IN THE JTWC TRACK.//
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