WDPN32 PGTW 091500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 24W (NARI) WARNING NR 04// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM 24W (NARI), LOCATED APPROXIMATELY 453 NM EAST OF MANILA, PHILIPPINES, HAS TRACKED WESTWARD AT 07 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS PERSISTENT DEEP CENTRAL CONVECTION OVER THE PAST SIX HOURS OVER A TIGHTLY WRAPPED LOW LEVEL CIRCULATION CENTER (LLCC). THE CURRENT INTENSITY OF 35 KNOTS IS BASED ON DVORAK ESTIMATES FROM PGTW AND KNES, WITH AN OLDER 090357Z OSCAT PASS INDICATING WIND SPEEDS WERE AROUND 30 TO 35 KNOTS AT THAT TIME. GIVEN THE STEADY INCREASE IN CENTRAL CONVECTION FROM THE 0357Z TIME, THE CURRENT INTENSITY OF 35 KNOTS SEEMS APPROPRIATE. UPPER-LEVEL ANALYSIS INDICATES A MARGINALLY-FAVORABLE ENVIRONMENT WITH DIFFLUENT EASTERLY FLOW AND WEAK (05 TO 10 KNOTS) VERTICAL WIND SHEAR (VWS). TS 24W IS TRACKING ALONG THE SOUTHERN PERIPHERY OF THE LOW- TO MID-LEVEL SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTH. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS 24W IS FORECAST TO TRACK GENERALLY WESTWARD THROUGH TAU 72 UNDER THE STEERING INFLUENCE OF THE AFOREMENTIONED STR. THE DYNAMIC MODEL GUIDANCE IS IN EXCELLENT AGREEMENT ON A GENERALLY WESTWARD TRACK ACROSS LUZON. TS 24W IS FORECAST TO INTENSIFY TO A PEAK OF 70 KNOTS AS IT APPROACHES LUZON UNDER FAVORABLE CONDITIONS OF GOOD OUTFLOW, LOW VWS AND WARM SEA SURFACE TEMPERATURES. C. IN THE EXTENDED PERIOD, TS 24W WILL CONTINUE TO TRACK WEST UNDER THE PERSISTENT STEERING INFLUENCE OF THE STR. AS IT TRACKS ACROSS THE MOUNTAINOUS TERRAIN OF CENTRAL LUZON, TS 24W WILL WEAKEN UNTIL IT TRACKS INTO THE SOUTH CHINA SEA AND THEN WILL RE-INTENSIFY TO TYPHOON STRENGTH BY TAU 120. BASED ON THE TIGHT AGREEMENT OF DYNAMIC MODELS, THERE IS HIGH CONFIDENCE IN THE JTWC FORECAST TRACK, WHICH IS POSITIONED SLIGHTLY FASTER THAN THE MULTI-MODEL CONSENSUS.// NNNN
Posted on: Wed, 09 Oct 2013 20:11:04 +0000
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