WDPN31 PGTW 120300
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 21W (NEPARTAK)// 
WARNING NR 15//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
    A. TROPICAL STORM (TS) NEPARTAK MAINTAINED TS INTENSITY DESPITE
THE INCREASING VERTICAL WIND SHEAR ALOFT AS IT APPROACHES THE STRONG
UPPER LEVEL WESTERLIES TO THE NORTH. ANIMATED WATER VAPOR IMAGERY
SHOWS DEEP CENTRAL CONVECTION AND GOOD POLEWARD OUTFLOW PERSIST
OVER THE SYSTEM. THE CURRENT INTENSITY IS BASED ON THE DVORAK FIXES
FROM PGTW AND KNES OF T3.5. THE CURRENT POSITION IS BASED ON ANIMATED
MULTISPECTRAL IMAGERY.
3. FORECAST REASONING.
    A. THE FORECAST PHILOSOPHY HAS NOT CHANGED SIGNIFICANTLY SINCE
THE PREVIOUS BULLETIN.
    B. TS 21W IS EXPECTED TO CONTINUE TRACKING POLEWARD AND MAINTAIN
A 55-KNOT INTENSITY AS IT APPROACHES THE JET STREAM TO THE NORTH THAT
IS MOMENTARILY PROVIDING POLEWARD OUTFLOW. IT WILL BEGIN TO ACCELERATE
INTO THE BAROCLINIC ZONE AFTER TAU 24, AND BECOME FULLY EXTRA-TROPICAL
BY TAU 48. TS NEPARTAK IS EXPECTED TO GRADUALLY WEAKEN AFTER THE
STRONG VWS FINALLY TAKES ITS TOLL ON THE SYSTEM BY TAU 36. THE AVAI-
LABLE NUMERIC GUIDANCE IS IN TIGHT AGREEMENT WITH THE WBAR AS THE SOLE
AND FAST OUTLIER TO THE RIGHT.//
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