Tropical Storm CHAMPI Advisory Thu Oct 15

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 25W (CHAMPI) WARNING NR
08//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 25W (CHAMPI), LOCATED APPROXIMATELY 394 NM
EAST OF SAIPAN, HAS TRACKED WEST-NORTHWESTWARD AT 11 KNOTS OVER THE
PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI)
CONTINUES TO DEPICT DEEPENED CONVECTION DISPLACED WEST OF A LOW
LEVEL CIRCULATION CENTER (LLCC). A 142345Z METOP-A MICROWAVE IMAGE
REVEALS SHALLOW SPIRAL BANDING WITH THE BULK OF THE DEEP CONVECTION
OVER THE SOUTHWESTERN QUADRANT WRAPPING INTO THE LLCC. THE INITIAL
POSITION IS BASED ON THE MSI AND AFOREMENTIONED MICROWAVE IMAGE WITH
GOOD CONFIDENCE. THE CURRENT INTENSITY OF 50 KNOT IS BASED ON THE
CURRENT STRUCTURE AND SLIGHTLY HEDGED HIGHER THAN CORRESPONDING
DVORAK INTENSITY ESTIMATES (T3.0) FROM ALL REPORTING AGENCIES. UPPER-
LEVEL ANALYSIS INDICATES THE SYSTEM IS LOCATED IN A
FAVORABLE ENVIRONMENT WITH LOW TO MODERATE EASTERLY VERTICAL WIND
SHEAR (VWS) AND STRONG DIVERGENT OUTFLOW. TS 25W IS TRACKING
WESTWARD ALONG THE SOUTHERN PERIPHERY OF THE SUB-TROPICAL RIDGE
(STR) TO THE NORTH.
3. FORECAST REASONING.
   A. NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TS CHAMPI WILL TRACK ON A WEST-NORTHWESTWARD TRAJECTORY ALONG
THE SOUTHERN PERIPHERY OF THE STEERING STR THROUGH TAU 48.
AFTERWARDS, TS 25W WILL TURN TO A MORE NORTHWESTWARD MOTION AS IT
APPROACHES THE WESTERN EXTENT OF THE STR. FAVORABLE CONDITIONS WILL
PERSIST ALLOWING A GRADUAL INTENSIFICATION AND LEADING TO A PEAK
INTENSITY OF 110 KNOTS BY TAU 72.
   C. BEYOND TAU 72, TS 25W WILL TURN POLEWARD AND ROUND THE
STEERING STR. THE CYCLONE WILL MAINTAIN INTENSITY AS DECREASING SEA
SURFACE TEMPERATURES (BELOW 27 CELSIUS) AND INCREASING VWS IS OFFSET
BY THE ENHANCED POLEWARD OUTFLOW CHANNEL. HOWEVER, AS THE SYSTEM
GAINS LATITUDE THE DETERIORATING ENVIRONMENTAL CONDITIONS WILL BEGIN
TO WEAKEN IT. DYNAMIC MODEL GUIDANCE IS IN GOOD AGREEMENT THROUGH
TAU 72. HOWEVER, DUE TO THE TIMING OF THE TURN AND SPREAD AMONG
AVAILABLE TRACKERS IN THE EXTENDED TAUS, THE JTWC TRACK CONFIDENCE
LEVEL REMAINS LOW.//
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