Tropical Storm CHAN-HOM Advisory 10月6日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 16W (CHAN-HOM) WARNING
NR 005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 16W (CHAN-HOM), LOCATED APPROXIMATELY 139 NM
SOUTHWEST OF IWO TO, JAPAN, HAS TRACKED NORTH-NORTHWESTWARD AT 04
KNOTS (KTS) OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED
(EIR) SATELLITE IMAGERY DEPICTS FORMATIVE BANDING WRAPPING INTO A
PARTIALLY-EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) WITH DEEP
CONVECTION COVERING THE SOUTHERN SEMICIRCLE. THE INITIAL POSITION IS
BASED ON THE PARTIALLY-EXPOSED NATURE OF THE LLCC AND A 051905Z
SSMIS 91 GHZ PARTIAL MICROWAVE IMAGE WHICH DEPICTS THE CONVECTIVE
BANDING WRAPPING IN FROM THE EAST WITH GOOD CONFIDENCE. THE INITIAL
INTENSITY OF 40 KTS IS HEDGED BETWEEN DVORAK CURRENT INTENSITY
ESTIMATES OF T2.5-3.0 (35-45 KTS, PGTW/RJTD) AND SLIGHTLY ABOVE THE
051740Z ADVANCED DVORAK TECHNIQUE ESTIMATE OF T2.3 (33 KTS) AND
051637Z SATCON ESTIMATE OF 34 KTS. TS 16W IS MOVING THROUGH AN
ENVIRONMENT WHICH IS FAVORABLE FOR DEVELOPMENT WITH WARM (29-30
CELSIUS) SEA SURFACE TEMPERATURE, LOW (5-10 KT) VERTICAL WIND SHEAR
(VWS), AND ESTABLISHED EQUATORWARD AND DEVELOPING POLEWARD OUTFLOW.
OF NOTE, CONVERGENT FLOW ON THE NORTHWEST PERIPHERY HAS LIMITED
DEVELOPMENT IN THAT QUADRANT. TS 16W IS TRACKING ALONG THE
SOUTHWESTERN PERIPHERY OF A SUBTROPICAL RIDGE (STR) POSITIONED TO
THE NORTHEAST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TS 16W IS FORECAST TO TRACK GENERALLY NORTHWESTWARD ALONG THE
SOUTHWESTERN PERIPHERY OF THE STEERING STR THROUGH TAU 72. DURING
THIS TIME, THE SYSTEM WILL STEADILY INTENSIFY TO A PEAK INTENSITY OF
85 KTS BY TAU 72 DUE TO CONTINUED LOW VWS AND WARM SSTS. THE
STEERING ENVIRONMENT DURING THIS TIME IS COMPLEX AS THE STEERING STR
BEGINS TO REORIENT. DUE TO UNCERTAINTY IN THE TIMING OF THE
REORIENTATION, THERE IS A SIGNIFICANT AMOUNT OF SPREAD IN THE
NUMERICAL MODEL SOLUTIONS WITH THE LARGEST ACROSS-TRACK SPREAD (248
NM) OCCURRING NEAR TAU 72. BASED ON THIS SPREAD, THERE IS ONLY FAIR
CONFIDENCE IN THE INITIAL PORTION OF THE JTWC FORECAST TRACK.
   C. AFTER TAU 72, THE SYSTEM WILL TRACK NORTHWARD, ROUNDING THE
STR AXIS AND TURNING TO A GENERALLY NORTHEASTWARD TRACK TOWARDS
KYUSHU. DUE TO HIGH (>20 KTS) VWS, TS 16W IS EXPECTED TO GRADUALLY
FOR THE REMAINDER OF THE FORECAST PERIOD TO AN INTENSITY OF 50 KTS
BY TAU 120. ADDITIONALLY, TS 16W WILL BEGIN TO INTERACT WITH THE
BAROCLINIC ZONE DURING THIS TIME AND COMMENCE EXTRATROPICAL
TRANSITION. IN THE EXTENDED RANGE, THE ALONG-TRACK SPREAD HAS
INCREASED FOR TAU 120 DUE TO THE UNCERTAINTY IN THE TIMING OF THE
RECURVE. HOWEVER, THE NAVGEM SOLUTION HAS COME INTO BETTER AGREEMENT
WITH THE OTHER MODEL SOLUTIONS AND NOW DEPICTS THE RECURVE SCENARIO.
DUE TO THE HIGH DEGREE OF DIVERGENCE IN MODEL SOLUTIONS, THERE IS
POOR CONFIDENCE IN THE REMAINDER OF THE JTWC FORECAST TRACK.//
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