WDPN33 PGTW 132100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 11W (NANGKA) WARNING NR 42//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 11W (NANGKA), LOCATED APPROXIMATELY 305 NM WEST-
SOUTHWEST OF IWO TO, HAS TRACKED NORTH-NORTHWESTWARD AT 08 KNOTS 
OVER THE PAST SIX HOURS. ANIMATED EIR SATELLITE IMAGERY DEPICTS A 
SMALL 6 NM EYE WITH THINNING DEEP CONVECTION ON THE NORTHERN SEMI-
CIRCLE. THE SYSTEM HAS UNDERGONE AN ERC THAT IS RESPONSIBLE FOR THE 
WEAKENING PERIOD. THE CURRENT POSITION IS BASED ON THE 
AFOREMENTIONED EYE FEATURE WITH HIGH CONFIDENCE. THE CURRENT 
INTENSITY OF 95 KNOTS IS BASED ON AN OVERALL ASSESSMENT OF DVORAK 
CURRENT INTENSITY ESTIMATES FROM ALL REPORTING AGENCIES. UPPER-LEVEL 
ANALYSIS INDICATES THE SYSTEM IS LOCATED IN AN AREA OF LOW TO 
MODERATE (10 TO 15 KNOT) VWS WITH RADIAL OUTFLOW, SUSTAINING THE 
DEEP CONVECTION. THE CYCLONE IS TRACKING ALONG THE SOUTHWESTERN SIDE 
OF THE STEERING STR.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE 
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY 11W WILL CONTINUE TO TRACK POLEWARD AS THE STEERING STR 
BACKS TO THE EAST. BY TAU 48, THE STEERING STR IS EXPECTED TO 
REBUILD, FORCING TY NANGKA WEST-NORTHWESTWARD. FAVORABLE CONDITIONS 
WILL PERSIST IN THE NEAR TERM; HOWEVER, THE NORTHERN SEMI-CIRCLE 
WILL BE IMPACTED BY THE HIGH PRESSURE TO THE NORTH. THEREFORE, TY 
NANGKA IS EXPECTED TO STEADILY INTENSIFY OVER THE NEXT 48 HOURS. 
AFTERWARD INCREASING VWS AND DECREASING ENVIRONMENTAL CONDITIONS 
WILL BEGIN TO WEAKEN THE SYSTEM AS IT APPROACHES THE SOUTHERN COAST 
OF JAPAN.
   C. BY TAU 72, TY NANGKA IS EXPECTED TO TRACK OVER THE SOUTHERN 
ISLANDS OF JAPAN. TY 11W WILL ROUND THE RIDGE AXIS AND TRACK 
NORTHEASTWARD ALONG THE NORTHWESTERN EDGE OF THE STEERING STR. 
AVAILABLE MODEL GUIDANCE HAS SLIGHTLY IMPROVED OVER THE PAST SIX 
HOURS, BUT REMAINS A SIGNIFICANT SPREAD AT TAU 72. DUE TO THE 
UNCERTAINTY IN THE EXTENT OF THE STR AND DIFFERENCES IN THE TRACK 
SPEEDS, THE OVERALL JTWC FORECAST REMAINS LOW.//
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