WDPN33 PGTW 141500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 11W (NANGKA) WARNING NR 45//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 11W (NANGKA), LOCATED APPROXIMATELY 637 NM SOUTH-
SOUTHEAST OF IWAKUNI, JAPAN, HAS TRACKED NORTHWARD AT 07 KNOTS
OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE 
IMAGERY SHOWS A 10NM EYE HAS RE-EMERGED; HOWEVER, A STRUGGLING 
CONVECTIVE SIGNATURE CONTINUES DUE TO DRY AIR WRAPPING INTO THE 
CENTER FROM THE NORTHERN AND WESTERN PERIPHERIES. A 140953Z SSMIS 
91GHZ MICROWAVE IMAGE DEPICTS A 50 NM MICROWAVE EYE FEATURE WITH 
LIMITED CONVECTION LOCATED ALONG THE NORTHERN EYEWALL AND WITHIN 
BANDING ALONG THE EASTERN PERIPHERY. THE CURRENT POSITION IS BASED 
ON THE EYE FEATURE IN THE EIR LOOP WITH HIGH CONFIDENCE. THE INITIAL 
INTENSITY IS HELD AT 90 KNOTS BASED ON AN UNCHANGED CONVECTIVE 
STRUCTURE AND SUPPORTED BY CONSENSUS DVORAK INTENSITY ESTIMATES OF 
T5.0 (90 KNOTS) FROM ALL AGENCIES. TY NANGKA IS LOCATED IN A 
MARGINALLY FAVORABLE ENVIRONMENT WITH LOW TO MODERATE (10-15 KNOT) 
VERTICAL WIND SHEAR (VWS), EXCELLENT EQUATORWARD OUTFLOW ALOFT, AND 
SEA SURFACE TEMPERATURES ABOVE 28 CELSIUS; HOWEVER, DRY AIR AND 
SUBSIDENCE TO THE NORTH AND WEST ARE INHIBITING CONVECTIVE 
DEVELOPMENT. TY 11W IS TRACKING ALONG THE WESTERN PERIPHERY OF THE 
DEEP LAYERED SUB-TROPICAL RIDGE (STR) TO THE EAST.
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 ALONG THE WESTERN 
PERIPHERY OF THE STEERING STR. BY TAU 24, THIS STR IS EXPECTED TO 
REBUILD, FORCING TY NANGKA ON A WEST-NORTHWESTWARD TRAJECTORY. 
ENVIRONMENTAL CONDITIONS WILL REMAIN MOSTLY UNCHANGED; HOWEVER, THE 
DRY AIR AND SUBSIDENCE ALONG THE NORTHERN SIDE OF THE SYSTEM WILL 
PREVENT AN INCREASED INTENSIFICATION RATE. BEYOND TAU 48, AS THE 
SYSTEM GAINS LATITUDE, IT WILL LOSE THE EXCELLENT EQUATORWARD 
OUTFLOW CHANNEL. IN ADDITION, INCREASING VWS, LOW OCEAN HEAT 
CONTENT, AND LAND INTERACTION WILL BEGIN TO WEAKEN THE CYCLONE AS IT 
APPROACHES AND MAKES LANDFALL ALONG THE SOUTHERN COAST OF JAPAN.
   C. BEYOND TAU 72, TY NANGKA WILL TRACK OVER THE SOUTHERN ISLANDS 
OF JAPAN AND ROUND THE STR AXIS, TURNING TO A NORTHEASTWARD 
TRAJECTORY. TY 11W WILL CONTINUE TO WEAKEN AS VWS RAPIDLY INCREASES 
AND SEA SURFACE TEMPERATURE DECREASES, LEADING TO ITS DISSIPATION BY 
THE END OF THE FORECAST PERIOD. DYNAMIC MODEL GUIDANCE HAS IMPROVED 
REGARDING THE TIMING OF THE RECURVE WITH THE BULK OF GUIDANCE 
SHOWING A 150NM SPREAD AT TAU 72. HOWEVER, DUE TO THE CONTINUED 
SPREAD BEYOND TAU 72, THERE REMAINS LOW CONFIDENCE IN THE JTWC TRACK 
FORECAST.//
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