WDPN31 PGTW 070300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 13W (THIRTEEN) 
WARNING NR 01//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 13W, LOCATED APPROXIMATELY 324 NM SOUTH 
OF SASEBO, JAPAN HAS TRACKED NORTH-NORTHEASTWARD AT 17 KNOTS OVER THE
PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS TWO
DEVELOPING FEEDER BANDS WITHIN THE SOUTHEASTERN QUADRANT OF AN
IMPROVING LOW LEVEL CIRCULATION CENTER (LLCC). THE LLCC APPEARS TO
BE PARTIALLY EXPOSED ALONG THE SOUTHWESTERN QUADRANT AS A REGION OF
SLIGHTLY DRIER AIR HAS BEEN OBSERVED MOVING TOWARDS THE CORE OF THE
SYSTEM IN THE TOTAL PRECIPITABLE WATER IMAGERY. OBSERVATIONS NEAR
AMAMI, JAPAN INDICATED 24 KNOTS WITH A 062159Z SSMIS MICROWAVE PASS
REFLECTING AN IMPROVING LLCC STRUCTURE. A RECENT 06/19Z AMSU CROSS-
SECTION INDICATED A 2 DEGREE WARM CORE ANOMALY IN THE 10 TO 12 KM
RANGE, SUPPORTING A TROPICAL SYSTEM. UPPER LEVEL ANALYSIS INDICATES
THE POLEWARD OUTFLOW CHANNEL IS TAPPING INTO THE MID-LATITUDE 
WESTERLIES, LOCATED TO THE SOUTH OF JAPAN. GIVEN THE FAVORABLE SEA
SURFACE TEMPERATURES (SSTS) AND UPPER LEVEL SUPPORT THE ISSUANCE OF
TROPICAL WARNINGS WAS INITIATED. TD 13W IS TRACKING QUICKLY ALONG
THE NORTHWESTERN PERIPHERY OF A DEEP LAYERED SUBTROPICAL RIDGE (STR)
TO THE SOUTHEAST OF THE SYSTEM. 
3. FORECAST REASONING.
   A. THIS IS THE FIRST PROGNOSTIC REASONING MESSAGE AND ESTABLISHES 
THE FORECAST PHILOSOPHY.
   B. TD 13W IS FORECAST TO CONTINUE TRACKING NORTHEASTWARD ALONG 
THE STR THROUGH THE REMAINDER OF THE FORECAST, TAU 72. THE SYSTEM 
WILL STRUGGLE TO DEVELOP AS THE INFLUENCE OF THE MID-LATITUDE 
WESTERLIES INCREASES OVER THE NEXT 36 TO 48 HOURS. DRY AIR AND 
INCREASING VERTICAL WIND SHEAR WILL LIMIT THE OVERALL 
INTENSIFICATION TO 50 KNOTS BY TAU 48. THE FAVORABLE SSTS AND STRONG 
POLEWARD OUTFLOW WILL COMPETE WITH SUBSIDENCE ALONG THE WESTERN 
PERIPHERY AND DRY AIR ENTRAINMENT, INITIALLY FAVORING FURTHER 
DEVELOPMENT, BUT EVENTUALLY LEADING TO THE START OF EXTRA-TROPICAL 
TRANSITION (ETT) AROUND TAU 36. AS TD 13W CONTINUES TO TRACK FURTHER 
NORTHEASTWARD THE ENVIRONMENT WILL CAUSE THE COMPLETION OF THE ETT 
PROCESS BETWEEN TAU 48 AND 72. MODEL GUIDANCE IS IN GOOD AGREEMENT 
LEADING TO HIGH CONFIDENCE IN THE FORECAST TRACK.//
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