WDPN33 PGTW 171500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 13W (THIRTEEN) 
WARNING NR 03//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION 13W (THIRTEEN), LOCATED APPROXIMATELY 58 NM
NORTH-NORTHEASTWARD OF KADENA AB, HAS TRACKED WEST-NORTHWESTWARD
AT 11 KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE 
IMAGERY (IR) REVEALS THE STRUCTURE OF THE SYSTEM CONTINUES TO 
STRUGGLE DESPITE SOME SLIGHT DEEPENING OF THE CONVECTION AROUND THE 
ILL-DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC). A 171055Z SSMIS 
91GHZ MICROWAVE IMAGE SHOWS CONVECTION CONTINUES TO BE FRAGMENTED 
ALONG THE NORTHERN PERIPHERY OF THIS COMPACT SYSTEM WITH NO REAL 
IMPROVEMENTS TO THE OVERALL ORGANIZATION. THE INITIAL POSITION IS 
MOSTLY BASED UPON THE AFOREMENTIONED MICROWAVE IMAGE DUE TO LARGE 
AMOUNTS OF AMBIGUITY IN THE IR LOOP. THE INITIAL INTENSITY HAS BEEN 
HELD AT 25 KNOTS BASED UPON DVORAK INTENSITY ESTIMATES FROM ALL 
AGENCIES AND THE UNCHANGED STRUCTURE OF THE SYSTEM. UPPER-LEVEL 
ANALYSIS REVEALS THE SYSTEM IS LOCATED SOUTH OF THE SUBTROPICAL 
RIDGE AXIS AND IS IN POOR TO MODERATE ENVIRONMENT AS AN UPPER-LEVEL 
LOW SOUTH OF THE SYSTEM HAS LIMITED THE OUTFLOW AND SLIGHTLY 
INCREASED VERTICAL WIND SHEAR TO MODERATE (10-20 KNOTS) LEVELS. TD 
13W IS CURRENTLY TRACKING WEST-NORTHWEST ALONG THE SOUTHERN 
PERIPHERY OF A LOW TO MID-LEVEL SUBTROPICAL STEERING RIDGE (STR) 
NORTH OF THE SYSTEM.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. TD 13W IS FORECAST TO CONTINUE TO TRACK GENERALLY WEST THROUGH 
TAU 36 AS IT CONTINUES TO MOVE ALONG THE PERIPHERY OF THE STR. AFTER 
TAU 36, DIRECT CYCLONE INTERACTION (DCI) IS EXPECTED TO BECOME THE 
DOMINANT STEERING INFLUENCE AS TD 13W BEGINS TO ORBIT AROUND AND 
INTO TD 12W. SLOW INTENSIFICATION IS EXPECTED THROUGH THE EARLY 
FORECAST PERIODS, AS MODERATELY FAVORABLE CONDITIONS OF WARM SEA 
SURFACE TEMPERATURES, LOW TO MODERATE VWS, AND IMPROVED OUTFLOW ARE 
EXPECTED. THE PROXIMITY AND INTENSITY OF NEIGHBORING TD 12W COULD 
CREATE A LESS FAVORABLE UPPER-LEVEL ENVIRONMENT WHICH WOULD LEAD TO 
A LOWER INTENSITY FORECAST.
   C. TD 13W IS EXPECTED CONTINUE TO INTERACT WITH TD 12W IN THE 
EXTENDED TAUS, AND EVENTUALLY MERGE INTO TD 12W BY TAU 96. DYNAMIC 
MODEL GUIDANCE CONTINUES TO SHOW TWO DISTICT SCENARIOS WITH THIS 
SYSTEM. ECMWF, JGSM AND NAVGEM SHOW TD 13W TRACKING FASTER AND 
FURTHER WEST IN THE EARLY TAUS. THIS SCENARIO TRACKS THE SYSTEM INTO 
MAINLAND CHINA BY TAU 72 AND RAPIDLY DISSIPATES THE SYSTEM DUE TO 
THE UNFAVORABLE UPPER LEVEL ENVIRONMENT AND LAND INTERACTION. EGRR, 
GFDN, AND GFS CONTINUE TO SHOW A DCI SCENARIO WITH A MERGE OF THE 
TWO SYSTEMS BY TAU 96. LOW CONFIDENCE REMAINS IN THE FORECAST DUE 
THE SEPERATE SCENARIOS DISPLAYED BY THE MODELS.//
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