WDPN31 PGTW 171500
MSGID/GENADMIN/NAVPACMETOCCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 01W WARNING NR 
08//
RMKS/
1. FOR METEOROLOGISTS.
2. PROGNOSTIC REASONING FOR 171200Z1 TO 201200Z5 JAN 03.
   A. TROPICAL DEPRESSION (TD) 01W, LOCATED APPROXIMATELY 325 NM 
EAST-SOUTHEAST OF GUAM, HAS TRACKED WEST-NORTHWESTWARD AT 13 
KNOTS OVER THE PAST 06 HOURS. THE WARNING POSITION IS BASED ON 
171130Z3 ANIMATED SATELLITE IMAGERY. CONVECTION AGAIN HAS ALL BUT 
CEASED OVER THE PAST 8 HOURS. THE LOW LEVEL CIRCULATION CENTER 
(LLCC) REMAINS WEAK IN THE SYNOPTIC AND QUICKSCAT DATA, WITH MAXIMUM 
WINDS NEAR 25 KNOTS ALONG THE NORTHERN EDGE OF THE SYSTEM. RECENT 
MICROWAVE IMAGERY INDICATES A SINGLE THUNDERSTORM OVER THE LLCC. THE 
WARNING INTENSITY IS BASED ON SATELLITE CURRENT INTENSITY ESTIMATES 
OF 30 TO 35 KNOTS AND RECENT QUICKSCAT DATA.
   B. TD 01W IS FORECAST TO TRACK NORTHWESTWARD INITIALLY, THEN 
INCREASINGLY NORTHWARD UNDER THE INFLUENCE OF THE LOW LEVEL RIDGE 
NORTHEAST OF THE SYSTEM. THE MORE NORTHWARD TRACK WILL MOVE THE 
SYSTEM INTO A WEAKNESS IN THE SUBTROPICAL RIDGE, CAUSED BY A PASSING 
MID-LATITUDE TROUGH. THE AVAILABLE DYNAMIC AIDS CONSISTING OF 
NOGAPS, THE JAPANESE GLOBAL SPECTRAL MODEL (JGSM), UKMET GLOBAL 
SPECTRAL MODEL (EGRR), NCEP AVIATION (AVN), GFDN, COAMPS, THE 
COLORADO STATE UNIVERSITY MODEL, AND THE BETA ADVECTION MODELS ARE 
IN GOOD AGREEMENT THROUGH THE 48 HOURS. AFTER, JGSM, EGRR, AND AVN 
TAKE A POLEWARD TURN, WHILE GFDN AND NOGAPS KEEPS THE SYSTEM WEAKER 
AND HAS A MORE EQUATORWARD BIAS. MULTIPLE CYCLONES BECOME VISIBLE AT 
THE LATER PERIODS IN MOST MODEL RUNS, AND INDICATING INCREASED 
WEAKENING AND MULTIPLE POSSIBLE PATHS. THE PATH THE SYSTEM 
EVENTUALLY TAKES WILL DEPEND MOSTLY ON THE INTENSITY OF THE SYSTEM, 
IF IT IS STRONG ENOUGH, IT MAY RECURVE AND UNDERGO EXTRATROPICAL 
TRANSITION, IN THE MID-LATITUDE FLOW, BUT IF IT REMAINS WEAK, IT 
WILL MORE LIKELY MOVE MORE WESTWARD AS AN EXPOSED LOW LEVEL 
CIRCULATION CENTER. THE CONSENSUS OBJECTIVE AIDS TAKE THE SYSTEM 
INTO THE WEAKNESS IN THE RIDGE AROUND THE 48 HOUR POINT, THEN 
VIRTUALLY STOP THE SYSTEM WITHIN THE WEAKNESS AT 72 HOURS. OUR 
FORECAST IS BASED ON PERSISTENCE AND A BLEND OF THE AVAILABLE 
DYNAMIC AIDS.
   C. THE SYSTEM HAS PULSED IN INTENSITY OVER THE PAST 24 HOURS, 
WEAKENING TO BELOW TROPICAL STORM STRENGTH DURING THE NIGHT, THEN 
REINTENSIFYING AT DAWN TO TROPICAL STORM STRENGTH. IT IS POSSIBLE 
THAT THE SYSTEM WILL UNDERGO SIMILAR PULSING IN INTENSITY OVER THE 
NEXT 24 HOURS. OVERALL, TD 01W IS EXPECTED TO CONTINUE TO INTENSIFY 
SLOWLY THROUGH THE PERIOD AS IT BEGINS TO SLOW DOWN. THERE IS 
POTENTIAL THAT THE SYSTEM WILL RAPIDLY WEAKEN TOWARD THE END OF THE 
PERIOD DUE TO INCREASING VERTICAL WIND SHEAR ASSOCIATED WITH THE 
MID-LATITUDE UPPER-LEVEL WESTERLIES. AS A LONG WAVE TROUGH MOVES OFF 
MAINLAND ASIA, THERE IS POTENTIAL FOR ENHANCED DEVELOPMENT AS THE 
SYSTEM MOVES INTO THE OUTFLOW AREA OF THE UPPER-LEVEL TROUGH. 
   D. FORECAST WIND RADII ARE BASED ON CLIMATOLOGY FOR AN AVERAGE 
SIZED SYSTEM, AND A RECENT QUICKSCAT PASS INDICATING SIGNIFICANTLY 
STRONGER WINDS IN THE NORTHERN HALF OF THE SYSTEM.
FORECAST TEAM: WAKEHAM/RONSSE/ANDERSON/MENEBROKER//

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