WDPN32 PGTW 190300 
MSGID/GENADMIN/NAVPACMETOCCEN PEARL//JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 20W (NARI) WARNING 
NR 53//
RMKS/
1. FOR METEOROLOGISTS.
2. PROGNOSTIC REASONING FOR 190000Z0 TO 220000Z4 SEP 01.
   A. TROPICAL DEPRESSION (TD) 20W (NARI), LOCATED APPROXIMATELY 300 
NM EAST OF HONG KONG HAS TRACKED SOUTH-SOUTHWESTWARD AT 08 KNOTS 
DURING THE PAST SIX HOURS. THE WARNING POSITION IS BASED ON 182330Z7 
INFRARED AND VISIBLE SATELLITE IMAGERY, RADAR DATA, AND SYNOPTIC 
REPORTS. THE WARNING INTENSITY IS BASED ON SATELLITE CURRENT 
INTENSITY ESTIMATES OF 30 KNOTS AND SYNOPTIC REPORTS.
    B. THE SYSTEM IS FORECAST TO TRACK WESTWARD UNDER THE STEERING 
INFLUENCE OF A LOW TO MID LEVEL RIDGE BUILDING OVER SOUTHERN CHINA. 
NOGAPS, GEOPHYSICAL FLUID DYNAMIC NAVY (GFDN), UK-MET OFFICE (EGRR), 
THE JMA GLOBAL SPECTRAL (JGSM), CSUM , AND THE BETA ADVECTION MODELS 
ARE IN GOOD AGREEMENT TRACKING THE SYSTEM WEST-SOUTHWESTWARD THROUGH 
THE PERIOD. OUR FORECAST IS BASED ON PERSISTENCE AND THE NUMERICAL 
CONSENSUS OF THE FOUR DYNAMICAL AIDS BLENDED WITH THE BETA ADVECTION 
MODELS AND CSUM.
   C. TD 20W IS EXPECTED TO SLIGHTLY INTENSIFY AS THE SYSTEM 
MOVES OVER WARMER SEA SURFACE TEMPERATURES IN THE SOUTH CHINA SEA. 
AFTER THE 24-HOUR FORECAST PERIOD THE SYSTEM SHOULD BEGIN TO WEAKEN 
AS IT INTERACTS WITH THE SOUTHERN COAST OF CHINA.     
   D. TD 20W DOES NOT MEET WIND RADII CRITERIA.  
FORECAST TEAM: MAZANY/MORRIS/EDBERG//