WDPN32 PGTW 301200
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 23W (ATSANI) 
WARNING NR 005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION 23W (ATSANI), LOCATED APPROXIMATELY 164 NM 
WEST-SOUTHWEST OF ANDERSEN AFB, GUAM HAS TRACKED NORTHWESTWARD AT 13 
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE 
IMAGERY DEPICTS A VERY DISORGANIZED AND WEAK SYSTEM, WITH MODERATE 
DISORGANIZED FLARING CONVECTION NEAR THE ASSESSED LOW LEVEL 
CIRCULATION CENTER (LLCC). THE SYSTEM HAS BEEN RELOCATED AND THE 
INITIAL POSITION HAS BEEN UPDATED WITH MODERATE CONFIDENCE BASED ON 
ANALYSIS OF THE SCATTEROMETER AMBIGUITIES FROM A 301014Z ASCAT-A AND 
301137Z ASCAT-B PASSES WHICH INDICATE A VERY ELONGATED CIRCULATION 
TO THE SOUTHWEST OF GUAM. THE INITIAL INTENSITY HAS BEEN LOWERED TO 
25 KNOTS BASED ON A T1.5 (25 KNOTS) DVORAK CURRENT INTENSITY 
ESTIMATE FROM PGTW, CONFIRMING THE LOW WINDSPEEDS FROM THE 
SCATTEROMETER PASSES MENTIONED EARLIER, BOTH OF WHICH SHOWED A 
SMATTERING OF VERY ISOLATED 25 KNOT WINDS IN THE NORTHEAST QUADRANT. 
TD 23W REMAINS IN A GENERALLY UNFAVORABLE ENVIRONMENT, HINDERING 
DEVELOPMENT. WHILE SSTS ARE VERY WARM (30 TO 31 DEG CELSIUS), VWS IS 
MODERATE (15-20) AND THE UPPER-LEVEL OUTFLOW IS RELATIVELY WEAK WITH 
NORTHEASTERLY FLOW ASSOCIATED WITH THE OUTFLOW PATTERN OF STY 23W 
CONVERGING OVER TOP OF THE SYSTEM. TD 23W IS TRACKING NORTHWESTWARD 
ALONG THE SOUTHWESTERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE 
(STR) CENTERED TO THE NORTHEAST.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE OVERALL TRACK 
PHILOSOPHY; HOWEVER, THE INITIAL POSITION HAS BEEN RELOCATED AFTER 
RECEIPT OF UPDATED SCATTEROMETER DATA, LEADING TO SIGNIFICANT 
ADJUSTMENT IN TRACK SPEED FROM THE PREVIOUS FORECAST.
   B. TD 23W IS FORECAST TO CONTINUE TRACKING NORTHWESTWARD THROUGH 
TAU 48 ALONG THE SOUTHWESTERN EDGE OF THE STR TO THE NORTHEAST. 
THEREAFTER THE TRACK BEGINS TO FLATTEN TO MORE WESTWARD AS A 
NEW, EAST-WEST ORIENTED STR BEGINS TO THE DEVELOP TO THE NORTH OF 
THE SYSTEM. WHILE IT CONTINUES TO STRUGGLE, THE ENVIRONMENT IS 
SUPPORTIVE OF SLOW INTENSIFICATION AS STY 23W MOVES WESTWARD, AND 
THE UPPER-LEVEL OUTFLOW PATTERN SLOWLY BECOMES MORE FAVORABLE 
THROUGH TAU 48. AFTER TAU 48, AN UPPER-LEVEL ANTICYCLONE IS FORECAST 
TO DEVELOP NEAR THE SYSTEM, WHICH WILL SERVE TO DECREASE VWS AND 
INCREASE OUTFLOW, ALLOWING FOR A PERIOD OF MORE RAPID  
INTENSIFICATION THROUGH TAU 72. MODEL GUIDANCE IS IN FAIR AGREEMENT 
THROUGH TAU 36, WITH INCREASING UNCERTAINTY THEREAFTER, WITH A 
DISTINCT BIFURCATION SCENARIO SETTING UP BY TAU 72. NAVGEM CONTINUES 
TO BE THE SOLE MODEL SOLUTION PREDICTING A FULL RECURVE OF THE 
SYSTEM TO THE NORTHEAST STARTING AT TAU 72. HOWEVER, AFUM AND 
ECMWF ARE TRACKING ON THE NORTHERN EDGE OF THE GUIDANCE PACKAGE ON 
THIS RUN THROUGH TAU 72 AS WELL, BUT NOT TO THE SAME DEGREE AS 
NAVGEM. MEANWHILE, GFS IS THE SOUTHERN OUTLIER SHOWING A FLATTER 
TRACK THAN ALL OTHER MODELS. THE JTWC TRACK LIES ALONG THE SOUTHERN 
EDGE OF A GROUPING OF MODELS THROUGH TAU 48 THEN DIVERGES FURTHER 
SOUTH TOWARDS THE GFS SOLUTION BY TAU 72 WITH LOW FAIR CONFIDENCE. 
   C. BEYOND TAU 72, THE SYSTEM SLOWS SIGNIFICANTLY WHILE TURNING 
WEST AS THE STEERING RIDGE WEAKENS SLIGHTLY AS IT REORIENTS TO A 
MORE EAST-WEST PATTERN. FROM TAU 72 TO 120, THE DEVELOPMENT OF MUCH 
IMPROVED OUTFLOW AND DECREASED VWS WILL ALLOW FOR STEADY 
INTENSIFICATION, PEAKING AT 90 KNOTS AT TAU 96. NUMERICAL MODEL 
GUIDANCE IS HIGHLY UNCERTAIN IN THE EXTENDED FORECAST, WITH 
AFOREMENTIONED BIFURCATION BECOMING VERY DISTINCT BY TAU 120, WITH A 
1000 NM SPREAD BETWEEN THE GFS AND NAVGEM OUTLIERS. HOWEVER, ALL 
REMAINING MEMBERS OF THE CONSENSUS DO CONCUR THAT THE TRACK FLATTENS 
OUT TO WESTWARD AFTER TAU 72 BUT DISAGREE PRIMARILY ON THE SPEED, 
WITH GFS ACCELERATING THE SYSTEM TO WELL OVER 20 KNOTS, AND THE 
REMAINDER INDICATING A MORE REALISTIC SPEED NEAR 10-15 KNOTS. THE 
JTWC FORECAST TRACK LIES CLOSE TO THE MULTI-MODEL CONSENSUS AT TAU 
120 BUT FAVORS THE GFS SOLUTION OVERALL. HOWEVER, WITH THE VERY 
LARGE UNCERTAINTIES ASSOCIATED WITH THE BIFURCATION THERE IS LOW 
CONFIDENCE IN THE JTWC FORECAST TRACK.//
NNNN