WDPN32 PGTW 010300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 23W (ATSANI) 
WARNING NR 011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION 23W (ATSANI), LOCATED 
APPROXIMATELY 779 NM EAST OF MANILA, PHILIPPINES, HAS 
TRACKED WEST-NORTHWESTWARD AT 19 KNOTS OVER THE PAST 
SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) 
REVEALS THAT THE CENTRAL CONVECTION HAS STRENGTHENED OVER
THE PAST 6 HOURS, HOWEVER THE OVERALL CONVECTIVE STRUCTURE
HAS FAILED TO FURTHER ORGANIZE. THE INITIAL POSITION IS 
PLACED WITH LOW CONFIDENCE BASED ON LOW LEVEL FEATURES IN THE
MSI LOOP. THE INITIAL INTENSITY OF 30 KTS IS PLACED WITH FAIR 
CONFIDENCE BASED ON MULTI-AGENCY DVORAK CURRENT INTENSITY 
ESTIMATES OF T2.0 (PGTW, 30 KTS) AND T2.5 (RJTD, 35 KTS). THE 
ENVIRONMENT IS OVERALL UNFAVORABLE WITH MODERATE (20-25 KTS) 
VERTICAL WIND SHEAR (VWS) AND WEAK OUTFLOW ALOFT OFFSET ONLY 
SLIGHTLY BY WARM (39-30 CELSIUS) SEA SURFACE TEMPERATURES 
(SST). THE CYCLONE IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY 
OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO THE NORTHEAST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE 
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TD 23W WILL CONTINUE ON ITS CURRENT TRACK IN THE 
PHILIPPINE SEA UNDER THE AFOREMENTIONED STR. AFTER TAU 24, A 
SHORTWAVE MIDLATITUDE TROUGH APPROACHING FROM THE NORTHWEST WILL 
ERODE AND SPLIT THE STR AND PULL THE CYCLONE POLEWARD INTO THE 
COL ZONE BETWEEN THE RIDGES. THE ENVIRONMENT IS FORECAST TO 
IMPROVE SLIGHTLY AS VWS WEAKENS IN THE COL ZONE AND POLEWARD 
OUTFLOW IMPROVES. THE SYSTEM IS FORECAST TO STEADILY INTENSIFY 
DURING THIS TIME TO 60 KTS BY TAU 72, HOWEVER, THERE REMAINS THE 
POSSIBILITY OF RAPID INTENSIFICATION DURING THIS TIME, DEPENDING
ON THE TIMING AND MAGNITUDE OF THE INTERACTION BETWEEN THE UPPER 
LEVEL TROUGH AND THE STEERING RIDGE. NUMERICAL MODEL TRACK 
GUIDANCE IS IN FAIR AGREEMENT UP TO TAU 24. AFTERWARD, NAVGEM 
DIVERGES TO THE RIGHT OF THE MODEL ENVELOPE. ALONG TRACK SPREAD 
IN SOLUTIONS ALSO DIVERGE AFTER THIS TIME DUE TO UNCERTAINTY IN 
THE TROUGH-RIDGE INTERACTION. THIS SPREAD IN ALONG TRACK 
SOLUTIONS LENDS ONLY FAIR CONFIDENCE IN THIS INITIAL PORTION OF 
THE JTWC FORECAST TRACK, WHICH IS PLACED SLIGHTLY LEFT OF THE 
MULTI-MODEL CONSENSUS TO OFFSET THE UNLIKELY NAVGEM SOLUTION 
THAT DRIVES THE SYSTEM CENTER INTO THE STR. 
   C. IN THE EXTENDED FORECAST, THE SECONDARY STR BEHIND THE 
SHORTWAVE TROUGH WILL ASSUME STEERING AND SLOWLY DRIVE TD 23W WEST-
SOUTHWESTWARD THEN WESTWARD. ENVIRONMENTAL CONDITIONS ARE FORECAST 
TO IMPROVE EVEN MORE WITH DECREASED VWS (10-15KTS) AND THE ADDITION 
OF AN EQUATORWARD OUTFLOW CHANNEL. THESE CONDITIONS, COUPLED WITH 
CONTINUED WARM SST, WILL ALLOW FOR FURTHER INTENSIFICATION TO 80KTS 
BY TAU 120, BY WHICH TIME IT WILL HAVE MADE LANDFALL OVER LUZON. 
NUMERICAL MODELS SIGNIFICANTLY DIVERGE TO 490 NM BY TAU 120 WITH 
VARYING TRACK SPEEDS, LENDING POOR CONFIDENCE IN THE EXTENDED 
PORTION OF THE JTWC FORECAST TRACK.//
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