Tropical Storm ATSANI Advisory Paz, 01.11.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 23W (ATSANI)
WARNING NR 010//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION 23W (ATSANI), LOCATED APPROXIMATELY
899 NM EAST OF MANILA, PHILIPPINES, HAS TRACKED WEST-
NORTHWESTWARD AT 09 KNOTS OVER THE PAST SIX HOURS. ANIMATED
ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A WEAK AND
DISORGANIZED SYSTEM WITH FLARING CENTRAL CONVECTION OBSCURING
A LOW LEVEL CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS
PLACED WITH LOW CONFIDENCE BASED ON LOW LEVEL FEATURES IN THE
EIR LOOP. THE INITIAL INTENSITY OF 30 KTS IS PLACED WITH FAIR
CONFIDENCE BETWEEN MULTI-AGENCY DVORAK CURRENT INTENSITY
ESTIMATES OF T1.5 (PGTW, 20 KTS) AND T2.5 (RJTD, 35 KTS). THE
ENVIRONMENT IS OVERALL UNFAVORABLE WITH MODERATE (15-20 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 36, 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 55 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 36. 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. ADDITIONALLY, THERE REMAINS THE POSSIBILITY FOR RAPID
INTENSIFICATION AT THIS TIME. NUMERICAL MODELS SIGNIFICANTLY DIVERGE
TO OVER 400NM BY TAU 120 WITH VARYING TRACK SPEEDS, LENDING POOR
CONFIDENCE IN THE EXTENDED PORTION OF THE JTWC FORECAST TRACK.//
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