Tropical Storm ATSANI Advisory Sun Nov 01

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 23W (ATSANI)
WARNING NR 012//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION 23W (ATSANI), LOCATED APPROXIMATELY 689 NM
EAST OF MANILA, PHILIPPINES, HAS TRACKED WEST-NORTHWESTWARD AT 16
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY (MSI) SHOWS A WEAK SYSTEM THAT HAS MAINTAINED AN OVERALL
POORLY-ORGANIZED CONVECTIVE STRUCTURE. THE INITIAL POSITION IS
PLACED WITH LOW CONFIDENCE BASED ON LOW-CLOUD TRACING INTO AN
OBSCURED LOW LEVEL CIRCULATION IN THE MSI LOOP. THE INITIAL
INTENSITY OF 30 KTS IS BASED ON THE DVORAK ESTIMATE ESTIMATE OF
T2.0/30KTS FROM PGTW. THE ENVIRONMENT IS OVERALL UNFAVORABLE WITH
MODERATE (20-25KT) VERTICAL WIND SHEAR (VWS) AND WEAK OUTFLOW ALOFT
OFFSET BY WARM (29-30C) 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 NORTHWESTWILL ERODE AND
SPLIT THE STR AND PULL THE CYCLONE POLEWARD INTO A QUASI-STATIONARY
STATE IN THE COL ZONE BETWEEN THE TWO RIDGES. THE ENVIRONMENT IS
FORECAST TO IMPROVE SLIGHTLY AS VWS WEAKENS AND POLEWARD OUTFLOW
IMPROVES, FUELING A STEADY INTENSIFICATION TO 60KTS BY TAU 72.
NUMERICAL MODELS ARE IN GOOD AGREEMENT UP TO TAU 24 WITH NAVGEM THE
SOLE OUTLIER TO THE RIGHT. AFTERWARD, THE MODELS DIVERGE
SIGNIFICANTLY WITH VARYING SOLUTIONS IN THE DURATION OF QS STATE IN
THE COL, LENDING LOW CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST
TRACK.
   C. IN THE EXTENDED TAUS, THE SECONDARY STR BEHIND THE SHORTWAVE
TROUGH WILL ASSUME STEERING AND SLOWLY DRIVE TD 23W 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 85KTS AS IT CROSSES THE LUZON
STRAIT. NUMERICAL MODELS SIGNIFICANTLY DIVERGE TO 400 NM BY TAU 120
WITH VARYING TRACK SPEEDS, LENDING POOR CONFIDENCE IN THE EXTENDED
PORTION OF THE JTWC FORECAST TRACK.//
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