Tropical Storm SANVU Advisory Pzt, 21.05.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 03W (THREE)
CORRECTED/WARNING NR 01//
RMKS//
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 03W, LOCATED APPROXIMATELY 160 NM SOUTH-
SOUTHEAST OF ANDERSEN AFB, GUAM, HAS TRACKED WESTWARD AT 06 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL (MSI) SATELLITE
IMAGERY CONTINUES TO SHOW AN OVERALL IMPROVEMENT IN THE
CONSOLIDATION OF CONVECTION SURROUNDING THE LOW-LEVEL CIRCULATION
CENTER (LLCC). A 210221Z OSCAT PASS INDICATES A LOW-LEVEL
CIRCULATION CENTER (LLCC) LOCATED DUE SOUTH OF GUAM. RECENT RADAR
REFLECTIVITIES FROM GUAM INDICATE SHARP TURNING WITHIN A STRONG
CONVECTIVE CLUSTER LOCATED NEAR THE OSCAT CIRCULATION. HOWEVER, THE
MSI AND RECENT MICROWAVE DATA DO NOT SUPPORT A LLCC IN THIS
LOCATION. CONSIDERING THE PAST HISTORY OF THIS MONSOON DEPRESSION
LIKE SYSTEM, AND ASSOCIATED MESOVORTICES ROTATING CYCLONICALLY
AROUND THE CENTER OF MASS, IT IS BELIEVED THAT THE CIRCULATION SOUTH
OF GUAM IS NOT THE TRUE LLCC. THE MSI AND MICROWAVE DATA PROVIDE FOR
A MORE TIME TESTED ANALYSIS TOOL THAN THE EXPERIMENTAL OSCAT
PRODUCT. THEREFORE, THE CURRENT POSITION IS BASED ON THE MSI AND
MICROWAVE DATA BUT THE CONFIDENCE REMAINS LOW DUE TO THE CONFLICTING
OSCAT PASS. THE CURRENT INTENSITY IS BASED ON DVORAK ESTIMATES
RANGING FROM 25-30 KNOTS FROM RJTD/KNES AND PGTW RESPECTIVELY. THE
WIND FIELD FOR TD 03W, AS SEEN IN PAST SCATTEROMETER DATA, HAS BEEN
CONSISTENT WITH A MONSOON DEPRESSION IN THAT CENTRAL WINDS ARE
LIGHTER AND PERIPHERAL WINDS ARE STRONGER, ESPECIALLY ON THE
NORTHEASTERN QUADRANT. TD 03W IS TRACKING ALONG THE SOUTHWESTERN
PERIPHERY OF THE SUBTROPICAL RIDGE (STR) CENTERED FAR TO THE
NORTHEAST. THE UPPER-LEVEL ENVIRONMENT HAS IMPROVED DURING THE PAST
24 HOURS, AS EVIDENT IN THE PGTW 210000Z UPPER-LEVEL STREAMLINE
ANALYSIS AND ANIMATED WATER VAPOR IMAGERY. THE TROPICAL UPPER
TROPOSPHERIC TROUGH (TUTT) CELL LOCATED SOUTHWEST OF GUAM HAS
CONTINUED TO MIGRATE WESTWARD AND THE DIVERGENT SIDE OF THE TUTT
CELL IS NOW ENHANCING THE POLEWARD OUTFLOW OF THE DISTURBANCE.
ADDITIONALLY, AN IMPROVEMENT IN EQUATORWARD OUTFLOW HAS OCCURRED
WITH THE DEVELOPMENT OF A POINT SOURCE OF DIFFLUENCE LOCATED JUST TO
THE EAST OF THE LLCC. OUTFLOW TO THE EAST INTO A TUTT CELL NEAR THE
DATELINE ALSO REMAINS ROBUST.
3. FORECAST REASONING.
   A. THIS IS THE INITIAL PROGNOSTIC REASONING AND SETS THE
FORECAST PHILOSOPHY.
   B. THE ORIENTATION OF THE STR IS EXPECTED TO BREAK DOWN AND
RETROGRADE TO THE EAST AS AN APPROACHING MID-LATITUDE TROUGH,
EXTENDING FROM CYCLOGENISIS CURRENTLY DEVELOPING OVER SOUTHERN
JAPAN, INTERACTS WITH THE RIDGING. TD 03W SHOULD PASS JUST SOUTH OF
GUAM DURING THE NEXT 12-18 HOURS AND THEN TRACK GENERALLY
NORTHWESTWARDS AROUND THE ERODING STR PERIPHERY. BY TAU 48 THE
SYSTEM SHOULD BEGIN TO ROUND THE STR AND BEGIN A MORE POLEWARD
TRACK WHICH WILL STEER TOWARDS A RE-CURVATURE INTO THE MID-
LATITUDES. INTENSITY DURING THIS TIME SHOULD GRADUALLY INCREASE AS
THE UPPER-LEVEL ENVIRONMENT REMAINS FAVORABLE.
   C. AFTER TAU 72, TD 03W IS FORECAST TO MOVE NORTH OF THE STR AND
BEGIN TO INTERACT WITH THE MID-LATITUDE BAROCLINIC ZONE. EXTRA-
TROPICAL TRANSITION (ET) SHOULD BEGIN DURING TAU 96 WITH COMPLETION
INTO THE WESTERLIES BY TAU 120. DURING THIS TIME INTENSITY WILL
BEGIN TO DECREASE DUE TO AN INCREASE IN VERTICAL WINDSHEAR. MOST
MODELS ARE IN AGREEMENT WITH SHOWING THE SYSTEM FULLY INCORPORATED
IN THE MID-LATITUDE WESTERLIES BY TAU 120. THERE IS LOW CONFIDENCE
IN THE FORECAST TRACK BASED ON THE POOR INITIAL POSITION
CONFIDENCE. HOWEVER, THERE IS A LOW DEGREE OF SPREAD WITHIN THE
OBJECTIVE AIDS DURING THE FIRST 48 HOURS.
4.JUSTIFICATION FOR CORRECTION: CHANGED 6 HOUR SUMMARY TO 12 HOUR
SUMMARY IN PARA 2 HEADER. ADDED GEOGRAPHIC REFERENCE AND PAST 6 HOUR
MOTION IN PARA 2 BODY.//
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