Tropical Storm SIX Advisory Wed Aug 12

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 06W (SIX)
WARNING NR 008//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 06W (SIX), LOCATED APPROXIMATELY 681
NM EAST OF KADENA AB, OKINAWA, HAS TRACKED WESTWARD AT 09 KNOTS OVER
THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS
A FULLY-EXPOSED, WELL-DEFINED LOW-LEVEL CIRCULATION WITH ISOLATED
FLARING CONVECTION TO THE SOUTH-SOUTHWEST OF THE CENTER. THEREFORE,
THERE IS HIGH CONFIDENCE IN THE INITIAL POSITION. THE INITIAL
INTENSITY REMAINS ASSESSED AT 25 KNOTS BASED ON RECENT ASCAT DATA AS
WELL AS DVORAK CURRENT INTENSITY ESTIMATES OF 1.5 (25 KNOTS) FROM
PGTW AND RJTD. DESPITE FAVORABLE SST (NEAR 30C), TD 06W CONTINUES TO
STRUGGLE DUE TO PERSISTENT, MODERATE (20 KNOTS) EASTERLY VERTICAL
WIND SHEAR (VWS) AND DRY AIR ENTRAINMENT AS INDICATED IN TOTAL
PRECIPITABLE WATER IMAGERY AND LOW 700-500MB RH VALUES OF 40-45%. TD
06W IS TRACKING WESTWARD UNDER THE SOUTHERN PERIPHERY OF THE LOW-
LEVEL SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTH.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. DUE TO THE WSW-ENE ORIENTATION OF THE LOW-LEVEL STR, TD 06W IS
FORECAST TO GRADUALLY TURN WEST-SOUTHWESTWARD AS IT APPROACHES THE
RYUKYU ISLANDS. ENVIRONMENTAL CONDITIONS ARE EXPECTED TO REMAIN
MARGINAL WITH MODERATE EASTERLY VWS AND DRY AIR ENTRAINMENT (700-
500MB RH VALUES OF 45-50%), THEREFORE, THE SYSTEM SHOULD REMAIN
SHALLOW AND WEAK WITH SOME POTENTIAL FOR DISSIPATION DURING THE
FORECAST PERIOD. NUMERICAL MODEL GUIDANCE SUPPORTS THE JTWC FORECAST
TRACK AND REMAINS IN FAIR AGREEMENT WITH MINOR VARIATIONS IN TRACK
ORIENTATION. MODEL SPREAD BETWEEN TAU 48 AND TAU 72 RANGES FROM 50-
70NM, THEREFORE, THE JTWC FORECAST TRACK IS POSITIONED CLOSE TO THE
MULTI-MODEL CONSENSUS WITH MODERATE CONFIDENCE.//
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