Tropical Storm BOLAVEN Advisory Mon Aug 20

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 16W (SIXTEEN)
WARNING NR 01//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 16W (SIXTEEN), LOCATED APPROXIMATELY 430
NM SOUTH OF IWO TO, HAS TRACKED NORTH-NORTHWESTWARD AT 07 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
(MSI) DEPICTS INCREASING CONSOLIDATION IN THE DEEP CONVECTIVE
BANDING OVER THE LOW-LEVEL CIRCULATION CENTER (LLCC). THE CURRENT
POSITION IS BASED ON THE MSI AND A 192303Z SSMIS 91 GHZ MICROWAVE
IMAGE WITH GOOD CONFIDENCE. THE CURRENT INTENSITY IS BASED ON DVORAK
ESTIMATES RANGING FROM 25 TO 35 KNOTS FROM RJTD, KNES, AND PGTW.
UPPER-LEVEL ANALYSIS INDICATES THE DEPRESSION IS LOCATED  A FEW
DEGREES NORTH OF A NEAR EQUATORIAL RIDGE (NER) AXIS UNDER WEAK (05-
10 KNOTS) VERTICAL WIND SHEAR WITH GOOD DIVERGENCE ALOFT. IT SEEMS
THAT A POINT SOURCE OF DIVERGENCE IS BEGINNING TO DEVELOP OVER THE
LLCC. ANIMATED WATER VAPOR IMAGERY SHOWS GOOD EQUATORWARD OUTFLOW
AND ENHANCED EASTWARD OUTFLOW INTO A TROPICAL UPPER-TROPOSPHERIC
TROUGH CELL LOCATED 10 DEGREES WEST OF THE DATELINE. ADDITIONALLY,
THE VORTICITY FROM 98W IS PROPAGATING CLOSER TO TD 16W AND SHOULD BE
ABSORBED INTO TD 16W DURING THE NEXT 18-24 HOURS. THE SYSTEM IS
CURRENTLY BEING STEERED BY THE NORTHWESTERN PERIPHERY OF THE NER.
3. FORECAST REASONING.
   A. THIS IS THE INITIAL PROGNOSTIC REASONING AND SETS THE FORECAST
PHILOSOPHY.
   B. TD 16W WILL BE STEERED BY THE NORTHWESTERN PERIPHERY OF THE
NER DURING THE NEXT 12 HOURS. AFTER TAU 12 THE SYSTEM WILL COME
UNDER THE STEERING INFLUENCE OF THE SOUTHERN PERIPHERY OF THE DEEP-
LAYERED SUBTROPICAL RIDGE (STR) CENTERED EAST OF JAPAN. THIS
STEERING STR WILL BECOME MORE ZONAL THROUGHOUT THE FORECAST PERIOD
AS A MID-LATITUDE TROUGH, CURRENTLY OVER NORTHERN CHINA, CONTINUES
TO PROPAGATE EASTWARD. TD 16W WILL INTENSIFY DUE TO FAVORABLE SEA
SURFACE TEMPERATURES (27-30 DEGREES CELSIUS) AND GOOD UPPER-LEVEL
ENVIRONMENTALS.
   C. IN THE EXTENDED FORECAST TD 16W WILL CONTINUE TO INTENSIFY AND
TRACK GENERALLY WESTWARD UNDER THE STABLE STEERING INFLUENCE OF THE
STR. OBJECTIVE AID GUIDANCE IS LIMITED BUT IN GOOD AGREEMENT ON THE
WESTWARD TRACK, THEREFORE, THERE IS HIGH CONFIDENCE IN THE TRACK
FORECAST. TRACK SPEEDS WERE KEPT SLIGHTLY FASTER THAN THE MODEL
CONSENSUS AFTER TAU 48 TO ACCOUNT FOR THE STEERING INFLUENCE.//
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