Tropical Storm VONGFONG Advisory Thu Oct 02

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 19W (NINETEEN)
WARNING NR 01//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 19W (NINETEEN), LOCATED APPROXIMATELY
147 NM EAST-NORTHEAST OF POHNPEI, HAS TRACKED WESTWARD AT 10 KNOTS
OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE IMAGERY
DEPICTS A CONSOLIDATING AND ELONGATED LOW-LEVEL CIRCULATION CENTER
(LLCC) WITH PERSISTENT DEEP CONVECTION. A 021915Z WINDSAT CORIOLIS
MICROWAVE IMAGE ALSO DEPICTS FORMATIVE BANDING LOCATED ON THE
EASTERN AND NORTHERN PERIPHERY OF THE SYSTEM. DUE TO THE BROAD
NATURE OF THE SYSTEM, THE INITIAL POSITION IS SET WITH FAIR
CONFIDENCE. THE INITIAL INTENSITY IS ASSESSED AT 30 KNOTS BASED ON
DVORAK CURRENT INTENSITY ESTIMATES OF T2.0 FROM PGTW. UPPER-LEVEL
ANALYSIS INDICATES A FAVORABLE ENVIRONMENT WITH LOW VERTICAL WIND
SHEAR AND GOOD OUTFLOW. TD 19W IS TRACKING ALONG THE
SOUTHERN PERIPHERY OF DEEP SUBTROPICAL RIDGE (STR).
3. FORECAST REASONING.
   A. THIS IS THE INITIAL PROGNOSTIC REASONING AND SETS THE
FORECAST PHILOSOPHY.
   B. TD 17W WILL TRACK TO THE NORTH-NORTHWEST UNDER THE STEERING
INFLUENCE OF THE STR. THE SYSTEM IS EXPECTED TO CONTINUE TO SLOWLY
CONSOLIDATE OVER THE NEXT 72 HOURS, REACHING AN INTENSITY OF 60
KNOTS JUST EAST OF THE MARIANA ISLANDS. LIMITED MODEL GUIDANCE IS IN
GOOD AGREEMENT OF A CONTINUED NORTH-NORTHWESTERN UNDER THE STEERING
INFLUENCE OF THE DEEP STR.
   C. IN THE EXTENDED TAUS, THE FAVORABLE UPPER LEVEL ENVIRONMENT
AND GOOD SEA SURFACE TEMPERATURES WILL ALLOW TD 19W TO CONTINUE TO
STRENGTHEN TO TYPHOON STRENGTH AFTER TAU 72 AND REACH ITS PEAK,
DURING THIS FORECAST PERIOD, OF 90 KNOTS AT TAU 120. HOWEVER, DUE TO
THE SYSTEM TAKING A SIMILAR TRACK TO 18W, EXPECT SLIGHTLY LESS
OVERALL INTENSIFICATION DUE TO THE ABSORPTION OF SOME OF THE OCEAN
HEAT CONTENT BY THE PREVIOUS STORM TRACK. OVERALL, THERE IS LOW
CONFIDENCE IN THE JTWC FORECAST BASED ON THE LIMITED MODEL
GUIDANCE.//
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