MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 13W (THIRTEEN)
WARNING NR 01//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL DEPRESSION (TD) 13W (THIRTEEN), LOCATED APPROXIMATELY 414
NM NORTH-NORTHEAST OF POHNPEI, FSM, HAS TRACKED NORTHWESTWARD AT 14
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY (MSI) SHOWS A FAST-CONSOLIDATING SYSTEM WITH FORMATIVE BANDS
WRAPPING INTO AN OBSCURED LOW LEVEL CIRCULATION CENTER. THE INITIAL
POSITION IS BASED ON THE MSI LOOP WITH POOR CONFIDENCE. THE INITIAL
INTENSITY OF 30 KNOTS IS BASED ON AN OVERALL ASSESSMENT OF DVORAK
ESTIMATES FROM PGTW, KNES, AND RJTD. UPPER-LEVEL ANALYSIS INDICATES A
MARGINALLY-FAVORABLE ENVIRONMENT WITH LOW TO MODERATE VERTICAL WIND
SHEAR (VWS) OFFSET BY GOOD POLEWARD OUTFLOW, ENHANCED BY A TUTT CELL
TO THE NORTH-NORTHWEST. ALONG-TRACK SSTS ABOVE 28 CELSIUS AND HIGH
OCEAN HEAT CONTENT ARE ALSO CONDUCIVE FOR FURTHER DEVELOPMENT. THE
CYCLONE IS CURRENTLY TRACKING ALONG THE SOUTHERN PERIPHERY OF A
DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO THE NORTH.
3. FORECAST REASONING.
A. THIS IS THE INITIAL PROGNOSTIC REASONING MESSAGE AND SETS THE
FORECAST PHILOSOPHY.
B. TD 13W IS FORECAST TO TRACK WESTWARD TO WEST-NORTHWESTWARD
THROUGHOUT THE FORECAST UNDER THE INFLUENCE OF THE STR. WITH
ENVIRONMENTAL CONDITIONS EXPECTED TO BE CONDUCIVE FOR DEVELOPMENT,
THE SYSTEM WILL REACH 100 KNOTS BY TAU 72.
C. IN THE EXTENDED TAUS, UPPER LEVEL CONDITIONS WILL BECOME
INCREASINGLY FAVORABLE WITH LOW VWS AND EXCELLENT DIVERGENT OUTFLOW.
BY THE END OF THE FORECAST, TD 13W WILL REACH 125 KNOTS. NUMERIC
MODEL GUIDANCE IS IN UNUSUALLY GOOD AGREEMENT, GIVEN THAT THIS IS THE
INITIAL FORECAST. HOWEVER, DUE TO THE DEVELOPMENTAL STAGE OF THE
SYSTEM, THERE IS - FOR NOW - LOW CONFIDENCE IN THE JTWC TRACK
FORECAST.//
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