
WDPN35 PGTW 242100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 15W (JONGDARI)
WARNING NR 12//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM (TS) 15W (JONGDARI), LOCATED APPROXIMATELY 358 NM
SOUTHWEST OF IWO TO, JAPAN, HAS TRACKED NORTHWARD AT 08 KNOTS OVER
THE PAST SIX HOURS. ANIMATED EIR SATELLITE IMAGERY SHOWS A COMPACT
SYSTEM THAT HAS SLOWLY CONSOLIDATED, FUELED BY A NARROW EASTWARD
OUTFLOW INTO A TUTT CELL TO THE EAST-NORTHEAST AND GOOD EQUATORWARD
OUTFLOW. THE INITIAL POSITION IS BASED WITH FAIR CONFIDENCE ON THE
LLC FEATURE IN THE 37 GHZ 241806Z SSMI MICROWAVE PASS. THE INITIAL
INTENSITY OF 35 KNOTS IS BASED ON AN OVERALL ASSESSMENT OF AGENCY
DVORAK ESTIMATES OF T2.0 AND A SATCON DVORAK ESTIMATE OF T3.1. UPPER
LEVEL ANALYSIS INDICATES THE SYSTEM IS IN A NARROW ZONE OF LIGHT TO
MODERATE RELATIVE VWS (10-15 KNOTS) THAT IS OFFSET BY OUTFLOW. THERE
IS ALSO SUBSIDENCE ALONG THE NORTHWEST QUADRANT CAUSED BY STRONG
NORTHEASTERLY WINDS ASSOCIATED WITH AN STR ANCHORED TO THE NORTH OVER
THE SEA OF JAPAN (SOJ). ALONG-TRACK SSTS REMAIN FAVORABLE FOR NOW
AT 28 CELSIUS. THE CYCLONE IS TRACKING ALONG THE WESTERN BOUNDARY OF
AN NER TO THE EAST.
3. FORECAST REASONING.
A. THERE IS NO CHANGE TO THE OVERALL FORECAST PHILOSOPHY SINCE
THE PREVIOUS PROGNOSTIC REASONING MESSAGE. HOWEVER, THE NEAR- TO
MID-TERM PORTION OF THE FORECAST TRACK IS LAID JUST OVER 30 NM LEFT
OF THE PREVIOUS TRACK AS A RESULT OF A WESTWARD ADJUSTMENT IN THE
BEST TRACK.
B. TS 15W IS FORECAST TO TRACK GENERALLY NORTHEASTWARD THROUGH TAU
TAU 72 AS IT ROUNDS THE WESTERN EDGE OF THE STEERING NER. A
STEADY INTENSIFICATION IS EXPECTED AS THE OVERALL FAVORABLE
CONDITIONS PREVAIL. CONCURRENTLY, AN UPPER-LEVEL LOW BETWEEN THE
AFOREMENTIONED STR AND A SECONDARY STR TO ITS NORTHEAST WILL ELONGATE
AND DESCEND SOUTHWARD TO THE EAST OF HONSHU. THIS ORIENTATION WITH
TS 15W WILL ENHANCE OUTFLOW AND CONTRIBUTE TO ITS INTENSIFICATION TO
A PEAK OF 95 KNOTS AT TAU 72. THE NUMERICAL GUIDANCE IS IN OVERALL
GOOD AGREEMENT IN THIS PORTION OF THE FORECAST WITH THE NOTABLE
EXCEPTION OF NAVGEM THAT DEVIATES FROM THE MODEL ENVELOPE FROM TAU 48
TO A DISTANCE OF 175 NM FROM TO THE RIGHT OF CONSENSUS AT TAU 72.
AFTER A SLIGHT ADJUSTMENT TO OFFSET THIS DEVIATION, THERE IS OVERALL
A HIGH CONFIDENCE IN THIS PORTION OF THE JTWC TRACK FORECAST.
C. AFTER TAU 72, THE SECONDARY STR TO THE NORTHEAST WILL BUILD AND
ASSUME STEERING AND DRIVE TS JONGDARI NORTH-NORTHWESTWARD THEN
NORTHWESTWARD. BY TAU 96, THE SYSTEM WILL HAVE MADE LANDFALL NEAR
TOKYO, JAPAN. INCREASING VWS, PROXIMITY TO THE UPPER LEVEL LOW, AND
COOLING SSTS WILL GRADUALLY ERODE THE SYSTEM. HOWEVER, 15W WILL STILL
BE AT A SOLID TYPHOON INTENSITY OF 75 KNOTS WHEN IT MAKES LANDFALL
OVER JAPAN. AFTERWARD, INTERACTION WITH THE RUGGED JAPANESE ALPS AND
THE COLD WATERS OF THE SOJ, IN ADDITION TO INCREASING VWS, WILL
RAPIDLY WEAKEN THE SYSTEM DOWN TO 35 KNOTS. THE NUMERICAL MODEL
GUIDANCE SIGNIFICANTLY SPREAD OUT IN THIS PORTION OF THE FORECAST,
LENDING AN OVERALL LOW CONFIDENCE TO THE EXTENDED PORTION OF THE JTWC
FORECAST TRACK.//
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