WDPN31 PGTW 141500
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 15W (MEGI) WARNING
NR 07//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
   A. TROPICAL STORM (TS) 15W (MEGI) LOCATED APPROXIMATELY 210 NM
NORTH OF YAP, HAS TRACKED WEST-NORTHWESTWARD AT 08 KNOTS OVER THE
PAST SIX HOURS. ANIMATED INFRARED SATELLITE IMAGERY DEPICTS
SLIGHTLY IMPROVED CONSOLIDATION WITH A CENTRAL DENSE OVERCAST
FEATURE EVIDENT. A 140903Z SSMIS IMAGE INDICATES IMPROVED
CONVECTIVE BANDING OVER THE WESTERN SEMI-CIRCLE ALTHOUGH THE
BULK OF THE DEEP CONVECTION REMAINS OVER THE EASTERN SEMI-CIRCLE.
THERE IS GOOD CONFIDENCE IN THE CURRENT POSITION BASED ON THE WELL-
DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC) EVIDENT IN THE 140903Z
IMAGE AS WELL AS IN A 141110Z SSMIS 37H IMAGE. THE CURRENT
INTENSITY IS ASSESSED AT 60 KNOTS BASED ON AN AVERAGE OF DVORAK
ESTIMATES RANGING FROM 55 TO 65 KNOTS FROM KNES AND PGTW AS WELL
AS EARLIER (140436Z) AIRCRAFT RECONNAISSANCE DATA INDICATING 62
KNOT MAXIMUM SUSTAINED WINDS; RJTD IS CURRENTLY AT 50 KNOTS (T3.0).
OVERALL, UPPER-LEVEL OUTFLOW IS GOOD WITH THE EXCEPTION OF SOME
PRESSURE ON THE WEST SIDE RESULTING FROM THE CLOSE PROXIMITY OF
AN ANTICYCLONE NEAR 10N 130E, ASSOCIATED WITH A WEAK TROPICAL
DISTURBANCE. THIS DISTURBANCE MAY ALSO BE DISRUPTING LOW-LEVEL
INFLOW OVER THE SOUTHWEST QUADRANT. 
3. FORECAST REASONING.
   A. NO CHANGE SINCE THE 140300Z BULLETIN.
   B. TS 15W IS CURRENTLY TRACKING ALONG THE SOUTHWEST PERIPHERY OF
THE MID-LEVEL SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTHEAST
TOWARD A WEAKNESS PRODUCED BY A MAJOR MIDLATITUDE SHORT-WAVE TROUGH
SITUATED OVER NORTHEAST ASIA. THIS TROUGH IS EXPECTED TO FILL AND
PROPAGATE NORTHEASTWARD, WHICH WILL ALLOW THE STR TO BUILD NORTH OF
THE SYSTEM PROVIDING A WESTWARD STEERING INFLUENCE. AVAILABLE MODEL
GUIDANCE IS TIGHTLY-CLUSTERED THEREFORE THE FORECAST IS IN CLOSE
AGREEMENT WITH THE MODEL CONSENSUS. TS 15W IS FORECAST TO INTENSIFY
AT A 15-25 KNOT PER DAY RATE THROUGH TAU 48 WITH RAPID
INTENSIFICATION LIKELY AFTER TAU 24 DUE TO IMPROVING OUTFLOW. 
   C. AFTER TAU 72, TS 15W IS FORECAST TO CONTINUE TRACKING WESTWARD
AND SHOULD MAKE LANDFALL OVER LUZON BY TAU 96. MODEL GUIDANCE IS
TIGHTLY-CLUSTERED THROUGH TAU 120. TS 15W IS EXPECTED TO PEAK AT
120 KNOTS BY TAU 96 AND SHOULD WEAKEN CONSIDERABLY AFTER CROSSING
THE MOUNTAINOUS REGION OF LUZON AND RE-EMERGE INTO THE SOUTH CHINA
SEA AT 80-90 KNOTS.// 
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