WDPN32 PGTW 151500
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 19W (SONGA) WARNING NR 
04//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
   A. TROPICAL STORM 19W (SONCA), LOCATED APPROXIMATELY 760 NM 
EAST OF IWO TO, JAPAN, HAS TRACKED NORTH-NORTHWESTWARD AT 09 KNOTS 
OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE IMAGERY SHOWS 
THE CONVECTIVE BANDS AROUND THE LOW LEVEL CIRCULATION CENTER (LLCC) 
RELAXING AND CLOUD TOPS WARMING DURING THE PAST SIX HOURS. A TONGUE 
OF DRY AIR HAS WRAPPED INTO THE LLCC AND IS ELONGATING THE LOW 
LEVELS OF THE STORM. THE INTENSITY ANALYSIS HAS BEEN LOWERED TO 35 
KNOTS BASED ON FALLING DVORAK ASSESSMENTS FROM MULTIPLE AGENCIES. A 
150944Z SSMIS IMAGE ALSO REVEALS AN ELONGATION OF THE LLCC. ANIMATED 
WATER VAPOR IMAGERY REVEALS THE OUTFLOW FROM TS 19W IS STRONGLY 
IMPINGING ON THE WESTERN HALF OF THE STORM, BUT IT ALSO SHOWS A WELL-
DEVELOPED POLEWARD OUTFLOW CHANNEL OVER THE NORTHEASTERN QUADRANT. 
THE 150000Z UPPER LEVEL STREAMLINE ANALYSIS SHOWS THAT TS 19W EXISTS 
IN A HIGHLY DIFFLUENT REGION, WITH A TUTT CELL DIRECTLY NORTH OF THE 
SYSTEM. THE TUTT IS AIDING POLEWARD OUTFLOW OVER THE NORTHEAST 
QUADRANT. VERTICAL WIND SHEAR IS APPROXIMATELY 15 KNOTS AND SEA 
SURFACE TEMPERATURE IS 29 DEGREES. TS 19W HAS TURNED TO THE 
NORTHWEST AND IS NOW BEING STEERED BY THE SUBTROPICAL RIDGE. 
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE 
PREVIOUS PROGNOSTIC REASONING BULLETIN.
   B. THE SUBTROPICAL RIDGE WILL GUIDE THE SYSTEM NORTHWESTWARD 
UNTIL IT CRESTS THE RIDGE AXIS NEAR 33 DEGREES NORTH LATITUDE, AT 
APPROXIMATELY TAU 60. AT THAT POINT THE STORM WILL BEGIN ITS TURN 
AROUND THE RIDGE AND INTO THE MID-LATITUDES. VERTICAL WIND SHEAR AND 
SEA SURFACE TEMPERATURE ALONG TRACK WILL REMAIN STEADY THROUGH TAU 
48, WHILE IMPINGEMENT ON OUTFLOW OVER THE NORTHWEST QUADRANT WILL 
EASE. THUS, TS 19W WILL UNDERGO SLOW AND SLIGHT INTENSIFICATION 
THROUGH TAU 48. AS TS 19W NEARS THE RIDGE AXIS, VERTICAL WIND SHEAR 
WILL INCREASE SHARPLY AND THE STORM WILL BEGIN TO WEAKEN. MODEL 
GUIDANCE IS IN GOOD AGREEMENT ON BOTH TRACK AND INTENSITY. THE JTWC 
TRACK FORECAST STAYS CLOSE TO CONSENSUS AND SLIGHTLY ABOVE INTENSITY 
GUIDANCE.  
   C. BETWEEN TAU 72 AND 120, TS 19W WILL RE-CURVE AND ACCELERATE 
INTO THE MID-LATITUDES. THE EXTRA-TROPICAL TRANSITION PROCESS WILL 
BEGIN BY TAU 96 AND BE COMPLETED BY TAU 12O. MODEL GUIDANCE IS IN 
GOOD AGREEMENT ON BOTH TRACK AND INTENSITY. THE JTWC FORECAST STAYS 
CLOSE TO CONSENSUS.//
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