Tropical Storm TEMBIN Advisory Sun Aug 19

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 15W (TEMBIN) WARNING NR
03//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 15W (TEMBIN), LOCATED APPROXIMATELY 285 NM
NORTHEAST OF MANILA, PHILIPPINES, HAS TRACKED EAST-SOUTHEASTWARD AT
02 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED
SATELLITE IMAGERY (EIR) SHOWS A SIGNIFICANT IMPROVEMENT IN THE
OVERALL STRUCTURE OF THE LOW LEVEL CIRCULATION CENTER (LLCC). DEEP
CONVECTIVE BANDING CONTINUES TO ENCOMPASS THE ENTIRE LLCC. THE
CURRENT INTENSITY OF 45 KNOTS IS BASED ON 3.0/3.0 DVORAKS FROM PGTW,
RJTD, AND KNES. THE CURRENT POSITION IS BASED ON THE EIR LOOP
TRACKING THE PREVIOUSLY IDENTIFIABLE LLCC. THE LLCC HAS BECOME CLOUD
FILLED OVER THE PAST SIX HOURS. THERE REMAINS GOOD CONFIDENCE IN THE
POSITION BASED ON THE WELL ORGANIZED STRUCTURE OF TS 15W. UPPER
LEVEL ANALYSIS INDICATES TS 15W IS LOCATED SEVERAL DEGREES NORTH OF
A NEAR EQUATORIAL RIDGE (NER) WITH A WEAK EXTENSION OF THE NER TO
THE EAST AND A MINOR TROPICAL UPPER TROPOSPHERIC TROUGH (TUTT) CELL
DEVELOPING TO THE WEST OF TS 15W, WHICH IS EVIDENT IN ANIMATED WATER
VAPOR IMAGERY. THE NER IS PROVIDING AMPLE EQUATORWARD OUTFLOW WITH
INCREASING WESTWARD OUTFLOW INTO THE TUTT CELL. ADDITIONALLY, A TUTT
CELL TO THE EAST-NORTHEAST IS BEGINNING TO SUPPORT A DEVELOPING
POLEWARD OUTFLOW CHANNEL. TS 15W REMAINS IN A WEAK STEERING
ENVIRONMENT AND HAS BEEN ON A SLOW YET STEADY TRACK FOR THE PAST SIX
HOURS.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE PREVIOUS PROGNOSTIC REASONING.
   B. TS 15W IS FORECAST TO REMAIN IN A WEAK STEERING ENVIRONMENT
OVER THE NEXT 12 TO 24 HOURS AS A NER TO THE SOUTHEAST OF TS 15W
BEGINS TO BUILD NORTHWESTWARD CAUSING THE SYSTEM TO START TRACKING
NORTHWARD. AS TS 15W MOVES NORTHWARD, THE SOUTHWESTERN EXTENT OF A
DEEP LAYERED SUBTROPICAL RIDGE (STR) LOCATED EASTWARD OF HONSHU,
JAPAN WILL CAUSE A SLIGHT NORTHWESTWARD SHIFT BETWEEN TAU 36 AND 48.
THE WESTWARD TURN WILL BECOME MORE PRONOUNCED BETWEEN TAU 48 AND 72.
STEADY INTENSIFICATION IS EXPECTED WITHIN A FAVORABLE ENVIRONMENT AS
SEA SURFACE TEMPERATURES REMAIN ABOVE 28 CELSIUS, WITH IMPROVING
UPPER LEVEL OUTFLOW CHANNELS VENTING THE SYSTEM AND VERTICAL WIND
SHEAR REMAINING LOW (5 TO 10 KNOTS).
   C. IN THE EXTENDED FORECAST TS 15W WILL CONTINUE TRACKING
WESTWARD ALONG THE SOUTHWESTERN PERIPHERY OF THE STR, MAKING
LANDFALL IN TAIWAN SLIGHTLY BEFORE TAU 96. TRACKING OVER TAIWAN, THE
SYSTEM IS EXPECTED TO BE WITHIN THE TAIWAN STRAIT SHORTLY AFTER TAU
96. INTENSITY IS FORECAST TO DECREASE AS IT TRACKS OVER TAIWAN,
EMERGING AS A STRONG TROPICAL STORM. DYNAMIC MODEL GUIDANCE HAS COME
INTO A WELL ORGANIZED GROUPING WITH EGRR BEING THE SINGULAR OUTLIER
TO THE SOUTH. NGPS HAS COME INTO ALIGNMENT WITH GFS, ECMWF, AND
GFDN. THE CURRENT FORECAST IS BASED PREDOMINANTLY ON THE CONSENSUS
NOW THAT THE MAJORITY OF THE MODELS HAVE COME INTO GOOD AGREEMENT.
BASED ON THE QUESTIONABLE TIMING FOR THE NER TO BEGIN THE NORTHWARD
PUSH OF TS 15W, THERE REMAINS LOW CONFIDENCE IN THE TIMING, HOWEVER
WITH THE MODEL GUIDANCE SHOWING A PERSISTENT TRACK SOLUTION OVER THE
PAST 12 HOURS THERE IS HIGH CONFIDENCE IN THE TRACK PHILOSOPHY.//
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