Tropical Storm WIPHA Advisory Ter, 30-07

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 08W (EIGHT)
WARNING NR 001//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 08W (EIGHT), LOCATED APPROXIMATELY 451
NM EAST-SOUTHEAST OF HANOI, VIETNAM, HAS TRACKED WEST-NORTHWESTWARD
AT 07 KNOTS (KTS) OVER THE PAST SIX HOURS. THE INITIAL POSITION,
PLACED WITH LOW CONFIDENCE USING ANIMATED ENHANCED INFRARED (EIR)
SATELLITE IMAGERY WHICH SUGGESTS A PARTIALLY EXPOSED LOW LEVEL
CIRCULATION CENTER (LLCC), IS JUST NORTH OF SUSTAINED CONVECTIVE
BANDING. THE EIR ALSO REVEALS LIMITED CONVECTIVE BANDING TO
THE NORTH OF THE LLCC. THE INITIAL INTENSITY IS BASED ON A 301400Z
METOP-C ASCAT IMAGE WHICH SHOWS 30 KT WINDS IN THE SOUTH, EAST, AND
NORTH QUADRANTS (THE PASS MOSTLY MISSED THE WEST QUADRANT). DVORAK
INTENSITY FIXES ARE T1.5 (25 KTS) AND BELOW. ENVIRONMENTAL
CONDITIONS ARE SOMEWHAT FAVORABLE WITH GOOD EQUATORWARD OUTFLOW AND
WARM (29-30 CELSIUS) SEA SURFACE TEMPERATURES, PARTIALLY OFFSET BY
MARGINAL (15-20 KT) VERTICAL WIND SHEAR AND A WEAK UPPER LEVEL LOW
RESULTING IN CONVERGENCE ALOFT JUST NORTH OF THE SYSTEM. TD 08W IS
TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF A SUBTROPICAL RIDGE
(STR).
3. FORECAST REASONING.
   A. THIS IS THE INITIAL PROGNOSTIC REASONING AND SETS THE
FORECAST
PHILOSOPHY.
   B. THROUGH TAU 72, TD 08W IS EXPECTED TO CONTINUE TRACKING ALONG
THE PERIPHERY OF THE STR, PASS OVER THE LEIZHOU PENINSULA AROUND TAU
30, ENTER THE GULF OF TONKIN NEAR TAU 36, AND MAKE LANDFALL NEAR
HANOI AROUND TAU 72. THE MARGINAL ENVIRONMENT IS EXPECTED TO LIMIT
INTENSIFICATION TO 35 KTS AT TAU 12. HOWEVER, THERE IS A POSSIBILITY
THE UPPER LEVEL LOW WILL WEAKEN AND ALLOW MORE INTENSIFICATION
BEFORE LANDFALL. BY TAU 24, SIGNIFICANT LAND INTERACTION SHOULD
INHIBIT INTENSIFICATION, BUT SMALL VARIATIONS IN THE ACTUAL TRACK
COULD LEAD TO SIGNIFICANT DIFFERENCES IN THE INTENSITY. NUMERICAL
MODEL GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 36. AFTER TAU 36,
THE UKMET MODEL DEVIATES TO THE SOUTH FROM THE OTHER MEMBERS. FOR
THIS PORTION OF THE FORECAST, THE JTWC TRACK FORECAST CLOSELY
FOLLOWS CONSENSUS WITH LOW CONFIDENCE DUE PRIMARILY TO HIGH
UNCERTAINTY IN THE INITIAL POSITION.
   C. AFTER TAU 72, TD 08W WILL CONTINUE INLAND AND DISSIPATE. THE
JTWC TRACK FORECAST IS HEDGED NORTH OF CONSENSUS TO OFFSET THE
SOUTHERN OUTLIER (UKMET) WITH LOW CONFIDENCE.//
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