Tropical Storm PEIPAH Advisory mer, 09.04.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 05W (PEIPAH)
WARNING NR 25//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 05W (PEIPAH), LOCATED APPROXIMATELY 672
NM SOUTHEAST OF MANILA, PHILIPPINES, HAS TRACKED NORTHWESTWARD AT
03 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY (MSI) DEPICTS A BROAD LOW-LEVEL CIRCULATION CENTER (LLCC)
WITH MULTIPLE VORTICES ROTATING ABOUT A CENTROID (WHICH IS THE
INITIAL POSITION). MSI SHOWS A WEAK VORTICE NEAR 7.3N 131.4E, WHICH
IS TRACKING EAST-NORTHEASTWARD AND WEAKENING OVER THE PAST SIX
HOURS. DESPITE A SLIGHT IMPROVEMENT IN CONVECTIVE STRUCTURE, THE
LLCC REMAINS BROAD AND THE CENTER REMAINS DIFFICULT TO PINPOINT. A
082300Z SSMIS IMAGE DEPICTS THE PRIMARY CURVED CONVECTIVE BAND OVER
THE NORTHERN SEMI-CIRCLE WITH WEAK BANDING OVER THE SOUTHWEST
QUADRANT AND SUPPORTS THE INITIAL POSITION WITH POOR CONFIDENCE.
BASED ON THE IMPROVED, PERSISTENT BANDING AND DVORAK INTENSITY
ESTIMATES OF 30 KNOTS, THE INITIAL INTENSITY IS ASSESSED AT 30
KNOTS. UPPER-LEVEL ANALYSIS REVEALS A MARGINAL ENVIRONMENT
CHARACTERIZED BY MODERATE (20 KNOTS) EASTERLY VERTICAL WIND SHEAR
OFFSET BY STRONG DIFFLUENCE AND GOOD POLEWARD OUTFLOW. TD 05W IS
SITUATED WITHIN A WEAK STEERING ENVIRONMENT AND IS TRACKING
ERRATICALLY BUT SLOWLY NORTHWESTWARD TOWARD A BREAK IN THE
SUBTROPICAL RIDGE.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TD 05W IS FORECAST TO REMAIN IN THE WEAK STEERING ENVIRONMENT
THROUGH TAU 36 BUT IS FORECAST TO TRACK SLOWLY NORTHWESTWARD TOWARD
THE WEAKNESS IN THE SUBTROPICAL RIDGE (STR). DYNAMIC GUIDANCE IS IN
FAIR AGREEMENT WITH SOLUTIONS INDICATING NORTHWESTWARD TRACKS,
HOWEVER, GFS AND ECMWF NOW SHOW A QUASI-STATIONARY TRACK THROUGH TAU
48. THE JTWC FORECAST TRACK ALSO REFLECTS A VERY SLOW TRACK THROUGH
TAU 48 AND IS POSITIONED CLOSE TO THE MULTI-MODEL CONSENSUS. TD 05W
SHOULD SLOWLY INTENSIFY TO A PEAK OF 35 KNOTS BY TAU 36 AS THE TRACK
SPEEDS INCREASE AND AS THE SYSTEM TRACKS INTO LOWER VERTICAL WIND
SHEAR WHILE MAINTAINING ROBUST POLEWARD OUTFLOW.
   C. IN THE EXTENDED TAUS, TD 05W IS EXPECTED TO TURN WEST-
NORTHWESTWARD AND TO ACCELERATE AS THE STR RE-BUILDS NORTH OF THE
SYSTEM. 05W SHOULD WEAKEN GRADUALLY PRIOR TO TRACKING OVER THE
PHILIPPINES AND IS FORECAST TO DISSIPATE BY TAU 96. DUE TO THE
UNCERTAINTY IN THE INITIAL POSITION AND SHORT-TERM MOTION AS WELL AS
MAJOR TRACK SPEED DIFFERENCES BETWEEN THE DYNAMIC MODELS, THERE IS A
HIGH DEGREE OF UNCERTAINTY AND, CONSEQUENTLY, LOW CONFIDENCE IN THE
JTWC TRACK FORECAST.//
NNNN
NNNN