Tropical Storm PEIPAH Advisory mar, 08.04.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 05W (PEIPAH)
WARNING NR 21//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 05W (PEIPAH), LOCATED APPROXIMATELY 759
NM SOUTHEAST OF MANILA, PHILIPPINES, HAS TRACKED NORTHWESTWARD AT 04
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY DEPICTS AN OBSCURED, SLOWLY-CONSOLIDATING LOW-LEVEL
CIRCULATION CENTER (LLCC) WITH THE BULK OF THE DEEP CONVECTION
SHEARED WEST AND NORTHWEST OF THE LLCC. A 072312Z SSMIS IMAGE SHOWS
WEAK, FRAGMENTED CONVECTIVE BANDING WRAPPING INTO A WEAKLY DEFINED
LLCC. DESPITE THE WEAK CONVECTIVE STRUCTURE, A 080028Z ASCAT IMAGE
DEPICTS A SYMMETRIC CIRCULATION WITH A WEAK CORE OF WINDS SURROUNDED
BY NUMEROUS 25 TO 30 KNOT WIND BARBS, PRIMARILY OVER THE NORTHERN
SEMI-CIRCLE. UPPER-LEVEL ANALYSIS REVEALS A MARGINAL ENVIRONMENT
CHARACTERIZED BY MODERATE TO STRONG (20 TO 30 KNOTS) EASTERLY
VERTICAL WIND SHEAR OFFSET BY STRONG DIFFLUENCE AND GOOD POLEWARD
OUTFLOW. BASED ON THE ASCAT IMAGE, THERE IS FAIR CONFIDENCE IN THE
INITIAL POSITION. THE INITIAL INTENSITY IS ASSESSED AT 30 KNOTS
BASED ON DVORAK ESTIMATES OF 3O KNOTS FROM KNES, RJTD AND PGTW, AS
WELL AS ASCAT DATA. TD 05W IS SITUATED WITHIN A WEAK STEERING
ENVIRONMENT AND HAS TRACKED ERRATICALLY AND SLOWLY OVER THE PAST 12
HOURS.
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 48 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 TO NORTHWARD
TRACKS. THE JTWC FORECAST TRACK IS POSITIONED CLOSE TO THE MULTI-
MODEL CONSENSUS. TD 05W SHOULD MAINTAIN INTENSITY THROUGH TAU 36
WITH A GRADUAL INCREASE TO 40 KNOTS BY TAU 72 AS THE TRACK SPEEDS
INCREASE AND AS THE SYSTEM TRACKS INTO LOWER VERTICAL WIND SHEAR
WITH 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. DUE TO THE UNCERTAINTY IN THE INITIAL POSITION AS WELL
AS MAJOR TRACK AND TRACK SPEED DIFFERENCES BETWEEN THE DYNAMIC
MODELS, THERE IS LOW CONFIDENCE IN THE JTWC TRACK FORECAST.//
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