Tropical Storm PEIPAH Advisory 08 Απρ.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 05W (PEIPAH)
WARNING NR 20//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 05W (PEIPAH), LOCATED APPROXIMATELY 778
NM SOUTHEAST OF MANILA, PHILIPPINES, HAS TRACKED WEST-NORTHWESTWARD
AT 04 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED
SATELLITE IMAGERY A SLOWLY-CONSOLIDATING LOW-LEVEL CIRCULATION
CENTER (LLCC) WITH THE BULK OF THE DEEP CONVECTION SHEARED WEST AND
NORTHWEST OF THE LLCC. A 071856Z TRMM IMAGE SHOWS WEAK, FRAGMENTED
CONVECTIVE BANDING WRAPPING INTO THE LLCC. UPPER-LEVEL ANALYSIS
REVEALS A MARGINAL ENVIRONMENT CHARACTERIZED BY MODERATE TO STRONG
(20 TO 30 KNOTS) EASTERLY VERTICAL WIND SHEAR OFFSET BY GOOD
DIFFLUENCE. BASED ON THE WEAK CONVECTIVE STRUCTURE, 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
AND PGTW. 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 72 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 48
WITH A SLIGHT INCREASE TO 35 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 INTENSIFY SLIGHTLY TO A PEAK INTENSITY OF 40
KNOTS 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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