Tropical Storm PEIPAH Advisory Sun Apr 06

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 05W (PEIPAH)
WARNING NR 15//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 05W (PEIPAH), LOCATED APPROXIMATELY
25 NM EAST-SOUTHEAST OF KOROR, PALAU, HAS TRACKED NORTHWESTWARD
AT 12 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED
SATELLITE IMAGERY DEPICTS THE DEEP CONVECTION SHEARED TO THE
NORTHWEST OF A WEAK DEVELOPING LOW-LEVEL CIRCULATION CENTER (LLCC).
A 061212Z METOP-B MICROWAVE IMAGE REVEALS FRAGMENTED CONVECTIVE
BANDING OVER THE NORTHERN SEMI-CIRCLE WRAPPING INTO A DEFINED
CENTER. THE CURRENT INTENSITY OF 30 KNOTS IS BASED ON A 061212Z
ASCAT PASS SHOWING A 25 TO 30 KNOT CIRCULATION AS WELL AS DVORAK
CURRENT INTENSITY ESTIMATES FROM PGTW AND RJTD. THE CURRENT POSITION
IS BASED ON THE ABOVE ASCAT IMAGE WITH HIGH CONFIDENCE. TD 05W
CONTINUES TO TRACK WEST-NORTHWESTWARD ALONG THE SOUTHERN PERIPHERY
OF A DEEP-LAYERED SUBTROPICAL STEERING RIDGE TO THE NORTH. ALTHOUGH
WARM SEA SURFACE TEMPERATURE (SST) IS CONDUCIVE FOR DEVELOPMENT,
UPPER-LEVEL ANALYSIS INDICATES THE SYSTEM REMAINS SOUTH OF THE UPPER-
LEVEL SUBTROPICAL RIDGE AXIS UNDER THE INFLUENCE OF MODERATE TO
STRONG (2O TO 30 KNOT) EASTERLY VERTICAL WIND SHEAR AND MAY STRUGGLE
TO ESTABLISH A STRONG OUTFLOW MECHANISM.
3. FORECAST REASONING.
   A. THE SYSTEM HAS STRUGGLED TO STAY VERTICALLY STACKED AND IS NOW
UNDER SIGNIFICANT SHEAR, EXPOSING THE LLCC. DUE TO THIS AS WELL AS
CHANGES TO STATISTICAL-DYNAMICAL INTENSITY GUIDANCE, FORECAST
INTENSITIES HAVE BEEN REDUCED FROM THE PREVIOUS WARNING.
   B. TS 05W IS FORECAST TO TRACK WEST-NORTHWESTWARD UNDER THE
CONTINUED INFLUENCE OF THE SUBTROPICAL STEERING RIDGE THROUGHOUT THE
FORECAST PERIOD. MINIMAL INTENSIFICATION MAY OCCUR AS THE SYSTEM
TRACKS OVER FAVORABLE SST AND IMPROVING WESTWARD DIFFLUENCE ALOFT
OFFSET THE NEGATIVE INFLUENCE OF PERSISTENT EASTERLY VERTICAL WIND
SHEAR.
   C. THE MINIMAL INTENSIFICATION TREND WILL BE DISRUPTED AFTER TAU
72 AS THE SYSTEM MOVES OVER LAND, ALTHOUGH VERTICAL WIND SHEAR IS
EXPECTED TO RELAX SLIGHTLY AND POLEWARD OUTFLOW IMPROVE DURING THE
SAME PERIOD AS A MIDLATITUDE SHORTWAVE TROUGH PASSES TO THE NORTH.
EVEN THOUGH NUMERICAL MODEL TRACK GUIDANCE INDICATES A 170 NM SPREAD
AT TAU 72, BUT IT REMAINS OVERALL IN GOOD AGREEMENT LENDING HIGH
CONFIDENCE IN THE JTWC TRACK FORECAST WHICH IS POSITIONED CLOSE TO
MULTI-MODEL CONSENSUS.//
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