Tropical Storm PEIPAH Advisory 07 Απρ.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 05W (PEIPAH)
WARNING NR 16//
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. THE CURRENT POSITION IS BASED ON A
RECENT PGTW SATELLITE FIX, A 061701Z AMSU PASS, AND SYNOPTIC
OBSERVATIONS FROM KOROR. THE INTENSITY OF 30 KNOTS IS CONSISTENT
WITH DVORAK CURRENT INTENSITY ESTIMATES FROM PGTW AND RJTD AND
OBSERVATIONS FROM KOROR. MOST DEEP CONVECTION ASSOCIATED WITH TD 05W
REMAINS SHEARED WELL TO THE WEST OF THE EXPOSED LOW LEVEL
CIRCULATION CENTER DUE TO STRONG EASTERLY FLOW ALOFT. THE SYSTEM
CONTINUES TO TRACK GENERALLY WESTWARD ALONG THE SOUTHERN PERIPHERY
OF A ZONALLY-ORIENTED SUBTROPICAL RIDGE TO THE NORTH.
3. FORECAST REASONING.
   A. DUE TO PERSISTENT VERTICAL WIND SHEAR AND TRENDS IN
STATISTICAL-DYNAMICAL INTENSITY GUIDANCE, FORECAST INTENSITIES HAVE
BEEN REDUCED FROM THE PREVIOUS WARNING. TRACK SPEEDS HAVE ALSO BEEN
REDUCED FOR THE TAU 36 TO TAU 72 PERIOD CONSISTENT WITH A SLOWDOWN
IN CONSENSUS TRACK GUIDANCE.
   B. TD 05W IS FORECAST TO TRACK WEST-NORTHWESTWARD UNDER THE
CONTINUED INFLUENCE OF THE SUBTROPICAL STEERING RIDGE. SIGNIFICANT
INTENSIFICATION DURING THE FORECAST PERIOD IS UNLIKELY. HOWEVER, A
SLIGHT RELAXATION OF VERTICAL WIND SHEAR AND IMPROVED POLEWARD
OUTFLOW INDUCED BY A MIDLATITUDE TROUGH PASSING TO THE NORTH MAY
ENABLE TD 05W TO MINIMALLY INTENSIFY AROUND TAU 48. DISSIPATION IN
THE NEAR TO MEDIUM TERM IS ALSO POSSIBLE, ALTHOUGH IT APPEARS AT
THIS POINT THAT SUFFICIENT UPPER LEVEL OUTFLOW AND PASSAGE OVER WARM
WATER WILL ALLOW THE SYSTEM TO MAINTAIN INTENSITY AT OR ABOVE THE
WARNING THRESHOLD OF 25 KNOTS.
   C. TD 05W WILL MOVE OVER LAND AND WEAKEN AFTER TAU 72. THERE IS
GENERALLY GOOD AGREEMENT AMONG NUMERICAL MODELS REGARDING TRACK
DIRECTION, BUT A FEW MODELS INCLUDING GFS AND ECMWF NOW SUGGEST A
PRONOUNCED SLOWING OF TRACK MOTION BETWEEN TAU 36 AND TAU 48 AS THE
AFOREMENTIONED MIDLATITUDE TROUGH PASSES TO THE NORTH. HOWEVER,
MODEL FORECAST AGREEMENT IS CLOSE ENOUGHT TO LEND HIGH CONFIDENCE TO
THE JTWC TRACK FORECAST TRACK.//
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