Tropical Storm PEIPAH Advisory lun, 07-04

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 05W (PEIPAH)
WARNING NR 17//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION 05W (PEIPAH), LOCATED APPROXIMATELY 61 NM
WEST OF KOROR, HAS TRACKED WESTWARD AT 11 KNOTS OVER THE PAST
SIX HOURS. THE CURRENT POSITION IS BASED ON RECENT ANIMATED
MULTISPECTRAL SATELLITE IMAGERY AND A 062324Z SSMIS PASS. THE
INTENSITY OF 25 KNOTS IS CONSISTENT WITH A DVORAK CURRENT INTENSITY
ESTIMATE FROM PGTW AND STRUCTURE EVIDENT IN VISIBLE AND MICROWAVE
SATELLITE IMAGERY. DEEP CONVECTION ASSOCIATED WITH TD 05W REMAINS
CONFINED TO THE WESTERN PORTION OF THE LOW LEVEL CIRCULATION CENTER
(LLCC) DUE TO STRONG EASTERLY VERTICAL WIND SHEAR. THE SYSTEM IS
TRACKING 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
AGAIN BEEN REDUCED FROM THE PREVIOUS WARNING. TRACK SPEEDS HAVE ALSO
BEEN REDUCED FOR THE TAU 72 TO TAU 120 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 THROUGHOUT THE
FORECAST PERIOD. THE MAJORITY OF THE NUMERICAL MODEL GUIDANCE
SUPPORTS THIS SCENARIO, ALTHOUGH THE LATEST UKMET AND GFS RUNS
SUGGEST THAT TD 05W MAY STALL AND TURN POLEWARD AFTER TAU 36. ECMWF
ALSO INDICATES A NEAR STALL AROUND TAU 36, BUT A WESTWARD TRACK
RESUMES IN LATER FORECAST TAUS. THE CURRENT FORECAST FAVORS A
GENERALLY WESTWARD TRACK GIVEN ANALYSIS OF CONTINUOUS RIDGING TO THE
NORTH AND THE PREPONDERANCE OF MODEL GUIDANCE IN SUPPORT OF THAT
SCENARIO. TD 05W SYSTEM IS EXPECTED TO MAINTAIN INTENSITY IN THE
NEAR TERM, BUT MAY INTENSIFY VERY SLIGHTLY AROUND TAU 36 DUE TO A
MINIMAL RELAXATION OF VERTICAL WIND SHEAR AND IMPROVED POLEWARD
OUTFLOW INDUCED BY A MIDLATITUDE TROUGH PASSING TO THE NORTH.
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 IS EXPECTED TO CONTINUE WEST-NORTHWESTWARD INTO
NORTHERN MINDANAO IN THE EXTENDED FORECAST PERIOD. CONSENSUS MODEL
GUIDANCE IS IN GENERALLY GOOD AGREEMENT WITH THE CURRENT FORECAST
TRACK, EXCEPT FOR THE AFOREMENTIONED POLEWARD TREND IN RECENT UKMET
AND GFS GUIDANCE. DUE TO THIS DIVERGENCE IN THE MODEL GUIDANCE,
CONFIDENCE IN THE CURRENT JTWC TRACK FORECAST IS LOW.//
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