Tropical Storm DAMREY Advisory Sat Jul 28

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 11W (DAMREY)
WARNING NR 01//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION 11W (DAMREY), LOCATED APPROXIMATELY 245 NM
EAST-NORTHEAST OF IWO-TO, JAPAN, HAS TRACKED WEST-NORTHWESTWARD AT
04 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY DEPICTS A PARTIALLY-EXPOSED LOW-LEVEL CIRCULATION CENTER
(LLCC) POSITIONED ALONG THE NORTHWESTERN EDGE OF A LARGE AREA OF
DEEP CONVECTION.  A 282043Z WINDSAT 37H IMAGE DEPICT A CONSOLIDATING
LLCC WITH MULTIPLE BANDS WRAPPING INTO A DEFINED CENTER. RECENT
SCATTEROMETER DATA SUPPORTS THE INITIAL INTENSITY ASSESSMENT OF 30
KNOTS. ADDITIONALLY, A SHIP REPORT AT 28/18Z (175 NM WNW) INDICATES
24 KNOT NORTHEASTERLY WINDS SUPPORTING THE RECENT CONSOLIDATION. TD
11W IS LOCATED WITHIN A MARGINAL UPPER-LEVEL ENVIRONMENT
CHARACTERIZED BY MODERATE, NORTHWESTERLY VERTICAL WIND SHEAR (VWS)
AND CONVERGENT FLOW OVER THE NORTHERN SEMI-CIRCLE. THEREFORE, THE
BULK OF THE DEEP CONVECTION IS SHEARED OVER THE EASTERN SEMI-CIRCLE.
TD 11W IS POSITIONED SOUTH OF A COL REGION PRODUCED BY AN UPPER-
LEVEL MIDLATITUDE SHORT-WAVE TROUGH DIGGING EAST OF JAPAN, AND IS,
THEREFORE, TRACKING SLOWLY WESTWARD. THERE IS GOOD CONFIDENCE IN THE
CURRENT POSITION BASED ON THE WINDSAT IMAGE.
3. FORECAST REASONING.
   A. THIS IS THE INITIAL PROGNOSTIC REASONING AND SETS THE FORECAST
PHILOSOPHY.
   B. TD 11W IS FORECAST TO CONTINUE TRACKING SLOWLY WESTWARD
THROUGH TAU 36 AND IS ALSO EXPECTED TO INTENSIFY SLOWLY WITHIN THAT
SAME TIME PERIOD DUE TO THE MARGINAL ENVIRONMENT. AFTER TAU 36, TD
11W IS EXPECTED TO ACCELERATE AS THE SHORT-WAVE TROUGH PROPAGATES
EASTWARD AND THE SUBTROPICAL STEERING RIDGE STRENGTHENS. DYNAMIC
MODEL GUIDANCE IS IN GOOD OVERALL AGREEMENT THROUGH TAU 72 ALTHOUGH
GFDN SHOWS ONLY A 36-HOUR TRACK AND WEAKENS THE SYSTEM. NOGAPS
APPEARS TO BE TOO SLOW AS IT ERRONEOUSLY INTERACTS 11W WITH 10W AND
SHOWS A MORE ERRATIC TRACK. THE JTWC FORECAST IS POSITIONED
EQUATORWARD AND FASTER THAN THE MODEL CONSENSUS TO OFFSET NOGAPS AND
GFDN. THE JTWC FORECAST ALSO FAVORS THE ECMWF, JGSM, UKMO AND GFS
SOLUTIONS, WHICH SHOW A FASTER TRACK TOWARD SHANGHAI. TD 11W IS
FORECAST TO REACH A PEAK INTENSITY OF 45 KNOTS DUE TO THE MARGINALLY-
FAVORABLE CONDITIONS.
   C. IN THE EXTENDED TAUS, TD 11W IS EXPECTED TO WEAKEN DUE IN
LARGE PART TO THE PROXIMITY OF THE MUCH LARGER AND STRONGER 10W NEAR
TAIWAN, WHICH SHOULD INCREASE VERTICAL WIND SHEAR AND DISRUPT
OUTFLOW. TD 11W IS EXPECTED TO MAKE LANDFALL BY TAU 120. THERE IS
STILL A SLIGHT POSSIBILITY OF SOME WEAK INTERACTION AS THE TWO
SYSTEMS APPROACH TO ABOUT 500 NM BY 01/18Z; HOWEVER, SIGNIFICANT
BINARY INTERACTION IS NOT FORECAST AT THIS TIME.//
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