Tropical Storm DANAS Advisory 18 Ιουλ.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 06W (DANAS) WARNING NR
07//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM (TS) 06W (DANAS), LOCATED APPROXIMATELY 253 NM SOUTH-
SOUTHEAST OF TAIPEI, TAIWAN, HAS TRACKED NORTHWARD AT 11 KNOTS OVER
THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE
IMAGERY SHOWS A PARTIALLY EXPOSED LOW LEVEL CIRCULATION (LLC) WITH
THE WEAK AND POORLY ORGANIZED CENTRAL CONVECTION SHEARED EASTWARD OF
THE LLC. THE INITIAL POSITION IS PLACED WITH GOOD CONFIDENCE BASED ON
THE LLC FEATURE IN THE EIR LOOP. THE INITIAL INTENSITY OF 35 KNOTS IS
HELD SLIGHTLY HIGHER THAN AGENCY DVORAK ESTIMATES OF T2.0/30KTS AND
MORE IN LINE WITH SATCON AT T2.5/35KTS AND REFLECTS THE SUSTAINED EIR
CONVECTIVE SIGNATURE OF THE SYSTEM. UPPER LEVEL ANALYSIS INDICATES
THE CYCLONE IS IN AN AREA OF MODERATE VERTICAL WIND SHEAR (VWS) AND
SUBSIDENCE ALONG THE NORTHWEST QUADRANT CAUSED BY AN INDUCED
MID-LATITUDE TROUGH OVER TAIWAN. HOWEVER, MODERATE NORTHEASTWARD OUTFLOW
AND WARM SEA SURFACE TEMPERATURES (SSTS AT 30C) ARE PROVIDING
VENTILATION AND FUEL TO THE STRUGGLING CONVECTION. TS 06W IS TRACKING
ALONG THE WESTERN PERIPHERY OF A SUBTROPICAL RIDGE (STR) TO THE EAST.
3. FORECAST REASONING.
   A. THIS FORECAST NOW CALLS FOR DISSIPATION BY TAU 96, OTHERWISE,
THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TS 06W WILL CONTINUE TRACKING POLEWARD THROUGH TAU 24 BEFORE
BEGINNING A NORTHEASTWARD TURN AS IT ROUNDS THE STR AXIS. THE
MARGINAL ENVIRONMENT WILL PROMOTE SLIGHT INTENSIFICATION TO 40 KNOTS
AT TAUS 12-36. AFTERWARD, COOLING SSTS AND INCREASING VWS WILL
GRADUALLY WEAKEN THE SYSTEM AND BY TAU 72, WILL BE REDUCED TO A
30-KNOT DEPRESSION AS IT APPROACHES BUSAN, SOUTH KOREA. NUMERICAL
MODELS ARE IN TIGHT AGREEMENT, LENDING HIGH CONFIDENCE TO THIS
PORTION OF THE JTWC FORECAST.
  C. BEYOND TAU 72, LAND INTERACTION WITH THE RUGGED TERRAIN OF SOUTH
KOREA, IN ADDITION TO THE DEGRADED ENVIRONMENT DISCUSSED IN PARA 3.B,
WILL LEAD TO DISSIPATION BY TAU 96 IN THE SEA OF JAPAN, POSSIBLY
SOONER. NUMERICAL MODELS SIGNIFICANTLY DIVERGE BEYOND TAU 72; GIVEN
THIS, PLUS THE ANTICIPATED ERRATIC MOTION OF THE WEAKENED TC AS IT
TRACKS ACROSS RUGGED TERRAIN, LEND LOW CONFIDENCE TO THE EXTENDED
PORTION OF THE JTWC TRACK FORECAST.//
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