Tropical Storm MEKKHALA Advisory 8月9日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 07W (SEVEN) WARNING
NR 001//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL DEPRESSION (TD) 07W (SEVEN), LOCATED APPROXIMATELY
204 NM NORTHWEST OF MANILA, PHILIPPINES, HAS TRACKED NORTHWARD AT
10 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR)
SATELLITE IMAGERY DEPICTS CONSOLIDATING, DEEP CONVECTION OBSCURING A
LOW LEVEL CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS PLACED
WITH FAIR CONFIDENCE BASED ON THE LOW LEVEL FEATURES PRESENT IN A
091015Z WINDSAT 37GHZ IMAGE AND THE CIRCULATION PRESENT IN THE
COMPOSITE RADAR LOOP. THE INITIAL INTENSITY OF 30 KTS IS PLACED WITH
FAIR CONFIDENCE BASED ON A PGTW DVORAK CURRENT INTENSITY ESTIMATE OF
T1.0 (25 KTS) AND THE 30 KTS WINDS PRESENT IN THE ELONGATED AND
ASYMMETRIC WIND FIELD REFLECTED IN A 091202Z ASCAT-A PASS. TD 07W IS
TRACKING NORTHWARD ALONG THE WESTERN PERIPHERY OF A SUBTROPICAL RIDGE
(STR) AND THROUGH A MARGINALLY FAVORABLE ENVIRONMENT FOR DEVELOPMENT
WITH WARM (30-31 CELSIUS) SEA SURFACE TEMPERATURES (SST) AND MODERATE
EQUATORWARD AND POLEWARD OUTFLOW ALOFT OFFSET BY MODERATE (10-15 KTS)
VERTICAL WIND SHEAR (VWS).
3. FORECAST REASONING.
   A. THIS IS THE FIRST PROGNOSTIC REASONING MESSAGE AND SETS THE
FORECAST PHILOSOPHY.
   B. TD 07W IS FORECAST TO CONTINUE TRACKING NORTHWARD ALONG THE
WESTERN PERIPHERY OF A SUBTROPICAL RIDGE POSITIONED TO THE EAST AS IT
TRACKS TOWARDS THE TAIWAN STRAIT. CONTINUED WARM (29-30 CELSIUS) SSTS
WILL SUPPORT INTENSIFICATION TO 35 KTS BY TAU 12 AND TO A MAXIMUM
INTENSITY OF 40 KTS BY TAU 24, HOWEVER THE ENVIRONMENT WILL BECOME
INCREASINGLY UNFAVORABLE DURING THIS TIME WITH INCREASING VWS AND
CONVERGENT FLOW FROM AN INDUCED UPPER LEVEL TROUGH POSITIONED OVER THE
TAIWAN STRAIGHT. THIS CONVERGENCE AND HIGH (25-30 KTS) VWS WILL HINDER
INTENSIFICATION AND LEAD TO GRADUAL WEAKENING TO 35 KTS BY TAU 36 AS
THE SYSTEM BEGINS DISSIPATION OVER WATER. TD 07W WILL MAKE LANDFALL
OVER MAINLAND CHINA AFTER TAU 36 WHEREUPON IT WILL WEAKEN DUE TO THE
FRICTIONAL EFFECTS OF LAND AND DISSIPATE OVER LAND BY TAU 48. THERE IS
A LARGE SPREAD IN NUMERICAL MODEL SOLUTIONS WITH A 200 NM CROSS TRACK
SPREAD IN POSITIONS AT TAU 48. THIS LARGE SPREAD OF THE CROSS TRACK
NUMERICAL MODEL SOLUTIONS LENDS ONLY FAIR CONFIDENCE TO THE OVERALL
JTWC FORECAST TRACK.//
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