MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 11W (NANGKA)
WARNING NR 58//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL DEPRESSION (TD) 11W (NANGKA), LOCATED APPROXIMATELY 232
NM WEST-NORTHWEST OF YOKOTA AB, HAS TRACKED NORTH-NORTHEASTWARD AT
09 KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE
IMAGERY DEPICTS RAPIDLY DECAYING CONVECTION ASSOCIATED WITH A BROAD
LOW-LEVEL CIRCULATION CENTER (LLCC). A 171740Z NOAA19 89 GHZ IMAGE
INDICATES A BROADLY-DEFINED LLCC WITH WITH FRAGMENTED, SHALLOW
BANDING. DUE TO THE WEAK NATURE OF THE SYSTEM, THERE IS FAIR
CONFIDENCE IN THE CURRENT POSITION. THE INITIAL INTENSITY IS
ASSESSED AT 30 KNOTS BASED ON DVORAK INTENSITY ESTIMATES OF 30 KNOTS
FROM RJTD, WHICH IS CONSISTENT WITH THE CONVECTIVE STRUCTURE. UPPER-
LEVEL ANALYSIS INDICATES THAT THE SYSTEM IS EMBEDDED WITHIN
SUBTROPICAL SOUTHWESTERLY FLOW WITH MODERATE VERTICAL WIND SHEAR. TD
11W IS CURRENTLY TRACKING ALONG THE NORTHWESTERN PERIPHERY OF THE
STR. CURRENTLY, THE BAROCLINIC ZONE IS WEAK AND IS DISPLACED WELL TO
THE NORTH, THEREFORE, THE SYSTEM IS NOT UNDERGOING EXTRA-TROPICAL
TRANSITION (ETT).
3. FORECAST REASONING.
A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
B. TD NANGKA WILL CONTINUE TRACKING NORTHEASTWARD THROUGH THE
FORECAST PERIOD AS IT CONTINUES TO TRACK WITHIN VIGOROUS SUBTROPICAL
SOUTHWESTERLY FLOW, POLEWARD OF THE STR. DYNAMIC GUIDANCE IS IN
TIGHT AGREEMENT AND SUPPORTS THE FORECAST TRACK WITH HIGH
CONFIDENCE. TD 11W IS FORECAST TO GRADUALLY WEAKEN AS IT TRACKS OVER
NORTHERN HONSHU AND WILL DISSIPATE BY TAU 36.//
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