Tropical Storm CHAN-HOM Advisory Wed Jul 08

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 09W (CHAN-HOM) WARNING NR 33//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 09W (CHAN-HOM), LOCATED APPROXIMATELY 393 NM
SOUTHEAST OF KADENA AB, HAS TRACKED WEST-NORTHWESTWARD AT 11 KNOTS
OVER THE PAST SIX HOURS. ANIMATED ENHANCED IR (EIR) IMAGERY SHOWS
THE SYSTEM HAS IMPROVED ITS CONVECTIVE SIGNATURE WITH A MORE WELL
DEFINED 20 NM  EYE. THE CONVECTION CONTINUES TO BE STRAINED ON THE
NORTHERN SIDE OF THE LLCC DUE TO UPPER LEVEL SUBSIDENCE WHICH CAN BE
SEEN IN THE EIR IMAGERY AS WELL AS A PARTIAL 081145Z AMSU-B IMAGE.
THE INITIAL POSITION IS BASED ON THE ABOVE IMAGERY WITH GOOD
CONFIDENCE. THE INTENSITY HAS BEEN RAISED TO 90 KNOTS AS THE EYE
FEATURE HAS IMPROVED OVER THE PAST 6 HOURS AND TO BE IN MORE
ALIGNMENT WITH A DT OF 5.0 FROM PTGW. UPPER LEVEL ANALYSIS INDICATES
A CONTINUED FAVORABLE ENVIRONMENT WITH MODERATE (15-20 KNOT)
NORTHERLY VWS WHICH IS OFFSET BY GOOD RADIAL OUTFLOW. THE CYCLONE IS
TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF AN EXTENSION OF THE STR
TO THE NORTH.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TY 09W IS FORECAST TO CONTINUE TRACKING NORTHWESTWARD UNDER
THE STEERING INFLUENCE OF THE STR THROUGH TAU 72. IT IS EXPECTED TO
INTENSIFY STEADILY PEAKING AT 115 KNOTS AT TAU 48 AS FAVORABLE
ENVIRONMENTAL CONDITIONS PERSIST. BY TAU 72, HOWEVER, TY 09 CHAN-HOM
WILL MAKE LAND FALL IN ZHEJIANG PROVINCE AND BEGIN DECAYING DUE TO
LAND INTERACTION. DYNAMIC GUIDANCE IS IN TIGHT AGREEMENT THROUGH
THIS PERIOD, LENDING HIGH CONFIDENCE TO THIS PORTION OF THE TRACK
FORECAST.
   C. IN THE EXTENDED FORECAST, TY 09W WILL TRACK TO THE NORTHEAST
AS THE STEERING STR EXTENSION BACKS TO THE EAST AND BREAKS DOWN DUE
TO AN APPROACHING MID-LATITUDE TROUGH. EXPECT FURTHER DECAY IN THE
SYSTEM DUE TO LAND INTERACTION IN THE EARLY PORTION OF THE EXTENDED
FORECAST AS WELL AS LIMITED OHC AND SOME INCREASE IN VWS.  NUMERICAL
MODEL GUIDANCE HAS COME INTO MUCH BETTER AGREEMENT OVER THE PAST SIX
HOURS WITH 11 OUT OF 12 MODELS DEPICTING A RECURVE SCENARIO BY 72
AND 8 OF THESE 11 TRACKING INTO THE YELLOW SEA BY TAU 120. HOWEVER,
DUE TO SOME UNCERTAINTY IN TIMING AND SPEED OF THE SYSTEM IN THE
EXTENDED FORECAST TRACK, THERE IS LOW CONFIDENCE IN THE JTWC
FORECAST TRACK.//
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