Tropical Storm CHAN-HOM Advisory Thu Jul 02

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 09W (CHAN-HOM) WARNING NR 09//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 09W (CHAN-HOM), LOCATED APPROXIMATELY 306 NM
SOUTHEAST OF ANDERSEN AFB, GUAM, HAS TRACKED WEST-SOUTHWESTWARD AT 20
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY SHOWS THE SYSTEM HAS MAINTAINED A CENTRAL DENSE OVERCAST
FEATURE THAT HAS DEEPENED AND EXPANDED BUT CONTINUES TO OBSCURE THE
LOW LEVEL CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS BASED ON
A LOW REFLECTIVITY LLCC FEATURE ON THE 020856Z F18 36GHZ MICROWAVE
IMAGE WITH HIGH CONFIDENCE. THE INITIAL INTENSITY OF 65 KNOTS IS
BASED ON THE DVORAK ESTIMATE OF T4.0 FROM PGTW AND REFLECTS THE
DEEPENED CONVECTION. UPPER LEVEL ANALYSIS INDICATES THAT THE SYSTEM
IS LOCATED IN A MARGINALLY FAVORABLE ENVIRONMENT WITH LOW TO MODERATE
(10 TO 20 KNOT) VERTICAL WIND SHEAR (VWS) AND EXCELLENT DIFFLUENT
OUTFLOW ALOFT. TY 09W IS CURRENTLY TRACKING ALONG THE SOUTHERN
PERIPHERY OF A SUB-TROPICAL RIDGE (STR) TO THE NORTH.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY 09W WILL MAINTAIN A GENERALLY WESTWARD TRAJECTORY THROUGH
TAU 24 UNDER THE INFLUENCE OF THE STEERING STR. AFTERWARDS, IT WILL
TURN TO THE NORTHWEST TOWARDS A BREAK IN THE STR. AS THE SYSTEM GAINS
LATITUDE, VWS WILL DECREASE AND OUTFLOW WILL IMPROVE. THIS WILL
PROMOTE STEADY INTENSIFICATION, REACHING 100 KNOTS BY TAU 72. MODEL
GUIDANCE SIGNIFICANTLY DIFFER IN LATERAL SPEED DURING THE FIRST 24-36
HOURS AS THE SYSTEM MAKES THE TURN, RENDERING THIS PORTION OF THE
FORECAST WITH LOW CONFIDENCE.
   C. TY CHAN-HOM WILL CONTINUE TO TRACK NORTHWESTWARD AND INTENSIFY
AS FAVORABLE ENVIRONMENTAL CONDITIONS PREVAIL REACHING SUPER TYPHOON
INTENSITY BY END OF FORECAST. MODEL GUIDANCE FOR THIS PORTION OF THE
FORECAST CONTINUES TO BE IN EXCELLENT AGREEMENT LENDING HIGH
CONFIDENCE TO THE EXTENDED PORTION OF THE JTWC TRACK FORECAST.//
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