Tropical Storm RAMMASUN Advisory Cts, 12.07.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 09W (NINE) WARNING
NR 06//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 09W (NINE), LOCATED APPROXIMATELY 63 NM
EAST-SOUTHEAST OF ANDERSEN AFB, GUAM HAS TRACKED WEST-NORTHWESTWARD
AT 08 KNOTS OVER THE PAST SIX HOURS. TD 09W HAS BEEN DOWNGRADED FROM
TROPICAL STORM STATUS DUE TO RECENT OBSERVATIONS AND THE LACK OF
SUPPORTING DVORAK ESTIMATES FROM PGTW, KNES, AND RJTD. THE
OBSERVATIONS AT GUAM INDICATE THE SYSTEM REMAINS A WEAKLY DEFINED
LOW LEVEL CIRCULATION CENTER (LLCC) TO THE EAST OF GUAM. ANIMATED
ENHANCED INFRARED SATELLITE IMAGERY DEPICTS DEEP CONVECTION
ASSOCIATED WITH THE SYSTEM HAS BEEN SHEARED TO THE NORTHWEST UNDER
A MARGINAL UPPER LEVEL ENVIRONMENT. RECENT FRESH CONVECTION HAS
STARTED TO BUILD OVER THE LOOSELY ORGANIZED LLCC. A SERIES OF
SPURIOUS SMALLER CIRCULATIONS TO THE SOUTH OF GUAM HAVE BEEN OBSERVED
IN THE GUAM RADAR IMAGERY. ATMOSPHERIC SOUNDINGS FROM GUAM AT 1200Z
INDICATED STRONGER 25 TO 30 KNOTS OF EASTERLY FLOW IN THE MID TO
UPPER LEVELS, CREATING MODERATE LEVELS OF VERTICAL WIND SHEAR (VWS)
OVER THE LLCC. TD 09W CONTINUES TO TRACK ALONG THE SOUTHERN PERIPHERY
OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR), ANCHORED BETWEEN IWO TO
AND GUAM.
3. FORECAST REASONING.
   A. THE CURRENT FORECAST SHIFTS THE INTENSITY FORECAST REASONING,
DECREASING THE INITIAL INTENSITY TO 30 KNOTS, BASED ON THE AVAILABLE
ENVIRONMENTAL OBSERVATIONS. THE FORECASTED INTENSITY HAS BEEN
DECREASED AT ALL TAUS IN RESPONSE TO THE RE-EVALUATION OF THE UPPER
LEVEL ENVIRONMENT.
   B. TD 09W IS FORECAST TO TRACK WESTWARD FOR THE NEXT 72 HOURS
ALONG THE SOUTHERN PERIPHERY OF THE STR. BASED ON THE SHIFT IN UPPER
LEVEL SUPPORT, INCREASED VWS THAN PREVIOUSLY FORECASTED, THE OVERALL
ENVIRONMENT WILL STRUGGLE TO ALIGN FOR THE NEXT 36 TO 48 HOURS,
LEADING TO A SLOW DEVELOPMENT POTENTIAL THROUGH TAU 48. SEA SURFACE
TEMPERATURES (SST) REMAIN FAVORABLE ALONG THE FORECASTED TRACK, BUT
THE OUTFLOW WILL REMAIN THE LIMITING FACTOR IN THE NEAR TERM. BY TAU
72, VWS IS EXPECTED TO DECREASE ALLOWING FOR INCREASED INTENSIFI-
CATION.
   C. AFTER TAU 72, A MID-LATITUDE TROUGH IS FORECAST TO DIG OVER
EASTERN CHINA, CAUSING A SHIFT IN THE STR, LEADING TO A MORE WEST-
NORTHWEST TRACK TOWARDS THE NORTHERN PART OF LUZON. ADDITIONALLY,
THE VERY FAVORABLE SST VALUES PRIOR TO THE APPROACH WILL LEAD TO
A MAXIMUM INTENSITY AROUND TAU 84, POSSIBLY NEAR 100 KNOTS BUT IS
NOT REFLECTED IN THE FORECAST AS THE TAU 120 INTENSITY OF 95 KNOTS
ENCOMPASSES A SLIGHT IMPACT TO THE LOW LEVEL STRUCTURE AS THE INFLOW
WITHIN THE NORTHWEST QUADRANT IS IMPACTED BY CROSSING OVER LUZON.
THE AVAILABLE MODEL GUIDANCE IS IN GOOD AGREEMENT; HOWEVER, DUE TO
THE INITIAL POSITIONING AND TRACK SPEED UNCERTAINTY, THE OVERALL
CONFIDENCE IN THE FORECAST REMAINS LOW.//
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