WDPN32 PGTW 120900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 07W (SON-TINH) WARNING NR 
001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 32.4N 151.5E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 613 NM EAST-SOUTHEAST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 18 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL STORM (TS) 07W (SON-TINH), WAS PREVIOUSLY ASSESSED AS A
SUBTROPICAL STORM (SS) LABELED AS 95W. A MANUAL PHASE
CLASSIFICATION ANALYSIS CONDUCTED AT 120000Z DETERMINED THAT THE
SYSTEM IS TROPICAL IN NATURE AND THUS HAS BEEN REASSESSED AS A
TROPICAL STORM. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI)
DEPICTS A FULLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC), WITH
PERSISTENT DEEP CONVECTION DISPLACED INTO THE SOUTHWESTERN
QUADRANT. A 120536Z SSMIS 91GHZ IMAGE CONFIRMED THE WELL-ORGANIZED
SPIRAL BANDING IS CONFINED TO THE LOWER-LEVELS, SIGNIFICANT DRY AIR
FIRMLY ENTRENCHED OVER THE SYSTEM IN THE MID-LEVELS. THE INITIAL
POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE EXPOSED LLCC
IN THE MSI. THE INITIAL INTENSITY OF 40 KNOTS IS ASSESSED WITH HIGH
CONFIDENCE BASED ON A PARTIAL 112251Z ASCAT-B PASS THAT REVEALED
AN AREA OF 35-40 KNOT WINDS IN THE NORTHEAST QUADRANT, AND EARLIER
SMAP AND SMOS PASSES WHICH SHOWED A SIMILAR PATTERN. THE WIND FIELD
REMAINS HIGHLY ASYMMETRIC, WITH ELEVATED WINDS EXTENDING FAR TO THE
SOUTHEAST, BUT THE INNER CORE OF GALE-FORCE WINDS IS SEPARATED FROM
THIS BAND. ENVIRONMENTAL ANALYSIS REVEALS A MARGINALLY UNFAVORABLE
ENVIRONMENT. WHILE SHEAR IS LOW AND SSTS ARE MODESTLY WARM
(26-27C), THE PRESENCE OF AN UPPER-LEVEL LOW A COUPLE HUNDRED MILES
TO THE SOUTH IS IMPARTING EASTERLY CONVERGENCE FLOW ALOFT. THE
SIGNIFICANT DRY AIR IN THE MID-LEVELS IS INHIBITING CONVECTIVE
DEVELOPMENT OVER THE CENTER AS WELL, HELPING TO KEEP THE VORTEX
CONFINED TO THE LOW-LEVELS.

INITIAL WIND RADII BASIS: PARTIAL SCATTEROMETER DATA, SMAP AND SMOS
DATA. 

CURRENT STEERING MECHANISM: SOUTHWESTERN SIDE OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) TO THE NORTHEAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.0 - 30 KTS
   KNES: T2.0 - 30 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 5-10 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: WEAK EQUATORWARD
   OTHER FACTORS: SIGNIFICANT MID-LEVEL DRY AIR. 

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: HIGH

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION: TROPICAL STORM 07W IS FORECAST TO CONTINUE
TRACKING NORTHWEST ALONG THE SOUTHWESTERN PERIPHERY OF THE DEEP STR
THROUGH THE DURATION OF THE FORECAST PERIOD. A SLIGHT TURN
NORTHWARD IS EXPECTED AT BY THE VERY END OF THE FORECAST AS THE
SYSTEM COMES UNDER THE STEERING INFLUENCE OF THE LOW-LEVEL WIND
PATTERN WHICH IS ORIENTED MORE NORTH-SOUTH THAN THE DEEP-LAYER
WINDS. HAVING ALREADY PEAKED IN INTENSITY WITHIN THE LAST 24 HOURS,
TS 07W IS FORECAST TO STEADILY WEAKEN AS IT TRACKS NORTHWESTWARD
DUE TO COOLING SSTS, PERSISTENT DRY AIR IN THE MID-LEVELS, AND
INCREASING NORTHEASTERLY SHEAR. FULL DISSIPATION IS EXPECTED NO
LATER THAN TAU 48 AND POTENTIALLY AS EARLY AS TAU 36, TO THE EAST
OF NORTHERN HONSHU. 

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN GOOD
AGREEMENT, DEPICTING MINIMAL CROSS OR ALONG-TRACK SPREAD THROUGH
THE END OF THE FORECAST PERIOD. THE JTWC FORECAST IS PLACED ON THE
SOUTHERN SIDE OF THE GUIDANCE ENVELOPE WITH HIGH CONFIDENCE.
INTENSITY GUIDANCE IS ALSO IN GOOD AGREEMENT, WITH ALL CONSENSUS
MEMBERS IN AGREEMENT THAT TS 07W WILL QUICKLY WEAKEN AND ULTIMATELY
DISSIPATE BY TAU 48, LENDING HIGH CONFIDENCE TO THE JTWC FORECAST. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   INTENSITY 0 - 72 HR: HIGH//
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