WDPN32 PGTW 121500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 07W (SON-TINH) WARNING NR 
002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 33.0N 150.4E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 549 NM EAST-SOUTHEAST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A FULLY
EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC), WITH CONVECTIVE DEBRIS
AND A FEW ISOLATED CONVECTIVE TOWERS ISOLATED TO THE SOUTHERN
PERIPHERY. UPPER-LEVEL CIRRUS STREAKS CAN BE SEEN MOVING RAPIDLY
ACROSS THE CENTER OF THE LLCC, INDICATIVE OF THE STRONG UPPER-LEVEL
EASTERLY FLOW ASSOCIATED WITH AN UPPER-LEVEL LOW POSITIONED TO THE
SOUTHEAST OF THE SYSTEM. A 120755Z RCM-1 SAR PASS REVEALED A
SYMMETRIC WIND FIELD, WITH WINDS UP TO 30 KNOTS CLOSING OFF THE
CORE OF THE SYSTEM TO THE SOUTHWEST, WHILE WINDS UP TO 42 KNOTS
WERE EVIDENT IN THE NORTHEASTERN HALF OF THE CIRCULATION. THE
INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE
EXPOSED LLCC IN THE EIR. THE INITIAL INTENSITY IS ASSESSED WITH
HIGH CONFIDENCE BASED ON THE EARLIER SAR PASS AND IS CONSISTENT
WITH CIMSS DPRINT AND HEDGED SLIGHTLY HIGHER THAN THE AGENCY DVORAK
ESTIMATES. ANALYSIS REVEALS A MARGINALLY UNFAVORABLE ENVIRONMENT,
WITH WARM SSTS AND MODERATE OUTFLOW BEING OFFSET BY STRONG EASTERLY
WIND SHEAR AND EXTREMELY DRY AIR EXTENDING FROM ABOUT 700MB
UPWARDS.

INITIAL WIND RADII BASIS: SAR DATA 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T1.5 - 25 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 40 KTS AT 121200Z
   CIMSS DPRINT: 38 KTS AT 121230Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 20-25 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD
   OTHER FACTORS: VERY DRY AIR ALOFT OVER TOP OF THE SYSTEM. 

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: BASED ON THE SAR DATA MENTIONED ABOVE, TS 07W
HAS MANAGED TO MAINTAIN 40 KNOT INTENSITY, EVEN IN THE FACE OF AN
OTHERWISE UNFAVORABLE ENVIRONMENT. LIKELY THIS WONT LAST MUCH
LONGER AS THE SYSTEM WILL START TO SPIN DOWN IMMINENTLY. TS 07W IS
FORECAST TO TRACK NORTHWESTWARD THROUGH TAU 36 ALONG THE
SOUTHWESTERN SIDE OF THE STR TO THE NORTHEAST. BY THE END OF THE
FORECAST, THE STEERING RIDGE QUICKLY SHIFTS SOUTHWARD, ALLOWING TS
07W TO ROUND THE RIDGE AXIS AND TURN NORTHEASTWARD AS IT
DISSIPATES. THE COMBINATION OF INCREASED SHEAR, DECREASING SSTS AND
PERSISTENT DRY AIR ALOFT, WILL LEAD TO FULL DISSIPATION BETWEEN TAU
36 AND 48 TO THE EAST OF HOKKAIDO. 

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN STRONG
AGREEMENT, WITH MINIMAL CROSS- OR ALONG-TRACK SPREAD, LENDING HIGH
CONFIDENCE TO THE JTWC TRACK FORECAST. INTENSITY GUIDANCE IS A BIT
MORE MIXED, WITH THE GUIDANCE SPREAD BETWEEN DISSIPATION AT TAU 36
AND 48, REFLECTING THE DIFFERENCES IN THE AMOUNT OF TIME NEEDED FOR
THE SYSTEM TO SPIN DOWN.  

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