WDPN32 PGTW 130900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUBTROPICAL DEPRESSION 07W (SEVEN)   
WARNING NR 003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 30.7N 126.1E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 233 NM SOUTHWEST OF SASEBO, JAPAN
   MOVEMENT PAST 6 HOURS: EASTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 13 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
THIS SYSTEM IS CLASSIFIED AS A SUBTROPICAL CYCLONE, WITH STRUCTURAL
FEATURES CHARACTERISTIC OF BOTH TROPICAL AND MID-LATITUDE CYCLONES.
THIS WARNING IS PROVIDED AS A SPECIAL ISSUANCE TO FACILITATE
RESOURCE PROTECTION. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI)
DEPICTS A BROAD, EXPOSED LOW-LEVEL CIRCULATION, WITH FLARING DEEP
CONVECTION TO THE NORTHEAST. THE INITIAL POSITION IS PLACED WITH
MEDIUM CONFIDENCE BASED ON THE MSI. A 130734Z SSMIS 91GHZ COLOR
COMPOSITE MICROWAVE IMAGE DEPICTS WEAK BANDING WRAPPING INTO A
BROAD LOW-LEVEL CIRCULATION CENTER. THE INITIAL INTENSITY OF 30 KTS
IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE PGTW ST1.5 ESTIMATE
(25-30 KNOTS).

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: SYSTEM IS EMBEDDED WITHIN THE BASE OF A
DEEP UPPER-LEVEL TROUGH, WITH A STEERING RIDGE POSITIONED TO THE
SOUTH AND ANOTHER BROAD SUBTROPICAL RIDGE POSITIONED TO THE EAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   CIMSS ADT: 29 KTS AT 130520Z
   CIMSS AIDT: 35 KTS AT 130730Z
   CIMSS D-MINT: 23 KTS AT 130502Z
   CIMSS D-PRINT: 25 KTS AT 130730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 15-20 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: MODERATE POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

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

FORECAST DISCUSSION: SUBTROPICAL DEPRESSION (SD) 07W IS EMBEDDED
WITHIN A DEEP UPPER-LEVEL MAJOR SHORTWAVE TROUGH POSITIONED OVER
THE KOREAN PENINSULA AND EAST CHINA SEA. THIS IS FORECAST TO DRIVE
THE SYSTEM EASTWARD TO EAST-NORTHEASTWARD THROUGH TAU 12. AFTER TAU
12, THE SYSTEM IS EXPECTED TO TURN POLEWARD AND TRACK ALONG THE
EASTERN COAST OF THE KOREAN PENINSULA AS IT TRANSITIONS TO THE STR
POSITIONED TO THE EAST. SLIGHT INTENSIFICATION TO SUBTROPICAL STORM
STRENGTH IS EXPECTED BY TAU 24 DRIVEN BY THE UPPER-LEVEL DYNAMICAL
SUPPORT OF THE MAJOR SHORT-WAVE TROUGH.     

MODEL DISCUSSION: ANALYSIS OF BOTH DETERMINISTIC AND ENSEMBLE MODEL
DATA INDICATE HIGH UNCERTAINTY IN THE JTWC TRACK AND INTENSITY
FORECAST. THERE IS A VERY LARGE SPREAD IN DETERMINISTIC SOLUTIONS,
WITH NAVGEM AND EEMI SHOWING A MORE EAST-NORTHEASTWARD TRACK INTO
SOUTHERN KYUSHU AT 30-35 KNOT INTENSITY. THE REMAINDER OF THE
GUIDANCE RECURVES THE SYSTEM SHARPLY POLEWARD OVER NORTHERN KYUSHU
TO SOUTHEASTERN KOREA, WITH SLIGHTLY HIGHER PEAK INTENSITY VALUES
OF 35-40 KNOTS. THE 130000Z ECENS SHOWS A LIMITED NUMBER OF
SOLUTIONS TRACKING THE SYSTEM INTO KYUSHU. THE 130000Z GEFS DEPICTS
A BIFURCATION IN GUIDANCE WITH THE LARGE MAJORITY OF SOLUTIONS
INDICATING A MORE EASTWARD TRACK INTO THE KYUSHU AND WESTERN JAPAN
REGION. THE OTHER CLUSTER OF SOLUTIONS TRACKS THE SYSTEM POLEWARD
THROUGH THE TSUSHIMA STRAIT THEN POLEWARD INTO THE WESTERN SEA OF
JAPAN. AN ADDITIONAL FACTOR IS THE FORMATION OF A STRONG UPPER-LEVEL 
LOW OVER THE KOREAN PENINSULA WITHIN THE NEXT 24 HOURS, WITH MULTIPLE 
VORTICITY MAXIMUMS MERGING INTO ONE LARGE, DYNAMIC, COMPLEX UPPER-
LEVEL LOW. THEREFORE, THERE IS POTENTIAL AND UPPER-LEVEL SUPPORT FOR 
THE FORMATION OF MULTIPLE SURFACE LOWS. THIS SYNOPTIC SITUATION MAKES 
IT VERY DIFFICULT TO TRACK OUR SYSTEM WITH ANY CONFIDENCE. THE 130000Z 
HAFS-A RUN SHOWS SD 07W APPROACHING WESTERN KYUSHU AND DISSIPATING, 
WITH ANOTHER SUBTROPICAL LOW FORMING NEAR 36N 130E THEN TRACKING OVER 
THE KOREAN PENINSULA.            

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