WDPN31 PGTW 020900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 12W (KROSA) WARNING NR 
039//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 37.5N 144.0E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 218 NM SOUTHEAST OF MISAWA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 16 KTS
   SIGNIFICANT WAVE HEIGHT: 24 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A
WELL-ORGANIZED SYSTEM, WITH LOW-LEVEL BANDS WRAPPING INTO A DEFINED
CENTER. AT ANALYSIS TIME, THE VORTEX STRUCTURE WAS STILL
MISALIGNED, WITH CONVECTION CONFINED TO THE NORTHERN HEMISPHERE OF
THE LOW LEVEL CIRCULATION CENTER (LLCC) DUE TO A RECENT INFLUX OF
DRY AIR ALONG THE SOUTHERN HALF OF THE SYSTEM. IN THE SUBSEQUENT
PERIOD UP TO NOW, THE VORTEX HAS UNDERGONE A RAPID SYMMETRIZATION
AND CONVECTION IS REFORMING AROUND THE LLCC ONCE MORE. A 020619Z
SSMIS 91GHZ MICROWAVE IMAGE SUPPORTED THE MSI ANALYSIS, REVEALING
DRY AIR ACROSS MOST OF THE SOUTHERN SEGMENTS OF THE CIRCULATION,
AND CONVECTIVE BANDS LAID OUT TO THE NORTH OF THE CENTER.
UPPER-LEVEL ANALYSIS AND ANIMATED WATER VAPOR IMAGERY DEPICT STRONG
POLEWARD OUTFLOW INTO THE BASE OF A STRONG JET MAX FAR TO THE
NORTH. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED
ON THE MICROWAVE IMAGERY NOTED ABOVE. THE INITIAL INTENSITY IS
ASSESSED WITH MEDIUM CONFIDENCE, HEDGED HIGHER THAN THE BULK OF THE
SUBJECTIVE AND OBJECTIVE FIX ESTIMATES IN PERSISTENCE WITH EARLIER
SMAP DATA WHICH SHOWED WINDS ABOUT 5-10 KNOTS HIGHER THAN THE
ESTIMATES AT THAT TIME. ENVIRONMENTAL CONDITIONS ARE FAVORABLE,
WITH LOW TO MODERATE SHEAR (IN-PHASE WITH STORM MOTION), GOOD
OUTFLOW ALOFT AND WARM SSTS. IN FACT, THE SYSTEM IS MOVING ALONG A
TONGUE OF VERY WARM WATERS IN THE KUROSHIO CURRENT.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: NORTHWESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED TO THE EAST OF IWO TO. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T3.0 - 45 KTS
   CIMSS SATCON: 49 KTS AT 020250Z
   CIMSS ADT: 39 KTS AT 020540Z
   CIMSS AIDT: 47 KTS AT 020540Z
   CIMSS D-MINT: 50 KTS AT 020619Z
   CIMSS D-PRINT: 45 KTS AT 020700Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL STORM (TS) 12W IS FORECAST TO TRACK
EAST-NORTHEASTWARD THROUGH THE FORECAST PERIOD ALONG THE NORTHERN
SIDE OF A DEEP STR POSITIONED TO THE SOUTH. TRACK SPEEDS SLOW AT
THE END OF THE FORECAST AS THE SYSTEM MOVES INTO A SLIGHTLY WEAKER
STEERING PATTERN IS IT TRANSITIONS TO AN EXTRATROPICAL LOW. TS 12W
IS EXPECTED TO REMAIN OVER THE TONGUE OF THE KUROSHIO FOR THE NEXT
6 TO 12 HOURS, AND WILL AT MINIMUM MAINTAIN INTENSITY, AND MAY IN
FACT INTENSIFY BRIEFLY, AS OTHER ENVIRONMENTAL CONDITIONS ARE
SUPPORTIVE OF DEVELOPMENT. HOWEVER, AFTER TAU 12, THE SYSTEM BEGIN
TO ENCOUNTER INCREASING RELATIVELY SHEAR AS THE MOTION VECTOR AND
THE SHEAR VECTOR BEGIN TO DIVERGE. AT THE SAME TIME, DRY MID-LEVEL
WILL BEGIN TO INTRUDE INTO THE CORE OF THE SYSTEM, MARKING THE
ONSET OF A STEADY WEAKENING TREND OVER THE REMAINDER OF THE
FORECAST PERIOD. THE SYSTEM BEGINS EXTRATROPICAL TRANSITION (ETT)
AROUND TAU 48, WITH FULL ETT NO LATER THAN TAU 72 AS THE SYSTEM
BECOMES EMBEDDED IN THE MID-LATITUDE WESTERLIES AND DEVELOPS
FRONTAL CHARACTERISTICS. 

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN STRONG
AGREEMENT THROUGH THE FORECAST PERIOD, WITH ONLY MARGINAL SPREAD BY
TAU 72, LENDING HIGH CONFIDENCE TO THE JTWC FORECAST. INTENSITY
GUIDANCE IS IN AGREEMENT, BUT WEAKENS THE SYSTEM TOO QUICKLY, AND
THE JTWC FORECAST IS PLACED ABOUT 5 KNOTS HIGHER THAN THE TOP END
OF THE GUIDANCE PACKAGE WITH MEDIUM CONFIDENCE. 

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   INTENSITY 00-72 HR: MEDIUM//
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