Tropical Storm KROSA (12W)

WTPN31 PGTW 032100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL STORM 12W (KROSA) WARNING NR 045//
RMKS/
1. TROPICAL STORM 12W (KROSA) WARNING NR 045    
   02 ACTIVE TROPICAL CYCLONES IN NORTHWESTPAC
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
   WIND RADII VALID OVER OPEN WATER ONLY
    ---
   WARNING POSITION:
   031800Z --- NEAR 42.0N 160.3E
     MOVEMENT PAST SIX HOURS - 070 DEGREES AT 22 KTS
     POSITION ACCURATE TO WITHIN 060 NM
     POSITION BASED ON CENTER LOCATED BY SATELLITE
   PRESENT WIND DISTRIBUTION:
   MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   BECOMING EXTRATROPICAL
   RADIUS OF 034 KT WINDS - 000 NM NORTHEAST QUADRANT
                            120 NM SOUTHEAST QUADRANT
                            120 NM SOUTHWEST QUADRANT
                            045 NM NORTHWEST QUADRANT
   REPEAT POSIT: 42.0N 160.3E
    ---
   FORECASTS:
   12 HRS, VALID AT:
   040600Z --- 43.2N 166.0E
   MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   EXTRATROPICAL
   RADIUS OF 034 KT WINDS - 030 NM NORTHEAST QUADRANT
                            120 NM SOUTHEAST QUADRANT
                            120 NM SOUTHWEST QUADRANT
                            070 NM NORTHWEST QUADRANT
   VECTOR TO 24 HR POSIT: 080 DEG/ 23 KTS
    ---
   24 HRS, VALID AT:
   041800Z --- 43.8N 172.4E
   MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   EXTRATROPICAL
    ---
REMARKS:
032100Z POSITION NEAR 42.3N 161.7E.
03AUG25. TROPICAL STORM 12W (KROSA), LOCATED APPROXIMATELY 866 NM
EAST-NORTHEAST OF MISAWA, JAPAN, HAS TRACKED EAST-NORTHEASTWARD
AT 22 KTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR)
SATELLITE IMAGERY DEPICTS AN ELONGATED AND HEAVILY SHEARED SYSTEM,
WITH NEARLY FULLY EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) AND
REMAINING ASSOCIATED CONVECTION TO THE EAST. ADDITIONALLY, AN OLDER
021048Z METOP-B ASCAT IMAGE SHOWED HIGHLY ASYMMETRIC WIND FIELD,
WITH HIGHER INTENSITIES ALONG THE SOUTHERN PORTION OF THE
CIRCULATION. THE SYSTEM IS CURRENTLY BECOMING EXTRATROPICAL,
DUE TO CROSSING INTO THE BAROCLINIC ZONE TO THE NORTH. TS 12W IS
POSITIONED POLEWARD OF A WESTERN EXTENSION OF A SUBTROPICAL JET.
ASSESSMENT IS SUPPORTED BY GFS AND ECMWF PHASE CYCLONE DIAGRAMS.
ADDITIONALLY, VERY COLD (17-18 C) SEA SURFACE TEMPERATURES AND
INCREASING VERTICAL WIND SHEAR ARE CREATING AN INCREASINGLY HOSTILE
ENVIRONMENT FOR TROPICAL DEVELOPMENT. NUMERICAL MODEL GUIDANCE IS
IN STRONG AGREEMENT IN REGARD TO THE TRACK AND INTENSITY, RESULTING
IN HIGH CONFIDENCE OF THE OFFICIAL JTWC FORECAST. THIS IS THE FINAL
WARNING ON THIS SYSTEM BY THE JOINT TYPHOON WRNCEN PEARL HARBOR HI.
THE SYSTEM WILL BE CLOSELY MONITORED FOR SIGNS OF REGENERATION.
MINIMUM CENTRAL PRESSURE AT 031800Z IS 983 MB. MAXIMUM SIGNIFICANT
WAVE HEIGHT AT 031800Z IS 22 FEET. REFER TO TROPICAL STORM 13W (BAILU) 
WARNINGS (WTPN32 PGTW) FOR SIX-HOURLY UPDATES.
//
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WDPN31 PGTW 031500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 12W (KROSA) WARNING NR 
044//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 41.2N 157.5E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 741 NM EAST OF MISAWA, JAPAN
   MOVEMENT PAST 6 HOURS: EAST-NORTHEASTWARD AT 24 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A SYSTEM
IN THE THROES OF RAPID VORTEX DECOUPLING, WITH A PARTIALLY EXPOSED
LOW LEVEL CIRCULATION CENTER (LLCC) SOUTHWEST OF THE MID-LEVEL
ROTATION WITH REMNANT CONVECTION. A 031049Z ASCAT-B AND A 030952Z
ASCAT-C PASS REVEALED A SMALL LLCC WITH A BROAD SWATH OF GALE-FORCE
WINDS ACROSS THE SOUTHERN HEMISPHERE OF THE CIRCULATION AND AN
EMBEDDED REGION OF 45-50 KNOT WINDS TO THE SOUTH. THE SERIES OF
ASCAT PASSES LENT HIGH CONFIDENCE TO THE INITIAL POSITION. THE
SCATTEROMETER DATA ALSO PROVIDED HIGH CONFIDENCE TO THE INITIAL
INTENSITY, WHICH WAS HELD HIGHER THAN THE SUBJECTIVE AND OBJECTIVE
ESTIMATES NOTED BELOW DUE TO THE SCATTEROMETER DATA. ENVIRONMENTAL
CONDITIONS ARE RAPIDLY BECOMING UNFAVORABLE, WITH STRONG WESTERLY
SHEAR, VERY COOL SSTS, AND SIGNIFICANT DRY AIR, PARTICULARLY ALONG
THE WESTERN FLANK, OFFSET BY ROBUST POLEWARD OUTFLOW.

INITIAL WIND RADII BASIS: VORTEX DECOUPLING.

CURRENT STEERING MECHANISM: NORTHERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) POSITIONED TO THE SOUTH. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T2.0 - 30 KTS
   KNES: T2.5 - 35 KTS
   CIMSS ADT: 41 KTS AT 031140Z
   CIMSS AIDT: 45 KTS AT 031140Z
   CIMSS D-MINT: 38 KTS AT 030752Z
   CIMSS D-PRINT: 40 KTS AT 031230Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 25-30 KTS
   SST: 20-22 CELSIUS
   OUTFLOW: STRONG POLEWARD

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: TROPICAL STORM (TS) 12W IS MOVING QUICKLY NOW,
ALONG THE NORTHERN SIDE OF THE STRONG RIDGE TO THE SOUTH. WHILE
THIS RIDGE WILL QUICKLY MOVE SOUTHWEST OVER THE NEXT 12 TO 24
HOURS, THERE WILL BE LITTLE IMPACT ON EITHER THE TRACK SPEED OR
DIRECTION DUE TO THE FACT THAT ANOTHER RIDGE QUICKLY MOVES IN FROM
THE EAST AND THE STEERING HANDOFF WILL BE QUITE RAPID. TS 12W IS
THUS EXPECTED TO CONTINUE TRACKING EAST-NORTHEASTWARD AT ABOUT
22-24 KNOTS THROUGH THE ENTIRE FORECAST PERIOD. AS TS 12W BECOMES
FULLY DECOUPLED, MOVES OVER EVEN COLDER WATERS AND DRY AIR RUSHES
TO ENGULF THE REMNANT VORTEX, IT WILL STEADILY WEAKEN WHILE
SIMULTANEOUSLY UNDERGOING EXTRATROPICAL TRANSITION (ETT).
COMPLETION OF ETT IS ANTICIPATED BY TAU 36. 

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE DISPLAYS LITTLE IN
THE WAY OF EITHER CROSS- OR ALONG-TRACK SPREAD THROUGH THE FORECAST
PERIOD, LENDING HIGH CONFIDENCE TO THE JTWC FORECAST. INTENSITY
GUIDANCE IS ALSO IN GOOD AGREEMENT ON A STEADY WEAKENING THROUGH
ETT, THOUGH THE MAJORITY OF THE GUIDANCE IS A BIT TOO QUICK TO
DISSIPATE THE SOON TO BE EXTRATROPICAL LOW AND THE JTWC FORECAST IS
HEDGED SLIGHTLY HIGHER TO REFLECT THAT. 

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