Advisories

WDPN31 PGTW 032100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 22W (KROVANH) WARNING NR 
011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 29.0N 128.2E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 151 NM NORTH OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A STILL
EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) MOVING NORTHWESTWARD
INTO THE EAST CHINA SEA. DEEP CONVECTION HAS PERSISTED EAST OF THE
LLCC, SIGNIFICANTLY DISPLACED DUE TO INCREASING WESTERLY VERTICAL
SHEAR OF 25-30 KT. MODERATE UPPER-LEVEL OUTFLOW EASTWARD AND
TURNING EQUATORWARD IS OBSERVED. A DEEP-LAYER DRY AIRMASS CONTINUES
TO ENVELOPE THE WESTERN SEMICIRCLE. SURFACE SUSTAINED WIND
OBSERVATIONS FROM THE RYUKYU ISLANDS HAVE OCCASIONALLY SPIKED INTO
THE 30-35 KT RANGE IN RECENT HOURS. THE INITIAL INTENSITY OF 22W IS
HELD AT 40 KT BASED ON A BLEND OF SURFACE OBSERVATIONS, OBJECTIVE
SATELLITE INTENSITY ESTIMATES, AND PERSISTENCE OF THE SATELLITE
PRESENTATION RELATIVE TO THE PAST 12 HOURS.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T2.0 - 30 KTS
   CIMSS SATCON: 36 KTS AT 031638Z
   CIMSS ADT: 41 KTS AT 031740Z
   CIMSS AIDT: 37 KTS AT 031740Z
   CIMSS D-MINT: 34 KTS AT 031724Z
   CIMSS D-PRINT: 38 KTS AT 031740Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 25-30 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE EASTWARD
   OTHER FACTORS: DEEP-LAYER DRY AIR MASS IN THE WESTERN SEMICIRCLE

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL STORM 22W (KROVANH) CONTINUES TO
TRACK NORTHWESTWARD INTO THE EAST CHINA SEA. THE MOST RECENT FEW
HOURS OF MOTION SUGGEST THAT THE ANTICIPATED SLOWING PHASE HAS
BEGUN, WHICH WILL CULMINATE IN A NEAR-STALL AND REVERSAL OF THE
TRACK MOTION OVER THE NEXT 24 TO 36 HOURS. LOW- TO MID-LEVEL
RIDGING BUILDING INTO THE YELLOW SEA IS FORECAST TO TURN KROVANH
SOUTHWARD AND THEN SOUTHEASTWARD TOWARD OKINAWA, PASSING BY THE
ISLAND IN AROUND 48 HOURS. THE SLOW COUNTERCLOCKWISE LOOP IS THEN
EXPECTED TO CONTINUE AS THE MONSOON TROUGH LIFTS NORTHWARD AND
CREATES A LARGE-SCALE CYCLONIC CAULDRON SOUTH OF JAPAN. BEYOND 48
HOURS, DYNAMIC MODEL GUIDANCE GENERALLY AGREES THAT 22W WILL
GRADUALLY CURVE EASTWARD AND THEN NORTHEASTWARD IN RESPONSE TO AN
UPPER-LEVEL TROUGH TO THE NORTH OVER THE KOREAN PENINSULA IN 72
HOURS, ULTIMATELY APPROACHING MAINLAND JAPAN AT TAU 120. REGARDING
THE INTENSITY FORECAST, ENVIRONMENTAL CONDITIONS ARE CURRENTLY
BECOMING MORE HOSTILE AS 22W ENCOUNTERS STRONGER WESTERLY SHEAR IN
THE EAST CHINA SEA, WHICH IS EXPECTED TO DEGRADE THE STORM'S
STRUCTURE IN THE NEAR-TERM. A BELT OF COLD ADVECTION SETTING UP
BETWEEN KOREA AND JAPAN IS FORECAST TO SUSTAIN GALES ON THE
NORTHERN SIDE OF THE CIRCULATION, EVENTUALLY WRAPPING INTO THE
WESTERN SEMICIRCLE AS THE STORM TURNS SOUTHWARD. AS 22W PASSES
OKINAWA IN ABOUT 48 HOURS, THE JTWC FORECAST NOW DIPS BELOW
TROPICAL STORM FORCE, AS SIGNIFICANT STIRRING OF THE MID-LATITUDE
AIR MASS INTO THE STORM ENVIRONMENT APPEARS LIKELY TO MUTE
CONVECTIVE ACTIVITY FOR A PERIOD OF TIME, AND DYNAMICAL MODELS
AGREE ON BROADENING AND WEAKENING OF THE CIRCULATION. DURING
KROVANH'S REACCELERATION NORTHEASTWARD AT THE END OF THE FORECAST,
SOME REINTENSIFICATION IS POSSIBLE SHOULD A WELL-DEFINED
CIRCULATION PERSIST AND REACQUIRE DEEP CONVECTION. WHILE SOME
MODELS LIKE HAFS-A DEPICT THIS SCENARIO, OTHERS DEPICT THE
POSSIBILITY THAT 22W WASHES OUT INTO A BROADER MONSOON DEPRESSION
AND FAILS TO REINTENSIFY. THE JTWC FORECAST CURRENTLY REPRESENTS A
COMPROMISE BETWEEN THESE TWO SCENARIOS.

MODEL DISCUSSION: THE JTWC TRACK FORECAST FOLLOWS A BLEND OF
PHYSICS-BASED AND AI-BASED MODEL AIDS, WITH SPREAD NOTICEABLY
SMALLER THAN YESTERDAY, LENDING MEDIUM CONFIDENCE TO THE TRACK
FORECAST. THE JTWC INTENSITY FORECAST IS CLOSE TO THE MULTI-MODEL
CONSENSUS, PLACED WITH MEDIUM CONFIDENCE.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: MEDIUM
   TRACK 72-120 HR: MEDIUM
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
NNNN