Advisories

WDPN31 PGTW 030300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 22W (KROVANH) WARNING NR 
008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 26.1N 130.2E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 131 NM EAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 14 KTS
   SIGNIFICANT WAVE HEIGHT: 21 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS AN EXPOSED
AND WELL-DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC) TRACKING
NORTHWESTWARD, WITH DEEP CONVECTION DISPLACED TO ITS SOUTH BY
MODERATE 15-20 KT NORTHERLY VERTICAL SHEAR. THE CONVECTION IS
WEAKER AND DISPLACED FARTHER FROM THE CENTER THAN SIX HOURS AGO.
UPPER-LEVEL OUTFLOW REMAINS WEAK EQUATORWARD AS THE STORM WRESTLES
WITH A WEAK UPPER-LEVEL TROUGH OVERHEAD. DEEP-LAYER DRY AIR IS
OBSERVED IN WATER VAPOR IMAGERY THROUGHOUT THE NORTHERN SEMICIRCLE.
A 020003Z ASCAT PASS REVEALED THE STRONGEST WINDS IN THE SOUTHEAST
AND NORTHEAST QUADRANTS, WITH THE LLCC SLIGHTLY ELONGATED TOWARDS
THE WEST, RESULTING IN SOME SHORT-TERM WOBBLES IN THE TRACK MOTION.
THE INITIAL INTENSITY IS SET AT 40 KT BASED ON THE ASCAT DATA AND
SURFACE OBSERVATIONS FROM KITA-DAITO, WHICH HAVE RANGED FROM 40 TO
45 KT AT AN ANEMOMETER HEIGHT OF 32 METERS ABOVE SEA LEVEL DURING THE 
PAST SEVERAL HOURS.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE SOUTHEAST OF JAPAN

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 41 KTS AT 022150Z
   CIMSS ADT: 35 KTS AT 022340Z
   CIMSS AIDT: 38 KTS AT 022340Z
   CIMSS D-MINT: 34 KTS AT 022150Z
   CIMSS D-PRINT: 36 KTS AT 022340Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK EQUATORWARD

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 22W (KROVANH) CONTINUES TO
TRACK NORTHWESTWARD TOWARD THE RYUKYU ISLANDS AND APPEARS TO HAVE
HELD A STEADY INTENSITY OVER THE PAST SIX HOURS. THE STORM HAS BEEN
WRESTLING WITH A WEAK UPPER-LEVEL TROUGH FOR SOME TIME, RESULTING
IN WEAK UPPER-LEVEL OUTFLOW AND INTRUSIONS OF DRY AIR THAT HAVE
THUS FAR LIMITED INTENSIFICATION. THE STORM'S CORE WIND FIELD HAS
BECOME BETTER DEFINED, AND ANY FURTHER BURSTS OF DEEP CONVECTION
NEAR THE LLCC COULD CAUSE SHORT-TERM FLUCTUATIONS IN INTENSITY
PRIOR TO 22W PASSING OVER THE RYUKYU ISLAND CHAIN. THE JTWC
FORECAST PROJECTS A NET-STEADY INTENSITY NEAR 40 KT THROUGH TAU 24.
THE STORM'S SHORT-TERM MOTION IS BEING GOVERNED BY A SUBTROPICAL 
RIDGE SOUTHEAST OF JAPAN, WHICH WILL DRIVE KROVANH NORTHWESTWARD FOR 
APPROXIMATELY THE NEXT 24 HOURS, PASSING BETWEEN OKINAWA AND AMAMI 
OSHIMA DURING WITHIN THE NEXT 12 HOURS. THEREAFTER, STEERING CURRENTS 
WILL BECOME WEAK AND COMPLEX AS AN UPPER-LEVEL TROUGH QUICKLY SCOOTS 
EASTWARD OVER THE KOREAN PENINSULA AND SEA OF JAPAN, USHERING IN A 
LOW- TO MID-LEVEL RIDGE IN ITS WAKE. THE RESULTING LOW-LEVEL 
NORTHEASTERLY COOL AND DRY FLOW IS EXPECTED TO HALT 22W'S NORTHWARD 
PROGRESS IN AROUND 24-36 HOURS, FORCING A STALL AND EVENTUALLY A 
NEAR-REVERSAL OF THE STORM'S MOTION IN A SOUTHWARD OR SOUTHEASTWARD 
DIRECTION, BACK INTO THE VICINITY OF OKINAWA IN AROUND 60 TO 72 
HOURS. DURING THE STALL, THE JUXTAPOSITION OF UPPER-LEVEL WESTERLIES 
ASSOCIATED WITH THE STJ OVERLAPPING THE SURFACE NORTHEASTERLIES WILL 
SUBSTANTIALLY INCREASE VERTICAL SHEAR AND DRY AIR ENTRAINMENT, LIKELY 
WEAKENING 22W SOMEWHAT, THOUGH SOME MODELS RETAIN GALES DURING THIS 
TIME, GRADUALLY EXPANDING FROM THE NORTHERN SEMICIRCLE INTO THE 
WESTERN SEMICIRCLE AS THE TRACK TURNS SOUTHWARD. AFTER 72 HOURS, 
THERE IS LESS CONFIDENCE IN THE TRACK FORECAST, AS THE STORM WILL BE
MAROONED IN WEAK STEERING CURRENTS BETWEEN A RIDGE OVER CHINA, A 
RIDGE EAST OF JAPAN, AND POTENTIALLY A NEW AREA OF LOW PRESSURE 
DEVELOPING WITHIN THE MONSOON TROUGH TO ITS SOUTHEAST. BOTH PHYSICS-
BASED AND AI-BASED MODELS GENERALLY AGREE ON KROVANH BEING POSITIONED
SOUTHEAST OF THE RYUKYU ISLANDS DURING THE 96 TO 120 HOUR PERIOD,
BUT MODEL SPREAD REMAINS RATHER LARGE. THE INTENSITY FORECAST
DURING THIS LONG-RANGE PERIOD IS ALSO LOWER CONFIDENCE, AS IT IS
SENSITIVE TO THE DEGREE TO WHICH THE STORM INGESTS MID-LATITUDE
AIR DURING ITS BRIEF VISIT TO THE EAST CHINA SEA. DYNAMICAL GLOBAL
MODELS FAVOR A BROADENING, HOLLOWED-OUT CIRCULATION THAT WEAKENS
THROUGH THE END OF THE FORECAST PERIOD, WHILE AI-BASED MODELS SHOW
THE POTENTIAL FOR REINTENSIFICATION AFTER THE STORM RETURNS EAST OF
THE RYUKYU ISLANDS. THE JTWC FORECAST IS A COMPROMISE OF THESE TWO
OUTCOMES, SHOWING A STEADY INTENSITY OF 35 KT NEAR THE END OF THE
FORECAST PERIOD.

MODEL DISCUSSION: THE JTWC TRACK FORECAST CLOSELY FOLLOWS A BLEND
OF THE PREVIOUS FORECAST AND THE MEAN OF THE PHYSICS-BASED
MULTI-MODEL CONSENSUS AND THE AI-BASED MULTI-MODEL CONSENSUS. THE
JTWC INTENSITY FORECAST IS SLIGHTLY ABOVE THE MULTI-MODEL CONSENSUS
THROUGH TAU 24 DUE TO SHORT-TERM TRENDS IN STORM STRUCTURE, THEN
NEAR THE CONSENSUS THEREAFTER. THE TRACK AND INTENSITY FORECASTS
HAVE MEDIUM (NEAR AVERAGE) CONFIDENCE THROUGH 72 HOURS, THEN LOWER
THAN AVERAGE CONFIDENCE THEREAFTER.

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