Advisories

WDPN31 PGTW 022100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 22W (KROVANH) WARNING NR 
007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 24.8N 130.9E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 196 NM EAST-SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 21 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
WELL-DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC) THAT MAY BE
DEVELOPING A MORE WELL-DEFINED CORE WIND FIELD THAN IT PREVIOUSLY
POSSESSED, WITH COMPACT ROTATION EVIDENT. THE LLCC IS PARTIALLY
EXPOSED DUE TO LIGHT NORTHERLY SHEAR PUSHING DEEP CONVECTION INTO
THE SOUTHERN SEMICIRCLE, WITH WEAK UPPER-LEVEL OUTFLOW CONFINED
SOUTHWARD. THE CONVECTION ITSELF HAS PULSED IN RECENT HOURS, WITH A
STRONGER AND MORE CIRCULAR CONVECTIVE BURST COVERING THE SOUTHERN
SIDE OF THE LLCC, LIKELY CONTRIBUTING TO THE MORE COMPACT-LOOKING
CIRCULATION. THE STRONGEST WINDS REMAIN TO THE NORTHEAST OF THE
CENTER, WHERE GALES HAVE BEEN OBSERVED BY GROUND STATIONS IN THE
DAITO ISLANDS ABOUT 45 NM FROM THE CENTER. BASED ON THESE
OBSERVATIONS AND OBJECTIVE SATELLITE-BASED INTENSITY ESTIMATES, THE
CURRENT INTENSITY IS SET AT 40 KT.

INITIAL WIND RADII BASIS: PERSISTENCE AND SURFACE OBSERVATIONS

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE EAST OF JAPAN

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 44 KTS AT 021658Z
   CIMSS ADT: 34 KTS AT 021740Z
   CIMSS AIDT: 36 KTS AT 021740Z
   CIMSS D-MINT: 34 KTS AT 021743Z
   CIMSS D-PRINT: 33 KTS AT 021820Z

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

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 TOWARD THE RYUKYU ISLANDS AND HAS BECOME A
LITTLE BETTER ORGANIZED OVER THE PAST SIX HOURS. THE STORM HAS BEEN
WRESTLING WITH A WEAK UPPER-LEVEL LOW FOR SOME TIME, RESULTING IN
WEAK UPPER-LEVEL OUTFLOW AND INTRUSIONS OF DRY AIR THAT HAVE THUS
FAR LIMITED INTENSIFICATION. RECENT SIGNS OF THE CORE WIND FIELD
BECOMING BETTER DEFINED AND MORE PERSISTENT CENTRAL CONVECTIVE
ACTIVITY SUGGEST THAT SOME FURTHER INTENSIFICATION MAY OCCUR IN THE
IMMEDIATE FUTURE BEFORE KROVANH PASSES OVER THE RYUKYU ISLAND
CHAIN. THE JTWC FORECAST PROJECTS A SHORT-TERM PEAK INTENSITY OF 45
KT AT TAU 12. 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 24-36 HOURS, PASSING
BETWEEN OKINAWA AND AMAMI OSHIMA BETWEEN TAU 12 AND TAU 24.
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 36
HOURS, FORCING A STALL AND EVENTUALLY A NEAR-REVERSAL OF THE
STORM'S MOTION IN A SOUTHWARD OR SOUTHEASTERLY 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 MOST 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
LOW 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 LOW 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 AND
HAFS-A SHOW THE POTENTIAL FOR RE-INTENSIFICATION 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
MAJORITY OF THE GUIDANCE PACKAGE NOW FAVORS A COUNTERCLOCKWISE
LOOP-SHAPED TRACK RATHER THAN A CLOCKWISE LOOP-SHAPED TRACK. 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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