Advisories

WDPN31 PGTW 040300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 22W (KROVANH) WARNING NR 
012//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 29.5N 128.0E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 180 NM NORTH OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A STILL
EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) WITH DEEP CONVECTION
DISPLACED TO THE EAST BY STRONG WESTERLY VERTICAL SHEAR. THE ENTIRE
WESTERN SEMICIRCLE AND MOST OF THE SOUTHERN SEMICIRCLE ARE DEVOID
OF DEEP CONVECTION. MODERATE UPPER-LEVEL OUTFLOW IS OBSERVED
TOWARDS THE EAST, BEGINNING TO TAP INTO THE SUBTROPICAL JET OVER
JAPAN AS AN UPPER-LEVEL TROUGH CROSSES THE KOREAN PENINSULA. THE
INITIAL INTENSITY IS HELD AT 40 KT, A LITTLE ABOVE AGENCY DVORAK
AND OBJECTIVE SATELLITE-BASED INTENSITY ESTIMATES DUE TO
GRADIENT-ENHANCED FLOW ON THE NORTH SIDE OF THE LLCC AND ELEVATED
WIND OBSERVATIONS AS HIGH AS 46 KT FROM SHIPS IN THE VICINITY OF
THE RYUKYU ISLANDS.

INITIAL WIND RADII BASIS: PERSISTENCE 

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: T2.0 - 30 KTS
   CIMSS SATCON: 40 KTS AT 032135Z
   CIMSS ADT: 41 KTS AT 032340Z
   CIMSS AIDT: 37 KTS AT 032340Z
   CIMSS D-MINT: 34 KTS AT 032134Z
   CIMSS D-PRINT: 35 KTS AT 032340Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 25-30 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE EASTWARD

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 SLOW
ITS SPEED OF ADVANCE TOWARD THE NORTHWEST AND IS NEARING ITS
ANTICIPATED PIVOT BACK SOUTHWARD. NORTHEASTERLY COLD ADVECTION NOW
OCCURRING BETWEEN KOREA AND JAPAN COUPLED WITH A BUILDING RIDGE
OVER NORTHEASTERN CHINA WILL BLOCK THE STORM AND FORCE THIS ABRUPT
TRACK CHANGE WITHIN THE NEXT 12 TO 24 HOURS, PUSHING 22W NEAR
OKINAWA IN 36 TO 48 HOURS. DURING THIS PERIOD, ENVIRONMENTAL
CONDITIONS WILL BE UNFAVORABLE FOR INTENSIFICATION, WITH STRONG
WESTERLY SHEAR AND ENTRAINMENT OF MID-LATITUDE AIR LIKELY LIMITING
DEEP CONVECTIVE ACTIVITY NEAR THE STORM CENTER. HOWEVER, GALES ARE
LIKELY TO BE MAINTAINED FOR ABOUT 36 HOURS DUE TO GRADIENT-ENHANCED
FLOW AROUND THE NORTHERN AND WESTERN SIDES OF THE CIRCULATION.
THEREAFTER, WEAKENING BELOW GALE FORCE IS ANTICIPATED AS 22W
RETREATS SOUTHEASTWARD AWAY FROM THE COLD ADVECTION BELT PREVIOUSLY
SUPPORTING STRONGER WINDS. AFTER 48 HOURS, DYNAMICAL MODEL GUIDANCE
HAS COME INTO AGREEMENT ON A GRADUAL TURN NORTHEASTWARD TOWARD
HONSHU AS AN UPPER-LEVEL TROUGH DIGS INTO THE EAST CHINA SEA.
HOWEVER, GUIDANCE HAS BEGUN TO DIVERGE SIGNIFICANTLY REGARDING THE
PACE OF THIS NORTHEASTWARD MOVE, WITH ALONG-TRACK SPREAD EXCEEDING
500 NM AT TAU 120 THIS CYCLE. THIS UNCERTAINTY IS AT LEAST
PARTIALLY RELATED TO KROVANH'S INTERACTION WITH THE BROAD MONSOON
TROUGH AS IT LIFTS NORTHWARD, LIKELY WITH INVEST 97W EMBEDDED
WITHIN IT. THIS ALSO CONTRIBUTES UNCERTAINTY TO THE INTENSITY
FORECAST BEYOND TAU 72, AS MODELS DISAGREE REGARDING THE BROADNESS
OF 22W AND HOW MUCH MID-LATITUDE AIR ULTIMATELY GETS STIRRED INTO
THE LARGE CIRCULATING CAULDRON OF THE MONSOON TROUGH, SUPPRESSING
CONVECTION. THE JTWC INTENSITY FORECAST SHOWS NEAR-STEADY INTENSITY
OF 30 TO 35 KT FROM TAU 48 THROUGH 120, WITH SOME MODELS INDICATING
A POSSIBILITY OF MILD RESTRENGTHENING ON APPROACH TO JAPAN.

MODEL DISCUSSION: THE JTWC TRACK FORECAST IS PLACED CLOSE TO A
BLEND OF THE PREVIOUS FORECAST, THE PHYSICS-BASED MULTI-MODEL
CONSENSUS, AND THE AI-BASED MULTI-MODEL CONSENSUS. THIS FORECAST IS
A BIT FASTER BEYOND TAU 48 THAN THE PREVIOUS FORECAST, FOLLOWING
TODAY'S TREND IN MODEL GUIDANCE, AND HAS LOWER CONFIDENCE THAN
AVERAGE GIVEN THE IMMENSE ALONG-TRACK SPREAD. THE JTWC INTENSITY
FORECAST IS CLOSE TO THE MULTI-MODEL CONSENSUS THROUGHOUT AND IS
PLACED WITH MEDIUM CONFIDENCE.

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