Advisories

WDPN31 PGTW 080900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 22W (KROVANH) 
WARNING NR 029//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 31.1N 132.8E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 195 NM SOUTH OF IWAKUNI, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
DEPRESSION 22W (KROVANH) WITH A MOSTLY EXPOSED LOW-LEVEL
CIRCULATION CENTER (LLCC) AND PERSISTENT CONVECTION DISPLACED TO
THE NORTHWEST OF THE CENTER. THE SHEAR DIRECTION APPEARS TO BE
SHIFTING TO SOUTHERLY BASED ON THE DIRECTION OF THE FAINT
UPPER-LEVEL CLOUDS RUNNING ACROSS THE VORTEX. THE STRUCTURE OF THE
LLCC HAS ALSO BECOME MORE IRREGULAR OVER THE PAST 6 HOURS AS THE
SYSTEM APPROACHES THE FRONTAL BOUNDARY OVER HONSHU. NONETHELESS,
THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE
EXPOSED LLCC IN ANIMATED MSI. THE INITIAL INTENSITY OF 30 KTS IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK FIXES
AND CIMSS INTENSITY ESTIMATES LISTED BELOW. ENVIRONMENTAL ANALYSIS
INDICATES THAT 22W IS IN AN UNFAVORABLE ENVIRONMENT CHARACTERIZED
BY STRONG POLEWARD OUTFLOW ALOFT AND WARM (28-29 C) SEA SURFACE
TEMPERATURES GREATLY OFFSET BY MODERATE TO HIGH (20-25 KTS)
SOUTHERLY VERTICAL WIND SHEAR AND EXTENSIVE DRY AIR ENTRAINMENT.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: THE NORTHWESTERN FLANK OF THE
SUBTROPICAL RIDGE (STR) CENTERED SOUTHEAST OF JAPAN

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T1.5 - 25 KTS
   CIMSS ADT: 32 KTS AT 080610Z
   CIMSS AIDT: 38 KTS AT 080610Z
   CIMSS D-MINT: 32 KTS AT 080431Z
   CIMSS D-PRINT: 30 KTS AT 080610Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 20-25 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: SIGNIFICANT DRY AIR ENTRAINMENT

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TD 22W IS FORECAST TO BEGIN TURNING MORE
NORTHEASTWARD OVER THE NEXT 12 HOURS AS IT ROUNDS THE NORTHWESTERN
PERIPHERY OF THE STR. AFTER TAU 12, THE SYSTEM WILL SKIRT THE
SOUTHERN COAST OF JAPAN, NEAR THE SHIKOKU AND KANSAI REGIONS WITH
INCREASING TRACK SPEEDS. 22W WILL BE HEAVILY IMPACTED BY THE
STATIONARY FRONTAL BOUNDARY THAT IS CURRENTLY DRAPED ACROSS HONSHU,
CAUSING THE CIRCULATION TO BECOME STRETCHED AND LIKELY MOVE
UNPREDICTABLY. IN TERMS OF INTENSITY, 22W IS FORECAST TO MAINTAIN
ITS CURRENT INTENSITY OF 30 KTS THROUGH TAU 12, MOSTLY DUE TO THE
WARM WATERS AND STRONG POLEWARD OUTFLOW CHANNEL. FOLLOWING TAU 12,
SOUTHWESTERLY SHEAR WILL SIGNIFICANTLY INCREASE, CAUSING THE VORTEX
TO ERODE AND SHALLOW OUT. ONCE THE SYSTEM BEGINS TO INTERACT WITH
THE MOUNTAINOUS TERRAIN OF JAPAN, 22W WILL QUICKLY WEAKEN WITH
DISSIPATION EXPECTED TO OCCUR NEAR TAU 24. EVEN THOUGH THE VORTEX
ASSOCIATED WITH 22W BECOMES ABSORBED WITHIN THE FRONTAL BOUNDARY,
LOCALIZED AREAS OF ENHANCED WINDS DUE TO TERRAIN FUNNELING MAY
PERSIST IN AREAS SUCH AS WAKAYAMA BAY AND ISE BAY.

MODEL DISCUSSION: MODEL TRACK GUIDANCE NOW AGREES ON THE
NORTHEASTWARD TURN THROUGH TAU 24 WITH MINIMAL CROSS-TRACK SPREAD.
HOWEVER, ALONG-TRACK SPREAD CONTINUES TO BE HIGH DUE TO MODELS
VARYING IN THE SPEED OF ADVANCE AROUND THE RIDGE. THE JTWC TRACK
FORECAST IS PLACED NEAR THE MULTI-MODEL CONSENSUS THROUGHOUT THE
SHORT FORECAST PERIOD WITH MEDIUM CONFIDENCE. INTENSITY GUIDANCE
AGREES ON RAPID DISSIPATION AFTER LANDFALL, THOUGH THE GFS DOES
SHOW A BRIEF PERIOD OF INTENSIFICATION TO 35 KTS AT TAU 12, JUST
BEFORE LANDFALL OCCURS. THE JTWC INTENSITY FORECAST IS ALSO PLACED
NEAR THE CONSENSUS WITH MEDIUM CONFIDENCE.

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