Advisories

WDPN33 PGTW 110900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 14W (CHAN-HOM) WARNING NR 
018//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 36.5N 142.0E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 133 NM EAST-NORTHEAST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 25 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
STORM (TS) 14W (CHAN-HOM) QUICKLY APPROACHING THE EASTERN COAST OF
HONSHU AS A FULLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC)
BELEAGUERED BY HIGH MIDLEVEL SHEAR AND SIGNIFICANT DRY AIR
ENTRAINMENT. ENVIRONMENTAL ANALYSIS REVEALS A HIGHLY UNFAVORABLE
ENVIRONMENT, CHARACTERIZED BY HIGH (30-35 KTS) VERTICAL WIND SHEAR
(VWS), COOL (23-24 C) SEA SURFACE TEMPERATURES (SST), DEEP LAYER
DRY AIR ENTRAINMENT, POOR EQUATORWARD OUTFLOW, AND LAND INTERACTION
ALONG THE WESTERN PERIPHERY OF THE STORM. 14W IS POLEWARD OF THE
KUROSHIO CURRENT AND HAS LOST THE OCEANIC SUPPORT IT PROVIDED. THE
LOW LEVEL CIRCULATION REMAINS INTENSE, DESPITE THE DEGRADING
ENVIRONMENT AND DETERIORATING APPEARANCE IN ANIMATED MSI. THE
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE FULLY
EXPOSED LLCC. THE INITIAL INTENSITY OF 40 KTS IS ASSESSED WITH
MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK FIXES AND CIMSS
ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE NORTH
AND A DEEP UPPER LOW TO THE SOUTH


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T2.5 - 35 KTS
   CIMSS SATCON: 51 KTS AT 110600Z
   CIMSS ADT: 41 KTS AT 110700Z
   CIMSS AIDT: 38 KTS AT 110700Z
   CIMSS D-MINT: 40 KTS AT 110402Z
   CIMSS D-PRINT: 35 KTS AT 110700Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY UNFAVORABLE
   VWS: 30-35 KTS
   SST: 23-24 CELSIUS
   OUTFLOW: WEAK EQUATORWARD
   OTHER FACTORS: DEEP LAYER DRY AIR ENTRAINMENT

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 14W IS FORECAST TO CONTINUE TRACKING
WEST-SOUTHWESTWARD WHILE IT REMAINS UNDER THE INFLUENCE OF THE STR
TO THE NORTH AND DEEP-LAYER LOW TO THE SOUTH, WHICH, IN
CONJUNCTION, ARE PRODUCING A TIGHT STEERING GRADIENT AND INDUCING
QUICK TRACK SPEEDS FOR 14W. LANDFALL IN HONSHU IS IMMINENT.
CHAN-HOM IS FORECAST TO SPEND LESS THAN 24 HOURS OVER LAND,
REEMERGING OVER WATER IN THE SEA OF JAPAN BETWEEN TAU 12-24 AND
REMAINING OVER WATER UNTIL DISSIPATING BY TAU 36. REGARDING
INTENSITY, 14W WILL CONTINUE GRADUAL WEAKENING UP UNTIL LANDFALL IN
HONSHU, AT WHICH POINT, THE ELEVATED TERRAIN IS EXPECTED TO SHRED
THE LOWER LEVEL CIRCULATION. CHAN-HOM IS FORECAST TO LIMP ITS WAY
BACK OVER WATER BEFORE TAU 24, BUT THE ENVIRONMENT WILL CONTINUE TO
BE HIGHLY UNFAVORABLE AND CHAN-HOM WILL BE UNABLE TO RECOVER FROM
THE SEVERE WEAKENING IT EXPERIENCED OVER THE MOUNTAINOUS TERRAIN.

MODEL DISCUSSION: DETERMINISTIC MODEL TRACK GUIDANCE IS IN STRONG
AGREEMENT THROUGHOUT THE FORECAST PERIOD, SUPPORTING THE JTWC TRACK
FORECAST WITH HIGH CONFIDENCE. LIKEWISE, THE RELIABLE INTENSITY
AIDS ARE IN STRONG AGREEMENT IN STEADY WEAKENING THROUGH
DISSIPATION AT TAU 36. AS A RESULT, THE JTWC INTENSITY FORECAST IS
ASSESSED WITH HIGH CONFIDENCE.

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