Tropical Storm MEARI Advisory 8月12日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 09W (NINE) WARNING NR
003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 28.8N 135.9E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 435 NM SOUTH-SOUTHWEST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 02 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A LOW
LEVEL CIRCULATION WHICH HAS TUCKED UNDER A FLARE-UP IN CONVECTIVE
ACTIVITY, AFTER HAVING BEEN FULLY EXPOSED PREVIOUSLY. THE LOW LEVEL
CIRCULATION CENTER (LLCC) IS EMBEDDED WITHIN A LARGER REGION OF
CYCLONIC ROTATION, OUTLINED BY AN AREA OF FLARING CONVECTION. THE
INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON A
111234Z ASCAT-B PASS, ALONG WITH THE ANIMATED ENHANCED INFRARED
SATELLITE IMAGERY.  THE INITIAL INTENSITY IS SET AT 35 KNOTS WITH
HIGH CONFIDENCE BASED ON THE IMPROVING CONVECTIVE STRUCTURE AND THE
PREVIOUSLY MENTIONED ASCAT-B PASS. ADDITIONALLY, THE ASSESSED
INTENSITY IS INLINE WITH PGTW DVORAK FIX INTENSITY OF T2.5.
ENVIRONMENTAL CONDITIONS ARE CURRENTLY MODERATELY CONDUCIVE FOR
DEVELOPMENT WITH WARM SEA SURFACE TEMPERATURES (29-30C), AN
MODERATE TO STRONG EQUATORWARD OUTFLOW. ALTHOUGH THESE FAVORABLE
ENVIRONMENTAL PARAMETERS ARE OFFSET BY CIMSS AUTOMATED ANALYSIS
SHEAR VALUES OF 25-30 KNOTS. THE FAIR AMOUNT OF WIND SHEAR IS THE
INHIBITING FACTOR WHICH IS HAVING AN IMPACT ON THE NORTHERN
CONVECTIVE ENVELOPE AND CONTINUING TO STRUGGLE IN ALLOWING THE LLCC
TO MAINTAIN UNDER THE CONVECTION.
INITIAL WIND RADII BASIS: SCATTEROMETER DATA
CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED TO THE EAST.
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   KNES: T1.5 - 25 KTS
   CIMSS SATCON: 32 KTS AT 111235Z
   CIMSS ADT: 33 KTS AT 111740Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 25-30 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD
ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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: TS 09W HAD SINCE BEEN MOVING IN A SOMEWHAT
ERRATIC MOTION BUT IS NOW BECOMING MORE CONSOLIDATED, AND THE
SYSTEM HAS BEGUN TO SLOWLY START TO TRACK NORTH ALONG THE WESTERN
PERIPHERY OF THE STR TO THE EAST. BY TAU 24, TS 09W WILL BEGIN TO
ACCELERATE TO THE NORTHEAST AS IT ROUNDS THE EDGE OF THE
SUBTROPICAL RIDGE AXIS ALONG WITH ANOTHER STEERING RIDGE TO THE
WEST OF THE SYSTEM.  THE SYSTEM IS FORECAST TO CONTINUE TRACKING TO
THE NORTHEAST BEFORE MAKING LANDFALL ALONG THE IZU ENINSULA BETWEEN
TAU 36 AND TAU 48. TS 09W REMAINS IN HIGH NORTHERLY WIND SHEAR OF
25-30 KNOTS, HOWEVER IT HAS BEEN ABLE TO CONSOLIDATE INTO A
MORE DEFIND LLCC OVER THE PAST 12 HOURS. MODEL GUIDANCE DOES
SUGGEST THE WIND SHEAR WILL HOLD STRONG THROUGH TAUS 12 TO 24 ALONG
WITH A DECREASE IN UPPER LEVEL DIVERGENCE, WHICH WILL BE AN
INHIBITING FACTOR IN SIGNIFICANT INTENSIFICATION AT THE BEGINNING
OF THE FORECAST. HOWEVER, BETWEEN TUA 24 AND TAU 36 THE MODEL
GUIDANCE SUGGEST A DECREASE IN VERTICAL WIND SHEAR AHEAD OF AN
APPROACHING 200MB TROUGH. THE COMBINED EFFECT OF A DECREASE IN
VERTICAL WIND SHEAR, INCREASE IN POLEWARD UPPER LEVEL OUTFLOW
ALOFT, ALONG WITH HIGH SEA SURFACE TEMPERATURES (29-30C) WILL ALLOW
FOR A BRIEF WINDOW OF INTENSIFICATION UP TO 55 KTS JUST PRIOR TO
LANDFALL. AFTER TAU 48 AS THE SYSTEM EMERGES BACK OVER WATER IT
WILL BEGIN TO ACCELERATE QUICKLY TO THE NORTHEAST AS IT INTERACTS
WITH AN APPROACHING UPPER LEVEL TROUGH UPSTREAM. THEN BETWEEN TAU
72 AND TAU 96 THE UPPER LEVEL TROUGH BECOMES NEGATIVELY TILTED
ALLOWING FOR EXTRATROPICAL TRANSITION, ADDITIONALLY, THE NEGATIVE
EFFECTS OF MUCH COOLER SEA SURFACE TEMPERATURES WILL ALLOW FOR THE
SYSTEM TO STEADILY DECREASE IN INTENSITY AS IT ULTIMATELY BECOMES A
COLD CORE VERTICALLY STACKED SYSTEM AS IT APPROACHES THE KAMCHATKE
PENINSULA.
MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE REMAINS IN OVERALL GOOD
AGREEMENT ON THE TRACK FORECAST WITH ALL CONSENSUS MODELS IN TIGHT
AGREEMENT THROUGH TAU 72. BY TAU 96 AS THE SYSTEM INTERACTS WITH
THE APPROACHING UPPER LEVEL TROUGH, THERE BECOMES MORE OF A SPREAD
IN GUIDANCE UP TO 300NM. THE JTWC FORECAST REMAINS CONSISTENT WITH
THE PREVIOUS FORECAST THROUGH TAU 36. BETWEEN TAU 36 AND TAU 48 THE
TRACK HAS SHIFTED SLIGHTLY TO THE EAST AND THE MAJORITY OF THE
NUMERICAL MODELS HAVE ALL COME INTO BETTER AGREEMENT. BY TAU 72 THE
TRACK REMAINS INLINE WITH THE PREVIOUS FORECAST BEFORE ACCELERATING
TO THE NORTHEAST THROUGH TAU 96 FOR THESE REASONS THE JTWC TRACK
FORECAST IS PLACED WITH MEDIUM CONFIDENCE. INTENSITY GUIDANCE
REMAINS INLINE WITH THE PREVIOUS FORECAST AND CONSISTENT WITH
PREVIOUS MODEL RUNS. RELIABLE MODEL INTENSITY GUIDANCE INDICATES AN
INTENSIFICATION TREND THROUGH TAU 36 AND TAU 48 AFTER WHICH ALL MODELS
WEAKEN THE SYSTEM, WHICH IS IN LINE WITH THE JTWC INTENSITY FORECAST.
DUE TO THE RANGE OF MODEL INTENSITY TRENDS THE JTWC INTENSITY FORECAST
IN PLACED WITH LOW CONFIDENCE.
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: LOW
   INTENSITY 72-120 HR: LOW//
NNNN
NNNN