Tropical Storm TALAS Advisory Fr, 23.09.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 17W (TALAS) WARNING NR
006//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 30.8N 134.8E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 250 NM SOUTHEAST OF IWAKUNI, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS AN IMPROVED
CONVECTIVE STRUCTURE, WITH A PARTIALLY EXPOSED LOW LEVEL
CIRCULATION CENTER (LLCC) THAT HAS BECOME SLIGHTLY MORE TUCKED
UNDER THE DEEP PERSISTENT CONVECTION. AN EARLIER 222121Z SSMIS
91GHZ MICROWAVE IMAGE REVEALS SHALLOW BANDING WRAPPING INTO A LOW
LEVEL CIRCULATION CENTER POSITIONED ALONG THE SOUTHWESTERN EDGE OF
A CURVED CONVECTIVE BAND. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON MSI IMAGERY AND THE SSMIS MICROWAVE IMAGERY.
THE INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON THE CURRENT CONVECTIVE STRUCTURE AS WELL AS A COMBINATION
OF AGENCY DVORAK INTENSITY ESTIMATES, PGTW T2.0, RJTD T2.0 AND CIMSS
ADT 34 KTS.
INITIAL WIND RADII BASIS: PERSISTENCE
CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE EAST
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T2.0 - 30 KTS
   RJTD: T2.0 - 30 KTS
   CIMSS SATCON: 46 KTS AT 222121Z
   CIMSS ADT: 34 KTS AT 222340Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG POLEWARD
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: AFTER A BRIEF INTENSIFICATION PERIOD TO 35
KTS, TS 17W WILL LIKELY MAINTAIN ITS INTENSITY BASED ON THE OVERALL
MARGINALLY FAVORABLE ENVIRONMENT, WHERE VERTICAL WIND SHEAR (VWS)
IS AN INHIBITING FACTOR AND IS FORECAST TO INCREASE AS THE SYSTEM
CONTINUES TO MOVES POLEWARD. OVER THE NEXT 12-24 HOURS THE JTWC
OFFICIAL TRACK SHOWS THE SYSTEM TURNING SHARPLY TO THE NORTHEAST
BEFORE MAKING LANDFALL INTO HONSHU. BY TAU 24, AFTER THE SYSTEM
MAKES LANDFALL IT WILL BEGIN TO DECREASE IN INTENSITY DUE TO LAND
INTERACTION WHILE ALSO INTERACTING WITH AN APPROACHING UPPER-LEVEL
TROUGH TO THE NORTHWEST OF THE SYSTEM. THIS INTERACTION BETWEEN THE
SYSTEM AND THE UPPER LEVEL FEATURE WILL INDUCE INCREASED VERTICAL
WIND SHEAR (VWS) WHICH WILL FURTHER DISRUPT THE SYSTEMS TROPICAL
CONVECTIVE STRUCTURE. AFTER TAU 36, 17W WILL CONTINUE TO WEAKEN
FURTHER DUE TO CONTINUED LAND INTERACTION FROM THE RUGGED TERRAIN.
THEREFORE, SIGNIFICANTLY IMPACTING THE SYSTEMS STRUCTURE, WITH
DISSIPATING FORECAST BY TAU 48.
MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE REMAINS IN TIGHT
AGREEMENT WITH ONLY A 40NM SPREAD UP TO TAU 24. THEREAFTER, THE
NUMERICAL MODEL GUIDANCE SPREADS ONCE THE SYSTEM MAKES LANDFALL,
WITH INCREASES IN BOTH CROSS TRACK AND ALONG TRACK VARIABILITY.
LIKELY DUE TO HOW MODELS ARE STRUGGLING TO RESOLVE THE WEAK
STRUCTURE OF THE CIRCULATION INDUCED BY INCREASED VERTICAL WIND
SHEAR AND TERRAIN INTERACTION. THUS, THE JTWC OFFICIAL TRACK
FORECAST IS PLACED WITH MEDIUM CONFIDENCE. THE JTWC INITIAL
INTENSITY IS CLOSE TO THE MULTI-MODEL CONSENSUS WITH MEDIUM
CONFIDENCE THROUGHOUT THE FORECAST PERIOD.
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM//
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