Tropical Storm NANMADOL Advisory 9月17日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 16W (NANMADOL) WARNING NR
017//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 25.5N 133.8E
   INITIAL INTENSITY: 135 KTS
   GEOGRAPHIC REFERENCE: 329 NM EAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 52 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
PERFECTLY SYMMETRICAL, VERY WARM (21C), 21NM DIAMETER EYE,
SURROUNDED BY A LARGE ENVELOPE OF DEEP CENTRAL CONVECTION.
ADDITIONALLY, A 161702Z AMSR2 89GHZ MICROWAVE IMAGE REVEALS
WELL-DEFINED FEEDER BANDS WRAPPING AROUND THE OUTER PERIPHERY OF
THE CIRCULATION, WITH THE DEEPEST INNER CORE CONVECTION WRAPPING
AROUND THE NORTHERN SEMICIRCLE. THE INITIAL POSITION IS PLACED WITH
HIGH CONFIDENCE BASED ON THE WELL DEFINED EYE FEATURE IN THE EIR
LOOP AND FORWARD EXTRAPOLATION OF THE LLCC IN THE AMSR2 PASS. THE
INITIAL SUPER TYPHOON (STY) INTENSITY IS ASSESSED AS 135 KNOTS WITH
HIGH CONFIDENCE BASED ON THE IMPRESSIVE SATELLITE DEPICTION, ALONG
WITH THE PGTW DVORAK ESTIMATE OF T7.0, CIMSS ADT OF 135 KTS, AND
THE CIMSS SATCON OF 130 KTS.
INITIAL WIND RADII BASIS: PERSISTENCE
CURRENT STEERING MECHANISM: DEEP LAYER SUBTROPICAL RIDGE (STR) TO
THE NORTHEAST
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T7.0 - 140 KTS
   RJTD: T7.0 - 140 KTS
   KNES: T6.5 - 127 KTS
   CIMSS SATCON: 130 KTS AT 161608Z
   CIMSS ADT: 135 KTS AT 161840Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 0-5 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG RADIAL
ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: MEDIUM
3. FORECAST REASONING.
SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.
FORECAST DISCUSSION: SUPER TYPHOON 16W (NANMADOL) IS FORECAST TO
TRACK NORTHWESTWARD ALONG THE WESTERN PERIPHERY OF THE SUBTROPICAL
RIDGE (STR) TO THE NORTHEAST. THE CURRENT ENVIRONMENT IS HIGHLY
FAVORABLE FOR CONTINUED INTENSIFICATION, WITH LOW (0-5 KTS) VERTICAL
WIND SHEAR (VWS), WARM (29-30C) SEA SURFACE TEMPERATURES (SSTS), AND
STRONG OUTFLOW IN ALL QUADRANTS. SSTS ARE TO REMAIN WARM ALONG THE
FORECAST TRACK, WITH OVERALL FAVORABLE RADIAL OUTFLOW OVER THE NEXT 24
HOURS. WITH A FORECAST PEAK INTENSITY OF 140 KNOTS TO BE REACHED BY
TAU 12 AS THE SYSTEM PASSES THE ISLAND OF MINAMI DAITO JIMA. BY TAU
24, THE SYSTEM IS FORECAST TO TRACK NORTH-NORTHWESTERLY WHILE ALSO
TRANSITING OVER AN AREA OF LOWER OCEAN HEAT CONTENT (OHC). THIS WILL
ULTIMATELY PREVENT ANY FURTHER INTENSIFICATION WITH A GRADUAL DECREASE
IN INTENSITY AS THE SYSTEM CONTINUES POLEWARD. BETWEEN TAU 36 AND TAU
48, 16W WILL BEGIN TO GRADUALLY SLOW ITS FORWARD MOTION AS IT NEARS
THE AXIS OF THE SUBTROPICAL RIDGE. AS THIS OCCURS THE SYSTEM WILL ALSO
BEGIN TO BE INFLUENCED BY AN APPROACHING UPPER-LEVEL TROUGH. AS THIS
INTERACTION OCCURS THE SYSTEM WILL SHARPLY RECURVE TOWARD THE EAST-
NORTHEAST, MAKING LANDFALL INTO KYUSHU AT TAU 48. ADDITIONALLY, THE
UPPER-LEVEL TROUGH INTERACTION WILL INDUCE AN INCREASE IN VWS, ALONG
WITH LAND INTERACTION, WHICH WILL RESULT IN A DECREASE IN THE
INTENSITY TO 95 KTS. BEYOND TAU 72, THE FORECAST TRACK CONTINUES
NORTHEASTWARD OVER HONSHU, WHILE THE SYSTEM WILL STEADILY WEAKEN
FURTHER DUE TO LAND INTERACTION AS WELL AS AN INCREASE IN VERTICAL
WIND SHEAR WHILE BECOMING EXTRATROPICAL. BY TAU 96, 16W WILL EXIT BACK
OVER OPEN WATER AND ACCELERATE TO THE NORTHEAST INTO THE MID-LATITUDE
WESTERLIES WHILE UNDERGOING FULL EXTRATROPICAL TRANSITION BY TAU
120.
MODEL DISCUSSION: NUMERICAL MODELS ARE IN TIGHT AGREEMENT THROUGH
TAU 36 WITH ONLY AN 65NM SPREAD IN SOLUTIONS. BY TAU 48, THE MODEL
TRACKERS SPREAD TO 100NM, WITH NOTABLE MEMBERS, SUCH AS NAVGEM,
ECMWF, AND ECMWF ENSEMBLE MEAN TO THE LEFT OF MANY OF THE OTHER
MEMBERS. GIVEN THE SPREAD AND UNCERTAINLY THE JTWC FORECAST IS PLACED
SLIGHTLY TO THE LEFT OF THE MULTI-MODEL CONSENSUS. WHICH RESULTS IN A
TRACK TRAJECTORY THAT MAKES LANDFALL INTO KYUSHU, JUST SOUTH OF SASEBO
BY TAU 48. BETWEEN TAU 72 AND TAU 96, THERE IS SOME ADDITIONAL CROSS
TRACK SPREAD IN THE GUIDANCE, WITH THE JTWC TRACK REMAINING CLOSE TO
THE CONSENSUS MEAN AND SIMILAR TO THE PREVIOUS TRACK. BEYOND TAU 96,
UNCERTAINTY INCREASES FURTHER WITH DIFFERENCES IN THE TIMING AND
FORWARD SPEED AT WHICH THE SYSTEM UNDERGOES EXTRATROPICAL TRANSITION.
THEREFORE, THERE IS LOW CONFIDENCE IN THE LATER PART OF THE TRACK
FORECAST, WITH THE JTWC FORECAST REMAINING CLOSE TO THE MULTI-MODEL
CONSENSUS. THE JTWC INTENSITY FORECAST IS ABOVE THE MULTI-MODEL
CONSENSUS DUE TO CONTINUED INTENSIFICATION OVER THE NEXT 12 HOURS.
WHILE REMAINING INLINE WITH GUIDANCE AND CLOSE TO THE PREVIOUS
FORECAST THROUGHOUT THE REMAINDER OF THE FORECAST.
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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