Tropical Storm HINNAMNOR Advisory 9月4日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (HINNAMNOR) WARNING NR 027//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 25.1N 124.6E
   INITIAL INTENSITY: 90 KTS
   GEOGRAPHIC REFERENCE: 192 NM WEST-SOUTHWEST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 42 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS THAT TY
12W CONTINUES TO CONSOLIDATE AND HAS STARTED ITS INTENSIFICATION
PHASE, HAVING DEPARTED THE COOL SST POOL AND MOVED INTO THE HOT TUB
OF THE EAST CHINA SEA. ANIMATED RADAR DATA AND A 031733Z AMSR2
89GHZ MICROWAVE IMAGE SHOWED THAT THE LOW LEVEL EYE FEATURE HAS
CONTRACTED QUITE A BIT SINCE 1200Z, NOW ESTIMATED BY RADAR TO BE NO
MORE THAN 10-15NM WIDE. THESE DATASETS ALSO SHOW A THICK INNER
EYEWALL SURROUNDED BY A MOAT AND MULTIPLE CONCENTRIC BANDS OF
CONVECTION EXTENDING OUT ABOUT 75NM OR SO. WHILE THE CORE OF THE
SYSTEM IS VERY SMALL, THE CDO EXTENDS ONLY ABOUT 100NM OUT FROM THE
CENTER, THE GALE FORCE WIND FIELD IS EXPANSIVE, EXTENDING PAST
OKINAWA TO THE NORTHEAST AND TO THE NORTHERN PART OF THE TAIWAN
STRAIT TO THE WEST. THE INITIAL POSITION IS ASSESSED WITH HIGH
CONFIDENCE BASED ON THE RADAR AND MICROWAVE EYE FEATURES. MEANWHILE
THE INITIAL INTENSITY OF 90 KNOTS IS ASSESSED WITH HIGH CONFIDENCE
BASED ON THE T5.0 ESTIMATES FROM ALL AGENCIES AND THE ADT, AND
RADAR ESTIMATED VELOCITIES OF 40-50 METERS PER SECOND. THE SATCON
IS BEING PULLED TOO HIGH DUE TO A UNREALISTIC ATMS ESTIMATE OF 119
KNOTS.
INITIAL WIND RADII BASIS: PERSISTENCE, AMSR2 WINDSPEED PRODUCT AND
SURFACE OBSERVATIONS
CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) TO THE EAST.
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T5.0 - 90 KTS
   RJTD: T5.0 - 90 KTS
   KNES: T5.0 - 90 KTS
   CIMSS SATCON: 104 KTS AT 031652Z
   CIMSS ADT: 90 KTS AT 031740Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD
   OTHER FACTORS: DRY AIR AND NORTHWESTERLY CONVERGENT FLOW TO THE
WEST
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: HAVING CROSSED THE SOUTHERN RYUKUS, TY 12W
APPEARS TO BE FINALLY EMBARKING ON ITS RE-INTENSIFICATION PHASE AS
IT MOVES INTO THE SHALLOW, WARM WATERS OF THE EAST CHINA SEA. THE
SYSTEM IS FORECAST TO TRACK NORTHWARD OVER THE NEXT 24 HOURS BEFORE
TURNING SHARPLY NORTHEASTWARD AS IT ROUNDS THE STR AXIS AHEAD OF AN
APPROACHING MID-LATITUDE TROUGH. TRACK SPEEDS ARE EXPECTED TO BE
FAIRLY SLOW, LESS THAN 10 KNOTS, THROUGH TAU 36 BUT ONCE THE SYSTEM
TURNS NORTHEAST, IT WILL RAPIDLY PICK UP SPEED TO MORE THAN 20
KNOTS BY TAU 48, QUICKLY MOVING INTO THE SEA OF JAPAN BY TAU 72.
WHILE THE SYSTEM HAS STARTED TO CONSOLIDATE, WITH A DECREASE IN THE
EYE DIAMETER, THE CONTINUED PRESENCE OF MULTIPLE CONCENTRIC RAIN
BANDS AND THE DRY, CONVERGENT FLOW TO THE WEST, MEANS THAT IT STILL
HAS SOME WORK TO DO BEFORE REALLY TAKING OFF IN TERMS OF INTENSITY.
HOWEVER, GLOBAL MODEL FIELDS SUGGEST THE ATMOSPHERE OUT FRONT OF
THE SYSTEM WILL MOISTEN OVER THE NEXT 24 HOURS OR SO WHICH SOLVES
ONE ISSUE. MEANWHILE AN UNSEASONABLY COLD AND DEEP UPPER-LEVEL LOW
AND DYNAMIC TROUGH, CURRENTLY OVER LAKE BAIKAL, WILL DIVE SOUTH
OVER THE NEXT TWO DAYS AND BE OVER MANCHURIA BY TAU 48. THE DEEP
TROUGH ASSOCIATED WITH THIS LOW WILL HAVE TWO MAIN EFFECTS. FIRST,
IT WILL PROVIDE A ROBUST POLEWARD OUTFLOW CHANNEL FOR TY 12W TO TAP
INTO BETWEEN TAU 24 AND 36, ENABLING A BURST OF RAPID
INTENSIFICATION. THEN BEGINNING AT TAU 48, TY 12W WILL BEGIN EXTRA-
TROPICAL TRANSITION AS IT MOVES INTO PHASE WITH THE TROUGH ALOFT. THE
SYSTEM IS FORECAST TO PEAK AT 115 KNOTS BY TAU 36, BUT THEN THE
RAPIDLY INCREASING SHEAR AND DECREASING SSTS WILL MARK THE START OF A
RAPID WEAKENING TREND. HOWEVER, TY 12W IS STILL EXPECTED TO BE A
STRONG TYPHOON AS IT MAKES ITS LANDFALL ALONG THE SOUTHERN COAST OF
KOREA, EVEN WHILE IT STARTS THE ETT PROCESS. THE SYSTEM WILL
TRANSITION TO A STRONG, WARM SECLUSION TYPE EXTRA-TROPICAL LOW IN THE
NORTHERN SEA OF JAPAN NO LATER THAN TAU 72.
MODEL DISCUSSION: TRACK GUIDANCE REMAINS IN VERY GOOD AGREEMENT AND
CONSISTENT WITH PREVIOUS MODEL RUNS. CROSS TRACK SPREAD REMAINS
LESS THAN 100NM THROUGH THE FORECAST PERIOD, THOUGH ALONG-TRACK
SPREAD BEGINS TO INCREASE AT TAU 48, INCREASING TO 480NM BY TAU 72,
THOUGH NOT UNEXPECTED FOR A TRANSITIONING EXTRA-TROPICAL LOW. THE
JTWC FORECAST REMAINS CONSISTENT WITH BOTH THE PREVIOUS FORECAST
AND THE MULTI-MODEL CONSENSUS WITH HIGH CONFIDENCE. INTENSITY
GUIDANCE REMAINS MIXED, WITH THE DECAY-SHIPS STUBBORNLY REFUSING TO
ACKNOWLEDGE THE FAVORABLE ENVIRONMENTAL CONDITIONS AND WEAKENING
THE SYSTEM FROM TAU 00, AS DOES THE GFS DETERMINISTIC MEMBER. THE
HWRF HAS BACKED OFF SIGNIFICANTLY SINCE YESTERDAY AND NOW LIES NEAR
THE CONSENSUS MEAN, WITH A PEAK AROUND 100 KNOTS. MEANWHILE THE
COAMPS-TC (GFS VERSION) AND RAPID INTENSIFICATION AID (RIDE) SHOW A
PEAK OF 115 KNOTS BY TAU 36. FROM AN ENVIRONMENTAL PERSPECTIVE, IF
ALL THE VARIOUS PARTS SUCCESSFULLY LINE UP, THIS PEAK IS REASONABLE
AND THE JTWC FORECAST CLOSELY FOLLOWS THE COAMPS-TC THROUGH THE
FORECAST PERIOD. HOWEVER, IF ONLY ONE FACTOR DOES NOT COME THROUGH
OR THE TIMING IS OFF, THE PEAK COULD BE SLIGHTLY LOWER. THUS THERE
IS ONLY MEDIUM CONFIDENCE IN THE JTWC FORECAST.
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   INTENSITY 0 - 72 HR: MEDIUM//
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