Tropical Storm HINNAMNOR Advisory Sa, 03.09.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (HINNAMNOR) WARNING NR 024//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 23.1N 124.7E
   INITIAL INTENSITY: 80 KTS
   GEOGRAPHIC REFERENCE: 265 NM SOUTHWEST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 40 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS THAT WHILE TY
12W IS SLOWLY INTENSIFYING AND ATTEMPTING TO CLEAR OUT AN EYE, IT
HAS YET TO PUT THE PEDAL DOWN. CONVECTIVE HOT TOWERS HAVE BEEN
DEVELOPING AND ROTATING AROUND THE CENTER CONSISTENTLY OVER THE
PAST SIX HOURS BUT HAVE YET TO DEVELOP OR SUSTAIN A CONSISTENT
EYEWALL. PART OF THE ISSUE LIES IN THE WEDGE OF VERY DRY AIR
BETWEEN 450-300MB AND 50-55 KNOT WINDS SEEN IN THE ISHIKAGIJIMA
1200Z SOUNDING, WHICH IS INHIBITING DEVELOPMENT ON THE NORTHERN
EDGE OF THE SYSTEM, BORNE OUT BY THE STRUGGLING STRUCTURE ON THAT
SIDE OF THE SYSTEM. A 022230Z SSMIS 91GHZ MICROWAVE IMAGE REVEALED
AN ASYMMETRIC CONVECTIVE STRUCTURE, WITH THE BULK OF DEEP
CONVECTION LIMITED TO THE SOUTHERN SECTORS WITH WEAKER CONVECTION
AROUND THE NORTHERN PORTION OF THE CORE. A 022136Z SENTINEL-1A SAR
PASS REVEALED THAT IN THE LOW LEVELS, THE STRUCTURE IS MUCH BETTER,
WITH A 25-NM EYE WITH A SMALL CORE OF ENHANCED STORM FORCE WINDS.
HOWEVER THE CORE IS EXTREMELY SMALL AND THE WIND FIELD HIGHLY
ASYMMETRIC WITH HURRICANE FORCE WINDS LIMITED TO THE EASTERN
SECTORS, ABOUT 50 TO 75 NM OUT. THE SAR PASS IN CONJUNCTION WITH A
RADAR EYE FEATURE LENT HIGH CONFIDENCE TO THE INITIAL POSITION. THE
INITIAL INTENSITY OF 80 KNOTS IS ASSESSED WITH HIGH CONFIDENCE
BASED ON THE SAR FIX OF 76 KNOTS, THE BULK OF AGENCY FIXES, THE
AIDT OF 78 KNOTS, AS WELL AS SOME NEW DEVELOPMENTAL CIMSS PRODUCTS
INCLUDING DEEP MULTINET (79 KTS) AND THE OPEN-AIIR (75 KTS). THE
SYSTEM IS WOBBLING NORTHWARD AT A MODEST PACE, ALONG THE WESTERN
SIDE OF A DEEP SUBTROPICAL RIDGE (STR) TO THE EAST.
INITIAL WIND RADII BASIS: SAR DATA
CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP SUBTROPICAL
RIDGE (STR) TO THE EAST.
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T4.5 - 77 KTS
   RJTD: T5.0 - 90 KTS
   KNES: T4.5 - 77 KTS
   CIMSS SATCON: 68 KTS AT 022231Z
   CIMSS ADT: 84 KTS AT 022340Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: STRONG RADIAL
   OTHER FACTORS: MID-LEVEL SHEAR AND DRY AIR TO THE NORTH.
ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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: TY 12W HAS DEFINITELY STARTED ITS NORTHWARD
MOVEMENT OVER THE PAST SIX HOURS, THOUGH IT IS STILL WOBBLING A BIT
EITHER SIDE OF DUE NORTH. TRACK SPEED IS STARTING TO PICK UP, NOW
UP TO ABOUT SEVEN KNOTS AS THE STEERING RIDGE TO THE EAST
STRENGTHENS. TY 12W IS FORECAST TO CONTINUE TRACKING JUST A SHADE
WEST OF DUE NORTH OVER THE NEXT 36 HOURS, PASSING JUST EAST OF
ISHIKAGIJIMA IN THE NEXT 12 HOURS, THEN ENTERING THE EAST CHINA
SEA. THE STEERING RIDGE WILL BEGIN TO REORIENT AROUND TAU 36,
ALLOWING TY 12W TO TAKE A FAIRLY SHARP NORTHEASTWARD TURN BY TAU
48. SHORTLY AFTER THIS POINT, IT WILL SLAM THE FOOT ON THE GAS AND
ACCELERATE TO THE NORTHEAST ALONG THE STRONG GRADIENT BETWEEN THE
RIDGE TO THE EAST AND A STRONG MID-LATITUDE TROUGH APPROACHING FROM
THE WEST, PASS OVER THE SOUTHERN COAST OF KOREA AND THEN EXIT INTO
THE SEA OF JAPAN, MOVING AT OVER 25 KNOTS BY THIS POINT. IN TERMS
OF INTENSITY, WHILE BULK SHEAR IS LOW, THIS DOES NOT TELL THE WHOLE
STORY. THE SYSTEM IS SLOWLY INTENSIFYING BUT IS FACING SOME
RESISTANCE FROM MID-LEVEL SHEAR AND UPPER-LEVEL DRY AIR TO THE
NORTH AS MENTIONED ABOVE. AN ADDITIONAL INHIBITING FACTOR IS SOME
PRESSURE FROM NORTHERLY, CONVERGENT FLOW TO THE WEST, WHICH IS
BLOCKING OUTFLOW IN THAT DIRECTION. GLOBAL MODEL ANALYSIS INDICATES
THE WEDGE OF DRY AIR TO THE NORTH, AS WELL AS THE MID-LEVEL SHEAR
SHOULD DECREASE OVER THE NEXT 12 HOURS, WHILE THE
NORTH-NORTHEASTERLY FLOW OFF TO THE WEST SHOULD RECEDE AWAY FROM
THE SYSTEM, ALLOWING FOR INCREASED RADIAL OUTFLOW. ADDITIONALLY AS
THE SYSTEM MOVES FURTHER NORTH AWAY FROM THE UPWELLING INDUCED COOL
POOL, SSTS WILL INCREASE TO OVER 30C, PROVIDING AMPLE ENERGY FOR
INTENSIFICATION. THE PEAK INTENSITY IS INCREASED TO 115 KNOTS BY
TAU 48 BUT IT IS POSSIBLE THAT THE PEAK MAY BE SLIGHTLY HIGHER AND
OCCUR SLIGHTLY LATER, AS THE SYSTEM HAS A BRIEF WINDOW, TO ABOUT TAU
60, TO TAP INTO SOME GOOD POLEWARD OUTFLOW PRIOR TO THE ONSET OF
HIGH SHEAR. REGARDLESS, BY TAU 72 SHEAR WILL INCREASE DRAMATICALLY,
THE SYSTEM WILL MOVE OVER COOLER WATERS LESS THAN 27C AND WILL
BEGIN TO INTERACT WITH THE TERRAIN OF SOUTHERN KOREA, AND WEAKEN TO
90 KNOTS. AS IT CROSSES THE COAST OF KOREA, TY 12W WILL BEGIN TO
INTERACT WITH THE MID-LATITUDE WESTERLY FLOW ALOFT AND BEGIN
EXTRA-TROPICAL TRANSITION. THE SYSTEM WILL COMPLETE TRANSITION TO A
WARM SECLUSION TYPE EXTRA-TROPICAL SYSTEM NO LATER THAN TAU 96 IN
THE SEA OF JAPAN.
MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE TRACK GUIDANCE REMAINS
VERY CONSISTENT RUN TO RUN AND WITH VERY LITTLE SPREAD,
PARTICULARLY THROUGH TAU 48. CROSS-TRACK SPREAD REMAINS LOW THROUGH
TAU 96, BUT ALONG TRACK SPREAD INCREASES TO 600NM BETWEEN THE SLOW
NAVGEM AND FAST JGSM MODELS, WHICH IS NOT ALL THAT UNUSUAL IN AN
ETT SCENARIO. THE JTWC FORECAST REMAINS CONSISTENT WITH THE
PREVIOUS FORECAST WITH HIGH CONFIDENCE THROUGH TAU 72, AND MEDIUM
CONFIDENCE THEREAFTER. INTENSITY GUIDANCE IS SOMEWHAT MIXED, WITH
THE DECAY-SHIPS CONTINUING TO HAVE LITTLE FAITH IN HINNAMNORS
POTENTIAL, SHOWING NO FURTHER INTENSIFICATION THROUGH THE FORECAST
PERIOD. MEANWHILE, GFS, HWRF AND THE CONSENSUS PEAK THE SYSTEM AT
AROUND 90 KNOTS, WHILE THE COAMPS-TC, AND ENSEMBLE INTENSIFY THE
SYSTEM TO AROUND 115 KNOTS. ADDITIONALLY, THE RAPID INTENSIFICATION
PREDICTION AID (RIPA) HAS TRIGGERED ON THIS RUN, INDICATING A 40
PERCENT OR HIGHER PROBABILITY OF RI. THE JTWC FORECAST LIES ALONG A
SHALLOWER SLOPE THAN THE RIPA, BUT ABOVE THE BULK OF THE GUIDANCE.
HOWEVER, WITH SUCH A LARGE SPREAD IN THE GUIDANCE, THERE IS MEDIUM
TO LOW CONFIDENCE IN THE FORECAST.
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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