WDPN32 PGTW 070900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 19W (CHANTHU) WARNING NR 005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.1N 135.7E
   INITIAL INTENSITY: 65 KTS
   GEOGRAPHIC REFERENCE: 764 NM SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) INDICATES THAT TY
19W HAS CONTINUED TO QUICKLY CONSOLIDATE AND HAS STARTED TO RAPIDLY
INTENSIFY. ANIMATED VISIBLE IMAGERY SHOWS VORTICAL HOT TOWERS (VHT)
DEVELOPING AROUND THE CENTER OF THE SYSTEM AND ROTATING UPSHEAR,
INDICATIVE OF THE ONSET OF RAPID INTENSIFICATION (RI).
ADDITIONALLY, A 070350Z AMSR2 COLORIZED 37GHZ MICROWAVE IMAGE
SHOWED A VERY SMALL MICROWAVE EYE FEATURE SURROUNDED BY A CYAN
RING, PROVIDING ANOTHER INDICATOR OF NEAR-TERM RI. THE AMSR2
IMAGERY PROVIDED HIGH CONFIDENCE TO THE INITIAL POSITION. THE
INITIAL INTENSITY IS SET AT 65 KNOTS, IS WELL ABOVE THE MAJORITY OF
THE MULTI-AGENCY AND OBJECTIVE CURRENT INTENSITY ESTIMATES.
HOWEVER, GIVEN THE MULTIPLE INDICATORS OF THE ONSET OF RI, THE
ANTICIPATED NEAR-TERM DEVELOPMENT OF AN EYE, AND THE COMPACT NATURE
OF THE SYSTEM (LEADING TO POTENTIALLY LOW DVORAK ESTIMATES) PROVIDE
HIGH CONFIDENCE TO THE INITIAL INTENSITY. WHILE SMALL IN NATURE,
THE SYSTEM CONTINUES TO EXHIBIT RADIAL OUTFLOW, AND VERY LOW WIND
SHEAR VALUES. THE SYSTEM LIES OVER VERY WARM (30C) AND HIGH OHC
WATERS, PROVIDING AMPLE ENERGY TO SUPPORT THE RI.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: DEEP-LAYER SUBTROPICAL RIDGE (STR) TO
THE NORTH. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T3.0 - 45 KTS
   KNES: T4.0 - 65 KTS
   CIMSS ADT: 53 KTS AT 070540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 0-5 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE RADIAL
   OTHER FACTORS: HIGH OHC VALUES ABOVE 200 ALONG TRACK

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: TY 19W IS FORECAST TO CONTINUE TRACKING
WEST-NORTHWESTWARD THROUGH TAU 48 ALONG THE SOUTHERN PERIPHERY OF
THE DEEP STR CENTERED TO THE NORTH. GLOBAL MODEL FIELDS INDICATE
THAT BY AROUND TAU 48 THE RIDGE TO THE NORTH WILL BEGIN TO WEAKEN
SLIGHTLY, ERODED BY THE TRANSIT OF A MINOR SHORTWAVE TROUGH, WHILE
THE STR CENTER WILL MOVE EAST AND THE WESTERN PERIPHERY OF THIS
RIDGE WILL REORIENT TO A NORTH-SOUTH AXIS. THE NET RESULT FOR TY
19W WILL BE A GRADUAL TURN POLEWARD TOWARDS THE COAST OF SOUTHERN
TAIWAN. THE SYSTEM IS EXPECTED TO MAKE LANDFALL ALONG THE SOUTHERN
TIP OF TAIWAN NEAR TAU 96 THEN MOVE INTO THE SOUTHERN TAIWAN
STRAIT. TY 19W HAS EXHIBITED DRAMATIC IMPROVEMENTS IN ITS CONVECTIVE
STRUCTURE AND IS BEGINNING TO RAPIDLY INTENSIFY. THE RAPID
INTENSIFICATION PREDICTION AID (RIPA) HAS CONTINUED TO BE
TRIGGERED, PROVIDING INCREASING CONFIDENCE IN THE FORECAST
INTENSITIES THROUGH TAU 48. THE SYSTEM IS NOW FORECAST TO INTENSIFY
TO 95 KNOTS BY TAU 24 AND 115 KNOTS BY TAU 48 UNDER VERY FAVORABLE
ENVIRONMENTAL CONDITIONS OF WARM (30C) SSTS, LOW (5-10 KTS) VWS AND
RADIAL OUTFLOW. AS THE SYSTEM APPROACHES TAIWAN, IT IS EXPECTED TO
TAP INTO SOME POLEWARD OUTFLOW, BUT AT THE SAME TIME SSTS ARE
FORECAST TO COOL SLIGHTLY WHILE VWS IS FORECAST TO INCREASE. THESE
PARAMETERS SHOULD OFFSET ONE ANOTHER, RESULTING IN THE SYSTEM
MAINTAINING INTENSITY THROUGH LANDFALL, WITH SIGNIFICANT WEAKENING
THEREAFTER AS THE SYSTEM INTERACTS WITH THE RUGGED TERRAIN OF
TAIWAN. TROPICAL STORM CONSON (18W) IS LOCATED APPROXIMATELY 715NM
TO THE SOUTHWEST. THE TWO SYSTEMS ARE EXPECTED TO CLOSE TO WITHIN
570-590NM AROUND TAU 72 BUT THE PROBABILITY OF BINARY INTERACTION
REMAINS LOW DUE TO THE COMPACT NATURE OF BOTH SYSTEMS.  

MODEL DISCUSSION: CONFIDENCE IN THE SHORT-TERM FORECAST THROUGH TAU
48 IS HIGH, WITH A 100NM SPREAD OF CONSENSUS MEMBERS AT TAU 48. GFS
AND ITS ENSEMBLE ARE SHOWING A BIT MORE EQUATORWARD TRACK, BUT
OVERALL ALL MEMBERS ARE IN AGREEMENT ON THE TRACK THROUGH TAU 48.
THEREAFTER THINGS BEGIN TO DIVERGE SIGNIFICANTLY. AT TAU 96, THE
GFS, GFS ENSEMBLE, NAVGEM AND HWRF TURN SHARPLY POLEWARD ALONG THE
EAST COAST OF TAIWAN, WHILE THE UKMET, UKMET ENSEMBLE, ECMWF AND
ECMWF ENSEMBLE CONTINUE THEIR CONSISTENT TRACK TO THE SOUTH OF
TAIWAN, LEADING TO A 430NM SPREAD AT TAU 48. THE NAVGEM AND GFS
MODELS HAVE BEEN HIGHLY INCONSISTENT RUN TO RUN, THOUGH THE CURRENT
AND MOST RECENT RUNS HAVE BEEN CONSISTENT OVERALL ON THE SHARP TURN
POLEWARD EAST OF TAIWAN. THUS THERE IS LESS PRESSURE TO DISCOUNT
THEM ALTOGETHER, BUT NOT YET ENOUGH CONFIDENCE TO FULLY SHIFT THE
TRACK. HENCE THE JTWC FORECAST TRACK REMAINS CONSISTENT WITH THE
PREVIOUS FORECAST, AND REMAINS SOUTH OF THE CONSENSUS MEAN WITH
MEDIUM CONFIDENCE. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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