WDPN31 PGTW 012100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 09W (NINE) WARNING NR 
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 10.5N 161.4E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 987 NM EAST OF ANDERSEN AFB
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
STORM (TS) 09W STEADILY CONSOLIDATING, WITH A SMALL CENTRAL DENSE
OVERCAST (CDO) FEATURE DEVELOPING OVER THE PAST FEW HOURS. A
011745Z SSMIS PASS REVEALS A SLIGHT NORTHWESTWARD VERTICAL TILT WITH
HEIGHT, AND THE LOWER-LEVEL STRUCTURE IS BETTER ORGANIZED THAN THE
UPPER-LEVEL AT THIS POINT IN TIME. DEEP CONVECTION IS BEGINNING TO
ORGANIZE BUT REMAINS CONSTRAINED PRIMARILY TO THE NORTHWESTERN
FLANK OF THE LOW LEVEL CIRCULATION CENTER (LLCC). GFS MODEL-BASED
SOUNDINGS SUGGEST VERY LIGHT VWS, WHILE THE LATEST CIMSS ANALYSIS
SUPPORTS ABOUT 15 KNOTS FROM THE SOUTHEAST. EMPIRICAL OBSERVATIONS
SUGGEST A VALUE SPLIT BETWEEN BOTH MODELS, BUT BIASED CLOSER TO
THE CIMSS SOLUTION. THE NEAREST SOUNDING FROM PTPN AT 1200Z SHOWS
ABOUT 11 KNOTS OF SHEAR. ANIMATED WATER VAPOR IMAGERY SHOWS A TUTT
TO THE NORTHWEST, EXTENDING FROM NEAR GUAM TO THE NORTH OF TS 09W.
THE INITIAL POSITION IS ASSESSED WITH LOW CONFIDENCE, AS THE LATEST
SSMIS PASS WAS NOT RECEIVED IN TIME FOR THE ANALYSIS, BUT GENERALLY
SUPPORTS THE INITIAL POSITION. THE INITIAL INTENSITY IS ASSESSED
WITH LOW CONFIDENCE, DUE TO THE SIGNIFICANT DISCREPANCY BETWEEN THE 
AGENCY FIXES (RANGE FROM T1.5 TO T3.5) AND THE GENERALLY WEAKER 
OBJECTIVE ESTIMATES. THE INITIAL INTENSITY IS CONSTRAINED TO THE 
AVERAGE OF ALL AVAILABLE ESTIMATES. THE ENVIRONMENT IS HIGHLY 
FAVORABLE FOR RAPID INTENSIFICATION (RI), WITH LOW DEEP-LAYER VWS, 
WARM SSTS, HIGH OHC, AND STRONG POLEWARD OUTFLOW INTO THE EASTERN 
FLANK OF THE AFOREMENTIONED TUTT.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SOUTHWESTERN FLANK OF AN EXTENSION OF A
DEEP LAYER SUBTROPICAL RIDGE (STR) POSITIONED TO THE EAST OF THE
SYSTEM. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T1.5 - 25 KTS
   KNES: T3.5 - 55 KTS
   PHFO: T2.5 - 35 KTS
   CIMSS SATCON: 34 KTS AT 011600Z
   CIMSS ADT: 43 KTS AT 011800Z
   CIMSS AIDT: 37 KTS AT 011800Z
   CIMSS D-MINT: 32 KTS AT 011500Z
   CIMSS D-PRINT: 36 KTS AT 011830Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 0-5 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: HIGH OCEAN HEAT CONTENT (OHC) EXCEEDING 100 KJ
PER CM3. 

ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   INITIAL INTENSITY: LOW
   INITIAL WIND RADII: LOW

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TS 09W IS CURRENTLY TRACKING NORTHWESTWARD
ALONG THE WESTERN FLANK OF AN EXTENSION OF THE STR POSITIONED TO
THE EAST. OVER THE NEXT 24 TO 36 HOURS, THE PRIMARY STR WHICH LIES
TO THE NORTH, EXTENDING FROM OKINAWA EASTWARD TO THE DATELINE, WILL
BUILD EASTWARD WHILE THE CURRENT EXTENSION OF THE RIDGE MOVES AWAY
TO THE SOUTHEAST AND WEAKENS. THE COMBINED EFFECT OF THESE CHANGES
WILL BE TO TURN TS 09W ONTO A MORE WESTWARD COURSE AFTER TAU 24.
BEGINNING AROUND TAU 48, AN UPPER-LEVEL TROUGH WILL PASS BY FAR TO
THE NORTH, AND PRECIPITATE A WEAKNESS IN THE STR. WHILE THE WEAKNESS 
IN THE RIDGE WILL NOT BE ENOUGH TO ENTICE TS 09W NORTHWARD, IT WILL 
WEAKEN THE STEERING GRADIENT RESULTING IN A SLOW DOWN IN FORWARD 
TRACK SPEED FROM TAU 48 TO TAU 72. THE SYSTEM WILL ONCE AGAIN 
INCREASE SPEED AFTER TAU 72, AS THE PRIMARY STEERING INFLUENCE SHIFTS 
TO A STRONG RIDGE CENTERED OVER THE RYUKYU ISLANDS WHICH WILL 
STEADILY BUILD EASTWARD. THE SYSTEM IS FORECAST TO PASS THROUGH THE 
NORTHERN MARIANA ISLANDS AROUND TAU 96. IN TERMS OF INTENSITY, THE 
ENVIRONMENT IS OPTIMAL FOR RAPID INTENSIFICATION (RI); THE PRIMARY 
LIMITING FACTOR FOR NOW IS THE SLIGHT VORTEX TILT. ALL AVAILABLE 
GUIDANCE SUPPORTS THE SYSTEM ACHIEVING AXISYMMETRIZATION IN THE NEAR 
TERM, SETTING THE STAGE FOR THE ONSET OF RI WITHIN THE NEXT 24 HOURS. 
THE FORECAST CALLS FOR THE SYSTEM TO REACH A PEAK INTENSITY OF AT 
LEAST 135 KNOTS AS IT PASSES THE NORTHERN MARIANAS, WITH SOME 
MESOSCALE GUIDANCE SUGGESTING THE PEAK INTENSITY COULD BE 
SIGNIFICANTLY HIGHER, WITH CENTRAL PRESSURES AS LOW AS 889MB. WITH 
SUCH INTENSE STORMS, THERE IS A HIGH LIKELIHOOD OF EYEWALL 
REPLACEMENT CYCLES (EWRC) WHICH WILL HAVE A SIGNIFICANT IMPACT ON THE 
MAGNITUDE AND TIMING OF THE PEAK INTENSITY, BUT THESE CYCLES REMAIN 
CRITICALLY UNPREDICTABLE AT PRESENT. HOWEVER, NUMERICAL MODELS HIGHLY 
CORROBORATE THAT A SIGNIFICANT SUPER TYPHOON WILL IMPACT THE NORTHERN 
MARIANA ISLANDS WITHIN APPROXIMATELY THE NEXT 96 HOURS. 

MODEL DISCUSSION: TRACK GUIDANCE IS IN OVERALL GOOD AGREEMENT
THROUGH THE FORECAST PERIOD. CROSS-TRACK SPREAD IN THE CONSENSUS
PACKAGE GRADUALLY INCREASES TO 120NM BY TAU 72, AND 220NM BY TAU
120. NAVGEM IS A SIGNIFICANT NORTHERN OUTLIER, WHILE THE UKMET
ENSEMBLE MEAN IS THE SOUTHERN OUTLIER. THE REMAINDER OF THE
GUIDANCE IS CONFINED TO A TIGHTER ENVELOPE, JUST 105NM WIDE AT TAU
120. MOST OF THE DETERMINISTIC GUIDANCE, WITH THE EXCEPTION OF
ECMWF, TRACKS THE SYSTEM NORTH OF SAIPAN, WHILE ALL OF THE
AVAILABLE AI EXPERIMENTAL GUIDANCE TRACKS THE SYSTEM SOUTH OF
TINIAN. THE ECMWF HAS SHIFTED SOUTHWARD WITH THIS RUN AND IS
ALIGNED WITH THE AI GUIDANCE. THE JTWC FORECAST TRACK IS PLACED ON
THE NORTHERN EDGE OF THE CLUSTER OF AI GUIDANCE, VERY CLOSE TO THE
ECMWF DETERMINISTIC TRACK FOR THE DURATION OF THE FORECAST PERIOD,
WITH HIGH CONFIDENCE. INTENSITY GUIDANCE IS ALSO IN STRONG
AGREEMENT, THOUGH UNCERTAINTY IN THE PEAK INTENSITY IS FAIRLY
LARGE, WITH SHIPS-GFS ON THE LOW END AT 95 KNOTS, AND HAFS-A ON THE
HIGH END, EXCEEDING 160 KNOTS. NEARLY EVERY RI PREDICTION AID HAS
TRIPPED, AND THE AI-RI 65KT IN 72HR PROBABILITY EXCEEDS 60 PERCENT.
THE JTWC FORECAST IS ALIGNED WITH THE EXPLICIT RI GUIDANCE THROUGH
TAU 48, THEN GENERALLY TRACKS THE EXPERIMENTAL GDM FNV3 GUIDANCE
THROUGH THE END OF THE FORECAST. CONFIDENCE IN THE INTENSITY
FORECAST IS MEDIUM, DUE TO THE UNCERTAINTIES OF ONSET OF EWRC. 

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   TRACK 72-120 HR: HIGH
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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