WDPN31 PGTW 011500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 09W (NINE) WARNING NR 
003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 9.8N 162.3E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 1027 NM EAST-SOUTHEAST OF TINIAN
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
STORM (TS) 09W QUICKLY CONSOLIDATING UNDER EXPANDING DEEP
CONVECTION. THE 011019Z METOP-B ASCAT PASS REVEALED THAT THE
SURFACE WINDS ARE STILL SLIGHTLY DISORGANIZED, WITH THE SMALL PATCH
OF GALE FORCE WINDS CONFINED TO THE SOUTHEAST QUADRANT.
ENVIRONMENTAL ANALYSIS INDICATES A HIGHLY FAVORABLE ENVIRONMENT,
CHARACTERIZED BY LOW (10-15 KTS) VERTICAL WIND SHEAR (VWS), WARM
(28-29 C) SEA SURFACE TEMPERATURES, AND ROBUST POLEWARD OUTFLOW.
THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON LOW
LEVEL CLOUD TRACING UNDER THE DEEP CONVECTION AND EXTRAPOLATION
FROM THE AFOREMENTIONED 011019Z ASCAT. THE INITIAL INTENSITY OF 35
KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE 011019Z ASCAT,
AND THE SUBJECTIVE AGENCY DVORAK FIXES AND CIMSS AUTOMATED
INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: INITIAL WIND RADII ARE BASED ON THE
011019Z METOP-C ASCAT DATA

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) CENTERED TO THE
NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   KNES: T3.0 - 45 KTS
   PHFO: T2.0 - 30 KTS
   CIMSS ADT: 35 KTS AT 011240Z
   CIMSS AIDT: 33 KTS AT 011240Z
   CIMSS D-PRINT: 32 KTS AT 011240Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: HIGH

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: RAPID INTENSIFICATION (RI) IS
FORECAST TO BEGIN AT TAU 24. THE PEAK INTENSITY FOR THIS FORECAST
PERIOD HAS BEEN INCREASED TO REFLECT THE ANTICIPATED EARLY RI.

FORECAST DISCUSSION: TS 09W WILL CONTINUE TRACKING GENERALLY
NORTHWESTWARD FOR THE NEXT 12-24 HOURS AS IT REMAINS STEERED BY THE
STR CENTERED TO ITS NORTHEAST. AROUND TAU 24, A SEPARATE STR
CENTERED TO THE NORTHWEST WILL BUILD AND EXTEND EASTWARD, GAINING
STEERING INFLUENCE OVER 09W IN THE PROCESS. AFTER 09W TRANSITIONS
STEERING RIDGES, IT WILL TRACK GENERALLY WEST-NORTHWESTWARD THROUGH
THE REMAINDER OF THE FORECAST PERIOD. BETWEEN TAU 48-60, THE
EASTWARD EXTENSION OF THE STEERING RIDGE IS EXPECTED TO WEAKEN,
CAUSING A SLIGHT SLOWDOWN IN 09W'S TRANSLATIONAL SPEED AND A SLIGHT
DIP IN 09W'S TRACK. THE RIDGE IS EXPECTED TO REORIENT SHORTLY
THEREAFTER AND KEEP 09W ON ITS WEST-NORTHWESTWARD TRAJECTORY
THROUGH TAU 120. REGARDING INTENSITY, 09W IS CURRENTLY FORECAST TO
STEADILY INTENSIFY UNTIL TAU 24 WHILE IT CONTINUES TO CONSOLIDATE.
THE SYSTEM IS EXPECTED TO RAPIDLY INTENSITY FROM TAU 24 UNTIL TAU
60. FOLLOWING TAU 60, 09W IS FORECAST TO CONTINUE INTENSIFYING AT A
SLIGHTLY SLOWER RATE UNTIL REMAINING STEADY BETWEEN TAU 96-120. IN
THE LATE-TERM FORECAST, 09W IS EXPECTED TO ENCOUNTER A DRY AIR MASS
TO THE WEST AND NORTH OF THE SYSTEM; HOWEVER, BY THIS TIME, 09W IS
EXPECTED TO BE A MATURE TYPHOON AND SHOULD BE ABLE TO COCOON ITSELF
OFF FROM THE SURROUNDING DRY AIR, AS INDICATED BY FORECAST MODELS.
ADDITIONALLY, FORECAST MODELS INDICATE 09W WILL HAVE AN EXPANSIVE
WIND FIELD, AND IS EXPECTED TO INTRODUCE DESTRUCTIVE WINDS ACROSS
CNMI AND GUAM AS IT PASSES SOUTH OF TINIAN.

MODEL DISCUSSION: DETERMINISTIC MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT THROUGH THE DURATION OF THE FORECAST, WITH THE EXCEPTION
OF GFS, WHICH DEPICTS A TRACK SIGNIFICANTLY FARTHER NORTH, AND
UKMET, WHICH DEPICTS A TRACK SOUTH OF ROTA. EXPERIMENTAL AI MODELS
ARE IN GOOD AGREEMENT WITH THE OTHER PHYSICS-BASED MEMBERS OF THE
JTWC CONSENSUS, WITH A TIGHT CLUSTERING OF RELIABLE MODELS PASSING 
BETWEEN ROTA AND TINIAN. THE JTWC TRACK FORECAST IS PLACED IN 
CONCURRENCE WITH THE BULK OF CONSENSUS MEMBERS AND EXPERIMENTAL AI 
MODELS WITH HIGH CONFIDENCE FROM TAU 0-72. THE CHIEF CONCERN IN THE 
LATE-TERM FORECAST IS THE LOCATION OF THE VORTEX CENTER AS 09W PASSES 
THROUGH THE ISLANDS. AS A RESULT, THE JTWC TRACK FORECAST IS PLACED 
WITH MEDIUM CONFIDENCE FROM TAU 72-120. RELIABLE INTENSITY AIDS ARE IN 
GOOD AGREEMENT IN A RAPID INTENSIFICATION TREND BETWEEN TAU 24-60. THE 
SPREAD IN PEAK INTENSITY CURRENTLY SITS AT A 25 KT SPREAD AT TAU 120 -
- WITH COAMPS-TC (GFS BOUNDARY CONDITIONS) AND GFS DETERMINISTIC ON 
THE LOWER SIDE AND HAFS-A ON THE HIGH SIDE. AS A RESULT, THE JTWC 
INTENSITY FORECAST IS ASSESSED WITH MEDIUM CONFIDENCE FROM TAU 0-72 
AND LOW CONFIDENCE FROM TAU 72-120, WITH UNCERTAINTY IN THE LATE-TERM 
FORECAST STEMMING FROM THE UNCERTAINTY SURROUNDING THE PEAK INTENSITY 
AS 09W UNDERGOES RI.

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