WDPN31 PGTW 010900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 09W (NINE) WARNING 
NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 9.2N 163.0E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 1086 NM EAST-SOUTHEAST OF ROTA
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
DEPRESSION (TD) 09W AS A QUICKLY CONSOLIDATING SYSTEM WITH LOWER
LEVEL CLOUD BANDS WRAPPING TIGHTLY UNDER A NEWLY DEVELOPING PLUME
OF DEEP CONVECTION THAT APPEARS TO BE THE BEGINNINGS OF A CENTRAL
DENSE OVERCAST. ENVIRONMENTAL ANALYSIS REVEALS A HIGHLY FAVORABLE
ENVIRONMENT, CHARACTERIZED BY LOW (0-5 KTS) VERTICAL WIND SHEAR,
WARM (28-29 C) SEA SURFACE TEMPERATURES, AND STRONG DIVERGENCE
ALOFT FROM A POINT SOURCE OVER THE SYSTEM. THE INITIAL POSITION IS
PLACED WITH MEDIUM CONFIDENCE BASED ON THE LOWER LEVEL CLOUD LINES
PRESENT IN ANIMATED MSI. THE INITIAL INTENSITY OF 30 KTS IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE CIMSS AUTOMATED
INTENSITY ESTIMATED AND AGENCY DVORAK FIXES LISTED BELOW.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   RJTD: T1.5 - 25 KTS
   KNES: T2.0 - 30 KTS
   PHFO: T1.5 - 25 KTS
   CIMSS ADT: 32 KTS AT 010700Z
   CIMSS AIDT: 31 KTS AT 010700Z
   CIMSS D-PRINT: 30 KTS AT 010700Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 0-5 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TD 09W WILL CONTINUE TRACKING GENERALLY
NORTHWESTWARD FOR THE NEXT 24 HOURS AS IT REMAINS STEERED BY THE
STR CENTERED TO ITS NORTHEAST. BETWEEN TAU 24-36, 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 EAST-NORTHEASTWARD THROUGH THE
REMAINDER OF THE FORECAST PERIOD. BETWEEN TAU 48-72, THE EASTWARD
EXTENSION OF THE STEERING RIDGE IS EXPECTED TO WEAKEN, CAUSING A
SLIGHT SLOWDOWN IN 09W'S TRANSLATIONAL SPEED. REGARDING INTENSITY,
09W IS CURRENTLY FORECAST TO STEADILY INTENSIFY UNTIL TAU 60. THE
SYSTEM IS EXPECTED TO BRIEFLY INTENSIFY AT A RAPID RATE FROM TAU
60-72 AS IT SLOWS IN THE HIGHLY FAVORABLE ENVIRONMENT. FROM TAU 72
ONWARD, 09W IS EXPECTED TO CONTINUE STEADY INTENSIFICATION. GIVEN
THE HIGHLY FAVORABLE ENVIRONMENT, RAPID INTENSIFICATION (RI) IS
POSSIBLE AS SOON AS TAU 24-48, WITH THE ONLY CURRENT INHIBITOR TO
RI BEING LACK OF ORGANIZATION. ONCE 09W CONSOLIDATES, THE
ENVIRONMENT WILL BE CONDUCIVE FOR UNRESTRICTED INTENSIFICATION.
SHOULD 09W BEGIN SIGNIFICANTLY INTENSIFYING SOONER THAN FORECAST, A
PEAK INTENSITY HIGHER THAN 120 KTS IS POSSIBLE. 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 NAVGEM AND GFS, WHICH DEPICT A TRACK SIGNIFICANTLY FARTHER
NORTH. 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 STRONG AGREEMENT IN
A STEADY INTENSIFICATION TREND THROUGH TAU 60. AFTER TAU 60,
MESOSCALE MODELS DEPICT A MORE SIGNIFICANT INTENSIFICATION TREND
THAN THE GFS DETERMINISTIC. THE SPREAD IN PEAK INTENSITY HAS
IMPROVED WITH EACH MODEL CYCLE, AND CURRENTLY SITS AT A 20 KT
SPREAD AT TAU 120 -- WITH GFS ON THE LOWER SIDE AND EXPERIMENTAL
GOOGLE DEEPMIND ON THE HIGH SIDE. AS A RESULT, THE JTWC INTENSITY
FORECAST IS ASSESSED WITH HIGH CONFIDENCE FROM TAU 0-72 AND MEDIUM
CONFIDENCE FROM TAU 72-120, WITH UNCERTAINTY IN THE LATE-TERM
FORECAST STEMMING FROM THE PREVIOUS DISCUSSION REGARDING RI.

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