Tropical Storm IN-FA Advisory za, 17-07

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 09W (NINE) WARNING
NR 004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 20.5N 133.5E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 477 NM SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS CONTINUING
CONSOLIDATION AROUND THE LOW LEVEL CIRCULATION CENTER (LLCC). DEEP
CONVECTION IS CONCENTRATED OVER THE EASTERN SEMICIRCLE AND TOTAL
PRECIPITABLE WATER LOOPS VERIFY THE EXISTANCE OF MUCH DRIER AIR
OVER THE NORTHWESTERN SEMICIRCLE. THE DRIER AIR AND INCREASING
UPPER LEVEL CONVERGENCE ASSOCIATED WITH THE UPPER LEVEL TROUGH IS
SLOWING THE DEVELOPMENT OF THE SYSTEM AND CREATING A MORE SUBSIDENT
ENVIRONMENT UPSTREAM ALONG TRACK. PRESSURE FALLS DURING THE
PAST 12 HOURS IN THE CORE OF THE SYSTEM AND DECREASING RADII OF THE
OUTERMOST CLOSED ISOBAR VERIFY STEADY DEEPENING AND CONSOLIDATION OF
THE SYSTEM. THE INITIAL POSITION IS FIXED WITH MODERATE CONFIDENCE
BASED ON THE PGTW FIX ON A PARTIALLY EXPOSED LLCC IN ANIMATED
MULTISPECTRAL IMAGERY. THE INITIAL INTENSITY ASSESSMENT IS BASED ON
A 162335Z PARTIAL ASCAT PASS, PRESSURE TRENDS, AND A BLEND BETWEEN
THE PGTW AND ADT DVORAK ASSESSMENTS.
INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).
CURRENT STEERING MECHANISM: TD 09W IS STEERING IN A COMPLEX MONSOON
GYRE PATTERN. CURRENTLY IT IS BEING NUDGED NORTHWESTWARD BY THE
WESTERN PERIPHERY OF THE NEAR EQUATORIAL RIDGE, BUT, AS IT TRACKS
FURTHER POLEWARD, THE SUBTROPICAL RIDGE WILL FORCE IT ON A MORE
WESTWARD TRACK. THE HAND-OFF BETWEEN STEERING FORCES WILL OCCUR
BETWEEN THE 24TH AND 26TH LATITUDES.
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T1.0 - 25 KTS
   RJTD: T1.5 - 25 KTS
   KNES: T2.5 - 35 KTS
   CIMSS ADT: 37 KTS AT 162340Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD
   OTHER FACTORS: AFTER TAU 24, OCEAN HEAT CONTENT ALONG TRACK
WILL DROP SHARPLY, IMPEDING PRONOUNCED INTENSIFICATION OF THE
SYSTEM.
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: TROPICAL DEPRESSION 09W WILL CONTINUE GRADUAL
CONSOLIDATION AND INTENSIFICATION AS IT TRACKS SLOWLY TO THE
NORTHWEST IN A MARGINALLY FAVORABLE ENVIRONMENT UNDER WEAK STEERING
FLOW. OVER THE NEXT 24 HOURS IT WILL TRACK AWAY FROM THE INFLUENCE
OF THE NEAR EQUATORIAL RIDGE AND GRADUALLY COME UNDER THE INFLUENCE
OF THE SUBTROPICAL RIDGE, BENDING TO A MORE WESTERLY TRACK. THE
SYSTEM WILL INTENSIFY STEADILY, REACHING A PEAK INTENSITY WHILE
TRACKING SOUTH OF OKINAWA. COOLER WATERS AND INCREASING SUBSIDENCE
ALOFT WILL IMPEDE SHARP INTENSIFICATION.
MODEL DISCUSSION: ALTHOUGH GUIDANCE HAS TIGHTENED CONSIDERABLY
DURING THE PAST 24 HOURS, THERE REMAINS CONSIDERABLE SPREAD IN
MODEL GUIDANCE DURING THE TAU 96-120 HOUR PERIOD. A SIGNIFICANT
PORTION OF ENSEMBLE MEMBERS ARE STILL TAKING A POLEWARD TRACK TOWARDS
AN UPPER LEVEL LOW SETTLING SOUTH OF KYUSHU, BUT ENSEMBLE MEANS HAVE
CONSOLIDATED TOWARDS A TRACK CLOSE TO AND SOUTH OF OKINAWA. THE
COMPLEX UPPER AIR PATTERN STEMMING FROM THE MONSOON GYRE WILL ACT
TO INCREASE UNCERTAINTY AND MODEL SPREAD THROUGHOUT THE FORECAST,
ESPECIALLY IN THE LATER TAUS. THE INTENSITY GUIDANCE IS BACKING DOWN
SLIGHTLY WITH EACH CONSECUTIVE MODEL RUN AND ANIMATED WATER VAPOR
IMAGERY SUPPORTS THEIR ASSESSMENT OF AN INCREASINGLY UNFAVORABLE
ENVIRONMENT UPSTREAM, BUT ALL GUIDANCE IS FIRM IN SHOWING A VIGOROUS
TYPHOON STRENGTH SYSTEM AS IT APPROACHES THE RYUKUS. THE JTWC
INTENSITY FORECAST STAYS IN THE CENTER OF THE ENSEMBLE MEAN
THROUGHOUT THE FORECAST. STATISTICAL DYNAMICAL MODELS REMAIN BELOW
THE MEAN AFTER TAU 72, AND NO GUIDANCE INDICATES AN INTENSITY OVER
90KTS.
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: LOW
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: LOW
   INTENSITY 72-120 HR: LOW//
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