WDPN31 PGTW 081500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 06W (MARIA) WARNING NR 
007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 28.8N 145.4E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 486 NM SOUTHEAST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 28 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
STORM 06W (MARIA), AS A WELL ORGANIZED AND SYMMETRICAL SYSTEM, WITH
A LOW LEVEL CIRCULATION CENTER (LLCC) WHICH IS FULLY OBSCURED BY A
CENTRAL DENSE OVERCAST (CDO). SPIRAL BANDS OF DEEP CONVECTION ARE
PRESENT IN ALL BUT ONE QUADRANT - THE NORTH WESTERLY SECTOR IS FREE
OF CONVECTION, WHICH CORRESPONDS TO ELONGATED DRY AIR IN THE
700-300MB LAYER. THE SYSTEM HAS BEEN TRACKING NORTH-NORTHEAST, WITH
THE PRIMARY STEERING INFLUENCE FROM A SUBTROPICAL RIDGE (STR) TO
THE EAST OF TS MARIA. THE INITIAL POSITION IS PLACED WITH MEDIUM
CONFIDENCE BASED ON ANIMATED INFRARED IMAGERY, AS WELL AS AN
EXTRAPOLATION OF THE NORMALIZED RADAR CROSS SECTION (NRCS) FROM A
080827Z SYNTHETIC APERTURE RADAR (SAR) PASS. THE INITIAL INTENSITY
OF 60 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE
AFOREMENTIONED SAR PASS, AS WELL AS AGENCY DVORAK AND AUTOMATED
FIXES. SUBSEQUENT REANALYSIS OF THE PGTW AND KNES FIXES TO T4.0
PROVIDE A HINT THAT THE INITIAL INTENSITY MAY IN FACT BE HIGHER
THAN 60 KNOTS.

INITIAL WIND RADII BASIS: SAR DATA 

CURRENT STEERING MECHANISM: WESTERN SIDE OF A DEEP-LAYER
SUBTROPICAL RIDGE TO THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T3.0 - 45 KTS
   KNES: T3.5 - 55 KTS
   CIMSS SATCON: 52 KTS AT 081000Z
   CIMSS ADT: 53 KTS AT 081300Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: HIGH
   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 06W (MARIA) IS CURRENTLY FORECASTED TO
CONTINUE TRACKING NORTH-NORTHEAST UNTIL TAU 24, FOLLOWED BY A
SLIGHT NORTH-WESTERLY TURN, DRIVEN BY A DEVELOPMENT OF AN EXTENDED
UPPER LEVEL RIDGE TO THE NORTH OF THE SYSTEM. AT TAU 72 TS MARIA IS
EXPECTED TO BEGIN FURTHER TURNING WEST, ON A HEADING GENERALLY
TOWARDS MISAWA, AS A DEVELOPING DEEP-LAYER RIDGE DEVELOPS OVER THE
SEA OF JAPAN AND BUILDS EASTWARD TO THE NORTH OF THE SYSTEM. THE
CURRENT FORECAST CALLS FOR LANDFALL SOUTHEAST OF MISAWA SHORTLY
AFTER TAU 96, WITH THE SYSTEM CROSSING TO THE WEST COAST OF
NORTHERN HONSHU BY TAU 120. TROPICAL CYCLONE DEVELOPMENT CONDITIONS
WILL REMAIN FAVORABLE FOR THE NEXT 36 TO 48 HOURS, WITH LOW WIND
SHEAR, GOOD POLEWARD AND EQUATORWARD OUTFLOW, HIGH OCEAN HEAT
CONTENT (OHC), WARM SSTS. DURING THE BRIEF WINDOW UP TO TAU 48,
STEADY INTENSIFICATION IS EXPECTED, TO A PEAK OF AT LEAST 80 KNOTS.
DEPENDING ON HOW QUICKLY THE VORTEX CAN CONSOLIDATE AND THE TRACK
SPEED, A PERIOD OF RAPID INTENSIFICATION (RI) REMAINS POSSIBLE.
AFTER TAU 48, INCREASING SHEAR, DECREASING SSTS AND A RAPID
REDUCTION OF UPPER-LEVEL OUTFLOW WILL MARK THE BEGINNING OF A
GENERAL WEAKENING TREND. AFTER LANDFALL, MOVEMENT ACROSS THE RUGGED
TERRAIN OF NORTHERN HONSHU WILL INDUCE MORE RAPID WEAKENING, WITH
THE SYSTEM FORECAST TO BE A WEAK TROPICAL DEPRESSION BY TAU 120. 

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS STILL IN POOR
AGREEMENT IN REGARDS TO TRACK FORECAST, WITH THE TAU 120 TRACK
SPREAD OF 930 NM, AFTER DISCARDING THE NAVGEM AND UKMET
DETERMINISTIC FORECASTS, AS WIDELY UNREALISTIC. GFS REMAINS THE
SOUTHERN OUTLIER, TAKING THE SYSTEM WEST AFTER TAU 60, MAKING
LANDFALL TO THE SOUTH OF SENDAI, WHILE THE GALWEM AND UKMET
ENSEMBLE MARK THE OPPOSITE OUTLIERS, TAKING THE SYSTEM TO THE KURIL
ISLANDS BY TAU 120. THE MAIN FACTOR DRIVING THE TRACK DETERMINATION
IS STILL THE UNCERTAINTY OF THE TIMING OF INTERACTION BETWEEN THE
MID-LATITUDE TROUGH NORTH OF HOKKAIDO AND THE BUILDING OF AN
EXTENDED SUBTROPICAL RIDGE, WITH MAJORITY OF THE MODELS LEANING
TOWARDS THE LATTER BEING THE MAIN STEERING MECHANISM, ALLOWING THE
TS 06W TO TAKE A WESTERLY TRACK VERSUS THE RECURVE MOTION TOWARDS
THE NORTH-EAST. SINCE THE LAST FORECAST, THE ECMWF TRACKER HAS
SHIFTED SOUTHWARD AND IS NOW APPROACHING THE GFS TRACKER, LENDING
INCREASING CONFIDENCE TO THE OVERALL TRACK SCENARIO. SHORT-TERM
TRACK SPREAD (THROUGH TAU 72) IS CURRENTLY 280 NM, MAKING THE TRACK
FORECAST MORE RELIABLE DURING THIS TIMEFRAME. INTENSITY GUIDANCE
REMAINS MIXED, WITH THE MESOSCALE MODELS SHOWING AN OVERALL FLAT
INTENSITY TREND TO TAU 60 FOLLOWED BY RAPID WEAKENING, WHILE ON THE
OPPOSITE SIDE, THE RAPID INTENSIFICATION (RI) AIDS (RIPA, RICN,
RI25 TO RI45) CONTINUE TO BE TRIPPED. THE SHIPS GUIDANCE ALONG WITH
THE CONSENSUS MEAN LIE IN THE MIDDLE BETWEEN THE EXTREMES. THE JTWC
FORECAST LIES ABOUT 5 KNOTS ABOVE THE MEAN. 


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