WDPN31 PGTW 072100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 06W (MARIA) WARNING NR 
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 25.6N 142.9E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 605 NM SOUTH-SOUTHEAST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: EAST-NORTHEASTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
STORM 06W (MARIA) AS QUICKLY CONSOLIDATING OVER THE PAST 6 HOURS
WITH A RAGGED EYE BEGINNING TO FORM. A 071912Z SSMIS 91 GHZ
MICROWAVE IMAGE REVEALS THE EYE NEAR THE EASTERN EDGE OF THE SWATH.
THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE
MENTIONED SSMIS IMAGE. THE INITIAL INTENSITY OF 40 KTS IS ASSESSED
WITH MEDIUM CONFIDENCE BASED ON THE OBJECTIVE AND SUBJECTIVE DVORAK
ESTIMATES LISTED BELOW. ENVIRONMENTAL ANALYSIS INDICATES THAT 06W
IS IN A FAVORABLE ENVIRONMENT FOR FURTHER INTENSIFICATION
CHARACTERIZED BY STRONG POLEWARD AND EQUATORWARD OUTFLOW ALOFT, LOW
(5-10 KTS) VERTICAL WIND SHEAR, AND WARM (30-31 C) SEA SURFACE
TEMPERATURES.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A SUBTROPICAL
RIDGE (STR) TO THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   KNES: T3.0 - 45 KTS
   CIMSS SATCON: 38 KTS AT 1800Z
   CIMSS ADT: 35 KTS AT 1800Z
   CIMSS AIDT: 38 KTS AT 1800Z
   CIMSS DPRINT: 36 KTS AT 1800Z
   CIMSS DMINT: 43 KTS AT 1625Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: CONTINUATION OF RAPID INTENSIFICATION
(RI) AIDS TRIGGERING AND AN EYE BEGINNING TO FORM HAS SHIFTED THE
FORECAST TO MORE QUICKLY INTENSIFY THE SYSTEM AND WITH A HIGHER
PEAK INTENSITY. ADDITIONALLY, MODEL GUIDANCE HAS A STRONGER
PRESENCE OF A WESTWARD TURN, SO THE TRACK HAS HEDGED TOWARDS THAT
DIRECTION RATHER THAN A NORTHEASTWARD TRACK DEPICTED BY THE
PREVIOUS FORECASTS. THIS WILL BE DISCUSSED IN DETAIL IN THE MODEL
DISCUSSION SECTION.

FORECAST DISCUSSION: 06W IS FORECAST TO TRACK NORTH-NORTHEASTWARD
THROUGH TAU 24. AS THE RIDGE TO THE WEST REORIENTS, THE SYSTEM IS
FORECAST TO TRACK NORTHWARD THROUGH TAU 96. AFTER TAU 96, AN
EXTENSION OF THE RIDGE WILL EXTEND OVER NORTHERN HONSHU DRIVING THE
SYSTEM WESTWARD THROUGH THE REMAINDER OF THE FORECAST PERIOD.
REGARDING THE INTENSITY FORECAST, 06W IS NOW FORECAST TO BEGIN A
PHASE OF RAPID INTENSIFICATION, WITH A PEAK INTENSITY OF 75 KTS AT
TAU 36. THIS IS IN RESPONSE TO MANY OF THE RI AIDS TRIGGERING AS
WELL AS THE FAVORABLE ENVIRONMENT REMAINING IN PLACE THROUGH THAT
TIME. AFTER TAU 36, THE SYSTEM IS FORECAST TO BEGIN A WEAKENING
TREND AS IT ENTERS COOLER WATERS AND DRY AIR BEGINS TO ENTRAIN INTO
THE SYSTEM ALONG THE WESTERN SEMICIRCLE.

MODEL DISCUSSION: MODEL GUIDANCE IS DEPICTING A BIFURCATION
SCENARIO FOR 06W. THE GFS AND GFS ENSEMBLE MEAN HAVE THE SYSTEM
TURNING SHARPLY WESTWARD AROUND TAU 60 AS THE RIDGE BUILDS IN TO
THE NORTH. THIS WESTWARD TRACK HAS THE SYSTEM PASSING ABOUT 90 NM
SOUTH OF TOKYO BEFORE MAKING LANDFALL IN HONSHU. ECMWF HAS THE
SYSTEM TRACKING FASTER IN THE NEAR TERM AND IS THEREFORE NOT
TRAPPED BY THE RIDGE. IT INSTEAD CONTINUES TRACKING POLEWARD AND
MAKING A NORTHEASTWARD TURN TRACKING EAST OF HOKKAIDO. GALWEM AND
UKMET DETERMINISTIC MODELS HAVE STARTED TRACKING MORE WESTWARD OVER
THE PAST FEW MODELS RUNS, ADDING SOME SUPPORT TO THE QUICKER ONSET
OF THE RIDGE EXTENSION TO THE NORTH FORMING. THE JTWC FORECAST HAS
BEGUN HEDGING CLOSER TO THE WESTWARD GROUPING WITHOUT COMPLETELY
BITING OFF ON THE GFS DEPICTION IF THE MODELS BEGIN TO DEVIATE. THE
JTWC TRACK FORECAST IS THEREFORE PLACED WITH MEDIUM CONFIDENCE
THROUGH TAU 72, WITH LOW CONFIDENCE THEREAFTER. WITH THE CONTINUED
PRESENCE OF RI AIDS AND THE CONSOLIDATED APPEARANCE IN ANIMATED
SATELLITE IMAGERY, THE JTWC FORECAST TRACK HAS TAKEN ON A MORE
AGGRESSIVE INTENSIFICATION TREND. NON-RI AIDS DEPICT A MUCH LESS
INTENSE TREND WITH A PEAK INTENSITY OF 50-55 KTS AT TAU 36. AFTER
TAU 36, MOST MODEL GUIDANCE HAS A SLIGHT WEAKENING TREND WITH THE
EXCEPTION OF HAFS-A AND GFS. THIS IS DUE TO THE LARGE VARIATION IN
TRACKS WITH THOSE TWO MODELS FROM THE REMAINDER OF GUIDANCE. BOTH
MODELS HAVE THE SYSTEM MAKING THE SHARP WESTWARD TURN, AND IF THAT
PATH IS TAKEN, OUTFLOW COULD INCREASE, CAUSING A HIGHER PEAK LATER
IN THE FORECAST (TAU 96-120) AS IT TRACKS WESTWARD. 

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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