WDPN31 PGTW 260900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 12W (KROSA) WARNING NR 
011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.9N 144.1E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 98 NM WEST OF PAGAN
   MOVEMENT PAST 6 HOURS: EAST-NORTHEASTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS SIGNIFICANT
SHEAR OVER TROPICAL STORM (TS) 12W AS DEEP CONVECTION IS SLIGHTLY
DISPLACED TO THE SOUTH OF THE LOW-LEVEL CIRCULATION CENTER (LLCC).
TROCHOIDAL MOTION IS EVIDENT ON THE ANIMATED LOOP AS THE SYSTEM HAS
TRACKED IRREGULARLY EAST-NORTHEASTWARD OVER THE LAST SIX HOURS.
EQUATORWARD AND EASTWARD UPPER-LEVEL DIVERGENCE IS EVIDENT ON
ANIMATED WATER VAPOR IMAGERY. THE INITIAL POSITION IS PLACED WITH
HIGH CONFIDENCE BASED ON THE DEEP CONVECTIVE BANDING AND DISLOCATED
CONVECTION EVIDENT ON 260611Z F-18 SSMIS 91GHZ AND 37GHZ IMAGES,
SIGNIFICANTLY ASSISTING WITH THE POSITIONING OF THE LLCC THROUGH
THE HEAVY CLOUDS. THE INITIAL INTENSITY OF 50 KTS IS ASSESSED WITH
LOW CONFIDENCE BASED ON THE AGENCY AND OBJECTIVE FIXES LISTED
BELOW.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: A SUBTROPICAL RIDGE TO THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T3.0 - 45 KTS
   KNES: T3.0 - 45 KTS
   CIMSS ADT: 35 KTS AT 260530Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 20-25 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: LOW
   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 12W WILL CONTINUE AN OVERALL NORTHWARD
TRACK UNDER THE STEERING INFLUENCE OF A SUBTROPICAL RIDGE TO THE
EAST THROUGH TAU 48. BETWEEN TAU 48-96, A SUBTROPICAL RIDGE
POSITIONED OVER JAPAN WILL COMPETE WITH THE EASTERN RIDGE, SLOWING
THE TRACK SPEED DOWN AND CAUSING IRREGULAR TRACK MOVEMENT. THE
EASTERN RIDGE WILL WEAKEN AFTER TAU 72, RESULTING IN A
NORTHEASTWARD TRACK FOR THE REMAINDER OF THE FORECAST PERIODS AS
THE NORTHWESTERN RIDGE BUILDS. THE SYSTEM WILL STRUGGLE TO
INTENSIFY IN THE EARLY-TERM FORECAST WHILE UNDER STRONG VERTICAL
WIND SHEAR UPWARDS OF 20KTS. HOWEVER, THE UNFAVORABLE SHEAR WILL BE
COUNTERED BY EXPANSIVE AND FAVORABLE UPPER-LEVEL DIVERGENCE
PREVENTING THE SYSTEM FROM WEAKENING. THE SHEAR IS EXPECTED TO
PERSIST FOR THE FIRST 24 HOURS BEFORE GRADUALLY DECREASING,
ALLOWING FOR A SLOW RATE OF INTENSIFICATION FROM 50 KTS AT TAU 25 TO
70 KTS AT TAU 120.

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE IS IN MODERATE
AGREEMENT THAT TD 11W WILL TRACK NORTHWARD FOR THE FIRST 48 HOURS
OF THE FORECAST. FOLLOWING, THE TRACK WILL BECOME IRREGULAR TO
VARYING DEGREES. NAVGEM COMPLETELY BIFURCATES EASTWARD AWAY FROM
THE BULK OF THE MULTI-MODEL CONSENSUS, AND THE VARYING TRACK
SOLUTIONS OF THE REST OF THE CONSENSUS MEMBERS LEND LOW CONFIDENCE
IN THE LATE TERM FORECAST. THE INTENSITY GUIDANCE IS IN GOOD
AGREEMENT THAT THE SYSTEM WILL STRUGGLE TO INTENSIFY BETWEEN TAU
12-48, WITH SLOW INTENSIFICATION FOR THE ENTIRETY OF THE FORECAST
PERIOD.

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