WDPN31 PGTW 242100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 12W (KROSA) WARNING NR 
005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.2N 143.2E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 179 NM NORTH-NORTHWEST OF ANDERSEN AFB
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
STORM (TS) 12W (KROSA) WITH A FRAGMENTED BAND OF DEEP CONVECTION
SURROUNDING THE WESTERN PORTION OF THE LOW-LEVEL CIRCULATION CENTER
(LLCC). MULTIPLE VORTICES HAVE BEEN CIRCLING AROUND THE ASSESSED
LLCC WITH BUILDING CONVECTION CLOSER TO THE CENTER. A 241635Z GMI
89 GHZ MICROWAVE IMAGE REVEALED THE STRONGEST CONVECTION CONFINED
TO THE SOUTHERN SEMICIRCLE WITH DEFINED LOW-LEVEL CLOUDS WRAPPING
INTO THE LLCC. ENVIRONMENTAL ANALYSIS INDICATES THAT 12W IS IN A
MARGINALLY FAVORABLE ENVIRONMENT CHARACTERIZED BY MODERATE
EQUATORWARD OUTFLOW ALOFT, HIGH (30-35 KTS) NORTHERLY VERTICAL WIND
SHEAR, AND WARM (29-30 C) SEA SURFACE TEMPERATURES. THE INITIAL
POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE MENTIONED
GMI MICROWAVE IMAGE. THE INITIAL INTENSITY OF 35 KTS IS ASSESSED
WITH HIGH CONFIDENCE BASED ON THE AGENCY DVORAK AND OBJECTIVE
INTENSITY ESTIMATES LISTED BELOW. ADDITIONALLY, THE 2410149Z AND
241140Z ASCAT PASSES REVEALED A SWATH OF 30-35 KTS WITHIN THE
SOUTHERN SEMICIRCLE.

INITIAL WIND RADII BASIS: 2410149Z AND 241140Z ASCAT SCATTEROMETER
DATA 

CURRENT STEERING MECHANISM: WEAK RIDGING TO THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T1.5 - 25 KTS
   KNES: T1.5 - 25 KTS
   CIMSS SATCON: 40 KTS AT 241557Z
   CIMSS ADT: 34 KTS AT 241800Z
   CIMSS AIDT: 36 KTS AT 241800Z
   CIMSS DPRINT: 25 KTS AT 241800Z
   CIMSS DMINT: 26 KTS AT 241633Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 30-35 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 12W IS FORECAST TO TRACK
NORTH-NORTHEASTWARD, ALONG THE WESTERN PERIPHERY OF A BUILDING
SUBTROPICAL RIDGE TO THE EAST THROUGH TAU 96. AFTER TAU 96, A LARGE
BELT OF ENHANCED SOUTHWESTERLY FLOW IS EXPECTED TO BEGIN
INTERACTING WITH THE VORTEX, WHICH WILL SHOVE IT OFF TO THE
NORTHEAST THROUGH THE REMAINDER OF THE FORECAST PERIOD. REGARDING
INTENSITY, 12W IS FORECAST TO INTENSIFY OVER THE NEXT 48 HOURS AS
THE SYSTEM CONTINUES TO CONSOLIDATE. NORTHERLY VERTICAL WIND SHEAR
IS EXPECTED TO REMAIN NEAR 30 KTS, HOWEVER, INTERACTION WITH AN
UPPER-LEVEL SHORTWAVE TROUGH IS EXPECTED TO DRASTICALLY ENHANCE
EASTWARD OUTFLOW THROUGH TAU 72. CURRENTLY, A PEAK INTENSITY OF 65 
KTS IS FORECAST TO OCCUR AT TAU 48 AND PERSIST THROUGH TAU 72. NEAR 
TAU 72, AN UPPER-LEVEL CYCLONE IS EXPECTED TO BE PLACED OVER THE 
VORTEX, WHICH WILL CAUSE INCREASED DRY AIR ENTRAINMENT AND 
SIGNIFICANTLY DECREASED OUTFLOW. AS A RESULT, 12W IS FORECAST TO 
WEAKEN FROM TAU 72 TO 96 UNDER THE INFLUENCE OF THE UPPER-LEVEL 
CYCLONE. 

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT THROUGH TAU 72 WITH AROUND A 130 NM CROSS-TRACK SPREAD AT
TAU 72. AFTER TAU 72, MODELS BEGIN TO DIVERGE DUE TO DIFFERENCES IN
TIMING AND AMOUNT OF INTERACTION WITH THE BELT OF ENHANCED
SOUTHWESTERLIES. THE ECMWF HAS A SLOWER TURN TO THE NORTHEAST WHILE
GFS HAS A SHARPER AND QUICKER TURN. THE JTWC TRACK FORECAST IS
PLACED CLOSE TO THE MULTI-MODEL CONSENSUS THROUGH TAU 96 AND MORE
IN LINE WITH THE ECMWF DEPICTION AFTERWARD. INTENSITY GUIDANCE
AGREES ON INTENSIFICATION THROUGH TAU 48-60 TO A PEAK RANGING FROM
55-75 KTS AND THEN WEAKENING AFTER TAU 72. COAMPS-TC (GFS BASED) IS
THE MOST AGGRESSIVE MODEL WITH A PEAK INTENSITY OF 75 KTS AT TAU 60.
OVERALL, THE JTWC INTENSITY FORECAST IS PLACED IN LINE WITH THE
CONSENSUS WITH MEDIUM CONFIDENCE.

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