WDXS31 PGTW 080900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 12S (JENNA) WARNING NR 
008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.2S 90.3E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 525 NM SOUTHWEST OF THE COCOS ISLANDS
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 23 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL CYCLONE (TC) 12S (JENNA) CONTINUES TO TRACK WEST
NORTHWESTWARD AS A DECAYING VORTEX WITH NO CENTRAL DEEP CONVECTIVE
ACTIVITY PRESENT FOR THE PAST SIX HOURS AS DEPICTED BY ANIMATED
MULTISPECTRAL SATELLITE IMAGERY (MSI). THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON AGENCY FIXES ON THE VISIBLE,
WEAK LLCC. THE INITIAL INTENSITY OF 45 KTS IS ASSESSED WITH HIGH
CONFIDENCE BASED ON A 080248Z ASCAT PASS INDICATING STRONGER WINDS
IN THE SOUTHWESTERN QUADRANT OF THE CIRCULATION.

INITIAL WIND RADII BASIS: A 080248Z METOP-C ASCAT

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE SOUTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   DEMS: T2.5 - 35 KTS
   APRF: T1.5 - 25 KTS
   CIMSS SATCON: 38 KTS AT 0715Z
   CIMSS ADT: 25 KTS AT 080645Z
   CIMSS AIDT: 30 KTS AT 080645Z
   CIMSS D-MINT: 25 KTS AT 080730Z
   CIMSS D-PRINT: 30 KTS AT 080645Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 15-20 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: WEAK POLEWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL CYCLONE 12S (JENNA) WILL CONTINUE TO
TRACK WEST-NORTHWESTWARD UNDER THE INFLUENCE OF A SUBTROPICAL RIDGE
TO THE SOUTH WHILE BEING WEAKENED BY WESTERLY SHEAR. A CONTINUED
WEAKENING TREND WILL BE FACILITATED BY PROLONGED EXPOSURE TO DRY
AIR. WHILE GALES COULD LINGER FOR AS LONG AS 36 HOURS DUE TO
ENHANCED GRADIENT FLOW IN THE SOUTHERN SEMICIRCLE OF THE STORM, THE
JTWC FORECAST DEPICTS DISSIPATION OF THE SYSTEM OVER WATER BY TAU
48.

MODEL DISCUSSION: CROSS TRACK GUIDANCE AMONGST THE MULTI MODEL
CONSENSUS IS UNDER 100 NM THROUGHOUT THE FORECASTED PERIOD WITH A
FAIRLY EVEN SPLIT BETWEEN MEMBERS FORECASTING A MORE NORTHERN TRACK
AND THOSE DEPICTING A SOUTHERN TRACK. THE JTWC TRACK FORECAST IS
PLACED CLOSE TO THE MULTI-MODEL CONSENSUS WITH HIGH CONFIDENCE.
INTENSITY GUIDANCE HAS A MAXIMUM SPREAD OF 15 KTS DISREGARDING THE
SLIGHT INTENSIFICATION DEPICTED BY HAFS. THE JTWC INTENSITY
FORECAST REFLECTS VALUES CLOSE TO THE MULTI-MODEL CONSENSUS WITH
HIGH CONFIDENCE.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   INTENSITY 00-72 HR: HIGH//
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