WDXS31 PGTW 200900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 26S (TWENTYSIX) WARNING 
NR 004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.2S 95.1E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 121 NM WEST-SOUTHWEST OF THE COCOS ISLANDS
   MOVEMENT PAST 6 HOURS: EAST-SOUTHEASTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS FRAGMENTED AND 
SHALLOW CONVECTIVE BANDING WRAPPING INTO AN EXPOSED LOW-LEVEL 
CIRCULATION CENTER (LLCC) OF THE TROPICAL CYCLONE (TC) 26S. RECENT 
CHANGE IN THE STEERING PATTERN AND STORM MOVEMENT LEFT THE LLCC FULLY 
EXPOSED AND TRACKING EAST-SOUTHEASTWARD, WHILE THE DEEP CONVECTION IS 
DISPLACED TO THE WEST, DUE TO STRONG (25-30 KTS) EASTERLY VERTICAL 
WIND SHEAR (VWS). THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE 
BASED ON THE LLCC PRESENT IN THE HIGH RESOLUTION VISIBLE IMAGERY LOOP, 
WHILE THE INITIAL INTENSITY OF 40 KTS IS ASSESSED WITH HIGH CONFIDENCE 
BASED ON A 200316Z METOP-B ASCAT PASS SHOWING A BAND OF 40 KT WINDS 
PRIMARILY TO THE NORTHWEST OF THE LLCC, AS WELL AS A 200538Z OCEANSAT-
3 PASS REVEALING 33-38 KT WINDS. ENVIRONMENTAL ANALYSIS REVEALS 
MARGINAL ENVIRONMENT CHARACTERIZED BY AFOREMENTIONED STRONG (25-30 
KTS) VWS, WEAK EQUATORWARD OUTFLOW, WARM (28-29 C) SEA SURFACE 
TEMPERATURES (SST), AS WELL AS SLIGHTLY INCREASING MOISTURE CONTENT 
ACROSS THE VERTICAL EXTENT.

INITIAL WIND RADII BASIS: 200316Z AND 200228Z ASCAT SCATTEROMETER
DATA 

CURRENT STEERING MECHANISM: NEAR EQUATORIAL RIDGE (NER) TO THE
NORTHEAST AND SOUTHEASTWARD LOW-LEVEL MONSOON FLOW

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   KNES: T2.5 - 35 KTS
   DEMS: T3.0 - 45 KTS
   CIMSS SATCON: 43 KTS AT 200600Z
   CIMSS ADT: 33 KTS AT 200530Z
   CIMSS AIDT: 33 KTS AT 200530Z
   CIMSS D-PRINT: 33 KTS AT 200530Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 25-30 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: WEAK EQUATORWARD
   OTHER FACTORS: STEERING PATTERN CHANGE FROM A SUBTROPICAL RIDGE
TO THE SOUTH, TO THE NEAR EQUATORIAL RIDGE TO THE NORTHEAST

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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: TC 26S IS FORECAST TO TRACK SOUTHEASTWARD
UNDER THE INFLUENCE OF THE LOW-LEVEL MONSOON FLOW. POTENTIALLY
DEVELOPING MID-LEVEL CONVECTION WILL ALSO BE STEERED IN THE SAME
DIRECTION BY THE NER TO THE NORTHEAST. GIVEN THE MARGINAL
ENVIRONMENT HOWEVER, ANY SIGNIFICANT DEVELOPMENT IS UNLIKELY AND
THE SYSTEM IS FORECAST TO MAINTAIN INTENSITY OF 35-40 KTS OVER THE
NEXT 96 HOURS, FOLLOWED BY A DISSIPATION BY THE END OF THE FORECAST
PERIOD. SIGNIFICANT UNCERTAINTY REMAINS IN PLACE IN REGARD TO THE
TRACK, AS PAST TAU 36, THE SYSTEM IS FORECAST TO MAKE A NORTHEASTWARD 
TURN, DRIVEN BY THE WEAKENING OF THE MONSOON SURGE, AS WELL AS THE NER 
TO THE NORTHEAST MOVING WESTWARD. AT THAT POINT, TC 26S WILL REMAIN IN 
A WEAK STEERING ENVIRONMENT, WITH THE POSSIBILITY OF ERRATIC MOTION. 
BY TAU 72 THE SYSTEM IS FORECAST TO MAKE ANOTHER TURN TOWARD 
SOUTHEAST, AS THE MONSOON SURGE STRENGTHENS AGAIN. AVAILABLE INTENSITY 
AIDS INDICATE DISSIPATION BEGINNING AT TAU 96 AND COMPLETING BY THE 
END OF THE FORECAST PERIOD. THERE IS HOWEVER POTENTIAL THAT TC 26S 
WILL INTERACT WITH ANOTHER SYSTEM DEVELOPING OFF THE NORTHWESTERN 
COAST OF AUSTRALIA AT THE BEGINNING OF NEXT WEEK.

MODEL DISCUSSION: DETERMINISTIC MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT THROUGH TAU 36, WITH THE EXCEPTION OF NAVGEM, WHICH
PREDICTS A MORE SOUTH-SOUTHEASTWARD TRACK, WITH WESTWARD TURN AT
TAU 36. ALL OTHER CONSENSUS MEMBERS INDICATE AN EAST-NORTHEASTWARD
TURN AT TAU 48, FOLLOWED BY A NORTH-NORTHEASTWARD TRACK DIRECTION.
THE UNCERTAINTY OF THE ACTUAL POSITION OF THE SYSTEM, ASSOCIATED
WITH A 160 NM CROSS-TRACK, INCREASES SIGNIFICANTLY AND
LEADS TO A MEDIUM CONFIDENCE IN THE SHORT TERM TRACK FORECAST AND LOW 
CONFIDENCE THROUGHOUT TAU 120. JTWC INTENSITY FORECAST IS PLACED CLOSE 
TO THE MULTI-MODEL CONSENSUS AND IS ASSESSED WITH MEDIUM CONFIDENCE, 
DUE TO SIGNIFICANT SPREAD ACROSS THE GUIDANCE. STATISTICAL-DYNAMICAL 
MODELS INDICATE SLOW AND STEADY INCREASE IN INTENSITY, WHILE GFS, HAFS 
AND COAMPS-TC INDICATE WEAKENING OVER THE NEXT 24-36 HOURS, FOLLOWED 
BY STABILIZATION PERIOD, WITH INTENSITY OSCILLATING AROUND THE WARNING 
THRESHOLD. 

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