WDXS31 PGTW 192100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 26S (TWENTYSIX) WARNING 
NR 003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.0S 94.8E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 132 NM WEST-SOUTHWEST OF THE COCOS ISLANDS
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 02 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
CYCLONE 26S WITH A PARTIALLY EXPOSED LOW-LEVEL CIRCULATION CENTER
(LLCC) AND CONVECTION CONFINED TO THE WESTERN PERIPHERY. STRONG
EASTERLY VERTICAL WIND SHEAR (VWS) IS STILL OBSERVED, APPARENT BY
THE PRESSURE ON THE EASTWARD OUTFLOW OF THE SYSTEM. A 191429Z
METOP-B ASCAT IMAGE REVEALED A POORLY ORGANIZED CIRCULATION WITH
40-45 KTS WITHIN THE NORTHWESTERN QUADRANT. ENVIRONMENTAL ANALYSIS
INDICATES THAT 26S IS IN A MARGINAL ENVIRONMENT CHARACTERIZED BY
MODERATE EQUATORWARD OUTFLOW, HIGH (25-30 KTS) EASTERLY VWS, WARM
(28-29 C) SEA SURFACE TEMPERATURES, AND DRY AIR ENTRAINMENT TO THE
NORTH. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON
THE PARTIALLY EXPOSED LLCC IN ANIMATED EIR IMAGERY. THE INITIAL
INTENSITY OF 45 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON
PERSISTENCE FROM THE MENTIONED ASCAT IMAGE AND DVORAK ESTIMATES
RANGING FROM T2.5-3.0. OBJECTIVE INTENSITY ESTIMATES ARE ANALYZED
TO BE TOO LOW, RANGING FROM 30-35 KTS.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: COMPETING STEERING PATTERN BETWEEN A
NEAR-EQUATORIAL RIDGE (NER) TO THE NORTHEAST AND A SUBTROPICAL
RIDGE (STR) TO THE SOUTH. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   KNES: T2.5 - 35 KTS
   DEMS: T3.0 - 45 KTS
   APRF: T2.5 - 35 KTS
   CIMSS ADT: 35 KTS AT 191800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 25-30 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   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 BEGIN TRACKING
SOUTHEASTWARD, ALONG THE SOUTHWESTERN PERIPHERY OF THE NER. TRACK
SPEED HAS BEEN VERY SLOW (2 KTS) OVER THE PAST 6 HOURS, INDICATING
THAT THE TRACK MOTION MAY BE IN THE PROCESS OF CHANGING DIRECTION.
A SOUTHEASTWARD TRACK IS FORECAST TO PERSIST THROUGH TAU 48. AFTER
TAU 48, THE STEERING PATTERN BECOMES VERY WEAK WITH NO CLEAR
MECHANISM. AS A RESULT, THE SYSTEM IS FORECAST TO BE EXTREMELY SLOW
MOVING THROUGH THE REMAINDER OF THE FORECAST PERIOD. THE ACTUAL TRACK 
AFTER TAU 48 IS EXTREMELY UNCERTAIN, WITH ERRATIC MOTION POSSIBLE. 
REGARDING INTENSITY, 26S IS FORECAST TO BEGIN WEAKENING AFTER TAU 12 
DUE TO THE HIGH SHEAR AND DRY AIR SHALLOWING OUT THE VORTEX. BETWEEN 
TAUS 36 AND 96, 26S WILL LIKELY BE BORDERLINE TROPICAL STORM STRENGTH 
AS THE ENVIRONMENT REMAINS MARGINAL. NEAR TAU 120, THE SYSTEM IS 
FORECAST TO DROP BELOW 35 KTS, BUT IT COULD OCCUR SOONER IF THE VORTEX 
LOSES ALL CONVECTIVE ACTIVITY. 

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT
THROUGH TAU 48, WITH THE EXCEPTION OF NAVGEM, WHICH TRACKS THE
SYSTEM MORE SOUTHWARD VICE SOUTHEASTWARD. CROSS-TRACK SPREAD AT TAU
48, DISCOUNTING NAVGEM, IS AROUND 97NM. AFTER TAU 48, MODELS
QUICKLY DIVERGE DUE TO THE WEAK STEERING PATTERN. MOST MODELS DO
SHOW A SLOW NORTHWARD TURN AFTER TAU 48, BUT WITH LARGE VARIANCE.
THE JTWC TRACK FORECAST IS PLACED WITH MEDIUM CONFIDENCE THROUGH
TAU 72 AND LOW CONFIDENCE THEREAFTER. INTENSITY GUIDANCE IS IN
MODERATE AGREEMENT, WITH THE MAJORITY OF MODELS SHOWING WEAKENING
THROUGH TAU 48, AND THEN MAINTAINING INTENSITY THROUGH TAU 96. THE
MAIN OUTLIER IS COAMPS-TC, WHICH SHOWS STEADY INTENSIFICATION AFTER
TAU 60. STATISTICAL DYNAMICAL MODELS ALSO SHOW A STRONGER SYSTEM 
THROUGHOUT THE ENTIRE FORECAST PERIOD. THE JTWC INTENSITY FORECAST IS 
PLACED CLOSER TO THE MAIN GROUPING WITH OVERALL MEDIUM CONFIDENCE DUE 
TO THE EXPECTED MARGINAL ENVIRONMENT.

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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