WDXS33 PGTW 160900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 14S (TALIAH) WARNING NR 
031//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 27.3S 81.0E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 1369 NM EAST-SOUTHEAST OF PORT LOUIS,
MAURITIUS
   MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 24 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
CYCLONE 14S (TALIAH) WITH AN EXPOSED LOW-LEVEL CIRCULATION CENTER
(LLCC) AND CONVECTION CONFINED TO THE SOUTHERN SEMICIRCLE. A
160335Z METOP-C ASCAT PARTIAL IMAGE REVEALS THAT THE WINDS WITHIN
THE WESTERN PERIPHERY HAVE WEAKENED OVER THE PAST 12 HOURS. 35 KNOT
WINDS ARE NOW DEPICTED WITHIN THE WESTERN AND SOUTHERN PERIPHERIES.
THE INITIAL INTENSITY OF 40 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON THE ASCAT IMAGE SHOWING 35 KTS, BUT NOT CATCHING A PORTION
OF THE SOUTHERN PERIPHERY, WHERE THE STRONGEST WINDS ARE NOW
THOUGHT TO BE. CIMSS OBJECTIVE INTENSITY ESTIMATES ARE TOO LOW ACROSS 
THE BOARD DUE TO THE LACK OF CONVECTIVE STRUCTURE. THE INITIAL 
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE EXPOSED NATURE OF 
THE LLCC IN ANIMATED MSI. ENVIRONMENTAL ANALYSIS INDICATES THAT 14S IS 
IN A MARGINAL ENVIRONMENT CHARACTERIZED BY STRONG POLEWARD OUTFLOW 
ALOFT, HIGH (30-35 KTS) VERTICAL WIND SHEAR, AND BORDERLINE (25-26 C) 
SEA SURFACE TEMPERATURES.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: COMBINED STEERING INFLUENCE OF RIDGING
TO THE EAST AND SOUTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   DEMS: T2.5 - 35 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 30-35 KTS
   SST: 25-26 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: EXTENSIVE DRY AIR OVER THE NORTHERN PORTION OF
THE SYSTEM

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 14S IS FORECAST TO CONTINUE TRACKING
SOUTHWESTWARD, IN RESPONSE TO THE COMBINED STEERING INFLUENCE OF
RIDGING TO THE EAST AND SOUTH THROUGH TAU 48. NEAR TAU 48, THE
STEERING PATTERN WILL WEAKEN, CAUSING THE TRACK SPEED OF 14S TO
SIGNIFICANTLY SLOW. RIDGING TO THE SOUTH WILL THEN BRIEFLY BUILD
BACK IN AROUND TAU 72, CAUSING THE SYSTEM TO BEGIN TRACKING
WESTWARD THROUGHOUT THE REMAINDER OF THE FORECAST PERIOD. REGARDING
INTENSITY, 14S IS FORECAST TO MAINTAIN INTENSITY THROUGH TAU 48
WITH GALE-FORCE WINDS LIKELY CONFINED TO THE SOUTHERN PERIPHERY.
STRONG POLEWARD OUTFLOW WILL FIGHT OFF THE HIGH SHEAR AND COOLING
SEA SURFACE TEMPERATURES. HOWEVER, BY TAU 72, SEA SURFACE
TEMPERATURES WILL DROP BELOW 23 C AND THE POLEWARD OUTFLOW CHANNEL
WILL WEAKEN, CAUSING THE SYSTEM TO DISSIPATE NEAR TAU 96. 

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT
REGARDING THE TRACK OF 14S THROUGH TAU 48 WITH A 32 NM CROSS-TRACK
SPREAD AT THAT TIME. AFTER TAU 48, MODELS BEGIN TO DIVERGE DUE TO
THE WEAKENED STEERING PATTERN. ECMWF AND ITS ENSEMBLE MEAN HAVE
VERY LITTLE WESTWARD MOVEMENT, MAKING UP THE EASTERNMOST MEMBERS.
GALWEM AND UKMET MAKE UP THE WESTERNMOST MEMBERS. THE JTWC TRACK
FORECAST IS PLACED SLIGHTLY TO THE EAST OF CONSENSUS WITH HIGH
CONFIDENCE THROUGH TAU 72 AND LOW CONFIDENCE THEREAFTER. INTENSITY
GUIDANCE IS IN OVERALL MODERATE AGREEMENT. HAFS-A HAS THE QUICKEST
WEAKENING TREND, SUGGESTING A DROP TO BELOW 35 KTS BY TAU 36. THE
REMAINDER OF GUIDANCE HAS A STEADY INTENSITY THROUGH TAU 48 AND
THEN WEAKENING THEREAFTER. THE JTWC INTENSITY FORECAST IS PLACED
CLOSER TO THE MAIN GROUPING OF GUIDANCE WITH MEDIUM CONFIDENCE.

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