WDXS33 PGTW 170900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 14S (TALIAH) WARNING NR 
033//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 29.4S 77.8E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 1246 NM EAST-SOUTHEAST OF PORT LOUIS,
MAURITIUS
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 04 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 PERSISTENT CONVECTION CONFINED TO THE SOUTHERN
SEMICIRCLE. ENVIRONMENTAL ANALYSIS INDICATES THAT 14S IS IN A
MARGINALLY UNFAVORABLE ENVIRONMENT CHARACTERIZED BY HIGH (25-30
KTS) VERTICAL WIND SHEAR, SIGNIFICANT DRY AIR ENTRAINMENT, AND COOL
SEA SURFACE TEMPERATURES (24-25 C) SLIGHTLY OFFSET BY STRONG
POLEWARD OUTFLOW. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON THE EXPOSED LLCC IN ANIMATED MSI. THE INITIAL
INTENSITY OF 40 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON A
COMBINATION OF THE 170401Z ASCAT-B AND 170016Z RCM-1 SAR IMAGES.
THE RCM-1 SAR IMAGE SHOWS 40-43 KTS WITHIN THE SOUTHWESTERN
PERIPHERY WHILE THE ASCAT IMAGE SHOWS A BROAD SWATH OF 30 KNOT
WINDS WITHIN THE SOUTHERN SEMICIRCLE. THE INITIAL INTENSITY IS
HEDGED SLIGHTLY HIGHER THAN THE ASCAT IMAGE DUE TO IT MISSING THE
WESTERN PORTION OF THE SYSTEM, WHERE THE SAR IMAGE HAD THE HIGHER
WINDS.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA AND SAR DATA

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A LOW-LEVEL
SUBTROPICAL RIDGE (STR) POSITIONED TO THE EAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   FMEE: T2.0 - 30 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 25-30 KTS
   SST: 24-25 CELSIUS
   OUTFLOW: STRONG POLEWARD
   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 14S IS FORECAST TO CONTINUE TRACKING
SOUTHWESTWARD, ALONG THE LOW-LEVEL TO THE EAST THROUGH TAU 36.
AFTER TAU 36, RIDGING IS EXPECTED TO BUILD IN TO THE SOUTH OF THE
SYSTEM, CAUSING IT TO TRACK WESTWARD THROUGHOUT THE REMAINDER OF
THE FORECAST PERIOD. REGARDING INTENSITY, 14S IS FORECAST TO
MAINTAIN INTENSITY THROUGH TAU 36 DUE TO THE ROBUST POLEWARD
OUTFLOW. GALE-FORCE WINDS WILL LIKELY BE CONFINED TO THE SOUTHERN
SEMICIRCLE OF THE VORTEX. NEAR TAU 48, FURTHER COOLING SEA SURFACE
TEMPERATURES (BELOW 23 C) ALONG WITH SIGNIFICANT DRY AIR AND HIGH
SHEAR WILL CAUSE THE SYSTEM TO DISSIPATE AROUND TAU 72.
ADDITIONALLY, THE POLEWARD OUTFLOW CHANNEL IS EXPECTED TO WEAKEN,
FURTHER SUPPORTING THE DISSIPATION TIMELINE.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT
THROUGH TAU 48 WITH A 58 NM CROSS-TRACK SPREAD AT TAU 48.
AFTERWARDS, ALONG TRACK SPREAD QUICKLY INCREASES DUE TO DIFFERENCES
IN HOW THE RIDGING TO THE SOUTH PICKS UP THE SYSTEM. OVERALL, THE
JTWC TRACK FORECAST IS PLACED WITH MEDIUM CONFIDENCE. INTENSITY
GUIDANCE IS IN CLOSE AGREEMENT, SUGGESTING A STEADY INTENSITY
THROUGH TAU 36 AND WEAKENING THEREAFTER. THE JTWC INTENSITY
FORECAST IS PLACED WITH HIGH CONFIDENCE AS A RESULT. 

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