WDIO31 PGTW 082100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 06B (MANDOUS) WARNING 
NR 005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 10.5N 82.2E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 193 NM SOUTH-SOUTHEAST OF CHENNAI, INDIA
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A MASS
OF CONVECTION DISPLACED TO THE SOUTHWEST QUADRANT FROM THE ASSESSED
LOW LEVEL CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS PLACED
WITH MEDIUM CONFIDENCE BASED ON THE PGTW AGENCY POSITION FIX, AN
EARLIER PARTIAL 081630Z METOP-B ASCAT PASS, ALONG WITH THE
AFOREMENTIONED EIR DATA. THE INITIAL INTENSITY OF 55 KTS IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON PGTW AND KNES DVORAK
ESTIMATES OF T3.5, AND SET SLIGHTLY HIGHER THAN DEMS T3.0.
ENVIRONMENTAL ANALYSIS INDICATES TC 06B IS IN A MARGINAL AREA FOR
FURTHER DEVELOPMENT WITH MODERATE UPPER-LEVEL OUTFLOW, AND WARM
(28-29 C) SEA SURFACE TEMPERATURES, OFFSET BY STRONG (20-25 KTS)
VERTICAL WIND SHEAR (VWS).

INITIAL WIND RADII BASIS: SCATTEROMETER DATA FROM 081630Z

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE NORTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   KNES: T3.5 - 55 KTS
   DEMS: T3.0 - 45 KTS
   CIMSS SATCON: 59 KTS AT 081412Z
   CIMSS ADT: 53 KTS AT 081815Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 20-25 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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 06B MANDOUS IS ON A DIRECT PATH
NORTHWESTWARD AND IS EXPECTED TO MAKE LANDFALL TO THE SOUTHWEST OF
CHENNAI ALONG THE COAST OF SOUTHEAST INDIA. THE SYSTEM HAS A
CURRENT INTENSITY OF 55 KNOTS AND IS EXPECTED TO SLIGHTLY WEAKEN
OVER THE NEXT 12 HOURS. AFTER TAU 12, THE COMBINATION OF STRONG
(20-25 KTS) VERTICAL WIND SHEAR (VWS), AS WELL AS LAND INTERACTION
WILL BEGIN A GRADUAL WEAKENING TREND. BY TAU 24 TC 04B IS EXPECTED
TO MAKE LANDFALL INTO SOUTHEAST INDIA AND WILL DECREASE IN
INTENSITY TO 40 KNOTS AND BEGIN DISSIPATION DUE TO INCREASED LAND
INTERACTION. BY TAU 36 THE SYSTEM WILL BE DISSIPATED WITH THE
INTENSITY FALLING TO 25 KNOTS.

MODEL DISCUSSION: THE NUMERICAL MODEL TRACK ENVELOPE IS RELATIVELY
TIGHT WITH A GRADUAL SPREAD TO 35 NM BY TAU 12, INCREASING TO 77 NM
AFTER LANDFALL BY TAU 24. DUE TO THIS TIGHT ENVELOPE THE CONFIDENCE
IN THE JTWC FORECAST TRACK IS HIGH. INTENSITY GUIDANCE IS IN
OVERALL GOOD AGREEMENT, WITH DECAY SHIPS REPRESENTING THE HIGH END
OF GUIDANCE WHILE THE HWRF AND COAMPS-TC SHOW A LESS AGGRESSIVE
INTENSITY SOLUTION. THIS COUPLED WITH THE DEGRADING ENVIRONMENT
OVER THE NEXT 24 HOURS LENDS MEDIUM CONFIDENCE IN THE JTWC
INTENSITY FORECAST WHICH IS SET SLIGHTLY HIGHER THAN CONSENSUS.

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