WDXS31 PGTW 302100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 01S (ONE) 
WARNING NR 005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.0S 92.4E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 1244 NM EAST-SOUTHEAST OF DIEGO GARCIA
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 13 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
PARTIALLY-EXPOSED LOW-LEVEL CIRCULATION (LLC) POSITIONED ALONG THE
NORTHERN EDGE OF A LARGE, SYMMETRIC AREA OF DEEP CONVECTION. A
301449Z AMSU-B 89GHZ MICROWAVE IMAGE SHOWS A DISORGANIZED CLUSTER
OF DEEP CONVECTION SHEARED OVER THE SOUTHERN SEMICIRCLE OF THE LLC
WITH WEAK LOW-LEVEL STRUCTURE OVER THE NORTHERN SEMICIRCLE. A
301544Z ASCAT-C BULLSEYE IMAGE, WHICH WAS USED TO SET THE 34-KNOT
WIND RADII, REVEALS A SWATH OF 34-37 KNOT GALE-FORCE WINDS OVER THE
WEST AND SOUTHWEST QUADRANTS WITH LESS THAN 30 KNOT WINDS
ELSEWHERE. THE INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH HIGH
CONFIDENCE BASED ON THE ASCAT DATA PRIMARILY. THE INITIAL POSITION
IS PLACED WITH MEDIUM CONFIDENCE BASED ON EXTRAPOLATION FROM THE
ASCAT-C IMAGE. ENVIRONMENTAL CONDITIONS ARE UNFAVORABLE WITH
MODERATE TO HIGH (20-30 KNOTS) NORTHERLY VERTICAL WIND SHEAR,
OFFSET BY MODERATE POLEWARD OUTFLOW, MARGINALLY-FAVORABLE SST
VALUES (26C) AND DRY AIR ENTRAINMENT.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA

CURRENT STEERING MECHANISM: THE SYSTEM IS LOCATED WITHIN A WEAK
STEERING ENVIRONMENT NORTH OF A BREAK IN THE SUBTROPICAL RIDGE WITH
A BUILDING RIDGE TO THE SOUTH-SOUTHWEST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 46 KTS AT 301630Z
   CIMSS ADT: 51 KTS AT 301750Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 20-25 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: MODERATE POLEWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: HIGH

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TC 01S HAS SLOWED DUE TO A RELATIVELY WEAK
STEERING ENVIRONMENT ASSOCIATED WITH THE PASSAGE OF A DEEP
MIDLATITUDE MAJOR TROUGH TO THE SOUTH. THE SUBTROPICAL RIDGE IS
BUILDING TO THE SOUTH-SOUTHWEST AND IS EXPECTED TO CONTINUE TO
BUILD AS THE MIDLATITUDE TROUGH PROPAGATES EASTWARD OVER THE NEXT
24 HOURS. TC 01S WILL ACCELERATE WEST-NORTHWESTWARD THROUGH THE
FORECAST PERIOD AS THE STEERING RIDGE TO THE SOUTH STRENGTHENS. THE
SYSTEM WILL STEADILY WEAKEN DUE TO SIGNIFICANT DRY AIR AND
INCREASING VERTICAL WIND SHEAR WITH DISSIPATION ANTICIPATED BY TAU
48.  

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN TIGHT AGREEMENT
(THE MODEL SPREAD THROUGH TAU 48 IS 50NM OR LESS) LENDING HIGH
CONFIDENCE TO THE JTWC FORECAST TRACK. THE RELIABLE INTENSITY
GUIDANCE IS ALSO IN GOOD AGREEMENT SUPPORTING THE JTWC INTENSITY
FORECAST. 

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