Tropical Cyclone 04B (04B)

WTIO31 PGTW 010900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE 04B (FOUR) WARNING NR 003//
RMKS/
1. TROPICAL CYCLONE 04B (FOUR) WARNING NR 003    
   01 ACTIVE TROPICAL CYCLONE IN NORTHIO
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
   WIND RADII VALID OVER OPEN WATER ONLY
    ---
   WARNING POSITION:
   010600Z --- NEAR 21.9N 90.4E
     MOVEMENT PAST SIX HOURS - 310 DEGREES AT 16 KTS
     POSITION ACCURATE TO WITHIN 025 NM
     POSITION BASED ON CENTER LOCATED BY SATELLITE
   PRESENT WIND DISTRIBUTION:
   MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND
   RADIUS OF 034 KT WINDS - 000 NM NORTHEAST QUADRANT
                            080 NM SOUTHEAST QUADRANT
                            070 NM SOUTHWEST QUADRANT
                            000 NM NORTHWEST QUADRANT
   REPEAT POSIT: 21.9N 90.4E
    ---
   FORECASTS:
   12 HRS, VALID AT:
   011800Z --- 23.0N 88.4E
   MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND
    ---
REMARKS:
010900Z POSITION NEAR 22.2N 89.9E.
01AUG23. TROPICAL CYCLONE 04B (FOUR), LOCATED APPROXIMATELY 81 NM
WEST-SOUTHWEST OF CHITTAGONG, HAS TRACKED NORTHWESTWARD AT 16
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE 
IMAGERY (MSI) TOGETHER WITH ANIMATED RADAR IMAGERY PROVIDED A 
HIGH DEGREE OF CONFIDENCE TO THE INITAL LOCATION OF 04B. THE 
FULLY EXPOSED CIRCULATION HAS VERY RECENTLY MADE LANDFALL OVER 
SOUTHERN BANGLADESH AND IS FORECAST TO PROCEED INLAND, WHERE IT 
WILL QUICKLY DISSIPATE BY TAU 12. NUMERICAL MODELS AND RELIABLE 
MODEL INTENSITY GUIDANCE, BOTH ECHO THE JTWC TRACK AND 
INTENSITY FORECASTS, LENDING HIGH CONFIDENCE TO BOTH. MINIMUM CENTRAL 
PRESSURE AT 010600Z IS 990 MB.THIS IS THE FINAL WARNING ON THIS SYSTEM 
BY THE JOINT TYPHOON WRNCEN PEARL HARBOR HI. THE SYSTEM WILL BE 
CLOSELY MONITORED FOR SIGNS OF REGENERATION. 
MAXIMUM SIGNIFICANT WAVE HEIGHT AT 010600Z IS 15 FEET.//
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WDIO31 PGTW 010300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 04B (FOUR) 
WARNING NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.9N 91.7E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 84 NM SOUTH OF CHITTAGONG
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS AN EXPOSED
LOW LEVEL CIRCULATION CENTER (LLCC) WITH SPOTTY CONVECTION FLARING
UP ON THE WESTERN AND SOUTHERN SIDES OF THE CIRCULATION. ANIMATED
RADAR DATA FROM BANGLADESH SHOWS THE LLCC TO GOOD EFFECT, AND
COMBINED WITH THE MSI IMAGERY, PROVIDED HIGH CONFIDENCE TO THE
INITIAL POSITION. THE INITIAL INTENSITY REMAINS SET AT 40 KNOTS
WITH MEDIUM CONFIDENCE, HEDGED SLIGHTLY HIGHER THAN THE AGENCY
DVORAK INTENSITY ESTIMATES OF T2.0 (30 KNOTS) FROM BOTH PGTW AND
KNES, IN PERSISTENCE WITH EARLIER SCATTEROMETER DATA. CIMSS
ANALYSIS REVEALS A SIGNIFICANT INCREASE IN NORTHEASTERLY SHEAR, NOW
UP TO 25-30 KNOTS, BUT THE UPPER-LEVEL FLOW REMAINS DIVERGENT IN
THE VICINITY OF THE CIRCULATION, PROVIDING SOME EXHAUST FOR THE
FLARING CONVECTION. OUTSIDE OF THE SHEAR, THE ENVIRONMENT REMAINS
SUPPORTIVE, WITH VERY WARM SSTS AND ROBUST EQUATORWARD OUTFLOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WESTERN SIDE OF THE LOW TO MID-LEVEL
SUBTROPICAL RIDGE (STR) COMPLEX OVER SOUTHERN CHINA. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   KNES: T2.0 - 30 KTS
   DEMS: T1.0 - 25 KTS
   CIMSS ADT: 41 KTS AT 312330Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 25-30 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL CYCLONE (TC) 04B (FOUR) IS FORECAST
TO TRACK NORTHWESTWARD ALONG THE WESTERN SIDE OF THE STEERING
RIDGE, WITH LANDFALL EXPECTED WITHIN THE NEXT 12 HOURS IN THE
VICINITY OF KUAKATA, BANGLADESH. NO SIGNIFICANT CHANGE IN THE
INTENSITY ARE EXPECTED, WITH LANDFALL AT OR NEAR 40 KNOTS. AFTER
LANDFALL, THE SYSTEM WILL TRACK GENERALLY WEST-NORTHWEST WHILE
SLOWLY WEAKENING DUE TO LAND INTERACTION, BEFORE DISSIPATING OVER
EASTERN INDIA NO LATER THAN TAU 36. 

MODEL DISCUSSION: AVAILABLE TRACK GUIDANCE IS IN GOOD AGREEMENT
THROUGH THE FORECAST PERIOD, PROVIDING HIGH CONFIDENCE TO THE JTWC
FORECAST TRACK. INTENSITY GUIDANCE IS ALSO IN GOOD AGREEMENT,
THOUGH THE JTWC FORECAST DEVIATES ABOUT FIVE KNOTS HIGHER IN THE
FIRST 12 HOURS, BUT OTHERWISE ALIGNS WELL WITH THE GUIDANCE
PACKAGE, WITH HIGH CONFIDENCE. 

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