Advisories

WDIO31 PGTW 271500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 02B (ARNAB) WARNING NR 
007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.3N 82.7E
   INITIAL INTENSITY: 120 KTS
   GEOGRAPHIC REFERENCE: 497 NM SOUTHWEST OF KOLKATA, INDIA
   MOVEMENT PAST 6 HOURS: WESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 39 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
COMPACT SYSTEM APPROACHING LANDFALL WITH A DETERIORATING CONVECTIVE
PRESENTATION, CHARACTERIZED BY RAPID CLOUD-TOP WARMING AND 
CONTRACTION OF THE EYE FEATURE. ANIMATED RADAR DATA FROM THE INDIA 
METEOROLOGICAL DEPARTMENT (IMD) DEPICTS A QUICKLY FILLING EYE, WITH 
OUTERMOST SPIRAL BANDS BEGINNING TO BRUSH THE SHORELINE OF THE 
GODAVARI RIVER DELTA. A 271046Z SSMIS 89 GHZ MICROWAVE IMAGE REVEALED 
A SMALL INNER CORE OF DEEP CONVECTION FORMING AN INNER EYEWALL, AS 
WELL AS SIGNIFICANT DRY AIR TO THE EAST WRAPPING INTO THE CORE ALONG 
THE NORTHERN FLANK. THE INITIAL POSITION IS ASSESSED WITH HIGH 
CONFIDENCE BASED ON RADAR DATA AND EXTRAPOLATION OF THE 271046Z 
MICROWAVE IMAGERY. ANALYSIS OF CIMSS RAW ADT DATA SUGGESTS THE SYSTEM 
REACHED PEAK INTENSITY BETWEEN 271000Z AND 271030Z BEFORE BEGINNING 
TO DETERIORATE, THOUGH MAXIMUM SUSTAINED WINDS REMAIN ELEVATED. 
INITIAL INTENSITY IS INCREASED TO 120 KTS, ASSESSED WITH HIGH 
CONFIDENCE BASED ON THE OVERALL CONGRUENCE OF SUBJECTIVE AND 
OBJECTIVE INTENSITY ESTIMATES NOTED BELOW. ENVIRONMENTAL CONDITIONS 
REMAIN FAVORABLE OVERALL, WITH LOW TO MODERATE EASTERLY VERTICAL WIND 
SHEAR (VWS), WARM SEA SURFACE TEMPERATURES (SSTS), HIGH OCEANIC HEAT 
CONTENT (OHC), AND VIGOROUS POLEWARD OUTFLOW, TEMPERED BY PROXIMITY 
TO LAND, INCREASING MID-LEVEL SHEAR, AND DRY AIR ENTRAINMENT.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SOUTHWESTERN FLANK OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED OVER EXTREME SOUTHERN CHINA. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   DEMS: T4.5 - 77 KTS
   CIMSS SATCON: 114 KTS AT 271030Z
   CIMSS ADT: 122 KTS AT 271130Z
   CIMSS AIDT: 122 KTS AT 271130Z
   CIMSS D-MINT: 119 KTS AT 271046Z
   CIMSS D-PRINT: 121 KTS AT 271130Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: PROXIMITY TO LAND. 

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THE FORECAST HAS BEEN TRUNCATED TO 48
HOURS DUE TO ANTICIPATED DISSIPATION OVER LAND.

FORECAST DISCUSSION: TROPICAL CYCLONE (TC) 02B HAS MAINTAINED A
FASTER-THAN-EXPECTED WESTWARD TRAJECTORY OVER THE PAST SIX HOURS AND 
IS NOW APPROACHING THE COAST SLIGHTLY AHEAD OF SCHEDULE. HOWEVER, 
RECENT FRAMES OF BOTH EIR AND RADAR IMAGERY SUGGEST THE SYSTEM IS 
DECELERATING AS IT NEARS THE COASTLINE, AS ANTICIPATED BY GLOBAL 
GUIDANCE, DUE TO BINARY INTERACTION WITH INVEST 90B, WHICH IS RAPIDLY 
DEVELOPING APPROXIMATELY 280 NM TO THE SOUTHEAST. AS 90B PROPAGATES 
RAPIDLY NORTHWARD, IT WILL IMPART A DEFLECTIVE PULL, RETARDING TC 
02BS WESTWARD TRANSLATION, DELAYING LANDFALL, AND CAUSING A BRIEF 
STALL ALONG THE GODAVARI DELTA COASTLINE. NUMERICAL MODEL TRACKERS 
SMOOTH THIS MOTION OUT OVER 12-HOUR TIME STEPS; HOWEVER, PROGNOSTIC 
FIELDS IN GFS, ECMWF, HAFS-A, AND HWRF CLEARLY RESOLVE THIS NEAR-TERM 
BINARY OSCILLATION, DIFFERING ONLY IN WHERE LANDFALL OCCURS AND HOW 
FAR INLAND THE SYSTEM TRACKS BEFORE STALLING. THE FORECAST TRACK 
CALLS FOR LANDFALL ALONG THE SOUTHWESTERN COAST OF THE GODAVARI RIVER 
DELTA BY TAU 12, BUT PRIOR TO LANDFALL, THE SYSTEM IS LIKELY TO SKIRT 
THE COASTLINE OR STALL BRIEFLY. INVEST 90B IS MOVING RAPIDLY 
NORTHWARD, IS EXPECTED TO CONTINUE ACCELERATING, AND WILL BE 
POSITIONED NORTHEAST OF TC 02B WITHIN THE NEXT 12-18 HOURS. AS 90B 
EJECTS TO THE NORTHEAST, TC 02B WILL RESUME A NORTHWARD TRACK FROM 
TAU 12 ONWARD THROUGH THE REMAINDER OF THE FORECAST PERIOD ALONG THE
WESTERN PERIPHERY OF THE LOW- TO MID-LEVEL STR TO THE EAST. REGARDING
INTENSITY, THE SYSTEM PEAKED NEAR 271000Z; LAND PROXIMITY, 
STRENGTHENING EASTERLY SHEAR, AND DRY AIR INTRUSION ARE NOW IMPINGING 
ON THE INNER CORE, LEADING TO RAPID CONVECTIVE DETERIORATION. 
WEAKENING WILL CONTINUE, THOUGH LANDFALL OVER THE SATURATED DELTA 
REGION AND THE ASSOCIATED BROWN OCEAN EFFECT WILL MODERATE THE PACE 
OF WEAKENING THROUGH TAU 12. MORE RAPID WEAKENING WILL OCCUR AFTER 
TAU 12, WITH TC 02B FORECAST TO DISSIPATE OVER LAND BELOW THE 35-KT 
WARNING THRESHOLD WITHIN 48 HOURS DUE TO TERRAIN FRICTION. 

MODEL DISCUSSION: TRACK GUIDANCE IS IN STRONG AGREEMENT, THOUGH
NEAR-TERM TRACK DEVIATIONS ARE SMOOTHED OUT BY THE 12-HOUR TIME STEPS 
OF THE MODEL TRACKERS. NAVGEM IS THE ONLY OUTLIER, SHOWING LANDFALL 
ALONG THE NORTHEASTERN COAST OF THE GODAVARI DELTA REGION BEFORE 
TURNING NORTH. THE REMAINDER OF THE GUIDANCE PACKAGE IS CLOSELY 
PACKED AROUND THE JTWC FORECAST, WHICH IS POSITIONED NEAR THE MULTI-
MODEL CONSENSUS MEAN WITH HIGH CONFIDENCE. CONFIDENCE IS TEMPERED 
SOMEWHAT IN THE NEAR TERM DUE TO UNCERTAINTIES REGARDING THE BINARY 
INTERACTION WITH 90B AND THE EXACT TIMING AND LOCATION OF LANDFALL. 
INTENSITY GUIDANCE IS IN STRONG AGREEMENT. THE JTWC FORECAST IS 
PLACED ON THE UPPER EDGE OF THE ENVELOPE THROUGH TAU 12 TO ACCOUNT 
FOR THE BROWN OCEAN EFFECT, THEN TRACKS NEAR THE GOOGLE DEEPMIND 
(GDM) SOLUTION THROUGH THE REMAINDER OF THE FORECAST.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   INTENSITY 00-72 HR: MEDIUM//
NNNN