Tropical Cyclone Arnab

WDIO31 PGTW 262100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 02B (ARNAB) WARNING NR 
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.0N 85.8E
   INITIAL INTENSITY: 80 KTS
   GEOGRAPHIC REFERENCE: 422 NM SOUTH-SOUTHWEST OF KOLKATA, INDIA
   MOVEMENT PAST 6 HOURS: WESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 28 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
CYCLONE (TC) 02B WITH CONTINUED PERSISTENT DEEP CONVECTION AROUND
ITS COMPACT CORE. THE SYSTEM HAS BEEN UNABLE TO MAINTAIN AN EYE IN
THE EIR IMAGERY, BUT IT HAS OCCASIONALLY PEEKED OUT OVER THE PAST
FEW HOURS. A 261835Z GMI 37 GHZ MICROWAVE IMAGE CONFIRMED THE
SYMMETRY OF THE COMPACT CORE AND MICROWAVE EYE. THE INITIAL
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON A DIMPLE EYE THAT
WAS PRESENT AT THE TIME OF ANALYSIS AND THE MICROWAVE EYE IN THE
AFOREMENTIONED GMI IMAGERY. THE INITIAL INTENSITY OF 80 KTS IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON A BLEND OF THE AGENCY
DVORAK FIXES ON THE LOWER END AND CIMSS INTENSITY ESTIMATES ON THE
HIGHER END. STRUCTURALLY, THE SYSTEM MAINTAINED ITS SATELLITE
APPEARANCE OVER THE PAST 6 HOURS, SUPPORTING A CONSTANT INTENSITY
TREND. THE ENVIRONMENT IS CHARACTERIZED AS HIGHLY FAVORABLE, WITH
GOOD RADIAL OUTFLOW ALOFT, WARM SEA SURFACE TEMPERATURES, AND LOW
VERTICAL WIND SHEAR (VWS).

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: COMPETING INFLUENCES FROM A SUBTROPICAL
RIDGE (STR) TO THE NORTHEAST AND A DEEP-LAYER TROUGH TO THE
SOUTHWEST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   DEMS: T4.0 - 65 KTS
   CIMSS SATCON: 90 KTS AT 261830Z
   CIMSS ADT: 79 KTS AT 261800Z
   CIMSS AIDT: 78 KTS AT 261800Z
   CIMSS D-MINT: 79 KTS AT 261613Z
   CIMSS D-PRINT: 82 KTS AT 261730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE RADIAL

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: THE TRACK SPEED OF TC 02B ACCELERATED OVER THE
PAST 6 HOURS IN A DUE WEST DIRECTION, PRIMARILY UNDER THE INFLUENCE
OF THE STR TO THE NORTHEAST. THE TRACK IS FORECAST TO TURN SHARPLY
POLEWARD AFTER TAU 24 AS THE STEERING RIDGE FULLY ASSERTS CONTROL
OVER THE SYSTEM. LANDFALL OVER SOUTHEASTERN INDIA IS EXPECTED
BETWEEN TAU 36 AND 48 AS THE TRACK CONTINUES NORTHWARD INTO CENTRAL
INDIA. CONTINUED INTENSIFICATION IS FORECAST IN THE HIGHLY
FAVORABLE ENVIRONMENT OVER THE NEXT 12 HOURS, THEN LEVEL OFF AS THE
OUTER PERIPHERY BEGINS TO INTERACT WITH THE INDIAN SUBCONTINENT.
RAPID WEAKENING OVER LAND IS FORECAST AFTER TAU 36, WITH
DISSIPATION EXPECTED BY TAU 72. 

MODEL DISCUSSION: MODEL TRACK GUIDANCE IS IN GOOD AGREEMENT ABOUT
THE WESTWARD TRACK OVER THE BAY OF BENGAL FOLLOWED BY A SHARP
POLEWARD TURN. THE JTWC TRACK FORECAST IS PLACED CLOSE TO THE
MULTI-MODEL CONSENSUS, WHICH IS ALSO IN GOOD AGREEMENT WITH THE
GOOGLE DEEPMIND SOLUTIONS. AS FOR INTENSITY, SEVERAL RAPID
INTENSIFICATION AIDS TRIGGERED THIS CYCLE AND THE JTWC INTENSITY
FORECAST IS REFLECTIVE OF THAT WITH A SHORT-TERM SPIKE IN
INTENSITY. THE INTENSITY FORECAST THAN FOLLOWS CLOSE TO THE
MULTI-MODEL CONSENSUS, WHICH REMAINS ELEVATED BY THE DECAY SHIPS
MODEL.

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