WTIN20 DEMS 021540 REGIONAL SPECIALISED METEOROLOGICAL CENTRE-TROPICAL CYCLONES, NEW DELHI SPECIAL TROPICAL WEATHER OUTLOOK DEMS-RSMC TROPICAL CYCLONES NEW DELHI DATED 02.12.2023 SPECIAL TROPICAL WEATHER OUTLOOK FOR NORTH INDIAN OCEAN (THE BAY OF BENGAL AND THE ARABIAN SEA) VALID FOR NEXT 168 HOURS ISSUED AT 1500 UTC OF 02.12.2023 BASED ON 1200 UTC OF 02.12.2023. SUB: DEEP DEPRESSION OVER SOUTHWEST BAY OF BENGAL (CYCLONE ALERT FOR ANDHRA PRADESH AND ADJOINING NORTH TAMIL NADU- PUDUCHERRY COASTS: YELLOW MESSAGE) THE DEEP DEPRESSION OVER SOUTHWEST BAY OF BENGAL MOVED WEST- NORTHWESTWARDS WITH A SPEED OF 7 KMPH DURING PAST 06 HOURS AND LAY CENTERED AT 1200 UTC OF TODAY, THE 2ND DECEMBER, 2023 OVER THE SAME REGION NEAR LATITUDE 10.9N AND LONGITUDE 83.1E, ABOUT 380 KM EAST-SOUTHEAST OF PUDUCHERRY (43331), 390 KM SOUTHEAST OF CHENNAI (43279), 520 KM SOUTHEAST OF NELLORE (43245), 620 KM SOUTH-SOUTHEAST OF BAPATLA (43220) AND 620 KM SOUTH- SOUTHEAST OF MACHILIPATNAM (43185). IT IS LIKELY TO MOVE WEST-NORTHWESTWARDS AND INTENSIFY INTO A CYCLONIC STORM OVER SOUTHWEST BAY OF BENGAL DURING NEXT 12 HOURS. THEREAFTER, IT WOULD MOVE NORTHWESTWARDS AND REACH WESTCENTRAL BAY OF BENGAL OFF SOUTH ANDHRA PRADESH AND ADJOINING NORTH TAMILNADU COASTS BY 0600 UTC OF 4 TH DECEMBER. THEREAFTER, IT WOULD MOVE NEARLY NORTHWARDS ALMOST PARALLEL AND CLOSE TO SOUTH ANDHRA PRADESH COAST AND CROSS SOUTH ANDHRA PRADESH COAST BETWEEN NELLORE AND MACHILIPATNAM AROUND 0600 UTC OF 5TH DECEMBER AS A CYCLONIC STORM WITH A MAXIMUM SUSTAINED WIND SPEED OF 80-90 KMPH GUSTING TO 100 KMPH. Track and Intensity Forecasts: Date/Time Position Maximum sustained Category of cyclonic (UTC) (Lat.0N/long.0E) surface wind speed (Kmph) disturbance 02.12.23/1200 10.9/83.1 55-65 kmph gusting to 75 kmph Deep Depression 02.12.23/1800 11.3/82.7 55-65 kmph gusting to 75 kmph Deep Depression 03.12.23/0000 11.7/82.3 60-70 kmph gusting to 80 kmph Cyclonic Storm 03.12.23/0600 12.2/81.9 65-75 kmph gusting to 85 kmph Cyclonic Storm 03.12.23/1200 12.7/81.4 70-80 kmph gusting to 90 kmph Cyclonic Storm 04.12.23/0000 13.5/81.0 75-85 kmph gusting to 95 kmph Cyclonic Storm 04.12.23/1200 14.5/80.6 80-90 kmph gusting to 100 kmph Cyclonic Storm 05.12.23/0000 15.5/80.8 80-90 kmph gusting to 100 kmph Cyclonic Storm 05.12.23/1200 16.5/81.2 60-70 kmph gusting to 80 kmph Cyclonic Storm 06.12.23/0000 17.6/82.3 45-55 kmph gusting to 65 kmph Depression 06.12.23/1200 18.5/83.5 25-35 kmph gusting to 45 kmph Well Marked Low Pressure Area Cloud distribution: (a) Isolated: <25%, Scattered:25-50%, Broken: 51-75%, Solid:>75%, Convection Intensity: (a) Weak: Cloud Top Temperature (CTT) >-25C, (b) Moderate: CTT: - 25C to -40C, (c) Intense: CTT: - 41C to -70C and (d) Very Intense: : Less than -70C PROBABILITY OF CYCLOGENESIS (FORMATION OF DEPRESSION):NIL: 0%, LOW: 1-33%, , MODERATE: 34-66% AND HIGH: 67-100% This is a guidance Bulletin for WMO/ESCAP Panel Member countries. Visit respective National websites for Country specific Bulletins INSAT-3D IMAGERY AT 1200 UTC, INDICATE FURTHER ORGANISATION OF CLOUD MASS. ASSOCIATED INTENSITY IS T2.0. ASSOCIATED SCATTERED TO BROKEN LOW/MEDIUM CLOUDS WITH EMBEDED INTENSE TO VERY INTENSE CONVECTION LAY OVER SOUTH AND ADJOINING CENTRAL BAY OF BENGAL BETWEEN LATITUDE 6.0N TO 17.0N LONGITUDE 80.0E TO 90.0E. MINIMUM CLOUD TOP TEMPERATURE IS MINUS 93 DEGREE CELSIUS. ASSOCIATED MAXIMUM SUSTAINED WIND SPEED IS 30 KNOTS GUSTING TO 40 KNOTS. ESTIMATED CENTRAL PRESSURE IS 1000 HPA. SEA CONDITION IS LIKELY TO BE VERY ROUGH OVER THE SOUTHWEST & ADJOINING SOUTHEAST BAY OF BENGAL. MADDEN JULIAN OSCILLATION (MJO) IS CURRENTLY IN PHASE 3 WITH AMPLITUDE GREATER THAN 1. IT WOULD MOVE ACROSS PHASES 3 AND 4 WITH AMPLITUDE GREATER THAN 1 DURING 2 ND TO 6TH DECEMBER. THUS, MJO WOULD SUPPORT CYCLOGENESIS OVER THE BAY OF BENGAL (BOB) REGION TILL 6TH DECEMBER. SEA SURFACE TEMPERATURE ALONG 270C. TROPICAL CYCLONE HEAT POTENTIAL IS 60-70 KJ/CM2 OVER SOUTHWEST AND WESTCENTRAL BOB. THE NCICS BASED FORECASTS FOR EQUATORIAL WAVES INDICATE STRENGTHENING OF WESTERLY WINDS ALONGWITH PRESENCE OF EQUATORIAL ROSSBY WAVES & MJO OVER SOUTH BOB AND EASTERLY WINDS OVER CENTRAL BOB TILL 4 TH DECEMBER. THE CONVECTIVE CLOUD CLUSTERS ARE COMING CLOSER. ALL THESE LARGE SCALE FEATURES ARE FAVOURABLE FOR FURTHER INTENSIFICATION OF SYSTEM INTO A CYCLONIC STORM. CURRENT ENVIRONMENTAL FEATURES INDICATE, INCREASE IN POSITIVE LOW LEVEL VORTICITY TO 150X10-6S -1 AROUND SYSTEM CENTRE WITH VERTICAL EXTENSION UPTO 200 HPA LEVEL. THE VORTICITY FIELD SHOWS NO TILTING WITH HEIGHT. POSITIVE LOW LEVEL CONVERGENCE IS ALOMOST SAME DURING PAST 6 HOURS AND IS ABOUT 20 X 10-5 S -1 TO THE EAST OF SYSTEM CENTRE. POSITIVE UPPER LEVEL DIVERGENCE IS SAME AND IS ABOUT 30 X 10-5 S -1 TO THE NORTHEAST OF THE SYSTEM CENTRE WITH LESS DIVERGENCE EQUATORWARD. THUS, EQUATORWARD OUTFLOW IS DECREASED AND POLEWARD OUTFLOW IS INCREASED. THERE IS NOT MUCH CHANGE IN WIND SHEAR AND IS ABOUT 10-20 KNOTS OVER SOUTHWEST BOB. TOTAL PRECIPITABLE WATER IMAGERY IS INDICATING WARM MOIST AIR ADVECTION FROM SOUTH AND SOUTHEAST SECTOR. UPPER TROPOSPHERIC RIDGE RUNS ALONG 140N. FROM 4TH DECEMBER/0000 UTC, THE SYSTEM WILL COME CLOSER TO THE RIDGE AND HENCE WOULD MOVE NEARLY NORTHWARDS AND BY 5TH /0000 UTC, IT WOULD CROSS RIDGE AND HENCE RECURVE NORTHEASTWARDS FROM 5TH DECEMBER/0000 UTC. UPPER TROPOSPHERIC WINDS ARE OF THE ORDER OF 50-60 KNOTS OVER NORTH ANDHRA PRADESH AND ODISHA COASTS. IT WOULD LEAD TO HIGHER WIND SHEAR. MOST OF THE MODELS ARE INDICATING INTIAL WEST-NORTHWESTWARDS MOVEMENT FOLLOWED BY NORTHWESTWARDS MOVEMENT TOWARDS ANDHRA PRADESH COAST. THE LANDFALL POINT IS VARYING BETWEEN LATITUDE 15.5-16.5 0N/80.0-82.00E. HOWEVER, NCUM MODEL IS INDICATING LANDFALL NEAR 13.3N/80.1E. IMD MME IS INDICATING LANDFALL NEAR 16.3N/81.2E. THE LANDFALL TIME IS VARYING BETWEEN 4TH/1800 UTC TO 5TH /1500 UTC. CONSIDERING ALL THE ABOVE, THE DEEP DEPRESSION IS LIKELY TO MOVE WEST- NORTHWESTWARDS AND INTENSIFY INTO A CYCLONIC STORM OVER SOUTHWEST BAY OF BENGAL DURING NEXT 12 HOURS. THEREAFTER, IT WOULD MOVE NORTHWESTWARDS AND REACH WESTCENTRAL BAY OF BENGAL OFF SOUTH ANDHRA PRADESH AND ADJOINING NORTH TAMILNADU COASTS BY 0600 UTC OF 4 TH DECEMBER. THEREAFTER, IT WOULD MOVE NEARLY NORTHWARDS ALMOST PARALLEL AND CLOSE TO SOUTH ANDHRA PRADESH COAST AND CROSS SOUTH ANDHRA PRADESH COAST BETWEEN NELLORE AND MACHILIPATNAM AROUND 0600 UTC OF 5 TH DECEMBER AS A CYCLONIC STORM WITH A MAXIMUM SUSTAINED WIND SPEED OF 80-90 KMPH GUSTING TO 100 KMPH.