####018005666#### WTIN20 DEMS 011630 DEMS-RSMC TROPICAL CYCLONES NEW DELHI DATED 01.12.2023 SPECIAL TROPICAL WEATHER OUTLOOK FOR NORTH INDIAN OCEAN (THE BAY OF BENGAL AND THE ARABIAN SEA) VALID FOR NEXT 168 HOURS ISSUED AT 1530 UTC OF 01.12.2023 BASED ON 1200 UTC OF 01.12.2023. SUB: DEPRESSION OVER SOUTHWEST BAY OF BENGAL THE DEPRESSION OVER SOUTHEAST AND ADJOINING SOUTHWEST BAY OF BENGAL MOVED WEST-NORTHWESTWARDS WITH A SPEED OF 11 KMPH DURING PAST 06 HOURS AND LAY CENTERED AT 1200 UTC OF TODAY, THE 01 ST DECEMBER, 2023 OVER SOUTHWEST BAY OF BENGAL NEAR LATITUDE 10.0ON AND LONGITUDE 85.7OE, ABOUT 680 KM EAST-SOUTHEAST OF PUDUCHERRY (43331), 680 KM EAST- SOUTHEAST OF CHENNAI (43279), 790 KM SOUTHEAST OF NELLORE (43245), 860 KM SOUTH-SOUTHEAST OF BAPATLA (43220) AND 850 KM SOUTH-SOUTHEAST OF MACHILIPATNAM (43185). IT IS LIKELY TO MOVE WEST-NORTHWESTWARDS, INTENSIFY INTO A DEEP DEPRESSION BY 2 ND DECEMBER AND FURTHER INTO A CYCLONIC STORM OVER SOUTHWEST BAY OF BENGAL AROUND 3 RD DECEMBER. THEREAFTER, IT WOULD MOVE NORTHWESTWARDS AND REACH NEAR 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 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. TRACK & INTENSITY FORECASTS: DATE/TIME POSITION MAXIMUM SUSTAINED SURFACE CATEGORY OF CYCLONIC (LAT. 0N/ LONG.0E) WIND SPEED (KMPH) DISTURBANCE (UTC) 01.12.23/1200 10.0/85.7 45-55 KMPH GUSTING TO 65 KMPH DEPRESSION 02.12.23/0000 10.6/84.9 50-60 KMPH GUSTING TO 70 KMPH DEEP DEPRESSION 02.12.23/1200 11.2/83.7 55-65 KMPH GUSTING TO 75 KMPH DEEP DEPRESSION 03.12.23/0000 11.9/82.5 60-70 KMPH GUSTING TO 80 KMPH CYCLONIC STORM 03.12.23/1200 12.6/81.5 70-80 KMPH GUSTING TO 90 KMPH CYCLONIC STORM 04.12.23/0000 13.5/80.8 75-85 KMPH GUSTING TO 95 KMPH CYCLONIC STORM 04.12.23/1200 14.4/80.4 80-90 KMPH GUSTING TO 100 KMPH CYCLONIC STORM 05.12.23/0000 15.4/80.4 80-90 KMPH GUSTING TO 100 KMPH CYCLONIC STORM 05.12.23/1200 16.3/80.9 65-75 KMPH GUSTING TO 85 KMPH CYCLONIC STORM 06.12.23/0000 17.4/81.9 55-65 KMPH GUSTING TO 75 KMPH DEEP DEPRESSION 06.12.23/1200 18.5/83.4 45-55 KMPH GUSTING TO 65 KMPH DEPRESSION INSAT -3D IMAGERY AT 1200 UTC, INDICATES VORTEX OVER SOUTHEAST BAY OF BENGAL AND NEIGHBOURHOOD NOW LAY CENTERED WITHIN HALF A DEGREE OF 10.1ON/86.0OE WITH ASSOCIATED INTENSITY OF T1.5. 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 5.0ON TO 15.0ON LONGITUDE 80.0E TO 91.0E. MINIMUM CLOUD TOP TEMPERATURE IS MINUS 93 DEGREE CELSIUS. ASSOCIATED MAXIMUM SUSTAINED WIND SPEED IS 25 KNOTS GUSTING TO 35 KNOTS. ESTIMATED CENTRAL PRESSURE IS 1000 HPA. SEA CONDITION IS LIKELY TO BE ROUGH TO 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 1 ST TO 6 TH DECEMBER. THUS, MJO WOULD SUPPORT CYCLOGENESIS OVER THE BAY OF BENGAL (BOB) REGION TILL 6 TH DECEMBER. SEA SURFACE TEMPERATURE IS 28-30 0 C OVER MAJOR PARTS OF BOB. TROPICAL CYCLONE HEAT POTENTIAL IS 60-70 KJ/CM 2 OVER SOUTHEAST 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 DURING 01 \U2013 4 TH DECEMBER. ALL THESE LARGE SCALE FEATURES ARE FAVOURABLE FOR CYCLOGENESIS (INTENSIFICATION INTO A CYCLONIC STORM) OVER SOUTHWEST BOB. CURRENT ENVIRONMENTAL FEATURES INDICATE, POSITIVE LOW LEVEL VORTICITY OF 50X10 -6 S -1 AROUND SYSTEM CENTRE WITH VERTICAL EXTENSION UPTO 200 HPA LEVEL. POSITIVE LOW LEVEL CONVERGENCE IS ABOUT 5-10 X 10 -5 S -1 TO THE SOUTHEAST OF SYSTEM CENTRE. POSITIVE UPPER LEVEL DIVERGENCE IS ABOUT 30 X 10 -5 S -1 TO THE SOUTHWEST OF THE SYSTEM CENTRE. WIND SHEAR IS ABOUT 5-10 KNOTS OVER SOUTH BOB AND UPTO 12 0 N. LOW TO MODERATE CLOCKWISE DEEP LAYER WIND SHEAR IS SUPPORTING INTENSIFICATION OF THE SYSTEM. GUIDANCE FROM VARIOUS NUMERICAL MODELS IS INDICATING INITIAL NORTHWESTWARDS MOVEMENT TOWARDS ANDHRA PRADESH AND ADJOINING NORTH TAMIL NADU COASTS, WITH CROSSING OVER SOUTH ANDHRA PRADESH COAST AND NORTHEASTWARDS MOVEMENT ALONG THE COAST. THERE IS GOOD CONSENSUS AMONG THE MODELS WITH RESPECT TO MOVEMENT. WITH RESPECT TO INTENSIFICATION, MOST OF THE MODELS ARE INDICATING THE SYSTEM TO INTENSIFY INTO A CYCLONIC STORM. PEAK INTENSIFICATION OF 45 KNOTS IS SUGGESTED. HOWEVER, ECMWF IS INDICATING INTENSIFICATION UPTO DEEP DEPRESSION STAGE. IMD GFS IS INDICATING INTENSIFICATION UPTO VERY SEVERE CYCLONIC STORM. IMD MME IS INDICATING INTENSIFICATION UPTO 45 KNOTS (CYCLONIC STORM CATEGORY). CONSIDERING ALL THE ABOVE, THE DEPRESSION OVER SOUTHWEST BAY OF BENGAL IS LIKELY TO MOVE WEST-NORTHWESTWARDS AND INTENSIFY INTO A DEEP DEPRESSION BY 2 ND DECEMBER AND FURTHER INTO A CYCLONIC STORM OVER SOUTHWEST BAY OF BENGAL AROUND 3 RD DECEMBER. THEREAFTER, IT WOULD MOVE NORTHWESTWARDS AND CROSS SOUTH ANDHRA PRADESH COASTS BETWEEN NELLORE (43245) AND MACHILIPATNAM (43185) AROUND 0600 UTC OF 5 TH DECEMBER AS A CYCLONIC STORM.=