WTIN20 DEMS 311825 DEMS-RSMC SPECIAL TROPICAL CYCLONES NEW DELHI DATED 31.10.2026 SPECIAL TROPICAL WEATHER OUTLOOK FOR THE NORTH INDIAN OCEAN (THE BAY OF BENGAL AND THE ARABIAN SEA) VALID FOR THE NEXT 168 HOURS ISSUED AT 1800 UTC OF 31.10.2026 BASED ON 1200 UTC OF 31.10.2026. SUB: DEPRESSION OVER SOUTHEAST BAY OF BENGAL THE DEPRESSION OVER SOUTHEAST BAY OF BENGAL AND ADJOINING AREAS OF ANDAMAN & NICOBAR ISLANDS AND ANDAMAN SEA MOVED WEST-NORTHWESTWARDS WITH SPEED OF 30 KMPH DURING PAST 6 HOURS AND LAY CENTERED AT 1200 UTC OF TODAY, THE 31ST OCTOBER, 2026 OVER SOUTHEAST BAY OF BENGAL, NEAR LATITUDE 10.5ON AND LONGITUDE 88.6OE, ABOUT 960 KM EAST-SOUTHEAST OF CHENNAI (CHENNAI, 43279), 980 KM SOUTHEAST OF VISHAKHAPATNAM (ANDHRA PRADESH, 43149) AND 1030 KM SOUTHEAST OF MACHILIPATNAM (ANDHRA PRADESH, 43185) AND 1080 KM EAST-SOUTHEAST OF ONGOLE (ANDHRA PRADESH, 43221). IT IS VERY LIKELY TO MOVE WEST-NORTHWESTWARDS AND INTENSIFY INTO A DEEP DEPRESSION OVER SOUTHEAST BAY OF BENGAL BY 1800 UTC OF TODAY, INTO A CYCLONIC STORM OVER THE SAME REGION ON 1ST NOVEMBER AND INTO A SEVERE CYCLONIC STORM OVER WESTCENTRAL BAY OF BENGAL ON 2ND NOVEMBER. IT IS VERY LIKELY TO REACH OVER WESTCENTRAL BAY OF BENGAL NEAR SOUTH ANDHRA PRADESH COAST 2100 UTC OF 3RD NOVEMBER AND CROSS SOUTH ANDHRA PRADESH COAST AS A SEVERE CYCLONIC STORM WITH WIND SPEED OF 100 TO 110 KMPH GUSTING 120KMPH BETWEEN NELLORE AND NARSAPUR BY 0300 UTC OF 3RD NOVEMBER 2026. FORECAST LOCATION AND INTENSITY ARE GIVEN IN FOLLOWING TABLE: DATE/TIME POSITION MAXIMUM SUSTAINED SURFACE CATEGORY OF CYCLONIC (IST) (LAT. 0N/ LONG. 0E) WIND SPEED (KMPH) DISTURBANCE 31.10.26/1230 10.5/88.6 45-55 GUSTING TO 65 DEPRESSION 31.10.26/1830 10.9/88.2 50-60 GUSTING TO 70 DEEP DEPRESSION 01.10.26/0530 11.3/87.3 60-70 GUSTING TO 80 CYCLONIC STORM 01.11.26/1130 11.8/86.3 65-75 GUSTING TO 85 CYCLONIC STORM 01.11.26/1730 12.3/85.4 70-80 GUSTING TO 90 CYCLONIC STORM 02.11.26/0530 13.2/83.4 80-90 GUSTING TO 100 CYCLONIC STORM 02.11.26/1730 14.3/81.6 90-100 GUSTING TO 110 SEVERE CYCLONIC STORM 03.11.26/0530 15.4/80.3 100-110 GUSTING TO 120 SEVERE CYCLONIC STORM 03.11.26/1730 16.6/79.2 70-80 GUSTING TO 90 CYCLONIC STORM 04.11.26/0530 17.9/78.1 50-60 GUSTING TO 70 DEEP DEPRESSION 04.11.26/0530 19.3/77.3 35-45 GUSTING TO 55 DEPRESSION THE ESTIMATED CENTRAL PRESSURE IS 1008 HPA AND MAXIMUM SUSTAINED WIND SPEED IS 25 KT GUSTING TO 35KT. A BUOY NEAR 15.6ON/88.0OE REPORTED MSLP OF 1015.0 HPA AND MSW 800 (WIND DIRECTION)/10.0KT, ANOTHER, BUOY NEAR 6.0N/90.3E REPORTED MSLP OF 1014.0 AND MSW 240 0 (WIND DIRECTION)/10.0KT. HATBAY (43364) REPORTED MSLP OF 1012.2 HPA AND MSW 230 0 (WIND DIRECTION)/1.0KT, AND MAYABANDAR (43309) REPORTED MSLP OF 1013.1 HPA AND MSW 50 0 (WIND DIRECTION)/2.0KT AS PER LATEST INSAT 3DS IMAGERY BASED ON 1200 UTC VORTEX OVER SOUTHEAST BAY OF BENGAL AND NEIGHBOURHOOD CENTRED NEAR 10.3N / 88.5E INETENSITY T1.5. SPIRAL BANS ARE APPEARING THE CLOUD IMAGING INDICATE SHEAR TO NORTHWEST, FURTHER THE SPIRAL BANDS ALSO APPEARING IN THE NORTHERN SECTOR. THE CLOUD SHOWS GRADUAL ORGANIZING DURING PAST 12 HOURS. ASSOCIATED SCATTERED TO BROKEN LOW/MEDIUM CLOUDS WITH EMBEDDED INTENSE TO VERY INTENSE CONVECTION OVER SOUTHEAST ADJACENT TO CENTRAL BAY OF BENGAL , ANDAMAN & NICOBAR ISLANDS WITH MINIMUM CTT -70OC TO -90OC. BASED ON HYSAT 008UTC AND OCEANSAT BASED ON 0706 UTC SCRATEROMETER BASED WINDS INDICATES AN STRONGER INDICATE NORTHEAST & ADJOIN SOUTHEAST SECTOR WITH SPEED REACHING 25-35 KTS. IT IS 25-35 KTS IN NORTHWEST SECTOR AND 10-15 KTS IN SOUTHWEST SECTOR. REMARKS: SEA SURFACE TEMPERATURE IS AROUND 290C OVER ANDAMAN SEA AND ENTIRE BOB. IT HAS REDUCED BY 10C OVER THE REGION COMPARED TO LAST WEEK. THE OCEAN HEAT CONTENT IS 60-70 KJ/CM2 COMPARED TO 100 KJ/CM2 DURING VERY SEVERE CYCLONIC STORM \U2018ARNAB\U2019. THE MADDEN JULIAN OSCILLATION (MJO) IS CURRENTLY IN PHASE 3 WITH AMPLITUDE MORE THAN 1. IT IS LIKELY TO CONTINUE IN SAME PHASE DURING THE ENTIRE FORECAST PERIOD WITH AMPLITUDE MORE THAN 1. THE GUIDANCE FROM THE NCICS MODEL INDICATES THE PREVALENCE OF WESTERLY WIND ANOMALY (>9 MPS) ALONGWITH MJO OVER SOUTH BAY OF BENGAL AND SOUTH ANDAMAN SEA AND EASTERLY WIND ANOMALY (>9 MPS) ALONGWITH KELVIN WAVE (KW) TO ITS NORTH OVER NORTH BOB AND ADJOINING AREAS OF EASTCENTRAL BOB. PREVALENCE OF KELVIN WAVE IN THE NORTHERN PARTS OF BOB WILL ENHANCE EXTRA-TROPICAL WESTERLIES OVER THE NORTH BOB. IT WILL BRING COLD AND DRY AIR FROM NORTHWEST OVER THE REGION, WHICH IS NOT SUPPORTIVE FOR HIGHER INTENSIFICATION OF THE SYSTEM. HOWEVER AT THE SAME TIME, ACTIVE MJO PHASE IS PERSISTING OVER THE REGION WHICH WILL ENHANCE CONVECTIVE ACTIVITY AND HENCE INTENSIFICATION OF DEPRESSION OVER BOB. VARIOUS ENVIRONMENTAL FEATURES INDICATES, THE POSITIVE LOW-LEVEL VORTICITY AT 850 HPA HAS INCREASED DURING PAST 24 HOURS AND IS AROUND 100 X10-6 S -1 OVER SYSTEM AREA WITH VERTICAL EXTENSION UP TO 500 HPA. THE LOW LEVEL CONVERGENCE IS THE SAME IN PAST 24 HOURS AND IS AROUND 5 X10-6 S -1 OVER SYSTEM AREA. UPPER-LEVEL DIVERGENCE HAS INCREASED IN PAST 24 HOURS AND IS AROUND 20X10-6 S -1 OVER SYSTEM AREA. MID-LEVEL WIND- SHEAR (500-850 HPA) IS LOW (5-10 KT) AROUND THE SYSTEM CENTRE. THE AREA OF MAXIMUM CONVERGENCE AND DIVERGENCE SUPERIMPOSED WITH EACH OTHER. THE MID-LEVEL WIND-SHARE, WHILE IT IS ANTICLOCKWISE IMMEDIATELY NEAR THE SYSTEM CENTER (UPTO 85OE) IT BECOME CLOCKWISE OVER SOUTHWEST WEST CENTRAL BAY OF BENGAL, HENCE SUCH TYPE OF SHEAR WILL SUPPORT INTENSIFICATION WHILE THE SYSTEM WILL MOVING TOWARDS THE COAST, AFTER REACHING 85N. THE RATE OF INTENSIFICATION MAY INCREASE FROM 1ST NOVEMBER EVENING DUE TO SUCH SUPPORTIVE WIND SHEAR. THE HIGH-LEVEL WIND SHEAR IS ALSO LOW TO MODERATE AROUND THE SYSTEM CENTRE AND ALONG THE FORECAST TRACK. THE ANTI-CYCLONIC SHEAR PREVAILS OVER THE ENTIRE AREA OF SOUTH AND CENTRAL BAY OF BENGAL AND ALONG SOUTH PENINSULAR WHICH IS SUPPORT INTENSIFICATION OF THE SYSTEM. AN UPPER TROPOSPHERIC RIDGE RUNS 17ON IN ASSOCIATION WITH ANTICYCLONE OVER MYANMAR, STEERING THE SYSTEM WEST-NORTHWARDS, HOWEVER AS THE SYSTEM MOVES WEST-NORTHWARDS AND ENTER SOUTHWEST BAY OF BENGAL AND IT WILL LIE IN THE OUTER PERIPHERY OF THIS RIDGE, AND HENCE MOVE NORTHWESTWARDS, AND CROSS SOUTH ANDHRA PRADESH. AFTER THE LANDFALL IT WILL LIES CLOSE TO THE RIDGE AND HENCE IT WILL MOVE INTO NORTHWARDS AND NORTH- NORTHEAST WARDS. AT THE SIMULTANEOUSLY IT WILL INFLUENCE THE UPPER TROPOSPHERIC TROUGH WHICH CURRENTLY RUNS ALONG 65OE & IT WILL BE MOVING TOWARDS 75OE BY 3RD NOVEMBER 2026. IT WILL ALSO NOT ALLOW THE SYSTEM TO MOVE WESTWARDS RATHER IT WILL HELP IN RECURVING NORTH-NORTHEAST WARDS. THE TOTAL PRECIPITABLE WATER IMAGERY INDICATES WARM MOIST AIR INCURSION INTO THE CORE FROM AROUND THE SYSTEM AND ALSO SYSTEM FORECAST TRACK. HOWEVER, COLD AIR INCURSION IS REACHING OUTER PERIPHERY OF THE SYSTEM IN THE SOUTHWESTERN SECTOR FROM SOUTH INTERIOR PENINSULAR. AS THE SYSTEM IS EXPECTED TO MOVE TOWARDS SOUTH ANDHRA PRADESH, IT MAY NOT HELP IN WEAKENING THE SYSTEM. IR-WV IMAGERY INDICATES INTENSE CONVECTION (COLDER THAN -4 0C) TO THE NORTHEAST OF SYSTEM CENTRE. THUS MJO, HIGH SST, LOW VERTICAL WIND SHEAR MAY SUPPORT FURTHER DEVELOPMENT OF SYSTEM. THE MODEL DIAGNOSIS BASED ON GLOBAL AND REGIONAL MODELS INDICATES, THAT CURRENT HIGH LEVEL (LOW TO MODERATE) WINDS SHEAR IS EXPECTED TO DECREASE BECOMING LOW WIND SHEAR BY 00UTC OF 1ST NOVEMBER 2026. THE LOW WIND SHEAR WILL CONTINUE TILL 00UTC OF 3RD NOVEMBER 2026 SUPPORTING INTENSIFICATION. MIDDLE LEVEL RELATIVE HUMIDITY IS AT PRESENT ABOUT 70% WHILE IT IS EXPECTED TO DECREASE SLIGHTLY BY 1ST NOVEMBER AND IT MAY INCREASE THEREAFTER TILL 3RD NOVEMBER REACHING ABOUT 70-75%. THUS SUPPORTS THE INTENSIFICATION. ALL THE MODELS LIKE ECMWF, AI-FGN, AI-FCN, EC-AIFS, AURORA, GOOGLE DEEPMIND AND HWRF ARE INDICATING EVEN INTENSIFICATION OF CYCLONIC STORM/SEVERE CYCLONIC STORM. GFS GROUP OF MODEL ARE SHOWING AN INTENSITY OF LOW PRESSURE AREA ONLY. HOWEVER, THERE IS A VERY GOOD CONSENSUS AMONG VARIOUS MODELS WRT WEST-NORTHWESTWARDS MOVEMENT INITIALLY FOLLOWED BY NORTHWEST WARD MOVEMENT TOWARDS SOUTH ANDHRA PRADESH COAST. MANY OF AI MODELS AND ECMWF MODEL ARE SUGGESTING NORTH-NORTHEAST WARDS OF RECURRING AFTER LANDFALL, WHILE GFS SYSTEM SHOW WESTWARDS MOVEMENT INSIDE SOUTHERN PENINSULAR AFTER LANDFALL. HENCE CONSIDERING THE ENVIRONMENTAL FEATURES, CLIMATOLOGICAL GUIDANCE AND MODEL GUIDANCE, MODERATE TO HIGH PROBABILITY IS ASSIGNED FOR INTENSIFICATION INTO A SEVERE CYCLONIC STORM BY 2ND NOVEMBER 2026. CONFIDENCE LEVEL IN ESTIMATION OF: (A) CURRENT LOCATION AND INTENSITY: HIGH (B) FORECAST TRACK: HIGH (C) FORECAST INTENSITY: MOD-HIGH=