Since the start of Summer season 2023 (March to May according to IMD classification) so far no IMD observatory in Tamil Nadu has touched 40°C yet as maximum temperature with the 39.6 recorded by the observatory at Erode being the highest recorded by a station in Tamil Nadu for the year so far. We will have to go back to more than 10 years to 2012 to find a year when no station in Tamil Nadu recorded or crossed 40°C during the first 7 weeks of a calendar year. To give a perspective on 2nd April 2021 seven stations from across the IMD network in Tamil Nadu recorded 42°C or more with Vellore recording a maximum temperature of 43.4°C gives an indication how subdued summer has been so far during 2023 for not just Tamil Nadu but large parts of the country.
If one were to run a reanalysis map from the NOAA Plotting tool the influence of Mid Latitude Westerly Trough over sub continent weather is visible in below average surface temperatures over large parts of Central India and Peninsular India, a look at the SPI Index Map created by IMD confirms the role of a string of WDs’ that brought in regular rainfall events over many areas of the Indian subcontinent not only increasing the soil moisture levels but also keeping a check on the temperatures as well. The last few weeks the presence of MJO over the Indian subcontinent certainly enhanced the rainfall prospects bringing a vitality to the thunderstorms.
But as the saying goes “All good things has to come to an end” so this spell of subdued heat also is expected to come to an end as drier weather partially influenced by the suppressed conditions brought by the East moving MJO wave which is likely to reduce the rainfall prospects over Peninsular India leading to not only drier weather conditions but also clearer skies. Additionally the train of Mid Latitude Westerly Troughs are also expected to slow down making things favorable for summer to crank up the heat from next week. Weather models are consistent the next few days Peninsular India may continue to see slightly below normal day time temperatures while from next week the remaining days of April may see mostly higher than average day time conditions increasing the maximum temperatures over most parts of Peninsular India and rest of the Indian subcontinent.
Chennai and North TN so far has enjoyed a relatively pleasant summer with 38°C recorded by Vellore on 27th March ’23 the highest among the North TN stations and 35.4°C recorded by Meenambakkam on the same day being the highest for Chennai stations. While almost all of Tamil Nadu may see an increase in day time temperatures during the second and third week of April, North TN including Chennai may bear the brunt of some of the heat from Rayalaseema move in pushing up the temperatures by 3 or 4 degrees compared to present max temperatures.