Weather report. Pre-monsoon holds sway as IMD rules out heatwave until May 10

Pre-monsoon weather often morphing as near-monsoon has settled across the country over the past couple of days marked by moderate to scattered to even heavy rainfall, thunderstorms, lightning, and high winds. In its extended forecast, India Meteorological Department (IMD) has ruled out heatwave conditions for any region at least until May 10.

The months of April and May are also known for violent types of weather to manifest over the Arabian Sea and the Bay of Bengal with the sea waters starting to warm up. Mrutyunjay Mohapatra, Director-General, IMD, said recently in New Delhi that there is a low probability of a low-pressure area/depression materialising over the Bay during this period.

Clouds loom large

On Tuesday morning, satellite pictures showed significant clouding (moisture) over the South-East Arabian Sea and South-West Bay of Bengal with some of them extending cover into the adjoining land over Kerala and Tamil Nadu. These normally grow in spatial coverage during the afternoon and evening as the land heats up during the day and allows seabreeze loaded with even more moisture to set in.

What will aid the process is a persisting cyclonic circulation over Maldives and a trough/wind discontinuity (a narrow corridor of lower pressure) that runs from West Vidarbha all the way down to South Interior Karnataka across Marathwada and North Interior Karnataka. The trough with its lower pressure (same as in the cyclonic circulation) acts as a ‘fire line’ packing needed fuel in the form of moisture from the sea that triggers thunderstorms and violent weather over the geography it passes.

Heavy rain in TN, Kerala

At 11.30 am this morning, clouds had settled over Thrissur, Kozhikode, and Thalassery in Kerala; Sakleshpura, Hassan, Chikkamagaluru, Bandipur National Park, Mysuru, Mandya, Kanakapura, Ramanagar, Tumakuru, Hosur, Bengaluru, and Chikkaballapur in South Interior Karnataka; adjoining Rayalaseema and Telangana; and Chennai, Mahabalipuram, Puducherry, Kancheepuram, Velur, Cuddalore, Mayiladuthurai, Tiruchirappalli, Thanjavur, and Nagapattinam in Tamil Nadu.

Monday saw moderate to heavy rainfall at isolated places over Tamil Nadu and Kerala. The highest rainfall (in cm) until 5.30 pm was recorded at Valparai (8) followed by Palayamkottai (5). Punalur in Kerala recorded five cm; Kakinada in Costa Andhra Pradesh four cm; and Tirupati in Rayalaseema, three cm. Hailstorm was observed over parts of Tamil Nadu and Coastal Andhra Pradesh.

Even more forecast

The forecast for today said heavy rainfall is likely over Coastal Andhra Pradesh, Yanam, Telangana, Rayalaseema, South Interior Karnataka, Tamil Nadu, Puducherry, Karaikal, Kerala, and Mahe.

Hailstorm with lightning, squall, lightning and gusty winds (speed of 30-40 kmph) is likely at isolated places over Telangana. Thunderstorms with lightning and gusty winds (40-50 kmph) are likely at parts of Coastal Andhra Pradesh, Yanam and Rayalaseema; and with lightning and gusty winds (30-40 kmph) over Interior Karnataka, Tamil Nadu, Puducherry, Karaikal, Kerala, Mahe, and Lakshadweep.

Outlook for the next four days said scattered/fairly widespread rainfall with thunderstorms, lightning, and gusty winds (40-50 kmph) is likely over the South Peninsula. Heavy rainfall may lash South Interior Karnataka, Coastal Andhra Pradesh, Telangana, Rayalaseema, Kerala, and Tamil Nadu on Tuesday and Wednesday. As for North-West India, a weather-altering western disturbance lies over Haryana, while a successor lay parked over South Pakistan with an induced cyclonic circulation over North-West Rajasthan.

Western disturbance

Given this, the IMD has forecast light to moderate fairly widespread to widespread rainfall/snowfall with thunderstorms, lightning and gusty winds (30-50 kmph) over North-West India until Wednesday and a gradual reduction in the activity thereafter. Hailstorms may strike parts of Uttarakhand during the next four days in Punjab, Haryana, Chandigarh, Delhi, Himachal Pradesh, and Uttar Pradesh today.

Other forecasts include thundersqualls (wind speeds of 50-60 kmph) over Uttarakhand today and tomorrow; heavy rainfall for parts of the Jammu division, Himachal Pradesh, Uttarakhand, and Punjab for today; and dust storms over West Rajasthan on Thursday. Over Central India, the IMD has forecast scattered to fairly widespread rainfall, thunderstorms, lightning, and gusty winds (40-50 kmph) for next two days. Hailstorm may lash isolated places over East Madhya Pradesh today.