Monsoon regains strength as clouds cover India. IMD issues alert for Delhi & other cities

A massive shield of monsoon clouds has draped nearly two-thirds of India, signaling a major revival of monsoon activity after a brief seasonal lull. Data captured by the Indian Space Research Organisation’s (ISRO) INSAT-3DR weather satellite indicates that roughly 60-70% of the country's landmass is currently under dense cloud cover.

The satellite imagery reveals the dense massing of clouds. The thickest structures sit over the northern plains, spanning Punjab, Uttar Pradesh, Bihar, and West Bengal, while stretching heavily into the Northeast.

Long, active bands fed by moist winds from the Arabian Sea are also sweeping across the southern peninsula. Conversely, western Rajasthan and sections of Tamil Nadu remain comparatively clear. 

Concurrently, the India Meteorological Department (IMD) has issued localised alerts as the monsoon trough regains momentum. 

Regional impact & city-wise alerts 

Delhi: Following a hot and humid weekend with maximum temperatures touching 40 degrees Celsius, the national capital is entering a much more active monsoon phase. The IMD has forecast a sharp intensification of rain activity between July 20 and July 22, with widespread showers, scattered thunderstorms, and isolated heavy rainfall expected across Delhi and adjoining parts of the NCR. The heavy cloud cover and incoming precipitation are projected to drag daytime temperatures down significantly, dropping the maximum near 30 degrees Celsius by Tuesday.  

Mumbai: A yellow alert is in place as heavy showers returned over the weekend, with some areas recording over 30 mm of rainfall in just a two-hour span. The 24-hour forecast predicts a generally cloudy sky with sudden heavy spells at isolated locations, alongside thunderstorms and wind speeds reaching 30 to 40 kmph. 

Thane & Palghar: Neighboring districts have also been placed under a yellow alert. Residents are advised to expect localized downpours, lightning, and strong gusts matching Mumbai's trajectory as conditions turn favorable for sustained rain activity. 

Jammu and Srinagar: With cloud top temperatures dropping past minus 80 degrees Celsius, the region faces the highest probability of sudden, violent thunderstorms and localized intense downpours capable of triggering flash hazards in hilly terrains. 

Patna, Ranchi, and Lucknow: Pockets of cloud formations dropping below minus 50 degrees Celsius put Bihar, Jharkhand, and Uttar Pradesh on alert for frequent lightning strikes and intense short-duration rainfall spells as the main monsoon core passes overhead. 

Bengaluru and Hyderabad: Long bands of moisture moving from the Arabian Sea bring persistent overcast conditions across Karnataka and Telangana. While these systems are primarily yielding widespread drizzle and steady moderate showers, municipal zones remain on alert for sudden convective thunderclouds building up later in the day. 

Scientific Insights from Orbit 

Meteorologists utilising Cloud Top Brightness Temperature (CTBT) data have mapped the severity of these systems. The thermal infrared imagery recorded temperatures plunging below minus 80 degrees Celsius over Jammu and Kashmir, indicating exceptionally tall, violent thunderstorms pushing toward the top of the troposphere.

Pockets below minus 50 degrees Celsius were logged over Bihar, Jharkhand, Uttar Pradesh, the Northeast, and along bands covering Karnataka, Telangana, and Andhra Pradesh. 

The IMD noted that the active monsoon trough over northern India is acting as a self-powering engine. "Every kilogram of water vapour that condenses releases about 2.5 million joules of heat, driving updrafts that push clouds 15 km high," experts detailed.