For short-term climate prediction and occasional weak monsoon rains in the Indian subcontinent, the event associated with it is El Niño and Southern Oscillations (ENSO). El Niño refers to a climate pattern characterized by the warming of the central and eastern tropical Pacific Ocean, which can have widespread impacts on weather patterns around the world.
During El Niño events, the sea surface temperatures in the central and eastern Pacific become unusually warm, leading to changes in atmospheric circulation patterns. These changes can disrupt the normal monsoon circulation over the Indian subcontinent and result in weaker monsoon rains.
El Niño events typically occur every few years and can persist for several months to a year or more. When an El Niño event coincides with the monsoon season in India, it often leads to below-average rainfall and drought conditions in the region. However, it`s important to note that not all El Niño events have the same impact on the Indian monsoon, and other factors can also influence monsoon variability.
While La Niña, the counterpart of El Niño characterized by cooler than average sea surface temperatures in the central and eastern tropical Pacific, can have different impacts on global weather patterns, it is typically associated with above-average monsoon rainfall in the Indian subcontinent.
The movement of jet streams and the greenhouse effects on a global level can influence long-term climate trends, but they are not specifically associated with occasional weak monsoon rains in the Indian subcontinent.