La Niña Delays and Its Impact on India’s Weather

  • 07 Sep 2024

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  • Current Conditions:
    • The India Meteorological Department (IMD) reported neutral Indian Ocean Dipole (IOD) conditions.
    • La Niña is expected to develop towards the end of the monsoon season, around the end of this month.
  • Forecasting Challenges:
    • Major global agencies have struggled with accurate forecasts for La Niña’s onset this year.
    • Initial predictions suggested La Niña would start around July, but it has been delayed.
  • Understanding La Niña:
    • La Niña, meaning "The Little Girl" in Spanish, is a phase of the El Niño Southern Oscillation (ENSO).
    • ENSO influences global climate through changes in tropical Pacific Ocean sea surface temperatures.
    • ENSO phases:
      • El Niño (warm phase)
      • La Niña (cool phase)
      • Neutral
  • ENSO Phases Explained:
    • Neutral Phase: Eastern Pacific is cooler; trade winds drive warm water westward, causing upwelling of cooler waters.
    • El Niño Phase: Weakened trade winds result in warmer eastern Pacific waters.
    • La Niña Phase: Strengthened trade winds push more warm water to the western Pacific, cooling the eastern Pacific.
  • Impact on India:
    • El Niño typically reduces monsoon rainfall; La Niña generally enhances it.
    • The previous El Niño occurred from June 2023 to May 2024.
    • La Niña episodes can influence severe weather patterns and are linked to higher temperatures, heavy precipitation, and droughts.
  • Weather Model Predictions:
    • A strong El Niño ended in June, transitioning ENSO to neutral.
    • Global models initially forecasted La Niña for July but revised this to August-October.
    • IMD’s forecast since April predicted La Niña in the latter half of the monsoon season, aiming for enhanced rainfall in August and September.
  • Reasons for Delayed Onset:
    • The expected La Niña might be weak, complicating predictions.
    • Other atmospheric factors, including the Madden-Julian Oscillation, impact weather models.
  • Current and Future Impacts:
    • La Niña's first signs are expected by late September or early October.
    • It is projected to peak in November and continue through the northern hemisphere winter.
    • Monsoon Impact: La Niña’s delayed onset means it won’t significantly affect the current southwest monsoon, though India saw a 16% surplus in August rainfall and a forecast of 109% “above normal” rain for September.
  • Potential Effects:
    • Northeast Monsoon: La Niña could influence the northeast (winter) monsoon (October-December), impacting Tamil Nadu, coastal Andhra Pradesh, Rayalaseema, south interior Karnataka, and Kerala. While La Niña typically doesn’t favor northeast monsoon rainfall, exceptions have occurred.
    • Cyclone Activity: La Niña years often see increased cyclone activity in the north Indian Ocean, with higher intensity and longer-lasting storms.
    • Winter Weather: Historically, La Niña years lead to harsher and colder winters, suggesting a potentially severe winter ahead.