Over the past couple of weeks leeward plains of Tamil Nadu saw a break from thunderstorms as monsoon remained active. The much needed active phase of Monsoon saw copious inflows into the Cauvery basin bring Mettur to Full reservoir level. While we can feel happy about the water levels in dams the landslide over Wayanad brings us back to reality. It once again highlights how the fragile Western Ghats is extremely vulnerable to unmindful developmental activities. As a developing nation it becomes essential we strike a balance between development and environmental destruction.
As we often mention at times when monsoon heads for a break the pendulum shifts from West to East. It is during the break in monsoon period when leeward areas of Tamil Nadu sees enhanced thunderstorms. Sub seasonal weather models have been fairly consistent about this break in monsoon period coming into effect. One of the key factors in this transition dynamics is the MJO influenced intra-seasonal oscillation. MJO has been struggling against the changing base state from NIno to Nina over the past couple of months.
With a weak signal now over the Western Hemisphere there are indications a more coherent MJO transition may happen. This could mean a more pronounced Monsoon intra-seasonal oscillation may happen during the remaining days of this year’s Southwest Monsoon. What this would mean is a period of enhanced monsoon may follow this period once a fresh MJO signal emerges. The MISO may once again favour Peninsular India towards end August / early September when the MJO pulses makes its journey to East.
But in the meanwhile for the next couple of weeks when the West Coast takes a much needed break from rains leeward TN can look forward to thunderstorms. With a lot of remnant moisture available in the atmosphere over the next couple of days under right conditions some of the places could see extremely intense thunderstorms before things settle down a bit. Gradually as the westerlies weaken more places over the leeward areas will start seeing thunderstorms during evening / night hours. The sub seasonal extreme precipitation index has been consistently indicating a positively anomalous rainfall period for the week ending 12th August.
Looking at the wind charts South coastal AP and North coastal TN may benefit the most from the availability of this moisture. Today this stretch along with parts of South Coastal TN may see moderate to intense thunderstorms over many places. From today it is time to have your umbrellas and rain coats in your bag daily.