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Monday, December 4, 2023

Cyclone Michaung update !! - what is 'Madden Julian Oscillation' ??


Chennaites are under difficult times – heavy rains, no electricity as   Cyclone Michaung inched closer to the Tamil Nadu and Andhra Pradesh coasts.  The very heavy rainfall has led to severe waterlogging in many areas.  News reports especially social media are agog with spotting of a big mugger crocodile on the road !!  

According to India Today -    Seven people were killed and another was injured in several rain-related incidents in Chennai following heavy rainfall and gusty winds in the city triggered by Cyclone Michaung. Flight operations at Chennai airport were affected as runway was flooded, several flights were cancelled and others diverted in view of heavy rain due to Cyclone Michaung.

Ever heard of ‘Madden Julian Oscillation (MJO)’  !?!?  -    one  IMD bulletin read that MJO is at phase  4  with amplitude greater than 1.  One might have heard of -  ENSO,  one of the most important climate phenomena on Earth due to its ability to change the global atmospheric circulation, which in turn, influences temperature and precipitation across the globe.    ENSO is a single climate phenomenon, it has three states, or phases, it can be in.  The two opposite phases, “El Niño” and “La Niña,” require certain changes in both the ocean and the atmosphere because ENSO is a coupled climate phenomenon.  “Neutral” is in the middle of the continuum.

The recent Weather bulletin of IMD reads :  the Severe Cyclonic Storm “MICHAUNG” (pronounced as MIGJAUM) over West Central & adjoining Southwest Bay of Bengal off south Andhra Pradesh and adjoining north Tamilnadu coasts moved northwestwards with a speed of 10 kmph during past 06 hours and lay centered at 1430 hours IST of 4th December, 2023 over the same region near Latitude 13.7°N and Longitude 80.7°E, about 100 km northeast of Chennai, 120 km southeast of Nellore, 220 km north-northeast of Puducherry, 250 km south of Bapatla and 280 km south of Machilipatnam.

The cyclone is likely to intensify gradually and move nearly northwards almost parallel and close to south Andhra Pradesh coast and cross South Andhra Pradesh coast between Nellore and Machilipatnam, close to Bapatla during forenoon of 5th December as a Severe Cyclonic Storm with a maximum sustained wind speed of 90-100 kmph gusting to 110 kmph.

IMD has further forecast  light to moderate rainfall at most places of North Coastal Tamil Nadu with heavy to very heavy rainfall at a few places with isolated extremely heavy fall is likely on 4th and   isolated heavy rainfall on 5th December and decrease thereafter.  There is similar warnings for Coastal Andhra Pradesh, Telengana,  Yanam  and Rayalaseema.

In case you wondered what MJO was :   Imagine ENSO as a person riding a stationary exercise bike in the middle of a stage all day long. His unchanging location is associated with the persistent changes in tropical rainfall and winds that have been  described as being linked to ENSO. Now imagine another bike rider entering the stage on the left and pedaling slowly across the stage, passing the stationary bike (ENSO), and exiting the stage at the right. This bike rider we will call the MJO and he/she may cross the stage from left to right several times during the show.

So, unlike ENSO, which is stationary, the MJO is an eastward moving disturbance of clouds, rainfall, winds, and pressure that traverses the planet in the tropics and returns to its initial starting point in 30 to 60 days, on average. This atmospheric disturbance is distinct from ENSO, which once established, is associated with persistent features that last several seasons or longer over the Pacific Ocean basin.  

The Madden–Julian oscillation (MJO) is the largest element of the intraseasonal (30- to 90-day) variability in the tropical atmosphere. It was discovered in 1971 by Roland Madden and Paul Julian of the American National Center for Atmospheric Research (NCAR). It is a large-scale coupling between atmospheric circulation and tropical deep atmospheric convection.  

Most cases we do not understand jargon, common man’s mind is all about when will the rain stop !, will cyclone cross nearer my place and if so, what will be its effects, when electricity  and when normalcy will be restored. Immediate answers may not be available – better to stay at home and be safe.

With regards – S Sampathkumar

4/12/2023 @ 6.15 pm.

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