Cyclone Nivar : Explained | UPSC
Cyclone Nivar may hit Tamil Nadu Wednesday: IMD
WHY IN NEWS:
Cabinet Secretary chairs National Crisis Management Committee Meeting
SYLLABUS COVERED: GS 1 : Geography : Cyclones
For PRELIMS it is important to understand the importance of pacific ridge and the impact of La Nina over the cyclone of Bay of Bengal .
For MAINS keep an eye on the disaster management, precautionary methods and also warning systems . Let us dive in !
- Cyclone Nivar might make landfall along the Tamil Nadu coast between Karaikal and Mahabalipuram on the afternoon of November 25.-IMD.
- However, any predictions by IMD have to be treated with caution as cyclones in the last few years have been highly unpredictable.
CYCLONE PATH TRAJECTORY
RISE IN SEA SURFACE TEMPERATURE
- Warm ocean waters in the Bay of Bengal, Arabian Sea and the Indian Ocean have been a result of anthropogenic global warming.
- Just this August, low pressure systems, which are the precursor storm systems to cyclones, during the monsoon season caused extremely heavy rainfall along a central belt across the country from Odisha to Gujarat.
- One reason for the heavy rainfall in August was the unusually warm Arabian Sea.
- The normal sea surface temperatures here are about 28-29°C, the temperatures this August reached up to 29-31°C.
- The sea surface temperatures in the Bay of Bengal are also in the range of 29-30°C,-IMD
ALERTS AND WARNING – IMD
- A deep depression in October had also carried much more rainfall than normal, causing extremely heavy rainfall in many parts of Telangana and Andhra Pradesh.
- The coastal areas of Andhra Pradesh and Yanam have also been kept under an “orange alert” —meaning “be prepared”.
- Hyderabad witnessed one of its heaviest showers in the century and floods that brought large portions of the city to a standstill.
- More rainfall than normal is another concern around cyclones in a world of climate change.
IMPACT OF LA NINA
- Another important factor for cyclone formation and behaviour in this season would be the prevalence of the La Niña phenomenon in the equatorial Pacific Ocean.
- On October 29 the WMO declared the prevalence of a moderate to strong La Niña event in the central and eastern equatorial Pacific Ocean.
- The phenomenon will continue till the end of the year and continue into the first quarter of 2021.
- This year has been a bumper year in the Atlantic so the Pacific and Indian Oceans are somewhat calmer.
- The total number of cyclones doesn’t increase that much so a higher number in the Atlantic tends to keep the numbers low in the other oceans.
NAMING OF CYCLONE
- IMD noted the cyclonic storm was christened Cyclone Nivar by Iran.
- Nivar currently lies as a depression some 600 km south south east of Puducherry in the Bay of Bengal.
- It will intensify into a deep depression by the evening of November 23 and a cyclone by the morning of November 24.
- The wind speeds at the time of landfall are likely to be in the range of 100-110 kilometres per hour.
- This will be first cyclone to make landfall on the Indian coast in 2020.
- It might bring heavy rainfall to the southern states of Tamil Nadu, Andhra Pradesh, Karnataka and Telangana from November 24-26.
Sources : IMD | Cyclone Nivar : Explained | UPSC
WHY CYCLONE IS STEERING TO NORTH TAMIL NADU?
- As you can see majority of our Cyclone will be steered by the Pacific ridge with upper steering(refer image below)
- Very rarely they take Arabian Sea ridge (Gaja in 2018) in under steering.
- While under-steered systems are choked and does not intensify a lot (Gaja was an exception due to nil wind shear).
- Cyclone Nivar is an upper steered system through the ridge extending from Pacific side.
SOURCES : thetamilweatherman.com
FAVORABLE PARAMETERS FOR CYCLONE TO INTENSIFY
- Wind Shear – Ideal wind shear of 10-15 knots and shows decreasing trend.
- No dry air intrusion.
- Sea Surface Temp is warming up and ideal
- It is very close to coast – Time is short
- Very fast movement
- Visakhapatnam and East Godavari districts are also likely to receive light to moderate rains.
- Widespread heavy rains from Delta to Chennai and extreme rains to Delta are expected.
- Fishermen from Tamil Nadu, Pondy and Andhra are not requested to venture into sea from today.
- Strangely the cyclone which try to avoid Sri Lanka and move towards TN coast are all with Coincidence starts with letter “N” – Nisha in 2008, Nilam in 2012 .
- India Meteorological Department made presentation on the present situation and mentioned that the status is being shared with the concerned State Governments.
SOURCES: IE | PIB | DownToEarth | Cyclone Nivar : Explained | UPSC