Cyclone #Amphan: All you need to know about Super Cyclone Amphan, origin, impact, and aftermath

Bhavik Bamania
Bhavik Bamania
 -  7 mins read
Cyclone #Amphan: All you need to know about Super Cyclone Amphan, origin, impact, and aftermath

How the super cyclone like Amphan originates? What threat does it possess to the Indian landmass? Here is the detailed article on Cyclone Amphan and how a cyclone originates.

Every year, as the calendar flips to April, the discussions and anticipations regard cyclogenesis because to take place across the common mass, and the people like me who observes metrological events closely, start to check the daily happenings, though we have a very different phase and a year this time, but not for the weather, and amidst the crisis of #COVID19, the Super Cyclone Amphan (pronounced UM-PUN) has appeared as a major threat to the Indian coastline. It is the only 2nd Super Cyclone in the Bay of Bengal after the devastating Super Cyclone of Odisha of 1999 and has the full potential to make a rewind of that scarce once again.

Introduction cum Metrological History

There must be something very interesting or something really important to make me thinking about writing an article during the life of Cyclone, rather than writing a case study after the destruction. The Super Cyclone Amphan is one of such kind, the cyclone was named after the name suggested by Thailand, the naming of Cyclone is a global thing which is done across the globe, and I will cover it in the upcoming portion.

The ongoing journey starts with a Low-Pressure Area around May 13th, in the Andaman Sea, the things went at berserk when it becomes a Cyclonic storm on the evening of 17th May and within the next 12 hours, it turned into a Super Cyclone, which no one has imagined and even at the moment, when I am writing this, the system is traveling in utmost favorable conditions. 

Types of Cyclones

There you must be thinking about what makes a favorable condition for the cyclogenesis? Well, let’s discuss the category of cyclone before get deep into this. I feel it won’t be easy to understand without knows some basics.

Well, there are number of scales, the most widely known is Saffir-Simpson Hurricane Wind Scale, primally used in American Continents, but when we talk about India the IMD classified the storm category into 7 parts. These types are listed in the below image

Classification of Cyclones

Since the Super Cyclone Amphan has the gust of 240–250 km/h with the sustained winds up to 275 km/h the system has been categorized as Super Cyclone.

Trajectory or the path of Super Cyclone Amphan

Presently it is moving nearly in a northward direction, and it is in the process of recurve, with a speed of 15 km/h and situated 640 km near south of Paradip, 800 km south-southwest of Digha. It will make the landfall by 20th May, afternoon, or evening near Sunderbans between Digha & Hatiya Islands of Bangladesh.

Since the coast of West Bengal is shallow and is a basin area, the impact would be catastrophic as it will trigger extensive damage to the structures, trees, it is well-advised to evacuate the adjoining area well before. I will brief the impacts in the later portion.

Affected Areas

The Super Cyclone going to crush the shallow coastline of West Bengal & Bangladesh but owing to its mammoth size it will be going to affect Odisha, West Bengal, Sikkim, and the entire North Eastern States particularly Assam & Arunachal Pradesh. However, I am going to post it on my twitter handle and Facebook about the further intensification and updates over this.

Features of Amphan

This is not a relevant section but considering the characteristics and the expected havoc, it is going to create it is important to emphasize why I am emphasizing the features and perhaps the reason behind writing this article.

The Super Cyclone Amphan has a wind speed of 230–240 km/h with the gust sustained up to 275 km/h, it has the 2nd lowest low pressure at its center of 918 hPa (the lowest is Super Cyclone of 1999 with 912 hPa), the lowest causes the more destructive cyclones. It has an expansive system with the cloud tops of 1111 km with super-dense, deep, and symmetrical central convection. The height is about 15 km with the radius of the eye is of mammoth 120 km, scary? Yes, it is, it might be the largest cyclone in dimension to ever made, only further study will tell about such trivia. The thing which is for sure now is that it can cause tidal wave up to 4–6 meters and since it is going to hit the delta things gets messier, that it might dump the saline water up to 25–30 km inland with the river and can cause massive inundation.

How the naming of Cyclones is done?

As I said above, the naming of Cyclone is a global procedure, the naming is done for the primary reason of naming is to able to report in the media, the technical terms are alphanumeric which is not easy to communicate and remember for the instance the name of Super Cyclone Amphan is Tropical Super Cyclone 01B.

The naming in North Indian Ocean ie., the Arabian Sea and the Bay of Bengal is done by the group of adjoining countries and the name of the suggested list is used.

An satellite image of the eye of Super Cyclone 1999

Cyclone: A Multi-Hazard

Whenever a cyclone hits it brings three-dimensional damage, which are

  • Tidal wave: Tidal wave caused by the Cyclone bring debris, makes soil saline, inundation, and the damage to the standing crops and the structure specifically the kutcha houses.
  • Heavy Rainfall: Any Cyclone can trigger massive rainfall, cloud burst with gust, and the cyclones with the intensity the same as Amphan can trigger massive rainfall. For instance, Puri recorded 54 cm in 24 hours when the Odisha Super Cyclone hit the Puri coast.
  • Strong Winds: The third factor which contributes to the damage is the strong winds rushing from the sea, the strong winds with the intensification makes the more adverse situation, in case of Amphan the North and South 24 Parganas are going to see the winds up to 165 km gusting 195 km and Kolkata with the wind speed of 110–120 km gusting 135 km

Parameters for Cyclogenesis

After all this, you might be wondering how these cyclones originate. What makes Amphan so powerful. There are 6 major factors behind any cyclogenesis, from the list of six the first three parameters are them are thermodynamical parameters and the last three are dynamic parameters.

  1. Sea Surface Temperature or simply SST and Ocean Thermal Energy are the most important parameter if the temperature of Sea Surface is more than 26° then the situations become favorable for cyclogenesis, at present the Bay of Bengal is heating up at 35° and thus we have got Super Cyclone Amphan.
  2. Higher Relative Humidity (at least 60% RH) in Tropospheric Level, this triggers to enhance of deep convective activities.
  3. Instability in the Atmosphere, help moist air to go up more quickly and evaporation takes place more quickly.
  4. Coralis force, the force causes because of the rotation of the earth. This cause deflection of winds towards the right direction in the Northern Hemisphere and to the left in the Southern Hemisphere. The cyclogenesis needs minimum Coralis force found in North of 5°.
  5. High Rotating power of the atmosphere in a lower Atmosphere. For, cyclogenesis it needs high rotating power in the lower troposphere which leads to the rotation of clouds.
  6. The cyclogenesis needs lower vertical wind shear, that is the winds should be lower side at the upper level to organize the clouds.

Apart from the above-mentioned factors like Madden-Jullien Oscillation (MJO), Calvin Wave are also important in the process of cyclogenesis.

And all the above-mentioned parameters are meeting as result of Super Cyclone Amphan

The effect over the Monsoon

The Super Cyclone Amphan caused the arrival of Monsoon over Andaman & Nicobar Islands but now the cyclone is so powerful that it will dry up all the moisture from the sea and thus will weak the surge of Monsoon current and thus the situation will put a hiatus over the Monsoon for at least 2 weeks, thus, I am also modifying my prediction, I am also expecting it to arrive around 1st June with (+/-4 days), earlier I was expecting an early onset over Kerala.

Aftermath

The aftermath is to be calculated after dissipating of the Cyclone but on the metrological term, it will shift the wind pattern to north-western in the landmass and thus these dry winds from the north-west direction will cause heat-wave conditions over the plains.

Conclusion

Owing to the situation, and conditions the sea will be phenomenal, very rough and since it will be going to hit the delta region it will going to cause catastrophic impact much like Cyclone Nargis and even much more since it has high intensity compared to Cyclone Nargis, it is a need of the hour to take the advisory very seriously and carried out the evacuation.

(Based on the personal knowledge and the session of DGM of IMD Dr. M. Mohapatra’s minutes of live session. The information regarding the current status of Super Cyclone Amphan is attributed to IMD)