From origin, impact, to aftermath all you need to know about Tropical Cyclones life cycle.

Cyclone is not a new topic upon which I am discussing, I have been discussing via various mediums a lot over this fascinating topic for the last 15 odd years but I started to write extensively in the last 5 years or so and that too first on my social media handles and as the year passed on I tried to reach out to as many audiences I could and thus I got the opportunity to discuss this phenomenon last year when the Cyclone Amphan hit the West Bengal Coast and before that DGM of Indian Meteorological Department had an interactive session over Facebook (bear with me if you lots of copy-paste material from this article).

But the article which I have mentioned above was more specific about Cyclone Amphan, and more specifically on the discussion we had with Dr. Mrithyunjay Mohapatra, though it has some elementary information regarding cyclogenesis, despite that, I felt I should write a separate article which has general information regarding cyclone and to aware the general masses. The core idea behind this article is to make people more aware and make capable enough to bear with such phenomenal circumstances.

Why cyclones originate in the North Indian Ocean?

This must be the first question that comes to your mind as you read about cyclones affecting the Indian Coast? Well, the answer is very simple as the summer arrives to be precise from April to October. The Northern Hemisphere starts to heat up and as a result, it leads to increase sea-surface temperature (SST) however, they can form anytime and anywhere but this is the most important factor after a favorable SST other factors kick in, well that’s one of the primary reason, another reason is the cyclones are low-pressure systems which forms on either side of the equator in between 10° and 20° latitude, they do not pr I say they rarely form near the equator or over the equator, because Coriolis force remains zero at the equator and it increases as the latitude increases, the Coriolis force at 5° is the ideal force for the formation of any tropical system. Now, you must be thinking what the heck is this Coriolis force? Well, the answer is simple, the rotation of the earth about its axis affects the direction of the wind. This force is called the Coriolis force.

Along with these factors, the Northern Indian Ocean provides slow winds, particularly in the Bay of Bengal, the slowness of winds allows the organization of clouds around the low-pressure area, and the other supporting helps them in their intensification. Hence, the location of India proving a hotbed for cyclogenesis.

How cyclones originate?

Now, we know why the Northern Indian Ocean proved to be a favorable area for cyclogenesis now the next in the cue is how these cyclones originate what are the parameters of cyclogenesis. There are 6 major factors behind any cyclogenesis, primarily divided into two viz, thermodynamical parameters, and dynamic parameters. So, let’s understand these two parameters shall we?

Thermodynamical Parameters

1. Sea Surface Temperature or simply SST and Ocean Thermal Energy is the most important parameter if the temperature of the Sea Surface is more than 26° then the situations become favorable for cyclogenesis. Here, remember the golden rule, ”higher the SST higher is the possibility of forming cyclones and that too a stronger cyclone if it roams more in warm water.”
2. Higher Relative Humidity (at least 60% RH) in Tropospheric Level, triggers the enhancement of deep convective activities (basically cyclones or any Low-Pressure Area [LPA]).
3. Instability in the Atmosphere, help moist air to go up more quickly and evaporation takes place more quickly. During the rainy season ie., the Monsoon, the atmosphere is quite stable, but pre and post-monsoon it is highly unstable that’s why cyclone forms before and after the monsoon and rarely during the monsoon season.

Dynamic Parameters

1. Coralis force, the force causes because of the rotation of the earth. This causes 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°.
2. High Rotating power of the atmosphere in a lower Atmosphere. For, cyclogenesis needs high rotating power in the lower troposphere which leads to the rotation of clouds.
3. The cyclogenesis needs lower vertical wind shear, that is the winds should be lower side at the upper level to organize the clouds. Here also applies the Golden rule which is useful even estimating the strength of a storm on many occurence it is the wind shear that comes to the rescue from the wrath of a cyclone, ”lower the wind shear, stronger the storm.”

Apart from the above-mentioned factors like Madden-Jullien Oscillation (MJO), Calvin Wave, Rossby Waves are also important in the process of cyclogenesis, but that might make this article very boring and I guess too technical for a layman to understand, therefore let’s leave them out for the moment.

Types of Cyclones

Now, we know the factors and the reasons behind the formation of cyclones, now we should have some scale to differentiate the types of cyclones isn’t it? Well, there are numbers of scales, the most widely known is Saffir-Simpson Hurricane Wind Scale, primarily 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

How the naming of Cyclones is done?

We humans have the habit of naming any newborn things in order to recall them or to identify them. Hence, we also name the cyclones as well, the naming of Cyclone is a global procedure, the naming is done so that we can able to report in the media and for easy identification, the technical terms are alphanumeric which is not easy to communicate and remember for the instance the name of Super Cyclone Amphan was Tropical Super Cyclone 01B.

The naming in the 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. Here is the current name list of cyclones with the name of countries who have given the names for the list.

Cyclone: A Multi-Hazard

This is maybe the most important section and therefore, I advise you to heed utmost attention while reading this out. I am planning to write a detailed article on this topic particularly but for the moment let’s keep it short and sweet and most important simple (too much information in one go often leads to mind is equal to blown).

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, it completely depends on the intensity of the cyclone. 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 intensification make the more adverse situation.

The effect over the Monsoon

This is the most important question especially when the cyclone forms during the pre-monsoon phase or the onsetting phase. Generally, the progress of the Monsoon either gets accelerated or halted by these cyclones, basically, it depends on the timing and the location of the cyclone and more important the trajectory or the path it follows.

If they follow the path in which the monsoon current is moving it triggers the early onset and rapid movement of the monsoon flow, but if they go against the direction of the monsoon flow they put the hiatus on the monsoon flow. However, the intensity of the cyclone also matters a lot here, if the cyclone is very powerful like Amphan, then it dries up all the moisture from the sea and thus weakens the surge of Monsoon current, Post-cyclones, it has been seen that cyclones mostly followed by a brief hiatus in the surge of the Monsoon.

Aftermath

The aftermath is to be calculated after dissipating of the Cyclone ie., once the cyclone has gone and dissolved but in the metrological term, the wind pattern often gets changes leading to the enhancement of rains or heat depends on the direction and the origin of the cyclone, as it tends to drag everything within them.

Conclusion

Owing to the situation which they cause, the conditions in the sea become phenomenal, very rough and they are a multi-hazard phenomenon, therefore, it is a must-to-do to take the advisory very seriously issued by the meteorological department and carried out the evacuation and cooperate with the rescue teams. Need not panic if it makes landfall in your area just need to follow the guidelines issued by the authority.

I hope that I have been able to provide crucial information regarding cyclones and it might help the readers on the closing note I would urge readers to share this article to make people aware and help me to spread the word for a better cause.