Cyclone ‘Ockhi’ heads for Lakshadweep, to intensify further

In news

The India Met Department (IMD) has officially stated that the deep depression 170 km to the south-east of Kanyakumari has intensified into a named cyclone, Ockhi.

It is moving towards the Lakshadweep Islands and would intensify into a severe cyclone in the process. The system is located 700 km east-south-east of Minicoy in Lakshadweep.

Further Intensification

  • The IMD said Ockhi would stay as a severe cyclonic storm out in the East-Central Arabian Sea till early morning on Sunday, up to which forecasts are available.
  • Earlier, the US Navy’s Joint Typhoon Warning Centre (JTWC) had put out an alert saying that the system could intensify further to become a severe cyclonic storm.
  • It further said the storm could re-curve towards the Mumbai-Gujarat region on the West Coast, after being influenced by an incoming western disturbance from the opposite direction.
  • But it would weaken as it approaches the coast. The IMD has not taken a call on the behaviour of the storm, its strength or intensity beyond December 3.

Basic Gyan

Cyclone

Cyclones are one of nature’s responses when there is a meeting between hot and cold air currents. These are circular shaped rotating storms which have huge diameters ranging from 150 to 1000 kilometres. Due to this high speed rotation, an intense low pressure is formed at the centre; this is called the “Eye of the storm”. Cyclones of high intensity are caused mostly in tropical areas. Cyclones are known to cause great devastation to life as well as property

Characteristics

  • Sustained wind speeds of more than 120 km/h surrounding the centre

  • Very low atmospheric pressure system

  • Increase sea level, storm surge and wave heights

  • Eye diameters are 40 km on average

  • Eye wall marks the strongest wind and heaviest rainfall

  • Spiral rain band clouds that extend over 1000 km from the eye

How do cyclones form?

First of all, as all matter has weight, so does air. Due to this weight it exerts pressure. This pressure may be different at different temperatures. This is due to the different densities possessed by air at different temperatures. Cold air has higher density and hot air has lower density.

The air flow pattern as we go from the North to South Pole varies according  This occurs because of the rotation of the earth. So when there is a low pressure area in the sub-tropical region, hot air and cold
air rush in to fill this low pressure. Just like when you burst a balloon. The pressure outside the balloon is lower than the pressure inside it therefore the air rushes outward to balance the pressure.

Therefore the hot and cold collide at this low pressure at certain angles. Now, the cold air goes downward and the hot air rises since they have different densities.

These air flows since coming in at an angle tend to cause a rotatory motion arising from downward motion of cold
air and upward motion of hot air. Since the direction of attack is opposite in the northern and southern hemispheres,
the direction of rotation will be opposite.

There is anti-clockwise rotation in the northern hemisphere and clockwise rotation in the southern hemisphere. In the centre of this rotating air mass is an intensely low pressure area known as the “Eye” of  the storm. The low pressure present at the eye of the storm tends to get filled by the rotating air mass.

This causes the lateral motion of the cyclone. Hence the “Eye” of the storm continuously moves forward. Therefore the cyclone consists of both rotatory and lateral motion. The physics of the motion the cyclone can be calculated using vector notations.
As the air mass rotates, even the surrounding air is pulled which makes the cyclone grow in diameter.

What is the difference between a hurricane, a cyclone, and a typhoon?

The only difference between a hurricane, a cyclone, and a typhoon is the location where the storm occurs.

Hurricanes, cyclones, and typhoons are all the same weather phenomenon; we just use different names for these storms in different places. In the Atlantic and Northeast Pacific, the term “hurricane” is used. The same type of disturbance in the Northwest Pacific is called a “typhoon” and “cyclones” occur in the South Pacific and Indian Ocean.

The ingredients for these storms include a pre-existing weather disturbance, warm tropical oceans, moisture, and relatively light winds. If the right conditions persist long enough, they can combine to produce the violent winds, incredible waves, torrential rains, and floods we associate with this phenomenon.

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