TROPICAL CYCLONE ‘TAUKTEA’

Recent Context:

Recently Cyclone Tauktae originating in the Arabian is likely to intensify into a severe cyclonic storm and intensify further; likely to move north-northwestwards and reach Gujarat coast on the morning of May 18 and cross Gujarat coast between Porbandar and Naliya around the same afternoon.

Introduction:

The name “Tauktae” has been given by Myanmar, which means “gecko”, meaning a highly vocal lizard in Burmese. This is going to be the first cyclonic storm of this year along the Indian coast. Tropical cyclones are officially named by one of its warning centres spread across the globe under the aegis of the World Meteorological Organization (WMO).

Key Updates:

  1. As cyclone Tauktae intensifies in coming 12 hours Kerala is going to witness heavy rain. IMD had issued a warning of heavy rainfall earlier on the day given the low depression formed over Lakshadweep in the Arabian Sea.
  2. Tauktae, once formed, is likely to intensify into a ‘very severe cyclonic storm’ with wind speed of 150 to 160 kmph gusting to 175 kmph on May 17, according to the latest forecast by the India Meteorological Department (IMD).
  3. The depression over Lakshadweep area has moved north-north-eastwards with a speed of about 19 kmph and is now centred over Lakshadweep about 30 km south southwest of Amini Divi, 320 km west-southwest of Kannur (Kerala), 1120 km south southeast of Veraval (Gujarat) at about 11.30 am on May 14.
  4. It is very likely to intensify into a cyclonic storm during the next 24 hours and is also expected to intensify further during the subsequent 24 hours. Tauktae is likely to move north north-eastwards initially for some more time and then move north-north westwards and reach the Gujarat coast by May 18 morning.
  5. Cyclone Tauktae can be among the ‘strongest’ on India’s west coast in 2 decades.
  6. The low pressure area over the Arabian Sea near Lakshwadeep has intensified into a deep depression, said the Indian Meteorological Department which will further intensify into a cyclonic storm.
  7. IMD, in a bulletin on Friday, said the depression over Lakshadweep moved north-northeastwards with a speed of 19 kilometre per hour in the past six hours. It lay centred over Lakshwadeep area and the adjoining southeast and east-central Arabian Sea at 2.30 pm, the IMD went on to add.
  8. This cyclonic disturbance intensified into a deep depression about 50 km north-northwest of Amini Divi, which is 310 km west-southwest of Kannur in Kerala.

Background:

Tropical cyclones form only over warm ocean waters near the equator.To form a cyclone, warm, moist air over the ocean rises upward from near the surface. As this air moves up and away from the ocean surface, it leaves is less air near the surface. So basically as the warm air rises, it causes an area of lower air pressure below. Air from surrounding areas with higher air pressure pushes in to the low pressure area. Then this new “cool” air becomes warm and moist and rises, too. And the cycle continues.

When the winds in the rotating storm reach 39 mph (63 kmph), the storm is called a “tropical storm”. And when the wind speeds reach 74 mph (119 kmph), the storm is officially a “tropical cyclone” or hurricane. Tropical cyclones usually weaken when they hit land, because they are no longer being “fed” by the energy from the warm ocean waters. However, they often move far inland, dumping many centimeters of rain and causing lots of wind damage before they die out completely.

  • Cyclones are rapid inward air circulation around a low-pressure area. The air circulates in an anticlockwise direction in the Northern hemisphere and clockwise in the Southern hemisphere.
  • Cyclones are usually accompanied by violent storms and bad weather
  • The word Cyclone is derived from the Greek word Cyclos meaning the coils of a snake. It was coined by Henry Peddington because the tropical storms in the Bay of Bengal and the Arabian Sea appear like coiled serpents of the sea.

Classification

There are two types of cyclones:

  • Tropical cyclones; and
  • Extra Tropical cyclones (also called Temperate cyclones or middle latitude cyclones or Frontal cyclones or Wave Cyclones).

The World Meteorological Organisation uses the term ‘Tropical Cyclone’ to cover weather systems in which winds exceed ‘Gale Force’ (minimum of 63 km per hour).

Tropical cyclones develop in the region between the Tropics of Capricorn and Cancer. They are large-scale weather systems developing over tropical or subtropical waters, where they get organized into surface wind circulation.

Extra tropical cyclones occur in temperate zones and high latitude regions, though they are known to originate in the Polar Regions.

Features of Tropical Cyclones

  • Tropical cyclones are violent storms that originate over oceans in tropical areas and move over to the coastal areas bringing about large scale destruction caused by violent winds, very heavy rainfall and storm surges.
  • Tropical Cyclones are one of the most devastating natural calamities in the world.
  • Tropical cyclones originate and intensify over warm tropical oceans. The conditions favourable for the formation and intensification of tropical storms are:
  • Large sea surface with temperature higher than 27° C.
  • Presence of the Coriolis force.
  • Small variations in the vertical wind speed.
  • A pre-existing weak low- pressure area or low-level-cyclonic circulation.
  • Upper divergence above the sea level system.

Stages of Formation: Tropical Cyclones

The development cycle of tropical cyclones may be divided into three stages:

Formation and Initial Development Stage

  • The formation and initial development of a cyclonic storm depends upon the transfer of water vapour and heat from the warm ocean to the overlying air, primarily by evaporation from the sea surface.It encourages formation of massive vertical cumulus clouds due to convection with condensation of rising air above the ocean surface.

Mature Stage

  • When a tropical storm intensifies, the air rises in vigorous thunderstorms and tends to spread out horizontally at the tropopause level. Once air spreads out, a positive pressure at high levels is produced, which accelerates the downward motion of air due to convection.
  • With the inducement of subsidence, air warms up by compression and a warm ‘Eye’ (Low pressure centre) is generated. The main physical feature of a mature tropical cyclone in the Indian Ocean is a concentric pattern of highly turbulent giant cumulus thundercloud bands.

Modification and Decay

  1. A tropical cyclone begins to weaken in terms of its central low pressure, internal warmth and extremely high speeds, as soon as its source of warm moist air begins to ebb or is abruptly cut off.
  2. This happens after its landfall or when it passes over cold waters.

Anticyclones

An anticyclone is the opposite of a cyclone i.e. it has an outward-spiraling air circulation around a high pressure centre. An anticyclone’s winds rotate clockwise in the Northern Hemisphere around a center of high pressure. In anticyclones, air comes in from above and sinks to the ground. High pressure centers generally have fair weather.

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