Hurricanes 

23 Aug 2023 Hurricanes 

This article covers “Daily Current Affairs” and the topic details “Hurricanes”. The topic “Hurricanes” has relevance in the “Geography” section of the UPSC CSE exam.

For Prelims:

What are Tropical Cyclones and their types? 

For Mains:

GS1: Geography

Why in the news?

In an unusual event, Hurricane Hilary is on track to be the initial tropical storm to make landfall in Southern California in over 80 years.

Tropical Cyclones

• A tropical cyclone is a swiftly rotating storm system identified by its central region of low pressure, enclosed low-level atmospheric circulation, powerful winds, and an arrangement of thunderstorms resulting in significant rainfall and abrupt gusts.

Nomenclature 

The nomenclature assigned to these cyclones varies based on their location and strength, encompassing terms such as hurricane and typhoon, as well as tropical storm, cyclonic storm, tropical depression, and simply cyclone.

• The classification of “hurricane” applies to robust tropical cyclones emerging in the Atlantic Ocean or the northeastern Pacific Ocean.
• The “typhoon” characterises similar storms in the northwestern Pacific Ocean. 
• In the Indian Ocean, South Pacific, and occasionally the South Atlantic, these weather phenomena are referred to as “tropical cyclones”.

Hurricane

• A hurricane, also known as a tropical cyclone, is a circular low-pressure weather system characterized by well-organized thunderstorms and the absence of fronts, which are boundaries separating different-density air masses. 
• The intensity of a hurricane is gauged using the Saffir-Simpson Hurricane Wind Scale, which ranges from 1 to 5 and is determined by the hurricane’s peak sustained winds. A higher category on the scale signifies a greater potential for causing damage to property.
• Originating primarily in the Atlantic basin, encompassing the Atlantic Ocean, Caribbean Sea, Gulf of Mexico, as well as occasionally in the eastern North Pacific Ocean and central North Pacific Ocean, hurricanes are identified using a six-year cyclic list of names. This list is curated and updated by the World Meteorological Organization.
• The timeframe known as “Hurricane Season” spans from June 1 to November 30. 

Parts of a Hurricane

• Eye: The centre of the storm is characterised by calm winds and sometimes clear skies.
• Eye Wall: A ring of intense thunderstorms surrounding the eye, with the strongest winds and heaviest rainfall.
• Rain Bands: Cloudy and rainy bands extending from the eye wall, often containing thunderstorms and occasionally tornadoes.

Stages of Hurricane Formation

• Tropical Disturbance: An area with developing rain clouds over warm ocean waters.
• Tropical Depression: A region of rotating thunderstorms with winds up to 62 km/hr (38 mph).
• Tropical Storm: Occurs when wind speeds reach 63 km/hr (39 mph).
• Hurricane: Achieved when wind speeds reach 119 km/hr (74 mph).

Necessary Conditions for formation of Hurricanes

• An existing weather disruption: Frequently, a hurricane initiates as a tropical wave.

• Elevated temperature in the ocean: The storm derives its energy from water that is a minimum of 26.5 degrees Celsius in temperature, extending 50 meters deep.

• Occurrences of thunderstorms: Thunderstorms transform the warmth from the ocean into the energy source for the hurricane.

• Limited wind shear: Significant variations in wind speed and direction in close proximity to the storm can result in its attenuation.

More about the news

• According to the latest public advisory released by the US National Hurricane Center, the storm was in close proximity to the western coast of Baja California.
• This occurrence is remarkable since the sole tropical storm accompanied by hurricane-force winds, thought to have impacted Southern California, occurred in October 1858, causing significant impact to San Diego.

Why is this occurrence remarkable? 

The Pacific coast’s rarity of tropical storms and hurricanes is due to unique ocean features. 

• Temperature Disparity: East vs. West: 

• • • The US east coast experiences warm hurricane-season temperatures, but the west coast has colder waters. 
    • Unlike the Atlantic’s warm equatorial waters moving north via the Gulf Stream, the Pacific’s cold currents bring cooler water from higher latitudes, making hurricanes unlikely.

• Role of Vertical Wind Shear: 

• • • As hurricanes can extend 16 km high, wind shear disrupts their structure, limits upward air movement, and displaces warm air above the storm’s eye. 
    • Strong wind shear in the eastern Pacific versus the Gulf of Mexico means fewer western coast hurricanes.

• Impact of Wind Steering Patterns: 

• • Trade winds guide hurricanes eastward, away from the western coast. Pacific-originating hurricanes often head west-northwest due to these winds, taking them away from the coast.

Role of Climate Change

• Scientific Studies: 

• • • Scientists predicted that climate change would not only increase the occurrence of such hurricanes but also intensify them. 
    • A recent study published in the journal American Meteorological Society, indicated that major hurricane landfalls in the eastern Pacific could become up to 30% more frequent if global temperatures rise by at least 2 degrees Celsius.

• Ocean’s Heat Absorption and Temperature Rise: 

• • • Oceans have absorbed 90% of the extra heat generated by greenhouse gas emissions recently. 
    • Consequently, the global mean sea surface temperature has risen by nearly 0.9 degrees Celsius since 1850 and around 0.6 degrees Celsius in the last four decades.

• Amplification of Extreme Weather Events: 

• • • Elevated sea surface temperatures lead to marine heatwaves, extreme weather events that can heighten the intensity of storms like hurricanes and tropical cyclones. 
    • Warmer temperatures accelerate evaporation and heat transfer from oceans to the air. 
    • Storms crossing warm oceans collect more water vapor and heat, resulting in stronger winds, heavier rainfall, and increased flooding upon landfall.

• Role of El Nino: 

• • The situation has been exacerbated by the occurrence of El Niño, the first in seven years. El Niño weakens vertical wind shear in the eastern Pacific, permitting more hurricanes in the area. 
  • El Niño refers to abnormal warming of surface waters in the equatorial Pacific Ocean, known to elevate the likelihood of temperature records being broken and triggering extreme heat both on land and in the ocean.

Sources: Hurricane Hilary: Why are west coast hurricanes so unprecedented? (indianexpress.com)

Yojna daily current affairs eng med 23rd August 2023

Q1. With reference to tropical cyclones, consider the following statements: 

1. “Hurricane” refers to strong tropical cyclones from the Atlantic Ocean, while the term “typhoon” is used for storms in the northwestern Pacific Ocean.
2. The “Hurricane Season” generally spans from June 1 to November 30.
3. The intensity of a hurricane is measured using the Fujita scale, ranging from 1 to 5.

Which of the statements given above is/are NOT correct?

(a) 1 and 2 only

(b) 2 only

(c) 1 and 3 only 

(d) None 

Answer: (c) 

Q2. Consider the following: 

1. The Eye is the central region of a hurricane,  consisting of intense thunderstorms and hosting the strongest winds and heaviest rainfall. 
2. The Eye Wall is a circular area surrounding the eye, known for calm winds and sometimes clear skies.
3. Thunderstorms play a role in converting ocean warmth into the energy that fuels hurricanes.
4. Limited wind shear, involving significant differences in wind speed and direction close to the storm, can weaken the storm’s intensity.

How many of the abovementioned statements are correct ?

(a) Only one 

(b) Only two 

(c) Only three 

(d) All Four 

Answer: (b)

Q3. Discuss the stages of formation of a hurricane, highlighting the conditions necessary for its development and the role of climate change in influencing the frequency and intensity of hurricanes.

Gaurav N