Hurricane, typhoon, cyclone: what is the difference?

These storms all form over warm tropical waters and all can be deadly – but their origin determines their name.

Hurricanes, typhoons and cyclones may have a lot more in common than you think. They are all intense areas of low pressure and form over warm tropical waters. They can ultimately unleash deadly winds and heavy rainfall, but the defining factor for naming these storms that originate in the tropics is essentially down to where in the world they form.

Hurricanes are classed as such when a low-pressure system intensifies so that winds of 74mph (119km/h) become sustained around an area of low pressure in the North Atlantic, central North Pacific or eastern North Pacific. The power of a hurricane is rated on the Saffir-Simpson wind scale and has five categories, category 5 being the most intense. The same storm would be called a typhoon if it were to form in the north-west Pacific and would then adhere to a slightly different intensity scale to that of hurricanes. A super-typhoon would be classed as a severe hurricane on the Saffir-Simpson scale (equivalent to a category 3 hurricane) for example. The generic term cyclone or tropical cyclone is used for the South Pacific and Indian Ocean and also follows slightly different intensity scales, depending on the authorities monitoring the storm.

8. Reading. Read the text and give headings to part 1 and part 2.

 

Tropical cyclones

Part I.

Hurricanes and typhoons are the same weather phenomenon: tropical cyclones. A tropical cyclone is a generic term used by meteorologists to describe a rotating, organized system of clouds and thunderstorms that originates over tropical or subtropical waters and has closed, low-level circulation.

The weakest tropical cyclones are called tropical depressions. If a depression intensifies such that its maximum sustained winds reach 39 miles per hour, the tropical cyclone becomes a tropical storm. Once a tropical cyclone reaches maximum sustained winds of 74 miles per hour or higher, it is then classified as a hurricane, typhoon, or tropical cyclone, depending upon where the storm originates in the world. In the North Atlantic, central North Pacific, and eastern North Pacific, the term hurricane is used. The same type of disturbance in the Northwest Pacific is called a typhoon. Meanwhile, in the South Pacific and Indian Ocean, the generic term tropical cyclone is used, regardless of the strength of the wind associated with the weather system.

The ingredients for tropical cyclones 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, large waves, torrential rains, and floods we associate with this phenomenon. At times, when a weather system does not meet all of these conditions, but is forecast to bring tropical storm or hurricane force winds to land in the next day or two, it is called a potential tropical cyclone in the Atlantic basin and the central and eastern North Pacific basins.

Typhoon paths follow three general directions.

Straight track (or straight runner). A general westward path affects the Philippines, southern China, Taiwan, and Vietnam.

A parabolic recurving track. Storms recurving affect eastern Philippines, eastern China, Taiwan, Korea, Japan, and the Russian Far East.

Northward track. From point of origin, the storm follows a northerly direction, only affecting small islands.

According to the World Meteorological Organization recommendations, tropical cyclones are classified by the maximum sustained wind speeds near the centre. Hurricanes are categorized 1 to 5 according to the Saffir-Simpson scale, which is based on wind speed.

In the Atlantic, hurricane season officially runs from June 1 to November 30. Ninety-seven percent of tropical cyclone activity occurs during this time period. However, there is nothing magical about these dates. Hurricanes can and do occur outside of this six month period.

 

Part II.

Changes to the uppermost layer of Earth's oceans due to rising temperatures are likely causing an increase in intense Pacific Ocean typhoons, suggesting strong typhoons may occur more frequently than scientists project in the coming decades, according to new research.

The surface layer of the ocean, known as the ocean mixed layer, is approximately 200 meters (656 feet) deep on average. This layer is constantly exchanging gases with the atmosphere and experiencing mixing caused by winds, heat transfer, evaporation and changes in salinity.

Understanding how climate variability within a climate system contributes to the observed increase in the proportion of intense typhoons helps scientists understand the hazards posed by devastating storms in the north Pacific Ocean, especially as the ocean and atmosphere continue to warm, according to the researchers.

Scientists have been studying the changes in typhoon intensity over the past several decades, but the reasons for the increase in typhoon intensity is still a subject of controversy, according to Wu.

In the new study, Wu and his team examined the contributions of various factors controlling typhoon intensity change, such as sea surface temperatures, the temperature of outward flowing air and water, ocean mixed layer depth, and vertical wind shear, as well as shifts in the tropical cyclone tracks. They used computer simulations to compare each factor with observed tropical cyclone intensities in the western North Pacific basin for each year from 1980-2015.

After quantifying the contribution of each environmental factor to tropical cyclone intensity, they determined that the increase in the proportion of intense typhoons was largely due to a deepening of the ocean mixed layer. This deepening is in turn caused by variations in ocean and atmospheric conditions.

The deepening of the ocean mixed layer is just one of many substantial changes to atmospheric and ocean circulations that have occurred in the western North Pacific since 2000 as a result of climate change, according to the researchers. Deepening of the ocean mixed layer is likely the major reason for the sudden increase in the proportion of intense typhoons in 2001, Wu said.

Because previous studies have not accounted for ocean mixed layer depth in their projections, the authors conclude that future typhoons in the North Pacific may be increasingly intense, and to an even greater degree than previously thought.

 

Comprehension check:

A) Answer the following questions on the text:

1. What are main characteristics of a tropical cyclone?

2. What is the tropical cyclone classification based on?

3. What are the ingredients for tropical cyclones occurrence?

4. When is the hurricane season?

5. What causes the typhoon intensity change according to Wu?

B) Are the statements true or false?

1. Hurricanes and typhoons are different weather phenomena.

2. Typhoon paths follow three general directions.

3. The weakest tropical cyclones are called typhoons.

4. Hurricanes can and do occur outside of the hurricane season period.

5. Future typhoons in the North Pacific may be increasingly intense, and to an even greater degree than previously thought.

 

9. Grammar revision. Make Participle I or Participle II of the verbs in brackets. Translate sentences into Russian.

1. ……….. (to know) also as cyclones and typhoons in other parts of the world, hurricanes cause high winds, flooding, heavy rain, and storm surges (high tidal waves).

2. Since 2002, there have been a number of initiatives and accomplishments (to have) ……… a significant impact on the World Weather Watch.

3. The current systems (to utilize) ………. the Global Positioning System, have resulted in continued improvement in data quality and ease of operation.

4. The reason for the dramatic reduction has been effective warnings and timely evacuation from coastal areas (to inundate) ……….. by storm surge.

5. Tropical cyclones are ideal subjects for study from (to instrument) ……..  aircraft.

6. This descending air reduces water vapor and cloud formation (to result in) ……… light winds and stable weather.

7. Since 1959 meteorological satellites have provided an overview of the atmosphere’s cloud patterns, (to serve) ……… among other things as an early warning and detection systems for hurricanes, typhoons, and tropical cyclones.

8. The World Weather Watch, (to organize) ……….. by the World Meteorological Organization, collects and disseminates information on a global basis.

9.The Beaufort wind force scale is an empirical measure that relates the mean wind speed to conditions (to observe) ……….. at sea or on land.

10. Scientists have used 3D printing to create (to vary) ………. shapes of snowflakes and study how their individual structure affects their behaviour.

10. Skills development. Render the text into English.