Tropical Cyclones, Hurricanes and Typhoons

The Global Distribution of Tropical Cyclones (Hurricane) and/or Typhoon

Tropical storms or cyclones are large areas of the air pressure. They bring torrential (fast and heavy) rain and very heavy  strong winds to tropical regions. The picture above shows their distribution and what they are called hurricanes in the North and Central America and the North Atlantic. Dependant on the location, there may be from six to over 20 each year, but most occur between mid-summer and early autumn when the sea is warmest.


Anatomy of a Hurricane in the Northern Hemisphere

The same but opposite rule applies (Hurricanes) in the Sothern hemisphere.

Formation of Tropically Cyclones (Hurricanes) and/or Typhoons

For Hurricanes or Typhoons to form, there needs to be a large surface area of sea water warmer than 26 degrees Celsius, and the air above must have a humidity of at least 75%. The most likely to happen over the tropical parts of the Pacific and Indian Oceans between May and November in the northern hemisphere. Typhoons are the same but travel down in perspective to Hurricanes and also spin in a different direction. Tropical Cyclones/Hurricanes and Typhoons have an even worse affect if accompanied by a Cumo-Limbus cloud that rains heavily and increases damage.

Click for Clip 1

Click for Clip 2

Saffir-Simpson Scale

  1. Category 1 (super storm) – 80mph winds – Minimal Damage
  2. Category 2 – 100mph winds – Moderate Damage
  3. Category 3 – 120mph winds – Extensive Damage
  4. Category 4 – 140mph winds – Extreme Damage
  5. Category 5 – 160mph winds – Catastrophic Damage

Storm Surge – A storm surge is a change in sea level that is caused by a storm. They can lead to extensive flooding and are dangerous for people living in many coastal areas.

Case Study: Hurricane Katrina, New Orleans (MEDC/LIC)

Hurricane Katrina was the deadliest and most destructive Atlantic tropical cyclone in 2005. It is the costliest natural disaster, as well as one of the five deadliest hurricanes, in the history of the United States. Katrina is the seventh most intense Atlantic hurricane ever recorded, part of the 2005 season that included three of the six most intense Atlantic hurricanes ever documented. At least 1,833 people died in the hurricane and subsequent floods, making it the deadliest U.S. hurricane since the 1928 Okeechobee hurricane; total property damage was estimated at $108 billion (2005 USD) which is still a large cost for the supposed richest county in the world. Roughly four times the damage brought by Hurricane Andrew in 1992.

Hurricane Katrina formed over the Bahamas on August 23, 2005, and crossed southern Florida as a moderate Category 1 hurricane, causing some deaths and flooding there before strengthening rapidly in the Gulf of Mexico. The hurricane strengthened to a Category 5 hurricane over the warm Gulf water, but weakened before making its second landfall as a Category 3 hurricane on the morning of Monday, August 29, in southeast Louisiana. It caused severe destruction along the Gulf coast from central Florida to Texas, much of it due to the storm surge. The most significant number of deaths occurred in New Orleans, Louisiana, which flooded as the levee system catastrophically failed, in many cases hours after the storm had moved inland. Eventually 80% of the city and large tracts of neighbouring parishes became flooded, and the floodwaters lingered for weeks. However, the worst property damage occurred in coastal areas, such as Mississippi beachfront towns; over 90 percent of these were flooded. Boats and casino barges rammed buildings, pushing cars and houses inland; water reached 6–12 miles (10–19 km) from the beach.

The hurricane surge protection failures in New Orleans are considered the worst civil engineering disaster in U.S. history and prompted a lawsuit against the U.S. Army Corps of Engineers (USACE), the designers and builders of the levee system as mandated by the Flood Control Act of 1965. Responsibility for the failures and flooding was laid squarely on the Army Corps in January 2008 by Judge Stanwood Duval, U.S. District Court, but the federal agency could not be held financially liable because of sovereign immunity in the Flood Control Act of 1928. There was also an investigation of the responses from federal, state and local governments, resulting in the resignation of Federal Emergency Management Agency (FEMA) director Michael D. Brown, and of New Orleans Police Department (NOPD) Superintendent Eddie Compass.

Several agencies including the United States Coast Guard (USCG), National Hurricane Centre (NHC), and National Weather Service (NWS) were commended for their actions. They provided accurate hurricane weather tracking forecasts with sufficient lead time.

Case Study: Hurricane Mitch, Central America (LEDC/LIC)

In October 1998 Hurricane Mitch hit Central America and was the most Hurricane Mitch was the most deadliest and destructive Atlantic hurricane for over 200 years (since the Great Hurricane of 1780), displacing the Galveston Hurricane of 1900 as the second-deadliest on record (Mitch has since dropped to seventh). Nearly eleven thousand people were confirmed dead and almost as many reported missing. Deaths were mostly from flooding and mudslides in Central America, where the slow-moving hurricane then a Cumo-Limbus tropical storm dropped nearly 36 inches (900 cm) of rain water. The flooding and mudslides damaged or destroyed tens of thousands of homes, with total damage amounting to over $5 billion (1998 USD, $6 billion 2006 USD), which is hard to pay for an LEDC most of which was in Honduras and Nicaragua. Prior to Mitch, the deadliest hurricane in Central America was Hurricane Fi-fi in 1974, which killed an estimated 8,000–10,00.

Hurricane Mitch began as a tropical depression on 21st October to the south of the Caribbean.

By 26th October Mitch was a category 5 Hurricane on the Saffir-Simpson scale, moving west across the Caribbean which meant the wind speeds were around 250kmh. Experts at the time were not able to predict the movement or path of Mitch but could track it. By 28th October, Mitch started moving south west towards central America. The problem for Honduras, Nicaragua, El Salvador and more was that the forward movement was slow as well as the wind speeds only slightly lower as a result there was torrential rain for three days. Because of this there was extreme flooding that destroyed lots.


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