Tropical Cyclones are warm-core, low pressure systems that develop over the tropics or subtropical regions and have an organized circulation.
Depending on the ocean, a tropical cyclone could be named a hurricane (Atlantic/Eastern Pacific Oceans), a typhoon (Western Pacific Ocean) or a cyclone (Indian Ocean).
Favorable conditions for tropical cyclones to form include:
- Warm ocean waters (at least 80°F) to about 150 feet below the surface.
- An atmosphere that cools fast enough so it can be potentially unstable to moist convection.
- Moist air at around 16,000 feet above sea level.
- At least 300 miles from the equator. If the storm develops too close to the equator, there is not enough Coriolis Force to allow for the cyclone to spin.
- Low amounts of vertical wind shear (the change in wind speed with height) between the levels of the atmosphere.
Tropical Cyclones form in seven tropical "basins" on a regular basis:
- Covers the North Atlantic Ocean, Gulf of Mexico and Caribbean Sea
- Official Hurricane Season runs from June 1 through November 30. Peak activity is in early- to mid-September.
Northeast Pacific Basin
- Covers Mexico towards the International Dateline
- Tropical Cyclone Activity from late May through early November. Peak is late August and early September.
Northwest Pacific Basin
- Covers the area from the International Dateline to Asia, including the South China Sea
- Activity can occur year round, although less likely in February through early March. Peak is late August and early September.
North Indian Basin
- Includes the Bay of Bengal and the Arabian Sea
- Activity is from May through November, although strongest storms occur from April to June and late September through early December.
Southwest Indian Basin
- Covers an area from Africa to 100 degrees east
- Tropical Season begins in late October and reaches peak in mid-January and again in mid-February to early March. Activity usually ends in May.
Southeast Indian/Australian Basin
- From 100 degrees east to 142 degrees east
- Begins in late October and early November and peaks in mid-January and mid-February to early March. The season typically ends in May.
Australian/Southwest Pacific Basin
- An area from 142 degrees east to about 120 degrees west
- Season begins in late October and ends in early May. The peak is in late February or early March.