The effects of tropical cyclones include heavy rain, strong wind, large storm surges near landfall, and tornadoes. The destruction from a tropical cyclone, such as a hurricane or tropical storm, depends mainly on its intensity, its size, and its location. Tropical cyclones remove forest canopy as well as change the landscape near coastal areas, by moving and reshaping sand dunes and causing extensive erosion along the coast. Even well inland, heavy rainfall can lead to landslides in mountainous areas. Their effects can be sensed over time by studying the concentration of the Oxygen-18 isotope within caves.
After the cyclone has passed, devastation often continues. Fallen trees can block roads and delay rescues, with medical supplies, or slow the repairs to electrical lines, telephone towers or water pipes, which could put other lives at risk for days or months. Stagnant water can cause the spread of disease, and transportation or communication infrastructure may have been destroyed, hampering clean-up and rescue efforts. Nearly 2 million people have died globally due to tropical cyclones. Despite their devastating effects, tropical cyclones are also beneficial, by potentially bringing rain to dry areas and moving heat from the tropics poleward. Out at sea, ships take advantage of their known characteristics by navigating through their weaker, western half.
Hazards are often characterized as primary, secondary or tertiary. A primary hazard involves destructive winds, debris and storm surge. Secondary hazards include flooding and fires. Tertiary hazards include spikes in prices of food and other necessities, as well as long term hazards like water-borne diseases.
At sea
The exports and imports are halted in sea ports due to the cyclone. Some people lose their jobs as well. A mature tropical cyclone can release heat at a rate upwards of watts. Tropical cyclones on the open sea cause large waves, heavy rain, and high winds, disrupting international shipping and, at times, causing shipwrecks. Generally, after its passage, a tropical cyclone stirs up ocean water, lowering sea surface temperatures behind it. This cool wake can cause the region to be less favorable for a subsequent tropical cyclone. On rare occasions, tropical cyclones may actually do the opposite. 2005's Hurricane Dennis blew warm water behind it, contributing to the unprecedented intensity of Hurricane Emily, which followed it closely. Hurricanes help to maintain the global heat balance by moving warm, moist tropical air to the mid-latitudes and polar regions and also by influencing ocean heat transport. Were it not for the movement of heat poleward (through other means as well as hurricanes), the tropical regions would be unbearably hot.
North American colonization
Shipwrecks are common with the passage of strong tropical cyclones. Such shipwrecks can change the course of history, as well as influence art and literature. A hurricane led to a victory of the Spanish over the French for control of Fort Caroline, and ultimately the Atlantic coast of North America, in 1565. The Sea Venture was wrecked near Bermuda in 1609 which led to the colonization of Bermuda and provided the inspiration for Shakespeare's The Tempest.
Shipping
Mariners have a way to safely navigate around tropical cyclones. They split tropical cyclones in two, based on their direction of motion, and maneuver to avoid the right segment of the cyclone in the Northern Hemisphere (the left segment in the Southern Hemisphere). Sailors term the right side the dangerous semicircle since the heaviest rain and strongest winds and seas were located in this half of the storm, as the cyclone's translation speed and its rotational wind are additive. The other half of the tropical cyclone is called the navigable semicircle since weather conditions are lessened (subtractive) in this portion of the storm (but are still potentially quite hazardous). The rules of thumb for ship travel when a tropical cyclone is in their vicinity are to avoid them if at all possible and do not cross their forecast path (crossing the T). Those traveling through the dangerous semicircle are advised to keep to the true wind on the starboard bow and make as much headway as possible. Ships moving through the navigable semicircle are advised to keep the true wind on the starboard quarter while making as much headway as possible.
Upon landfall
The most significant effects of a tropical cyclone occur when they cross coastlines, making landfall then it destroys ships and lives.