A hurricane_ (in Asia most commonly called a typhoon - different from a seasonal monsoon or earthquake-caused tsunami is a large serious storm that only forms over warm water.

It is characterized by very high winds, big waves and a storm surge. While water does not rise quite so much as in a tidal wave it can be whipped up by wind to go further inland than most tidal waves. Hurricanes are a major flood control challenge.

Hurricanes are ranked from category I to V, pronounced "one" to "five". A storm of lesser force than a hurricane is called a tropical storm. These are closely watched to see if they will develop into hurricanes, based on wind direction, water temperature and air temperature factors.

A category IV or V hurricane has historically been rare, and even in the Gulf of Mexico it was assigned only a 0.5% probability in any given year, before climate change and Gulf of Mexico warming effects led to repeated hurricanes in Florida and then to Hurricane Katrina and Hurricane Rita.

Today it is unclear how useful historical information is in predicting hurricanes. The total number of more serious hurricanes has doubled worldwide, according to UK government advisor Ted Burke. It may be impossible to predict frequency of hurricanes in latitudes further north. For instance, the category III Hurricane Juan hit Nova Scotia, very far north in the Gulf Stream, in 2002, and much later in the year (September 30) than any prior major hurricane in that region. It is postulated that the hurricane window in the North Atlantic may have as much as tripled from two weeks to six weeks, which also triples the probability of a major hurricane, from perhaps once every fifteen years to once every five or so.

While the time in which hurricanes can strike may not increase as much in more southerly waters, the probability that many will strike in one year seems to be increasing drastically. In Florida in 2004, four hurricanes hit in one year. This was unprecedented and overwhelmed the [[emergency response]] system. This was however predictable given the increase in hurricane "hit rate".

Also, the absolute category of a hurricane does little to predict the damage it does: a category 2 hitting in a poorly defended urban area may do much more total life-and-money damage than a category V that hits an unpopulated coastline or sparse islands. Further, the shearing edge of the hurricane (where its total windspeed is a sum of its motion across water and its circular rotating motion) does damage equivalent to a tornado or the next level of hurricane up the scale. Indeed, as with Rita, which spun off tornadoes that did tremendous damage far inland, the circular winds of a hurricane spawn smaller storms.

Using satellite imaging, it is easy now to spot and warn of impending hurricanes, although it is no easier to deal with them.

In Cuba, over a million people can be, and have been, evacuated and put back in their homes, with no loss of life, in major hurricanes. It is therefore more a challenge of logistics and leadership than of materiel. In the USA, the US FEMA supposedly takes charge of such activities. But Brownie did a hell of a job:

According to much of the Hurricane Katrina commentary linked from dkosopedia, US hurricane response lacked compared to Cuba's or even to that of poor countries hit by the Asian tsunami in December 2004. Whether Canada would fare much better given a very large storm is difficult to say.

According to Paul Martin, all the emergency response authorities in Halifax, at federal, provincial and municipal levels of government are now "in one building". In the downtown.