The West Indian hurricanes originate in tropical latitudes, somewhere north of the equator. They move in a northwesterly direction until they reach the latitude of westerly winds; then they recurve and move in a northeasterly course. In some instances a hurricane recurves before reaching the Florida coast; in others it advances until the recurve crosses the Gulf of Mexico. In the first instance it is not likely to cover anything more than
Storm cards showing movement of wind in West Indian hurricane.
the coast plain; in the second the storm center may sweep the eastern United States from the Gulf to the St. Lawrence valley. After recurvature, hurricanes move more rapidly—occasionally as much as 50 miles per hour.
These storms are called West Indian hurricanes from the fact that they are first noted at a West Indian weather station, frequently at Barbados. They sometimes originate far to the eastward of the West Indies, sometimes in the Caribbean Sea. Since vessels are now fitted with radio-telegraphic apparatus, hurricanes are commonly reported before reaching a land weather station. Once discovered, their movements are closely watched and are made known to shipping until they disappear in the North Atlantic.
The dead calm of tropical seas is the real beginning of the West Indian hurricane. The air, moist almost to the dewpoint, is heated next the surface until it becomes more buoyant than the colder air above it. Finally the unstable equilibrium is overcome and an updraught occurs. The warm air of the updraught is chilled by its expansion and its moisture is condensed. The latent heat thus set free adds to the strength of the up-
