When did people first realize that hurricanes are a particular type of storm system?
Trade winds from a general easterly direction occur almost all of the time in the Caribbean and tropical Atlantic. A hurricane approaching from any direction except from the south would change the wind direction because winds spiral counterclockwise into the hurricane. For example, a hurricane approaching from the east would cause the wind direction to back to northerly, while one approaching from the west (very rare in the tropics before recurvature occurs) would cause the wind direction to veer to southerly. If a hurricane approached from a general southerly direction, the wind would remain generally easterly but would gradually increase in speed and gustiness. Hurricanes are often accompanied by anticlyclonic outflow at upper levels; this could be observed via the motion of cirrus clouds.