Wanderlust World Wanderlust World One of the most important indications of an impending hurricane is the time of year. Places subject to hurricanes tend to track their hurricane season -- those times when the ocean temperatures and wind patterns allow for hurricane formation. On the United States' Eastern seaboard, hurricane season lasts from June 1 to Nov. 30.
At about 96 hours before a hurricane hits land, perceptive beach-goers begin to notice swells in the ocean. According to the Atlantic Oceanographic and Meteorological Laboratory, these swells stand about 3 feet high and reach shore every 10 seconds. Regular waves, caused by local winds, often mask these swells, however, reducing the ability to notice the oncoming hurricane. These swells increase in size over the next two days, reaching heights of 9 feet and landing every eight seconds. By the time the barometer begins to drop (at 36 hours before landfall), the swells reach about 12 feet and land every seven seconds.
When the Hurricane of '38 hit Massachusetts, Christian I. Gunness was the first person to notice the storm closing in on the northeastern state, according to In the Loop, University of Massachusetts's staff news organization. Gunness manned the university's daily meteorological observations; when he checked the campus barometer, the readings descended to the very lowest possible point.
Barometers read atmospheric pressure. As a hurricane approaches, the air pressure descends relative to increasing wind speed. Throughout the hurricane, the air pressure continues to drop, reaching its lowest point in the eye (despite the lack of wind).
With a previously clear sky, you can easily notice the changes in atmospheric conditions during the two days before the hurricane reaches land. From 36 hours to 18 hours, the cloud cover changes rapidly. While at 36 hours, the sky may be free of clouds, a large veil appears over the eastern horizon. By 30 hours before landfall, the high cloud cover reaches land, with thick low clouds moving in below. These thicken over the next six hours, with rain squalls beginning around 18 hours before landfall.
From 24 hours before to the moment of landfall, the winds continuously increase in strength. At 24 hours before landfall, expect the winds to blow at about 30 mph. Over the next six hours, they increase to 46 mph, making it hard to stand. Within the next six hours (12 hours before landfall), the winds reach hurricane force, at about 75 mph. The wind now picks up small objects and breaks tree branches. Over the next 24 hours, the winds will increase to over 100 mph, and then start to reduce after the hurricane passes.