Dear Tom,
How did the word “depression” get associated with hurricanes?
–David Ligare
Dear David,
When an area of disturbed weather in the tropics begins to acquire a circulation but has top wind speeds of less than 39 m.p.h. it is classified as a tropical depression. The term depression is related to the low barometer readings at the center of the circulation, which is depressed when compared to the surrounding air pressure.
According to the American Meteorological Society’s “Glossary of Meteorology,” the word depression can be applied to any area of low pressure or trough, not just to tropical systems.
If the tropical depression strengthens, it becomes a named tropical storm when sustained winds reach 39 m.p.h. and a hurricane when speeds reach 74 m.p.h.
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