How To Build A Hurricane

Everyone at one point in their lives has heard about hurricanes. It may be called a tropical storm, 
typhoon, tropical depression or cyclone depending on where you live. In the Caribbean we refer 
to this destructive force of nature as a hurricane.

What is a hurricane?

A hurricane is an intense tropical weather system of strong thunderstorms with a well-defined surface circulation and maximum sustained winds of 74 mph (64 kt) or higher. [1] In the Northern Hemisphere it usually rotates counterclockwise and in the Southern Hemisphere it rotates clockwise. This is due to the rotation of the earth, called the Coriolis Effect, whereby the rotation of the Earth creates air currents along the surface at the equator which is then pushed outwards.

Photo Credit:Lisa Gardiner/Windows to the Universe

How do they form?

Hurricanes need warm water and low steady air currents to form. The optimum temperature for the formation of hurricanes is around 26͐°C. At this temperature, water starts evaporating from the surface of the sea, creating warm moist air. This warm air would then expand and rapidly rise upwards, while cool air would sink to take its place. The process is then repeated creating currents from the surface of the ocean to the atmosphere. This vortex with a warm core consisting of ascending moist air and inside it another still warmer, but much drier air originally produced by strong subsidence [2]. If high winds are present it can disturb the flow of air. For a hurricane to form  there must be low wind speeds so that the level of moisture remains relatively the same creating the rotating motion of the system.

How are hurricanes built?

Tropical disturbances 

(rain clouds build over warm water)

Tropical depressions 

(rotating thunderstorms with 38 mph or less wind speeds)

Tropical storm 

(wind speed passes 39 mph)

Hurricane 

(wind speed passes 74mph)

References:

[1] http://www.hurricane.com/what-is-a-hurricane.php

[2] http://www.geophysica.fi/pdf/geophysica_1948_3_1_026_palmen.pdf
[Palmen, Erik. "On the formation and structure of tropical hurricanes." Geophysica 3, no. 1 (1948): 26-38. (pg10, para 5)]