Storm guide Here's a quick explanation of the stages of a tropical disturbance so that you'll know what your TV weathercaster is talking about: Most disturbances usually begin as a group of thunderstorms that, under the right atmospheric conditions, evolve into a tropical depression, with winds near the center between 23 and 39 miles per hour. A tropical depression can evolve into a tropical storm in as little as half a day. It is at this stage that the National Weather Services identifies it with one of the designated names for the season. Maximum winds are between 39 and 73 miles per hour. The storm becomes more organized and circular in shape, resembling a hurricane. Hurricanes have wind speeds of 74 miles per hour or more, with winds, clouds and precipitation rotating around a central core, or eye. The intensity of hurricanes is measured in categories from 1 to 5, based on a measurement standard known as the Saffir-Simpson Scale. All hurricanes, once they reach landfall, are capable of inflicting damage to buildings and vegetation. The strongest hurricanes, category 5, have winds of greater than 155 miles an hour and are capable of blowing away small buildings and causing extensive damage to homes and industrial buildings. While hurricanes can live in the ocean for as long as three weeks, they lose intensity and dissipate once they reach cooler ocean water or move inland. Source: Department of Atmospheric Sciences, University of Illinois at Urbana-Champaign

It's no coincidence that the Atlantic hurricane season coincides with summer. With the days long and temperatures hot, ocean temperatures grow warmer across the Gulf of Mexico and Atlantic Ocean. Clusters of thunderstorms develop from the convergence of warm tropical breezes and disturbances moving off the continent of Africa. If atmospheric and oceanic conditions are just right, a tropical cyclone develops.

It takes a unique combination of ocean, wind and atmospheric conditions to create a tropical cyclone and an even more unique set of conditions for the cyclone to strengthen into a hurricane. On any given summer day, there are numerous disturbances and thunderstorms across the tropics, but only a handful of these systems ever develop into an organized tropical cyclone. In a typical year, the Atlantic basin sees about 10 named storms. Of these, six become hurricanes, and about two of the hurricanes develop into intense hurricanes (category 3, 4 or 5).

Most of recent hurricane seasons have been active
By most accounts, this year's hurricane season is expected to be a busy one, with an above normal number of storms. This outlook reflects a trend of above normal activity that began nearly a decade ago in 1995. Since then, all but two Atlantic hurricane seasons have been above normal.

The science of hurricane prediction has come a long way in recent years. Forecasters have discovered that that several factors found in the oceans and in the atmosphere months before and during the hurricane season can give strong clues as to how many storms will develop. These factors include Atlantic sea surface temperatures, wind speed and direction at various points in the atmosphere across the Atlantic, and surface pressure at strategic locations at points in the Atlantic and Pacific.

Scientists with the National Hurricane Center indicate that this year, most of the indices are positive, meaning conditions will be favorable for many of the disturbances and clusters of storms to become organized -- in other words, a busy hurricane season.

According to Dr. William Gray of Colorado State University, this year's Atlantic hurricane season will see 14 named storms. Eight of these storms are forecast to become hurricanes, and three of the hurricanes should be intense. Dr. Gray and other hurricane researchers believe there is a strong probability that at least one of the year's tropical storms or hurricanes will move inland somewhere along the Texas coast this year. These scientists believe that the position of the Bermuda high this year will be favorable to steer many developing storms toward the western Gulf of Mexico and Texas.

Hurricanes have been prominent in Central Texas weather history
Central Texas is no stranger to hurricanes and tropical storms. Some of the heaviest rains and worst floods in Central Texas weather history have come from hurricanes and tropical storms that made landfall along the Texas coast. For instance, a dying tropical system in September 1921 produced 38 inches of rain in just 24 hours in the community of Thrall northeast of Austin. A dying tropical storm Amelia produced more than 20 inches of rain across a large part of the Hill Country in 1978, causing torrential flooding.

Last year, one hurricane (Claudette) and one tropical storm made landfall in Texas. However, both of these storms were relatively weak. Could this be the year a powerful storm strikes Central Texas, or even a weak storm that causes widespread flooding? No one knows the answer to this question. But with the forecast for an active hurricane season, Texans along the coast and well inland across Central Texas and the Hill Country need to take notice and be prepared.

Rose is LCRA's chief meteorologist. See his previous columns on weather and link to his regular weather forecast.

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