Compared to hurricanes and winter storms, thunderstorms are small. The typical thunder- storm in Mississippi is about 15 miles in diameter and lasts for about 30 minutes. Despite their small size, all thunderstorms are dangerous. Mississippi is susceptible to many types of dangerous weather conditions from thunderstorms. Mississippi thunderstorms can produce tremendous lightning, a phenomenon that kills more people across the country each year than tornadoes.

Thunderstorms over the state occasionally become severe. Severe thunderstorms produce high winds and occasionally hail and tornadoes. Fortunately, only about 5 percent of all thunder- storms become severe, with only about 1 percent becoming tornadic. However, abundant moisture from the Gulf of Mexico leads to torrential rainfall from Mississippi thunderstorms, which in turn leads to flood potential.

Severe weather can visit the state on any day of the year, and at any time of the day. However, severe storms are most likely to occur during the Spring and Fall, and are most likely during the afternoon and early evening hours of the day.

In April 2003, severe storms struck central Mississippi producing hail to the size of baseballs and producing some of the worst flooding and flashing flooding that part of the state has ever seen.

Several atmospheric factors must come together for severe thunderstorms to form in Mississippi. These conditions include:

* a supply of warm moist air flowing out of the Gulf of Mexico at low levels and cool dry air moving in from the west at higher levels. These airflows result in an unstable airmass over Mississippi;

* a weather system to lift the low level moist air and produce thunderstorms. This lift can come from a front or other boundary, or from a weather system at mid levels of the atmosphere; and

* an increase in wind speed with height (this is called wind shear).

Wind shear is an important ingredient. It keeps the falling precipitation away from the rising air columns (updrafts) that keep the storm going. Since the precipitation doesn't fall through the updraft and weaken it, the updraft can live longer and grow stronger!

Severe thunderstorm detection has been greatly improved with the installation of Doppler Weather Radar. This new radar helps Meteorologists see developing cores of large hail high in the storm, estimate rainfall amounts for the diagnosis of flash flood potential, and locate circulations within thunderstorms that can lead to tornado development. Unfortunately, weather radar only shows what is aloft, not what is being observed at ground level.

Trained SKYWARN storm spotters help the National Weather Service determine what is happening on the ground. It is through the coupled effort of Doppler Radar and storm spotter reports that the public is successfully warned of approaching danger! If you have an interest in both weather and protecting your community, and would like to join SKYWARN, contact the National Weather Service.

Severe Weather Awareness Week gives all of us an opportunity to increase our under- standing of Mississippi severe thunderstorms, and to prepare for the threats they bring.