To make their forecasts more exciting, meteorologists stress certain words (cities with very bad weather, etc.), they speed up or slow down their rate of speech, they pause in certain places, and change their tone of voice. My next paragraph will give examples of all these things.
By stressing certain words, such as "tornadoes," "these storms are very, very severe," etc, they get across to you that what they are saying is very important. They usually speed up as they start their sentences, and slow down at the end of their sentences. They would pause where commas are, and also where periods were. One meteorologist changed his tone of voice when he said, "Drive with care," talking about severe weather around Wichita, Kansas, on May 16.
As you can see, meteorologists do use many methods to make their forecasts more exciting.