Introductory Meteorology

Lesson 12. The Tropics: Hurricanes


a satellite image of Hurricane Katrina
A MODIS satellite image of Hurricane Katrina (August 2005).
Credit: NASA

On the morning of Monday, August 29, 2005, Hurricane Katrina barreled ashore in southeast Louisiana. Katrina made landfall as a category 3 hurricane which means it was packing wind between 111 to 130 mph. Unless you've actually experienced (and survived) such wind speeds it's difficult to paint an accurate portrait of the conditions on the ground at the point of landfall. This is what I tell my students... Consider that the minimum wind speed necessary for a tropical cyclone to be a hurricane is about 75 mph. Now imagine putting your hand out of the window of a car moving down the highway at that speed. You can hardly hold your hand steady in the air rushing by. Now think about that same force over your entire body. And remember, this is just for a minimal hurricane. The power of these storms is not to be underestimated!

To see what I mean, check out these videos. In the first Hurrucane Katrina video, the first 6 minutes really give you a good feel for conditions as the storm moved through (don't ask me why there are dolphins in the pool!). In the second Hurricane Katrina video, check out the wind funneling through the hotel at about the 2 minute mark. The second video also gives you a good glimpse of a hurricane's most dangerous weapon... water!

At 10:11 a.m. on August 28th (24 hours before Katrina's landfall along the Louisiana coast), the National Weather Service office in New Orleans issued this chilling public bulletin which describes in graphic detail the conditions that would likely occur as the storm came ashore. This bulletin marked a watershed moment in NWS history in that no public bulletin had ever been so explicit in describing the danger faced by those choosing not to evacuate. In hindsight, it was an ominous foreshadowing of what was to come. Unfortunately for many, by the time the storm rolled in, it was too late.

Read on.