Hurricane Katrina, which hit the US Gulf coast earlier this week, may have plenty of company this storm season. Warm sea-surface temperatures are fuelling hurricane growth. This image, taken by NASA's Aqua satellite, shows a three-day average for 25–27 August and highlights areas where temperatures reached around 28° C or above (red, orange and yellow), which is hot enough for hurricanes to form.

Credit: UPI PHOTO/NASA-SVS/NEWSCOM

Katrina reached category 5 status before weakening and making landfall as a category 4 hurricane on 29 August. Meteorologists at Colorado State University in Fort Collins predict that there will be 20 named tropical storms this year. Katrina is the eleventh, and the hurricane season runs to the end of November.

The low-lying city of New Orleans escaped the annihilation that forecasters had feared from Katrina — Mississippi bore the brunt of the storm's force.

After this story went to press, the situation worsened in New Orleans. Some of the levees that protect the area from the sea were breached, causing floods that have left much of the city underwater. Many fatalities have been reported. Nature wrote about the possibility of this happening last year (see Hurricane Ivan highlights future risk for New Orleans) and will follow the situation in the coming days.