Katrina: FORMATION OF KATRINA

The following is a synopsis of the conditions that produced historic Hurricane Katrina

The formation of Hurricane Katrina was caused by the interaction between Tropical Depression Ten’s remains and tropical wave at the southeastern area of the Bahamas on August 23rd.

This tropical depression strengthened into Tropical Storm Katrina the next day. It then moved slowly along a northwesterly then westerly track through the Bahamas, increasing in strength during this time.

A few hours before landfall in south Florida at around 6.30 EDT on August 25th, Katrina strengthened to become a category 1 (windspeeds of 75mph or greater) hurricane. Landfall occurred between Hallandale Beach and North Miami Beach, Florida, with windspeeds of approximately 80 mph (70 kts). Gusts of above 90 mph (78 kts) were measured as Katrina came ashore.

Landfall- the time at which a storm passes over shore

As the storm moved southwest across the tip of the Florida peninsula, Katrina's winds decreased slightly before regaining hurricane strength in the Gulf of Mexico.

Given that Katrina spent only seven hours over land, its strength was not significantly diminished and it quickly re-intensified shortly after moving over the warm waters of the Gulf.

Katrina moved almost due westward after entering the Gulf of Mexico. A mid-level ridge centered over Texas weakened and moved westward allowing Katrina to gradually turn to the northwest and then north into the weakness in the ridging over the days that followed.

Atmospheric and sea-surface conditions (an upper level anticyclone over the Gulf and warm SSTs) were conducive to cyclone's rapid intensification, which lead to Katrina attaining 'major hurricane' status on the afternoon of the 26th.