Katrina: Ten Years After

Ten years ago, the United States suffered one of its greatest natural disasters in its history. The monster that caused it left 80% of the Big Easy flooded and miles of coastline destroyed. In the midst of the chaos, the best of humanity surfaced in the form of selfless deeds done by individuals whose names will never be known to history. However, as the clouds cleared and the flood waters slowly fell, the world bore witness to the face of America that would rather remain unseen. This is the face of political power and pride that hindered relief efforts. This is also the face that is far more racist and prejudiced than the average American would like to believe. The monster that brought this clarity was a hurricane; a hurricane named Katrina.

August 23, 2005 (EDT): Tropical Depression Twelve

GOES-12 Visible imagery of TD-12

GOES-12 Infrared (IR4) imagery of TD-12

GOES-12 Water Vapor (IR3) imagery of TD-12

At 2:00 pm EDT (1800 UTC) on August 23, 2005, the National Hurricane Center (NHC) began issuing advisories on tropical depression Twelve. The storm was expected to intensify slowly, if at all. This was due to heavy westerly vertical wind shear; the same shear that a few days earlier had caused tropical depression Ten to fall apart. However, the dissipation of Ten was part of a series of complex interactions that ultimately led to TD-12's formation.

TD-12 shortly after being upgraded to tropical depression status. Notice how the shear is keeping most of the cloudiness to the south and east of the storm's center.

To understand the genesis of this storm, it is necessary to go all the way back to August 11, when a tropical wave entered the Atlantic basin from Africa. A tropical wave is essentially a pulse of low pressure that travels along or near the equator, producing a region of instability; a breeding ground for tropical cyclones. While this wave made its way across the Atlantic, tropical depression Ten was struggling to survive against heavy shear that threatened to tear it apart. Late on the 13th, Ten lost its battle and slowly began to shred apart as it approached the Leeward Islands. Finally, late on the 18th, the system fell apart for good.

When a tropical cyclone is sheared apart, a couple different things can happen, in this case, the mid-level circulation detached from the low-level circulation. Ten's low-level circulation persisted for several more days while moving generally westward until it dissipated completely on the 21st. Meanwhile, the mid-level circulation lagged behind and began tracking northwestward, passing north of the Leeward Islands. The next day, August 19th, the tropical wave caught up to the mid-level circulation and merged with it, creating a large area of showers and thunderstorms north of Puerto Rico.

The resulting disturbance continued northwestward without much organization due to the heavy shear until it finally began to consolidate in the afternoon of the 22nd while just east of the Turks and Caicos. As the shear continued to weaken, the disturbance became more organized, prompting the NHC to upgrade the system to a tropical depression the next day.

This loop of near-infrared (IR2), sometimes called short-wave IR, imagery was made in three hour increments. Near-infrared is more detailed than standard IR, but, not as clear as visible; unlike visible though, near-infrared can used at night. The blue line is the track of TD-10, with its location indicated by the cross. The number above the cross is the maximum one minute sustained wind speed in knots, and the lower number is the minimum central pressure in millibars. This loop ends just a few hours before the system was upgraded to TD-12. While the tropical wave is not obvious on the satellite imagery, notice how the area of cloudiness originating from Ten suddenly pulses and begins to intensify right about the time it passes north of Puerto Rico; this is when the mid-level remains of Ten merged with the tropical wave.