A strong tropical wave exited the coast of Africa on August 14, moved westward as a disorganized system, and passed through the Cape Verde islands on August 15.
On August 17, a weak area of low pressure developed in the system about 750 miles (1,200 km) west-southwest of the Cape Verde islands.
Convection increased over the western portion of the wave axis, and the system began to become better organized on August 18 while located about 1,250 miles (2,000 km) east of the Lesser Antilles.
However, convection around the system diminished on August 19, and later that day it began to move through the Lesser Antilles.
Despite favorable upper-level winds and falling atmospheric pressures, there were initially no signs of a circulation at the surface.
Convection again increased early on August 20, and it gradually became better organized.
Based on a ship's wind report of the system, it is estimated the wave developed into Tropical Depression Nine on August 21 while located about 260 miles (415 km) south of San Juan, Puerto Rico.

The depression quickly showed signs of organization with the development of banding features around its blossoming convection.
Due to a favorable upper level environment, forecasters predicted the depression to intensify to a 70 mph (110 km/h) tropical storm after making landfall on Haiti and eastern Cuba.
Upper-level outflow remained well-defined, though convection waned near the center early on August 22.
The depression appeared to continue organizing, with a well-defined cloud band to its north and east.
However, strong southwesterly wind shear unexpectedly increased over the system, and the depression degenerated into a tropical wave late on August 22, south of the eastern tip of the Dominican Republic.
The system retained a well-defined cloud pattern with a vigorous mid-level circulation, and forecasters at the National Hurricane Center indicated regeneration could have occurred at any time.
The wave axis moved over the Dominican Republic early on August 23, and became disorganized over the mountainous terrain of Hispaniola.
There existed the potential for redevelopment as it moved into a potentially more favorable area, though the National Hurricane Center ceased monitoring the system on August 25 when redevelopment appeared unlikely.
A strong tropical wave exited the coast of Africa on August 14, moved westward as a disorganized system, and passed through the Cape Verde islands on August 15. On August 17, a weak area of low pressure developed in the system about 750 miles (1,200 km) west-southwest of the Cape Verde islands. Convection increased over the western portion of the wave axis, and the system began to become better organized on August 18 while located about 1,250 miles (2,000 km) east of the Lesser Antilles. However, convection around the system diminished on August 19, and later that day it began to move through the Lesser Antilles. Despite favorable upper-level winds and falling atmospheric pressures, there were initially no signs of a circulation at the surface. Convection again increased early on August 20, and it gradually became better organized. Based on a ship's wind report of the system, it is estimated the wave developed into Tropical Depression Nine on August 21 while located about 260 miles (415 km) south of San Juan, Puerto Rico.
The depression quickly showed signs of organization with the development of banding features around its blossoming convection. Due to a favorable upper level environment, forecasters predicted the depression to intensify to a 70 mph (110 km/h) tropical storm after making landfall on Haiti and eastern Cuba. Upper-level outflow remained well-defined, though convection waned near the center early on August 22. The depression appeared to continue organizing, with a well-defined cloud band to its north and east. However, strong southwesterly wind shear unexpectedly increased over the system, and the depression degenerated into a tropical wave late on August 22, south of the eastern tip of the Dominican Republic. The system retained a well-defined cloud pattern with a vigorous mid-level circulation, and forecasters at the National Hurricane Center indicated regeneration could have occurred at any time. The wave axis moved over the Dominican Republic early on August 23, and became disorganized over the mountainous terrain of Hispaniola. There existed the potential for redevelopment as it moved into a potentially more favorable area, though the National Hurricane Center ceased monitoring the system on August 25 when redevelopment appeared unlikely.
Tropical Depression Nine (2003)