[1] The long-lived system formed on September 24 just off the west coast of Africa, and for several days maintained a general westward track.

The depression produced heavy rainfall in the Lesser Antilles, reaching 12 in (300 mm) on Barbados; it left three deaths and moderate damage on the island.

[2] The system exited the west coast of Africa the next day,[1] and on September 24 it developed into a tropical depression about 95 mi (153 km) southwest of Conakry, Guinea.

[3] A nearby upper-level trough — an elongated area of low pressure — hindered further strengthening, and on October 1 the depression struck the island of Saint Lucia.

[2] In the Caribbean, the trough caused the depression to slow to a westward drift, resulting in several days of heavy rainfall in the region, particularly Puerto Rico.

[2] Around October 3, forecasters advised residents on islands from Barbados and St. Vincent through Guadeloupe to prepare for floods, high seas, and gale-force gusts.

[5] On October 10, a warning to be on guard against gusts was issued to owners of light aircraft in Puerto Rico and the Virgin Islands.

[9] Heavy rains impacted the U.S. Virgin Islands, including a total of 11.4 in (290 mm) recorded by the National Park Service on Saint John.

[2] In the aftermath of the disaster, Luis A. Ferré, the Governor of Puerto Rico, declared a state of emergency over the whole island,[19] asking for $10 million (1970 USD) in federal aid.

[18] The Governor of the Virgin Islands, Melvin Evans, requested aid similar to Puerto Rico,[17] and that territory was also declared a federal disaster area about a week after the rains ended.

[21] The heavy rainfall in the Virgin Islands caused a marked dinoflagellate algal bloom in the days after the rains ended.