The fifth named storm of the 2009 Atlantic hurricane season, Erika originated out of a tropical wave on September 1 near the Lesser Antilles.

Later that day, the system reached its peak intensity with winds of 50 mph (85 km/h) and a barometric pressure of 1004 mbar (hPa; 29.65 inHg).

Increased wind shear caused the storm to weaken shortly thereafter, with Erika barely maintaining tropical storm-status by September 2.

On September 3, Erika weakened to a tropical depression as the low pressure center became fully displaced from convective activity.

Several other islands recorded moderate rainfall form the system before the tropical storm degenerated into a remnant low.

In Puerto Rico, the cyclone's remnants produced heavy rainfall, peaking at 7.58 in (193 mm), that triggered flooding in several regions.

[8] On September 1, a Hurricane Hunter reconnaissance mission into the low found a closed circulation center and tropical storm-force winds.

[9] Several hours after being classified, the storm reached its peak intensity with winds of 50 mph (85 km/h) and a barometric pressure of 1004 mbar (hPa; 29.65 inHg).

[10] In post-storm analysis of these readings, it was determined that the NHC had overestimated the wind speeds in an area of unusually heavy rains.

[1] By the morning of September 2, Erika became significantly disorganized, and Hurricane Hunters reported the possibility that multiple circulation centers existed within the broader storm system.

[12] Around 1830 UTC, the center of Erika passed over the island of Guadeloupe with winds of 40 mph (65 km/h)[1] as the storm entered the eastern Caribbean Sea.

Early on September 3, the tropical storm watches were upgraded to warnings as Erika drifted through the eastern Caribbean.

[1] Exports from the Hovensa oil refinery in St. Croix, with a daily production of roughly 500,000 barrels (79,000 m3), were canceled as ports across the island were closed.

[29] In Puerto Rico, the remnants of Erika produced significant amounts of rainfall, causing the rivers of La Plata, Loíza and Caguitas to overflow their banks and trigger widespread flooding.