It strengthened to its initial peak as a moderate tropical storm, and weakened due to increasing wind shear late on the August 23.

Atmosphere convection fluctuated as its associated tropical wave moved across the Caribbean Sea and a mid-level circulation developed.

Shower and thunderstorm activity increased as it crossed Central America,[1] and a broad area of low pressure formed about 115 mi (185 km) south of the Mexican coast on August 19.

On 1800 UTC August 21, advisories were initiated on Tropical Depression Nine-E while located roughly 205 mi (330 km) southeast of Salina Cruz, Mexico.

[1] Upon becoming a tropical cyclone, the storm was located in a favorable environment with sea surface temperatures near 30 °C (86 °F) and fairly weak wind shear.

[7] However, high levels of northeasterly wind shear caused the system to weaken slightly the next day,[1] and by early August 24, the NHC was no longer forecasting the storm to become a hurricane.

Microwave imagery at 0834 and 1714 UTC showed a closed ring of thunderstorm activity that resembled an eye and by early August 25, the cyclone was just below hurricane intensity.

On 1800 UTC, Frank reached its peak intensity of 90 mph (150 km/h) and 978 mbar (hPa; 28.88 inHg) while located 350 mi (560 km) south of the southern tip of the Baja California Peninsula.

While at peak intensity, satellite imagery showed a small but distinct eye surrounded by a central dense overcast, or a large area of thunderstorm activity.

[1] On August 27, the NHC downgraded Frank into a tropical storm, with poorly organized convection located west of the center due to strong wind shear.

[11] Frank rapidly lost all thunderstorm activity because of cooler water, and the storms intensity was reduced to a swirl of clouds while it turned towards the north due to a mid-level trough.

Frank degenerated into a remnant low while located 230 mi (370 km) southwest of the southern tip of Baja California.

[13] Officials gave Frank a hazard rating of intense for the Mexican Pacific, and strong for Baja California Sur.