Hurricane Cleo was the strongest Atlantic hurricane of the 1958 Atlantic hurricane season, based on maximum sustained winds. It remains one of only three Category 5 hurricanes to avoid land in the historical database–the others were Dog of 1950 and Easy of 1951. The third tropical cyclone, first hurricane, and first major hurricane of the season, Cleo developed from a tropical wave off the coast of Africa. It intensified to a tropical storm 300 miles (480 km) southeast of Praia, Cape Verde. It moved steadily westward, and it intensified to a hurricane on August 12. On August 14, the cyclone turned northward, and its forward motion decelerated. Later, the hurricane strengthened to its peak intensity of 160 mph (260 km/h) on August 15. On August 16, its movement increased, and the cyclone moved around the periphery of an upper-level anticyclone. Its northwest path was halted on August 18, and it turned northeast in response to a shortwave trough. The hurricane transitioned to an extratropical cyclone on August 20, causing no casualties in its path.
On August 11, a low pressure area was observed near the Cape Verde islands, which quickly became a tropical storm. Operationally, lack of data prevented the classification of Cleo until August 14, when it was observed by the Hurricane Hunters. On August 12, several ships reported the presence of an expansive circulation. On August 13, Cleo intensified to a hurricane, and it continued to quickly intensify, reaching major hurricane status on August 14. The cyclone's motion slowed, and an upper trough near 50°W allowed it to turn northward. On August 15, the hurricane's minimum central pressure of 948 mbar (28.0 inHg) was measured by reconnaissance aircraft, and it reached its estimated maximum sustained winds of 160 mph (260 km/h). The hurricane's strongest winds were not documented, so it is assumed that the cyclone reached its peak strength during the day.
On August 16, the upper-level trough weakened, and a ridge of high pressure forced Cleo to turn northwest. Recurvature was not completed because of the storm's southerly latitude and climatological time of year. The storm slowly weakened to a strong Category 3 hurricane, and it passed within 450 miles (725 km) of Bermuda on August 18. Its speed slowed during the day, and a strong shortwave trough exited the Northeastern United States. In response, the cyclone accelerated northeast, and its winds diminished below major hurricane status. On August 19, the weakening cyclone passed southeast of the Canadian Maritimes, becoming extratropical the next day. Cleo's remnants moved east-southeast on August 21, and dissipated west of Portugal.
Preparations and impact
On August 14, the Weather Bureau office in San Juan, Puerto Rico issued a hurricane watch for the Lesser Antilles, and caution was advised for watercraft in the cyclone's path. When the storm moved more northward, the watch was discontinued on August 15. Hurricane Cleo ultimately caused minimal impact on land, limited to 2 inches (51 mm) of rainfall in St. John's, Newfoundland. The extratropical remnants of Cleo eventually affected Europe, but damages are unknown.