passing through the trough that generated the wind shear, the storm began to strengthen again. While moving about 350 miles (560 km) north of Puerto Rico on September 30, the winds of the storm increased to 90 mph (145 km/h). By this time, an eye was clearly visible on satellite imagery. After holding steady for 36 hours, the storm recurved around a ridge on October 1. Gladys then began to undergo rapid deepening, becoming a Category 2 hurricane at 18:00 UTC and Category 3 hurricane the following day. Early on October 2, the storm strengthened into a Category 4 hurricane. At 08:46 UTC on October 2, Hurricane Hunters measured maximum sustained winds of and a minimum barometric pressure of . Moving northeast, the hurricane hunters soon observed a pressure of , making it the one of the most intense high-latitude storms ever observed. Despite its distance from Cape Hatteras, the system was briefly observed on radar. It became one of few hurricanes at the time to be seen on radar over from the continental United States. Thereafter, the storm weakened slightly, and was downgraded to a Category 3 hurricane early on October 3. Accelerating at unusually high speeds, Gladys passed 70 miles (115 km) southeast of Cape Race, Newfoundland on October 3. The storm finally merged with a large extratropical cyclone on October 4. Observation, preparations and impact While over the Atlantic Ocean, a National Oceanic and Atmospheric Administration (NOAA) C-130 hurricane hunter aircraft flew into Gladys on October 1 on a research mission. The mission was to study the storm and use the information to improve seeding operations for the now-defunct Project Stormfury. Gladys was the strongest storm to threaten the East Coast of the United States since Hurricane Hazel in 1954. Although initially not expected to threaten, meteorologists at the NHC forecast the storm to make landfall along the East Coast of the United States within three days. A hurricane watch was issued for North Carolina's Outer Banks on October 1, extending from Cape Lookout to Kitty Hawk. However, the watch discontinued as Gladys pulled away, though the storm was still considered a threat to the nation. In Manteo, residents began laying sandbags and filling their cars up with fuel in anticipation for possible evacuation, and the United States Coast Guard sent a plane equipped with a loudspeaker to warn fishermen of the hurricane. However, despite warnings, about