On October 23, an area of low pressure a few hundred miles east-northeast of the Lesser Antilles began to produce some shower and thunderstorm activity. Over the next few days, the disturbance moved slowly northward and atmospheric conditions for development improved. As westerly shear diminished, convection persisted closer to the center of the developing low. Late on October 26, the low-level center had become well-defined. However, due to its interaction with a nearby upper-level low, the system was classified Subtropical Storm Oscar. This was the seventh named storm in 2018 to be subtropical during some part of its lifetime, making 2018 the first known season for such an occurrence.
Interaction with the upper-level low caused Oscar to turn sharply westward on the 27th. Meanwhile, significant deepening took place, indicating that Oscar's maximum winds had increased. Oscar's structure evolved throughout that day until the cyclone possessed a small core of deep convection and maximum winds close to the center. As a result, it was reclassified as a tropical storm. A ridge pushed the system south of west on the 28th and favorable conditions allowed an eye feature to begin forming. Around the same time, Oscar strengthened into a hurricane. The trend of gradual intensification persisted on October 29 and the system became a category 2 that evening, reaching its peak intensity of 105 mph winds and a pressure of 970 mb. Meanwhile, a mid-latitude frontal system approaching from the west began to sheer the cyclone toward the north.
By the 30th, Oscar was picking up speed toward the north and north-northeast and began to encounter cooler waters as it passed east of Bermuda. As a result, deep convection near the center waned, the maximum winds dropped, and the system began to take on extratropical characteristics. Nevertheless, it remained a potent cyclone and brought rough surf to Bermuda that day. Around midday on October 31, Oscar transitioned to a hurricane-strength extratropical storm as it sped north-northeastward over the open Atlantic. The post-tropical low deepened over the north Atlantic during the following days, reaching a minimum pressure of 950 mb on November 2. It dissipated a few days later near Iceland.
This image shows the small hurricane Oscar at peak intensity as a category 2 hurricane.
Oscar did not directly affect any land areas during its time as a tropical or subtropical cyclone.
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