By 0000 UTC on October 17, the transition was completed and Michael was reclassified as a tropical storm as supported by satellite classifications via the Dvorak technique. Shortly thereafter, the National Hurricane Center initiated advisories on Tropical Depression Seventeen; post-analysis later discovered it was actually a tropical storm. A well-defined eye quickly developed early on October 17 as Michael began to strengthen and continued to organize. That afternoon, Michael rapidly intensified further and was upgraded to a hurricane as Reconnaissance flights found winds of . At that point, Michael began to move northward. While Michael was maintaining minimal hurricane status, the eye remained ragged, yet well-defined. Early on October 19, Michael briefly strengthened to 140 km/h (85 mph) before weakening slightly six hours later. Tracking into cooler water, Michael began its extratropical transition while accelerating to the northeast towards Newfoundland, which prevented significant weakening. The acceleration was caused by a shortwave trough embedded within strong southwesterly mid-level flow.