On August 19, 2019, the National Hurricane Center (NHC) identified a tropical wave—an elongated trough of low air pressure—within a monsoon trough over Guinea and Senegal in western Africa. Convective activity associated with the wave was limited by an abundance of Saharan dust in the region. Propagating west over the tropical Atlantic Ocean, the system remained disorganized for several days. On August 23, a defined area of low pressure consolidated at the surface and thunderstorm activity increased. The system acquired sufficient organized convection to be classified as Tropical Depression Five at 15:00 UTC on August 24. At this time the system was situated 805 mi (1,300 km) east-southeast of Barbados. A deep ridge imparted continued westward movement of the depression, steering it toward the Lesser Antilles. A small cyclone, it soon developed a defined inner-core with a 12 mi (18 km) wide eye-like feature. This marked the system's intensification into a tropical storm, at which time it was assigned the name Dorian by the NHC. Thereafter, moderate wind shear and surrounding dry air limited further organization. Rainbands gradually wrapped more around Dorian on August 25–26, though convection remained inconsistent.
Dorian continued moving west and barely missed Barbados, bringing tropical storm-force winds and heavy rain. It then started moving northwestward toward Saint Lucia. At 10:00 UTC on August 27, Dorian made landfall on the island of Saint Lucia as a tropical storm, briefly disrupting the core of the storm, before entering the Caribbean Sea. The storm underwent a center relocation further north, to the west of Martinique, causing the island to experience tropical storm-force winds as well. Dorian had been predicted to travel northwest and pass over or near the Dominican Republic or Puerto Rico, possibly allowing their mountainous terrain to weaken the tropical storm. At that time, dry air and wind shear were expected to prevent Dorian from attaining hurricane status—although just barely. However, Dorian took a more northerly track than expected, causing it to pass to the east of Puerto Rico and hit the US Virgin Islands. On August 28, Dorian intensified into a Category 1 hurricane as it approached Saint Thomas in the US Virgin Islands, where hurricane-force winds were recorded; at 18:00 UTC that day, Dorian made landfall on Saint Thomas at Category 1 intensity. However, the hurricane's small size prevented mainland Puerto Rico from experiencing hurricane- or tropical storm-force winds, although this was not the case for the Spanish Virgin Islands.
Once the system moved north past the Virgin Islands, the storm entered a more favorable environment. On the next day, the system started to rapidly intensify, reaching Category 2 status early on August 30. Rapid intensification continued, and the storm eventually reached major hurricane status several hours later, on the same day. This strengthening trend came to a halt for the remainder of the day, but soon resumed. The system continued strengthening, and on August 31, Dorian attained Category 4 major hurricane status. Dorian reached Category 5 intensity on the following day. On the morning of September 1, a dropsonde deployed by a NOAA aircraft measured a wind gust of 176 knots (326 km/h; 203 mph) at the surface. With one-minute sustained winds of 180 mph (285 km/h) and a minimum pressure of 913 mbar (27.0 inHg), the NHC noted that Dorian was the strongest hurricane in modern records to affect the northwestern Bahamas.
The amount of precipitation produced by Hurricane Dorian from August 27 to September 9.
At 16:40 UTC on September 1, Hurricane Dorian made landfall on Great Abaco Island in the Bahamas, with one-minute sustained winds of 185 mph (298 km/h), wind gusts over 220 mph (355 km/h), and a central barometric pressure of 911 millibars (26.9 inHg). The storm's central pressure bottomed out at 910 millibars (26.87 inHg) within a few hours, as Dorian reached its peak intensity during landfall. Storm chaser Josh Morgerman observed a pressure of 913.4 mbar (26.97 inHg) in Marsh Harbour. Hurricane Dorian's forward speed decreased around this time, slowing to a westward crawl of 5 mph (8.0 km/h). At 02:00 UTC on September 2, Dorian made landfall on Grand Bahama near the same intensity, with the same sustained wind speed. Afterward, Dorian's forward speed slowed to just 1 knot (1.2 mph; 1.9 km/h), as the Bermuda High that was steering the storm westward weakened. Later that day, the storm began to undergo an eyewall replacement cycle to the north of Grand Bahama; the Bermuda High to the northeast of Dorian also collapsed, causing Hurricane Dorian to stall just north of Grand Bahama. Around the same time, the combination of the eyewall replacement cycle and upwelling of cold water caused Dorian to begin weakening, with Dorian dropping to Category 4 status at 15:00 UTC. Due to the absence of steering currents, Hurricane Dorian stalled north of Grand Bahama for about a day. Hurricane Dorian subsequently weakened to a Category 2 storm on September 3, before beginning to move northwestward at 15:00 UTC, parallel to the east coast of Florida, with Dorian's wind field expanding during this time.
While moving northwestward, Dorian gradually reorganized. At 06:00 UTC on September 5, Dorian moved over the warm waters of the Gulf Stream and completed its eyewall replacement cycle, reintensifying into a Category 3 hurricane off the coast of South Carolina. However, several hours later, Dorian encountered high wind shear, causing the storm to weaken to a Category 2 hurricane, and later to Category 1 intensity, early on September 6. On September 6 at 12:35 UTC, Dorian made landfall in Cape Hatteras, North Carolina as a Category 1 hurricane, with 1-minute sustained winds of 90 mph (150 km/h) and a minimum central pressure of 956 mb (28.2 inHg). Afterward, Dorian began to transition into an as it quickly moved northeastward, completing its transition on September 7. The storm subsequently restrengthened, due to baroclinic processes, generating Category 2 hurricane-equivalent winds. Several hours later, at 7:05 p.m. AST on September 7 (23:05 UTC on September 7), Dorian made landfall on Sambro Creek, Nova Scotia, as a Category 2-equivalent , before making another landfall on the northern part of Newfoundland several hours later. By 11:00 p.m. AST on September 8 (03:00 UTC on September 9), Dorian had moved into the Labrador Sea, 375 miles off the coast, moving northeastward at 24 mph (39 km/h), with wind speeds of 60 mph (97 km/h), maintaining tropical storm-strength winds. As Dorian no longer posed a threat to Atlantic Canada at that time, the NHC issued their final advisory on the storm. On September 10, Dorian's extratropical remnant dissipated off the coast of southern Greenland.