Hurricane Flora
Hurricane Flora was an extremely deadly and devastating tropical cyclone that is among the deadliest Atlantic hurricanes in recorded history, with a death total of at least 7,193. The seventh tropical storm and sixth hurricane of the 1963 Atlantic hurricane season, Flora developed from a disturbance in the Intertropical Convergence Zone on September 26 while located southwest of the Cape Verde islands. After remaining a weak depression for several days, it rapidly organized on September 29 to attain tropical storm status. Flora continued to strengthen, reaching Category 3 hurricane status after moving through the Windward Islands and passing over Tobago, and it reached maximum sustained winds of in the Caribbean.
The storm struck southwestern Haiti near peak intensity, turned to the west, and drifted over Cuba for four days before turning to the northeast. Flora passed over the Bahamas and accelerated northeastward, becoming an extratropical cyclone on October 12. Due to its slow movement across Cuba, Flora is the wettest known tropical cyclone for Cuba, Haiti, and the Dominican Republic. The significant casualties caused by Flora were the most for a tropical cyclone in the Atlantic Basin since the 1900 Galveston Hurricane.
Meteorological history
The tropical wave that ultimately spawned Hurricane Flora moved off the coast of West Africa sometime late on September 23 or early September 24. The disturbance gradually became better organized as it moved west across the tropical Atlantic. Imagery from the TIROS-7 satellite captured the developing system on September 26 in the vicinity of, revealing a large and complex cluster of clouds. Two disturbances comprising the complex were detected by the satellite, though it is unclear which particular disturbance became Flora. While the United States Weather Bureau contemporaneously assessed that Flora formed from the precursor disturbance on September 26, a reanalysis of the official Atlantic hurricane database by the Hurricane Research Division determined that the Flora first became a tropical depression on September 28, 48 hours later than initially assessed, on account of the incipient disturbance's lack of organization in both the September 26 TIROS-7 imagery and a subsequent image taken on September 27. Weather observations were scant in the vicinity of Flora around the time it became a tropical depression, preventing a more accurate determination of Flora's genesis.However, a KLM jet airliner en route to Paramaribo, Suriname, encountered disturbed weather east of the Lesser Antilles on September 28, prompting the Weather Bureau office in San Juan, Puerto Rico, to request special weather observations from ships in the area the next day and schedule an aerial reconnaissance mission into the storm for September 30. Retrospective analyses of Flora indicate that it reached tropical storm intensity on September 29. Delayed ship reports documented gale-force winds and low pressures in the vicinity of Flora between September 29–30. Flora reached hurricane intensity east of the Lesser Antilles by 00:00 UTC on September 30.
Aircraft hurricane reconnaissance first intercepted the center of Flora around east of Trinidad at 14:07 UTC on September 30, finding a well-defined eye surrounded by an eyewall spanning across within the compact hurricane. The flight also assessed winds exceeding the hurricane-force threshold and a central air pressure of 994 mbar. A summary of the 1963 Atlantic hurricane season authored by Weather Bureau staff and published in the Monthly Weather Review described the mission's observations as " that hurricane Flora was the most concentrated and best organized tropical cyclone of the past two years." Hurricane Flora rapidly intensified as it traversed the Windward Islands throughout September 30. The center of the hurricane made landfall on Tobago at around 18:00 UTC that day. A minimum air pressure of 974 mbar was registered at Crown Point, Tobago, which when reconciled with Flora's size, location, and forward speed suggested maximum sustained winds of around 105 mph. The center of Flora passed roughly south of Grenada about three hours later as the hurricane entered the southeastern Caribbean Sea.
Within the southeastern Caribbean Sea, Flora took a steady course towards Haiti's Tiburon Peninsula that curved progressively northwards with time. The hurricane's rate of intensification on October 1 had become more gradual, though the storm was continuing to strengthen. However, Flora began to strengthen quickly between October 2–3, with periodic aircraft reconnaissance missions finding increasing winds and deepening air pressures. Flight-level winds reaching were recorded by reconnaissance missions on both October 2 and October 3. The HRD reanalysis estimated that Flora became a major hurricane by around 06:00 UTC on October 2, with Flora's winds continuing to increase before reaching a peak of around 150 mph by 18:00 UTC on October 4; this intensity is equivalent to a Category 4 hurricane on the modern Saffir–Simpson hurricane wind scale. Based on aircraft reconnaissance data, Flora had a minimum central air pressure of around 933 mbar and wind gusts of 180–200 mph at the time of its peak strength. The hurricane had slowed its forward course and began moving more towards the north-northwest on October 3, leading to a landfall on southwestern Haiti near Côtes-de-Fer at 01:00 UTC on October 4.
While the HRD reanalysis assessed that Flora made landfall at its peak intensity, the eight-hour gap between landfall and the preceding aircraft reconnaissance mission meant that Flora may have been considerably stronger than estimated at its Haitian landfall. Flora traversed the Tiburon Peninsula in roughly two hours before emerging into the Windward Passage. The hurricane subsequently made landfall on eastern Cuba approximately east of Guantanamo Bay at around 18:00 UTC on October 4 with maximum sustained winds estimated at 120 mph ; this intensity is equivalent to a Category 3 hurricane on the Saffir–Simpson scale.
Changing atmospheric circulation patterns over the United States in early October 1963 were consequential in shaping Flora's trajectory leading up to and after the hurricane's landfalls on Haiti and Cuba. Although Flora's northward curve leading to its landfall on Haiti was spurred by the presence of a trough off the U.S. East Coast, the subsequent northward retreat of the trough and strengthening ridging over the eastern U.S. caused Flora to slowly curve west between October 5–7. Additional areas of high pressure to Flora's west and east prevented the hurricane from moving away from the region, resulting in Flora lingering near or over eastern Cuba for several days. While the hurricane's winds diminished somewhat due to Flora's persistent interaction with land, the storm maintained a strong intensity due in part to a conducive atmospheric environment and the presence of moist tropical air atop the warm waters surrounding Cuba. The hurricane also grew during its traversal of eastern Cuba, with its radius of outermost closed isobar expanding nearly three-fold. On October 6, Flora moved over the Gulf of Guacanayabo and likely restrengthened. At around 00:00 UTC on October 7, the center of Flora again moved ashore Cuba, this time a few miles west of Santa Cruz del Sur, with estimated maximum sustained winds of 100 mph. A strengthening anticyclone over the Gulf of Mexico stopped Flora's slow westward advance on October 7. Concurrently, the passage of two troughs off the U.S. East Coast and The Bahamas caused Flora to curve east and later northeast over the same regions of Cuba previously traversed by the hurricane. Between October 7–8, Flora's winds weakened to tropical storm intensity. However, Flora promptly intensified after reemerging into the Atlantic Ocean near Gibara along the northern Cuban coast after 12:00 UTC on October 8, regaining hurricane intensity six hours later.
Now moving more steadily towards the northeast, the center of Flora passed over Mayaguana at around 06:00 UTC on October 9 with sustained winds of around 100 mph. A minimum air pressure of 977 mbar was recorded on the island within Flora's eye. The hurricane continued to intensify after leaving the Bahamas, with sustained winds topping out at 110 mph. Accelerating northeast, Flora passed southeast of Bermuda on October 10 and began losing its tropical characteristics as it moved over the cooler waters of the mid-latitude Atlantic. The occurrence of frontogenesis by around 00:00 UTC on October 12 signaled the completion of Flora's transition into an extratropical cyclone. Although Flora weakened during this period, ships in the storm's vicinity observed hurricane-force winds. Remaining a strong extratropical cyclone, the remnants of Flora progressed northeast and meandered near the Denmark Strait between October 15–17, gradually weakening before being absorbed by a stronger extratropical cyclone.
Preparations
The Weather Bureau in San Juan, Puerto Rico, issued a hurricane warning for Trinidad, Tobago, and the Grenadines south of Saint Vincent in the cyclone's first advisory on Hurricane Flora. Gale warnings were later issued for islands off northern Venezuela and from Saint Vincent northward to Martinique. Advisories on Flora emphasized the danger of the hurricane and advised preparations to be rushed to completion. The advisories also recommended small craft throughout the Windward Islands to remain at harbor and for shipping in the path of the hurricane to advise extreme caution. People in low-lying areas and near beaches were advised to evacuate to higher grounds, as well. Lead time was short, especially in Tobago which received news of the approaching hurricane just two hours before it struck.On October 2, two days before it made landfall on southwestern Hispaniola, the San Juan Weather Bureau issued a gale warning from Barahona in the Dominican Republic to Sud-Est, Haiti. Advisories recommended small craft in the southern portions of the countries to remain at port. Later that day, the gale warning was upgraded to a hurricane warning in southwestern Haiti. On the day of when Flora made landfall, advisories recommended all citizens on beaches and in low-lying areas west of Santo Domingo to evacuate. Carmelo Di Franco, the provisional Director of Civic Defense for the Dominican Republic, organized safety procedures and the dissemination of tropical cyclone bulletins from the San Juan Weather Bureau. Di Franco also organized for the transmission of hurricane emergency information to citizens, believed to reduce the loss of life. On the afternoon before the hurricane struck, the head of the Haitian Red Cross prohibited radio broadcasts of tropical cyclone advisories for fear of panic among citizens. As a result, many thought the hurricane would miss the country.
In Cuba, the government enacted the Second Agrarian Reform Law the day before Hurricane Flora made landfall and had its attention focused on revolutionary politics rather than hurricane preparations. Officials at the Cuban National Observatory issued radio bulletins on the hurricane, which included the position of Flora, its intensity, direction of motion, and necessary warnings. By the time the hurricane left the island, more than 40,000 had been evacuated to safer areas.
The Weather Bureau predicted Flora to turn to the northwest after entering the Windward Passage and affect the Bahamas. Forecasters advised those in The Bahamas to quickly complete preparations, though the eye of the hurricane did not pass over the archipelago until four days later. When Flora turned to the northeast out to sea, forecasters again advised Bahamian citizens to prepare for the hurricane, and on October 9, weather advisories advised the southeastern Bahamas to prepare for gale-force winds and strong tides. One advisory considered there to be less than a 50% chance of the hurricane reaching southeastern Florida, though weather bulletins advised Florida citizens to monitor the hurricane. At its closest approach to Florida, the hurricane remained away, though gale warnings were issued from Stuart to Key West due to the hurricane's large size.