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2023 Fort Lauderdale floods

Extreme weather event

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Through State of emergency, Tornado and President of the United States

Meteorological background

The flooding rainfall in eastern Broward County, Florida, spanning from the midday hours of April 12 to roughly midnight on April 13, was supported by the combination of a weather front that was moving slowly through South Florida, and an intensifying area of low pressure in the Gulf of Mexico. The Weather Prediction Center (WPC) wrote in its Excessive Rainfall Discussion, that was issued on April 10, that, "...it anticipated that atmospheric conditions supportive of flash flooding in the Florida peninsula would persist into April 12, highlighting a "Marginal Risk" of flash flooding for urban areas along the coast of southeastern Florida...". The WPC later upgraded the risk to a "Slight Risk", as the confidence increased in the potential for flash flooding, exacerbated by heavy antecedent rainfall on April 11. A flood watch was issued for southeastern Florida during this time. Rainfall spread across south central Florida, throughout the morning of April 12. This was happening in advance of a slow, northward-progressing warm front. The local atmospheric environment was conducive to heavier precipitation rates, bearing precipitable water amounts near the climatological maxima for the region (approximately 1.7–1.9 in (43–48 mm)). Heavier showers and thunderstorms embedded in the largely stratiform rains grew during the morning. The combination of the morning rainfall and rain from preceding days saturated the soils in Broward and Miami-Dade counties to the point that only 1.5–2.0 in (38–51 mm) of rain would need to fall in an hour to produce flash flooding according to flash flood guidance.

The moist conditions persisted into the afternoon and evening, enabling the highly efficient production of rainfall in the storms as the warm front progressed north of Key Largo and into the Miami area. By around 5:30 p.m. EDT, 2–6 in (51–152 mm) of rain had fallen across the Miami metropolitan area. During the evening hours, stationary thunderstorms caused torrential rainfall over Fort Lauderdale, fueled by the locally moist atmosphere and a persistent inflow drawing moisture from the Atlantic towards the Florida coast. National Weather Service Miami, Florida, issued a flash flood emergency at 7:58 p.m. EDT for Fort Lauderdale and Hollywood highlighting the potential for 2–4 in (51–102 mm) of additional rainfall atop the 10–12 in (250–300 mm) of rain that had already fallen. The cluster of storms began to weaken by around 11:00 p.m. EDT after dropping 10–20 in (250–510 mm) of rain in the Fort Lauderdale area. The day's storms also produced two brief tornadoes in Broward County, each producing EF0-rated damage; the first one touched down near West Hollywood at 3:26 p.m. EDT while the second touched down near Dania Beach at 9:41 p.m. EDT. The combination of wind shear, interaction between the warm front and the coast, and enhanced convection and vorticity resulting from the aggregation of thunderstorms may have produced conducive conditions for the development of tornadoes.

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