April 12, 2023 is One for the Record Books

This is a brief meteorological report of the unprecedented and significant rain event in Fort Lauderdale, Florida in the afternoon and evening hours of April 12, 2023. Many of these numbers are preliminary and may change when finalized by the National Weather Service.

 The National Weather Service in Miami has provided preliminary estimates of rainfall in the past 24 hours and a screenshot is provided below (Figure 1).[1] The highest reported total is from Fort Lauderdale and is 25.91 inches of rainfall in the 24-hour period from 7:00AM on Wednesday, April 12 to 7:00AM on Thursday, April 13.

Preliminary precipitation report from the last 24 hours from the National Weather Service in Miami, Florida.
Figure 1. Preliminary precipitation report from the last 24 hours from the National Weather Service in Miami, Florida. Estimates are provided on a per County basis and for observations over 10 inches.

Based on historic data, the previous maximum 24-hour (or 1-day) rainfall total for the Fort Lauderdale-Hollywood International Airport was 11.30” on April 25, 1979. These 24-hour totals would shatter that record.[2] The Fort Lauderdale Beach station had a record event on October 15, 1965, of 15.88”. This event would be on-par or exceed that record. This is well above the December 2019 event that also shut down the Fort Lauderdale-Hollywood International Airport.

In addition to looking at the event as one of the most extreme ever recorded at this location, it is helpful to examine how often such a rainfall event should be expected in the area. The figure below is the Point Precipitation Frequency diagram using NOAA Atlas 14 data. Based on a 24-hour duration, a 25.91” of rain would be equivalent to a 1000-year storm or have a 0.1% chance of occurrence each year. Our construction design standards are generally based on a 100-year storm (which is 15.8” of rain in 24-hours), which would be ten times more frequent. The 16.71” report in SSE Fort Lauderdale would roughly be equivalent to a 200-year 24-hour storm.

Regardless of the final numbers, this storm created rainfall totals well above the general 100-year design standard of our community and flooding of homes and businesses would be expected.

Figure 2. Point Precipitation Frequency (PF) Estimates from NOAA Atlas 14, Volume 9, Version 2 for the Fort Lauderdale-Hollywood International Airport location.

[1]  National Weather Service Miami Tweet at 9:40AM on Thursday, April 13, 2023: https://twitter.com/NWSMiami/status/1646508714462158848?s=20
[2] Iowa Environmental Mesonet Automated Data Plotter: https://mesonet.agron.iastate.edu/plotting/auto/