A rare over 1,000-year rainfall event inundates Pearl River County on Halloween

NEW ORLEANS (WVUE) - An extremely rare rainfall event unfolded across Pearl River County on Halloween night, dropping more than 19 inches of rain in just six hours near Crossroads, MS.

According to the National Weather Service precipitation frequency estimates, the rainfall totals far exceeded what is classified as a 1,000-year event. That means the odds of this type of rainfall occurring in any given year at this location are just 0.1%, or 1 in 1,000.

According to the National Weather Service, a 1000 year rainfall event criterion in this area is 12 inches of rain in six hours. Parts of Pearl River County received nearly 20 inches, far exceeding the limit, which only goes up to 1000 year events.

The extraordinary deluge caused the National Weather Service to issue a Flash Flood Warning with a rare “catastrophic” tag. That indicates that it was an extremely dangerous flood capable of catastrophic damage and a severe threat to human life.

This alert triggered the Wireless Emergency Alerts system, allowing the NWS to send warnings directly to cell phones in affected areas. The message urged those in the path of the rain to seek higher ground.

Storm reports indicate at least one home flooded on Buckbranch School Rd near Humphry Rd, with debris observed floating in the rapidly moving water. A high-water rescue was conducted on Humphry Rd, approximately 4 miles northeast of Crossroads, as water levels rose dramatically.

The West Hobolochitto River near McNeil experienced rapid water rises of approximately 12 feet overnight, reaching moderate flood stage before leveling off.

A 1,000-year rainfall event is a statistical term used by the NWS to describe a specific rainfall amount of a given duration and intensity.

It’s important to note that such a rainfall event doesn’t automatically guarantee a 1,000-year flood. Actual flooding depends heavily on local drainage systems, soil saturation levels, and the size of the watershed.

While Pearl River County bore the brunt of the historic rainfall, Metairie also experienced significant flooding when eight inches fell in just three hours. That rainfall was classified as a 100-year event, which means a 1% chance of occurring in any given year.

The extreme rainfall was fueled by an active jet stream pattern, influenced by the strong El Niño we are experiencing this fall.

This active jet stream positioned itself over our very warm atmosphere and warm Gulf waters, creating an ideal environment for the moisture needed to produce extreme rainfall rates and catastrophic flooding.

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