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Historic flooding hits Louisiana: Parts of the state experienced a ‘1-in-1000-year’ rainfall event


Heavy rain produced by a slow-moving storm started affecting portions of the US Gulf Coast on August 4, 2016. By Friday, August 12, parts of central Gulf Coast were under historic flooding. Florida was first to receive heavy rain, followed by southeastern Louisiana and southern Mississippi. On Friday, August 12, parts of Louisiana received a 1-in-100 to 1-in-1000-year rainfall events and the heavy rain is still not over. NWS warns copious moisture from the Gulf of Mexico will bring more rounds of heavy rain to the central Gulf Coast states through the weekend. Additional heavy rain chances will extend from southwest Texas all the way to northern New England on Saturday, August 13. By Sunday, the mid-Mississippi Valley will also see a significant threat of flash flooding.

Louisiana was under heavy rainfall since Monday, August 8, but the worst came on Friday, August 12 when extreme amounts of rain fell on already heavily soaked ground. Severe flooding that followed prompted the governor to declare a state of emergency in the southern part of the state.

This region is now experiencing a historic flooding, the worst in more than 30 years.

On Friday alone, floods forced evacuations of dozens of people stranded in homes by the waist-high water and left at least three people dead. With more people reportedly missing, rescue operations have continued through Saturday, August 13.

Estimates of the Louisiana rainfall, which totaled more than 305 mm (12 inches) overnight Friday, indicate somewhere between a 1-in-100-year to 1-in-500-year rainfall event near Zachary and Greensburg, CNN reported. Baton Rouge Airport recorded 207.8 mm (8.18 inches) of rain Friday, the wettest August day on record since weather records began over 100 years ago. One weather station in Livingston measured 434 mm (17.09 inches) since midnight, making the deluge a 1-in-1000-year rainfall for that location.

"All seven major roads into Greensburg, near Baton Rouge, were under water and the town was largely cut off," director of operations for the St. Helena Parish Sheriff's Office, Michael Martin, said. "Only large National Guard vehicles have been able to get into and out of town. At least two dozen high-water rescues were carried out Friday, with stranded residents pulled from cars, rooftops and, in one case, a tree."

"This is the worst that I've seen and can remember," Martin told CNN.

Rivers in Louisiana and southern Mississippi have risen toward historic crests. The Tickfaw River in Montpelier crested at record levels in multiple locations, rising nearly 6 meters (20 feet) since midnight, August 12. By 09:00 local time, it was already at the highest level ever recorded. Tangipahoa, Amite, Comite and Tchefuncte rivers are either at major flood stage or expected to reach major flood stage soon.

A flash flood watch is in effect until 07:00 local time on Sunday, August 14, for Ascension, Assumption, East Baton Rouge, East Feliciana, Livingston, Pointe Coupee, St. Helena, Tangipahoa, West Baton Rouge and West Feliciana parishes, and Amite, Pike and Wilkinson Counties.

State of emergency declaration will remain in effect until September 10.

revised list of shelters for those impacted by floods was issued early Saturday morning by the office of Louisiana Governor John Bel Edwards.

In Mississippi, several roads of various counties were shut down, and at least five people were rescued in the small town of Osyka in Pike County. More than 203 mm (8 inches) inches of rain had fallen in this area by Friday morning, but some houses were already flooded on Thursday.

Total rainfall estimates between August 4 and 11, 2016. Credit: NASA/GPM/IMERG

NASA's Integrated Multi-satellite Retrievals for GPM (IMERG) data were used to make estimates of total rainfall over the Gulf Of Mexico during the period from August 4 – 11, 2016.

These results show that the most extreme rainfall during this period fell over the waters of the northern Gulf Of Mexico south of the Florida Panhandle where IMERG estimates indicate that from 500 mm (~20 inches, shown in purple) to over 900 mm (~35 inches, shown in peach) of precipitation may have fallen.

Over coastal areas, the highest totals are on the order of 300 to 400 mm (~12 to 16 inches, shown in dark red) and occur mostly along the northeast and north-central Florida Gulf Coast along with parts of southeastern Louisiana.

Video courtesy CNN

Video courtesy CBS

Video courtesy Weather Nation

Video courtesy Weather Nation


According to NWS forecast issued at 11:17 UTC on August 13 (07:17 EDT), a low- to mid-level cyclone over the Lower Mississippi Valley will slowly begin to lift northward into the Middle Mississippi Valley by Sunday evening into Monday, August 15. Tropical moisture over the Gulf Coast Region will aid in producing showers and thunderstorms over the Lower Mississippi Valley with heavy rain at times through Monday.

Meanwhile, a quasi-stationary front extending from New England westward to the Great Lakes then southward to the Southern Plains will have tropical moisture pooling along the boundary through Monday. Showers and thunderstorms will develop along and near the boundary through Monday with some areas getting heavy rain. Additionally, tropical moisture and daytime heating over the Southeast will produce showers and thunderstorms over the area during the afternoon into the late evening hours on Saturday into Monday. In addition, upper-level energy over Upper Mississippi Valley will move eastward into Canada by late Saturday night. The energy will trigger showers and thunderstorms over parts of the Upper Mississippi Valley/Upper Great Lakes that will likewise move into Canada overnight Saturday.

Elsewhere, monsoonal moisture and daytime heating will produce showers and thunderstorms over parts of the Southern/Central Rockies during the afternoon into the late evening on Saturday and Sunday.

Stay safe!

Each year, more deaths occur due to flooding than from any other thunderstorm-related hazard.

The Centers for Disease Control and Prevention report that over 50% of all flood-related drownings occur when a vehicle is driven into hazardous flood water. The next highest percentage of flood-related deaths is due to walking into or near flood waters.

People underestimate the force and power of water and many of them die in automobiles as they are swept downstream. Of these drownings, many are preventable, but too many people continue to drive around the barriers that warn you the road is flooded.

A mere 15 cm (6 inches) of fast-moving flood water can knock over an adult. It takes just 30 cm (12 inches) of rushing water to carry away a small car, while 60 cm (2 feet) of rushing water can carry away most vehicles. It is NEVER safe to drive or walk into flood waters. Be extra cautious!

Featured image: Tangipahoa, Louisiana rescue operations on August 12, 2016. Credit: Weather Nation

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