Water levels are rising and winds are picking up along the Louisiana coast and bands of heavy rain are arriving.
Lumbering toward the coast at just 3 mph, Barry presents “a long duration heavy rainfall and flood threat” according to the National Hurricane Center.
At 11 p.m. Friday, Barry was centered 75 miles south of Morgan City, Louisiana.
The storm strengthened Friday morning, it peak winds climbing from 50 to 65 mph, before its intensity leveled off in the afternoon through the evening. The National Hurricane Center projects some additional strengthening and that it will become a hurricane by Saturday morning, when it it approaches landfall along the central coast of southern Louisiana.
On Friday afternoon and evening, New Orleans had winds sustained from 20 to 30 mph with gusts to 40 mph. But fears that the storm surge up the Mississippi River might test the city’s levees eased Friday evening when the National Weather Service announced the river crested at 17 feet, several feet below the height at which the levees would have been topped:
Right along the Gulf Coast winds were picking up while the storm surge was building Friday afternoon and evening.
“An observation platform at South Timbalier Block off the coast of Louisiana has recently reported a sustained wind of 47 mph (76 km/h) with a gust to 59 mph (94 km/h),” the Hurricane Center said Friday evening.
Poweroutage.us reported over 29,000 customers without power in Louisiana.
At Port Fourchon, Louisiana’s southeasternmost port, photos showed the storm surge lapping over the roadway during the afternoon:
Roads were inundated to the east in Terrebonne Parish, while storm surge flooding was seen as far east as Dauphin Island, Alabama.
What comes next
The strongest winds, heaviest rain and highest water levels are expected Saturday, when serious flooding could occur.
A hurricane warning is in effect for much of the central and eastern coast of Louisiana, with tropical storm warnings covering most of the rest of the state’s coastline. The tropical storm warning also covers Lake Pontchartrain and New Orleans.
In addition to the hazards posed by high water, damaging winds are expected in the narrow zone where the storm center makes landfall, with winds sustained over 70 mph and gusts possibly exceeding 80 mph. Farther inland and even considerable distances away from the storm center, tropical-storm-force winds over 40 mph and gusts over 60 mph are possible.
#Barry will be strong enough to take down some trees - easier on already saturated soils - that could be life-threatening by falling on cars, roads (and cars later hit) or homes,” tweeted Rick Knabb, The Weather Channel’s hurricane expert.
Power outages are likely.
Tornadoes are also possible within the storm’s rainbands as they move inland off the Gulf of Mexico.
Although Barry is expected to become only a Category 1 hurricane and could even remain a tropical storm, hurricane specialists frequently say that “there’s more to the story than the category.”
The category rating of a hurricane refers only to its peak sustained wind speed — it says nothing about how big the storm is, its storm surge and how much rain it will produce.
Detailed rainfall forecasts
The rainfall forecast is ominous for places like New Orleans, Baton Rouge, Lafayette, and southern Mississippi.
“Barry is expected to produce total rain accumulations of 10 to 20 inches over south-central and southeast Louisiana along with southwest Mississippi, with isolated maximum amounts of 25 inches,” the Hurricane Center said. “These rains are expected to lead to dangerous, life threatening flooding over portions of the central Gulf Coast into the Lower Mississippi Valley.”
Heavy rain bands may pass over some of the same areas repeatedly, with rates as high as three to four inches per hour.
The heaviest rain will progress from south to north through southeastern Louisiana and southwestern Mississippi on Saturday, moving into northern Louisiana, southwestern Arkansas and west-central and northern Mississippi on Sunday. By Monday, heavy rain is likely in western Tennessee and central and northern Arkansas.
“[E]arly next week, Barry is expected to produce rainfall accumulations of 4 to 8 inches across western portions of the Tennessee Valley," the Hurricane Center said.
During the middle of next week, between Tuesday and Thursday, Barry’s remnant rains are likely to spread through the Tennessee and Ohio valleys and potentially to the Mid-Atlantic.
Detailed surge forecasts
The storm surge, or water pushed ashore by the storm’s wind, could reach 3 to 6 six feet above normal tide levels in the most at-risk areas.
“There is a danger of life-threatening storm surge inundation along the coast of southern and southeastern Louisiana, portions of Lake Pontchartrain, and portions of coastal Mississippi where a Storm Surge Warning is in effect,” the Hurricane Center reported.
Here are some specific forecasts from the Hurricane Center:
- Mouth of the Atchafalaya River to Shell Beach: 3 to 6 ft
- Shell Beach to Biloxi MS: 3 to 5 ft
- Intracoastal City to the Mouth of the Atchafalaya River: 3 to 5 ft
- Lake Pontchartrain: 3 to 5 ft
- Biloxi, Miss. to the Mississippi/Alabama border: 2 to 4 ft
- Lake Maurepas: 1 to 3 ft
An asymmetric storm
Two ingredients that shape a storm and where its heaviest rainfall occurs are the vertical wind shear (change in wind speed and direction with height) and low- to mid-level relative humidity (moisture content). For the past day or so, the northern Gulf Coast has lucked out, and Barry’s wet side has remained south of its center, over water. That remains the case Friday — so far.
The forecast indicates that the mid-level dry air will get nudged to the west by the storm’s circulation even as the wind shear remains northerly for at least the next day. What does that mean? If the forecast is right, the heaviest rain will be displaced almost entirely to the east of the center while areas west of the center see far less rainfall.
There’s a small chance a sharp cutoff in the heavy rainfall sets up near New Orleans such that instead of seeing 10 to 15 inches of rain, the city sees significantly less (on the order of a few inches). But forecasting where the heaviest rain starts and stops is difficult, and New Orleans should prepare for the worst.