Tropical Storm Bertha is fading, but its moisture plume is fueling a serious East Coast flood threat
By Meteorologists Dakota Smith and Briana Waxman
(CNN) — Bertha continues its tour along the Gulf Coast, ushering in tropical storm-force wind gusts, hazardous beach conditions and pockets of rain. But its most significant impacts may unfold hundreds of miles away in the mid-Atlantic.
The disorganized, lopsided tropical storm was centered south of the Louisiana coast early Thursday with maximum sustained winds of 45 mph. Bertha will move near or along the Louisiana and upper Texas coasts through Thursday afternoon before moving inland over Texas by Thursday night.
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Meanwhile, a plume of tropical moisture linked to Bertha is feeding into a cold front draped across southeast Virginia, parts of the Carolinas and northern Georgia. That moisture will supercharge flooding rainfall through Thursday in the Mid-Atlantic and Southeast, potentially producing more serious impacts than those occurring near Bertha itself.
Bertha is forecast to maintain tropical storm strength until it reaches the upper Texas coast late Thursday, then dissipate over Texas by Thursday night or Friday. The storm could bring 2 to 4 inches of rain, with isolated totals of 6 inches, along the Texas Gulf Coast and in South Texas, potentially causing isolated flash flooding. Meanwhile, its moisture will continue feeding a more dire flood threat farther east.
Bertha is the second named storm of the Atlantic hurricane season, which has gotten off to a slow start compared to recent years as El Niño tightens its grip on parts of the basin.
Multi-day flood threat
The storm system that caused historic flooding in West Virginia Tuesday into Wednesday and wreaked havoc from the Ohio Valley to the East Coast will linger across Virginia and the Southeast through the end of the week.
Bertha’s moisture began funneling into that region in earnest on Wednesday, setting the stage for a new flood threat.
The influx of moisture and that storm system’s stalling front have already produced bands of rain in eastern Tennessee, southern Virginia and northern North Carolina. Storms in northeastern Tennessee prompted flash flood warnings to the north of Knoxville on Wednesday morning, with some places seeing up to 5 inches of rain within a few hours.
More rounds of rain are expected through Friday, and some areas could receive a month’s worth of rain in just a few days.
The rainfall in southern Virginia and North Carolina is needed to help quench drought conditions there, but too much rain repeating over the same areas over hours or days could quickly trigger dangerous flash flooding.
A Level 3 of 4 risk of flooding rain is in place for a portion of the Virginia-North Carolina border Thursday into Friday morning.
Thursday afternoon’s thunderstorms could pack rainfall rates up to 2 inches per hour — an intensity that can quickly overwhelm drainage systems and flood urban areas. Atlanta, Birmingham, Alabama, and Charlotte, North Carolina are among the cities at risk.
The flood threat will continue Friday, when a Level 2 of 4 risk stretches from coastal North Carolina through South Carolina, northern Georgia and into northeast Alabama.
Parts of the Level 2 risk area could be upgraded to Level 3 as forecast models gain a clearer picture of where exactly the heaviest rain will set up.
The-CNN-Wire
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