Long-Lived Bill Meets its Demise in Mid-Atlantic

The books have finally been closed on Post-Tropical Cyclone Bill, which dumped heavy rain and clung to life as an identifiable system during a trek of more than 1,000 inland miles. The last advisory on Bill was issued by the NOAA Weather Prediction Center at 8:00 am EDT Sunday, almost five days after the cyclone made landfall on Matagorda Island, Texas, as a 60-mph tropical storm at 11:55 am CDT Tuesday, June 16. The poorly defined circulation associated with Bill was located on Sunday morning about halfway between Baltimore and Philadelphia, with maximum sustained winds a paltry 10 mph. Bill wasn’t designated as a tropical storm until 10:00 pm CDT on Monday, June 15, so an impressive 89% of Bill’s lifespan as a named entity (115 of 129 hours) took place inland. The National Hurricane Center handed off responsibility for Tropical Depression Bill to NOAA’s Weather Prediction Center at 4:00 am CDT Wednesday morning, when Bill was located south of Waco, TX. The system held together as a tropical depression much longer than expected--until 4:00 pm CDT Saturday afternoon (a total of 78 hours), when it was located about 65 miles NNW of Jackson, KY.

According to Weather Channel tropical expert Michael Lowry, the average post-landfall lifespan of 131 inland tropical cyclones since 1970 was just 36 hours, and only 12 of those systems lasted 78 hours or longer as inland tropical storms or depressions. The longest-lived was an unnamed, posthumously recognized tropical storm in mid-August 1987 that persisted for almost 7 days as a tropical cyclone after it made landfall, making only a brief dip into the northern Gulf along a track from Louisiana to Georgia.


Figure 1. This satellite/radar overlay from 8:30 am CDT Saturday, June 20, shows the still-robust fingerprint of clouds and thunderstorms around Bill--then still a tropical depression, although with some hybrid characteristics evident--as it moved along the Ohio Valley between Louisville and Cincinnati. Image credit: Greg Postel/Weather Channel.

Bill was especially robust on Wednesday afternoon and evening over the Texas/Oklahoma border area, where it produced isolated rainfall totals of more than a foot. As Bill drifted northward, it came under the influence of a weak upper-level trough that infused it with energy and allowed its moisture to stream northeastward. Some of Bill’s tenacity over Texas and Oklahoma may have resulted from the brown ocean effect, where extremely moist soils send large amounts of latent heat into the atmosphere. In the wake of Bill, yet another round of heavy thunderstorms fell over the border area around Lake Texoma on Sunday afternoon, pushing 60-day rainfall totals well into the phenomenal 35” - 40” range over several counties. Two people were rescued after a bridge collapse on Sunday afternoon along a farm-to-market road (FM 118) about 50 miles northeast of Dallas. The Red River at Gainesville, TX, reached a record crest of 42.05 feet on Friday, nearly swamping the Interstate 35 bridge before subsiding. The previous record crest of 40.08 feet occurred on May 31, 1987, during a well-established El Niño event, as is the case this year.


Figure 2. The Red River (separating Oklahoma and Texas) reached a record crest on Friday of 42.05 feet. Image credit: NOAA Advanced Hydrologic Prediction Service/U.S. Geological Survey



Figure 3. Floodwaters from the Washita River inundate a bridge on State Highway 377 south of Tishomingo, OK. The nearby Cumberland Levee was breached on Sunday after being overtopped during the weekend, but the water was pouring into an unpopulated containment basin. Image credit: Tulsa District, U.S. Army Corps of Engineers.

Rains that jump ahead of tropical cyclones
Along with the downpours near its center, heavy rains also developed well northeast of Bill, as rich moisture was channeled ahead of the system along a frontal zone from Missouri to the Appalachians. While Bill’s center was still in Texas on Tuesday night and Wednesday morning, a large cluster of thunderstorms developed in south-central Missouri, which appears to have been an unusually early-in-the-season example of a predecessor rainfall event (PRE). A 2010 study led by Tom Galarneau (then at the University at Albany, State University of New York, and now at the National Center for Atmospheric Research) analyzed 28 PREs that occurred during the period from 1995 to 2008. On average, these PREs occurred about 600 miles downstream and about 36 hours ahead of a tropical cyclone’s central rain shield. PREs tend to occur when an east-west frontal zone is intersected by, and strengthened by, an influx of deep tropical moisture in the southerly flow ahead of a tropical cyclone. “The presence of tropical cyclone moisture can turn a heavy rain event into a record-breaking high-impact heavy rain event,” noted the authors. Most of the PREs analyzed by Galarneau and colleagues occurred in August and September, and they were most common with stronger hurricanes. However, a couple of early-season PREs were associated with Tropical Storm Alberto (June 12, 2006) in the Carolinas, and Hurricane Dennis (July 9, 2005) in Florida, Georgia, and South Carolina.

Here are some of the heaviest rainfalls in each state near or ahead of Bill, as reported by NOAA’s Weather Prediction Center on Sunday:

Texas: 12.50” (Montague)
Louisiana: 4.79” (Shreveport Regional Airport)
Oklahoma: 12.53” (3 miles E of Healdton)
Arkansas: 4.42” (2 miles SE of Rogers)
Kansas: 3.64” (Coffeyville Municipal Airport)
Missouri: 8.25” (4 miles WNW of Fordland)
Illinois: 5.14” (Cooks Mill)
Indiana: 6.72” (Grissom Air Force Base/Peru)
Kentucky: 3.54” (Henderson City)
Ohio: 5.11” (Lima/Allen County Airport)
Pennsylvania: 1.93” (Harrisburg/Capital City Airport)
West Virginia: 1.68” (Parkersburg/Wilson)
Virginia: 3.85” (Fort Belvoir/Davison Air Force Base)
District of Columbia: 2.37” (Reagan Washington National Airport)
Maryland: 2.50” (1 mile NNE of Cheltenham)

A quiet week ahead in the tropics
No major tropical developments are expected over the next several days, with wind shear relatively high across much of the deep tropics of the North Atlantic and North Pacific.

Thanks go to Sheldon Kusselson (NOAA/NESDIS) and Michael Lowry, Stu Ostro, and Greg Postel (The Weather Channel) for data, graphics, and perspective related to Bill.

Bob Henson


Figure 4. Visible satellite image of Bill’s circulation from around 7:00 pm CDT on Friday, June 19, when the center was close to the Mississippi and Ohio River confluence. Thunderstorms along an inflow band extended to northeast Texas and southwest Arkansas (see circle and Figure 5 below). Image credit: NOAA.


Figure 5. Stu Ostro (The Weather Channel) photographed these thunderstorms on Friday evening associated with a convergence band in the Arklatex region, well to the southwest of Bill’s center. Image credit: Stu Ostro.