Notable Characteristic of Tropical Storm Bill: It Lasted an Unusually Long Time Over Land

The National Hurricane Center initiated advisories on Tropical Storm Bill at 10 p.m. CDT Monday, June 15. Bill made landfall on Matagorda Island, Texas at 11:45 a.m. June 16.

Bill was then downgraded to a tropical depression at 1 a.m. June 17, but maintained its tropical depression status for more than three and a half days until 4 p.m. CDT Saturday, June 20, when it was finally downgraded to a post-tropical cyclone over eastern Kentucky. Heavy rain and flooding were the primary impacts in Bill's path.

(MORE: Tropical Storm Bill Recap)

Bill lasted for 96 hours, or four days, over land as a tropical storm or tropical depression. The time spent inland is based on the first synoptic point over land through the synoptic point when the system was designated as post-tropical. In this case the time spent inland was from 1 p.m. June 16 through 1 p.m. June 20.

Michael Lowry, hurricane specialist at The Weather Channel, went back through  records to 1970. Lowry did not include storms before the satellite era due to the difficulting in ascertaining tropical versus post-tropical classification. The data does not include the time any of the tropical cyclones reemerged briefly over water.

Based on Lowry's research,Tropical Storm Bill landed in a three-way tie for sixth place for the longest-lasting tropical cyclones inland. 

Bill also falls above the 95th percentile of long-lasting inland tropical cyclones since 1970. The data also suggests that a tropical cyclone will last 96 hours or longer once every 7.5 years.

"Interestingly the average life span of an inland tropical cyclone is only 36 hours based on the 1970-2014 record," said Lowry. "I would have expected it to be higher but that's really all a function of where it makes landfall, how much terrain it encounter, and at what point it gets mixed up in the mid-latitudes."

A few other interesting notes regarding the top six longest lasting tropical cyclones were that they were all tropical storms at their peak, with only one hurricane and, as expected, the biggest impact from them all was heavy rain and flooding.

The longest lasting inland tropical cyclone was an unnamed tropical storm in 1987 which persisted for nearly seven full days (August 9-17), with the exception of one point over the northern Gulf, post-landfall. Over 20 inches of rain was measured in Vancleave, Mississippi.

Second place goes to Tropical Storm Fay in August 2008 which lasted 138 hours and made eight landfalls, including four in Florida. Fay even became better defined on radar as it moved over Florida, a sign that the storm was strengthening despite being over land. 

Tropical Storm Claudette in July 1979 is tied for third place with 114 hours, or almost five full days, inland as a tropical storm or tropical depression. The center remained close to the coast, due to a blocking ridge of high pressure that formed to its north, so Claudette did not weaken. A new 24-hour rainfall record for the United States was set in Alvin, Texas where 42 inches of rain fell.

Hurricane Danny in July 1997, tied for third place with 114 hours, made its first landfall in Louisiana as a very small hurricane and then moved back over the Gulf of Mexico and strengthened before making another landfall in Alabama. Dauphin Island, Alabama measure 37.75 inches of rain from Danny.

In fifth place is Tropical Storm Alberto which made landfall near Destin, Florida, on July 3, 1994. Steering currents weakened, which allowed Alberto to slowly move across Alabama and Georgia, producing torrential rains.

Tied with Tropical Storm Bill for sixth place is Tropical Storm Jerry in 1995 which produced 18.51 inches of rain in Antreville, South Carolina after making landfall in southeast Florida and Tropical Storm Allison in 2001, which is the most costly tropical storm in U.S. history with $9 billion in losses.

(MORE: Houston May 2015 Flooding Compared to Tropical Storm Allison)

Allison made landfall in Texas on June 5 and then tracked as far inland as Lufkin, Texas on June 7 bringing heavy rain across the region.

Then, Allison began to move southward as a ridge over New Mexico strengthened just as the high off the Southeast flattened and moved southeastward. This setup brought incredible flooding to southeast Texas on June 7 and 8, with just over 40 inches at Moore Road Detention Pond in Jefferson County Texas and 36.99 inches falling at the Port of Houston.

Allison then moved back over the Gulf of Mexico making a second landfall in Louisiana before reintensifying over land as it tracked through Louisiana and Mississippi, even forming an eye feature during the morning of June 11, a rare accomplishment for a tropical cyclone over land. Ten inches of rain was even reported in northeast North Carolina and southeast Pennsylvania. 

Before Tropical Storm Bill made landfall there was mention of the "brown ocean" effect and how it could play a role in fueling Bill after it moved inland, given the high soil moisture over Texas from the record rain in May.

(MORE: Record Rain in May)

It is difficult to say conclusively at this point whether this was the case, but the moisture in the soil certainly did not hurt the ability for Bill to maintain its tropical characteristics.

MORE ON WEATHER.COM: Tropical Storm Bill June 2015 (PHOTOS)