United States tropical cyclone rainfall climatology

From Wikipedia, the free encyclopedia

All tropical cyclone tracks between the years 1985 and 2005.

1 Long term averages
2 Top Ten Tropical Cyclones Amounts By Point Maximum for the Lower 48 since 1976
3 Maximum tropical cyclone rainfall per state for the Lower 48
4 Average and Record Statistics Per Time Frame For the Lower 48
5 See Also
6 References
7 External Links

[edit] Long term averages

On average, five tropical cyclones or their remnants lead to rainfall across the contiguous United States each year, contributing around a quarter of the annual rainfall to the southern United States. While many of these storms form in the Atlantic Basin, some systems or their remnants move through Mexico from the Eastern Pacific Basin. The average storm total rainfall for a tropical cyclone impacting the lower 48 from the Atlantic Basin is about 16 inches/406 mm, with 70-75 percent of the storm total falling within a 24 hour period.

[edit] Top Ten Tropical Cyclones Amounts By Point Maximum for the Lower 48 since 1976

Below is a list of the top ten highest storm total rainfall amounts from individual tropical cyclones across the lower 48 since 1976. Much of the rainfall information was provided by the National Climatic Data Center in Asheville, North Carolina.

Allison Flooding in Houston

1219 mm/48.00 inches Amelia 1978
1143 mm/45.00 inches Claudette 1979
1033 mm/40.68 inches Allison 2001
977 mm / 38.46 inches Georges 1998
932 mm / 36.71 inches Danny 1997
707 mm / 27.85 inches Alberto 1994
652 mm / 25.67 inches Allison 1989
649 mm / 25.56 inches Dennis 1981
635 mm / 25.00 inches T.D. #1 1992
611 mm / 24.06 inches Floyd 1999^[1]

[edit] Maximum tropical cyclone rainfall per state for the Lower 48

See also: List of wettest tropical cyclones in the United States

U.S. tropical cyclone rainfall maxima per state

State maxima relating to tropical cyclones and their remnants are shown on the left, color coded by amount. Tropical cyclones from the Atlantic Basin have the most sway along the Gulf coast and Eastern Seaboard. The impact of tropical cyclones and their remnants originally from the eastern Pacific stretches as far east as Michigan and Indiana. It should be stated that rainfall related to the low pressure area once associated with a tropical cyclone, or its remnants aloft, are included in this sample. No additional rainfall from pre-existing upper lows as seen before cyclones such as Hurricane Fran of 1996 or from upper cyclones that closed off behind former tropical cyclones such as Hurricane Juan of 1985 was included.

The state of Texas has the highest amounts, followed by Florida, Alabama, and Mississippi. This is due to the fact that over the 31 year sample, the storms that have become quasi-stationary like 2001's Tropical Storm Allison, 1978's Tropical Storm Amelia (1978), and Hurricane Danny (1997) are dominating the statistics. Out West, the same can be said for Hurricane Kathleen (1976) and the remains of Hurricane Olivia of the 1982 Pacific hurricane season. As the United States tropical cyclone rainfall climatology works back earlier into the 1970s, the amounts across the West and the Upper Ohio Valley are likely to increase due to the influence of Hurricane Agnes of 1972 and Hurricane Eloise in 1975. Data from the 1950s will increase amounts in New England.

U.S. Tropical Cyclone Rainfall Accumulations per time frame

[edit] Average and Record Statistics Per Time Frame For the Lower 48

To the right is a graphic showing averages and extremes for a 15 year sample of tropical cyclones and their remnants affecting the contiguous United States. The units of the rainfall amounts are in inches, while the time units are in hours. The bars in the graph express the percent of the storm total rainfall, which is defined to be 100 percent in the final column. Note that, on average, as much as one-fourth of the total occurs in 2-3 hours, while half falls within 12 hours, and almost three-quarters of the storm total falls within a 24 hour period. Cases where a cyclone scraped the coast were not separated out from those that made a more direct landfall. Also, Pacific and Atlantic cases were not separated. This all explains the average storm total of the sample being depressed to 338.8 mm/13.34". On the bottom of the graphic are listed the averages per time frame and the records. The records were mainly set during Tropical Storm Allison (2001) and Hurricane Danny (1997). This graphic will be updated as the climatology pushes farther back in time.^[2]