PRECIPITATION |
Tropical Cyclones (TCs) frequently produce extreme precipitation. TC precipitation (TCP) accounts for a considerable portion of both total annual precipitation and extreme precipitation along the Atlantic and Gulf of Mexico coasts in United States [11,12,13]. TCP causes inland flooding that can result in significant economic damage and loss of life [14,15].
At a larger scale, there is an increasing trend in North Atlantics TCs’ contribution to both annual total rainfall and extreme rainfall events (i.e., top 5% of rainfall events) from 1979 to 2005 [16]. Kunkel et al. [13] reported that TC related extreme precipitation events in the eastern U.S. doubled during 1994-2008 as compared to the long-term (1895-2008) average. Knight and Davis [12] also showed that the TCP contribution to extreme precipitation increased during 1972 to 2007 due to increases in both storm frequency and intensity. Nogueica and Keim [17] found increasing trends in both annual TCP volume and affected area in the eastern U.S. since 1995, which are attributed to increases in TC frequency. Generally, these large-scale studies show increases in TCP in recent years, both in terms of extreme precipitation and the contribution to annual precipitation. Increases in TC frequency are responsible for much of this trend. However, there is no evidence of an increase in TC-related precipitation in Texas (based on 1950-2009) [18].
Generally, the front half and right side of the TC receive more frequent and intense precipitation than the rear half and the left side. The largest TCP events in Texas are associated with slow moving or stalled TC systems.
At a larger scale, there is an increasing trend in North Atlantics TCs’ contribution to both annual total rainfall and extreme rainfall events (i.e., top 5% of rainfall events) from 1979 to 2005 [16]. Kunkel et al. [13] reported that TC related extreme precipitation events in the eastern U.S. doubled during 1994-2008 as compared to the long-term (1895-2008) average. Knight and Davis [12] also showed that the TCP contribution to extreme precipitation increased during 1972 to 2007 due to increases in both storm frequency and intensity. Nogueica and Keim [17] found increasing trends in both annual TCP volume and affected area in the eastern U.S. since 1995, which are attributed to increases in TC frequency. Generally, these large-scale studies show increases in TCP in recent years, both in terms of extreme precipitation and the contribution to annual precipitation. Increases in TC frequency are responsible for much of this trend. However, there is no evidence of an increase in TC-related precipitation in Texas (based on 1950-2009) [18].
Generally, the front half and right side of the TC receive more frequent and intense precipitation than the rear half and the left side. The largest TCP events in Texas are associated with slow moving or stalled TC systems.
What impacts precipitation and inland flooding?
Tropical cyclones (TC) are one of the primary causes of severe riverine flooding in Texas [19,20]. Many of the recent TCs with more than a billion dollars in losses have made landfall near Houston (e.g., Tropical Storm Allison, Hurricane Rita, and Hurricane Ike) (http://www.ncdc.noaa.gov/billions/).
Riverine flooding is a hazard that causes major destruction and loss of life in the United States [21]. Texas is a state that has been frequently influenced by severe riverine flooding [19,22]. The rapid urbanization in this region has also increased its vulnerability to riverine floods [23],[24]. Past studies about TC precipitation and flooding have focused on the historical patterns and trends in extreme precipitation and discharge for all of Texas [19,25] or have focused on just one watershed [23]. Although the Houston area is frequently influenced by TCs [18], few studies have examined the impact of tropical cyclone precipitation (TCP) on discharge and flooding in watersheds near Houston.
Many TC systems travel towards the north and west after landfall. Typically TCP intensity gradually decreases as the TC moves inland. However, sometimes TC re-intensify because of interactions with other weather systems or local conditions. These inland TCP events can generate large amounts of precipitation in western and northern Texas, such as the >500 mm/day of TCP that fell in western Texas from Hurricane Alice (1981), or the clusters of TCP extremes (~250 mm/day) in northern Texas associated with TS Dean (1995) and TS Erin (2007). Antecedent soil moisture conditions are one of the factors that led to the re-intensification of TS Erin (2007) [26].
In other cases inland TCP maxima are associated with TCs that become stalled due to weak steering winds or interactions with mid-latitude weather systems (TS Claudette in 1979 and TS Delia in 1973). Other TCs that generated extreme amount of precipitation did so because they reversed course (TS Alison in 2001 and Hurricane Beulah in 1967). TS Claudette and TS Alison are associated with the record daily TCP in Texas (~1000 mm) and the heavy precipitation and slow movement caused major inland flooding.
Riverine flooding is a hazard that causes major destruction and loss of life in the United States [21]. Texas is a state that has been frequently influenced by severe riverine flooding [19,22]. The rapid urbanization in this region has also increased its vulnerability to riverine floods [23],[24]. Past studies about TC precipitation and flooding have focused on the historical patterns and trends in extreme precipitation and discharge for all of Texas [19,25] or have focused on just one watershed [23]. Although the Houston area is frequently influenced by TCs [18], few studies have examined the impact of tropical cyclone precipitation (TCP) on discharge and flooding in watersheds near Houston.
Many TC systems travel towards the north and west after landfall. Typically TCP intensity gradually decreases as the TC moves inland. However, sometimes TC re-intensify because of interactions with other weather systems or local conditions. These inland TCP events can generate large amounts of precipitation in western and northern Texas, such as the >500 mm/day of TCP that fell in western Texas from Hurricane Alice (1981), or the clusters of TCP extremes (~250 mm/day) in northern Texas associated with TS Dean (1995) and TS Erin (2007). Antecedent soil moisture conditions are one of the factors that led to the re-intensification of TS Erin (2007) [26].
In other cases inland TCP maxima are associated with TCs that become stalled due to weak steering winds or interactions with mid-latitude weather systems (TS Claudette in 1979 and TS Delia in 1973). Other TCs that generated extreme amount of precipitation did so because they reversed course (TS Alison in 2001 and Hurricane Beulah in 1967). TS Claudette and TS Alison are associated with the record daily TCP in Texas (~1000 mm) and the heavy precipitation and slow movement caused major inland flooding.
Acknowledgements & Credits: Click here for literature cited in this section, "Hurricane Impacts." This material is based upon work supported by the Texas Department of Public Safety's Division of Emergency Management. Background photo courtesy of Mark Moran (Creative Commons license CC BY 2.0)
© 2019 Jennifer L. Irish & Steven M. Quiring. All rights reserved.
© 2019 Jennifer L. Irish & Steven M. Quiring. All rights reserved.