Hurricanes: Wind, rain, and storm surge

Chapter 28

Hurricanes: Wind, rain, and storm surge Wossenu Abtew Water and Environment Consulting, Boynton Beach, FL, United States

28.1 Introduction

28.2

Tropical systems develop as tropical waves, depressions, tropical storms, and hurricanes. According to the National Hurricane Center, a tropical system originates in the tropical and subtropical region. It is a rotating organized system of clouds and thunderstorms that has a closed low-level circulation. Tropical systems rotate counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. Tropical systems are classified based on sustained wind speed that they generate (Table 28.1). According to Chaston (1996), tropical systems transport heat energy, moisture, and momentum from the tropics to the poles to decrease the temperature differential to maintain the current climate of the Earth. Tait (1995) reported an average of 9.4 subtropical storms, tropical storms, and hurricanes annually in the North Atlantic Ocean between 1886 and 1994 where 4.9 of them were hurricanes. Williams and Duedall (1997) reported a fewer number, 1000 tropical storms in the North Atlantic, Caribbean Sea, and Gulf of Mexico in 126 years (1871– 1996), an average of 7.9 storms in a year. In the last 20 years the average number of tropical storms and hurricanes in the North Atlantic, Caribbean Sea, and Gulf of Mexico was 13.8 with 6.8 being hurricanes, far higher than the historically reported (Fig. 28.1). The costliest storms that hit the US mainland in recent years are presented in Table 28.2. The costliest of all the years is 2017 with total cost of 175 billion dollars between Hurricane Harvey (Texas) and Hurricane Irma (Florida). Hurricane Irma and Hurricane Maria devastated Porto Rico and other Caribbean islands. Hurricane Nate (Louisiana, Mississippi, and Alabama) also incurred damage in 2017. The distribution of tropical systems, excluding tropical depressions, from 1906 through 2006, is shown in Fig. 28.2. On an average 82% of the tropical storms and hurricanes occur from the beginning of August through the end of October. The official hurricane season is June 1 through November 30, although in few instances storms have developed in every month through February.

Tropical systems contribute a considerable percent of South Florida rainfall depending on the number, type of storm, time of occurrence, and path of tropical storms (Walther and Abtew, 2006). Additionally, rainfall from these systems had ended severe regional droughts. For example, a tropical storm dropped more than 25 cm of rainfall over the Miami area at the end of August during the 1932 severe drought. Passage of Tropical Storm Dawn in September 1972 brought much needed rainfall to South Florida during the 1971–72 drought. Similarly, Hurricane Dennis passed through South Florida in 1981 as a tropical storm and contributed over 51 cm of needed rainfall during a severe drought. In July 1985, Hurricane Bob also contributed to South Florida rainfall as a tropical storm in a drought year. Hurricane Keith made landfall as a tropical storm in the upper portion of South Florida in November 1988 and deposited over 27 cm of rainfall in the severe drought year. The 2000–01 severe drought effect was minimized due to 15 cm of rainfall from Hurricane Gabrielle in the Kissimmee area of South Florida. Large spatial coverage and high runoff volumes are typical characteristics of rainfall associated with tropical systems. The severe drought of 2007 in South Florida was eased by significant rainfall contribution from Tropical Storm Barry in June 2007 and Tropical Storm Faye in August 2008. Reported drought years in South Florida are 1932, 1955–57, 1961–63, 1971–72, 1973–74, 1980–82, 1985, 1988–89, 1990, 2000–01, 2006–07, and 2011–12 (Abtew and Huebner, 2002; Abtew et al., 2009a, 2012). Other parts of the United States such as Texas have benefited from tropical system rain to break persistent drought moisture deficit. Tropical system rainfall is one of the main causes of damages to infrastructure and life. Two characteristics of tropical system rainfall are high intensity and high volume as a result of large spatial coverage and rainfall generation mechanism. It overwhelms drainage systems and flooding is common with these events. The amount of rainfall from a tropical system depends on its relative path to the area of concern, size of storm, and forward speed. Steering wind,

Extreme Hydrology and Climate Variability. https://doi.org/10.1016/B978-0-12-815998-9.00028-2 © 2019 Elsevier Inc. All rights reserved.

Rainfall from tropical systems

367

368 Extreme hydrology and climate variability

TABLE 28.1 Tropical systems Saffir-Simpson classification by wind speed Classification

Wind speed (km h21)

Tropical depression

63

Tropical storm

63–118

Hurricane

119–153

1

154–177

2

178–209

3

210–250

4

250

5

Major hurricane

Category

high-pressure barrier, cold fronts, and other atmospheric conditions can accelerate or slow the forward speed, steer storm direction, affecting the amount of rainfall that a storm generates as found in the case of Hurricane Wilma in 2005 and Hurricane Harvey in 2017. Hurricane Harvey on August 30, 2017 dumped a record 132 cm of rainfall in Houston, Texas, causing catastrophic large-scale flooding resulting in the loss of life, massive displacement, and billions of dollars of property losses (Fig. 28.3). According to NOAA, a week upper level wind that failed to steer the storm and a high-pressure system to the north blocking the path resulted in the hurricane staying

FIG. 28.1 Tropical storms, hurricanes, and major hurricanes (1997–2017).

longer in the area for several days. Although spatial coverage of tropical systems rainfall is wide, spatial distribution varies with some spots getting extremely heavy rainfall as found during Hurricanes Harvey (August 25–30, 2017) in Southeast Texas (Fig. 28.3), and Irma (September 9–11, 2017) in South Florida (Fig. 28.4).

28.3

Hurricane wind and storm surge

Hurricanes generate high-velocity winds with catastrophic damage to infrastructure from wind impact and storm surge. Hurricane winds affect water management infrastructure in many ways. Waves generated in impoundments can damage earthen levees through wave erosion and overtopping. Levee breach or overtopping may result in loss of human life and property damage downstream. In South Florida, hurricane-generated waves in Lake Okeechobee resulted in 392 and 2700 fatalities in 1926 and 1928, respectively (Bromwell et al., 2006). In 1947 and 2005, the dike around Lake Okeechobee experienced significant levee erosion from hurricane-generated wave setup and storm surge. Water control structure and canal performance is decreased due to vegetation and other debris accumulation from hurricane activity. Of all the hurricanes that affected South Florida during the 2004 and 2005 hurricane seasons, Hurricane Wilma (October 24, 2005) produced the most damage to the Herbert Hoover Dike of Lake Okeechobee (Abtew and Iricanin, 2008).

Hurricanes: Wind, rain, and storm surge Chapter 28

369

TABLE 28.2 The costliest tropical storms that impacted the US mainland Rank

Tropical system (impacted region)

Year

Category

Damage (US $ in billions)

1

Harvey (TX)

2017

4

125

2

Katrina (SE FL, LA, MS)

2005

3

125

3

Sandy

2012

1

50

4

Irma (FL, Key West)

2017

4

50

5

Ike (TX, LA)

2008

2

30

6

Andrew (SE FL, LA)

1992

5

27

7

Ivan (AL, NW FL)

2004

3

20.5

8

Wilma (S FL)

2005

3

19

9

Rita (SW LA, N TX)

2005

3

18.5

10

Charley (SW FL)

2004

4

16

11

Irene (Mid Atlantic and NE US)

2011

1

13.5

12

Mathew

2016

1

10

13

Frances (FL)

2004

2

9.8

14

Allison (N TX)

2001

TS

8.5

15

Jeanne (FL)

2004

3

7.5

16

Hugo (SC)

1989

4

7

17

Floyd (Mid-Atlantic NE US)

1999

2

6.5

18

Gustav (LA)

2008

2

6

19

Isabel (Mid-Atlantic)

2003

2

5.5

20

Fran (NC)

1996

3

5

21

Opal (NW FL AL)

1995

3

4.7

22

Alicia (N TX)

1983

3

4

23

Georges (FL Keys MS AL)

1998

2

2.5

24

Isaac (LA)

2012

1

2.8

25

Dennis (NW FL)

2005

3

2.55

Source: National Hurricane Center.

Hurricane Wilma formed as a tropical depression on October 15, 2005, east-southeast of Grand Cayman islands in the Atlantic. In 3 days, Wilma became a hurricane moving west-northwestward strengthening to a Category 5 hurricane, with a record low pressure (882 mb) for an Atlantic hurricane. On October 21, it made landfall on the island of Cozumel, Mexico, as a Category 4 hurricane. On October 22, Wilma crossed to the Yucatan Peninsula after devastation and emerged in the Gulf of Mexico on October 23, 2005. It headed toward South Florida making landfall as a Category 3 hurricane near Cape Romano on October 24 and crossed South Florida as a Category 2 hurricane, crossing to the Atlantic in 4½ h (Pasch et al., 2006). The eye of Hurricane Wilma passed south of Lake Okeechobee

inflicting extensive damage from the front end and back end of the hurricane with wind gust speeds higher than 180 km h 1 (Figs. 28.5 and 28.6). Most of the rainfall from the hurricane was on the headwaters of Lake Okeechobee and the southwest. Because the hurricane crossed South Florida quickly, rainfall was not extreme. But the location of the high rainfall, the amount of runoff generated, and the high antecedent water levels in lakes and impoundments impacted the water management system hydraulically, structurally, and environmentally. Hurricane Wilma passed over the six stormwater treatment areas (STAs), constructed wetlands, at the south and southeastern edges of the Everglades Agricultural Area.

370 Extreme hydrology and climate variability

FIG. 28.2 North Atlantic tropical storms from 1906 to 2006 (Abtew and Iricanin, 2008).

FIG. 28.3 Rainfall estimates from Hurricane Harvey (August 25–30, 2017). Source: NOAA (edited).

The STAs were impacted significantly. The impacts included resuspension of settled sediment, vegetation damage, dislocation of wetland vegetation and pushing vegetation onto levee banks, loss of power, and levee and pump station damages. The downed power lines on levees and roads also limited access to facilities. In the Upper Kissimmee Basin, Lakes Myrtle, Mary Jane, Gentry, Tohopekaliga, and Kissimmee were above regulation schedule following Hurricane Wilma, which generated over 15 cm of areal average rainfall over the basin. Inflow into Lake Okeechobee through the Kissimmee River

(S-65E) between October 24, 2005 (landfall of Hurricane Wilma) and December 31, 2005 was 648 million m3. Kissimmee River floodplain water levels at the restoration area climbed over 2 m due to increase in surface water flow from the hurricane rainfall. Lake Okeechobee was fully impacted by Hurricane Wilma. Lake Okeechobee is impounded with an earthen levee, except at Fisheating Creek, where there is an open water connection. The lake has numerous inflow and outflow water control structures. The impact zones of wind-generated high waves on Lake Okeechobee depend

cm

28.5N

FIG. 28.4 Rainfall contribution to South Florida from hurricane Irma, 21 cm (September 9–11, 2017).

75 60

28N

50 40 27.5N

30 25

27N

20 15 10

26.5N

8 5

26N

4 3

25.5N

1 25N

82.5W

82W

81.5W

81W

80.5W

80W

79.5W

FIG. 28.5 Hurricane Wilma atmospheric pressure, maximum gust, and average wind speed at Belle Glade Station south of Lake Okeechobee.

372 Extreme hydrology and climate variability

FIG. 28.6 Hurricane Wilma direction and gust wind speed over South Florida (10:30 a.m. October 24, 2005), Abtew and Iricanin (2008).

on the path of the hurricane, wind speed, wind direction, and duration of impact. There are four weather stations within Lake Okeechobee. Of these, three weather stations (except for L005) had gust wind speed, average wind speed, and wind direction data collected during Hurricane Wilma. Weather station L001, at the northern side of the lake, registered instantaneous maximum gust wind speed of 172 km h 1; weather station L006, at the south side of the lake, registered instantaneous maximum gust wind speed of 180 km h 1. Wind speed and direction over the lake correspond with the area of levee erosion and high water levels. The wind direction over the lake is clearly shown as eastnortheast (ENE) from the front side of the hurricane and northwest (NW) from the backside of the hurricane (Fig. 28.6). Both the gust and average wind-speed data show that the backside of the hurricane had higher wind speed than the front side. Damage to levee was at the southeastern side of the lake where highest gust wind speed is shown (Fig. 28.6). Hurricane winds blow vegetation from the lake

toward the levee banks. Water control structures built on the levees get clogged with massive vegetation and debris impeding emergency operations. The wind wave action stirred up the lake, thereby resuspending settled sediment and impacting water quality. High sediment concentration reduced the depth of light penetration into water, reducing the growth and maintenance of submerged aquatic vegetation. High sediment concentration is associated with increase in nutrient concentration. Due to the high water level in the lake, water had to be discharged. The quantity and quality of the discharge impact the receiving estuarine systems. Structural damage from hurricanes can occur in several ways. High rainfall on the lake’s watershed from hurricanes results in high surface water inflows. This results in rising water level in the lake where outflow conveyance capacity is lower than inflow conveyance capacity. High water level in the lake increases seepage through the levee, which could result in levee failure. Hurricane winds can generate high waves, and the energy from the back-and-forth battering of an earthen levee can result in cutting the levee. Also, failure can occur around structures on the levee. High water level creates the potential for high wind to generate high waves that could wash the lakeside of the levee, or even overtop and erode the outside of the levee. At the time, normal Lake Okeechobee operation is below 5.03 m National Geodetic Vertical Datum (m NGVD29); 5.03– 5.33 m NGVD29 elevation initiates levee inspection at intervals of 7–30 days, varying by reach. Water levels of 5.33–5.64 m NGVD29 initiate inspection at intervals of 1–7 days and levels >5.64 m NGVD29 initiate daily inspection. Seepage is the slow movement of water from the lake through the levee due to the hydrostatic force created by high water level in the lake. Seepage is an inherent problem of earthen dams. When the rate of seepage increases, soil material moves through the levee along with the seepage water (i.e., boiling). Boiling starts with fine material movement followed by course material movement and results in levee breach. It was reported that there will be problems when the stage approaches 5.64 m NGVD29 and levee breach is likely expected at 6.4 m NGVD29. Also, increased flow rates from high rainfall can create failure at a water control structure. High rainfall can create earthen levee erosion from rainfall impact. There were five or six eroded areas along the lakeshore after Hurricane Wilma. If the wave setup exceeds the height of the levee, then washout could occur to the lakeside, top, and outer side of the levee. The wave run-up from Hurricane Wilma exceeded the maximum reading capacity of some of the water level recorders on the perimeters of Lake Okeechobee. Estimates of highest level of wave setup were made from watermark manually marked at the time at a structure on southern side

Hurricanes: Wind, rain, and storm surge Chapter 28

373

6.5

S133_T

6

S4_T

Lake water level (m NGVD29)

5.5

5

4.5

4

3.5

3

2.5

23:37

22:52

22:07

21:22

20:37

19:52

18:52

18:07

17:22

16:37

15:52

15:07

14:22

13:37

12:52

12:07

11:22

9:52

10:37

9:07

8:22

7:37

6:52

6:07

5:22

4:07

3:07

2:22

1:37

0:52

0:07

2

Time of day (October 24, 2018)

FIG. 28.7 Lake Okeechobee drawdown from wind side and wave setup on opposite side from Hurricane Wilma.

of the lake. The initial estimate before surveying was 7.92 m NGVD29 as water is pushed from the incoming wind side to the opposite side (Fig. 28.7). Hurricane Wilma’s impact on Lake Okeechobee is not limited to the impact during the hurricane. Runoff associated with the hurricane rainfall has lingering impact on the lake. Lake Okeechobee water level rose following Hurricane Wilma. Rise in lake stage results in high-rate discharge to manage the lake water level. The hurricane moved quickly through the area. Slow movement of the hurricanes might have had extensive hydrologic impact that would have included large-scale flooding. Fig. 28.8 depict damage to the Herbert Hoover dike of Lake Okeechobee. Lake Okeechobee is over 1760 km2 in surface area with a high risk of dam breach that would affect towns around the lake, vast sugarcane production and other agriculture, and businesses.

28.4 Hurricanes, global warming, and climate teleconnections 28.4.1

Global warming

Recent increase in hurricane intensities and ferocity of damage brings to the forefront the relationship of global warming and tropical systems. The 2017 three major hurricanes (Harvey, Irma, and Maria) that hit the Caribbean

islands and the United States, intensity, and damage raised climate change association. According to Trenberth (2005), global vapor column over the oceans has been increasing at a rate of 1.3% per decade in line with increase in sea surface temperature (SST). Both increase in temperature and water vapor are favorable for convective systems. Bender et al. (2010), applying downscaling strategy that uses hurricane-prediction model, predicted an increase in the number of high-intensity hurricanes, Categories 4 and 5, in Western Atlantic north of 20°N. They acknowledged that other model outputs have reported a decrease in hurricane activity with global warming without addressing change in intensity. From observed data statistical analysis and GFDL CM2.1 climate model application, link was made between inter-decadal variability in Atlantic SST (AMO) and India and Sahel summer rainfall, and Atlantic hurricanes (Zhang and Delworth, 2006). Warm phase of the AMO is positively related to increase in India and Sahel summer rainfall and Atlantic hurricane activity. When the AMO is in cold phase, vertical shear reduces hurricane activity.

28.4.2

Climate teleconnection

El Nin˜o Southern Oscillation (ENSO) relation to Atlantic and Caribbean tropical system development and path is that El Nin˜o condition reduces the number of storms and steer

374 Extreme hydrology and climate variability

FIG. 28.8 Wave erosion damage to the Herbert Hoover Dike of Lake Okeechobee from Hurricane Wilma in October 2005 (Bromwell et al., 2006; Abtew and Iricanin, 2008).

FIG. 28.9 Number of most named storms since 1851 and ENSO events. Storm numbers data source: https://www.wunderground.com/hurricane/top10.asp

the path away from continental United States. La Nin˜a conditions are favorable for tropical system development and likely landfall. El Nin˜o condition creates atmospheric shear that weakens and diverts tropical storms. From the top 20 costliest storms, 14 were during La Nin˜a and neutral ENSO conditions as determined by cumulative SST index (Abtew et al., 2009b; Abtew and Trimble, 2010). Of the 15 top most named storm years since 1851, 11 were mostly during La Nin˜a and neutral ENSO events (Fig. 28.9, Table 28.3). Of

the 10 top most hurricane years since 1851, eight were during La Nin˜a and neutral ENSO events (Fig. 28.10, Table 28.3). Of the eight top most major hurricane years since 1851, seven were during La Nin˜a and neutral ENSO events (Fig. 28.11, Table 28.3). It is most likely that Atlantic and Caribbean storms to be more in number and high in impact during La Nin˜a and neutral years and less in El Nin˜o years. Figs. 28.12 and 28.13 present examples of both cases.

Hurricanes: Wind, rain, and storm surge Chapter 28

375

TABLE 28.3 Most number of storms, hurricanes, and major hurricanes since 1851 Year

No. of Storms

Year

No. of hurricanes

Year

No. of major hurricanes

2005

28

2005

15

1950

8

1933

20

2010

12

2005

7

2012

19

1969

12

1955

6

2011

19

1887

11

1999

6

2010

19

1950

11

1964

6

1995

19

1998

11

1961

6

1887

19

1995

11

1998

6

1969

18

2012

10

1926

6

2008

16

1933

10

2003

16

1916

10

1936

16

2007

15

2004

15

2001

15

2000

15

Storm numbers data source: https://www.wunderground.com/hurricane/top10.asp

FIG. 28.10 Number of most hurricanes since 1851 and ENSO events. Storm numbers data source: https://www.wunderground.com/hurricane/top10.asp

FIG. 28.11 Number of most major hurricanes since 1851 and ENSO events. Storm numbers data source: https://www.wunderground.com/hurricane/ top10.asp

FIG. 28.12 Fewer number of storms and path of storms away from land during a strong El Nin˜o year of 1997 (NHC).

Hurricanes: Wind, rain, and storm surge Chapter 28

377

FIG. 28.13 Higher number of storms and path of storms toward landfall during a strong La Nin˜a year of 2011 (NHC).

28.5 Summary Tropical systems are major natural forces that impact regions physically, hydrologically, and ecologically impacting mainly coastal areas and island regions. In some cases, they can move inland and contribute large volume of rain with reduced wind impact. This chapter presents mainly Atlantic hurricanes with specific details of known hurricane events and their interaction and impact on landfall on the US mainland. The 25 costliest storms that hit United States in the past three decades are presented. The relationship between El Nin˜o Southern Oscillation phenomena and Atlantic tropical systems development is presented with likelihood of occurrence. Since 1851, 73% of the most number of storm years, and most number of hurricane years were during La Nin˜a and Neutral ENSO years, with only 23% in El Nin˜o years. Seven out of eight number of major hurricane years occurred in La Nin˜a and neutral ENSO years. Only one was during an El Nin˜o year showing that El Nin˜o years have fewer storms than La Nin˜a and neutral years. Tropical systems are hydrologically essential in

breaking droughts and replenishing surface and groundwater storage.

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378 Extreme hydrology and climate variability

Abtew, W., Pathak, C., Ciuca, V., 2012. Regional Hydrology. In: 2012 South Florida Environmental Report—Volume I. South Florida Water Management District, West Palm Beach, FL. Bender, M.A., Knutson, T.R., Tuleya, R.E., Sirutis, J.J., Vecchi, G.A., Garner, S.T., Heid, I.M., 2010. Modeled impact of anthropogenic warming on the frequency of intense Atlantic hurricanes. Science 308, 454. https://doi.org/10.1126/science.1180568. Bromwell, L.G. Dean, R.G., Vick, S.G., 2006. Report of expert review panel technical evaluation of Herbert Hoover Dike Lake Okeechobee, Florida. Prepared for South Florida Water Management District. BCI Engineers and Scientists, Lakeland, Florida. Chaston, P.R., 1996. Hurricanes. Chaston Scientific, Inc., Kearney, MO. Pasch, R.J., Blake, E.S., Cob III, H.D., Roberts, D.P., 2006. Tropical Cyclone Report Hurricane Wilma. NHC, Miami, FL.

Tait, L.S., 1995. Hurricanes … Different faces in different places. The 17th annual National Hurricane Conference held in Trump Taj Mahal, Atlantic City, NJ, on April 11–14, 1995. Trenberth, K., 2005. Uncertainty in hurricanes and global warming. Science 308, 1753. https://doi.org/10.1126/science.1112551. Walther, S., Abtew, W., 2006. Contribution of Rainfall From Tropical Systems in South Florida From 1871–2005. Environmental Resources Assessment Department, South Florida Water Management District, West Palm Beach, FL. Williams, J.M., Duedall, I.W., 1997. Florida Hurricanes and Tropical Storms. FL. University Press of Florida, Gainesville. Zhang, R., Delworth, T.L., 2006. Impact of Atlantic multidecadal oscillation on India/Sahel rainfall and Atlantic hurricanes. Geophys. Res. Lett. 33(17). https://doi.org/10.1029/2006GL026267.