Chapter 11 Hurricanes

Transcription

1 Natural Disasters Tenth Edition Chapter 11 Hurricanes Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-1

2 Hurricanes Large tropical cyclones Heat engines converting heat of tropical ocean into winds, waves Generate winds over 240 km/hr Push massive amounts of water onshore as surges, up to 6 m over sea level Heavy rains cause dangerous floods well away from coastlines Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-2

3 Figure 11.3 Hurricanes Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-3

4 How a Hurricane Forms (1 of 3) Means of transporting excess tropical heat to mid-latitudes Requirements for development of hurricane: Seawater at least 27 o C (80 o F) in upper 60 m Air must be warm, humid and unstable Weak upper-level winds, preferably blowing in same direction as developing storm is moving Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-4

5 How a Hurricane Forms (2 of 3) Begins with tropical disturbance: low-pressure zone drawing in cluster of thunderstorms with weak surface winds Converging surface winds flow up central core (like chimney) sending warm, moist air into stratosphere Rising moist air cools to dew point temperature, condenses and releases latent heat Released heat warms surrounding air stronger updrafts increased rate of upward flow of warm, moist, surface air When winds exceed 63 km/hr: tropical storm When winds exceed 119 km/hr: hurricane Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-5

6 How a Hurricane Forms (3 of 3) Storm becomes tropical depression (receives identifying number): Surface winds strengthen and flow around and into core Rotates counterclockwise (in Northern Hemisphere) Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-6

7 Figure 11.4 Hurricane Katrina grows in strength moving over unusually warm seawater Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-7

8 Figure 11.5 How a Hurricane Forms Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-8

9 How a Hurricane Works (1 of 3) The Eye As more wind blows into center of tropical storm, difficult for all wind to reach center spiraling upward cylindrical wind mass in center of storm When surface-wind speeds reach about 119 km/hr, none of wind reaches center calm clear eye Inside eye: Cool, high-altitude air sinks and absorbs moisture Eye wall: Cylinder-shaped area of spiraling upward winds around eye Strongest winds Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-9

10 How a Hurricane Works (2 of 3) The Eye Eddies of storm sucked up into eye wall and stretched vertically caused winds on one side of 130 mph + 80 mph = 210 mph, and winds on other side of 130 mph 80 mph = 50 mph Same phenomenon occurs on different sides of storm: one side experiences wind speed + travel speed of hurricane, other side experiences wind speed travel speed of hurricane Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

11 How a Hurricane Works (3 of 3) Hurricane Energy Release Transfers heat from tropical seas to core of hurricane Huge amounts of latent heat released as air rises Generates energy at 200 times greater rate than worldwide electricity-generating capacity Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

12 Figure Energy Flow within a Hurricane Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

13 Figure How a Hurricane Works Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

14 Hurricane Origins (1 of 3) Differences from high-latitude storms: Main energy source is latent heat released by water vapor condensation Weakens rapidly when moves onto land Not associated with fronts Weaker high-altitude winds stronger hurricane Hurricane winds weaken with height Air in center of eye sinks downward Different names in different parts of the world: Indian Ocean: cyclones Western Pacific Ocean: typhoons Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

15 Hurricane Origins (2 of 3) Form on west sides of oceans where warm water is concentrated Also off Pacific coast of Mexico area of warm water isolated from cold California current by bend in coastline Not off coast of Brazil Atlantic Ocean is too narrow, not enough warm water Form between 5 o to 20 o latitude, travel to higher latitudes Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

16 Hurricane Origins (3 of 3) Do not form along equator because Coriolis effect is zero Can not cross equator once formed lose rotation Average of 84 tropical cyclones (hurricanes, typhoons, cyclones) form each year About 10 in north Atlantic Ocean, Caribbean Sea, Gulf of Mexico Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

17 Figure Hurricane Origins Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

18 Hurricane Damage Potential Strength assessed by Saffir-Simpson scale Category 1: wind damages trees and unanchored mobile homes Category 2: winds blow down trees, major damage to mobile homes, some roofs Category 3: winds blow down large trees, strip foliage, destroy mobile homes, damage small buildings Category 4: all signs blown down, heavy damage to buildings, major damage to coastal buildings, flooding extends inland Category 5: severe damage to buildings, major damage to buildings less than 5 m above sea level and within 500 m of shoreline, small buildings overturned and blown away Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

19 TABLE 11.1 Saffir-Simpson Hurricane Damage Potential Scale Barometric Pressure (millibars) Barometric Pressure (inches) Wind Speed (km/hr) Wind Speed (mph) Storm surge (meters) Storm surge (feet) Damages Category Over Minimal Category Moderate Category Extensive Category Extreme Category 5 <920 Less than >250 Over 155 >5.5 Over 18 Catastrophic Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

20 North Atlantic Ocean Hurricanes From 851 to 2006: U.S. Gulf and Atlantic coastlines hit by 279 hurricanes, three category 5 and 18 category 4 Most form in late summer when sea surface temps are warmest Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

21 Table 11.3 North Atlantic Tropical storms and Hurricanes, Category Maximum (Frequency (Year)) Minimum (Frequency (Year)) Tropical Storms and Hurricanes 28 (2005) 4 (1983) Hurricanes 15 (2005) 2 (2013) Major hurricanes (Winds > 110 mph) U.S. landfalling tropical storms and hurricanes 8 (1950) 0 many times (e.g., 2013) 8 (1916) 1 many times (e.g., 1997) U.S. landfalling hurricanes 6 (1985, 2004, 2005) 0 many times (e.g., 2013) U.S. landfalling major hurricanes 4 (2005) 0 many times (e.g., 2014) Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

22 North Atlantic Ocean Hurricanes: Cape Verde-type Hurricanes Usually begin as easterly waves moving west away from Africa May gain tropical storm status near Cape Verde Islands Blown westward with trade winds, gaining energy from warm seawater Movement curves northward due to Coriolis effect upon reaching western Atlantic Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

23 North Atlantic Ocean Hurricanes: Andrew, August 1992 (1 of 2) Began as thunderstorms over West Africa, August 13 Moved out over Atlantic Ocean as rotating lowpressure air mass Intensified into tropical storm by August 17 Reached western Atlantic on August 21 as upperlevel winds died down, allowing clouds and winds to build, and as high pressure to the north forced Andrew over warmer water to the west August 22: hurricane strength August 23: northern Bahamas, wind speeds of 240 km/hr Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

24 North Atlantic Ocean Hurricanes: Andrew, August 1992 (2 of 2) August 24: crossed southern Florida with 25-mile wide path over homes of 350,000 people, with winds of 250 km/hr, gusts up to 282 km/hr, vortices up to 320 km/hr Killed 33 people, destroyed 80,000 buildings Moved across Gulf of Mexico regaining energy Hit Louisiana with 190 km/hr winds on August 26 Killed additional 15 people Spent remaining energy in heavy rains over Mississippi $35 billion in damages, most destructive in U.S. history Much of damage was result of poor construction Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

25 Figure North Atlantic Ocean Hurricanes Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

26 Global Tropical Cyclone Paths Main influences on hurricane paths: Trade winds blow cyclones west Coriolis effect adds curve to right Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

27 Figure Tracks of all Tropical Cyclones, Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

28 North Atlantic Ocean Hurricanes: Hurricane Paths Influences on hurricane paths: Size, position of Bermuda High: North Atlantic high pressure zone Small, to the north: hurricanes miss coastlines Strong, extensive: guides hurricanes along east coast of U.S. South: guides hurricanes to Gulf of Mexico Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

29 Figure North Atlantic Ocean Hurricanes Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

30 Hurricane Path Influences Bermuda High part of North Atlantic Oscillation (NAO): decade shifting of atmospheric pressures over ocean 1950s: east coast of North America hit by Category 3+ hurricanes 1960s, 1970s: Gulf coast hit by hurricanes Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

31 Figure Hurricane Path Influences Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

32 North Atlantic Ocean Hurricanes: Caribbean Sea- and Gulf of Mexico- Type Hurricanes Form at Intertropical Convergence Zone (ITCZ), where trade winds meet Location of ITCZ moves with migration of the Sun ITCZ located south of equator in Northern Hemisphere s winter and north of equator in Northern Hemisphere s summer Low-pressure area forms where air flows converge thunderstorms hurricane Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

33 North Atlantic Ocean Hurricanes: Hurricane Mitch, October 1998 (1 of 2) October 22: tropical depression 13 at ITCZ in Caribbean 18 hours later: Tropical Storm Mitch 36 hours later: Hurricane Mitch October 26: one of strongest category 5 hurricanes Sustained winds of 290 km/hr, gusts greater than 320 km/hr Winds over 250 km/hr for 15 consecutive hours Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

34 North Atlantic Ocean Hurricanes: Hurricane Mitch, October 1998 (2 of 2) Heading toward Cuba then veered to Central America October 27: stalled off coast of Honduras, winds slowed down to tropical storm strength, but absorbed enormous amounts of water from warm ocean October 30: landfall in Central America, tremendous amounts of rain in Honduras and Nicaragua Three-day rainfall totals up to 2 m About 6,500 people killed in Honduras, about 3,800 people killed in Nicaragua, many by mudflows of pyroclastic material Second deadliest hurricane in history of Americas Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

35 Figure North Atlantic Ocean Hurricanes Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

36 Figure North Atlantic Ocean Hurricanes Hurricane Forecasts Increased number of storms in North Atlantic region can be forecast based on: Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

37 Figure North Atlantic Ocean Hurricanes Hurricane Forecasts Annual probability of a named storm forming Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

38 Figure North Atlantic Ocean Hurricanes Hurricane Forecasts Percent probability of a hurricane hitting the coast. Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

39 TABLE 11.4 Hurricane Landfalls on U.S. Coastline, State Hurricane Hits Florida 114 Texas 64 Louisiana 58 North Carolina 53 South Carolina 30 Alabama 27 Georgia 23 Mississippi 19 New York 13 Massachusetts 11 Connecticut 11 Virginia 10 Data Source: NOAA. Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

40 TABLE 11.5 Hurricane Name Lists for the North Atlantic Basin Seasons, (1 of 2) Ana Alex Arlene Alberto Andrea Arthur Bill Bonnie Bret Beryl Barry Bertha Claudette Colin Cindy Chris Chantal Cristobal Danny Danielle Don Debby Dorian Dolly Erika Earl Emily Ernesto Erin Edouard Fred Fiona Franklin Florence Fernand Fay Grace Gaston Gert Gordon Gabrielle Gonzalo Henri Hermine Harvey Helene Humberto Hanna Ida Ian Irma Isaac Imelda Isaias Joaquin Julia Jose Joyce Jerry Josephine Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

41 TABLE 11.5 Hurricane Name Lists for the North Atlantic Basin Seasons, (2 of 2) Kate Karl Katia Kirk Karen Kyle Larry Lisa Lee Leslie Lorenzo Laura Mindy Matthew Maria Michael Melissa Marco Nicholas Nicole Nate Nadine Nestor Nana Odette Otto Ophelia Oscar Olga Omar Peter Paula Philippe Patty Pablo Paulette Rose Richard Rina Rafael Rebekah Rene Sam Shary Sean Sara Sebastien Sally Teresa Tobias Tammy Tony Tanya Teddy Victor Virginie Vince Valerie Van Vicky Wanda Walter Whitney William Wendy Wilfred Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

42 Decade of the Naughts 2000 to : Florida hit by four hurricanes, Japan hit by 10 typhoons, first documented hurricane in South Atlantic hit Brazil 2005: Hurricane records broken in North Atlantic basin Increase due to human activity or natural variation? Total energy release by hurricanes is higher, probably due to increasing sea-surface temperatures and increased water vapor in lower atmosphere, possibly due to global warming Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

43 Table 11.6 Records Made During the 2005 Atlantic Hurricane Season Most Numerous 28 named storms (old record: 21 in 1933) 15 hurricanes (old record: 12 in 1969) 4 major hurricanes hit the United States (old record:3 in tropical storms before August 1 (old record: 5 in 1997) Costliest U.S. hurricane: Katrina Mexican hurricane: Wilma Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

44 North Atlantic Ocean Hurricanes: Hurricane Damages Hurricane deaths are down in recent decades Hurricane damages are up Larger, more expensive homes on coastlines Destruction and deaths caused by: Winds Storm surges Heavy rains and inland flooding Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

45 TABLE 11.7 The 13 Deadliest Hurricanes in the United States, (1 of 2) When Where Number of Death 8 September 1900 Galveston, Texas 8,000 Mid-September 1928 South Florida Lake Okeechobee 2, August 2005 Hurricane Katrina Louisiana/Mississippi 1,836 Mid-September 1919 Florida Keys/Corpus Christi, Texas September 1915 New Orleans, Louisiana June 1957 Hurricane Audrey Morgan City, Louisiana 416 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

46 TABLE 11.7 The 13 Deadliest Hurricanes in the United States, (2 of 2) When Where Number of Death 2 September 1935 Florida Keys September 1944 East Coast Virginia to Massachusetts 390 Mid-September 1926 Miami, Florida/Alabama September 1909 Grand Isle, Louisiana August 1915 Galveston, Texas September 1938 New England, especially Rhode Island August 1969 Hurricane Camille-Mississippi 256 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

47 TABLE 11.9 The 22 Costliest Hurricanes Striking the United States, (in 2010 US$) (1 of 2) When Where Damage in Billions Hurricane Category 2005 LA/MS Katrina NJ/NY Sandy FL Andrew TX Ike FL Wilma FL/AL Ivan FL Charley NC/NJ/NY Irene SC Hugo FL/NE US Agnes TX Rita FL/LA Betsy TX Allison 11 TS Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

48 TABLE 11.9 The 22 Costliest Hurricanes Striking the United States, (in 2010 US$) (2 of 2) When Where Damage in Billions Hurricane Category 2004 FL Frances E US Floyd MS Camille FL Jeanne FL/AL Opal NE US Diane AL/MS Frederic New England NC Fran 6 3 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

49 North Atlantic Ocean Hurricanes: Storm Surge Hazards Rise in sea level under storm due to: Winds push water ashore to pile up above normal levels, especially on right-hand side of storm highest wind velocities In Northern Hemisphere, highest storm surge occurs km to right of path of eye Low atmospheric pressure causes water to mound up under eye of hurricane Also large waves blown by hurricane winds Also sometimes already high astronomical tides Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

50 Figure North Atlantic Ocean Hurricanes Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

51 North Atlantic Ocean Hurricanes: Heavy Rains and Inland Flooding After moving on land, no more water vapor is absorbed into hurricane, so it loses strength Precipitation of massive volume of water in dissipating hurricane can cause massive flooding and deaths Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

52 TABLE U.S. Hurricane Deaths, Inland flooding 59% Wind 12 Storm surge 12 Offshore 11 Tornado 4 Other 2 100% Source : Tropical Cyclones & inland Flooding (2001); NOAA Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

53 Hurricanes and the Gulf of Mexico Coastline Galveston, Texas, September 1900 Deadliest natural disaster in U.S. history Galveston wealthiest Texas city 38,000 residents given warning of hurricane but many did not evacuate Category 4 hurricane at high tide, with 200 km/hr winds Highest point on island flooded to 0.3 m 8,000 people killed, but many survived 10 m waves by crowding in lighthouse City constructed sea wall, brought in sand to elevate land 1915 hurricane killed another 275 people Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

54 Hurricane Katrina (1 of 2) August 24, 2005: Tropical air mass over Bahamas first catalogued as Katrina August 25, 2005: Grew to hurricane two hours before crossing Florida, lost strength but grew again rapidly over Gulf of Mexico double size, wind speeds 280 km/hr August 26, 2005: models forecast 17% chance of direct hit to New Orleans August 27, 2005: Warnings issued, residents began to flee August 28, 2005: Mandatory evacuation ordered for 1.2 million residents, all roads exit New Orleans Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

55 Hurricane Katrina (2 of 2) August 29, 2005: Came ashore east of New Orleans, wind speeds of 195 mph Pushed in enough water to breach levees, overflow canals and flood 80% of low-lying New Orleans 1,800 of 100,000 residents who did not evacuate were killed Deadliest natural disaster since 1928 Okeechobee hurricane Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

56 Figure Hurricane Katrina Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

57 Figure Hurricane Katrina Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

58 Hurricane Katrina: Were the Katrina- Caused Deaths and Destruction a Surprise? Hurricane like Katrina was anticipated for years Special reports in New Orleans Times Picayune in 2002, among others September 2004: Hurricane Ivan narrowly missed hitting New Orleans, after massive evacuation of city (practice run before Katrina, but same mistakes were repeated) Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

59 Hurricane Katrina: New Orleans-Can This Setting Be Protected? (1 of 2) Water and floods have always been part of city life, three centuries of floods from river and hurricanes Billions of dollars spent on levees City built on delta: loose mixture of sand, mud, and water deposited by Mississippi River Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

60 Hurricane Katrina: New Orleans-Can This Setting Be Protected? (2 of 2) Deltas naturally subside city has subsided to 6 m below sea level and continues to subside Levees prevent flooding, therefore also prevent deposition of new layers of sand and mud that would build up land level Creates bowl, with lake and river water levels higher than city land Subsidence will continue no easy solutions Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

61 Figure Hurricane Katrina Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

62 Figure Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

63 The Evacuation Dilemma Satellite photos allow warning before hurricane makes landfall, people can evacuate out of way Almost 50 million people live in Atlantic Ocean or Gulf of Mexico coastline counties, population growth faster than construction of new roads or bridges Aided by assurance of federal disaster assistance Warning of 1999 Hurricane Floyd hitting South Carolina created massive gridlock leaving people exposed on roads Hurricane Floyd hit North Carolina instead Evacuation dilemma: estimated 72 hours to evacuate most cities Hurricane path not well known 72 hours in advance Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

64 Reduction of Hurricane Damages (1 of 2) Building Codes After many manufactured homes destroyed by 1992 Hurricane Andrew, tougher building codes enacted new manufactured homes survived four hurricanes of 2004 Roofs First step in destroying building is often to lift off roof Prevention by: Elimination or strengthening of eaves Strap roofs to walls Ban stapled asphalt roofing sheets on plywood Impact of Wind-borne Debris Windows of shatter-proof glass or protected by shutters or plywood Remove loose objects outside Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

65 Reduction of Hurricane Damages (2 of 2) Land-Use Planning Use low-lying coastal land for parks, farm fields, golf courses, nature preserves, etc., where flooding is not damaging Coastal Development Restrictions Current building boom on shorelines Thousands of new homes built since last hurricane strike FEMA estimates next 60 years: 25% houses within 150 m of shoreline will fall into water during some hurricane, without mitigating actions Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

66 Figure Hurricane Proofing a House: Sit atop pilings Allow water to flow below house Bolted steel beam construction No eaves Solid, heavy roof Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

67 Global Rise in Sea Level Global rise of ~1 ft in 20 th century, probably 3 ft or more in 21 st century Can move beaches inland by 1,000 ft in low-lying areas Continuing buildup of houses along coastline is just asking for trouble Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

68 Figure Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

69 Hurricanes and the Pacific Coastline 15% of Earth s tropical cyclones: offshore southern Mexico, Guatemala, El Salvador Why is Pacific coastline hit by fewer hurricanes? Trade winds blow hurricanes west out to sea Cold California current from Alaska reduces energy available for hurricanes Hurricane Iniki, September 1992 Hawaiian Islands at northern edge of hurricanegenerating warm waters, hit by storms formed to the southeast Iniki: category 4 storm tore across Kauai with 210 km/hr sustained winds and gusts of 260 km/hr Damaged all buildings, cost island economy $2 billion Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

70 Cyclones and Bangladesh Seven of world s nine most deadly weather events in 20 th century were cyclones hitting densely populated Bangladesh low-lying sediments of deltas of Ganges and Brahmaputra Rivers, 1/3 below 6 m elevation In average year, 20% of country submerged in floods 1970 cyclone during full Moon high tides brought surge of 7 m, winds of 235 km/hr 300,000 people killed 1991 cyclone with 6 m surge, 235 km/hr winds killed 140,000 people Population of Bangladesh is expected to double in next 30 years Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display