Storm Surge — the Big Killer

When a hurricane strikes land, the storm surge can be more deadly than the storm’s violent wind. Tropical cyclones – called hurricanes in the Atlantic, typhoons in the Pacific, and cyclones in Australia and India – have killed over 1 million people in the past hundred years. The majority of those deaths are attributed to the surge component of the storm.

Typhoon Haiyan hit the Philippine Islands city of Tacloban on November 11, 2013, with a wind speed of 195 mph (315 km/h), the strongest landfall speed ever recorded. Over 5,000 died and the city was leveled. The savage wind took its toll, but it was the 20 ft. (6.6m) wall of ocean water surging more than a mile (1.6 km) inland that took most of the lives.

When Superstorm Sandy came ashore in New Jersey and New York in late October, 2012, the wind speed was only 115 mph (185 km/h), but the storm was so massive it pushed a 14 ft. (4.4m) storm surge far inland, killing more than 100 and wiping out or badly damaging thousands of homes. Reconstruction costs have reached $70 billion.

In August, 2005, Hurricane Katrina, a Category 3 with a wind speed of120 mph (192 km/h) struck New Orleans and Gulf Coast cities in Louisiana, Mississippi, and Alabama. Although the wind did some damage, the storm surge with waves as high as 28 ft. (7.5m) wiped out shoreline communities, and breached New Orleans’ levees, flooding the city, and causing most of the 1,800 deaths.

Some of the most destructive storm surges have occurred in Bangladesh and India. The northern end of the Bay of Bengal is funnel shaped, and storm surges become tidal bores that sweep many miles inland. The Bhola cyclone in 1970 produced a storm surge of 35 ft. (11m), taking 500,000 lives in Bangladesh. The largest storm surges ever recorded took place in India in 1839 when a 40 ft. (12.2m) surge killed 300,000; and in Bathurst Bay, Queensland, Australia, where a 42 ft (12.8m) surge killed 400 in 1899. It was reported at the time that dolphins and fish were found atop the cliffs surrounding the bay.

A storm surge is created by the storm’s high wind piling the ocean’s surface higher than ordinary sea level. Low pressure at the center of the weather system has a lifting effect and aids in the buildup of the sea and the energy of the surge.

People living near the shoreline in tropical storm-prone areas should be prepared not only to protect property against the high wind, but also be aware of storm surge danger, and prepared to evacuate before the storm makes landfall.       

Pacific Typhoon Season

While residents of the East and Gulf Coasts of North America prepare for hurricane season, people in Japan, Taiwan, the Philippines, and the coast of China get ready for typhoon season. Hurricane and typhoon are different names for the same type of tropical storm — what meteorologists refer to as tropical cyclones. Both originate in warm tropical waters as tropical waves, evolving to tropical depressions. Both typhoons and hurricanes are reported on the same Safir-Simpson Hurricane Wind Speed Scale, elevating from tropical depression to tropical storm to Category One Typhoon or Hurricane when wind speed reaches 74 mph (121 km/h).

The 2013 typhoon forecast issued by the Typhoon Storm Risk Consortium of University College in London predicted between 23 and 27 tropical storms in the Western Pacific during 2013, an average year. Historically, there have been 25.7 tropical storms per season. Seven have already occurred this year, including Tropical Storm Rumbia that struck the Philippines and China in late June and early July, causing widespread flooding and mountain landslides that killed 55 and made thousands homeless.

On July 13, 2013, Typhoon Soulik, the first Pacific storm to strengthen to Category 3 typhoon status, battered Taiwan with 115 mph (190 km/h) winds and torrential rain. One mountain village reported 24-hour rainfall of 35 inches (900mm). Taiwan authorities had evacuated a number of mountain villages to prevent landslide deaths. Even so, 2 people were killed and over 100 injured on Taiwan by the storm.

Halsey’s Typhoon. One of the most notable typhoons in history took place during World War II. On December 17, 1944, Admiral William “Bull” Halsey inadvertently sailed the U.S. Third Fleet into the heart of Typhoon Cobra, with winds gusting to 145 mph (230 km/h), extremely high seas, and torrential rain. The fleet, consisting of 13 aircraft carriers, 8 battleships, 15 cruisers, and 50 destroyers, had been refueling after a series of air raids on Japanese installations on Luzon, and were caught unprepared. 3 destroyers capsized in the storm, with a loss of over 800 lives. Nine other ships were badly damaged, more than 100 aircraft were wrecked or washed overboard, and almost every ship in the fleet sustained some damage. 93 sailors from the capsized ships were rescued by other ships in the fleet. A court of inquiry found that Admiral Halsey had committed an error of judgment in sailing the fleet into the storm, but no sanctions were recommended. Many believe the novel The Caine Mutiny was based on the experience of Herman Wouk, the author, who was serving aboard one of the fleet’s ships during Typhoon Cobra.

 

Natural Disasters — Luck of the Draw

Natural disasters inflict suffering on millions of people every year, but most of us pay little attention as we go about our daily routines. We might be somewhat aware of others’ misfortunes by reading about them or watching news clips, but it’s a different story if you happen to be where the disaster happens.

In the summer of 2012, for example, there were major floods in the Black Sea area of Russia, in Niger, the Philippines, and Myanmar (Burma) that took hundreds of lives and made many thousands homeless.  A series of earthquakes struck Iran in August and southwestern China in September, killing hundreds and destroying thousands of homes. Typhoon Bolaven hit the Korean Peninsula at the end of August with high winds and driving rain, causing hundreds of fatalities and mass home evacuations. On the same day that Typhoon Bolaven pummeled Korea, Hurricane Isaac struck the U.S. Gulf Coast with 90 mph (150 kph) winds, heavy rain, and a storm surge of more than11 ft. (3.4m). There were 9 deaths, and hundreds of homeless in flooded neighborhoods. Although Isaac delivered rain to many parts of a parched Mississippi Valley, most of the southwest and Midwest continued to suffer one their worst droughts on record.

Natural disasters cause death and damage all over the planet, all year, every year. It all depends on where you are the moment. Most of us are lucky. Some of us aren’t.

 

 

 

Are Hurricanes Getting Stronger?

Recent modeling studies indicate that while the average number of Atlantic hurricanes per year will probably not increase by the end of the century, the intensity and amount of rainfall produced per storm most likely will rise. Global warming is thought be one contributor to these changes. As climate warms, ocean temperatures warm, causing increased evaporation and cloud formation.

 

A 2008 study by NOAA’s Geophysical Fluid Dynamics Laboratory, last revised in August, 2011, indicates that global warming will very likely bring about these outcomes: (1) a 2% to 11% increase in hurricane intensity; (2) a doubling in the frequency of very intense – categories 4 and 5 – hurricanes; (3) higher rainfall rates than present day hurricanes, with a projected increase of 20% within 100 km (60 mi) of the storm center; (4)  no increase in the number of storms annually; (5) changes will be gradual, and probably not detectable for several decades.

 

Hurricane Irene and Tropical Storm Lee, the two 2011 tropical storms that made landfall in mainland United States up to September 13, were not as intense as originally forecast, but were heavy rainmakers and caused considerable property damage and a number of deaths.

Irene, which started as a tropical wave off the west coast of Africa, grew to a category 3 hurricane in the Caribbean, but had dropped to a category 1 when it made landfall on August 27 in North Carolina with a wind speed of 85 mph (140kph). After going back out to sea, Irene made its second landfall in New Jersey, and had been downgraded to a tropical storm when it made its third landfall in Brooklyn, NY.  Heavy rain associated with the storm caused widespread flooding in New Jersey and Vermont. 55 people were confirmed dead as a result of the storm. Property loss was estimated at $10 billion.

Lee started as tropical depression in the Gulf of Mexico and was upgraded to a tropical storm on September 2. It came ashore in Louisiana on September 3 with sustained winds of 45 mph (80kph), but was a slow moving and very wet storm, depositing 11 inches (28mm) of rain on New Orleans and Mobile in the first 24 hours. It tracked north, delivering 13 inches (33mm) to parts of Pennsylvania, causing the Susquehanna River to  crest at just over 42 feet (13m), the highest ever recorded. Wilkes-Barre, PA and Binghamton, NY sustained substantial flood losses.

Earlier, Tropical Storm Arlene, the first of the season, produced heavy rain in several Mexican states, triggering mudslides that killed 22.

While this was happening in North America, Typhoon Talas struck Japan. It, too, was a low intensity, slow moving storm that produced very heavy rain. Wind speed didn’t exceed 65 mph (100kph), but parts of Japan received 79 inches (2,000mm) of rain between September 3 and September 8. 59 people died and 50 were missing as a result of flooding and mountain mudslides.

Storm surge was not a factor in either Irene or Lee, but In stronger hurricanes, more people die from the storm surge than from the high winds. A storm surge is created by the wind’s piling the ocean’s surface higher than ordinary sea level. Low pressure at the center of the weather system has a secondary effect in the buildup of the sea and the energy of the surge. A category 4 hurricane tends to build an 18-ft (5.5m) surge, but during Katrina in 2008, 20-to-30 ft (6.1 to 9.1m) waves were reported along parts of the U.S. Gulf Coast.

Hurricanes and all tropical cyclones start as a cluster of thunderstorms moving over warm ocean water registering 80F (26C) and greater. Thunderstorms form in areas of wind convergence. Off the west coast of Africa, the northern and southern equatorial winds collide and force warm moist air to rise and condense to form storm cluster formations called tropical disturbances. As a tropical disturbance grows and organizes, more water vapor condenses in rising air, causing the surface air pressure to drop.

As more warm moist air rises and condenses, the storm system increases in size, the surface pressure drops further, and the storm becomes a tropical depression. The earth’s rotation can impart a spin to the storm clouds at this point, causing even more warm moist air inside the spiral to rise and condense, enlarging the storm area, and increasing the storm’s wind speed. The formation becomes a tropical storm when wind speed reaches 39 mph to 73 mph (62-117 KPH). The storm becomes a category 1 hurricane when the wind strengthens to 74 mph to 95 mph. Here are the hurricane categories:

Category         Wind MPH       KPH                  Surge Ft           Meters

1                      74 to 95           118-152           5                      1.5

2                      96 to 110         153-176           8                      2.4

3                      111 to 130       177-208           12                    3.7

4                      131-155           209-248           18                    5.5

5                      155+                248+                18+                   5.5+

Tropical Cyclones are called hurricanes in the Atlantic, typhoons in the Western Pacific, and cyclones in India and Australia. Even though the North American Eastern and Gulf Coasts have experienced many highly destructive hurricanes, tropical cyclones with even more devastating consequences have occurred in the Bay of Bengal, where much of Bangladesh and parts of India are low-lying wetlands and wide open to storm surge damage. The northern end of the Bay of Bengal is funnel shaped, and storm surges become tidal bores that sweep many miles inland. The Bhola cyclone in 1970 had sustained winds of 140 MPH (224 KPH) and a storm surge of 35 feet (10.7m). 500,000 died. In April, 1991, a similar storm in the same area killed 150,000. The biggest storm surges recorded occurred in India in 1839 when a 40-ft (12.2m) surge killed 300,000; and in Bathurst Bay in Queensland, Australia in 1899 when a 42-ft (12.8m) surge killed 400. It was reported at the time that dolphins and fish were found atop cliffs surrounding Bathurst Bay.

One of the most notorious typhoons in American military history hit Okinawa in October, 1945, two months after the end of World War II. A large segment of the U.S. naval task force that had been assembled for the invasion of Japan was still anchored in Buckner Bay on the east coast of Okinawa. Typhoon Louise, which had developed south of Guam, took a sudden unexpected turn and headed straight for Okinawa, giving the fleet no advance warning and no time to put to sea. The typhoon struck with sustained winds of 100 MPH (160 KPH), gusting to 120 MPH (192 KPH). Waves in the bay rose to 35 ft (10.7m). The fleet task force was devastated. 12 ships were lost, 222 went aground, and more than 30 were badly damaged. 83 sailors were dead or missing, and another 100 badly injured. It was fortunate for the Allies that the surrender had already been signed. The crippled task force would have been hard pressed to carry out its mission had it been called upon to do so. Damage on the island, where 200,000 troops had been massed for the invasion of Japan, was equally severe. Roads were washed out. Supply depots were blown down, scattered, and drenched by seawater blowing across the island. Aircraft and landing strips were badly damaged. Most islanders and many soldiers took refuge in Okinawa’s many caves.

Typhoons changed the course of history in 13th century Asia. The Mongolian leader Kublai Khan ruled all of mainland Asia, including Mongolia, China, and what is now Korea. The only Asian nation Kublai Kahn hadn’t conquered was Japan. In 1274, he assembled a fleet of hundreds of ships and thousands of soldiers and set out to invade the Japanese islands. Off the coast of Japan a typhoon struck the invading force. Most of the wooden ships were demolished and the rest retreated to the mainland. The Japanese called the typhoon Kamikaze, or divine wind. In 1281, Kublai Khan tried again, this time with thousands of ships and a hundred thousand soldiers. Once again a typhoon intervened, wrecking the invading fleet. Kublai Khan made no further attempt to conquer Japan. Twice, the Kamikaze divine wind had saved the Japanese empire. The Kamikaze pilots of World War II were named after the wind that saved Japan.

This is an updated revision of one of this website’s earlier articles.