Tag Archives: floods

Historic Flooding in West Virginia

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Relentless rain unleashed catastrophic flooding across West Virginia late last week. Officials say it was the state’s worst flood disaster in more than a century.

According to the NWS, the Mountain State received about 25% of its average annual rainfall in just a few hours. In Greenbrier County, more than 10 inches of rain fell between Thursday and Friday. This massive amount of precipitation in such a short period of time overwhelmed rivers and streams throughout the area. In Kanawha County, which includes the state capital of Charleston, the Elkview River crested at 33.37 feet – its highest crest in more than 125 years of record keeping.

The raging torrents of floodwater damaged or destroyed thousands of homes and businesses, as well as infrastructure across the state. To date, twenty-three weather-related deaths have been reported and more than 10,000 customers are still without power.

This type of rainfall is considered a one in one thousand year event in West Virginia. That does not mean it can only happen once every thousand years. It is the recurrence interval, a statistical calculation that means an event has a one in one thousand chance (0.1%) of happening in any given year in a given location.

The cause of this devastating flooding was twofold and involved a combination of weather and topography. First, “training” thunderstorms developed along a boundary between cooler air to the northeast and warm, moist air to the southeast. This is a meteorological phenomenon where strong storms flow continuously over the same area for a relatively short period of time – like train cars traveling along a track – dumping excessive amounts of rain.

The second major player in this deadly deluge was the state’s mountainous topography. When substantial rain falls in hilly terrain, it runs downslope very quickly and causes flash flooding in valleys, where most people tend to live. Moving with tremendous force, this type of fast flowing water can pick up and destroy almost anything in its path.

The Governor of West Virginia, Earl Ray Tomblin, has declared a state of emergency in 44 of the state’s 55 counties as a result of the flooding. Additionally, President Obama declared a major disaster in three of the hardest hit counties – Kanawha, Greenbrier, and Nicholas – which allows federal funds to supplement state and local emergency efforts.

Flooding In West Virginia. Credit: ABC11

Flooding in Richwood, Nicholas County, West Virginia. Credit: J. Rose/ABC11

Bonnie Makes Landfall as a Tropical Depression in South Carolina

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Bonnie, the second named pre-season storm of 2016, made landfall on Sunday just east of Charleston, South Carolina on the Isle of Palms.

According to the NWS, Bonnie was categorized as a tropical storm on Saturday with winds as high as 45mph. But by the time it came ashore, its winds had fallen below 39mph – the threshold for a tropical storm – and was downgraded to a tropical depression. Despite this reduced status, the storm still brought heavy rain, flash flooding, and dangerous rip currents to the area.

Rainfall totals, according to the Charleston NWS office, reached as high as ten inches in some spots. Flash flooding in Jasper County even caused sections of Interstate 95 – one of America’s busiest highways – to close.

Remnants of Bonnie are expected to linger over the southeastern US for the next several days, bringing even more rain to the region.

The Atlantic Hurricane Season official begins on June 1st.

Bonnie makes landfall as a tropical depression near Charleston, SC. Credit: NASA

Bonnie makes landfall as a tropical depression near Charleston, SC. Credit: NASA

 

Historic Flooding in Houston

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Relentless rain unleashed catastrophic flooding across southeast Texas on Monday. Local officials say this was the worst flooding event the region has seen in years.

Rainfall totals across the Houston metro area varied, but some places saw nearly 17 inches in less than 24 hours. The NWS office in Houston reported 9.92 inches of rain at Houston Intercontinental Airport (IAH), making it that city’s second wettest day on record. On average, Houston typically gets 3.46 inches of rain for the entire month of April.

The intense rainfall caused bayous to swell out their banks and flood homes, businesses, and major roadways – effectively paralyzing large parts of this country’s 4th largest city. Rainfall rates reached as high as 3 to 4 inches per hour in some spots, which prompted the NWS to issue a flash flood emergency (the highest level of flood alert) for the area. Local officials say 5 people were killed and more than 100,000 people lost power as a result of the flood.

The primary driver behind this extreme rain event was also main reason why the eastern US has been unseasonably warm and dry recently. The omega block that sat over the country for the past few days basically set up a large ridge of high pressure in the east and blocked an upper-level low from moving past the Four Corners region. Essentially stuck in place, the upper-level low funneled in massive amounts of moisture from the Gulf of Mexico. That moisture was then forced to rise and cool when it interacted with the stationary front in the area. The result was an extended period of thunderstorms and intense rainfall.

Southeast Texas is no stranger to flooding. In fact, this was the fourth major flood to hit the area in the past twelve months. The previous three took place in May, June and October of 2015. But, officials in Houston say Monday’s event was the largest flood the area has seen since Tropical Storm Allison in 2001. That storm dumped more than 35 inches of rain on the Houston metro area over the course of five days and caused $5 billion worth of damage.

The Governor of Texas, Greg Abbot, has declared 9 counties to be disaster areas as a result of Monday’s storm.  More rain, unfortunately, is forecast for the region this week.

View of flooding in downtown Houston, TX. Credit: KHOU

View of flooding in downtown Houston, TX.  Credit: KHOU

From Drought to Flood: Weather Whiplash in Texas

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Bouncing between the extremes of drought and flood, the weather whiplash in Texas continued this weekend. For the second time this year, torrential rain caused widespread flooding across the Lone Star State.

The city of Corsicana, south of Dallas, saw more than 18 inches of rain between Friday and Saturday. Flash floods caused extensive damage and even derailed a Union Pacific freight train. In Houston, where they received 8 inches of rain on Saturday and Sunday, bayous swelled out of their banks and flooded roadways. Local officials say Buffalo Bayou near the downtown area rose 20 feet in just 12 hours.

The cause of this prolonged rain event involved the interaction of a few key atmospheric players. First, an area of high pressure over the east coast – with a clockwise circulation – pushed tropical moisture across the Gulf of Mexico and into Texas. Then, there was a strong upper level low – with a counter clockwise circulation – over the southwest and a cold front moving southeast. These added lift to the atmosphere. When the warm saturated air was forced to rise, it cooled. Since cool air holds less moisture than warm air, the moisture was wrung out of the atmosphere in the form of intense rain. Then, on the heels of all that, remnants of Hurricane Patricia from the Pacific Ocean traveled across Mexico and into Texas. It brought even more tropical moisture into the mix.

Ironically, much of Texas was in a drought just last week. It was considered a “flash drought” as it developed very quickly this summer after intense rains and catastrophic flooding in May brought the previous drought to an abrupt end. From drought to flood to drought and back to flood, Texas certainly has had a wild ride with weather this year.

Credit: NBC Train derailed by flood waters near Dallas, TX

Freight train derailed by flood waters near Corsicana, TX. Credit: NBC News

Historic Flooding in South Carolina

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Relentless rain unleashed catastrophic flooding across South Carolina this past weekend. Officials say it was one of the worst disasters in the state’s history.

According to the NWS, an estimated 5.8 trillion gallons of water fell in the Palmetto state in just four days with some communities receiving more than 20 inches of rain. This storm total exceeds that of any tropical cyclone on record that has impacted South Carolina.

Receiving this massive amount of precipitation in such a short period of time overwhelmed rivers and streams, and even caused a number of dams to breach. The floodwaters inundated homes, businesses, and shut down major roadways, including parts of Interstate-95. Local officials say the storm also caused water mains to break, leaving more than 40,000 people without drinkable water. To date, seventeen weather-related deaths have been reported across the state.

This type of rainfall is considered a one in thousand year event in South Carolina. That does not mean it can only happen once every thousand years. It refers to the recurrence interval – a statistical calculation that means an event has a one in one thousand chance (0.1%) of happening in any given year in a given location.

The cause of this widespread and destructive flooding was the unique convergence of three different weather systems that essentially set up an atmospheric river – a fire hose of moisture – aimed directly at South Carolina. The first was Hurricane Joaquin, which sat over the Bahamas for days and pumped huge amounts of moisture into the atmosphere. The second was an upper level low-pressure area over the southeastern US and Gulf of Mexico. It helped pull some of Joaquin’s moisture westward toward the US coastline. And lastly, there was a stalled frontal boundary along the coast. When the warm saturated air encountered the cooler air along the front, it was forced to rise and cool. Since cool air holds less moisture than warm air, the moisture was wrung out of the atmosphere in the form of intense rain over the same area for days.

Although the rain has now cleared, South Carolina is not out of the woods just yet. As swollen rivers make their way to the Atlantic, more flooding is expected in the state’s coastal low country.

Credit: NWS Columbia/NOAA

Credit: NOAA/NWS Columbia

When it Rains, it Pours

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Torrential rain events and the flooding they cause are nothing new.  Global warming, however, is helping to make them more likely.

According to the most recent National Climate Assessment, heavy rain events – defined as the heaviest 1% of all rain events – have become heavier and more frequent across most of the US. The greatest increases have been observed in the northeast, mid-west, and southeast.

Climate scientists attribute this increase in heavy precipitation to our warming atmosphere. Simply put, warm air holds more moisture than cold air. And, the more moisture that builds up in the air, the more rain can fall.

The relentless rain and deadly floods in Texas last month made national headlines, but there are many other examples of similar events in the recent past. In September 2013, Colorado experienced catastrophic flooding caused by overwhelming amounts of rain in a short period of time. Locally, here in the NYC area, the town of Islip on Long Island saw more than 13 inches of rainfall in a single day last August. That equates to 29% of their average annual rainfall. The damage caused by that single event was estimated at $35 million.

As our global temperature continues to rise, experts say we should expect to see more extreme rain events, even in areas where overall precipitation is projected to decrease. In other words, when it rains, it will likely pour.

The map shows percent increases in the amount of precipitation falling in very heavy events (defined as the heaviest 1% of all daily events) from 1958 to 2012 for each region of the continental United States. These trends are larger than natural variations for the Northeast, Midwest, Puerto Rico, Southeast, Great Plains, and Alaska. The trends are not larger than natural variations for the Southwest, Hawai‘i, and the Northwest. The changes shown in this figure are calculated from the beginning and end points of the trends for 1958 to 2012.

The map shows percent increases in the amount of precipitation falling in very heavy events  from 1958 to 2012 for each region of the continental United States. These trends are larger than natural variations for the Northeast, Midwest, Puerto Rico, Southeast, Great Plains, and Alaska. The trends are not larger than natural variations for the Southwest, Hawai‘i, and the Northwest. Credit: 2014 US National Climate Assessment

Catastrophic Flooding in Texas

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Relentless rain unleashed catastrophic floods across southeast Texas this past weekend. Coming out of a prolonged drought, officials say this was the worst flooding the region has seen in years.

In Houston, more than 10 inches of rain fell Monday night into Tuesday morning. With the ground already saturated from plentiful spring rains, rivers and bayous swelled out of their banks.  The floodwaters inundated homes, businesses, and major roadways, paralyzing large parts of this country’s 4th largest city.  Rainfall rates reached as high as 4 inches per hour, which prompted the NWS to issue a flash flood emergency – the highest level of flood alert – for the area.  Local officials say 3 people were killed and more than 80,000 people lost power as a result of the flood.

On Sunday, torrential rain in Hays County, TX caused the Blanco River to rise more than 30 feet in 3 hours. Before the river gauge was washed away, it reported a crest of 40.21 feet, which is about 7 feet above the previous record set in 1929. Officials there say the raging water destroyed more than 350 homes and that 13 people are still missing.

Just north of Texas, the Oklahoma City area also experienced severe weather and flooding this holiday weekend. Across both states, floodwaters caused a number of fatalities. The combined death toll currently stands at 14, but is expected to rise.

The intensity of these rain events had two main drivers. First, a mass of warm and deeply saturated air moved north from the Gulf of Mexico.  It then ran into a deep dip in the jet stream, which has been locked in place over the western states recently. This collision triggered intense thunderstorms that wrung tremendous amounts of moisture out of the air.  The result was a series of deadly and destructive deluges across the region.

The Governor of Texas, Greg Abbot, has declared 37 counties from the Red River to the Rio Grande to be disaster areas as a result of recent weather events.  More rain, unfortunately, is forecast for the region this week.

Flooded roadway in Houston. Credit: KTRK

Flooded roadway in Houston. Credit: KTRK

An App to Visualize the Impacts of Sea Level Rise in South Florida

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Sea level rise is one of the most pressing aspects of climate change for coastal communities around the globe.  Here in the US, South Florida is especially vulnerable. Raising awareness of this issue, a team of professors and students at Florida International University (FIU) have created a web app called the Sea Level Rise Toolbox.

Utilizing elevation data from Google and sea level rise calculations made by FIU scientists, the app visualizes the potential impacts of a 0 to 6 foot rise in sea level for neighborhoods across Miami-Dade County. The goal of the app, according to Susan Jacobson, an assistant professor at FIU and the web app project manager, “is to inform residents of South Florida about the potential impact of sea level rise where they live.”

This eye-opening app is free and easy to use. Check it out at:http://eyesontherise.org/app

Sea Level Rise Toolbox. Credit: FIU.

Sea Level Rise Toolbox. Credit: FIU.

Super-Storm Sandy: Two Years Later

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Two years ago today, Super-storm Sandy slammed the New York City tri-state area.  Despite being downgraded from hurricane to post-tropical status just prior to landfall, Sandy was the second costliest natural disaster in U.S. history, following Hurricane Katrina in 2005. The question is, can it happen again?

Coming ashore with tropical storm-force winds at high tide during a full moon, Sandy was an unprecedented storm. It formed late in the season, grew as it moved north, and instead of turning out to sea like most tropical systems, it made that now famous left hook toward the coast. Statistically, Sandy’s unusual trajectory was a 1-in-700-year event, according to a recent study by researchers at NASA and Columbia University. That said, as sea levels continue to rise, future storm surges will have a higher starting point and be able to reach further inland. So, a lesser storm could produce similar, if not worse, flooding in the future. A different study in the journal, Nature Climate Change, predicts that a current “500 year” storm surge event in NYC could happen every 50 to 240 years by the end of the century.

Sandy caused a record 13.88-foot storm surge at the Battery in lower Manhattan.  It flooded many low-lying areas, including parts of the NYC subway system.  The massive storm, according to the CDC, directly claimed the lives of 117 people in the U.S – mostly by drowning. Damaging or destroying more than 650,000 homes, Sandy displaced thousands of people and caused approximately $70 billion in property damage in addition to knocking out power to 8.5 million people for multiple days.

In reaction, many government agencies – at all levels – have been re-evaluating their strategies for dealing with future storm surge flood disasters.  The National Hurricane Center changed its policy for issuing warnings on post-tropical storms and has developed an experimental Potential Storm Surge Flooding Map that depicts the risk associated with a storm surge during a tropical cyclone. In NYC, the Office of Emergency Management   re-drew its hurricane evacuation zones to reflect the threat of higher sea levels.

As these types of important improvements are being made, the arduous process of rebuilding homes and installing physical defenses against future storms is still ongoing, especially in  the region’s hardest hit areas.

NYC Sea Level Rising Faster than Global Average

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Sea level is on the rise around the globe. Some areas, such as New York City, however, are seeing the water rise faster than others.

According to the latest IPCC report, the average global sea level has risen about eight inches since 1880.  Locally, in New York Harbor, the water has risen by more than a foot in the past century. The graph below shows the upward sea level trend at the Battery, Manhattan’s southern tip.

In general, sea level rise has two main drivers. They are thermal expansion – a process in which water expands as it warms – and the melting of land based ice, such as glaciers and ice sheets. Both are the result of rising global temperatures. On the local level in NYC, there is also the issue of glacio-isostatic adjustment. This process is not caused by current glacial melt, but rather by the modification of the Earth’s surface as it slowly responds to the removal of the massive weight of ancient glaciers. Overall, it causes some land surfaces to rise and others to sink.  In NYC, the land is slowly sinking.  This combination of factors is expected to intensify future storm surge events in the city.

Sea level in NY Harbor is rising faster than the global average. Credit: NOAA

Sea level is rising in NY Harbor.   Credit: NOAA