WunderBlog Archive » Category 6™
Category 6 has moved! See the latest from Dr. Jeff Masters and Bob Henson here.Thousands Urged to Evacuate Iowa Floods; Megi’s Threat to Taiwan Escalates
Water from the Cedar River will overspread a large swath of Cedar Rapids, Iowa’s second-largest city, on Tuesday. Fed by massive rains over northeast Iowa during the past week, the flood crest of 23 feet projected on Monday afternoon for Tuesday afternoon would be the second-worst in city history--topped only by the 31 feet during the catastrophic flood of June 2008, and 3 feet higher than all other crests. Officials have strongly encouraged residents of about 5000 homes in central Cedar Rapids to evacuate ahead of the flood crest (see map at bottom of this post).
Figure 1. Iowa National Guard members walk past a local business covered in sandbags, Monday, Sept. 26, 2016, in Cedar Rapids, Iowa. Residents are waiting anxiously as a quickly rising Cedar River threatens to inundate their city with devastating floodwaters for the second time in eight years. Image credit: AP Photo/Charlie Neibergall.
The floods of 2008 eclipsed anything on record across eastern Iowa, particularly in Cedar Rapids and Iowa City. The estimated cost of that flood reached $10 billion, with more than 5000 homes and nearly 1000 business damaged. This time, the heaviest rains (more than 10” in 24 hours last Wednesday--see Figure 3 below) have been focused across the Cedar River basin north of Cedar Rapids, which is helping to keep the most serious flooding within that corridor, including Cedar Falls and Waterloo. Another plus: the flood crest heading toward Cedar Rapids in 2008 was boosted by an intense storm just one day before it peaked downtown. “That’s why the intensity of the flooding caught people by surprise. Nothing like that is in the cards [this time]” Witold Krajewski, director of the Iowa Flood Center, told me. In fact, the flood crest should arrive on Tuesday beneath sunny skies. “Because this event is well predicted, the city is well prepared,” said Krajewski.
Figure 2. An aerial image shows flood-affected areas on June 13, 2008 in Cedar Rapids, Iowa. Image credit: David Greedy/Getty Images.
Cedar Rapids since 2008: Progress and problems
In the wake of the 2008 floods, Cedar Rapids and surrounding Linn County took big strides toward preparing for future disaster. The city and county are among three pilot communities nationwide in the Resilient America project, organized by the National Academies to help communities build resilience and reduce the physical and economic toll of disasters. In Cedar Rapids, roughly 1400 flood-damaged homes were acquired by the city and removed over the last eight years. That action has already cut back on the destruction that this week’s flood might wreak. The city has also adopted a $625 million flood protection plan, including a series of new levees and floodwalls. However, these structures have yet to be built: federal funding has been authorized, but has not yet been provided. As a result, some of the areas restored in the wake of the 2008 flood are imperiled once again.
Citizen-volunteers have been pitching in this week, helping to put more than 250,000 sandbags in place to help stem the flood crest. A Facebook page devoted to the unfolding flood is helping connect people to the most pressing needs. About 100 volunteers spent Sunday removing almost 1000 seats from the historic Paramount Theatre in downtown Cedar Rapids. After being heavily damaged in 2008, the theatre was restored with federal, state, and local funds totalling $35 million.
Figure 3. A swath of 8” - 10” of rain fell on Wednesday, September 21, 2016, atop the northwest-to-southeast Cedar River basin. Enhanced by other rains over the past week, this flood crest has moved southeast past Waterloo and Cedar Falls and is now approaching Cedar Rapids (southeast of map domain). Image credit: Iowa Flood Information System/Iowa Flood Center.
A very out-of-season flood for eastern Iowa
September is not when Iowans are usually keeping an eye on flood risk. In fact, this is the first time on record that a flood of any magnitude (at least 12 feet) has been measured on the Cedar River at Cedar Rapids. Heavy rains are far more common during spring and summer across eastern Iowa. Climate change has been shown to exacerbate the intensity of the heaviest rainfall events in the United States and many other parts of the world, as warmer temperatures allow more moisture to evaporate into the atmosphere. Research led by Eugene Takle (Iowa State University) found that eastern Iowa has already seen a measurable rise in the number of days with rainfall that is typically too heavy for soils to absorb (1.25” in a 24-hour period). “We can logically conclude that enhanced streamflow and the potential for flooding are also rising,” Takle wrote. His research has also found a shift away from spring floods (as warmer spring temperatures allow for earlier snowmelt) and toward late-summer events. Storms in late summer tend to be oriented along northwest-to-southeast trajectories, which aligns them with river basins in eastern Iowa. “This seems to be the new norm for seasonal flood occurrence in the state,” noted Takle.
Figure 4. Enhanced infrared satellite image of Typhoon Megi as of 2100Z (5:00 pm EDT) Monday, September 26, 2016. Image credit: RAMMB/CIRA/CSU.
Megi intensifying as it nears Taiwan
Typhoon Megi vaulted to Category 3 strength on Monday afternoon, heightening the risk to Taiwan. As of 18Z (2 pm EDT), Megi’s top sustained winds (averaged over 1 minute) were estimated at 115 mph by the Joint Typhoon Warning Center. Satellite imagery suggests that Megi has almost completed an eyewall replacement cycle, with its small eye from last weekend now superseded by a much larger but still-ragged eye, about 35 miles in diameter. The timing of this replacement cycle is bad news for Taiwan, as Megi has had just enough time to begin consolidating very intense, widespread thunderstorms around this newly formed eye. The 21Z Monday (5 pm EDT) forecast from JTWC brings Taiwan onshore with peak winds of at least 110 mph.
Figure 5. As of 18Z (2:00 pm EDT) Monday, September 26, the center of Typhoon Megi is projected to pass through central Taiwan between 06Z and 18Z Tuesday (2:00 pm Tuesday to 2:00 am Wednesday local time). Image credit: Central Weather Bureau, Taiwan.
Although Taiwan is experienced with typhoons—it gets three to four in a typical year--Megi will be striking the island head on, with its center passing through the heart of Taiwan. This will put the northern half of the island, which includes the capital of Taipei, in the more dangerous right-hand part of Megi. All signs point to Megi being an expensive and potentially deadly disaster for Taiwan, with wind damage, massive rainfall, and landslides a good bet across mountainous eastern Taiwan and major disruption in the capital city of Taipei, at the island’s north end. As of 2:20 am local time (2:20 pm EDT), 24-hour rains had already topped 200 mm (7.87”) at Taoyuan City, just west of Taiwan. Exacerbating the flood risk will be the saturated ground produced by heavy rain from Super Typhoon Meranti and Typhoon Malakas over the last two weeks.
On its predicted course, Megi would make a second landfall as a tropical storm along the coast of southeast China, not far south of where Meranti claimed at least 29 lives and caused at least $2.6 billion in damage.
Taiwan's typhoon history
According to EM-DAT, the international disaster database, the most damaging typhoon in Taiwan’s history was Typhoon Herb of 1996, which hit the island as a Category 4 super typhoon with 150 mph winds. The eye passed directly over the capital of Taipei, and the storm unleashed rains as high as 78.23”. Damage was estimated at $1.7 billion (2016 dollars), and the storm killed 73 people. The only other billion-dollar typhoon for the island was Typhoon Nari of 2001, which hit the island as a Category 2 storm with 100 mph winds, killing 104 and causing $1.1 billion in damage (2016 dollars.) Two typhoons have hit Taiwan at Category 5 strength. The first was Super Typhoon Joan, which made landfall in 1959 with 185 mph winds. Joan was Taiwan’s deadliest typhoon in recorded history, with 1046 deaths. The other Cat 5 was Super Typhoon Bilis, which intensified from a Category 2 storm with 105 mph winds to a Category 5 storm with 160 mph winds in the 30 hours before making landfall on the island on August 22, 2000. Bilis killed 14 people and did $134 million in damage to Taiwan. The island was hit by one major typhoon this year—Category 4 Super Typhoon Neparak—and by two major typhoons last year: Category 4 Typhoon Dujuan and Category 3 Typhoon Soudelor. The Central Weather Bureau of Taiwan has a list (in Chinese) of all the typhoons that have affected Taiwan.
Megi Links
Brian McNoldy has a continuously updating radar loop of Megi. It will be fascinating to watch as the storm makes landfall and gets deflected and distorted by the high mountains of Taiwan.
Stunning zoomed-in visible animation of Megi from September 26, 2016, from NOAA/RAMMB/Colorado State.
Storm chaser James Reynolds is in Taiwan and will be making live updates on Megi’s landfall on his Twitter feed.
Figure X. Satellite image of Invest 97L from Monday afternoon, September 26, 2016.
97L slowly organizing over tropical Atlantic
As it continues hustling westward at about 20 mph, the tropical wave dubbed Invest 97L is gaining latitude and organization. At 2:00 pm EDT Monday, 97L was located about 950 miles east-southeast of the Windward Islands. Considerable spin was already evident in a large swath of scattered showers and thunderstorms on 97L’s north side. The National Hurricane Center has upped the odds of 97L’s developing into at least a tropical depression to 70% by Wednesday and 90% by Saturday. The large envelope of showers and thunderstorms around 97L will make it slower to develop, but potentially more powerful once it does.
A Hurricane Hunter flight is scheduled for Tuesday afternoon into 97L, and it would not surprising if it finds that 97L is already Tropical Storm Matthew by then. Models agree that 97L will track into the southeast Caribbean, and tropical storm conditions may spread across parts of the Lesser Antilles as it does so. As noted in our morning update, there remains huge uncertainty as to 97L’s future beyond that point. The 12Z Monday operational runs of the GFS, ECMWF, and UKMET models differ on how closely 97L might come to the north coast of South America, but they agree on the general idea of a sharp northward turn through the central Caribbean by the weekend or early next week. Should this turn materialize, a landfall on the East Coast of the U.S. or Canada would be a possibility, or 97L could even head out to sea. All this will hinge on how quickly one upper-level storm system moves through the eastern United States and how quickly the next one approaches. It is far too soon to know how those midlatitude storms will evolve, and we still can’t rule out the possibility that 97L will continue across the Caribbean much farther to the southwest. One thing we do know is that 97L will have at least some of the ingredients needed to become a powerful and dangerous hurricane, including very deep warm water through much of the Caribbean as well as sea surface temperatures at or near record-warm levels across the western Atlantic.
We’ll be back with our next update on the Atlantic and Pacific tropics by late morning Tuesday.
Bob Henson and Jeff Masters
Figure 1. Iowa National Guard members walk past a local business covered in sandbags, Monday, Sept. 26, 2016, in Cedar Rapids, Iowa. Residents are waiting anxiously as a quickly rising Cedar River threatens to inundate their city with devastating floodwaters for the second time in eight years. Image credit: AP Photo/Charlie Neibergall.
The floods of 2008 eclipsed anything on record across eastern Iowa, particularly in Cedar Rapids and Iowa City. The estimated cost of that flood reached $10 billion, with more than 5000 homes and nearly 1000 business damaged. This time, the heaviest rains (more than 10” in 24 hours last Wednesday--see Figure 3 below) have been focused across the Cedar River basin north of Cedar Rapids, which is helping to keep the most serious flooding within that corridor, including Cedar Falls and Waterloo. Another plus: the flood crest heading toward Cedar Rapids in 2008 was boosted by an intense storm just one day before it peaked downtown. “That’s why the intensity of the flooding caught people by surprise. Nothing like that is in the cards [this time]” Witold Krajewski, director of the Iowa Flood Center, told me. In fact, the flood crest should arrive on Tuesday beneath sunny skies. “Because this event is well predicted, the city is well prepared,” said Krajewski.
Figure 2. An aerial image shows flood-affected areas on June 13, 2008 in Cedar Rapids, Iowa. Image credit: David Greedy/Getty Images.
Cedar Rapids since 2008: Progress and problems
In the wake of the 2008 floods, Cedar Rapids and surrounding Linn County took big strides toward preparing for future disaster. The city and county are among three pilot communities nationwide in the Resilient America project, organized by the National Academies to help communities build resilience and reduce the physical and economic toll of disasters. In Cedar Rapids, roughly 1400 flood-damaged homes were acquired by the city and removed over the last eight years. That action has already cut back on the destruction that this week’s flood might wreak. The city has also adopted a $625 million flood protection plan, including a series of new levees and floodwalls. However, these structures have yet to be built: federal funding has been authorized, but has not yet been provided. As a result, some of the areas restored in the wake of the 2008 flood are imperiled once again.
Citizen-volunteers have been pitching in this week, helping to put more than 250,000 sandbags in place to help stem the flood crest. A Facebook page devoted to the unfolding flood is helping connect people to the most pressing needs. About 100 volunteers spent Sunday removing almost 1000 seats from the historic Paramount Theatre in downtown Cedar Rapids. After being heavily damaged in 2008, the theatre was restored with federal, state, and local funds totalling $35 million.
Figure 3. A swath of 8” - 10” of rain fell on Wednesday, September 21, 2016, atop the northwest-to-southeast Cedar River basin. Enhanced by other rains over the past week, this flood crest has moved southeast past Waterloo and Cedar Falls and is now approaching Cedar Rapids (southeast of map domain). Image credit: Iowa Flood Information System/Iowa Flood Center.
A very out-of-season flood for eastern Iowa
September is not when Iowans are usually keeping an eye on flood risk. In fact, this is the first time on record that a flood of any magnitude (at least 12 feet) has been measured on the Cedar River at Cedar Rapids. Heavy rains are far more common during spring and summer across eastern Iowa. Climate change has been shown to exacerbate the intensity of the heaviest rainfall events in the United States and many other parts of the world, as warmer temperatures allow more moisture to evaporate into the atmosphere. Research led by Eugene Takle (Iowa State University) found that eastern Iowa has already seen a measurable rise in the number of days with rainfall that is typically too heavy for soils to absorb (1.25” in a 24-hour period). “We can logically conclude that enhanced streamflow and the potential for flooding are also rising,” Takle wrote. His research has also found a shift away from spring floods (as warmer spring temperatures allow for earlier snowmelt) and toward late-summer events. Storms in late summer tend to be oriented along northwest-to-southeast trajectories, which aligns them with river basins in eastern Iowa. “This seems to be the new norm for seasonal flood occurrence in the state,” noted Takle.
Figure 4. Enhanced infrared satellite image of Typhoon Megi as of 2100Z (5:00 pm EDT) Monday, September 26, 2016. Image credit: RAMMB/CIRA/CSU.
Megi intensifying as it nears Taiwan
Typhoon Megi vaulted to Category 3 strength on Monday afternoon, heightening the risk to Taiwan. As of 18Z (2 pm EDT), Megi’s top sustained winds (averaged over 1 minute) were estimated at 115 mph by the Joint Typhoon Warning Center. Satellite imagery suggests that Megi has almost completed an eyewall replacement cycle, with its small eye from last weekend now superseded by a much larger but still-ragged eye, about 35 miles in diameter. The timing of this replacement cycle is bad news for Taiwan, as Megi has had just enough time to begin consolidating very intense, widespread thunderstorms around this newly formed eye. The 21Z Monday (5 pm EDT) forecast from JTWC brings Taiwan onshore with peak winds of at least 110 mph.
Figure 5. As of 18Z (2:00 pm EDT) Monday, September 26, the center of Typhoon Megi is projected to pass through central Taiwan between 06Z and 18Z Tuesday (2:00 pm Tuesday to 2:00 am Wednesday local time). Image credit: Central Weather Bureau, Taiwan.
Although Taiwan is experienced with typhoons—it gets three to four in a typical year--Megi will be striking the island head on, with its center passing through the heart of Taiwan. This will put the northern half of the island, which includes the capital of Taipei, in the more dangerous right-hand part of Megi. All signs point to Megi being an expensive and potentially deadly disaster for Taiwan, with wind damage, massive rainfall, and landslides a good bet across mountainous eastern Taiwan and major disruption in the capital city of Taipei, at the island’s north end. As of 2:20 am local time (2:20 pm EDT), 24-hour rains had already topped 200 mm (7.87”) at Taoyuan City, just west of Taiwan. Exacerbating the flood risk will be the saturated ground produced by heavy rain from Super Typhoon Meranti and Typhoon Malakas over the last two weeks.
On its predicted course, Megi would make a second landfall as a tropical storm along the coast of southeast China, not far south of where Meranti claimed at least 29 lives and caused at least $2.6 billion in damage.
Taiwan's typhoon history
According to EM-DAT, the international disaster database, the most damaging typhoon in Taiwan’s history was Typhoon Herb of 1996, which hit the island as a Category 4 super typhoon with 150 mph winds. The eye passed directly over the capital of Taipei, and the storm unleashed rains as high as 78.23”. Damage was estimated at $1.7 billion (2016 dollars), and the storm killed 73 people. The only other billion-dollar typhoon for the island was Typhoon Nari of 2001, which hit the island as a Category 2 storm with 100 mph winds, killing 104 and causing $1.1 billion in damage (2016 dollars.) Two typhoons have hit Taiwan at Category 5 strength. The first was Super Typhoon Joan, which made landfall in 1959 with 185 mph winds. Joan was Taiwan’s deadliest typhoon in recorded history, with 1046 deaths. The other Cat 5 was Super Typhoon Bilis, which intensified from a Category 2 storm with 105 mph winds to a Category 5 storm with 160 mph winds in the 30 hours before making landfall on the island on August 22, 2000. Bilis killed 14 people and did $134 million in damage to Taiwan. The island was hit by one major typhoon this year—Category 4 Super Typhoon Neparak—and by two major typhoons last year: Category 4 Typhoon Dujuan and Category 3 Typhoon Soudelor. The Central Weather Bureau of Taiwan has a list (in Chinese) of all the typhoons that have affected Taiwan.
Megi Links
Brian McNoldy has a continuously updating radar loop of Megi. It will be fascinating to watch as the storm makes landfall and gets deflected and distorted by the high mountains of Taiwan.
Stunning zoomed-in visible animation of Megi from September 26, 2016, from NOAA/RAMMB/Colorado State.
Storm chaser James Reynolds is in Taiwan and will be making live updates on Megi’s landfall on his Twitter feed.
Figure X. Satellite image of Invest 97L from Monday afternoon, September 26, 2016.
97L slowly organizing over tropical Atlantic
As it continues hustling westward at about 20 mph, the tropical wave dubbed Invest 97L is gaining latitude and organization. At 2:00 pm EDT Monday, 97L was located about 950 miles east-southeast of the Windward Islands. Considerable spin was already evident in a large swath of scattered showers and thunderstorms on 97L’s north side. The National Hurricane Center has upped the odds of 97L’s developing into at least a tropical depression to 70% by Wednesday and 90% by Saturday. The large envelope of showers and thunderstorms around 97L will make it slower to develop, but potentially more powerful once it does.
A Hurricane Hunter flight is scheduled for Tuesday afternoon into 97L, and it would not surprising if it finds that 97L is already Tropical Storm Matthew by then. Models agree that 97L will track into the southeast Caribbean, and tropical storm conditions may spread across parts of the Lesser Antilles as it does so. As noted in our morning update, there remains huge uncertainty as to 97L’s future beyond that point. The 12Z Monday operational runs of the GFS, ECMWF, and UKMET models differ on how closely 97L might come to the north coast of South America, but they agree on the general idea of a sharp northward turn through the central Caribbean by the weekend or early next week. Should this turn materialize, a landfall on the East Coast of the U.S. or Canada would be a possibility, or 97L could even head out to sea. All this will hinge on how quickly one upper-level storm system moves through the eastern United States and how quickly the next one approaches. It is far too soon to know how those midlatitude storms will evolve, and we still can’t rule out the possibility that 97L will continue across the Caribbean much farther to the southwest. One thing we do know is that 97L will have at least some of the ingredients needed to become a powerful and dangerous hurricane, including very deep warm water through much of the Caribbean as well as sea surface temperatures at or near record-warm levels across the western Atlantic.
We’ll be back with our next update on the Atlantic and Pacific tropics by late morning Tuesday.
Bob Henson and Jeff Masters
Projection of #Flood2016 in Cedar Rapids (left: crest of 23') compared to 2008 (right: crest of 31') along the Cedar River #iawx pic.twitter.com/zS4IiCJYFJ
— Rebecca Kopelman (@KopelmanWX) September 25, 2016
The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.