This winter season has been fluctuating in temperatures across the United States. With period of warmer spring-like temperatures and more seasonable winter temperatures occurring it can lead to winter flooding scenarios and ice jams on the rivers. Winter flooding can happen anywhere in the United States. Ice jams, coastal flooding and rapid snowmelt all can lead to winter flooding.
An ice jam is defined as pieces of floating ice on a river that are carried by the current which accumulate to obstruct the flow of the river. Ice jams form commonly just around the river bend and the mouths of tributaries. A tributary is a river or stream that flows into a larger basin of water like a lake or ocean. Ice jams form downstream of dams and upstream of bridges or obstructions because that is where there is a decrease in the river’s slope. The season for ice jams are usually late winter until early spring due to the fluctuation in temperatures. The constant melting and refreezing of liquid surfaces.
Ice jams can be defined in two ways. Freeze up jams which occur in early winter and break up jams that occur in early spring. Freeze up jams don’t usually cause much flooding but the breakup jams in early spring tend to cause the most damage and flooding. These break up jams lead to significant property damage like ripping houses off foundations and wooden decks.
Snowmelt contributes towards winter flooding because it adds water to the ground that drains in the same way that regular rainfall does. According to the National Weather Service in Des Moines, IA, on average one inch of fresh snowfall holds approximately a tenth of an inch of water so ten inches of snow could lead to five inches of water in the springtime. Other factors of snowmelt and winter flooding include high soil moisture from autumn, elevated stream levels, moderate-heavy rainfall while snow melting is occurring, and ice jams.
With this winter changing so rapidly it's important to keep an eye on any rivers or streams that may be rising suddenly. Paying attention to local weather reports and guidance from your local National Weather Service will help you be prepared for any ice jams or winter flooding!
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Photo Credit: NWS Riverton
© 2020 Meteorologist Shannon Scully
It has been a soggy May across much of New York State. As a result, Lake Ontario water levels are near an all-time high. According to the International Joint Commission who oversees monitoring of the lake level, the level of Lake Ontario is predicted to surpass levels last seen in 2017. Currently Lake Ontario is tied for its monthly record high at 248.92 feet and is less than an inch away from the record height of 248.95 feet.
This level of water is concerning to the communities around the lake. Many towns have begun to prepare for significant flooding with sandbags. Wake warnings for boaters around the shoreline have also been put in place to avoid more water flowing onto shore. According to the Army Corps of Engineers weekly Great Lakes water level update, Lake Ontario has risen 21 inches since April. This is a vast difference compared to the other Great Lakes which have seen water rise by 5-8 inches. These water levels are from a combination of the wetter-than-average conditions in the region and the uncontrolled, record high inflows from Lake Erie. Forecasts predict that the water levels on Lake Ontario are expected to crest over the following weeks, approximately within an inch of the records seen in 2017.
Water levels on Lake Ontario are predicted to crest in the next few weeks. If the beginning of the summer months experiences above-average precipitation, similar to this past May, then water levels could rise higher. The International Lake Ontario-St. Lawrence River Board are putting plans into action to provide relief for the communities along the lake that are taking the brunt of the damaging flooding.
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© 2019 Meteorologist Shannon Scully
Photo Credit: NOAA Great Lakes Environmental Research Laboratory
NOAA Great Lakes Environmental Research Laboratory
Army Corp of Engineers
International Lake Ontario- St.Lawrence River Board
International Joint Comission
On February 17th, 2019, many regions along the Mississippi River rose above their flood stages. At this current time, many locations along the river are still above flood stage. Vicksburg, located in Warren County, Mississippi along with other regions near the Mississippi River, is experiencing the longest, above flood stage duration since the Great Flood of 1927. In Baton Rouge, Louisiana, flood waters have risen and remained above the 35-foot flood stage level throughout the past few months. In Red River Landing, Louisiana, flood waters have also risen and remain above the 48-foot flood stage level. As of May 14th, 2019, over 260 river gauges throughout the Midwest have recorded river flooding levels above the flood stage, categorized as minor, moderate, and major flood statuses, as detailed in the diagram below.
Factors leading to this historic flooding event have been rapid melting of snow and intense rainfall in the Midwest regions. Because of this rapid snow melt and intense rainfall, runoff from these sources has absorbed into the soil so quickly that oversaturation has prevented normal seepage. The soil is then unable to dry out in time before another rainfall event occurs. Therefore, this runoff has nowhere else to go. The runoff flows downslope into the Mississippi River, filling and flooding the Mississippi. Hydrologists believe that flooding in this region of the Mississippi is caused in part due to sediments being deposited onto the floor of the riverbed. The buildup of these sediments has caused flood waters to rise higher than they would have in previous years. Since February 2019 to present day, various regions along the Mississippi River have remained well above the flood stage, making this the longest lasting flood in over 90 years.
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© 2019 Weather Forecaster Christina Talamo
DISCUSSION: Flooding is a major problem around the world. For example, flooding along the Missouri River in the north-central U.S. wreaked havoc recently (see article below this one here). In addition, Cyclone Idai recently made landfall in Mozambique, flooding a very large area and killing hundreds of people. The picture above illustrates the flooding impacts of Idai in Africa (credit: Mike Hutchings/Reuters).
In the U.S., the Federal Emergency Management Agency (FEMA) provides flood risk maps. These maps not only provide information on locations most at risk for flooding, they also are the basis for National Flood Insurance Program premiums. These FEMA-produced flood maps focus on the risk from a 100-year flood (i.e., a flood that on average occurs once every century or has a 1% chance of occurring in any given year), and many of these maps haven’t been updated in a long time. Higher-resolution, more accurate maps of topography (useful for correctly depicting where water will flow) are now available that could improve the accuracy of FEMA flood maps. In addition, there are several issues with recurrence intervals and associated flood risk maps based on those intervals. These intervals are highly dependent on observation record. So, as the record continually gets longer, homes not previously in the 100-year flood plain can find themselves at risk for such a flood. In addition, recurrence intervals assume that conditions are stationary with time (e.g., no construction has occurred on the flood plain that could restrict water flow) and that all floods are from the same source (e.g., all floods are from heavy rains from a tropical cyclone) both of which are rarely true.
FEMA flood maps can be a useful tool to provide some indication whether there is a significant flood risk at your house/business in the U.S. But, it is important to know the limitations of this tool so that the maps can be applied and used correctly. While FEMA is limited by funding and Congress to update their flood maps, work is continuing outside FEMA to create updated, more versatile (i.e., provide risk of flooding from a range of flood sizes, not just a 100-year flood) flood maps for not only the U.S., but across the globe. These maps may be very useful for planning and preparing for floods, thus lessening future flood damages and fatalities.
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© 2019 Meteorologist Dr. Ken Leppert II
Source: The Atlantic/Herschel Talley / Nebraska National Guard / Handout via Reuters
The State of Nebraska, along with several nearby states, is slowly recovering from one of the most extreme flooding events in recent memory. According to USA Today, the estimated losses across the entire Great Plains region now falling somewhere around $1.5 billion
These losses include everything from agricultural operations to residential properties, as the Missouri and Mississippi Rivers, along with several other rivers along their basins, struggled to keep up with the amount of water flowing through them. As the cleanup continues along some parts of the Great Plains, others are still experiencing flooding issues as flood waters descend all along the region’s watersheds. Many questions have been raised in the days following some of the worst observed flooding conditions, including why it was that conditions deteriorated to such an extreme point. Essentially, it was the overlap of several meteorological events that aided in turning this flooding event in particular into one for the record books.
We begin by first exploring a bomb cyclone, which typically refers to any low pressure system that has experienced bombogenesis, a process in which the central pressure of a cyclone drops 1mb per hour within the span of a 24-hour period. And while these cyclones tend to develop primarily in the ocean, they can develop inland at times, as was the case with the Great Plains bomb cyclone of March 2019.The entire region, especially the high and northern Plains, all experienced everything from blizzards to strong winds and torrential rains.
Source: NEXRAD Imagery
Then there are low-level jets, or LLJs, which similarly develop whenever a strong pressure gradient is experienced in the Great Plains as divergent upper-level air masses are transported by an upper-level disturbance, or wave, into an area of strong low-level convergence. In other words, as the pressure drops over the region the airmass overhead allows for air to speed up while air closes to the surface reacts by ascending to fill the void. When air parcels from the Gulf of Mexico enters these sorts of wind motions, their water content is then advected, or transported, over into the Plains, resulting in heavy precipitation.
The third and final phenomenon is, of course, snow-melt; this bomb cyclone developed right as that part of the country was beginning to warm up following a period of very cold and snowy conditions. As such, when more precipitation moved in and temperatures continued to warm, the already saturated surface was introduced to even more water, leading to an increased stress on it and the rivers all along the northern and central Plains.
Source: The Atlantic/ Shutterstock / Aspects and Angles
As the record-breaking bomb cyclone developed on the lee-side of the Rocky Mountain during the early-to-mid part of March of this year, the low-level jet and its ability to transport moisture into the region, and the subsequent melting of snowpack across the region during a relatively short period of time owing to warmer temperatures during this time of the year, Nebraska in particular experienced severe flooding all across the state. And as the region continues to recover, it is times like these that one can look back and see how weather events, such as these, are not made up of one single entity, but are in fact the products of several ingredients coming together at the right place and time. As the states in the Midwest impacted by the flooding continue to recover, there are many ways to help including donations to the local, regional and national flood relief organizations and the American Red Cross .
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© 2019 Meteorologist Gerardo Diaz Jr.
USA Today: https://www.usatoday.com/story/news/nation/2019/03/19/historic-midwest-flooding-nebraska-mike-pence-visit/3209623002/
Flood Relief Efforts: https://www.1011now.com/content/news/HOW-TO-HELP-Nebraska-flood-victims-507197401.html
For most people, December means it’s the holidays. It’s a time that is spent either shopping, eating, or simply being with family. However, this time of year means something else for those in low-lying areas along the US coastlines. It means king tide.
Before diving into how king tide affected West coast residents just this past December, it is important to understand what king tides are and how they differ from normal tides. The semi-annual tide, also known as the perigean spring tide, occurs when the Moon’s perigee (the point when it is closest to earth in its orbit) coincides with the alignment of the Moon, Sun, and Earth. Being semi-annual, it usually occurs once in the summer and once in the winter, with the most recent one being right around Christmas of 2018. It is the highest high tide of the year for most coastal locations. Given the high predictability of king tides, meteorologists are often able to issue the necessary flood warnings well in advance.
The most important takeaway though, when it comes to king tides, is that they are not caused by climate change. King tides occur on a perennial basis, always at roughly the same time of year, and have occurred throughout human history. However, king tides are reaching areas farther inland than they have previously, and this factor may very well be because of the melting of freshwater and mountain glaciers, which are causing sea levels to rise. Factor in warming seas, which are causing thermal expansion (heat expands, so warmer oceans will rise more), and you have worsening king tides. It’s something that was noted in the Bay Area just this past December, when warmer-than-normal water temperatures in the Pacific Ocean along the coast may have caused ocean waters to crest several inches above tidal gauges. The average temperatures for the Pacific in Northern California in December are around 55 degrees Fahrenheit; this December, the Pacific averaged in the upper-50s, with parts of Monterey Bay edging the 60 degree mark.
While the West coast saw the most recent king tides, it’s the low-lying East and Gulf Coasts that are seeing the most severe flooding from king tides. An official with the Environmental Protection Agency, whose hometown is among those affected by extreme king tides, attempted to document the increase in king tide flooding through a blog post back in 2013. He found inland areas of the town were flooding more frequently, and this was especially prevalent in the aftermath of Hurricane Sandy. This area is now situated in Federal Emergency Management Agency’s highest flood zone category.
Further down the coast, in Virginia’s Hampton Roads region, residents have been feeling the effects of king tide flooding for years. In fact, king tide flooding often occurs on normal, fair weather days, leading them to be colloquially known as “sunny day” tides. This has been detrimental to local infrastructure, travel, and even the economy. Local officials are often forced to close roads and divert traffic away from the coast as a safety precaution. It’s something that isn’t new, says Jeff Orrock, the Meteorologist-in-Charge at the local National Weather Service office in Wakefield. “In general, sea level rise across Hampton Roads has been rising at a rate of 4 to 6 millimeters per year”, said Orrock. He indicated this was an average, and that there have often been periods of higher sea level rise, ultimately causing king tides to become more noteworthy. “King tides are more of an issue and we reach nuisance flooding on a much more frequent basis now than just 10 to 20 years ago. We even issue more flood advisories and warnings than just 10 to 20 years ago.”
Ten years ago isn’t a long time, but it has given some coastal residents time to prepare and organize local, and even statewide movements. Oregon residents have joined forces with the international King Tide Project, an Australian-founded initiative that motivates everyday citizens to document their local king tide, post it online and share it for others to see. The movement was founded in order to provide people with an idea of what type of tidal flooding will be normal in the future, should sea level rise and other climate change phenomenon continue at their current pace. In the meantime, residents along the U.S. West coast are preparing for two more king tides, one around January 21st and another in February, both predicted to be more than a whopping ten feet.
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© 2018 Weather Forecaster Jacob Dolinger
DISCUSSION: Over the past year and counting, there is no debate that a good portion of both the contiguous United States as well as Hawaii (even as disconnected from the United States mainland as it is), has not had any shortage of tropical cyclone activity. On that note, it is important to acknowledge the fact that with a good portion of this tropical cyclone activity also came with the shattering of state rainfall records in North Carolina, South Carolina, Texas, and Hawaii. During the past 12 months, the world watched as Hurricane Harvey impacted southeast Texas, Hurricane Lane impacted parts of southern and central Hawaii, as well as Hurricane Florence which severely impacted North Carolina and South Carolina.
It goes without saying that with four states breaking tropical cyclone event rainfall records within the time-span of 12 months there are plenty of legitimate questions which are raised throughout the community. First and foremost, whether future climate change will make such events more and more common with time. The simple answer to this question is the fact that someone cannot pin any given event on various impacts of current and future climate change.
Therefore, to attribute that some given percentage of a tropical cyclone’s rainfall is directly connected to climate change would be a premature statement since any one event may have be impacted in a subtle manner from warmer-than-average sea-surface temperatures and other factors such as favorable mid/upper-level jet stream dynamical support. Thus, there are manners by which a tropical cyclone can be positively influenced with respect to an increasing intensity feedback loop but there should never be an assumption for there to be a direct connection between tropical cyclones rainfall records and climate change.
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© 2018 Meteorologist Jordan Rabinowitz
DISCUSSION: There is no debate that the biggest ticket issue during both the pre-landfall, landfall, and post-landfall phases of Hurricane Florence, then Tropical Storm Florence, and now Tropical Depression Florence was the persistent flooding event which unfolded. It is worth noting that many towns and cities across North Carolina and South Carolina got so much rain, that they broke all-time 24-hour rainfall records as well as rainfall records from a given tropical cyclone event. Thus, it goes without saying that the flooding impacts from Hurricane Florence across this part of the Mid-Atlantic region of the United States will go down as one of the worst flooding events from a tropical cyclone landfall in recorded history for the United States.
The worst part about this ongoing flooding situation is precisely the fact that it is still going on right now with more rainfall still coming down heavily across a good portion of North Carolina, Virginia, West Virginia, and beyond right at this very moment. Hence, this flooding still far from over with more rainfall on the way. Attached above is a brief video briefing which details a good portion of why this ongoing flooding event from what is now Tropical Depression Florence is indeed so historic in the context of recorded history with respect to both general flooding events as well as tropical cyclone-based flooding events.
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© 2018 Meteorologist Jordan Rabinowitz
The Return of the Jökulhlaup… Or is it? (Photo Credits: Sharon Sullivan, NWS Juneau, Alaska- Pacific River Forecast Center)
Water begins to cover the Skater’s Cabin walkway to Mendenhall Lake Thursday morning July 19, after reports that Suicide Basin to the side of Mendenhall Glacier had released. Mendenhall Glacier in the background (Sharon Sullivan)
The jökulhlaup has struck again. Jökulhlaup (“yo-kel-yawp”) comes from the Icelandic word meaning “glacial run”. This unique annual flooding event in Southeast Alaska results from a glacial dam outburst from Suicide Basin, located about 2 miles up from the eastern side of the Mendenhall Glacier. The basin is like a bowl with an opening on the bottom. The exit is normally sealed with ice, allowing rainwater and glacial melt to collect during the spring and summer months. Once the weight of the water becomes too great for the icy seal, it is lets loose and sends a surge of water through the drainage system below the glacier into the Mendenhall Lake. Floods can occur all at once or have multiple releases. The first jökulhlaup occurred in 2011, with 2016 being the largest.
An abrupt change in the basin’s water level near the end of June 2018 indicated that Suicide Basin was beginning to drain. Upon further examination, a calving event with a chunk of ice 1/5 of a mile wide disrupted the cycle by splashing into the basin and displacing the sensor, similar to dropping an ice cube into a glass of water. The calving event seemed to strengthen the dam holding the water in place, but a flood watch was issued as a precaution. By July 17, the water level in Suicide Basin had dropped overnight, but there was no response from Mendenhall Lake. Waters began responding by rising accordingly for the lake and the Mendenhall River on Wednesday, July 18 as glacial water flowed overtop the wall of ice surrounding the Mendenhall Glacier. By 10 am, a flood watch was in effect for the Mendenhall Lake area, with an expected 12 foot crest by Thursday evening and the potential for record flooding. At 8 am on July 19th, a flood warning was issued by NWS Juneau when the current stage level reached 8.99 ft. The flood stage for Mendenhall Lake is 9 feet.
Major flood stage of Mendenhall Lake occurs at 14 ft. The highest recorded water levels on the lake occurred in 2016, when the jökulhlaup caused the lake to reach heights of 11.99 feet (Alaska- Pacific River Forecast Center)
The crest occurred at 4:30 pm at 10.92 feet, tying for the 3rd highest lake level (11.99 feet in 2016), which was lower than the crest that was predicted. Significant flooding was reported along view drive and water inundated the Mendenhall Campground. According to the NWS Hydrologic Prediction Center, water levels begin dropping at a rate of about 3.5 inches per hour. The Mendenhall Campground, which had been evacuated the previous day was back open as of 9 am Friday. As of 11 am Friday, people were once again setting up their tents and enjoying the sunshine.
It is difficult to predict when the jökulhlaup will happen during the summer and if significant flooding will occur, but it is important that people are aware of the threat and prepare accordingly. In any flooding event, residents are advised to keep an emergency bag with important documents, dry foods, tools, and medication to take on the go. If you see water on the roadways, do not proceed to drive through it, as water may be deeper/ faster than you estimate. And, in the case of a jökulhlaup event, glacial waters can reach below freezing so hypothermia may become a threat. The response to the flooding went generally well due to a collaborative effort between the National Weather Service office in Juneau, the River Forecast Center, the Forest Service to evacuate the campgrounds, USGS river gauges, and the Department of Transportation’s thorough inspections on important bridges and roadways every year. Dynamics of a glacier in a changing climate, unknowns in the basin water levels, and small sample sizes may lead to varying crest heights and timing, but significant progress has been made since 2011 to better understand, forecast, and monitor this phenomena.
(Follow-up: On August 8th, the Mendenhall Lake and River were once again under Flash Flood Warnings as a significant heavy rain event over the northern panhandle and some additional contributions from Suicide Basin increased waters past flood stage).
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©2018 Meteorologist Sharon Sullivan
“The Flooded Stairway to Nowhere” (Sharon Sullivan)
In the last two weeks, Japan has been inundated with rainfall totaling over 70 inches in areas over the extreme southwestern part of the country. This has been cited as one of worst flooding disasters to ever occur there. The flooding rains have lead to numerous landslides as well as rivers overflowing their banks which has caused immense damage to cities and villages. The death toll has risen to 200 and continues to rise by the day, with another 54 people that remain unaccounted for. The Hiroshima and Okayama Prefecture areas took the brunt of the storms, with rainfall rates exceeding three inches per hour at times. Japan’s Shikoku Island was also hit hard. The Associated Press reported that 10.4 inches of rain accumulated in its Kochi Prefecture in just three hours, with more than 70 inches of rain totaling at the end of the storm system. The World Meteorological Organization reports that the total precipitation at many of the observation sites reached two to upwards of four times the annual mean which also happens to be the monthly precipitation for the month of July in southwestern Japan.
Japan is no stranger to natural disasters, with the catastrophic tsunami in 2011 that caused the meltdown at the Fukushima Daiichi Nuclear Power Plant. The scenes of the flooded landscapes with rooftops just barely visible this past week eerily resembles the aftermath of the 2011 tsunami.
In the case of this storm, the torrential rainfall can be blamed on a combination of events occurring. Tropical moisture was pulled north, colliding with the remnants of Typhoon Prapiroon as well as colliding with a front stalled over Japan. While uncommon to occur, the atmospheric conditions were just right in this case, creating multiple storms behind the parent thunderstorms. This process had the storms lining up and inundating the same region over and over, causing the massive landslides and flooding to occur instantaneously.
While natural disasters are bound to happen throughout the world even without climate change existing, the continuous acknowledgment as well as educating others on this matter will really make a difference on tackling these problems in the world.
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©2018 Weather Forecaster Michael Ames