NSSL’s mobile radar part of debris flow project in North Carolina

IPHExDebris flows caused by rainstorms are a frequent and devastating hazard in the Southern Appalachian Mountains of North Carolina.  Through June, NSSL is partnering with the Integrated Precipitation and Hydrology EXperiment (IPHEX) to understand warm season precipitation caused by complex terrain in the area, and the relationship between precipitation patterns and hydrologic processes.

Current precipitation estimates are significantly poor in the inner mountain region of the Southern Appalachians where National Weather Service WSR-88D radar data is used in hydrologic forecast models.  NSSL researchers are collecting data with the NOAA X-Pol (NOXP) mobile radar in the Pigeon River watershed basin of North Carolina until mid-June to test the role of gap-filling radars to better define rainfall runoff for these models.

Since 2007, a high elevation tipping bucket rain gauge network has been recording observations in the Pigeon River Basin. Instruments that measure microphysics have also been used during intensive observing periods in this and surrounding river basins during different seasons, focusing on ridge-ridge and ridge-valley variability. These observations have helped define the variability of rainfall intensity and accumulation at scales ranging from annual to daily.

So far, researches have discovered the importance of light (<3 mm/hr) rainfall as a baseline freshwater input to the region, and that the active depth of the atmosphere varies considerably in space from ridge to ridge.

Results from the modeling work have identified coalescence as a driving process in warm light to moderate rainfall. The localized importance of the region’s persistent fog interacting with low level clouds has also been identified. The fog and cloud interactions intensify and even trigger precipitation events that are often experienced only at high elevations and contribute significantly to the yearly water budget in the region.

The data gathered by NSSL will help researchers improve the accuracy of models used to predict flash floods and debris flows.

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CI-FLOW total water level system prepared for test by Hurricane Sandy

Researchers with the Coastal and Inland Flooding Observation and Warning (CI-FLOW) project are preparing for Hurricane Sandy to test their total water level system in North Carolina this weekend. The CI-FLOW system captures the complex interaction between rainfall, river flows, waves, tides and storm surge, and how they impact water levels in the Tar-Pamlico and Neuse Rivers and the Pamlico Sound in North Carolina.

CI-FLOW collects data from a computing system that combines radar and rain gauge information to create estimates of rainfall.  This information is passed on to water quantity models that simulate freshwater flows from the headwaters of the basins into the rivers; taking into account soil type, slope of the land and vegetation patterns.  Finally, water flow data is passed from river models to a coastal circulation and storm surge model that provides simulations of waves, tides and storm surge.

National Weather Service forecasters will have access to CI-FLOW during Hurricane Sandy to help them evaluate the system for application in the flood and flash flood warning process.

The CI-FLOW project is motivated by NOAA’s critical forecast need for detailed water level predictions in coastal areas and has a vision to transition CI-FLOW research findings and technologies to other U.S. coastal watersheds.

The NOAA National Severe Storms Laboratory with support from the NOAA National Sea Grant Office leads the unique interdisciplinary team including the North Carolina, South Carolina, and Texas Sea Grant Programs, University of Oklahoma, Renaissance Computing Institute (RENCI), University of North Carolina at Chapel Hill, Seahorse Consulting, NWS Forecast Offices in Raleigh, and Newport/Morehead City, NWS Southeast River Forecast Center, NOAA’s Coastal Services Center, NOAA in the Carolinas, NOAA Southeast and Caribbean Regional Team (SECART), NOAA-Integrated Ocean Observing System, Department of Homeland Security, Center of Excellence-Natural Disasters, Coastal Infrastructure and Emergency Management, Centers for Ocean Sciences Education Excellence SouthEast, Coast Survey Development Laboratory and NWS Office of Hydrologic Development.

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CI-FLOW provided useful predictions of total water level during Hurricane Irene

CI-FLOW predicted water levels above sea level (ft) issued at 1500 UTC 27 August 2011 (approximately at time of hurricane landfall) overlain with Hurricane Irene's track in coastal eastern North Carolina. Maximum predicted water levels occurring on the western side of the barrier islands of 6-8 feet compared within +/- 1 foot of the observations. Highest predicted inundation amounts occur in the Neuse and Tar River outlets to the Pamlico Sound.

The Coastal and Inland Flooding Observation and Warning (CI-FLOW) project began producing real-time 84-hour simulations of total water level in coastal North Carolina from Hurricane Irene on August 23, 2011.  CI-FLOW is the first system to capture the complex interaction between waves, tides, river flows, and storm surge to produce total water level simulations.  Hurricane Irene made landfall near Morehead City, N.C.

Impressive predictions of water level and inundation are shown in the image to the left.  This information was available to forecasters before landfall.  CI-FLOW total water level simulations were compared with water levels observed during the storm.  Researchers found a high level of agreement in both the timing and water level heights for the Tar-Pamlico and Neuse River coastal watershed.

The Raleigh NWS Weather Forecast Office (WFO) shared CI-FLOW information with critical decision makers in briefings and conference calls, including highlighting the CI-FLOW predictions displayed on the public domain Coastal and Emergency Risks Assessment (CERA) web site.  A Raleigh WFO said: “Several of us referred to and viewed various CI-FLOW products. The one product I used the most was the storm surge simulation.”  A forecaster from the Newport/Morehead City WFO said, “I received a call for a storm surge forecast from the Emergency Management office at MCAS Cherry Point early Thursday morning. I relayed to them an expected water level height of 6-8 feet there based on the forecast hydrograph at that location during that time. I did stress that the information was to be used as guidance only given the experimental nature of the data, but I felt comfortable enough with the forecast based on my personal experience of observing water levels on the Neuse to consider it reasonably reliable.”

The North Carolina governor Beverly Perdue has stated preliminary losses from Hurricane Irene topped $400 million.  President Barack Obama signed a disaster declaration for coastal North Carolina.  Hurricane Irene inflicted some of its worst damage in that state by pushing the water from the estuarine sounds up against the western edge of the barrier islands and the Tar and Neuse river outlets to the Pamlico Sound.

A diverse group of local, state, regional, academic and federal partners, and emergency management communities formed CI-FLOW with a united goal to improve flood predictions and warnings. The consortium includes NOAA’s National Severe Storms Laboratory, the North Carolina, South Carolina, and Texas Sea Grants, National Sea Grant, University of Oklahoma, Renaissance Computing Institute (RENCI), University of North Carolina at Chapel Hill, Seahorse Consulting, NWS Forecast Offices in Raleigh, and Newport/Morehead City, NWS Southeast River Forecast Center, NOAA’s Coastal Services Center, NOAA in the Carolinas, NOAA-IOOS, DHS-DIEM, Centers for Ocean Sciences Education Excellence SouthEast, NWS Office of Hydrologic Development, and NOS Coast Survey Development Laboratory.

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