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NOAA SLOSH
Background
Addresscloud offers comprehensive coverage of key perils for the US and these are sourced from a number of trusted, high quality data providers with a proven track record of providing data to the insurance industry. This section focuses on Sea, Lake and Overland Surges (SLOSH) from Hurricanes data. provided by the National Oceanic and Atmospheric Administration (NOAA). The data you see in Addresscloud are as they are provided by NOAA without any derivations or modelling from Addresscloud.
Introduction to NOAA SLOSH
The Sea, Lake, and Overland Surges from Hurricanes (SLOSH) model, developed by the National Oceanic and Atmospheric Administration (NOAA), is a sophisticated computational tool designed to estimate storm surge heights and potential flooding levels resulting from hurricanes. The model is a vital part of the United States' hurricane preparedness and response strategy, providing crucial data that informs emergency management, evacuation planning, and public safety decisions. This summary will delve into the SLOSH model's development, components, functioning, applications, limitations, and its significance in mitigating the impacts of hurricanes.
SLOSH has been applied to the entire U.S. Atlantic and Gulf of Mexico coastlines. In addition, coverage extends to Hawaii, Puerto Rico, the U.S. Virgin Islands, and the Bahamas. The SLOSH model coverage is subdivided into 37 regions or basins. These basins represent sections of coastline that are centred upon particularly susceptible features: inlets, large coastal centres of population, low-lying topography, and ports.
Development and Purpose
The SLOSH model was first developed in the 1960s and has since undergone continuous refinement to enhance its accuracy and reliability. It was created in response to the need for a robust tool to predict the storm surges associated with hurricanes, which are often the most destructive component of these natural disasters. The model aims to provide real-time forecasts and historical simulations of storm surge inundation, thereby helping communities prepare for and mitigate the adverse effects of hurricanes.
Components and Structure
The SLOSH model comprises several key components:
1. Grid System : The model operates on a polar grid system, which is more efficient for the curvilinear paths that hurricanes typically follow. This grid is tailored to specific basins, such as coastal regions, lakes, and inland areas susceptible to storm surge flooding.
2. Bathymetry and Topography Data : Accurate bathymetric (underwater depth) and topographic (land elevation) data are essential inputs. These datasets help define the physical landscape over which the storm surge will travel, influencing the water's movement and accumulation.
3. Meteorological Forcing : The model uses meteorological data, including hurricane track, size, wind speeds, and atmospheric pressure. These parameters drive the model's calculations, determining how the storm's characteristics affect the surge.
4. Numerical Algorithms : The core of the SLOSH model consists of numerical algorithms that solve fluid dynamics equations. These equations describe the behaviour of the storm surge, taking into account factors like wind stress, Coriolis force, pressure gradients, and frictional effects.
Functioning of the Model
The SLOSH model functions through a series of computational steps:
1. Initialization : The model is initialised with the current or predicted hurricane parameters, including the storm's central pressure, radius of maximum winds, forward speed, and track.
2. Computation of Wind Field : The wind field around the hurricane is computed based on the input parameters. This wind field is a crucial driver of the storm surge, as the winds push water towards the coast.
3. Water Level Calculations : The model calculates the resulting water levels by solving the hydrodynamic equations. It accounts for the wind-driven setup, wave setup, and other contributing factors to determine the surge heights at various locations within the grid.
4. Inundation Mapping : The computed water levels are translated into inundation maps, showing the extent and depth of flooding across the affected area. These maps are vital for understanding the potential impact on infrastructure, homes, and evacuation routes.
How often are SLOSH basins updated?
Currently, SLOSH basins are being updated at an average rate of 6 basins per year. SLOSH basin updates are ultimately governed by the Interagency Coordinating Committee on Hurricanes (ICCOH). The ICCOH manages hazard and post-storm analysis for the Hurricane Evacuation Studies under FEMA's Hurricane Program.
Updates are driven by a number of different factors. These factors include changes to a basin's topography/bathymetry due to a hurricane event, degree of vulnerability to storm surge, availability of new data, changes to the coast, and addition of engineered flood protection devices (e.g., levees).
The National Weather Service's Meteorological Development Laboratory (MDL) incorporates the latest topography/bathymetry and other data in the basin building process. These updates are provided to the National Hurricane Center's Storm Surge Unit in order to conduct storm surge simulation studies.
Applications
The SLOSH model has a wide range of applications in hurricane preparedness and response:
1. Forecasting and Real-time Decision Making : During an active hurricane, the model provides real-time forecasts of storm surge levels, aiding emergency managers in making informed decisions about evacuations and resource allocation.
2. Evacuation Planning : Historical simulations using the SLOSH model help identify areas at risk of flooding, guiding the development of evacuation plans and the designation of evacuation zones.
3. Risk Assessment : The model's outputs are used in risk assessments for coastal infrastructure, such as bridges, roads, and utilities, ensuring that these structures are designed to withstand potential storm surge impacts.
4. Public Awareness and Education : Inundation maps and risk assessments generated by the SLOSH model are used to educate the public about the risks associated with hurricanes and the importance of evacuation orders.
Limitations
Despite its strengths, the SLOSH model has several limitations:
1. Resolution and Scale : The model's grid resolution can limit the precision of its predictions, particularly in complex coastal areas with intricate topography and bathymetry.
2. Simplified Physics : While the model captures the primary drivers of storm surge, it simplifies some physical processes, which can lead to inaccuracies in certain scenarios, such as rapid changes in storm intensity.
3. Dependence on Input Accuracy : The accuracy of the model's predictions is highly dependent on the accuracy of the input data, particularly the hurricane's track and intensity forecasts.
4. Exclusion of Waves : The SLOSH model does not account for wave action, which can significantly impact surge heights and coastal erosion. This omission can lead to underestimation of the total water levels in some cases.
Significance
The SLOSH model is a cornerstone of the United States' hurricane preparedness strategy. Its ability to provide accurate and timely storm surge forecasts has saved countless lives and reduced property damage by enabling better preparedness and response. By integrating the latest meteorological data and leveraging advanced computational techniques, the model helps communities anticipate the impact of hurricanes and take proactive measures to protect residents and infrastructure.
Future Directions
Continued advancements in computing power, data collection, and meteorological science will likely enhance the SLOSH model's accuracy and utility. Integrating the model with other predictive tools, such as wave models and climate projections, could provide a more comprehensive understanding of hurricane impacts. Additionally, efforts to improve the resolution and accuracy of input data will further refine the model's predictions, making it an even more valuable resource for hurricane preparedness and response.
In conclusion, the SLOSH model from NOAA is a critical tool in the arsenal against hurricane-induced storm surges. Its detailed simulations and real-time forecasting capabilities provide essential information that helps safeguard lives and property in vulnerable coastal regions. As technology and science continue to evolve, the SLOSH model will remain an indispensable asset in the ongoing effort to mitigate the devastating effects of hurricanes.