Forecast Storm Surge Research Articles

Hurricane surge and inundation in the Bahamas, part 1: Storm surge model

AbstractA storm surge model has been developed as part of a pilot study for The Commonwealth of the Bahamas. The hydrodynamic model, TELEMAC‐2D, is used to simulate the response of water level to tide and the wind and atmospheric pressure fields of hurricanes and subsequent inundation over land. The model is used by The Bahamas Department of Meteorology to forecast storm surge and flooding over the islands of Grand Bahama and Eleuthera for incoming hurricanes to assist in preparation for and management of hurricane surge events and has been used in a flood risk assessment, reported in a companion paper. The model has been optimised to run quickly while also resolving the bathymetry and topography that affect the development and propagation of storm surge. Wind fields are generated within TELEMAC‐2D based on hurricane warning bulletins. The model has been validated for its representation of water level and against tide gauge measurements during four historical hurricanes: Irene, Sandy, Matthew and Dorian. Factors contributing to uncertainty in forecast predictions are discussed and recommendations are provided to improve the performance in future. The pilot study provides a template for future expansion to cover the other inhabited islands of The Bahamas.

Effect of waves, tides and storm parameters on water level rise through numerical simulation

In this study, the foot water is calculated by the factors of collecting parameters and tides, calculated waves are analyzed by the tidal integrated numerical model, Toring sea and storm surge (SuWAT - Surge, Wave and Tide). The SuWAT model has been applied to calculate storm surge in a number of storms that have made landfall on the northern coast (such as storms Franki-96, Washi-05, Xangxane-06, Kalmeagy-14) with some calculation options different. The results show that the influence of the tide on the rising water level is negligible in places with low tidal amplitude and with storm landing at high tide, the water will be lower than when the storm makes landfall at low tide; The water surge due to atmospheric pressure is only significant in the offshore area when the storm intensity is still strong. Meanwhile, in the area, shoreline rise due to wind stress and wave stress accounted for the majority of the total water level rise during storms. With storm parameters, the storm surge at Hon Dau station reached the maximum value with the case where the storm's movement speed was 1 hour slower than the actual one. The magnitude of the water decreased as the pressure in the storm increased, but the magnitude increased at three different stations. Water level rise at 3 stations Cua Ong, Hon Dau, and Hon Ngu increased with wind speed, however, Hon Ngu station had a higher rate of increase. The magnitude at Cua Ong station increases slowly. The water surge at Cua Ong station is dominated by wind speed more than at Hon Ngu station. The research results will be very useful in warning and forecasting storm surge in the area.

Forecasting Storm Surge and Inundation: Model Validation

Abstract Coastal regions are increasingly vulnerable to damage from storm surge and inundation. Delft3D is used by the Naval Oceanographic Office to model the ocean dynamics in the near shore. In this study, the performance of Delft3D in predicting the surge and inundation during Hurricane Ike, which impacted the northern Gulf of Mexico in September 2008, is examined. Wave height, water level, and high-water mark comparisons with a number of observations confirm that the model does well in predicting the surge and inundation during extreme events. The impact of using forecast winds based on the best-track data as opposed to hindcast winds is also investigated, and it is found that the extent of inundation is represented reasonably well with the forecast winds. In Delft3D, waves can be coupled to the hydrodynamic component using the radiation stress gradient method or the dissipation method. Comparing the results of using the two shows that for low-resolution grids such as that needed for a forecast model the dissipation method works better at reproducing the water levels and inundation.

ENSEMBLE FORECAST OF EXTREME STORM SURGE: A CASE STUDY OF 2013 TYPHOON HAIYAN

The object of this study is to evaluate an ensemble forecast of extreme storm surge by using a case of Typhoon Haiyan (2013) and its associated storm surge. A simple numerical model composed of ARW-WRF, FVCOM and SWAN is employed as a forecast system for storm surge. This ensemble system can successfully forecast storm surge 3-4 days before it happened. However, the typhoons in almost all ensemble members were underpredicted probably because of its difficulty in forecasting a track and central pressure of highly intense typhoon. This leads to the underestimation of a prediction of storm surges around Leyte Gulf. Compensating the underestimation of forecasted extreme storm surge, it can be important to not only examine the ensemble mean among members but also consider the phase-shifted manipulation and the worst ensemble member in the case where the extreme storm surge is forecasted. In addition, the ensemble forecast system can have a potential to determine the time at which the peak of extreme surge appears with a high precision.

Development of a near real-time forecasting system for storm surge and coastal inundation

ABSTRACT Yoon, J.J. and Shim, J.S., 2016. Development of a near real-time forecasting system for storm surge and coastal inundation. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 1427 - 1431. Coconut Creek (Florida), ISSN 0749-0208. Climate change is resulting in an increase in disastrous effects, such as sea level rise, intensity and frequency of storms, abnormal waves, and storm surges, in densely populated coastal areas. In particular, the coast of Korea was repeatedly damaged by storm surge and subsequent inundation caused by the approach of strong typhoons. Therefore, it is desirable to accurately forecast storm surge height and coastal inundation. In this study, a rapid, near real-time forecasting system was developed for addressing coastal inundation. A primary study of this system for operational forecasting using typhoon advisories was ...

A simplified real time method to forecast semi-enclosed basins storm surge

Semi-enclosed basins are often prone to storm surge events. Indeed, their meteorological exposition, the presence of large continental shelf and their shape can lead to strong sea level set-up. A real time system aimed at forecasting storm surge may be of great help to protect human activities (i.e. to forecast flooding due to storm surge events), to manage ports and to safeguard coasts safety. This paper aims at illustrating a simple method able to forecast storm surge events in semi-enclosed basins in real time. The method is based on a mixed approach in which the results obtained by means of a simplified physics based model with low computational costs are corrected by means of statistical techniques. The proposed method is applied to a point of interest located in the Northern part of the Adriatic Sea. The comparison of forecasted levels against observed values shows the satisfactory reliability of the forecasts.

Tolerable Time-Varying Overflow on Grass-Covered Slopes

Engineers require estimates of tolerable overtopping limits for grass-covered levees, dikes, and embankments that might experience steady overflow. Realistic tolerance estimates can be used for both resilient design and risk assessment. A simple framework is developed for estimating tolerable overtopping on grass-covered slopes caused by slowly-varying (in time) overtopping discharge (e.g., events like storm surges or river flood waves). The framework adapts the well-known Hewlett curves of tolerable limiting velocity as a function of overflow duration. It has been hypothesized that the form of the Hewlett curves suggests that the grass erosion process is governed by the flow work on the slope above a critical threshold velocity (referred to as excess work), and the tolerable erosional limit is reached when the cumulative excess work exceeds a given value determined from the time-dependent Hewlett curves. The cumulative excess work is expressed in terms of overflow discharge above a critical discharge that slowly varies in time, similar to a discharge hydrograph. The methodology is easily applied using forecast storm surge hydrographs at specific locations where wave action is minimal. For preliminary planning purposes, when storm surge hydrographs are unavailable, hypothetical equations for the water level and overflow discharge hydrographs are proposed in terms of the values at maximum overflow and the total duration of overflow. An example application is given to illustrate use of the methodology.

U.S. IOOS coastal and ocean modeling testbed: Inter-model evaluation of tides, waves, and hurricane surge in the Gulf of Mexico

[1] A Gulf of Mexico performance evaluation and comparison of coastal circulation and wave models was executed through harmonic analyses of tidal simulations, hindcasts of Hurricane Ike (2008) and Rita (2005), and a benchmarking study. Three unstructured coastal circulation models (ADCIRC, FVCOM, and SELFE) validated with similar skill on a new common Gulf scale mesh (ULLR) with identical frictional parameterization and forcing for the tidal validation and hurricane hindcasts. Coupled circulation and wave models, SWAN+ADCIRC and WWMII+SELFE, along with FVCOM loosely coupled with SWAN, also validated with similar skill. NOAA's official operational forecast storm surge model (SLOSH) was implemented on local and Gulf scale meshes with the same wind stress and pressure forcing used by the unstructured models for hindcasts of Ike and Rita. SLOSH's local meshes failed to capture regional processes such as Ike's forerunner and the results from the Gulf scale mesh further suggest shortcomings may be due to a combination of poor mesh resolution, missing internal physics such as tides and nonlinear advection, and SLOSH's internal frictional parameterization. In addition, these models were benchmarked to assess and compare execution speed and scalability for a prototypical operational simulation. It was apparent that a higher number of computational cores are needed for the unstructured models to meet similar operational implementation requirements to SLOSH, and that some of them could benefit from improved parallelization and faster execution speed.

Application of rule based methods to predicting storm surge

The accurate forecast of storm surge, the long wavelength sea level response to meteorological forcing, is imperative for flood warning purposes. There remain regions of the world where operational forecast systems have not been developed and in these locations it is worthwhile considering numerically simpler, data-driven techniques to provide operational services. In this paper, we investigate the applicability of a class of data driven methods referred to as rule based models to the problem of forecasting storm surge. The accuracy of the rule based model is found to be comparable to several alternative data-driven techniques, all of which result in marginally worse but acceptable forecasts compared with the UK's operational hydrodynamic forecast model, given the reduction in computational effort. Promisingly, the rule based model is considered to be skillful in forecasting total water levels above a given flood warning threshold, with a Brier Skill Score of 0.58 against a climatological forecast (the operational storm surge system has a Brier Skill Score of up to 0.75 for the same data set).The structure of the model can be interrogated as IF–THEN rules and we find that the model structure in this case is consistent with our understanding of the physical system. Furthermore, the rule based approach provides probabilistic forecasts of storm surge, which is much more informative to flood warning managers than alternative approaches.Therefore, the rule based model provides reasonably skillful forecasts in comparison with the operational forecast model, for a significant reduction in development and run time, and is therefore considered to be an appropriate data driven approach that could be employed to forecast storm surge in regions of the world where a fully fledged hydrodynamic forecast system does not exist, provided a good observational and meteorological forecast can be made.

Numerical model of storm surge and inundation in Bohai Bay

A two-dimensional numerical model of extratropical storm surge and inundation in Bohai Bay was built based on the unsteady flow Navier-Stokes equations. The model included two sections, one was for the simulation of storm surge tidal level and the other for the simulation of storm surge inundation in the coastal area. While simulating the storm surge tidal level, the alternating direction implicit (ADI) method was applied to dispersing and solving 2D storm surge equations. In the simulation of storm surge inundation, the 2D unsteady flow equations were dispersed and solved using the structureless grids of finite volume method (FVM). A coupling calculation mode of the process of inundation and storm surge tidal level variation was proposed, therefore the storm surge inundation process and area could be calculated while simulating and forecasting the process of storm surge tidal setup. Furthermore, an extratropical storm surge and inundation in Bohai Bay were simulated using this numerical model. Simulation results are in good agreement with the measured data, which shows that this numerical model provides a new method of simulating and forecasting storm surge and inundation in Bohai Bay.

AN EFFICIENT STORM SURGE FORECASTING TOOL FOR COASTAL MISSISSIPPI

Coupled storm surge simulations with fine resolution have become a reality due to the rapid development of computer power and advancement in the integration of the simulation models. However, the real-time application of such robust simulations is often constrained by the availability of time and computational resources. In this study, an alternative, Storm Surge Forecasting Tool (SSFT) has been developed to forecast storm surge in Coastal Mississippi. The algorithm of SSFT uses a weight based Storm Similarity Index (SSI) that is defined by current hurricane position Central Pressure (CP), Pressure Scale Radius (Rmax) along with hurricane track, landfall location, storm forward speed, and forecasted storm track published by the National Hurricane Centre (NHC) and correlated with the characteristics of synthetic storms within the underlying database. Based on the values of SSI (scales from 0 to 1), the SSFT identifies a group of storms that much as close as possible with the characteristics of the approaching hurricanes and then display high resolution simulation results (e.g., maximum surge elevation and hydrographs). The SSFT model operates in two different modes:1) Hindcasting mode and 2) Forecasting mode. The SSFT GUI was tested in both modes and we found that the method is very promising. Using this tool and approach as a decision aide, the emergency personnel can quickly forecast local storm surge along the coast of Mississippi. This will allow them to make quantitative and objective decisions by evaluating "what-if-scenarios† starting two to three days ahead of the landfall.

A high resolution forecast model of storm surge inundation

In order to forecast storm surge inundation, a two-dimensional model is established. In the model, an alternating computation sequence method is used to solve the governing equations, and the dry and wet method is introduced to treat the moving boundary. This model is easy to use. It has a friendly input interface and Arcview GIS is used as the output interface. The model is applied to the Shantou area to simulate the storm surge elevations and inundations caused by Typhoons 6903 ane 0104 using the same relevant parameters. The calculated results agree well with the observations.

Cyclone induced storm surge and flood forecasting in the northern Bay of Bengal

A cyclone induced storm surge and flood forecasting system that has been developed for the northern Bay of Bengal is presented. The developed system includes a cyclone forecasting model that uses statistical models for forecasting of the cyclone track and maximum wind speed, and an analytical cyclone model for generation of cyclone wind and pressure fields. A data assimilation system has been developed that allows updating of the cyclone parameters based on air pressure and wind speed observations from surface meteorological stations. The forecasted air pressure and wind fields are used as input in a 2D hydrodynamic model for forecasting storm surge levels and associated flooding. An efficient uncertainty prediction procedure based on Harr's point estimation method has been implemented as part of the forecasting system for prediction of the uncertainties of the forecasted storm surge levels and inundation areas caused by the uncertainties in the cyclone track and wind speed forecasts. The developed system is applied on a severe cyclone that hit Bangladesh in April 1991. The simulated storm surge and associated flooding are highly sensitive to the cyclone data. The cyclone data assimilation system provides a more accurate cyclone track when the cyclone approaches the coastline, which results in a significant improvement of the storm surge and flood predictions. Application of the uncertainty prediction procedure shows that the large uncertainties of the cyclone track and intensity forecasts result in large uncertainties of the forecasted storm surge levels and flood extend. The forecasting system shows very good forecasting capabilities up to 24 h before the actual landfall.

Storm surges in the Western Black Sea. Operational forecasting

The frequency of the storm surges in the Black Sea is lower than that in other regions of the World Ocean but they cause significant damages as the magnitude of the sea level set-up is up to 7-8 times greater than that of other sea level variations. New methods and systems for storm surge forecasting and studying their statistical characteristics are absolutely necessary for the purposes of the coastal zone management. The operational forecasting storm surge model of Meteo-France was adopted for the Black Sea in accordance with the bilateral agreement between Meteo-France and NINMH. The model was verified using tide-gauge observations for the strongest storms observed along the Bulgarian coast over the last 10 years.