Hurricane Center Research Articles

A Markov chain location-allocation meta-model for hurricane relief planning

We present a meta-model for the pre-positioning of state staging areas (SSA), activation of points of distributions (PODs), and allocation of commodities for hurricane relief. Strength and path of the hurricane are stochastic processes modelled as discrete Markov chains. Demand is also treated as a stochastic parameter. The meta-model is two models: a location model to determine SSAs to activate and a location-allocation model to determine PODs to activate and how much commodities for each of them. To solve it, we used SMOSA, a multi-objective simulated annealing heuristic, in which the initial solution and the cooling rate were determined via design of experiments. The initial temperature is irrelevant, but temperature reduction must be gradual. The Markov chains performed as well or better than forecasts made by the US National Hurricane Center (NHC), and the heuristic performed well, compared to ILP, when solving a network of 20 SSAs and 19 PODs.

Incorporating Hurricane Forecast Uncertainty into a Decision-Support Application for Power Outage Modeling

A variety of decision-support systems, such as those employed by energy and utility companies, use the National Hurricane Center (NHC) forecasts of track and intensity to inform operational decision making as a hurricane approaches. Track and intensity forecast errors, especially just prior to landfall, can substantially impact the accuracy of these decision-support systems. This study quantifies how forecast errors can influence the results of a power outage model, highlighting the importance of considering uncertainty when using hurricane forecasts in decision-support applications. An ensemble of 1,000 forecast realizations is generated using the Monte Carlo wind speed probability model for Hurricanes Dennis, Ivan, and Katrina. The power outage model was run for each forecast realization to predict the spatial distribution of power outages. Based on observed power outage data from a Gulf Coast utility company, the authors found that in all three cases the ensemble average was a better predictor of power...

The NCEP–FNMOC Combined Wave Ensemble Product: Expanding Benefits of Interagency Probabilistic Forecasts to the Oceanic Environment

The U.S. National Centers for Environmental Prediction (NCEP) and the Fleet Numerical Meteorology and Oceanography Center (FNMOC) have joined forces to establish a first global multicenter ensemble system dedicated to probabilistic forecasts of windwave heights. Both centers run independent wave ensemble systems (WES), which are combined onto a multicenter system with 41 members. A performance assessment of the multicenter wave-height product is made relative to altimeter data. Computed estimates of mean errors, ability to represent uncertainty, and reliability of probabilistic forecasts indicate that the multicenter ensemble product outperforms individual WES and deterministic wave models alike. The investigation includes an evaluation made at NCEP's National Hurricane Center (NHC) of the multicenter WES product, including severe sea-state events. The interagency collaboration has provided an opportunity to investigate in more depth the properties of wave ensembles, which has led to planned improvements ...

Real-Time Upper-Ocean Temperature Observations from Aircraft during Operational Hurricane Reconnaissance Missions: AXBT Demonstration Project Year One Results

Abstract Thousands of aircraft observations of upper-ocean thermal structures have been obtained during hurricane and typhoon research field experiments in recent decades. The results from these experiments suggest a strong correlation between upper-ocean thermal variability and tropical cyclone (TC) intensity change. In response to these results, during the Office of the Federal Coordinator of Meteorology (OFCM) 2011 Interdepartmental Hurricane Conference (IHC), the Working Group for Hurricane and Winter Storms Operations and Research (WG/HWSOR) approved a 3-yr project to demonstrate the usefulness of airborne expendable bathythermographs (AXBTs) in an operational setting. The goal of this project was to initialize and validate coupled TC forecast models and was extended to improve input to statistical intensity forecast models. During the first season of the demonstration project, 109 AXBTs were deployed between 28 July and 28 August 2011. Successes included AXBT deployment from WC-130J aircraft during operational reconnaissance missions tasked by the National Hurricane Center (NHC), real-time onboard and postflight data processing, real-time data transmission to U.S. Navy and NOAA hurricane numerical prediction centers, and near-real-time assimilation of upper-ocean temperature observations into the Naval Research Laboratory Coupled Ocean–Atmosphere Mesoscale Prediction System-Tropical Cyclones (COAMPS-TC) forecast model. Initial results showed 1) increased model accuracy in upper-ocean temperatures, 2) minor improvements in TC track forecasts, and 3) minor improvements in TC intensity forecasts in both coupled dynamical and statistical models [COAMPS-TC and the Statistical Hurricane Intensity Prediction Scheme (SHIPS), respectively].

Track and Intensity Forecasting of Hurricanes: Impact of Convection-Permitting Resolution and Global Ensemble Kalman Filter Analysis on 2010 Atlantic Season Forecasts

Abstract Twice-daily 48-h tropical cyclone (TC) forecasts were produced for the fall 2010 Atlantic hurricane season using the Advanced Research core of the Weather Research and Forecasting (WRF-ARW) model on a large 4-km grid covering much of the northern Atlantic. WRF forecasts initialized from operational Global Forecast System (GFS) analyses based on the gridpoint statistical interpolation (GSI) three-dimensional variational data assimilation (3DVAR) system and from experimental global ensemble Kalman filter (EnKF) analyses, and corresponding global GFS forecasts were intercompared. For the track, WRF forecasts show improvement over GFS forecasts using either set of initial conditions (ICs). The EnKF-initialized GFS and WRF are also better than the corresponding GSI-initialized forecasts, but the difference is not always statistically significant. At all lead times, the WRF track errors are comparable to or smaller than the National Hurricane Center (NHC) official track forecast error, with those of the EnKF WRF being smallest. For weaker TCs, more improvement comes from the model (resolution) than from the ICs. For hurricane intensity TCs, EnKF ICs produce better track forecasts than GSI ICs, with the best forecast coming from WRF at most lead times. For intensity, EnKF ICs consistently outperform GSI ICs in both models for weaker TCs. For hurricane-strength TCs, EnKF ICs produce forecasts statistically indistinguishable from GSI ICs in either model. For all TCs combined, WRF produces about half the error of the corresponding GFS simulation beyond 24 h, and at 36 and 48 h, the errors are smaller than those from NHC official forecasts. The improvement is even greater for hurricane-strength TCs. Overall, the WRF forecasts initialized with EnKF ICs have the smallest intensity error, and the difference is statistically significant compared to the GFS forecasts.

Investigating the sensitivity of hurricane intensity and trajectory to sea surface temperatures using the regional model WRF

The influence of sea surface temperature (SST) anomalies on the hurricane characteristics are investigated in a set of sensitivity experiments employing the Weather Research and Forecasting (WRF) model. The idealised experiments are performed for the case of Hurricane Katrina in 2005. The first set of sensitivity experiments with basin-wide changes of the SST magnitude shows that the intensity goes along with changes in the SST, i.e., an increase in SST leads to an intensification of Katrina. Additionally, the trajectory is shifted to the west (east), with increasing (decreasing) SSTs. The main reason is a strengthening of the background flow. The second set of experiments investigates the influence of Loop Current eddies idealised by localised SST anomalies. The intensity of Hurricane Katrina is enhanced with increasing SSTs close to the core of a tropical cyclone. Negative nearby SST anomalies reduce the intensity. The trajectory only changes if positive SST anomalies are located west or north of the hurricane centre. In this case the hurricane is attracted by the SST anomaly which causes an additional moisture source and increased vertical winds.

Skill assessment of a real-time forecast system utilizing a coupled hydrologic and coastal hydrodynamic model during Hurricane Irene (2011)

Due to the devastating effects of recent hurricanes in the Gulf of Mexico (e.g., Katrina, Rita, Ike and Gustav), the development of a high-resolution, real-time, total water level prototype system has been accelerated. The fully coupled model system that includes hydrology is an extension of the ADCIRC Surge Guidance System (ASGS), and will henceforth be referred to as ASGS-STORM (Scalable, Terrestrial, Ocean, River, Meteorological) to emphasize the major processes that are represented by the system.The ASGS-STORM system incorporates tides, waves, winds, rivers and surge to produce a total water level, which provides a holistic representation of coastal flooding. ASGS-STORM was rigorously tested during Hurricane Irene, which made landfall in late August 2011 in North Carolina. All results from ASGS-STORM for the advisories were produced in real-time, forced by forecast wind and pressure fields computed using a parametric tropical cyclone model, and made available via the web. Herein, a skill assessment, analyzing wind speed and direction, significant wave heights, and total water levels, is used to evaluate ASGS-STORM's performance during Irene for three advisories and the best track from the National Hurricane Center (NHC). ASGS-STORM showed slight over-prediction for two advisories (Advisory 23 and 25) due to the over-estimation of the storm intensity. However, ASGS-STORM shows notable skill in capturing total water levels, wind speed and direction, and significant wave heights in North Carolina when utilizing Advisory 28, which had a slight shift in the track but provided a more accurate estimation of the storm intensity, along with the best track from the NHC. Results from ASGS-STORM have shown that as the forecast of the advisories improves, so does the accuracy of the models used in the study; therefore, accurate input from the weather forecast is a necessary, but not sufficient, condition to ensure the accuracy of the guidance provided by the system. While Irene provided a real-time test of the viability of a total water level system, the relatively insignificant freshwater discharges precludes definitive conclusions about the role of freshwater discharges on total water levels in estuarine zones. Now that the system has been developed, on-going work will examine storms (e.g., Floyd) for which the freshwater discharge played a more meaningful role.

Atlantic Hurricane Database Uncertainty and Presentation of a New Database Format

Abstract “Best tracks” are National Hurricane Center (NHC) poststorm analyses of the intensity, central pressure, position, and size of Atlantic and eastern North Pacific basin tropical and subtropical cyclones. This paper estimates the uncertainty (average error) for Atlantic basin best track parameters through a survey of the NHC Hurricane Specialists who maintain and update the Atlantic hurricane database. A comparison is then made with a survey conducted over a decade ago to qualitatively assess changes in the uncertainties. Finally, the implications of the uncertainty estimates for NHC analysis and forecast products as well as for the prediction goals of the Hurricane Forecast Improvement Program are discussed.

A validation study for GPS radio occultation data with moist thermodynamic structure of tropical cyclones

We exploit the cloud‐penetrating capability and insensitivity to precipitation of the Global Positioning System radio occultation (GPSRO) technique to study the humidity environment of tropical cyclones (TCs). We focus in regions within and around the vicinity of TCs' eye, where infrared and microwave observations are difficult to acquire due to cloudiness and heavy precipitation. We use data from the National Hurricane Center TC Best Tracks to identify the location of North Atlantic TCs. The Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) Data Analysis and Archive Center provides concurrent refractivity, temperature, and humidity measurements from the Challenging Minisatellite Payload and COSMIC missions and the European Centre for Medium‐Range Weather Forecasts (ECMWF). The distribution of GPSRO‐derived humidity profiles as functions of altitude and distance from the storms' center identifies a pronounced low‐level inflow, characteristic of mature TCs, at distances between 50 and 90 km, which coincide with the area where the eyewall of TCs forms. We also capture wavelike structures resembling spiral rainbands beyond the eyewall. The distribution of water vapor as functions of altitude and TC intensity shows a decrease at all altitudes when a tropical system matures from a tropical depression to a Category 1 (Cat 1) hurricane. The water vapor gradually increases from Cat 2 to Cat 5 hurricanes—a result that is also identified in ECMWF data sets and Atmospheric Infrared Sounder observations. We conclude that GPSRO data can contribute significantly to the understanding and modeling of the vertical structures of TCs.

Transition of the Coastal and Estuarine Storm Tide Model to an Operational Storm Surge Forecast Model: A Case Study of the Florida Coast

Abstract The operational forecast demands and constraints of the National Hurricane Center require that a storm surge model in research mode be tested against a benchmark model such as Sea, Lake, and Overland Surges from Hurricanes (SLOSH) for accuracy, computation time, and numerical stability before the model is used for operational forecasts. Additionally, the simulated results must be in a geographic information system format to facilitate the usage of computed storm surge for various applications. This paper presents results from a demonstration project to explore the pathway for the transition of the Coastal and Estuarine Storm Tide (CEST) model to an operational forecast model by testing CEST over SLOSH basins in Florida. The performance and stability of CEST were examined by conducting simulations for Hurricane Andrew (1992) and more than 100 000 synthetic hurricanes for nine SLOSH basins covering the Florida coast and Lake Okeechobee. The results show that CEST produces peak surge heights similar to those from SLOSH. Additionally, CEST has proven to be numerically stable against all synthetic hurricanes and the computation time of CEST is comparable to that of SLOSH. Therefore, CEST has the potential to be used for operational forecasts of storm surge. The potential of producing more detailed real-time surge inundation forecasts was also investigated through the simulations of Andrew's surge on various grids with different cell sizes. The results indicate that CEST can produce 48-h forecasts using a single processor in about 40 min over a grid generated by reducing the cell edge size of the SLOSH grid by 4 times.

Relating the Skill of Tropical Cyclone Intensity Forecasts to the Synoptic Environment

Abstract Prior knowledge of the performance of a tropical cyclone intensity forecast holds the potential to increase the value of forecasts for end users. The values of certain dynamical parameters, such as storm speed, latitude, current intensity, potential intensity, wind shear magnitude, and direction of the shear vector, are shown to be related to the error of an individual model forecast. The varying success of each model in the different environmental conditions represents a source of additional information on the reliability of an individual forecast beyond average forecast error. Three hurricane intensity models that were operational for the duration of the five hurricane seasons between 2006 and 2010, as well as the National Hurricane Center official forecast (OFCL), are evaluated for 24-, 48-, and 72-h forecasts in the Atlantic Ocean. The performance of each model is assessed by computing the mean absolute error, bias, and percent skill relative to a benchmark model. The synoptic variables are binned into physically meaningful ranges and then tested individually and in combinations to capture the different regimes that are conducive to forecasts with higher or lower error. The results address conventional wisdom about which environmental conditions lead to better forecasts of hurricane intensity and highlight the different strengths of each model. The statistical significance established between the different bins in each model as well as the corresponding bins for other models indicates there is the potential for error predictions to accompany tropical cyclone intensity forecasts.

Atlantic Hurricane Season of 2011*

Abstract The 2011 Atlantic season was marked by above-average tropical cyclone activity with the formation of 19 tropical storms. Seven of the storms became hurricanes and four became major hurricanes (category 3 or higher on the Saffir–Simpson hurricane wind scale). The numbers of tropical storms and hurricanes were above the long-term averages of 12 named storms, 6 hurricanes, and 3 major hurricanes. Despite the high level of activity, Irene was the only hurricane to hit land in 2011, striking both the Bahamas and the United States. Other storms, however, affected the United States, eastern Canada, Central America, eastern Mexico, and the northeastern Caribbean Sea islands. The death toll from the 2011 Atlantic tropical cyclones is 80. National Hurricane Center mean official track forecast errors in 2011 were smaller than the previous 5-yr means at all forecast times except 120 h. In addition, the official track forecast errors set records for accuracy at the 24-, 36-, 48-, and 72-h forecast times. The mean intensity forecast errors in 2011 ranged from about 6 kt (~3 m s−1) at 12 h to about 17 kt (~9 m s−1) at 72 and 120 h. These errors were below the 5-yr means at all forecast times.

Improvements to the Operational Tropical Cyclone Wind Speed Probability Model

Abstract The National Hurricane Center Hurricane Probability Program, which estimated the probability of a tropical cyclone passing within a specific distance of a selected set of coastal stations, was replaced by the more general Tropical Cyclone Surface Wind Speed Probabilities in 2006. A Monte Carlo (MC) method is used to estimate the probabilities of 34-, 50-, and 64-kt (1 kt = 0.51 m s−1) winds at multiple time periods through 120 h. Versions of the MC model are available for the Atlantic, the combined eastern and central North Pacific, and the western North Pacific. This paper presents a verification of the operational runs of the MC model for the period 2008–11 and describes model improvements since 2007. The most significant change occurred in 2010 with the inclusion of a method to take into account the uncertainty of the track forecasts on a case-by-case basis, which is estimated from the spread of a dynamical model ensemble and other parameters. The previous version represented the track uncertainty from the error distributions from the previous 5 yr of forecasts from the operational centers, with no case-to-case variability. Results show the MC model provides robust estimates of the wind speed probabilities using a number of standard verification metrics, and that the inclusion of the case-by-case measure of track uncertainty improved the probability estimates. Beginning in 2008, an older operational wind speed probability table product was modified to include information from the MC model. This development and a verification of the new version of the table are described.

The Long Road to Recovery: Environmental Health Impacts of Hurricane Sandy

Building contractor John Pierciey stands in the gutted interior of a 1950s-era home in Manasquan, New Jersey. Wallboard, two layers of wood flooring, a layer of felt—all of it had to be ripped out to rid the house of mold caused by Hurricane Sandy’s storm surge. “This is the sixth house I’ve gutted in a week,” Pierciey says. “Every one is different. You don’t know what you’re going to find until you take them apart.” Residents and volunteers keep warm by a fire barrel in the New Dorp Beach neighborhood of Staten Island, 5 November 2012. Power outages persisted through a cold snap that put temperatures in the single digits. So it is with the environmental health impacts of Hurricane Sandy. Every layer of society, every type of building, has felt the impact of the storm, which struck the U.S. East Coast on 29 October 2012. Incidences of death and illness, though small in number compared with some storms, have come in many forms, the effects still unfolding as time goes by.

Eastern North Pacific Hurricane Season of 2011

Abstract Overall activity during the 2011 eastern North Pacific hurricane season was near average. Of the 11 tropical storms that formed, 10 became hurricanes and 6 reached major hurricane strength (category 3 or stronger on the Saffir–Simpson hurricane wind scale). For comparison, the 1981–2010 averages are about 15 tropical storms, 8 hurricanes, and 4 major hurricanes. Interestingly, although the number of named storms was below average, the numbers of hurricanes and major hurricanes were above average. The 2011 season had the most hurricanes since 2006 and the most major hurricanes since 1998. Two hurricanes affected the southwestern coast of Mexico (Beatriz as a category 1 hurricane and Jova as a category 2 hurricane), and the season’s tropical cyclones caused about 49 deaths. On average, the National Hurricane Center track forecasts in the eastern North Pacific for 2011 were very skillful.

Landfalling tropical cyclones on the Pacific coast of Mexico: 1850-2010

Historical documents and newspapers from Mexican Pacific states (north of 14° N) were reviewed to determine the incidence of landfalling tropical cyclones from 1850 to 1949, prior to the start of the United States National Hurricane Center database. The reviewed documents are only found in Mexican repositories at national, state and municipal level and the systematic search embarked upon in this study yielded valuable information that cannot be found elsewhere. Atime series of landfall was reconstructed back to 1850, indicating active and quiet periods. An average of 1.8 ± 1.6 landfalls per year is determined from the time series for 1850-2010. When the series is limited to 1880-2010, eliminating the first 30 years that may have some undercounting, the average increases to 2.1 ± 1.6 cases per year. Spectral and wavelet analysis of the 161 years of landfalling tropical cyclones indicates that the Pacific Decadal Oscillation (PDO) modulates the activity. The influence of El Niño/Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO) on the landfall frequency may be present throughout the reconstruction period but both oscillations have lower correlations compared to that from the PDO.

Tropical Cyclone Formation Guidance Using Pregenesis Dvorak Climatology. Part I: Operational Forecasting and Predictive Potential

Abstract While there are a variety of modes for tropical cyclone (TC) development, there have been relatively few efforts to systematically catalog both nondeveloping and developing cases. This paper introduces an operationally derived climatology of tropical disturbances that were analyzed using the Dvorak technique at the National Hurricane Center (NHC) and the Central Pacific Hurricane Center from 2001 to 2011. Using these Dvorak intensity estimates, the likelihood of genesis is calculated as a historical baseline for TC prediction. Despite the limited period of record, the climatology of Dvorak analyses of incipient tropical systems has a spatial distribution that compares well with previous climatologies. The North Atlantic basin shows substantial regional variability in Dvorak classification frequency. In contrast, tropical disturbances in the combined eastern and central North Pacific basins (which split at 125°W into an eastern region and a central region) have a single broad frequency maximum and limited meridional extent. When applied to forecasting, several important features are discovered. Dvorak fixes are sometimes unavailable for disturbances that develop into TCs, especially at longer lead times. However, when probabilities of genesis are calculated by a Dvorak current intensity (CI) number, the likelihood stratifies well by basin and intensity. Tropical disturbances that are analyzed as being stronger (a higher Dvorak CI number) achieve genesis more often. Further, all else being equal, genesis rates are highest in the eastern Pacific, followed by the Atlantic. Out-of-sample verification of predictive skill shows comparable results to that of the NHC, with potential to inform forecasts and provide the first disturbance-centric baseline for tropical cyclogenesis potential.

Hurricane preparedness and planning in coastal public school districts in the United States

One hundred school districts were surveyed along the Atlantic and Gulf of Mexico coasts from North Carolina to Texas. Nearly all had recent experience with a tropical storm or hurricane and had hurricane plans in place. About half teach hurricane preparedness to students and 85 % train staff members in hurricane preparedness. Sources of information about cyclone threats were the National Hurricane Center (91 %), local television news (74 %), The Weather Channel (67 %), and the internet (67 %). Only 36 % would cancel classes for a hurricane warning but 89 % would cancel classes for a mandatory evacuation. Most districts (75 %) would use schools as storm shelters, and 92 % would use school busses to assist in community evacuations. Districts with a higher percentage of Hispanic population provided hurricane information in Spanish. Larger school districts were less likely to cancel classes in the middle of the day for a storm threat. Districts with higher home values were less likely to use school busses for evacuations, and smaller school districts were less likely to provide schools as storm shelters. There were no other significant associations between hurricane preparedness of the districts and district demographic variables of poverty, percent black, percent Hispanic, population, district size, or median home values.

Mental Health Effects of Hurricane Sandy

On October 22, 2012, a late-season tropical system was named Sandy by the US National Hurricane Center. The system meandered for several days in warm Caribbean waters, intensifying slowly, gaining forward momentum, and passing directly over Jamaica, eastern Cuba, and the Bahamas. Sandy’s outer rain bands deluged Haiti’s deforested terrain, triggering severe floods and mudslides. Although Sandy was a minimal hurricane, millions were affected across 5 Caribbean nations and Puerto Rico, 100 persons were killed or reported missing, and thousands of homes were damaged. Estimated economic losses ranged from $5 million in Jamaica to $2 billion in Cuba.1 What catapulted this system into a “superstorm” was a rare climate event. At mid-latitudes, Sandy interacted with a polar jet stream that steered the system toward the mid-Atlantic coastline, transforming the system into a hybrid blend of posttropical cyclone and winter storm. The system’s cloud canopy expanded to 1000 miles in diameter as circulating winds funneled ocean waves into the New Jersey shoreline, Long Island Sound, and New York Harbor, inundating portions of Staten Island and southern Manhattan. In the United States, an estimated 60 million people across 24 states experienced a range of storm effects at varying intensities, including wind, rain, flood, coastal surge, and blizzard. The effects of the storm on vulnerable and fragile infrastructure produced power outages for more than 8 million residents; flooded New York City’s subway system and East River tunnels; set off a major fire that destroyed 111 housing units in the Breezy Point section of Queens; disrupted communications; and created acute shortages of gasoline, food, and commodities. Sandy was blamed for 113 US deaths and damaged 200 000 homes. Costs have been estimated at $50 billion, second only to Hurricane Katrina as the nation’s costliest natural disaster.2,3 Over the past 2 decades, considerable research efforts have been focused on populations affected by natural disasters. A rapidly growing body of knowledge is now available to assist in estimating the potential mental health effects of Superstorm Sandy and the differential risks for specific populations and communities. The availability of data from randomized controlled trials on the efficacy of interventions for trauma-exposed populations may enable better planning and implementation of prevention strategies to mitigate the adverse mental health effects of the disaster.

Geoffrey Philp, Dub Wise

Geoffrey Philp is a poet and short-story writer who was born in 1958 in Jamaica and emigrated to Miami in 1979. He has been living there ever since. His first four collections of poetry (Exodus and Other Poems, 1990; Florida Bound, 1995; Hurricane Center, 1998; and Xango Music, 2001) signalled the arrival of a major new poetic talent walking in the footsteps of Derek Walcott, Mervyn Morris, Dennis Scott and Kamau Brathwaite, among others. His most recent collection, Dub Wise (Peepal Tree Pres...