2014 Hurricane Preparedness Week – Day 5
The Forecast Process
The National Hurricane Center (NHC) is responsible for forecasting all tropical cyclone activity in the Atlantic and Eastern Pacific basins around North America. The NHC forecasts the track, intensity, size, and structure of tropical cyclones, storm surges, rainfall, and tornadoes associated with tropical cyclones, and the likelihood of tropical cyclone formation within 48 hours. The overall skill of these forecasts is shown in the section on Hurricane Forecast Model Accuracy. Once a tropical cyclone forms, NHC staff follows a set of procedures to generate a set of forecast products and then communicate those products outside of NHC every six hours. While the NHC forecast process is the focus here, other agencies responsible for tropical cyclone forecasting in other ocean basins [link to Hurricane Forecast Regions and Centers] follow similar procedures, but their procedures are tailored to the needs of their areas of responsibility and are guided by the observational, modeling, and forecast dissemination capabilities of those areas.
The next step in the forecast process involves analyzing all of the data gathered by the various observational platforms. The observations are examined, quality controlled, and then used to initialize a suite of hurricane forecast models, often referred to more generally as numerical prediction (NWP) models. These hurricane forecast models create objective, computer-generated predictions of a hurricane’s future track and intensity.
Results from hurricane forecast models (and ensembles generated from the individual models) are interpreted and then used as guidance to create official hurricane forecasts and warnings. Each model has a different way of representing atmospheric processes and will sometimes produce very different results. Therefore, forecasters must evaluate the strengths and weaknesses of each model’s output before producing their official forecast. To do this evaluation, the forecasters compare the forecast models’ results to the current and recent environmental observations. Hurricane forecasters then use their experience and judgment to decide how to use the individual and ensemble model guidance to produce the best possible forecast.
Tropical cyclone forecasts and warnings are coordinated between the national centers and local forecast offices to provide consistency, which is important when a tropical cyclone landfall is imminent. After the NHC issues a forecast, local NWS Weather Forecast Offices (WFOs) use the information to tailor their local forecasts. The NHC cannot produce forecasts tailored to the conditions at every location on the coast, so it is important to contact your local WFO for current and predicted local effects of a hurricane.
Information for local WFOs is provided to local and state emergency management, as well as the media. Emergency managers are the final decision makers in the forecast process. They are tasked with ordering evacuations, preparing the local community, and staging resources. For the general public, television, radio, the Internet, and NOAA weather radio are all outlets for important hurricane information.