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Frequently Asked Questions

What are the model designations?

Model designations are given by a 3 or 4 letter abbreviation in the legends of each figure (e.g. CMC, AVNO, EGRR, etc...). A key can be found on the National Hurricane Center's Automated Tropical Cyclone Forecasting website for operational models and the National Center for Atmospheric Research's Hurricane Forecast Improvement Project website for experimental models.

What are interpolated models?

Interpolated models have a model designation that ends in an "I" if it is a model run 6-hours previous to the analysis time on the figure. The old model track and/or intensity forecast is corrected to the new position and estimated intensity. Likewise, a model designation that ends in a "2" is a model run 12-hours previous to the analysis time on the figure.

Why are there different models for different tropical cyclones?

Some models are run over specific regions or are based on the statistics over a particular ocean basin. Tropical cyclones in different parts of the world will correspondingly have different sets of guidance.

Why are some models not available after the analysis time?

There is a spectrum of models that comprise the guidance suite. Some models are simple statistical models that take a very short time to run. Other models are numerical weather prediction models that assimilate observations of the atmosphere and integrate complex equations to arrive at an estimate of the state of the atmosphere at a future time. Numerical weather prediction models take hours to run on supercomputers, and their track output is typically delayed anywhere from three to six hours after the analysis time, depending on the complexity of the model. There are also dissemination restrictions in place with a couple models.

What are model ensembles?

Model ensembles are formed by taking slightly different initial conditions and/or model physics and integrating each of these ensemble members to generate a spread of possible outcomes. Since the atmosphere is a chaotic system, small initial differences can have profound impacts on the tracks and intensities of tropical cyclones at a future time. Ensembles are used to estimate uncertainty in a forecast. Ensemble output is typically delayed six to twelve hours after the analysis time.

May I reproduce the figures on this website?

Reproduction is allowed for research and educational purposes. Reproduction is forbidden for any commercial purposes. Hotlinking figures directly to message boards and blogs is forbidden due to limited resources.

What are the data sources for the guidance?

Data is provided by the Automated Tropical Cyclone Forecasting system, the Hurricane Forecast Improvement Project, and the THORPEX Interactive Grand Global Ensemble.

Who may I contact if I have questions or comments regarding this website?

This website is maintained by Brian Tang. While questions and comments are appreciated, this website is maintained on a highly irregular basis.