Tropical cyclone forecast model
A tropical cyclone prediction model is a computer program that uses meteorological data to predict the motion and intensity of tropical cyclones. They utilize powerful supercomputers with sophisticated software and meteorological data to come up with paths and intensities. There are two general types, statistical and dynamical, and two primary types of forecasts, track and intensity.
Track Models
This is a list of track models, some of which have additional notes.
- CLIPER (CLImatology and PERsistence) is a statistical model. It uses the current path of a tropical cyclone and an average of historical paths of similar cyclones to come up with a track. Curiously, until the late 1980s, this was actually the most accurate model.
- NHC90
- BAM (Beta and Advection) uses horizontal winds. There are three forms, BAMD (BAM Deep), BAMM (BAM Medium) and BAMS (BAM Shallow) that use different altitudes of wind.
- VICBAR
- NHCP Aviation primarily predicts wind direction and speed and provides input for other models.
- GFDL (Geophysical Fluid Dynamics Laboratory)
- UKMET (United Kingdom Meteorological Office)
- NOGAPS (United States Navy Global Atmospheric Prediction System)
The above models are not 100 percent accurate because it is impossible to learn exactly everything about the atmosphere in a timely enough manner. Also, it is possible that input values are not measured totally accurately. Thus, slight variations in these inputs are used to form a consensus track.
Like all weather forecasts, track predictions are more accurate in the short-term than in the long term. Average errors for the US NHC are around 100, 200, and 300 nautical miles in 1, 2, and 3 days, respectively. This is the source of the 1-2-3 rule.
Intensity Models
This is a list of intensity models, some of which have additional notes.
- SHIFOR (Statistical Hurricane Intensity FORecast) uses the average of past storms with similar behaviour as well as an extrapolation of recent behaviour by a storm to arrive at a prediction. Until recently, this was the most consistently accurate.
- SHIPS (Statistical Hurricane Intensity Prediction Scheme) uses current conditions and past storms to arrive at a prediction.
- GFDL is the same model used in track prediction.
- RI Scheme (Rapid Intensification) uses output from SHIPS to determine the probability of rapid intensification.
As with track models, intensity models are not perfect. They increase in accuracy as the future time of the prediction approaches the present. That is, a model is more accurate in the short term than in the long term.