XTRP is very different from other computer models.

XTRP, which stands for eXTRaPolated, is an extrapolation of a tropical cyclone's future track if a system were to continue its current motion and speed at a constant rate. While it is not technically a computer model, the XTRP line is often incorporated into tropical computer model graphics to be used as a comparison to other computer models. The XTRP line, since it simply uses 2 variables, heading and speed, is always a straight line. Unlike other computer models, the XTRP forecast should not be taken as seriously as other computer models and is not used by the National Hurricane Center to forecast tropical systems.