Diana the Computer Model
August 03, 2001
In a key step toward improving hurricane prediction, scientists at the National Center for Atmospheric Research (NCAR) in Boulder, Colo., have reproduced in a computer model the fine- scale structure that drives the birth and strengthening of tropical cyclones. The image above is a simulation of hurricane Diana which struck North Carolina in 1984. The simulation, which used the NCAR/Penn State (University) Mesoscale Model, Version 5 (MM5), marks the first time a cloud- resolving simulation has been able to reproduce the formation of a tropical cyclone, given only information about atmospheric conditions on a scale much larger than that of the cyclone. Computer models used for day-to-day weather prediction have become increasingly adept at projecting a hurricane's motion. Yet even the best models have little skill in predicting intensity, especially the rapid strengthening often noted in the most powerful hurricanes. Part of the problem is that the compact core of a hurricane, including the spiral bands of showers and thunderstorms that gather and focus energy, can't be modeled in sufficient detail on the computers and models used for everyday forecasting. The new Weather Research and Forecasting Model and more powerful computers will allow for the type of fine-scale detail in the MM5 to be simulated for daily forecasting.