February 26, 2014
New Hurricane Model Can More Accurately Predict Storm Path, Intensity
Brett Smith for redOrbit.com - Your Universe Online
When Hurricane Sandy slammed into southern New Jersey in October 2012, it had essentially confounded both the NOAA's Global Forecast System (GFS) and the European Centre for Medium-Range Weather Forecasts (ECMWF).
"For this particular study aircraft-based Doppler radar information was ingested into the system," said Fuqing Zhang, a professor of meteorology at Penn State. "Our predictions were comparable to or better than those made by operational global models."
In addition to incorporating real-time Doppler radar information, the convection-permitting hurricane analysis and forecasting system (WRF-EnKF) also uses high-resolution cloud-permitting grids, which allow for the consideration of individual clouds in modeling a storm system.
"Our model predicted storm paths with 100 km -- 50 mile -- accuracy four to five days ahead of landfall for Hurricane Sandy," Zhang said. "We also had accurate predictions of Sandy's intensity."
The new model runs 60 storm forecasts simultaneously as a collection, each with differing starting conditions. To evaluate the Hurricane Sandy forecast information, the scientists separated the 60 simulations into three groups: good, fair and poor. This was designed to segregate uncertainties in the model primary conditions. Zhang said that errors occur because of variances in the primary steering-level winds in the tropics that Sandy was baked into, instead of a mid-latitude trough – an area of reasonably low atmospheric pressure – ahead of Sandy's path.
"Though the mid-latitude system does not strongly influence the final position of Sandy, differences in the timing and location of its interactions with Sandy lead to considerable differences in rainfall forecasts, especially with respect to heavy precipitation over land," the researchers explain in their report on the model that was published in the Journal of Advances in Modeling Earth Systems.
The study team said Hurricane Sandy is ideal for analysis due to its unusual path for an Atlantic tropical storm, which does not typically roll northwest into the mid-Atlantic or New England. While established models performed reasonably well, the WRF-EnKF model appeared to be very promising in predicting path, intensity and rainfall – the researchers said.
A study published in October found that climate change may eventually keep hurricanes like Sandy from making a sizeable impact on US coastlines.