The Operational GFDL Coupled Hurricane–Ocean Prediction System and a Summary of Its Performance

Abstract

The past decade has been marked by significant advancements in numerical weather prediction of hurricanes, which have greatly contributed to the steady decline in forecast track error. Since its operational implementation by the U.S. National Weather Service (NWS) in 1995, the best-track model performer has been NOAA’s regional hurricane model developed at the Geophysical Fluid Dynamics Laboratory (GFDL). The purpose of this paper is to summarize the major upgrades to the GFDL hurricane forecast system since 1998. These include coupling the atmospheric component with the Princeton Ocean Model, which became operational in 2001, major physics upgrades implemented in 2003 and 2006, and increases in both the vertical resolution in 2003 and the horizontal resolution in 2002 and 2005. The paper will also report on the GFDL model performance for both track and intensity, focusing particularly on the 2003 through 2006 hurricane seasons. During this period, the GFDL track errors were the lowest of all the dynamical model guidance available to the NWS Tropical Prediction Center in both the Atlantic and eastern Pacific basins. It will also be shown that the GFDL model has exhibited a steady reduction in its intensity errors during the past 5 yr, and can now provide skillful intensity forecasts. Tests of 153 forecasts from the 2004 and 2005 Atlantic hurricane seasons and 75 forecasts from the 2005 eastern Pacific season have demonstrated a positive impact on both track and intensity prediction in the 2006 GFDL model upgrade, through introduction of a cloud microphysics package and an improved air–sea momentum flux parameterization. In addition, the large positive intensity bias in sheared environments observed in previous versions of the model is significantly reduced. This led to the significant improvement in the model’s reliability and skill for forecasting intensity that occurred in 2006.

Tropical cyclone predictions over the Bay of Bengal using the high‐resolution Advanced Research Weather Research and Forecasting (ARW) model

“…The GFDL model incorporates ocean-atmospheric coupling using the Princeton Ocean Model, improved physics, vortex initialization and fine horizontal resolution. Bender et al (2007) provided a summary of the GFDL model advancements and its performance for the Atlantic and east Pacific TCs. The average track errors of the GFDL model are reported to vary from 72 km at 12 h to 340 km at 72 h for the Atlantic cyclones from 1996 and 2005.…”

Storm surge and wave simulations in the Gulf of Mexico using a consistent drag relation for atmospheric and storm surge models

“…A still commonly used drag coefficient in those models, some of them were developed in the past, is based on a relation, according to which the magnitude of the coefficient is either constant or increases monotonically with increasing surface wind speed (Bender, 2007;Kim et al, 2008;Kohno and Higaki, 2006). The NWP and surge models are often tuned independently from each other in order to obtain good results.…”

Tropical cyclone track forecasting techniques ― A review

“…The improvements include coupling the atmospheric component with the Princeton Ocean Model (POM) and increasing the vertical and horizontal resolution (Bender et al, 2007). In 2003 the vertical resolution was increased from 18 to 42 vertical levels and this change resulted in a considerable improvement in track forecast accuracy both for shorter and longer-term forecasts (Bender et al, 2007). Currently this model is run four times a day on Silicon Graphics supercomputers with 5248 Itanium processors.…”