Operational Forecasting of Wind-Generated Waves by Hurricane Isabel at NCEP*

Abstract

The accuracy of the operational wave models at the National Centers for Environmental Prediction (NCEP) for sea states generated by Hurricane Isabel is assessed. The western North Atlantic (WNA) and the North Atlantic hurricane (NAH) wave models are validated using analyzed wind fields, and wave observations from the Jason-1 altimeter and from 15 moored buoys. Both models provided excellent guidance for Isabel in the days preceding landfall of the hurricane along the east coast of the United States. However, the NAH model outperforms the WNA model in the initial stages of Isabel, when she was a category 5 hurricane. The NAH model was also more accurate in providing guidance for the swell systems arriving at the U.S. coast well before landfall of Isabel. Although major model deficiencies can be attributed to shortcomings in the driving wind fields, several areas of potential wave model improvement have been identified.

South China Sea wave characteristics during typhoon Muifa passage in winter 2004

“…Since the modelgenerated H S fields compared well to the satellite observed H S fields along several T/P tracks (figure 14 in Chu et al, 2004), we only show the comparison on the 25 crossover points for illustration. Tolman et al (2005) also demonstrated the capability of WW3 in simulating wave characteristics in the western North Atlantic Ocean with hurricane Isabel 2003. Figure 9 shows the comparison of H S between WW3 result and T/P observation with a total of 38 data pairs.…”

“…Following NCEP's operational wave prediction in the western North Atlantic Ocean during Hurricane Isabel (Tolman et al, 2005), a regularly spaced longitude-latitude grid with spacing 0.25° is used. This is also due to the comparable resolution (0.25°) in the QuikSCAT winds, which is much coarser in the JTWC data (see Table 1).…”

“…8). Similar to Chu et al (2004) and Tolman et al (2005), the comparison was conducted along the passages and crossover points. The same wave (WW3) and wind (QTCWPM) models with QuikSCAT winds were used to simulate the wave characteristics during TY Muifa's passage from 0000UTC on 16 November to 0600UTC on 25 November 2004 (this study) and TY Rumbia from 0000UTC on 2 December to 0600UTC on 9 December 2000 (Chu et al, 2004).…”

Surface Gravity Wave Modeling in Tropical Cyclones

“…The results from their simulations are compared with buoy observations and NASA SRA data, which were obtained on 24 August 1998 in the open ocean and on 26 August when the storm was approaching the shore. While the model results yielded good agreement with observations of directional spectrum as well as significant wave height, dominant wavelength, and dominant wave direction (wavelength and direction at the peak frequency of the wave spectrum) excluding shallow areas near the shore, later studies found that WAVEATCH III overestimates the significant wave height under very high wind conditions in strong hurricanes [38][39][40]. These studies attribute this error to the overestimations of the drag coefficient (C d ) used in the wave model at very high winds.…”

Wave Probabilities Consistent with Official Tropical Cyclone Forecasts

“…Traditionally, third-generation spectral ocean wave models such as WAVEWATCH III (Tolman 1991;Tolman et al 2002) are run with global numerical weather prediction (NWP) model surface winds to produce significant wave height forecasts. However, the resolution of the global NWP models is often insufficient to capture the steep wind gradients associated with TCs, so there are applications to infuse more detailed TC structure from higher-resolution NWP models into the global NWP model wind fields used as input to WAVEWATCH III (e.g., Tolman et al 2005), which can result in more realistic wave fields in the vicinity of the TC (e.g., Chao and Tolman 2010).…”