GWAM 4.0

NOGAPS 10 meter analysis and forecast wind speed (m/s) is verified using
Moored Buoy observed wind speed (m/s) in the North Pacific, and Atlantic.
Verification indicates NOGAPS slightly underanalyzes and underforecasts10
meter wind speeds stronger than 10 m/s, especially in coastal, nearshore
locations. The NOGAPS 10 meter wind speed negative bias above 10 m/s
increases with increasing observed wind speed and forecast time.

GWAM 4.0 analysis and forecast significant wave height (H1/3) is verified
using moored buoy observed wave height (H1/3). GWAM typically exhibits a
minor positive bias for H1/3 wave heights below 2.5 m. Above 2.5 m, GWAM
H1/3 exhibits a definite negative bias, especially in coastal, nearshore
locations. The negative bias increases with increasing moored buoy H1/3
wave height 3 m or greater.

Approximately seventy-two moored buoys are clustered into twelve regions (7
EPAC/Hawaii and 5 GulfMex/WATL/ England) for verification. In general,
NOGAPS 0 hour wind speed shows slight under-analysis bias for open-ocean
buoy regions (GulfAk, NEPac, Hawaii, FlaCapeHat and England). Negative wind
speed bias is greatest at 0 hour in the near-shore and coastal buoy regions
(BCCan, OreWash, NorCal, SouCal and GulfMex).

GWAM H1/3 negative bias is related to under-analysis, propagation and
forecast of long period swell energy that has moved into a buoy cluster
region. Long-period swell-wave diffusion has been noted in several WAM
research studies and publications as being responsible for under
propagating and underforecasting long-period swell-wave energy.

H1/3 negative bias is minimum in the open-ocean buoy cluster regions where
wind-wave energy is usually greater than swell-wave energy. H1/3 negative
bias is greatest in swell dominated regions such as the West Coast (BCCan,
WashOre, NorCal and SouCal) and Tropics (Hawaii).