Appendix G Data Buoy Impacts on Warning and Forecast Operations
Thomas Ainsworth, National Weather Service, Western Region
Data buoys provide reliable real-time (hourly) meteorological and oceanographic data to NWS forecasters and the general public. Moored data buoys in the eastern Pacific have repeatedly provided crucial upstream intelligence in support of all Western Region warning and forecast programs, in both coastal and inland areas. At least half of all NWS marine warnings are based principally on buoy (and C-MAN) data. Sea pressure, pressure tendency, and wind observations from buoys are also used for synoptic warnings for inland areas of the Western Region. Buoy data accurately assesses storm strength, wind speeds, and sea conditions before storms make landfall and permit forecasters to compare NCEP model prognoses to ground truth.
Consider:
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- published in the next morning's edition of newspapers (with graphical explanations), still 9–12 hrs before the height of the storm which produced 100+ mph winds on the coast and verified high wind warnings east of the Cascade Mountains.
Marine customers have repeatedly explained to WR NWS offices their primary requirement for buoy data is for ensuring the safety of their crew and passengers onboard. Several examples of customer input received over the years include:
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West coast radars are ineffective in assessing meteorological and oceanographic conditions in the coastal zone because of their base elevation (as high as 7500 ft in southern Oregon) and beam blockage by mountainous terrain. Coverage patterns by the Portland and Medford, Oregon, radars exclude the central Oregon coastal waters completely. Without buoy data, ground truth information of offshore conditions would be very difficult to assess. Denying forecasters the benefits of buoy data would directly affect the way NWS offices support news media, citizens with commercial and recreational marine interests, coastal residents, harbor masters, and other government agencies.
All NDBC-operated data buoys measure wind speed, direction, and gust; barometric pressure; air temperature; sea surface temperature; wave height; and wave period. No other instrument provides forecasters with spectral wave information. Along with the spectral energies, measurements such as significant wave height, wave steepness, average wave period, and
dominant period are also derived from buoy observations. NDBC recently began posting on its home page an experimental, automated sea-swell separation method based on the energy spectra. In addition to their use in operational weather forecasting, warnings, and atmospheric models, moored buoy data are used for scientific and research programs, during emergency response to chemical spills, in legal proceedings, and in engineering design. Sea truth observations from buoys help calibrate remotely sensed measurements from spacecraft. Fisherman and sailors on ocean-going vessels, both commercial and recreational, depend on NOAA Weather Radio broadcasts of buoy observations for purposes of crew and passenger safety, and use buoy observations in deciding whether to leave port.
The loss of NOAA data buoys does not leave NWS forecasters, and the numerous other consumers of buoy data, completely without data. There are other instruments available that provide some data from the marine environment in much different fashions than moored buoys and are not intended to supplant the information currently reported by buoys.
Drifting buoys are not yet equipped to measure wind velocity or sea state off the west coast yet. There have been documented cases where sea-level pressure data from drifting buoys have improved surface analyses; however, problems persist in communicating even limited drifting buoy data to forecast offices in a timely fashion.
Ships participating in the volunteer observing ships program provide helpful surface meteorological reports from the large data sparse areas between buoys. However, ship reports differ considerably from fixed buoy reports. Winds are measured as high as 30 meters off the surface. Because of the ships' movement, reports come from a different location each time, which may affect pressure tendency reports. Sea state conditions reported by ships are estimated by the crew, not measured. Ocean vessels (smartly) divert around storms and thus vacate areas from which forecasters are most interested in receiving observations. Satellite imagery and their derived products complement surface weather observations. In fact, satellite and surface observations are both considered indispensable tools in meteorology and oceanography. Satellites provide basic cloud imagery and low-level cloud and fog imagery 24 hours per day, which greatly assists forecasters determining storm motion and intensity trends (deepening and weakening). Not only do they provide imagery, but they also compute wind velocity from cloud motions at several levels, and provide worldwide operational sea ice analyses, and SST analyses. Satellites do not measure wave conditions, and satellite-derived wind data are not used by numerical wave prediction models. Generally speaking, satellite estimates of surface conditions (e.g., wind, ice, SST) are limited to cloud-free regions (or nearly cloud free). Where there
is significant weather, storm clouds prevent satellites from “seeing” and reporting surface weather observations.
Operational meteorology in recent years has come to rely more and more on products from numerical weather prediction models. NWS generates ocean wind and wave model forecasts with a number of sea surface weather observations available in near real ground truth of actual conditions. This sort of blind acceptance would likely lead to more “surprise” developments. In summary, documented cases in which ground truth buoy data improved NWS warnings and forecasts over numerical model guidance are available. The lead time for hurricane wind force warnings over inland portions of the Western Region as long as 24 hours are due, in large part, to data supplied by offshore buoys.
Years of interactive outreach efforts by NWS field offices with mariners and coastal residents are highlighted by a common conclusion: the safety and livelihood of these customers depend on reliable buoy reports. Lives have been saved by citizens heeding NWS warnings and data buoy reports of hazardous weather conditions. Customer reaction to potential buoy losses is always negative. The value of data buoys must not be weighed solely on their contribution to numerical atmospheric prediction models. They are deemed extremely important to NWS forecasters and citizens alike.
