CBOFS
The Chesapeake Bay Operational Forecast System (CBOFS)For decades, mariners in the United States have depended on NOAA's Tide Tables for the best estimate of expected water levels. These tables provide accurate predictions of the astronomical tide (i.e., the change in water level due to the gravitational effects of the moon and sun and the rotation of the Earth). However, they cannot predict water-level changes due to wind, atmospheric pressure, and river flow, which are often significant. CBOFS is a high-resolution hydrodynamic numerical estuarine model that simulates, by computer, the flow of water throughout the Chesapeake Bay. It incorporates tidal forcing, wind fields and coastal water levels from National Weather Service weather and ocean forecast models, real-time wind and water-level observations from the NOS Physical Oceanographic Real-Time System (PORTS®) in Chesapeake Bay, plus historical river inputs. Forecast water-levels are likely to be especially useful for the commercial shipping industry, as they can be used for transit planning up to 24 hours in advance to and from the ports within Baltimore Harbor and Hampton Roads. CBOFS complements the Chesapeake Bay PORTS® (Physical Oceanographic Real-Time System). PORTS® provides accurate real-time oceanographic and meteorological information tailored to the specific needs of local users of the Bay. CO-OPS, in partnership with local port authorities, pilot associations, the U.S. Coast Guard, the U.S. Army Corps of Engineers, the U.S. Navy, academia, and others, has implemented PORTS® in U.S. various bays and harbors to measure and disseminate real-time observations of water levels, currents, salinity, and meteorological variables (e.g., winds, atmospheric pressure). The data are relayed to the maritime user community in a variety of user-friendly formats, including, via the Internet and telephone voice response. In support of PORTS®, CO-OPS also operates the Continuous Operational Real-Time Monitoring System (CORMS), which is staffed 24 hours a day to quality-control PORTS® data and, which is able to discontinue data dissemination if its quality or accuracy are in question. Depths on NOAA's nautical charts are referenced to Mean Lower Low Water (MLLW); however, it is rare for a ship to transit an area at exactly MLLW. Normally, a ship will be travels at a water level higher than MLLW and has more water under the keel than shown on the chart. Less frequently, a vessel may transit during periods when the water level is below MLLW and have less water than charted. Access to accurate, real-time water-level data and forecast guidance from CBOFS allows U.S. port authorities and maritime shippers to make sound decisions regarding maximum tonnage (based on available bottom clearances)and passage times without compromising safety. |
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