David Burch - Ocean Navigator

11 Feb

The New Revolution in Tide and Current Predictions

David BurchNavigation, Ocean Voyaging, Offshore Safety, Offshore Sailing, Power Voyaging, Seamanship & Navigation, Seamanship & Navigation Newsletter

We had one tidal revolution in 2021 when NOAA announced that they were discontinuing the decades-long use of Table 2 lists of secondary station corrections, and that there will no longer be any sanctioned annual Tide and Current Tables. Plus there will no longer be any international tidal data published by NOAA. Going forward, the way we get official tide and current predictions is go to tidesandcurrents.noaa.gov and create a monthly or annual table for specific stations as PDFs and then print them. It takes four pages per year, per station. This is a superior system, as we rarely needed…

Squall Forecasts

David BurchNewsletter, Weather

It is likely known that we can get GRIB formatted wind and pressure forecasts from numerical weather models such as GFS. But it is probably less known that we can get usable squall forecasts as well. We get this from the output parameter composite reflectivity (REFC), often called “simulated weather radar,” which is effectively what it is. Once we are in an area of squalls, we can watch them and maneuver around or with them using our marine radar, but it is often valuable to know when they are likely, how severe they might be, and how they will move.…

How to Weave a Barometer into Navigation

David BurchNavigation, Ocean Voyaging, Voyaging Skills, Weather

Even in the age of high-speed internet at sea, remarkable weather model forecasts, and satellite wind measurements, our knowledge of the correct atmospheric pressure, and how it changes with time, remains the key to safe, efficient routing decisions. Pressure data are also the most direct means of evaluating the model forecasts that we ultimately rely on for routing. Productive barometer use in navigation is a relatively new concept — it was actually used more effectively in the 1700s than in the 1900s. The Barometer Handbook explains its interesting history and its role in marine navigation. The major change came when accurate, affordable…