Let’s Name the Zones of the Open Sea!

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c-keymz Let’s name the zones, the zones, the zones. Let’s name the zones of the open sea! If you happen to have small children in your household, you might recognize this lyric from Finding Nemo. For others, this animated movie is about the adventures of a clownfish from the Great Barrier Reef off Australia. In any case, when I heard the lyric for the first time, my marine meteorological mind was drawn to the subject of “marine zones”. In the marine community, the term “zones” carries multiple meanings. For fishing, you no doubt are aware of Federal, State, and local “zones” which tell you what to catch, or not catch, how much, etc. Nautical charts, on the other hand, may identify hazardous “zones” such as shoals or reefs. For the weather-minded, a marine zone represents a marine weather forecast area that, more often than not, contains a similar wind and sea state. The Florida Keys National Weather Service issues marine weather forecasts for 16 such marine zones. Forecasts were issued for only nine zones just a few years ago, and before 1999, there were less than five zones covering an area of approximately 22,000 square miles. At the Florida Keys National Weather Service, we have worked diligently during the last decade to provide marine weather forecasts of both greater accuracy and precision. Obviously, forecasts are far from perfect. However, we believe that the overall quality and value of the forecasts is higher than what it was in 1999. The zone map is somewhat “busy”, with lots of colors, lines, and labels. However, if you look closely, you will notice that many of the zones have been created so that they represent areas with similar water depths (e.g., Florida Bay, Hawk Channel, or the Gulf of Mexico inside five fathoms). This was done because one of the things that influences wave growth is the depth of the water (other factors are wind velocity, wind fetch, current/swell interactions, and land interactions). The steady advances in computer technology during the last several years have allowed Florida Keys National Weather Service marine duty forecasters to employ increasingly sophisticated wave models to aid in the marine weather forecast mission. Sadly, we still lack the appropriate observational network to properly validate the models. For example, did you know that we do not have a single wave-measuring buoy in the coastal waters surrounding the Florida Keys? Nevertheless, it seems likely that the application of better wave models and more realistic marine forecast zones has resulted in improved marine weather forecasting. The following website displays the marine weather zone map along with clickable links to the appropriate Coastal Waters Forecast segment. Just click your desired location on the map. http://www.srh.noaa.gov/key/?n=marine Upon clicking, you will access a page providing a weather synopsis, Gulf Stream location information, and a five-day marine weather forecast. The synopsis is intended to be a concise, understandable description of surface weather features that may cause significant winds and seas over the forecast area during the forecast period, including identification of the strength, trend, and movement of each major weather system affecting the area. The Gulf Stream information includes identification of the approximate shoreward edge of the Gulf Stream referencing eight landmarks along the Florida Keys and Reef tract between Loggerhead Key (Dry Tortugas) and Carysfort Reef. The information is derived from a Naval Oceanographic Office satellite-based analysis usually performed three times per week (Mondays, Wednesdays, and Fridays). Finally, the five-day marine weather forecast includes forecasts of wind speed and direction, significant wave height (“seas”), and precipitation intensity and coverage. Forecast periods are 12 hours in length, with the daytime periods covering the interval between 6:00 a.m. and 6:00 p.m., and the nighttime periods covering the interval between 6:00 p.m. and 6:00 a.m. (all local times). An alternative presentation of the marine weather forecasts can be obtained by viewing the “Hourly Weather Graph” at the following link: http://www.srh.noaa.gov/key/ ?n=marineweathergraph You will notice that the actual names of the Florida Keys marine weather zones are quite descriptive, at the risk of even being verbose (e.g., Straits of Florida from Craig Key to west end of Seven Mile Bridge 20 to 60 nautical miles out). If you have a chance, check out the “Shipping Forecast” from the British Broadcasting Corporation (BBC). Nearly the same style and presentation has been used for decades. Most of the zone names are only one word long, and the entire forecast rarely contains more than 15 words. The BBC Shipping Forecast reads almost like poetry, even when mentioning strong gales and high seas. The Florida Keys National Weather Service marine forecasts are issued at least four times per day, and updated more frequently during rapidly changing weather regimes. National Safe Boating Week is May 18–24. Remember to be weather-ready and stay safe!


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