Using a Weather Service on Your Next Passage - SailNet Community
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Using a Weather Service on Your Next Passage

Had the trawler "Sea Wolf" departed Mt. Desert Island, Maine, for Charleston, South Carolina, on Saturday, September, 3,1994, as the vessel's captain planned, it would have experienced clear skies and calm seas for the first 36 hours and then, by late Sunday, would have been battling 40-knot winds, with gusts to 50 knots and seas 6 to 12 feet.

Fortunately, Sea Wolf had engaged a weather service which warned the trawler's captain of a low-pressure center developing near Cape Hatteras and intensifying as it moved northeast toward New England's coastline. Since the system had potential to produce storm-force winds and very rough seas, Sea Wolf's captain followed the weather service's advice and delayed departure until later in the week. As predicted, the low developed into a storm affecting coastal waters from Block Island to Nova Scotia. By delaying departure, Sea Wolf experienced an uneventful and pleasant trip later in the week.

Many boat owners and captains consider themselves knowledgeable in the science and art of weather prediction and do not feel the need for weather advice. But, unless you have access to satellite imagery and know how to interpret it, weather data, forecast model output and some training in meteorology, it will be difficult to carry out the long range forecasting and route planning that a marine meteorologist can provide.

Imagine sitting at anchor in St. George's Harbor in Bermuda contemplating departure for the Azores, your next stop on a transatlantic cruise. Weather offshore, though, east of Bermuda has you concerned.

Recently a series of low-pressure systems have been tracking across the North Atlantic, bringing high seas and overcast skies as far south as 35 degrees north latitude. Now, as you sip your coffee and peer out over the harbor, the weather looks good, barometric pressure is up to 1035 mb, but do you really have a weather window?

In hopes of solving your dilemma-to leave or not to leave, you pick up a surface weather chart from the Bermuda pilot office. It seems to show surface features with several fronts, but there are few isobar lines, scant wind arrows and no wave or swell data. You would like to find a meteorologist to answer questions such as: Where are the lows north of Bermuda heading? Are they strengthening or weakening? Should you depart today and if so, what direction should you head to take advantage of wind and seas?

Navy, Coast Guard and commercial shipping have been using weather-routing techniques for years, as have ocean racers, both power and sail. Looking back in history, an early confirmation that weather prediction and routing is useful was the Normandy D-Day invasion. Allied meteorologists found a12-hour weather window, sandwiched between two powerful North Atlantic low-pressure systems, which allowed the massive invasion to take place. Today, 50 years later, advancements in meteorology allow precision routing of small vessels on both long and short voyages.

If you become a regular customer with a specific company, they will start a file on you, building a data base from which they can track your voyages and further tailor forecasting and routes provided to you.

Where do weather routers obtain their information? They depend on the US National Weather Service and European Meteorological Center for raw data, satellite imagery and computer modeling of weather systems. But they each apply their own knowledge and experience to customize forecasts and resolve differences that often arise between various models, raw data and on-scene reports.

How do you choose a router and when should you call for a forecast?
Ask the potential routers to send you detailed information and costs on all their services. Choose one that feels right and then establish an account with them so that when you call for a forecast, they are expecting to hear from you and will already have all the background information needed on your boat and route requirements.

A company's physical location has no effect on their ability to produce forecasts, since they receive data and imagery via phone and data lines. They provide accurate weather forecasts for any location on the earth.

Michael Carr is offline  
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