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Weather by the yard

Dec 14, 2009

There are numerous ways to obtain a weather “briefing” for a voyage. You can listen to the full cycle of a broadcast on the local VHF/FM National Oceanic and Atmospheric Administration (NOAA) weather channel. That will usually suffice for a day trip or even for a sail of a few days duration — unless things are forecast to change rapidly, in which case multiple checks will be in order. If the trip will extend over several days spend some time examining the weather products available on NOAA’s National Weather Service (NWS) Web site (www.nws.noaa.gov).

Begin with a check of the “Warnings” tab in the left navigation panel (data for the entire continent and by state or county). The satellite image for your area (under “Observations”) will provide a picture of the general situation (check both the Infrared and Water vapor images). Click on “Radar” to view any current precipitation in your area. The “Surface Weather” tab provides access to reports from Automated Surface Observing System (ASOS) reports that will provide a nowcast (what’s going on at the moment). Click on “Forecasts, Local” and select your area to gain access to graphical forecasts, radar, satellite and a weather map. (ASOS reports are also available from most airports and can be accessed by telephone.)

If planning a voyage that will last for more than a few hours click on “Forecasts, Aviation” and select “Prog Charts” and then “Surface” for the latest surface analysis and forecast maps for the next 48 hours. The low level SFC-240 chart will provide access to weather maps that show significant weather for the continental U.S., and under the “Extended Forecast SFC Prog” heading is a 30, 36 and 48-hour look ahead. The aviation “Winds/Temps” tab will show the current and forecast surface wind speed, wind streamlines, temperature and temperature differences across the continent and offshore for hundreds of miles.

The next step is to check the current temperature, wind and sea state conditions for the area in which you plan to sail. If your voyage will be in one of the areas served by the Physical Oceanographic Real-Time System (PORTS) you can access the weather and navigational data on their Web site (http://tidesandcurrents.noaa.gov/ports.html) or by telephone. Although primarily intended as a safety and efficiency aid for commercial vessel operators, the real-time tide, current, wind velocity, temperature and barometric data is a valuable asset for anyone on the water. The PORTS system is custom designed for each location. A list of the 18 existing installations is posted on the Web site. Reports are available both on the Web and via a voice data response system, making it accessible via a cell phone. An example of coverage can be seen on the online image that shows the eight reporting sites that comprise the PORTS of Narragansett Bay.

Real-time weather from buoys
Real-time information for many areas in coastal U.S., international and foreign waters is also available from NOAA’s National Data Buoy Center (www.ndbc.noaa.gov/ index.shtml), which is an amazing window on the world’s marine weather. The site’s opening page presents a world map showing the world-wide distribution of data-reporting buoys and automated land sites; in the Indian Ocean, across the Pacific and the Atlantic and those off the north coast of Alaska. Manage the screen image as you do when using Google Earth, use the zoom and scroll keys to select the reporting station of interest; click to see its station number, operator identity, location (lat/long) and the latest report of on-site conditions.

The diamonds on the screen are color coded — yellow for buoys with current data, orange for those that have only historical data and red for those that have not reported during the past eight hours. A mouse click on a buoy symbol will open an initial data window. Click on the “View Details” block to view pages of data, including the latest NWS forecast for the area, observations from nearby stations and ships and the latest satellite wind map. You can also access the data via the “Mobile Access” tab. Click, select the station ID or region in which you are interested and then select from the list of reporting points (95 are listed under the Florida tab). Alternatively, click on Google Maps and zoom-in on the buoy or reporting point of interest. For example, Station 44032, buoy EE004 on the Central Maine Shelf, a part of the Gulf of Maine Ocean Observing System, a two-meter diameter discus buoy, reporting wind direction and average and gust speed, wave height and period, atmospheric pressure and trend, air and water temperature and visibility. Heading for Bermuda? Click on BEP86, a NOAA reporting station located on the Esso Pier in Bermuda. On the way there you might want to look at the report from buoy 44402 136 nm SE of Fire Island, N.Y. Some buoys carry a Deep-ocean Assessment and Reporting of Tsunamis (DART) payload and primarily report changes in ocean height that might signal the passage of a tsunami wave. Accessing this type of buoy will also allow a quick check on observations from nearby stations and ships.

Buoy data via e-mail
While a fast Internet connection is by far the easiest way to access the marine navigation information that has been assembled by NOAA, all of the shore station and buoy information can be obtained via e-mail. A text format report for one or more stations can be accessed using www.ndbc.noaa.gov/email_access.shtml. To obtain a report, address your e-mail message to: ftpmail@ftpmail.nws.noaa.gov. The subject line can contain whatever you wish since it will be ignored by the system. The body of the e-mail must be constructed as shown on the Web site (example above). Expect to receive a response to the inquiry in less than two minutes. (Be sure your spam filter does not reject the return e-mail messages).

Data from buoys and land sites can also be obtained by telephone/cell phone by calling 1-888-701-8992, entering “1” followed by the five-digit buoy or station identification number (enter “7” for Q and “9” for Z). A computer-generated voice will deliver the full report from the station including detailed wave information where appropriate. Entering “2” at the end of the report will then provide the most recent complete marine weather forecast. The increasing popularity of satellite telephones (especially the hand-held Iridium phone) makes it entirely practical for a mariner crossing an ocean to obtain weather information and forecasts from buoys along the planned route and from shore stations when nearing the destination. During our test of the system we listened to reports from buoys in the Mediterranean, off the coast of England and in the Pacific. (Some of the water column height buoys do not report through the telephone access system).

A relatively new capability, the measurement of surface currents using high frequency land-based radar, has been added to the list of marine weather related resources. Ocean surface current information, a critical component of many search and rescue efforts is sensed by the coastal high frequency radar sites, some capable of obtaining information out to about 300 km. Files containing current observations for parts of the U.S. East Coast and much of the West Coast are available online. (At the time this article was being written the surface current at N27.1839, W83.0186 (off the west coast of Florida) was moving at 15 cm/sec (0.291 knots) at 139 degrees). Reports for areas such as the western end of Long Island Sound are displayed as a myriad of current vectors, color-coded to depict the speed of the surface current. Data can be shown in knots or in cm/sec, is logged hourly and is displayed for the past 25 hours.



Breadth and scope
The breadth and scope of NOAA’s NWS accomplishments can be overwhelming when you first start delving into NWS’s weather products. Probably the best way to become familiar with the information available is with a high speed Internet connection, a comfortable chair, a glass of your favorite beverage and a few hours to spend poking about in what you will soon agree is a remarkable and immensely valuable information resource. Take the time to look at every one of the subheadings listed in the left panel of the opening page of the nws.noaa.gov Web site. While you are looking at the information you might recall that a few years ago a member of the Senate introduced a bill that would curtail NOAA’s online availability. NOAA and the NWS needs the support of every citizen during the annual budget battles, especially all of us who sail or fly. If you like what you see, tell your Senator and Representative.



Contrbuting editor Chuck Husck is a sailor, pilot, and engineer in Florida.

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