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The typical coastal
boater monitors the weather by keeping his/her eye on the skies and occasionally
putting his/her ear to the VHF marine forecasts broadcast by NOAA’s
National Weather Service. It’s a useful but imperfect technique.
For instance, how do you handle the classic summer lightning conundrum
that came up in this column recently—a flat, hot summer day perfect
for boating but with a chance of severe thunderstorms developing? Do you
listen to that tedious synthesized voice on VHF all day? Wouldn’t
it be great if you could see significant weather hundreds of miles away—even
gauge its intensity and motion? Well, at this year’s Miami International
Boat Show, no fewer than four brand-new products were announced that promise
to make weather awareness while underway quicker, more visual, and more
specific. They’re each different, but all share the common central
feature of overlaying a chart with nearly real-time animated output from
NOAA’s remarkable nationwide Nexrad weather radar system.
Nexrad, short for Next
Generation Radar, became fully operational during the 1990’s, but
many of us are only just now grasping its capabilities. Picture 158 radar
domes carefully spaced around the country (including Hawaii and Puerto
Rico). Each is 28 feet in diameter and contains a 750-kW scanner capable
of seeing rain and snow—and birds, airplanes, and more—for
a radius extending as far as 250 miles. Their output scans are high-resolution
and color-coded to reveal gradations of intensity. All that output is
piped to central super computers, where it is processed, even blended
into large-area mosaics, and then offered freely to the public (and to
independent weather organizations for use in forecasting and for commercial
redistribution).
So what can Nexrad do
for you? The Web screenshot on page 40 is some indication. It shows first
how Nexrad covers almost the whole country to about 100 miles offshore
and second how it paints a picture of active weather, or at least the
precipitation that accompanies the most significant activity. (You can
bet that’s a significant front moving through the central states.)
Moreover, the picture was scanned just a few minutes before I opened the
Web page and, unlike many satellite images, shows what’s happening
underneath the cloud layers. Better yet (but hard to show on paper) you
can “loop” the image—i.e., see a little movie of the
radars’ scans over the last few hours—which truly helps you
understand often complex system motions. You can make out areas of particularly
intense precipitation by their “hotter” colors and thus identify
fronts and—when more typically zoomed in to a few hundred miles
around your location—even individual storm cells. In looping mode
you can often tell if these cells are intensifying or breaking up and
predict their track.
No doubt you’ve
seen images like this narrated by a TV forecaster or on the Web (go to
www.nws.noaa.gov and select “radar,”
or find somewhat improved versions at independent weather sites like www.wunderground.com).
And I’m sure that some well-equipped boaters use fast onboard Internet
connections to check out Nexrad sites while cruising, even though going
online is generally a hassle on anything but a megayacht. After all, what
better way to bridge the often substantial gap between what you can see
immediately around you and what the forecasters were predicting a few
hours ago for a fairly wide region? So how would you like to have this
almost live weather information simply overlaid on, say, a Northstar 958
chartplotter? Well, that’s exactly what a company called WSI was
showing off in Miami, an impressive system called AtSea.
Next page >
Weather Tracking, Part 2 > Page 1, 2,
3, 4, 5,
6
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