November 1, 1999
Ever since automated weather observations made their debut, pilots have complained about the problems associated with the observations' lack of a human element. ASOS (automated surface observation system) and AWOS (automated weather observation system), for example, use laser beam ceilometers (LBCs) to determine the height of any clouds or cloud layers above the observing stations. The LBC shoots an extremely narrow beam directly upward to make these observations. If there's a 500-foot overcast, then the LBC will faithfully record the cloud height and report it over the ASOS or AWOS frequency (and, in many cases, over a published telephone number, too). That's great when clouds cover, more or less, the entire sky.
But the LBC doesn't distinguish between a lonely fair-weather cumulus cloud and a massive thunderstorm. It only "sees" the sky directly above it. And ASOS technology hasn't developed to the point where thunderstorm activity can be reliably located and reported by today's observation methods. (This technology is now being introduced, however.) So pilots face a problem: How do we know if the cloud-base information from an ASOS or AWOS observation is really indicative of the prevailing weather at or near the site?
That's one of the issues at the heart of anti-ASOS/AWOS sentiments. "You need a human observer at the airport," critics say. "That's the only way we'll know that a huge thunderstorm is just out of range of an automated site's LBC."
Other criticisms center on precipitation observations and measurements, although ASOS equipment does in fact report precipitation type. Some ASOS sensors also report the presence of freezing rain. Even so, it would be nice to have an actual human telling you whether the rain came from a monster microburst or an isolated, passing shower.
None of this is to suggest that we turn back the clock and revert to rolls of yellow newsprint ratcheting out of clattering teletype machines. I'm no Luddite, and besides, automated weather does give us accurate vital information (altimeter settings, wind information, density altitude) at more airports than ever before. The equipment works day and night, and it allows more instrument approaches (with lower descent minimums) at more airports. Moreover, many ASOS and AWOS sites do have observers who augment automated reports with their own observations. Reports from these sites won't have the AUTO or AO prefixes at the beginning; any human observations that back up or augment any automated information will appear in the "remarks" section of a METAR.
That said, let's agree that more weather information is always better. A program now being used in Alaska goes today's automated weather one better by posting imagery from airport cameras on the Internet ( www.flightcam.net). This program is supported by the Alaska Science and Technology Foundation (funded with the help of the FAA and regional airlines) and now serves three airports in the Alaskan interior — Anaktuvuk Pass, Ruby, and Kaltag.
These airports don't have instrument approaches and are near high terrain and mountain passes. Weather changes quickly in these remote areas, and Ruby and Kaltag don't even have AWOS equipment. Before flightcams, pilots had to fly to these villages not knowing what to expect. Sure, other pilots could relay their own observations, but how reliable would those be after a few hours had gone by?
The flightcam imagery is updated every 30 minutes. Views are shown for various directions from the camera sites. Actually, there are two views for each camera angle. One shows the nearby scenery on a severe-clear, VFR day, and includes terrain features labeled with their heights and ranges. The one next to it shows the current conditions. By comparing the two images, you can see (or not see, as the case may be) just how bad the weather is. Flightcams lend truth to the sayings "What you don't see can definitely hurt you" and "A picture's worth a thousand words."
Alaska's flightcam project began with a $61,000 grant to Army Lt. Col. James Buckingham. More support came from the FAA, the National Weather Service, the Alaska Aviation Safety Foundation, Mosquitonet (an Internet service provider), GCI (a long-distance carrier), the Alaska Department of Transportation, and Alaskan charter firms such as Frontier Flying Service, Tanana Air Service, Larry's Flying Service, and others.
The program began in April. Buckingham would like to continue the flightcam project past its six-month initial period. "I am going to try to continue the service until the FAA can take over the sites later this year ," he said.
"This project has been strongly embraced by the local flying community," Buckingham added. "Air carriers in particular are ecstatic. They trust AWOS for everything but ceiling and visibility. Therefore the cameras fill a much-needed gap in information, especially with the demise of the AFSSs around the state."
Plans are to expand the program to include cameras at the Dillingham, Haines, and Summit airports. Pilot support will help preserve, sustain, and expand the Alaskan flightcam network. To register your support, contact Buckingham via e-mail ( [email protected]).
As long as we're on the subject of Web weather, let me steer you to a couple of sites that deal exclusively with hurricanes. The Tropical Prediction Center ( www.nhc.noaa.gov) of the National Center for Environmental Prediction (NCEP) is the nation's official source of hurricane information. At this site, you can see tracking charts, read about hurricane histories, and get the latest stats on tropical depression, tropical storm, or hurricane developments. I just finished viewing an update on Hurricane Floyd — and wish I hadn't.
Another good hurricane site is run by the Fifty-Third Hurricane Hunters Squadron ( www.hurricanehunters.com). Go there, and you can download five-second movies of actual storm penetrations, including views of torrential rain pelting a P-3 Orion's windshield and propellers. Some nice on-top shots are also there, and the sound of all that rain is sort of neat, and scary. Hurricane season has just ended, so until next June these sites may be your last chance to vicariously fly along on a hurricane-penetration mission.
Icing season is upon us, and the next Wx Watch will deal with some of the many aspects of this serious weather hazard. In the meantime, check out the NWS's experimental "neural network" icing forecast products, put out by the Aviation Weather Center ( http://adds.aviationweather.gov/icing/). Here you can see areas of probable icing, contoured according to altitude and extent of coverage. Altitude ranges run in four groupings: from the surface to 6,000 feet msl; from 6,000 to 14,000 feet msl; from 14,000 feet msl to FL300; and a category called "all levels."
This is just one of many icing-related Web sites, and we'll touch on some others next month. In the meantime, remember that the neural network icing forecasts are experimental, meaning not legal (yet) for weather-briefing purposes. They, like the experimental icing sites posted by other organizations, remain purely advisory, and are works very much still in progress.
Links to all Web sites referenced in this issue can be found on AOPA Online ( www.aopa.org/pilot/links/links9911.shtml). E-mail the author at [email protected].
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