The following article is based on Lou Billones' April 24, 2006 presentation to the Nebraska Balloon Club.
First, a bit of background. Lou Billones began ballooning in the 1960’s, crewing for NBC founding member Charlie Cook. Charlie did the weather briefings for the Nationals at Indianola, and in those days, he was paid with an extra pilot pack, which he gave to Lou. This was back in the days of staying in the dorms at Simpson College with no air conditioning. Lou soon took over from Charlie, and was paid the handsome sum of $25 for the entire week. Fast forward a few years . . .
Lou built a business, Windsong Services, forecasting weather for aviation events, and providing weather forecasting for balloonists. Gas balloons, that is, transmitting updates to them by cell phone. One day, he got a phone call from some guy he’d never heard of, Steve Fossett, who wanted weather forecasts to fly a balloon from Japan to the US.
Lou thought the guy was nuts and turned him down. Steve was persistent, calling Lou the next day, and offering to pay for Lou's services. And the rest is history. Fast forward to the present . . .
Lou is passing on the torch of Windsong Services to one of his associates, but is still involved in a few projects, including forecasting weather for an around-the-world record attempt by a Turbine Legend, a partial-scale replica of a P51 Mustang, seen at right.
Now, for an explanation of "Circular 91-compliant" weather information sources. Advisory Circular 00-62, Internet Communications of Aviation Weather and NOTAMS, discusses reliability, accessibility and security standards for distribution of aviation weather and Notices To Airmen (NOTAMs) to the public via the internet. Throughout this discussion, sources will be divided into two groups, according to to their ability to meet Circular 91 standards.
Circular 91-compliant sources of weather information are continually reviewed by humans, and updated in real-time as conditions change. Updates must be disseminated by reliable means. In contrast, non-Circular 91-compliant sources are not meteorlogically watched, may not be updated on a timely basis, may be only seasonally available (i.e., during academic calendars), and should not be relied upon for as a sole source of information for flight planning.
The NWS Aviation Weather Center - Aviation Digital Data Service (adds.aviationweather.gov). This site is Circular 91-compliant, and is designed for briefing purposes, allowing you to follow along and see the same information the briefer is working from when calling 1-800-WX-BRIEF. Other Circular 91-compliant sources are DUATS (www.duats.com). Information includes SIGMET/AIRMET, wind forecasts, prognostic weather charts, forecasts and observations. TAF (Terminal Aerodrome Forecasts) are guaranteed that a human forecaster is watching them for accuracy, and if the forecaster feels that conditions are deviating by a prescribed amount from the forecast, an amended TAF is issued. TAFs are valid for 24 hours and are issued four times a day at 0000, 0600, 1200, and 1800Z. Aviation routine weather reports (METARs) observations are made between 45 minutes past the hour and the hour (e.g., between 1045 and 1100), and are reported between 50 minutes past the hour and the hour (e.g., between 1050 and 1100). A non-routine "special" observation report may be issued if siginficant change occurs. However, the kinds of changes, such as 45° wind shift of 10 kts or more, or a change in cloud ceiling of several thousand feet, are of greater interest to IFR fixed-wing aviation than VFR ballooning. However, a SPECI observation can be issued if thunderstorms occur, which certainly would interest balloonists!
"Davis" Weather Stations (see sidebar) are local weather observations set up by private individuals, and are informative of local conditions, but are not Circular 91-compliant. Note one particular point about the Gretna site. Even though there is a lot more information on here than we need or can use, down at the bottom of the page is a map and list of other Davis weather sites around Omaha, as well as a link to a listing of Davis weather stations around the world. If you’re flying in another city, maybe at a rally, this could provide you with some information about the local conditions.
Some other informative, but non-Circular 91 compliant sources include Weather Underground, Air Sports.Net Launch Code, Blastvalve, WX Bug, and LAMPS. LAMPS Bulletins (www.nws.noaa.gov/tdl/lamp/bullform.html, and the experimental GFS model www.nws.noaa.gov/mdl/gfslamp/bullform.html) are results of statistical models producing hourly forecasts for a selected station. The tabular output is easy to read, and could be easily converted into a graphical form. (Some sites may already do so.) This is the forecast model used by weather forecasters. It does not include wind gusts, although during daylight hours, you can assume any forecast wind over 12 knots will include gusts 5-6 knots higher. Once again, LAMP Bulletins are not Circular 91-compliant.
RUC Soundings (rucsoundings.noaa.gov) are serious meteorological information. (Note: they are not Circular 91-compliant.) You need Java installed on your computer to view the graphics. These were not designed with the general public or pilots in mind, but are excellent weather forecasting tools for predicting whether winds will die or not die, levels and thicknesses of cloud cover, the existence of inversions that may cause sound reflection, etc. RUC stands for Rapid Update Cycle, an hourly computational cycle that is good for near-term (less than 12 hour) forecasting. MAPS (Mesoscale Analysis and Prediction System) is a another computational cycle that predicts at greater than 12 hour range.
Both models produce a SkewT-LogP chart, an "energy diagram" in which lines of constant temperature are skewed at a 45° angle. Atmospheric pressure is indicated on the left vertical axis in a logarithmic scale (LogP), while pressure altitude is indicated on the right vertical axis in thousands of feet. A few reference points help to make sense of the chart: 500mb =18,000' while 850mb = 5,000'. The red line is the temperature sounding, depicting the actual lapse rate. The blue line is the dewpoint sounding. The distance between the two lines represents the relative humidity. Where the lines coincide, clouds form (i.e., 100% relative humidity). The lowest point of convergence indicates cloud bases, and where the lines diverge indicates cloud tops. Temperature generally decreases with height (the "standard lapse rate"). Overnight, radiative cooling of the ground can cool the air at the surface, causing the temperature to increase with height, and form an inversion. Inversions generally cause winds to be "capped", with lighter winds below the inversion layer. As the sun heats the ground and the inversion breaks, upper winds mix down to the surface (see illustration below). By clicking on the "Get Text" button, you can produce a table of wind speed/direction and temperature/dew point values by altitude. (Editor’s note: the RUC website includes a link to an article on interpreting the SkewT plot from the February 2004 edition of the NWS newsletter, The Front. This is an excellent reference for pilots.)
Another interesting point to note is the effect of an inversion on reflection of sound waves. Because air density varies with temperature, air density will be different above and below an inversion layer. This density boundary can reflect sound. When flying a balloon just below the inversion layer, sound may be partially reflected off the inversion layer back to the surface, amplifying the burner's noise. Flying above the inversion layer, sound may be reflected back up. This phenomenon should be kept in mind when flying over livestock or noise-sensitive areas.
Finally, Ryan Carlton’s site, Balloonist’s Wind Forecast (www.ryancarlton.com/wind.php), produces an excellent tabular representation of the RUC sounding data. Still not Circular-91 compliant, but a very nice, readable version of the RUC data.
All links to cited weather sources can be found on the NBC Resources page, categorized as to their Circular 91 status. Nebraska Balloon Club wishes to thank Lou Billones for information on weather sources.