In addition to standard briefings, Flight Service Stations offer outlook briefings for pilots who want a picture of what the weather is expected to be more than six hours in the future. Such a briefing might help you to decide the night before whether you will be able to make a flight the next morning. No matter how good the weather looked when you received an outlook briefing, always get a standard briefing before taking off; the weather can change dramatically over the course of six or more hours.
If your takeoff is delayed after you receive a standard briefing, or if you've obtained all of the information that's in a standard briefing from another source, you can get a last-minute update with an abbreviated briefing. As with an outlook briefing, though, don't use this as your only weather source.
The National Weather Service's Aviation Weather Center (AWC) in Kansas City, Missouri, offers a good guide to a standard weather briefing on its Web site ( www.awc-KC.NOAA.gov/awc/aviation_weather_center.html ).
To meet the requirements of the federal aviation regulations (FARs), pilots need to obtain information from one of the official Weather Service dissemination systems. The easiest way to do this is to call a flight service station at 800/WX-BRIEF or get a DUATS briefing using your computer. If you're obtaining a briefing over the telephone and Web access is handy, the Aviation Weather Center Web site is a good way to look at the relevant radar and satellites images as you talk with the briefer. The maps can help you visualize what the weather briefer is talking about.
The Web page also offers a good way for student pilots to practice obtaining weather briefings. In fact, the many links to other information on the AWC's standard briefing page can answer your questions about the nuts and bolts of the various kinds of weather information that pilots should understand.
A standard briefing begins with reports of adverse conditions. The idea is that these reports can make it obvious that a particular flight isn't a good idea, saving pilots time.
The products that give adverse conditions are:
- Sigmets (significant meteorological information): Warnings of conditions that are dangerous to any aircraft.
- Convective sigmets: Warnings of conditions that are dangerous to any aircraft and are caused by convective activity (thunderstorms).
- Airmets (airmen's meteorological information): Warnings of conditions that are particularly dangerous to small, single-engine aircraft.
Sigmets and airmets, like almost all National Weather Service products, are in a kind of shorthand that's unique to the world of weather. While many pilots would like to see these coded reports go away, AWC officials say that's unlikely to happen anytime soon. Fortunately, the Aviation Weather Center and other organizations are helping make sense of forecasts like the typical convective sigmet shown in Figure 1.
Translation problems begin with the fact that locations are given in relation to VOR radio navigation stations. The easiest way to see what area the sigmet refers to is to go to the graphics section on the AWC site that shows areas covered by sigmets and airmets. Figure 2 is an example of these graphics. It shows, in red, the area covered by the first part of convective sigmet 27C. Some commercially available flight-planning software packages do this for you based on a downloaded briefing.
To translate the text, you can first go to the AWC Web site ( www.awc-kc.noaa.gov/awc/aviation_weather_center.html ) to look up the VORs used in the sigmets. The first part translates as: "From 40 (miles) east-northeast of Ardmore (Oklahoma) to 20 (miles) south-southwest of Waco (Texas) to Ardmore to 40 (miles) east-northeast of Ardmore an area of embedded thunderstorms (is) moving little. Tops to flight level 380 (38,000 feet). Cells (are) moving (toward) 200 degrees at 30 knots."
The green lines in Figure 2 show the area covered by the sigmet's outlook section. This section translates as: "Outlook valid (from) 22 (day of the month) at 1555 (Zulu time) to 1955 (on the 22nd). From Hill City (Kansas) to Springfield (Missouri) to 120 miles west-southwest of Grand Isle (Louisiana) to Palacios (Texas) to Texico (Texas) to Hill City. (An) upper-level shortwave trough (is) moving north-northeast into western Kansas. Gulf moisture and (a) marginally unstable air mass across (the) southern (and) central Plains will result in numerous showers with widely scattered, embedded thunderstorms. Thunderstorms could be more numerous across central (and) eastern Texas and western Louisiana by early afternoon where instability will be greater. Occasional convective sigmet issuances expected."
For help in translating coded products you can go to the list of frequently used contractions on the AWC site ( www.awc-kc.noaa.gov/info/domestic_contractions.html ).
From time to time you might see a contraction that you won't find in this list, but you can usually figure out what the report or forecast is saying.
After giving the adverse conditions, the briefer might say that VFR (visual flight rules) flight is not recommended. The decision is up to the pilot. Still, a pilot without much weather experience should give serious thought to not flying if a briefer recommends against it.
If it looks like the flight is still on, the briefer next gives the synopsis of the current weather. This information comes from various charts, including the latest surface weather map, various upper air charts known as constant pressure analysis charts, the radar summary chart, and the weather depiction chart.
The weather depiction chart is a good way to get a quick view of the overall weather that affects flying. Figure 3 is from such a chart and shows Kansas, Oklahoma, most of Texas, and parts of surrounding states. The areas inside the lines have marginal VFR conditions with ceilings from 1,000 feet to 3,000 feet and/or visibility from three to five miles. The shaded areas show instrument conditions with ceilings below 1,000 feet and/or visibility less than three miles.
The circles show weather stations with the amount of shading representing cloud cover. The numbers under the station circles are the ceilings in hundreds of feet. That is, you add two zeros to the end of the figure to read the height of the lowest level of clouds that cover most of the sky.
In a standard briefing, the current conditions information comes after the synopsis. Here, you receive information from aviation routine meteorological reports, or METARs, which are the regular hourly reports from weather stations. On the AWC Web site you can access both the coded METARs and plain-language translations. The AWC Web site also offers various radar and satellite images, which help fill out your picture of the current weather.
After covering the past and current weather, a standard briefing turns to various forecasts for the immediate future.
You can obtain a general picture of future weather from the area forecast for the region where you'll be flying. Area forecasts give the general weather that's expected over a wide area. The contiguous 48 states are divided into six large areas for these forecasts. For a more close-up view, you can look at TWEBs, or transcribed weather en-route broadcasts, for routes between various airports. These forecasts are for a corridor 25 miles on either side of each route.
Before translating the area forecast or TWEB, it's a good idea to look at the low-level significant weather prog chart. ("Prog" is weather talk for "prognosis" or forecast.) These maps show the general forecast for 12 and 24 hours after the time they are issued.
Figure 4 is a four-panel low-level significant weather prog chart. The two charts on the left show the forecast for 12 hours after the map was issued. The top map indicates what should be happening above the surface up to about 25,000 feet, such as turbulence, clouds, and the freezing level. The bottom part shows what should be happening at the surface, including the location of fronts, areas of high and low pressure, and weather such as rain or snow. The two panels on the right are the 24-hour forecasts.
The TAFs, or terminal aerodrome forecasts, give you a picture of what the weather is expected to be at specific airports. In addition to the forecasts and a TAF decoder, the AWC Web site has graphics based on the forecasts.
Figure 5 is an example of one of these graphics, indicating the forecast cloud conditions. The red circles show where ceilings are forecast to be less than 1,000 feet or the visibility less than three miles (IFR conditions). The blue circles indicate ceilings from 1,000 to 3,000 feet or visibility from three to five miles (marginal VFR).
The last forecasts included in a standard briefing are for winds and temperatures aloft. You'll need this information for flight planning. Knowing how fast the wind is blowing, and in what direction, can help you determine the most efficient altitude for your flight. Knowing temperatures aloft can help you avoid icing and other hazards.
A complete weather briefing also includes notices to airmen (notams) for airports you'll be using. The AWC Web site has links to this information.
Each of the FAA's en route Air Route Traffic Control Centers has NWS meteorologists who provide controllers with advisories and impact statements about weather that could affect flights in their areas. Pilots can think of this information as a second opinion about what the weather is likely to do.
The amount of weather information that a pilot is expected to take in and understand can seem overwhelming. But this is true of almost any aspect of flying when you first begin. As with learning how to make smooth landings, learning how to obtain a complete weather briefing and make sound decisions about a planned flight becomes easier with practice. Think of the Aviation Weather Center's Web site as a weather briefing simulator, then practice, practice, practice.
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