Insights

Your safety depends on it

Meteorology is a science, and while you are not expected to be a meteorologist, you must understand basic meteorology and be able to interpret aviation weather data--a task that became easier with the October 2007 publication of FAA Advisory Circular 00-45F, Aviation Weather Services. Weather data is available from several sources; I recommend TV's The Weather Channel and the FAA's Pilot Web site. It contains all required resources: published notices to airmen (notams) and notam contractions, temporary flight restrictions (TFRs), NOAA's Aviation Digital Data Service (ADDS), NOAA's Aviation Weather Center, and NOAA's National Weather Service. The amount of information can be intimidating, but if you use ADDS and the following outline, the applicability of that information will make sense. When weather is obviously favorable, some steps can be omitted.

• Seven days before your flight: Start monitoring The Weather Channel's weekly planner at 20 minutes past most hours.
• 48 hours before: Check the 48-hour prognostic chart.
• 36 hours before: Check the 36-hour prognostic chart and the day-two convective outlooks (AC)--published twice daily. The AC depicts areas of possible severe thunderstorms and areas of general thunderstorms.
• 24 hours before: Check the terminal aerodrome forecasts (TAFs)--valid for 24 hours, published four times daily--and the day-two AC.
• 18 hours before: Check the TAFs, the area forecasts (FAs)--valid for 18 hours, published three times daily--and the day-one AC, which is published five times daily.
• 12 hours before: Check the TAFs, FAs, 12-hour prognostic chart, and day-one AC.
• As you get closer to flight time, compare the TAFs and FAs to the METARS, which provide the actual weather conditions and are published hourly. This step is critical! If the forecasts are accurate--the actual weather is equal to or better than the forecast weather--continue. If not call flight service for an outlook briefing and ask if an amended forecast has been issued.
• If the forecasts are valid, check for aviation hazards contained in convective sigmets, sigmets, airmets, center weather advisories, and urgent pilot reports. If none exist, check the winds-aloft forecast and plan your flight.
• Six hours before: By this time you know whether or not conditions seem acceptable, so perform the second critical step: Call flight service to get a second opinion of the weather situation. Ask for a standard briefing.

Flight safety can be compromised if you use only flight service for a weather briefing. You should use Internet resources to determine the weather situation, and then use flight service to validate your knowledge. During the briefing, you will readily identify information that supplements or corrects that knowledge. If conditions are acceptable, file your flight plan.

• Before departure: Check the Weather Depiction Chart, published every three hours, and the United States Surface Analysis Chart for your area--published every eight hours, but more legible than the Surface Analysis Chart, which is published every three hours.

If isolated or widely scattered thunderstorms are forecast and you're planning a VFR flight, check the Nexrad radar charts and the Radar Summary Chart--published hourly--to ensure that your planned route is clear of convective activity. Call flight service for an abbreviated briefing; check for last-minute weather changes and new TFRs or pilot reports (pireps).

• Finally, revalidate your weather knowledge during flight by contacting En Route Flight Advisory Service (Flight Watch, 122.0 MHz).

Instrument pilots must carefully evaluate thunderstorms and freezing levels. ATC's WSR-88D Doppler radar displays precipitation and non-precipitation targets, a vast improvement over the old radar systems, but flying with thunderstorms present is foolhardy unless your airplane has airborne radar or your planned route will obviously avoid isolated or widely scattered storms. To determine freezing levels, look at the freezing level graphics forecasts: initial, three-, six-, nine-, and 12-hour. The initial and three-hour forecasts are updated hourly, the others are updated every three hours. Then look for pireps and airmet zulus, which predict freezing level heights and moderate icing. The AOPA Air Safety Foundation offers several free online courses on this topic, including A Pilot's Guide to Flight Service and the Weather Wise series. Your safety requires proper weather knowledge, good judgment, and sound decisions. Use your resources! Ralph Butcher, a retired United Airlines captain, is the chief flight instructor at a California flight school. He has been flying since 1959 and has 25,000 hours in fixed- and rotary-wing aircraft. Visit his Web site.