Despite all the technological advancements, safety in flight is still subject to weather conditions such as limited visibility, turbulence, and icing.
One may wonder why pilots need more than general information available from the predictions of the meteorologist. The answer is well known to the experienced pilot. Meteorologists’ predictions are based upon movements of large air masses and upon local conditions at points where weather stations are located. Air masses at times are unpredictable, and weather stations in some areas are spaced rather widely apart. Therefore, pilots must understand the conditions that could cause unfavorable weather to occur between the stations, as well as the conditions that may be different from those indicated by weather reports.
Furthermore, the meteorologist can only predict the weather conditions; the pilot must decide whether the particular flight may be hazardous, considering the type of aircraft being flown, equipment used, flying ability, experience, and physical limitations.
Weather service to aviation is a combined effort of the National Weather Service (NWS), the Federal Aviation Administration (FAA), the Department of Defense (DOD), and other aviation groups and individuals. Because of the increasing need for worldwide weather services, foreign weather services also have a vital input into our service.
This chapter is designed to help the pilot acquire a general background of weather knowledge and the principles upon which sound judgment can be built as experience is gained and further study is undertaken. There is no substitute for experience in any flight activity, and this is particularly true if good judgment is to be applied to decisions concerning weather.
Weather observations are measurements and estimates of existing weather both at the surface and aloft. When recorded and transmitted, an observation becomes a report, and these reports are the basis of all weather analyses and forecasts.
Surface Aviation Weather Observations
Surface aviation weather observations include elements pertinent to flying. A network of airport stations provides routine up-to-date surface weather information. Automated surface observing systems (ASOS), automated weather observing systems (AWOS), and other automated weather observing systems are becoming a major part of the surface weather observing network.
Upper Air Observations
Upper air observations are data received from sounding balloons (known as radiosonde observations) and pilot weather reports (PIREPs). Upper air observations are taken twice daily at specified stations. These observations furnish temperature, humidity, pressure, and wind data. In addition, pilots are a vital source of upper air weather observations. In fact, aircraft in flight are the only means of directly observing turbulence, icing, and height of cloud tops.
Precipitation reflects radar signals which are displayed as echoes on the radar scope. The use of radar is particularly helpful in determining the exact location of storm areas. Except for some mountainous terrain, radar coverage is complete over the contiguous 48 states.
A radar remote weather display system (RRWDS) is specifically designed to provide real-time radar weather information from many different radars. A radar system that uses Doppler technology is being installed across the United States. This radar gives greater detail and enhanced information about thunderstorms and weather systems.
A weather service outlet as used here is any facility, either government or private, that provides aviation weather service to users. Information concerning some of the service outlets provided by the FAA follows.
FAA Flight Service Station (FSS)
The FAA flight service station provides more aviation weather briefing services than any other government service outlet. They provide preflight and inflight briefings, make scheduled and unscheduled weather broadcasts, and furnish weather advisories to flights within the FSS area.
The FAA has modernized its FSS program. Automated flight service stations (AFSS) are becoming abundant, with about one per state, with lines of communications radiating out from it.
Pilot’s Automatic Telephone Weather Answering System (PATWAS)
Pilot’s automatic telephone weather answering system is a recorded telephone briefing with the forecast for the local area, usually within a 50 nautical mile radius of the station.
Transcribed Information Briefing Service (TIBS)
Transcribed information briefing service is provided by AFSS’s and provides continuous telephone recordings of meteorological and/or aeronautical information. Specifically, TIBS provides area and/or route briefings, airspace procedures, and special announcements, if applicable. Other items may be included depending on user demand.
Direct User Access Terminal Service (DUATS)
A direct user access terminal service is an FAA-operated information system which enables pilots and other aviation interests to conduct their own weather briefings. The computer-based system receives and stores a number of NWS and FAA products which are commonly used in weather briefings. Pilots using a personal computer and modem can access the system and request weather and other pertinent data as well as file or amend flight plans.
Transcribed Weather Broadcast (TWEB)
A transcribed weather broadcast is a continuous broadcast on low/medium frequencies (190 to 535 kHz) and selected VORs (108.0 to 117.95 MHz).
Obtaining a good weather briefing is in the interest of safety. It is the pilot’s responsibility to ensure all the needed information is obtained to make a safe flight. When requesting a briefing, pilots should identify themselves and provide as much information regarding the proposed flight as possible. The information received will depend on the type of briefing requested. The following would be helpful to the briefer.
• Type of flight, visual flight rule
(VFR) or instrument operating rule (IFR).
• Aircraft number or pilot’s name.
• Aircraft type.
• Departure point.
• Route of flight.
• Flight altitude(s).
• Estimated time of departure.
• Estimated time en route or estimated time of arrival.
Standard Briefing should include:
• Adverse conditions.
• VFR flight not recommended when conditions warrant.
• Weather synopsis (positions and movements of lows, highs, fronts, and other significant causes of weather).
• Current weather.
• Forecast weather (en route and destination).
• Forecast winds/temperatures aloft.
• Alternate routes (if any).
• Notices to Airmen (NOTAMs).
• Air traffic control (ATC) delays.
• Request for PIREPs.
An abbreviated briefing will be provided at the user’s request to supplement mass disseminated data, to update a previous briefing, or to request specific information only.
An outlook briefing will be provided when the briefing is 6 or more hours in advance of the proposed departure time. It will be limited to applicable forecast data for the proposed flight.