These broadcasts ultimately serve as not only great information, but a way to decongestion frequencies for critical information
Receiving Automated Broadcast Services:
The most common method to receive automated broadcast services is through the aircraft's radios
Frequencies, posted in the chart supplement as well as airport diagrams and approach plates provide the frequency to receive the broadcast
Additionally, phone numbers found in the chart supplement or the local Fixed-Base Operator (FBO) may be used before engine start-up
Automatic Terminal Information Service (ATIS):
ATIS is the continuous broadcast of recorded non-control information in selected high activity terminal areas in order to improve controller effectiveness and to relieve frequency congestion by automating the repetitive transmission of essential but routine information
The information is continuously broadcast over a discrete VHF radio frequency or the voice portion of a local NAVAID as a product of Air Traffic Control
Some airports broadcast two streams, an arrival and departure ATIS:
Arrival ATIS transmissions on a discrete VHF radio frequency are engineered according to the individual facility requirements, which would normally be a protected service volume of 20 NM to 60 NM from the ATIS site and a maximum altitude of 25,000' AGL
In the case of a departure ATIS, the protected service volume cannot exceed 5 NM and 100' AGL
At most locations, ATIS signals may be received on the surface of the airport, but local conditions may limit the maximum ATIS reception distance and/or altitude
Pilots are urged to cooperate in the ATIS program as it relieves frequency congestion on approach control, ground control, and local control frequencies
The Chart Supplement U.S. indicates airports for which ATIS is provided
Present weather consisting of: sky condition, temperature, dew point, altimeter, a density altitude advisory when appropriate, and other pertinent remarks included in the official weather observation
Instrument runway in use
The ceiling/sky condition, visibility, and obstructions to vision may be omitted from the ATIS broadcast if the ceiling is above 5,000' and the visibility is more than 5 miles
The departure runway will only be given if different from the landing runway except at locations having a separate ATIS for departure
The broadcast may include the appropriate frequency and instructions for VFR arrivals to make initial contact with approach control
Pilots of aircraft arriving or departing the terminal area can receive the continuous ATIS broadcast at times when cockpit duties are least pressing and listen to as many repeats as desired
ATIS broadcast must be updated upon the receipt of any official hourly and special weather
A new recording will also be made when there is a change in other pertinent data such as runway change, instrument approach in use, etc.
Example: "Dulles International information Sierra. 1300 zulu weather. Measured ceiling three thousand overcast. Visibility three, smoke. Temperature six eight. Wind three five zero at eight. Altimeter two niner niner two. ILS runway one right approach in use. Landing runway one right and left. Departure runway three zero. Armel VORTAC out of service. Advise you have Sierra"
Pilots should listen to ATIS broadcasts whenever ATIS is in operation
Pilots should notify controllers on initial contact that they have received the ATIS broadcast by repeating the alphabetical code word appended to the broadcast
Example: "Danbury Tower, Cessna One Seven Two Seven Victor, 10 miles to the west, Information Sierra, inbound for landing"
When a pilot acknowledges receipt of the ATIS broadcast, controllers may omit those items contained in the broadcast if they are current
Rapidly changing conditions will be issued by ATC and the ATIS will contain words as follows:
Example: "Latest ceiling/visibility/altimeter/wind/(other conditions) will be issued by approach control/tower"
NOTE-The absence of a sky condition or ceiling and/or visibility on ATIS indicates a sky condition or ceiling of 5,000' or above and visibility of 5 miles or more
A remark may be made on the broadcast, "the weather is better than 5000 and 5," or the existing weather may be broadcast
Controllers will issue pertinent information to pilots who do not acknowledge receipt of a broadcast or who acknowledge receipt of a broadcast which is not current
To serve frequency limited aircraft, FSSs are equipped to transmit on the omnirange frequency at most en route VORs used as ATIS voice outlets. Such communication interrupts the ATIS broadcast. Pilots of aircraft equipped to receive on other FSS frequencies are encouraged to do so in order that these override transmissions may be kept to an absolute minimum
While it is a good operating practice for pilots to make use of the ATIS broadcast where it is available, some pilots use the phrase "have numbers" in communications with the control tower. Use of this phrase means that the pilot has received wind, runway, and altimeter information ONLY and the tower does not have to repeat this information. It does not indicate receipt of the ATIS broadcast and should never be used for this purpose
Chart Supplement U.S. Supplement AWOS/ASOS Frequencies
Operations at Uncontrolled Airports With Automated Surface Observing System (ASOS)/Automated Weather Observing System (AWOS):
Many airports are equipped with either ASOS or AWOS [Figure 3]
At most airports with an operating control tower or human observer, the weather will be available via Aviation Routine Weather Report (METAR), special observation format on the Automatic Terminal Information Service (ATIS), or directly transmitted from the controller/observer
At uncontrolled airports that are equipped with ASOS/AWOS with ground-to-air broadcast capability, the one-minute updated airport weather should be available to you within approximately 25 NM of the airport below 10,000 feet
Some part-time towered airports may also broadcast the automated weather on their ATIS frequency during the hours the tower is closed
Controllers issue SVFR or IFR clearances based on pilot request, known traffic and reported weather, i.e., METAR/Nonroutine (Special) Aviation Weather Report (SPECI) observations, when they are available
Pilots have access to more current weather at uncontrolled ASOS/AWOS airports than do the controllers who may be located several miles away
Controllers will rely on the pilot to determine the current airport weather from the ASOS/AWOS
All aircraft arriving or departing an ASOS/AWOS equipped uncontrolled airport should monitor the airport weather frequency to ascertain the status of the airspace
Pilots in Class E airspace must be alert for changing weather conditions which may effect the status of the airspace from IFR/VFR
If ATC service is required for IFR/SVFR approach/departure or requested for VFR service, the pilot should advise the controller that he/she has received the one-minute weather and state his/her intentions
Pilot: "I have the [Airport] one-minute weather, request an ILS Runway 14 approach
Automated Surface Observing System (ASOS)/Automated Weather Observing System (AWOS):
The ASOS/AWOS is the primary surface weather observing system of the U.S.
The program to install and operate these systems throughout the U.S. is a joint effort of the NWS, the FAA and the Department of Defense
ASOS/AWOS is designed to support aviation operations and weather forecast activities
The ASOS/AWOS will provide continuous minute-by-minute observations and perform the basic observing functions necessary to generate an aviation routine weather report (METAR) and other aviation weather information
The information may be transmitted over a discrete VHF radio frequency or the voice portion of a local NAVAID
ASOS/AWOS transmissions on a discrete VHF radio frequency are engineered to be receivable to a maximum of 25 NM from the ASOS/AWOS site and a maximum altitude of 10,000' AGL
At many locations, ASOS/AWOS signals may be received on the surface of the airport, but local conditions may limit the maximum reception distance and/or altitude
While the automated system and the human may differ in their methods of data collection and interpretation, both produce an observation quite similar in form and content
For the "objective" elements such as pressure, ambient temperature, dew point temperature, wind, and precipitation accumulation, both the automated system and the observer use a fixed location and time-averaging technique
The quantitative differences between the observer and the automated observation of these elements are negligible
For the "subjective" elements, however, observers use a fixed time, spatial averaging technique to describe the visual elements (sky condition, visibility and present weather), while the automated systems use a fixed location, time averaging technique
Although this is a fundamental change, the manual and automated techniques yield remarkably similar results within the limits of their respective capabilities
System Description
The ASOS/AWOS at each airport location consists of four main components:
Individual weather sensors
Data collection units
Processing units
Peripherals and displays
The ASOS/AWOS sensors perform the basic function of data acquisition. They continuously sample and measure the ambient environment, derive raw sensor data and make them available to the collection and processing units
Every ASOS/AWOS will contain the following basic set of sensors:
Cloud height indicator (one or possibly three)
Visibility sensor (one or possibly three)
Precipitation identification sensor
Freezing rain sensor (at select sites)
Pressure sensors (two sensors at small airports; three sensors at large airports)
Ambient temperature/Dew point temperature sensor
Anemometer (wind direction and speed sensor)
Rainfall accumulation sensor
Automated Lightning Detection and Reporting System (ALDARS) (excluding Alaska and Pacific Island sites)
The ASOS/AWOS data outlets include:
Those necessary for on-site airport users
National communications networks
Computer-generated voice (available through FAA radio broadcast to pilots, and dial-in telephone line)
Wind direction is reported relative to magnetic north in ATIS as well as ASOS and AWOS radio (voice) broadcasts
An ASOS/AWOS report without human intervention will contain only that weather data capable of being reported automatically. The modifier for this METAR report is "AUTO." When an observer augments or backs-up an ASOS/AWOS site, the "AUTO" modifier disappears
There are two types of automated stations, AO1 for automated weather reporting stations without a precipitation discriminator, and AO2 for automated stations with a precipitation discriminator. As appropriate, "AO1" and "AO2" must appear in remarks. (A precipitation discriminator can determine the difference between liquid and frozen/freezing precipitation) [Figure 2/3]
ASOS/AWOS Decoder, Page 1
ASOS/AWOS Decoder, Page 2
Automated Weather Observing System (AWOS):
Weather Forecaster Augmentation (KWRI)
Automated Weather Observing Systems consist of various sensors, a processor, a computer-generated voice subsystem, and a transmitter to broadcast local, minute-by-minute weather data directly to the pilot
AWOS observations derived from an automated system will include the prefix "AUTO"
AWOS observations derived from an observer (rare) will include the prefix "OBSERVER WEATHER" [Figure 4]
Observers provide weather and obstruction to vision information in the remarks of the report when the reported visibility is less than 7 miles
These sites, along with the hours of augmentation, are to be published in the Chart Supplement U.S.
The AWOS report density altitude when it exceeds the field elevation by more than 1,000'
The reported visibility is derived from a sensor near the touchdown of the primary instrument runway
The visibility sensor output is converted to a visibility value using a 10-minute harmonic average
The reported sky condition/ceiling is derived from the ceilometer located next to the visibility sensor
The AWOS algorithm integrates the last 30 minutes of ceilometer data to derive cloud layers and heights
This output may also differ from the observer sky condition in that the AWOS is totally dependent upon the cloud advection over the sensor site
These real-time systems are operationally classified into nine basic levels [Figure 5]
AWOS Classifications
The information is transmitted over a discrete VHF radio frequency or the voice portion of a local NAVAID. AWOS transmissions on a discrete VHF radio frequency are engineered to be receivable to a maximum of 25 NM from the AWOS site and a maximum altitude of 10,000 feet AGL. At many locations, AWOS signals may be received on the surface of the airport, but local conditions may limit the maximum AWOS reception distance and/or altitude. The system transmits a 20 to 30 second weather message updated each minute. Pilots should monitor the designated frequency for the automated weather broadcast. A description of the broadcast is contained in subparagraph c. There is no two-way communication capability. Most AWOS sites also have a dial-up capability so that the minute-by-minute weather messages can be accessed via telephone
AWOS information (system level, frequency, phone number, etc.) concerning specific locations is published, as the systems become operational, in the Chart Supplement U.S., and where applicable, on published Instrument Approach Procedures. Selected individual systems may be incorporated into nationwide data collection and dissemination networks in the future
Computer-generated voice is used in AWOS to automate the broadcast of the minute-by-minute weather observations. In addition, some systems are configured to permit the addition of an operator-generated voice message; e.g., weather remarks following the automated parameters. The phraseology used generally follows that used for other weather broadcasts. Following are explanations and examples of the exceptions
Location and Time:
The location/name and the phrase "AUTOMATED WEATHER OBSERVATION," followed by the time are announced
If the airport's specific location is included in the airport's name, the airport's name is announced
Example: "Bremerton National Airport automated weather observation, one four five six zulu"
Example: "Ravenswood Jackson County Airport automated weather observation, one four five six zulu"
If the airport's specific location is not included in the airport's name, the location is announced followed by the airport's name
Example: "Sault Ste. Marie, Chippewa County International Airport automated weather observation"
Example: "Sandusky, Cowley Field automated weather observation"
The word "TEST" is added following "OBSERVATION" when the system is not in commissioned status
"Bremerton National Airport automated weather observation test, one four five six zulu"
The phrase "TEMPORARILY INOPERATIVE" is added when the system is inoperative
"Bremerton National Airport automated weather observing system temporarily inoperative"
Visibility:
The lowest reportable visibility value in AWOS is "less than 1/4." It is announced as "VISIBILITY LESS THAN ONE QUARTER"
A sensor for determining visibility is not included in some AWOS. In these systems, visibility is not announced. "VISIBILITY MISSING" is announced only if the system is configured with a visibility sensor and visibility information is not available
Weather:
In the future, some AWOSs are to be configured to determine the occurrence of precipitation. However, the type and intensity may not always be determined. In these systems, the word "PRECIPITATION" will be announced if precipitation is occurring, but the type and intensity are not determined
Ceiling and Sky Cover:
Ceiling is announced as either "CEILING" or "INDEFINITE CEILING." With the exception of indefinite ceilings, all automated ceiling heights are measured
"Bremerton National Airport automated weather observation, one four five six zulu. Ceiling two thousand overcast"
"Bremerton National Airport automated weather observation, one four five six zulu. Indefinite ceiling two hundred, sky obscured"
The word "Clear" is not used in AWOS due to limitations in the height ranges of the sensors. No clouds detected is announced as "NO CLOUDS BELOW XXX" or, in newer systems as "CLEAR BELOW XXX" (where XXX is the range limit of the sensor)
"No clouds below one two thousand"
"Clear below one two thousand"
A sensor for determining ceiling and sky cover is not included in some AWOS. In these systems, ceiling and sky cover are not announced. "SKY CONDITION MISSING" is announced only if the system is configured with a ceilometer and the ceiling and sky cover information is not available
Remarks:
If remarks are included in the observation, the word "REMARKS" is announced following the altimeter setting
Automated "Remarks"
Density Altitude
Variable Visibility
Variable Wind Direction
Manual Input Remarks. Manual input remarks are prefaced with the phrase "OBSERVER WEATHER." As a general rule the manual remarks are limited to:
Type and intensity of precipitation
Thunderstorms and direction; and
Obstructions to vision when the visibility is 3 miles or less
"Remarks ... density altitude, two thousand five hundred ... visibility variable between one and two ... wind direction variable between two four zero and three one zero ...observed weather ... thunderstorm moderate rain showers and fog ... thunderstorm overhead"
If an automated parameter is "missing" and no manual input for that parameter is available, the parameter is announced as "MISSING." For example, a report with the dew point "missing" and no manual input available, would be announced as follows:
"Ceiling one thousand overcast ... visibility three ... precipitation ... temperature three zero, dew point missing ... wind calm ... altimeter three zero zero one"
"REMARKS" are announced in the following order of priority:
Automated "REMARKS"
Density Altitude
Variable Visibility
Variable Wind Direction
Manual Input "REMARKS"
Sky Condition
Visibility
Weather and Obstructions to Vision
Temperature
Dew Point
Wind; and
Altimeter Setting
"Remarks ... density altitude, two thousand five hundred ... visibility variable between one and two ... wind direction variable between two four zero and three one zero ... observer ceiling estimated two thousand broken ... observer temperature two, dew point minus five"
Automated Surface Observation System (ASOS)Automated Weather Observation System (AWOS)
Manual Observations:
With only a few exceptions, these reports are from airport locations staffed by FAA who manually observe, perform calculations, and enter these observations into the (WMSCR) communication system
The format and coding of these observations are the same as those contained in Aviation Routine Weather Reports (METARs) and Aerodrome Forecasts (TAF)
Service Standards:
The term "Service Standards" refers to the level of detail in weather observation. The service standards consist of four different levels of service (A, B, C, and D) as described below [Figure 8]
Service Level D:
Level D defines the minimum acceptable level of service
It is a completely automated service in which the ASOS/AWOS observation will constitute the entire observation, i.e., no additional weather information is added by a human observer
Information recorded include: wind, visibility, precipitation/obstruction to vision, cloud height, sky cover, temperature, dew point, and altimeter
Service Level C:
Level C is a service in which the human observer, usually an air traffic controller, augments or adds information to the automated observation
Service Level C also includes backup of ASOS/AWOS elements in the event of an ASOS/AWOS malfunction or an unrepresentative ASOS/AWOS report
In backup, the human observer inserts the correct or missing value for the automated ASOS/AWOS elements
This service is provided by air traffic controllers under the Limited Aviation Weather Reporting Station (LAWRS) process, FSS and NWS observers, and, at selected sites, Non-Federal Observation Program observers
Two categories of airports require detail beyond Service Level C in order to enhance air traffic control efficiency and increase system capacity
Services at these airports are typically provided by contract weather observers, NWS observers, and, at some locations, FSS observers
Additional information recorded include: thunderstorms, tornadoes, hail, virga, volcanic ash, tower visibility, and operational significant remarks as deemed appropriate by the observer
Service Level B:
Level B is a service in which weather observations consist of all elements provided under Service Level C, plus augmentation of additional data beyond the capability of the ASOS/AWOS
This category of airports includes smaller hubs or special airports in other ways that have worse than average bad weather operations for thunderstorms and/or freezing/frozen precipitation, and/or that are remote airports
Additional information recorded include: Longline RVR at precedented sites (may be instantaneous readout), Freezing drizzle versus freezing rain, Ice pellets, Snow depth & snow increasing rapidly remarks, Thunderstorm and lightning location remarks, Observed significant weather not at the station remarks
Service Level A:
The highest and most demanding category, includes all the data reported in Service Standard B, plus additional requirements as specified
Service Level A covers major aviation hubs and/or high volume traffic airports with average or worse weather
Additional information recorded include: 10 minute Longline RVR at precedented sites or additional visibility increments of 1/8, 1/16 and 0 Sector visibility, Variable sky condition, Cloud layers above 12,000 feet and cloud types, Widespread dust, sand and other obscurations, Volcanic eruptions
Service Levels
Automatic Flight Information Service (AFIS) - Alaska FSSs Only:
AFIS is the continuous broadcast of recorded non-control information at airports in Alaska where an FSS provides local airport advisory service. Its purpose is to improve FSS specialist efficiency by reducing frequency congestion on the local airport advisory frequency
The AFIS broadcast will automate the repetitive transmission of essential but routine information (for example, weather, favored runway, braking action, airport NOTAMs, etc.). The information is continuously broadcast over a discrete VHF radio frequency (usually the ASOS frequency)
Use of AFIS is not mandatory, but pilots who choose to utilize two-way radio communications with the FSS are urged to listen to AFIS, as it relieves frequency congestion on the local airport advisory frequency. AFIS broadcasts are updated upon receipt of any official hourly and special weather, and changes in other pertinent data
When a pilot acknowledges receipt of the AFIS broadcast, FSS specialists may omit those items contained in the broadcast if they are current. When rapidly changing conditions exist, the latest ceiling, visibility, altimeter, wind or other conditions may be omitted from the AFIS and will be issued by the FSS specialist on the appropriate radio frequency
"Kotzebue information ALPHA. One six five five zulu. Wind, two one zero at five; visibility two, fog; ceiling one hundred overcast; temperature minus one two, dew point minus one four; altimeter three one zero five. Altimeter in excess of three one zero zero, high pressure altimeter setting procedures are in effect. Favored runway two six. Weather in Kotzebue surface area is below V-F-R minima - an ATC clearance is required. Contact Kotzebue Radio on 123.6 for traffic advisories and advise intentions. Notice to Air Missions, Hotham NDB out of service. Transcribed Weather Broadcast out of service. Advise on initial contact you have ALPHA"
NOTE: The absence of a sky condition or ceiling and/or visibility on Alaska FSS AFIS indicates a sky condition or ceiling of 5,000 feet or above and visibility of 5 miles or more. A remark may be made on the broadcast, "the weather is better than 5000 and 5"
Pilots should listen to Alaska FSSs AFIS broadcasts whenever Alaska FSSs AFIS is in operation
NOTE: Some Alaska FSSs are open part time and/or seasonally
Pilots should notify controllers on initial contact that they have received the Alaska FSSs AFIS broadcast by repeating the phonetic alphabetic letter appended to the broadcast
EXAMPLE: "Information Alpha received"
While it is a good operating practice for pilots to make use of the Alaska FSS AFIS broadcast where it is available, some pilots use the phrase "have numbers" in communications with the FSS. Use of this phrase means that the pilot has received wind, runway, and altimeter information ONLY and the Alaska FSS does not have to repeat this information. It does not indicate receipt of the AFIS broadcast and should never be used for this purpose
Conclusion:
Although still early in development, you can digitally access ATIS (ATIS-D) through apps on android and apple
When listening to an automated broadcast in other countries, multiple languages may be used
An English segment will always be available, however
