A look at the hourly updates provided by ATC.
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Every takeoff and landing is planned with a thorough understanding of the weather conditions. Automatic Terminal Information Service, or ATIS, is the source pilots use to plan their aircraft’s performance. Let’s talk about how the weather is reported at airports.
What is ATIS
The issuance of ATIS weather broadcasts is the responsibility of air traffic controllers. ATIS broadcasts are uniformly made at every airport on a dedicated radio frequency. Controllers have precise guidelines about how to record and what to include in ATIS. Generally, a new ATIS report is required upon receipt of an official weather update which usually occurs 54 minutes past every hour. Each ATIS broadcast has a letter from the phonetic alphabet appended to it, such as “alpha” or “bravo,” so that pilots and controllers can quickly communicate about the weather efficiently.
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Ground controllers are responsible for ensuring that departing aircraft have the current weather information. On initial contact with the ground, pilots will indicate they have the current ATIS by stating its letter. Likewise, approach controllers at large airports ensure arriving pilots have the most recent weather. It’s a courtesy for pilots to inform that they have the updated information without being prompted to save unnecessary chatter on the frequency. When a new ATIS broadcast comes into effect, the ground, tower, and approach controllers state the letter of the new ATIS and the updated altimeter setting so that pilots can promptly set it.
ATIS is reported uniformly. Here’s an example of what a recorded ATIS might sound like:
Airport ATIS information Alpha. Time 17:54 Zulu. Wind two six zero at one six. Visibility one zero. Ceiling one thousand overcast. Temperature one four. Dew point one six. Altimeter two niner niner six. ILS runway two four right approach in use. Departing runway two four left. Notice to air missions: multiple cranes in vicinity of airport. Advise on initial contact you have information Alpha.
ATIS is available digitally at large airports. Pilots can download the ATIS digitally or print it if the plane is equipped correctly. This saves time since pilots don’t have to tune in and listen to the ATIS on its dedicated frequency. Pilots can also receive airport weather from hundreds of miles away rather than waiting until they are in the airport’s ATIS broadcast frequency range.
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Rapidly changing weather requires updates more frequently than the regular hourly ATIS update. A “SPECI” (or special weather observation) is issued on dynamic weather days between regular ATIS updates. A SPECI will be issued if the wind necessitates a runway direction change, if the cloud ceiling is rapidly lowering, or if microbursts or wind shear have been observed. Pilots rely on special observations during rapidly changing conditions to calculate accurate landing and takeoff speeds or to determine if the weather is good enough to attempt an approach and landing.
ATIS broadcasts are an underlying feature of every controlled airport. ATIS allows every pilot to be on the same page, even at a large airport. ATIS is an ingenious yet simple solution to distributing weather information that would otherwise require much more verbosity.