The Center Weather Advisory (CWA) is a specialized aviation weather warning used within the United States National Airspace System to manage the safety and flow of air traffic. It serves as a short-fused product that alerts pilots and air traffic controllers to immediate or anticipated hazardous weather conditions. This advisory is part of a broader system of weather alerts, designed to ensure operational safety during all phases of flight.
Defining the Center Weather Advisory and Its Purpose
The CWA is an unscheduled weather product designed to warn of hazardous conditions that are developing rapidly or are not adequately covered by broader national advisories. It is primarily a tactical tool used by the Federal Aviation Administration (FAA) to manage air traffic flow in real-time and by flight crews to avoid immediate dangers. CWAs are short-term, typically valid for a maximum of two hours, and may include forecasts for conditions expected to begin within the next two hours.
The CWA is issued by the National Weather Service (NWS) through its Center Weather Service Units (CWSU). CWSUs are staffed by NWS meteorologists but are physically located within the FAA’s Air Route Traffic Control Centers (ARTCCs), which manage high-altitude, en-route airspace. This co-location allows for immediate coordination between weather experts and the air traffic managers responsible for the airspace. The CWA acts as a localized “nowcast,” providing precise, actionable intelligence that complements the national forecast picture.
Specific Conditions That Trigger a CWA
The issuance of a CWA is prompted by specific meteorological conditions that meet or approach the criteria for more significant national advisories. The primary goal is to provide warnings for hazards that could severely impact the safety or efficiency of flight operations within the ARTCC’s area of responsibility. These advisories are often issued for significant phenomena such as moderate or greater turbulence, or moderate or greater icing.
CWAs are issued for a variety of other conditions, including:
- Widespread or rapidly developing thunderstorms that meet Convective SIGMET criteria.
- Heavy or extreme precipitation, which can dramatically reduce visibility or affect aircraft performance.
- Surface weather events such as dust storms, sandstorms, or volcanic ash.
- Low instrument flight rules (LIFR) conditions, indicating poor visibility and low cloud ceilings.
- Low-level wind shear (a rapid change in wind speed or direction below 2,000 feet above ground level).
- Sustained surface winds or gusts exceeding 30 knots.
CWA Versus Other Aviation Weather Alerts
The CWA operates within a hierarchy of aviation weather warnings, the most common of which are AIRMETs (Airmen’s Meteorological Information) and SIGMETs (Significant Meteorological Information). The fundamental distinction lies in scope, scale, severity, and issuance schedule.
AIRMETs generally cover widespread, moderate hazards like moderate icing or turbulence and are typically issued as scheduled products valid for up to six hours. SIGMETs, by contrast, warn of severe, widespread non-convective hazards, such as severe or extreme turbulence or volcanic ash, and are valid for up to four hours. These alerts cover large geographical areas and are often used for pre-flight planning.
The CWA is a localized and unscheduled product, issued only as needed for a specific ARTCC area. It is not considered a flight-planning tool due to its short lead time and duration. A CWA is often issued when a localized weather hazard is approaching SIGMET criteria but does not yet meet the larger geographical requirements for a national issuance. It acts as an immediate supplement to existing national advisories, allowing the CWSU meteorologist to refine or update the location, movement, or intensity of a weather event.
This highly localized focus makes the CWA an invaluable tactical tool for air traffic controllers. They use this rapid, detailed intelligence to make real-time decisions about traffic flow and re-routing aircraft.