Weather systems play an important role in the FAA modernization, as weather information services are critical to improving safety and enhancing the capacity of the NAS. The 2000 Aviation Capacity Enhancement Plan reveals that delays due to adverse weather, a major factor affecting NAS capacity, increased significantly from 1998 to 1999 accounting for 71 percent of system delays greater than 15 minutes.

The deployment of the Integrated Terminal Weather System (ITWS) vastly improves the FAA's ability to monitor and predict aviation-impacting weather. The ITWS will function as a "weather server" at 46 major airports. It will ingest and integrate data from multiple sources (NWS Rapid Update Cycle (RUC II) gridded forecast data, Meteorological Data Collection and Reporting System (MDCRS) aircraft observations, lightning data, WSR-88D (or NEXRAD), Terminal Doppler Weather Radar (TDWR), Low Level Wind Shear Alert System (LLWAS), and Airport Surveillance Radar (ASR-9)), and then generate easy-to-use products for NAS non-meteorologist users. The ITWS wind shear and microburst predictive capability will improve NAS safety. It's accurate forecasts of wind shifts associated with frontal passage across airport runways will enable terminal controllers and traffic managers to more efficiently sequence aircraft in and out of the terminal airspace, thereby mitigating weather-induced reductions on airport acceptance rates that can also affect NAS capacity. Furthermore, ITWS will provide significant and timely information on severe storms that assist controllers and traffic managers in routing aircraft around hazardous weather. In addition to displaying enhanced weather products to terminal personnel, ITWS will provide enhanced terminal weather forecast data to the Center TRACON Automation System (CTAS), improving the performance of the automation systems (or tools) used by terminal controllers for sequencing and spacing arrival aircraft. ITWS situation displays located in the Air Traffic Control System Command Center and Air Route Traffic Control Centers will enhance traffic flow management across the NAS.

The FAA continues to validate emerging user requirements for ITWS data. In addition, it is evaluating communications alternatives to meet currently validated requirements, with sufficient flexibility to meet the needs of new users while accommodating changing requirements of current users.