Ceiling and Visibility
- About
- Contacts
Overview
Low ceilings and reduced surface visibilities yield critical impacts across the spectrum of aviation activities. For the general aviation pilot, limited ceiling and/or visibility (C&V) present a significant safety hazard – one that must be carefully considered in making pre–flight go/no–go decisions, route plans, and in–flight IFR avoidance and escape decisions. For commercial aviation, advanced aircraft equipment and pilot experience enable safe operations in low C&V conditions, but traffic flow capacity at impacted terminals drops markedly. This reduction in capacity is a major cause of flight delays and cancellations, and can propagate 'upstream' from impacted terminals to feeder terminals where no C&V problem exists.
RAL's work toward C&V nowcasting and forecasting addresses both the safety and terminal capacity impacts outlined above.
National Ceiling and Visibility
NCVn Nowcast Product
RAL's first–generation National Ceiling and Visibility Nowcast (NCVn) is undergoing FAA evaluation to qualify for future operational use as a supplemental guidance product enhancing pilot situational awareness. NCVn presents current observations at ˜1600 METAR sites across the continental U.S. (CONUS), along with estimates of expected conditions between observing points based on careful spatial interpolation. To remain current in rapidly changing conditions, the product is updated every 5 minutes, and is rendered on a 5 km grid. NCVn's ceiling, visibility and flight category displays are accompanied by product confidence fields that provide users with simplified information on the quality of observations and seek to aid the users' assessment of product representativeness for current conditions. A second–generation NCVA product will implement more rigorous probabilistic representation of the uncertainty in C&V conditions between observing points.
The product is available on the Experimental ADDS website, and is also used to populate RAL's experimental Helicopter Emergence Medical Services (HEMS) Tool.
NCVF Probabilistic Forecast Product
Recognizing that probabilistic weather forecasts are critical to meeting the air traffic efficiency goals of NextGen, RAL is working toward a probabilistic 1–12 hr C&V forecast product (NCVF). This approach acknowledges the inherent uncertainty in the forecast process and seeks to quantify and convey that uncertainty directly to the user. Forecast probabilities can be intelligently interpreted by human decision–makers, and can be used quantitatively in decision support systems where a variety of inputs and consequences are considered. In mature form, NCVF will forecast the probabilities for ceiling and visibility conditions ranging from fully obscured to clear.
RAL's NCVF development combines existing operational forecast resources through use of new techniques, and typically yields forecast skill that exceeds that of its input resources. For example, blending of LAMP forecast data with time–lagged ensembles derived from the Rapid Update Cycle (RUC) yields the improved IFR ceiling forecast skill shown for the Cincinnati/Northern Kentucky International airport shown in the figure at left. Blended use of the Rapid Refresh model yields the improved IFR visibility forecast skill for Chicago's O'Hare airport shown at right. Under NOAA funding, development is looking at best ways to incorporate forecaster inputs to the NCVF process, and best opportunities to enhance the tools available to operational forecasters today.
Figure: Nine–hour forecast skill for NCVF (in black) and LAMP (in red) for the period November 2009 through April 2010. IFR ceiling for Cincinnati Intl. at left. IFR visibility for Chicago O'Hare at right. NCVF skill in these examples exceeds that of LAMP, the RUC model (blue diamond at left) and Rapid Refresh model (blue diamond at right).
NCVF development will include evaluation of the forecast skill increases attainable through use of time–lagged ensembles from the High Resolution Rapid Refresh and NAM models, as well as use of RAL–developed statistical forecasting methods. Conventional ensembles comprised of members from the NAM and Rapid Refresh will also be evaluated. The first–generation experimental NCVF product will undergo operational trials in the NE U.S. starting November, 2010.
San Francisco Marine Stratus Forecast
RAL staff have worked with colleagues from MIT/ Lincoln Laboratory to develop the San Francisco Marine Stratus Forecaster Display system, which provides forecasts of the time that low clouds and fog will clear the approach to the San Francisco Airport. The system was transferred to the NWS and is currently running operationally.
The San Francisco Marine Stratus Forecaster Display (above) is used operationally by the Center Weather Service Unit (CWSU) forecaster, WFO aviation forecaster, FAA traffic managers, and airline meteorologists. The left side provides displays of sensor data, used in the forecast models. There are four primitive forecast models and a consensus forecast. The right side provides the forecast information. The historical probability of success is provided as a measure of confidence in the consensus forecast.
Primary Contacts
- CARMICHAEL, Bruce | AAP DIRECTOR | ph: 8406 | email: brucec
- BARRON, Bob: | AAP DEPUTY DIRECTOR | ph: 8410 | email: bob
- POLITOVICH, Marcia | AAP DEPUTY DIRECTOR | ph: 8449 | email: marcia