NCEP MMAB Coastal Visual Range Guidance
revised October 26, 2006.PLEASE NOTE: The model upon which these visibiliity products are based was changed on July 8, 2003. The cloud physics packages were improved, which resulted in more realistic modeling of visual range. These changes have resulted in significant pattern changes and reduced the amount of decreased visibilities over land and sea. More information can be found at the mmb website. Comments are encouraged.
The lowest layer Coastal Visual Range Guidance products are provided as post-processed fields direct from the NAM (12 km resolution currently) model. The data used for the lower 48 states are taken from a 40km Lambert Conformal grid and applied to a 0.25 deg X 0.25 deg lon/lat grid over N. America. The data used for Alaska are taken from a 45km polar stereographic grid and applied to a 0.25 deg X 0.25 deg lon/lat grid over Alaska and adjacent water bodies. These fields are in m and have been converted to n mi on the depictions shown on this web page.
These products are valid all year for the coasts of the contiguous United States, Alaska and Gulf of Alaska. Three shades of color are given: 7 n mi to gt 3 n mi in blue, 3 n mi to gt 0.5 n mi in green, and le 0.5 n mi in yellow, where 7 n mi is the furthest distance to the horizon that can be seen from the bridge of most ships, le 3 n mi is where National Weather Service Forecasters are required to add obstructions to visibility to their forecasts, and le 0.5 n mi is the WMO definition of dense fog.
The animations and still figures are in gif format; the animations are on the order of 350k, while the stills are on the order of 15k each. Model output is available throughout the year.
The GRIB filecontain 29 records: one for each projection for AWIPS Grid 212 or Grid 217 from 03 to 84 hours at 3-h intervals on a 45 km polar stereographic grid or a 40 km Lambert Conformal grid, respectively. gif files are also available. There is a link below that will take you to the ftp sites.
Please send questions and comments to Robert.Grumbine@noaa.gov
See "About the NCEP Coastal Visibility Guidance" to find out the differences between the new and old versions of this product.
NAM Visibility Forecast Animations
Table 1. Animation selection table. Each animation has 29 frames with forecasts from 03- through 84-h at 3 hour intervals. The animation has a size of about 350k and takes about 3 minutes to download with a 28.8 K modem.
Individual NAM Visibility Forecasts
Table 2. Individual forecast selection table. Within each depiction column are the numbers 00, 06, 12, and 18; these are the model run times for the projection hour.
Visibility Forecast Data