The Rapid Refresh (RAP) model uses a rapid-refresh version of the WRF model. Therefore, the images generated by the NAM/WRF model can be compared with the images of the RAP model. The RAP model covers North America and is updated every hour. The model has a 13 km horizontal resolution with 50 vertical levels. The grid is projected onto a rotated lat-lon grid, with a 759x567 mass-point domain (Arakawa grid). The model uses 1/12-deg NCEP sea-surface temperatures. The web site images are updated every hour.
RAP 4 Panel Forecasts
These 4 panel charts displays the conditions at 4 forecast times for a particular plot type. The upper left panel is the 1 hour forecast, the upper right is the 3 hour forecast, the lower left is the 5 hour forecast and the lower right is the 7 hour forecast.
0 - 3000m Helicity
Helicity is used to indicate where rotation/shear is high enough to allow thunderstorms to organize into severe or supercell storms. In the lack of helicity, storms develop vertically and the precipitation will snuff out the updraft killing the thunderstorm. Severe storms need helicity to maintain an organized structure allowing hte storm to develop to severe limits. A value of 400-500 is often needed to produce severe storms. Often this is used in conjunction with CAPE to determine severe storm location.