7.8.1. RAP and HRRR

The Rapid Refresh (RAP) model is available in three forms. The RAP HiRes (also called RAP CONUS) model is focused on the continental US. Nevertheless, it provides marine coverage out to about 130 degrees W on the US West Coast and about 60 degrees West along the US East Coast. Much of the Caribbean is also covered as is all of the Gulf of Mexico and Gulf of California. It offers about 8 data points for each degree of coverage.

 

The second RAP model is the RAP Fast (also call RAP NAM). This RAP Fast model covers all of North America, including Alaska, Hawaii, and Central America. A chunk of northern South America is also included in this model. This is a lower spatial resolution model than the RAP HiRes providing 3 data points per degree (compared to 8 data points per degree in the HiRes). For the satellite user, this is important because for the same area, a RAP Fast file will download faster than a RAP HiRes because it contains fewer data points.

 

Both RAP models offer 1 hour temporal resolution model forecasting over an 18 hour time period. Each was constructed to serve the needs of users needing frequently updated short-term forecasts. This means it is most commonly used by aviators and severe weather forecasters. However, these features will benefit any SAGA Explorer user monitoring short-term weather conditions changing at a pace that is faster than the 3 or 6 hour model update frequencies typical of most weather models.

 

The third RAP variant is the Very High Resolution Rapid Refresh (HRRR) model. This is awesome data with a spatial resolution of about 3 km or more than 30 data points per degree. Data is of such a high resolution that it can be used in inland waters such as Chesapeake Bay, Long Island Sound, Puget Sound, San Francisco Bay and others. In Puget Sound, for example, the HRRR model returns 3 to 4 wind barbs where other models display 1 at most. Of course, the trade off for this high spatial resolution is BIG file size. So when using HRRR data, be sure your GRIB boxes are 1 or 2 degrees at most if connecting through a satellite phone. Expand if on cellular or network connections.

 

RAP wind, precipitation, CAPE, lifted index, air temperature, 500 mb and cloud cover GRIBs are available in all models. Pressure data is also available in the HRRR data set. You must choose a Forecast Duration of 03 through 18 hours in order to have access to ANY of the RAP data in the Global Wind category. If you select 03 through 18 for a Forecast Duration AND you want to access the HRRR data, you will be asked to select one or more time periods when you actually pick HRRR from the Global Wind drop down.

 

Selection of RAP Fast, RAP HiRes or HRRR is an either/or proposition. You cannot select more than one model source at a time.