From NOAA Satellite and Information Service:
What is a "SPENES" message and what does it look like?
The answer lies with the NOAA NESDIS's Satellite Analysis Branch (or SAB), which routinely provides analyses of satellite-derived weather data and trends to the National Weather Service's Weather Prediction Center (WPC) for use in the WPC's Mesoscale Precipitation Discussions (MPDs).
MPDs provides short-term guidance to National Weather Service forecast offices during heavy rain events that may lead to flash flooding. Ideally issued 1-6 hours ahead of time, MPDs consist of a graphic indicating the area of concern and any pertinent meteorological features, as well as a brief text discussion focused on the mesoscale features supporting the anticipated heavy rainfall.
In addition, the SAB provides satellite-based guidance messages, or SPENES, to the NWS Field Offices in Hawaii and Puerto Rico when heavy rains threaten those areas.
So, what does a SPENES message look like? Check out the links below for active messages or view older ones in the archives that date back to 2007.
Active Messages: http://go.usa.gov/cu9ux
Archived Messages: http://go.usa.gov/cu9ze