Is it true that the VAAC’s do not issue volcanic ash dispersion model forecasts (sometimes called “VAFTADs” using the name of an earlier model), but use them as guidance, like the PUFF and AVHRR? If I wanted to see your forecast, then would need to look up your bulletin and the attached VAAC chart along with the SIGMETS bulletin, or do you send the VAFTAD out as a graphic?
Yes, dispersion model output is guidance. For information on obtaining the model output, see From http://www.ready.noaa.gov/ready-bin/ashcurrent.pl
Though there is not an international requirement to issue the model output, NOAA issues it with WMO headers PHBE10 KWBC and PHBI10 KWBC.
SIGMETs contain the official forecast; these are issued by Meteorological Watch Offices such as the Aviation Weather Center. ( http://aviationweather.gov/) and the Alaska Aviation Weather Unit (http://aawu.arh.noaa.gov/). Other official volcanic ash products are Volcanic Ash Advisories (text messages) and Volcanic Ash Graphics, issued from Volcanic Ash Advisory Centers (e.g. Washington (http://www.ssd.noaa.gov/VAAC/messages.html) and Anchorage (http://vaac.arh.noaa.gov/)).”
AVHRR satellite imagery is not a forecast, but an analysis.