The default scan mode (as of the writing of this blog post) for GOES-16 (GOES-East), mode 3, provides a full disk image every 15-min, a CONUS image every 5-min, and two movable 1-min sectors. The GOES-East mesoscale sectors have default locations over the eastern half of the United states, and can be positioned anywhere within the full disk upon request. NWS entities have the highest priority for making requests, and any NWS WFO can make a request through their regional request focal point office.
Figure 1: GOES-East Mesoscale Domain Sector coverage for the afternoon of 3 September 2018. The sector over the northern plains covers a SPC slight risk, while the sector over Florida covers TS Gordon. Full res
When making a meso request, individuals should provide: their office, desired begin and end date/time of sector coverage, the center lat/lon of the sector in decimal degrees, and the rationale for the request. Try to make the request early in the day before the event begins, if possible.
In the event of more than two requests, a priority list is consulted. The priority list can be found in the document or slides at this NOAA VLAB page. When offices make a request, they should refer to this list and make sure they use the highest possible reasoning that applies to their CWA.
When deciding on the center lat/lon of the sector, offices should consider the threat not only within their CWA, but also around them. Instead of simply using a lat/lon in the center of the CWA, requestors should choose a lat/lon that covers their area plus as much of the rest of the threat area as possible. For example, choose a lat/lon that will cover most of the SPC convective outlook area, or SPC fire weather outlook area, or WPC excessive rainfall outlook area, etc. Also, try to keep most of the sector in CONUS in order to benefit as many NWS offices as possible. One can visualize the coverage of a sector given a center lat/lon by consulting this CIRA webpage (Fig 2).
Figure 2: Screenshot from CIRA MDS preview webpage. Full res
Finally, if you think the 1-min imagery will be even remotely helpful in your area, make the request! If there are no requests, the sectors simply scan from their default locations, possibly going unused. National Centers also make requests, but offices should not assume this will happen. For severe threats, SPC will likely make requests for ENH or higher, and often will for SLGT as well. But it is recommended the WFO make the request to ensure coverage, especially for MRGL and SLGT. And remember, once GOES-17 goes operational as GOES-West, there will be four total 1-min mesoscale sectors to work with!
Bill Line, NWS