Hurricane Maria made landfall in Puerto Rico early on 20 September as a strong category 4 Hurricane, packing maximum sustained winds of 155 mph. The island received significant damage, including the loss of both radars (TSJU and TJUA). Given the vast devastation, WFO Miami was providing service backup for Puerto Rico. Without radar coverage over the island, forecasters needed to rely heavily on other datasets such as satellite imagery from GOES-16. To provide the best/most information possible, a GOES-16 1-min mesoscale sector was available continuously over Puerto Rico. Having this sector was especially important because, from checkout position, the GOES-16 5-min CONUS sector coverage ends halfway across Puerto Rico (Fig 1). Outside of that sector, coverage is 15-min.
Figure 2: 30 September 2017 GOES-16 1-min VIS/IR sandwich image combination. Full res:
On 30 September, a tropical wave interacting with an upper-level trough was producing strong thunderstorms near Puerto Rico. Given the expected heavy rain and already saturated soils, a flash flood watch was issued for the island. During the morning, strong thunderstorms were oriented just south of the island. The appearance of these storms in satellite imagery led to the issuance of a Special Marine Warning per warning text (SOURCE…SATELLITE IMAGERY INDICATED). The 1-min GOES-16 IR/VIS sandwich image combo shows the burst of thunderstorms and warning product.
Figure 2: 30 September 2017 GOES-16 1-min VIS/IR sandwich image combination. Full res: https://satelliteliaisonblog.files.wordpress.com/2017/09/20170920_pr_1min1.gif
-Bill Line, NWS
“The GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing. Users bear all responsibility for inspecting the data prior to use and for the manner in which the data are utilized.”
Satellite Liaison Blog 
