https://phys.org/news/2018-05-nasa-alberto-strongest-storms-fragmented.html

The Moderate Resolution Imaging Spectroradiometer (MODIS) instrument aboard NASA's Aqua satellite captured an infrared image of Tropical Storm Alberto on May 27 at 2:50 a.m. EDT (0650 UTC) which showed scattered strong storms north and east of Alberto's center over the Gulf of Mexico. The most powerful thunderstorms had cloud top temperatures as cold as or colder than -63 degrees Fahrenheit (-53 degrees Celsius).  A small area, located over open waters south of the southern tip of Florida, had the coldest temperatures near -70 degrees Fahrenheit (-56.6 Celsius), indicating the strongest storms within the tropical storm. Storms with cloud top temperatures that cold have the capability to produce heavy rainfall. 

NHC forecaster Cangialosi noted "Alberto appears a little better organized this morning with an area of deep convection gradually expanding near and to the north of the center. A large band of showers and thunderstorms extends well to the east of the center from western Cuba to south Florida and the northwestern Bahamas."