Maximum sustained winds reached only about 40 mph before the storm lost force and weakened to a tropical depression while moving deeper into the Atlantic.
Alberto was the earliest-forming tropical storm in the Atlantic Basin since Ana emerged on April 21, 2003.
Alberto was also one of only three Atlantic tropical storms to form in May over the past 31 years, according to Weather Underground's Jeff Masters.
Tropical Storm Alberto Track
Satellite Loop Data: CIMSS