Whitcomb made a career-high-tying six 3-pointers as Seattle was 18 of 30 from 3-point range. Whitcomb was two points away from tying her career high in points.
Sue Bird had nine points and seven assists in her return for Seattle (8-1) after missing the past five games due to a bone bruise in her left knee. Alysha Clark added 16 points and Breanna Stewart had seven points and nine rebounds in 24 minutes.
The Storm reached 100 points for the first time since July 31, 2018.
Betnijah Laney scored 17 points and Blake Dietrick added 16 points for Atlanta (2-7), which has lost six straight games. Atlanta, which will be without star rookie Chennedy Carter for the next two weeks while she recovers from a sprained ankle, was 8 of 29 behind the arc.