All three players were part of England's training group earlier this month.
Both Shrubsole and George were forced out of England's tour of New Zealand earlier this year due to injuries, but have successfully recovered in time for the English summer.
England skipper Knight expressed her excitement at being able to turn out for Storm in this year's competition.
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“Because of my links to the South West I love playing for Western Storm. We had tremendous success in the Kia Super League and I’m excited that we will get to play a part in this season’s Rachael Heyhoe-Flint Trophy. To be able to play in a competition that bears her name will be an honour.”
“We are linking back up with the squad this week and are really looking forward to seeing how much the group has developed over the winter. It’s a great set up and the three of us can’t wait to play in the green and black again this summer.”
Regional Director of Women's Cricket, Lisa Pagett heaped praise on the England trio saying they add great value to the side not just on the field, but off it as well.
“They have achieved so much in the game already but their desire to keep improving everyday is evident for everyone to see whenever they arrive at training. Although they will initially only be available for three fixtures, their presence will be of huge benefit to the squad as a whole.
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“Once again, we would like to thank the ECB for allowing the player’s release for the opening fixtures of the Rachael Heyhoe Flint Trophy.”
Storm's roster has plenty of familiar faces with the likes of Luff, Fi Morris, Georgia Hennessy, Alex Griffiths, Nat Wraith and Dani Gibson all being handed professional contracts last December. Veteran off-spinner Claire Nicholas, who is pregnant, will miss the start of the competition.
Squad: Sophie Luff (c), Lauren Parfitt, Heather Knight, Alex Griffiths, Georgia Hennessy, Emma Corney, Niamh Holland, Olivia Churcher, Abbie Whybrow, Nat Wraith, Danielle Gibson, Anya Shrubsole, Fi Morris, Katie George, Emily Edgcombe, Steph Hutchins, Lauren Filler