Western Storm 152 for 1 (Mandhana 70, Priest 72*) beat Yorkshire Diamonds 151 for 9 (Armitage 59) by nine wickets
Western Storm's relentless march towards next month's Kia Super League Finals Day continued with a fifth straight win as openers Smriti Mandhana and Rachel Priest demolished a 152 target to beat Yorkshire Diamonds by nine wickets at York's Clifton Park.
The table-topping Storm initially stymied the Diamonds progress having elected to bowl, with five run-outs coming in the last 16 balls in a total of 151 for 9.
Armitage's innings was then dwarfed in comparison by Indian left-hander Mandhana and New Zealand's Priest, who shared 133 inside 14 overs.
Mandhana hit 70 off 47 balls and wicketkeeper Priest, who also had a hand in all five run-outs, made 72 not out off 43.
It means at the halfway stage in their campaign, the Storm already seem destined for a place at Finals Day at Hove on September 1 having secured a bonus-point victory with 5.1 overs remaining.
Armitage, strong on the sweep, shared a third-wicket stand of 60 inside eight overs with Indian Jemimah Rodrigues, advancing the Diamonds from 47 for 2 in the seventh over.
The diminutive Rodrigues (28) played one particularly memorable lofted cover drive for four off the offspin of compatriot Deepti Sharma.
Storm new-ball duo Claire Nicholas and Freya Davies struck, with Alyssa Healy caught at square leg on the pull off Nicholas' offspin for 12.
Lauren Winfield was stumped by Priest for 18 off seamer Sonia Odedra, with the ball trickling back towards the wicketkeeper off pad.
Davies later bowled Armitage in the 20th over amidst the run out carnage, but England's Anya Shrubsole was clearly the pick of the bowlers with 1 for 16 from four overs: she had Rodrigues caught at mid-off by Mandhana.
Three of the five run-outs came in the 19th over - bowled by Shrubsole - as Yorkshire crucially stumbled. All five runs outs occurred in search of a second run going to wicketkeeper Priest.
Last year, Mandhana was the KSL's leading run-scorer with 421 from nine innings, including two fifties and a hundred. Here, she displayed similar dominance on the way to a 29-ball fifty, achieved in the eighth over when the Storm were 86 without loss.
74 runs came off the powerplay, while opening partner Priest scored only eight of the first 58.
Mandhana was particularly strong over cover and to long-off and, in the fifth over, hoisted legspinner Katie Levick for her only six.
Priest played her part as the partnership approached 100, hitting seamer Alice Davidson-Richards for three successive boundaries to end the sixth.
In 2017, the Kiwi had hit an unbeaten century in a 10-wicket win at this venue. Happy to camp on the back foot and hit powerfully to leg, she reached her fifty off 33 balls in the 10th over with the score at 102 without loss. She finished the game with two sixes in three balls off Linsey Smith's left-arm spin.
The Diamonds, for whom Davidson-Richards had Mandhana caught at long-on, have now lost three from four games.