International banks will pass their trading from one centre to the next, so London hands over to NY, which hands over to Tokyo etc.
When a centre takes the reins, they may not want to keep the same position as the previous one; perhaps London was happy being long Euro but NY wants to shift that to be long Yen, or they can't maintain the tight spreads around the Cable prices. So during that initial handover period, the easy thing to do is just widen all the spreads until you've got your system configured and set up the way you want it, then you can bring the spreads in.
answered Feb 28 '18 at 13:44
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