Why is the date of the 2016 Passover a month late when compared to Easter?

Jesus was put to death on Passover eve Nisan 14. This was the first full moon following the vernal equinox.this year the vernal equinox is March 20.2016 The first full moon after March 20 is March 23 2016. This is the day that Jehovah's Witnesses will have their annual memorial of Christs death event. That is why those who celebrate Easter will be doing so on March 27 2016. The first Sunday following the paschal full moon. All seems to be in order until I check the date for Passover this year and it is April 22 2016. Can someone explain why there is almost a full month lag for Passover this year?