Normally one water park will close at a time, and the first one will close around the end of October. This is necessary as all the pumps have to be torn down and rebuilt because of all the sand that gets in them. Since the October schedule shows both open until the end of the month, my thoughts are as follows.
One park will close on either the last Sunday in October or the first Sunday in November. About nine weeks later, usually the first Sunday in January that park will reopen and the other one will close. On the second or third Sunday in March you will then have both parks open again.
I would expect that Typhoon will always be the first one to close. Blizzard is themed to Christmas, so there would be minimal additional holiday decorations required.