St. Patrick’s Day is nearly three weeks away, but New Jersey’s stellar roster of parades is about to get underway. More than 30 parades honoring Saint Patrick, the primary patron saint of Ireland, are being held over the next four weekends. One of the biggest — the Belmar-Lake Como St. Patrick’s Day parade — is happening this Sunday. Now in its 51st year, the parade has 6,500 registered marchers as of Monday, the highest in its history, according to organizer Sheila Murphy. While many parades have a single grand marshal, along with other honorees, this year’s Belmar/Lake Como parade has four g…