According to an announcement released on Turkish Airlines' website, the cancellations are due to Hurricane Sandy's dangerous approach to the east coast. Turkish Airlines has cancelled all flights to Washington and New York scheduled for October 29th and October 30th.
The THY flights cancelled are as follows:
October 29th-TK 0003-Istanbul-New York
October 29th-TK 0004-New York-Istanbul
October 29th-TK 0001-Istanbul-New York
October 29th-TK 0007-Istanbul-Washington
October 30th-TK 0012-New York-Istanbul
October 30th-TK 0008-Washington-Istanbul