I’m looking at the predicted winds for Saturday at 3:00 PM on windy.com. In particular the northeast of the U.S. Usually, winds follow surface isolines, more or less. From the Delaware Bay to Cape Cod the winds are perpendicular to the lines and at relatively higher speeds. What is going on? At 5000’ the winds are almost directly opposite in direction.
It looks like you will have to drag the slider to Saturday at 3:00 after you click on the link.
Note that the low pressure center in the remnants of Ian is dragging a warm front which aligns nicely with the discontinuity in surface wind direction you noticed. Fronts are often characterized by sharp changes in surface wind speed and direction.