I think that it might be more of an apparent northward jog rather than an actual one. At 19Z the low-level circulation was at about 18.8N 91.1W and at 21Z it is near 18.8N 91.3W. A few hours earlier I noticed a second center of circulation, perhaps mid-level, to the NNE of the surface center. Keeping in mind that TD Alex is now a lot weaker, a weakening of the original surface center and development of a new one more in line with the mid-level circulation is probably what has evolved. I had located the mid-level at 19.3N 90.9W at 21Z - pretty close, and it also helps with the verification of your last initial forecast point

On another subject, I've added a few Mexico observation links on the Main Page. At 21Z the wind at Campeche was out of the east northeast at 20 knots and the SLP was 998mb.
ED