When I got out of the shower last night, I asked HB, "Did you use my shampoo, or did we have a serious increase in atmospheric pressure?" During the shower, I had noticed that my shampoo bottle was compressed in the middle - something it had decidedly not been when I'd used it the night before - and when I opened the bottle, a fountain of shampoo splurted out.
These are symptoms typically associated with taking your shampoo on an airplane, or traveling with it from higher altitude to lower altitude, both examples of increased atmospheric pressure producing exactly this effect on sealed, flexible plastic bottles.
HB told me he definitely hadn't used my shampoo, and a quick glance at wunderground.com proved my intuition right. Pressure that had been holding steady around 29.9mmHg had a sharp increase in the course of a few hours to over 30mmHg on the night of the 23rd.
Maybe my new-found homemade barometer will come in handy during hurricane season.