Presumably an instrument problem caused the 89. Maybe rain caused a power blink, or maybe someone bumped the anemometer.
I can imagine the software calmly analyzing this: "Hmm. I see 89 MPH. That's a SQUALL. Does ConditionName == Number? Yes. Quality control: OK!"
NWS does apply human checking sooner or later, so I'm sure this bit of amusement will be fixed.
The current icon shows Polistra using a Personal Equation Machine.