Sorry, but I am a retired CPA, so "weathering" is only a hobby that sometimes I struggle with. When you say uploading altimeter, what does that mean? I am using Weatherlink 6.0.3. I am surprised that Davis support did not identify that as the cause. I spent over one hour on the phone with John from that group, and he could not explain it--he was looking at my data on CWOP and WU and I was telling him what was on my console. He was "perplexed." As you know, CWOP "grades" our weather data and tells us where our data might be off. If I correct my barometer readings (using nearby large airports here in Chicago) that get uploaded to CWOP to get closer to their "grade," the display on my console will be wrong and my data on WU will be off so I guess I will accept CWOP as being close but not precise.