Friday, November 20, 2009

Blue Hill Observatory

I didn't realize I was in such good company! The Blue Hill Observatory in Milton, MA is the location of the oldest continuous weather record in North America.

Weather Station Quality

After watching observations from my Davis Vantage Pro2 and other nearby weather stations (via, I can say with some confidence that the VP2 is one of the better stations out there. Even excluding cases where other stations have produced completely bogus data, the VP2 seems to produce measurements which are more consistent with nearby airport measurements. Most stations on Wunderground seem to produce good temperature measurements, but some of the humidity values are clearly off. Here are observations from two Oregon Scientific WMR series personal weather stations, two Davis Vantage Pro2 personal weather stations and two nearby airports:

StationTemp (F)Dew Point (F)Humidity
All of the personal weather stations are in the same general area and are certainly not distant enough to explain the differences in humidity. As you might guess, the first two are the Oregon Scientific WMR series stations, the next two are the Davis VP2s and the last two are airports (all in the western suburbs of Boston). The VP2 dew point/humidity measurements match the airport measurements reasonably closely. Not so for the Oregon Scientific WMR series stations which seem to report consistently low dew point/humidity readings.

Note: My station (KMANATIC3) and KMAWELLE9 are extremely close to each other. The other two personal weather stations are the next closest VP2 and Oregon Scientific WMR series stations. Data was collected at appx. 1:30pm 11/20/09.

Saturday, November 7, 2009

KMANATIC3 is live!

I dug a 2' 8" hole in my yard using a pole digger, mounted my Davis Vantage Pro2 on my 8' fence post and began recording real outdoor weather observations. I also created a Wunderground station, KMANATIC3, and set up weewx to post weather information to Wunderground every 5 minutes. If you are following along at home, one thing I should note is that I got an INVALIDPASSWORDID error from Wunderground up to about 10 minutes after I created the station at But, then it went through fine without me having to do anything.

I must say, it's been a pleasure to use weewx. Hard to believe it's such a well-made product in it's first release!

Thursday, November 5, 2009


I installed my data logger to my VP2 console, installed weewx on my computer and I'm now successfully logging the weather conditions of my study and bedroom every 5 minutes! The only problem I had with weewx was that the startup script didn't respect the change I made to WEEWX_ROOT. But, that was an easy fix. Otherwise, weewx was easy to install. I doubt the weewx daemon needs to use the 50 megs of memory top is reporting, but I also doubt that I'll ever notice on my 8 gig machine...

Monday, November 2, 2009

siting and 8' pole

I'm getting closer to having my weather station up-and-running. I selected an installation location over the weekend. We have a lot of trees and don't get a ton of sunlight, so it was a bit challenging to find a spot with (1) at least a few hours of direct sunlight (for the solar panel), (2) no rain obstructions directly overhead and limited rain shadow from trees, and (3) semi-accurate wind measurements (not too close to building/hill), (4) without being an eyesore. But, I think I've found a decent spot. There's no way I can follow all of wunderground's weather station siting recommendations, but I know my measurements aren't going to be airport quality!

I also figured out how I'm going to mount the station. I ended up in the fencing section of Home Depot and found an 8 foot, 1 5/8" diameter fence end post, which should let me position the station about 5 feet off the ground. I also bought a pole digger---it sounds like I just need to put the pole about 2 1/2 feet into the ground and make sure the ground is well compacted around it---not quite as challenging as installing a basketball hoop or fence.

Wunderfixer and Weewx

Sounds like if I'll want a relatively clean history of my station stored at, I'll need the Wunderfixer, which is a utility for updating wunderground records to match your weewx or wview records on a given day. I.e. it sounds like you first need to do the detective work to discover the lapse at wunderground. But, then, this script makes the fix easy.

This discovery also leads me to believe that weewx may be the recording/uploading software I should use. Whereas wview is written in C++ and handles a wide variety of configurations, weewx is written in Python and is written for exactly my situation---uploading data from a Vantage Pro2 to using U.S. units via a desktop machine (wview is so efficient that it can run on a Linksys NSLU2). Since the weewx code base is Python and much smaller (than wview's), it should be much easier to understand and modify. Another plus is that the author reported no DST issues whereas from what I read on the mailing list, it sounded like wview only recently switched to using UTC-based timestamps...