VA7IS Weather

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The readings are updated every 30 minutes. Reload the pages to get the most recent information.

View many weather parameters graphically. They are uploaded every 30 minutes. 

These are graphic displays generated by the software that interfaces with the wireless weather station. The flag logo in the summary panel is the Provincial Flag for British Columbia.

Tabulated  details of various parameters.

Daily Weather Stats Includes a summary of the data collected since starting to run the system on September 14, 2006.

You can also see the weather data at Weather Underground.

The temperatures read at stations in the Vancouver area, are plotted on a map here (map file: 200k).

My weather station is a package made by Oregon Scientific Model WMR968. It has wireless remote units operating at 433 MHz and a main console. The remote units are:

1. Outdoor thermometer and hygrometer.

2. Outdoor rain gauge.

3. Outdoor wind direction and anemometer.

4. Indoor thermometer, hygrometer and barometer.

Units 1 through 3 each have a separate transmitter unit that they plug into. The transmitter units contain a solar panel, NiMH storage battery pack and two AA backup up cells. Unit 4 has four AAA cells for power. All the remote units appear to only transmit periodic short bursts, during which a red LED is illuminated.

The main unit operates on 12 volts dc from a wall cube. It also has four AA cells for backup. It has an RS232 serial connection to a computer that is always running and connected to the Internet by a cable TV modem. The computer is running the Virtual Weather Station (VWS) Internet Edition software by Ambient Weather. VWS takes care of collecting all the weather information from the sensors through the main unit and sending it to this web site and the Weather Underground. It also makes a file that is used to sent the information to the Amateur Radio APRS network. VWS has many options and features that allow an almost infinite amount of customization. VWS is not free, but was included at a reduced cost with the weather station package.

I hope to learn more about the actual operation of the equipment, how the sensors work, what frequencies are used etc. I have already found circuit diagrams on the user groups.

Another free program VWSaprs is configured to send the APRS data file to Findu.com every 5 minutes. The APRS data from my station can be viewed at Findu.com.

The rain gauge is a cylinder with a funnel at the base that directs the collected rain into a teeter-totter (seesaw) with cups on each side of the pivot and a small magnet. One side fills first and then it tips to the other side, emptying the water and generating an impulse from a magnet as it passes a reed switch. The other side then fills up. When the temperature goes below zero, the rain gauge tends to stop working as it is not heated. Some stations heat the rain gauge to convert snow into water.

The anemometer is a "cup" type with three cups on arms that rotate. A magnet creates a pulse with each rotation. The following is from the Wikipedia:

One particular merit of the cup anemometer is its simplicity. However if used without electronic data logging equipment it is not well suited to leaving a record of the actual velocity at any particular moment, and hence it can leave very brief events unrecorded. Unfortunately, when Dr. Robinson first designed his anemometer, he stated that no matter what the size of the cups or the length of the arms, the cups always moved with one-third of the velocity of the wind. This result was apparently confirmed by some early independent experiments, but it is very far from the truth. It was later discovered that the actual relationship between the speed of the wind and that of the cups depends very largely on the dimensions of the cups and arms, and may have almost any value between two and a little over three. This had the result that wind speeds published in many official 19^th century publications were often in error by nearly 60%.

The wind unit was mounted on a 3/4" diameter post fixed to a deck railing at the front of the house. We are surrounded by forest and wind is quite variable - often there is no movement of air. The anemometer tends to freeze and stop turning when the temperature is below freezing. Presently it had to be removed so that the deck could be rebuilt and the railing replaced.

The outdoor temperature and humidity unit is located inside this "Stevenson Shield":
 
Tests have shown that the temperature is significantly affected if the shielded sensor is placed in the sun. One day I may make a second shield out of wood, painted white, that shields the pot saucer unit from the sun. I know aspirated shields are used, but want to avoid running power to a small fan out in the yard. The real Stevenson shield box (as used by professional sites) seems to have two sets of louvers that are arranged so that if the outer set is heated by the sun, radiation from it will be absorbed by the inner set rather than warm up the actual sensor unit. The rain gauge will be fixed to the top of the wooden unit and both will be out in a sunny part of the yard where the solar panels can work better.

I started this series of web pages from a fascination for understanding the weather. I have no past experience or training in reading the weather, other than tapping an ancient mechanical aneroid barometer and looking at a Radio Shack digital indoor/outdoor thermometer (the kind with a wire through the wall to a sensor outside). It seems that in the last few years a number of packages have become available that can automate recording the weather. I bought one of the lower cost ones by Oregon Scientific. I know there are other possibly better quality (and more expensive) systems available by Davis and Peet Bros for example. The VWS software seems to be well regarded and widely used with all makes of data gathering equipment. The VWS software seems to be updated on a regular basis as bugs are found. This can be seen in the version history.

Of course, I have learnt more since the original purchase. I found that one can download a free weather system program called FreeWX written by an Australian ham radio operator. It seems to have virtually all the functionality of VWS.

Issues

My site is evaluated by an automated system run by Philip Gladstone. Once you join the CWOP (Citizen Weather Observer Program, your data may start to be verified by automated comparison with other stations in the area. My temperature and barometric pressure check out OK, but not the dew point (humidity). This may be due to the location I am in, surrounded by large trees. I have tried to do sensor calibration with a sling psychrometer. I did not have much success and ended up leaving the unit in the uncalibrated state.

I also tried a single point humidity calibration. The hygrometer (humidity) can be calibrated quite accurately at one point - 75%. A Google search for "calibrate hygrometer" will come with a number of pages describing how to do it (They mostly seem to relate to humidors used to store tobacco products). You put some damp table salt in a small container like a bottle cap, place that and the instrument in an airtight transparent bag like a ziplock bag and leave it for at least 6 hours. The humidity will stabilize at 75%. The salt should be damp with no visible liquid. For my indoor unit, the humidity stabilized at 62%, which is 13% below the correct value. Another small pocket instrument (Thermor) read 69% in the bag. It claims ±5% accuracy, so was close to the tolerance range.

Before purchasing my system, I downloaded a free program from Ambient Weather called Weather Exchange. It allows one to view the data from personal weather stations all over the World. I recommend anyone interested in this activity should download this program and play around with it first.

Also use the Internet to evaluate the different systems available. There are various discussion forums that you can join. For example, the 9 page installation manual that is supplied with my system is rather poor. It does not tell you various things like: you have to open up the remote units and remove isolating plastic strips from the installed batteries. I found that I could download a much better 36 page manual (use the mouse right-click to download and save the .pdf file). It is for the Radio Shack Wireless Weather Station, which appears to be an identical Radio Shack version of my station.

System anomalies are listed here. Here are a few comments about the predominant wind direction.

I am a member of the North Shore Amateur Radio Club. They offer a comprehensive web site about amateur radio.

In the following link, you can access a radar plot of rainfall activity for the local area:

 

Plan your trip Local Radar Detailed Forecast

Here is another interesting link. It shows a sunlight map of the World that is updated every 30 minutes.

 Page was last updated: February 2, 2012