The elevation of the property on which the station is located is just about exactly 300 feet above mean sea level. The station sensors are located about 15-20 feet above the ground. This information may be useful when evaluating forecasts based on elevation.
Just FYI, the inside temperature sensor is located in a room that contains equipment that warms the room when it is operating. Most of the house is several degrees cooler than what is shown, depending on outdoor weather.
I located the anemometer (speed) and wind vane (direction) in as unobstructed location as I was able to find on my site. There are, however, high trees in the area that no doubt have some effect on the readings.
As is customary, the wind direction reported is the direction from which the wind is coming.
High winds in this area seem to run around 30-33 mph. The highest reading during the big storm in December 2006 was in the low 40s. (There are a lot fewer trees in the area since that storm.)
The rain season/year shown on these reports is January 1 - December 31. The Seattle Office of the National Weather Service' (NWS) official rain season runs from October 1 - September 30 as the heaviest rainfall in the Seattle area occurs in October through December. I chose to use the calendar year to avoid confusion.
Rain rate reflects the amount of rain that would fall if it rained at that rate for a full hour. Rain rate is calculated based on the amount of time that elapses between 0.01 inch readings
Day/Month/Year rain totals are self-explanatory—the starting time for each is midnight.
Storm rain totals reflect the amount of rain that has fallen from the beginning of the current rain storm (at least 0.02 inches) and continues until no rainfall has been recorded for a 24 hour period.
The rain sensor is not heated. It captures the water content of snow when the snow melts, which may be hours or even days after the actual snowfall.
Evaptotranspiration (ET) is a measurement of the amount of water vapor returned to the air by evaporation and transpiration in a given area. Effectively, ET is the opposite of rainfall, and it is expressed in the same units of measure—inches. It can be used to estimate the need for watering in the growing season.
The weather station uses air temperature, relative humidity, average wind speed, and solar radiation data to estimate ET. It is calculated once an hour on the hour.
The solar radiation reading gives a measure of the amount of solar radiation (direct and reflected from the rest of the sky) hitting the solar radiation sensor (which is on a horizontal surface) at any given time. This measure is expressed in watts per square meter (W/m2).
Energy from the sun reaches the earth as visible, infrared, and ultraviolet (UV) rays. Exposure to UV rays can cause numerous health problems, such as sunburn, skin cancer, skin aging, cataracts, and can suppress the immune system. UV rays also create essential vitamin D-3 in our skin.
The readings shown do not account for UV reflected off snow, sand, water, or other surfaces, which can significantly increase your exposure. Nor do these readings take into account the dangers of prolonged UV exposure.
The readings shown do not suggest that any amount of exposure to UV is safe or healthful and should not be used to determine the amount of UV to which you expose yourself. Rather, it can advise of situations where exposure is particularly unacceptable.
UV Index is an intensity measurement developed by Environment Canada and later adopted world-wide. The National Weather Service predicts UV Indexes for the following noon. The UV Index reading shown on this report is a continuous real-time measurement.
The US-EPA categorizes index values as follows:
Index Values |
Exposure Category |
0-2 |
Low |
3-4 |
Moderate |
5-6 |
High |
7-9 |
Very High |
10+ |
Extreme |
This is where NWS forecasters explain their thinking and give the rationales behind their forecasts. If you REALLY need to know what the forcasters think is going to happen with the weather in the next few days, this is a good place to check. In my experience, these discussions are very candid. When they are SURE of what is going to happen, they say so. When they are GUESSING, that is usually evident as well ("The models are all over the place, but I gotta say something, so..."). When they say they are giving a climatological forecast, they are saying that the forecast is what is typical for this area at this time of year rather than necessarily being based on weather models or other readings.
This is also a good place to get early indications of future weather events. It is common for possible future storms to be mentioned in the forecast discussion several update cycles (or even several days) before they are included in the official forecasts.
The Forecast Discussion is updated approximately every 6 hours: roughly 3 am, 9 am, 3 pm, and 9 pm. Note that these times are approximate, and it is not unusual for an update to be as much as an hour (or occasionally more) "late".
The discussions tend to contain lots of jargon and obscure abbreviations. However, even if you don't understand every word, you can get the drift of what they are saying by skimming through the discussion. A couple of sites—NWS Contractions and a Glossary help a lot in reading the discussions. Times are given in 24 hour Universal Time (aka Greenwich Mean Time) when shown with a 'Z' after the time—Norwood 7 (daylight time) or 8 (standard time) hours earlier. Cities/weather stations are referred to by 3 or 4 character abbreviations—a list of Washington cities is here (the full international list is here). They also refer a lot to computerized weather models—GFS, NAM and others—once you know that they are there, it is easier to figure out what they are saying.
The NWS is currently experimenting with an enhanced version of the Forecast Discussion ("Enhanced" on my main menu). This version includes links to graphics from the various models so you can actually see what they are describing in the discussion. There are an excellent FAQ and Legends Help which are humorous while also being good tutorials on weather forecasting and weather models. Note that, in my experience, the enhanced version tends to be posted a bit later than the regular Forecast Discussion.
This weather station is a registered participant in the CWOP. The main page links to a summary report of data sent from this station. At any given time, over 4000 CWOP stations across the country and more around the world contribute data. This data is aggregated and supplied to a variety of customers, including the National Weather Service. The "NWS/CWOP Weather at Norwood Village" link on my menu is to a National Weather Service page with data from this station.
Though I make no claims of accuracy per my disclaimer below, CWOP routinely evaluates the quality of key data items (temperature, dew point, barometer etc.) submitted by each registered station. Click here for the latest report on this station. Note that comparison data are estimates calculated from readings submitted by other stations in the area. The expectation is that data from each station will approximate these estimates within certain tolerances. At this writing, my numbers look pretty good—the highest summary rating available for each data item is a green check with two 'thumbs-up'. A red cross would mean that my data are out of tolerance in some way.
Norwood Village weather information is gathered by a Davis Instruments Vantage Pro2 Plus weather station located about a block from Norwood Pool in Upper Norwood. This station has been in use since Janury 2005.
Prior to that, I used a Davis Instruments Weather Monitor 2, which was installed in December 1999.
Both stations store readings that can be downloaded to a computer and used for further analysis. I currently have most of the readings which were taken approximately every 15 minutes from the latter part of December 1999 to the present. (NWS typically takes their readings every hour.)
Data for the on-line reports is automatically updated every minute. The Summary report is based on the 24-hour day beginning at Midnight.
On the morning of December 3, 2009, the sensor suite (external sensors other than the anemometer) was moved to a more suitable location that should improve the accuracy of rainfall, outside temp, and outside humidity. The sensor suite, up to now, has been mounted on a mast attached to the chimney on the roof. It has been moved to the recommended 5 feet above a grassy surface. The anemometer remains on the roof-top mast at about 24 feet above the ground. During the move, the rain gauge registered 0.12 inches of rain due to handling of the sensors rather than actual rainfall.
This is information that I have developed for my own use and which I am sharing with the understanding that:
This page was last updated: December 3, 2009