About the article “Filler Upgrades Weather Station” in the Nov. 16 Advocate: I was able to view the current weather report from Dennis Filler’s station just now using Wunderground where it is labeled “Holly Meadows River Bend Estates Station.” Good info and good to see him on the air. There is a “science issue” with one portion of the article. It states that “the main difference between barometric pressure and atmospheric pressure is that atmospheric pressure describes the pressure exerted by the atmosphere whereas barometric pressure refers to pressure measured by a barometer.” I would think technical readers and all current 9th grade science students know better. Barometric pressure IS atmospheric pressure regardless of how it was measured. Typically 14.7 psi at sea level and varying over time based on altitude, high pressure or low pressure weather circumstances, etc. Normal or typical atmospheric pressure (being the same as barometric pressure) varies with altitude above sea level and can in fact be used to measure altitude. The simplest non-radar altimeters in aircraft read altitude based on pressure. Since it changes relatively slowly over time compared to a climbing aircraft, pilots routinely set their altimeter calibrated in feet (either to zero or to the known geographic altitude of the airport) before takeoff. The pressure change downward due to their altitude after takeoff is used to read altitude in the cockpit.
Another misleading thing about the article regards forecasts. The only kind of forecast in a personal weather station (PWS) like his is based on pressure changes, clarified by the ambientweather.com website. Rising air pressure tends to mean clearing and less precipitation while dropping pressure tends to indicate an approaching low pressure center with storms and precipitation. That could be done (and has been done for many years) using a barometer and watching the trend of it’s readings. It was said that “these forecasts are generated for our location (true) and not coming out of Clarksburg Weather (also true but very misleading.)” Weather services, like Wunderground, utilize the data from large numbers of sources including PWS data from many sites but are certainly not basing their forecasts based on any one station’s data. These national (actually global) services use huge weather models running on large computers which utilize data from thousands of sources. The models can then be interrogated to provide forecasts for a specific given location on the earth. Wunderground can provide a FORECAST for a location (such as at the Parsons station location) which comes from a large complex system, not from that local station. They also provide and show on the home computer screen the CURRENT data such as temperature, pressure, humidity, etc. which DO come from the local station selected on the screen. Big difference between using data from a PWS and thinking that the PWS itself generates the forecasts. Interesting and informative article.
J.Wm. (Bill) Rymer
Lexington Park, MD 20653
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