Weather Watch

New weather station brings windfall of real-time data

Chris Arndt of and John Lindsey installed a Davis Vantage Pro ll weather station on the Cuesta Grade overlooking San Luis Obispo.
Chris Arndt of and John Lindsey installed a Davis Vantage Pro ll weather station on the Cuesta Grade overlooking San Luis Obispo.

Last week, Chris Arndt of and I installed a Davis Vantage Pro II weather station at a remote site 4 miles northeast of downtown San Luis Obispo on the Cuesta Grade. The equipment will provide critical weather data to firefighters and meteorologists.

The location, which is at an elevation of 2,620 feet, already is home to one of PG&E’s communications facilities that provide information to line crews to help restore electrical service in case of outages.

Over the years, Arndt has added more than 25 Davis weather stations — from the top of the Condor Lookout facility at 3,190 feet on Hi Mountain about 15 miles east of San Luis Obispo, to the Point San Luis Lighthouse and areas in between.

The new station will measure — minute by minute — temperatures, rainfall, wind speeds, humidity, barometric pressure and even peak solar radiation.

Ron Alsop, San Luis Obispo County’s emergency services manager, noted the importance of this new weather station.

“This particular location on Black Butte will be especially useful, along with other information, to determine if there would be a potential for evacuations of residents along San Luis Creek due to flooding,” he said.

This location is at the uppermost location of the San Luis Creek Watershed and can receive extraordinarily high amounts of precipitation. The topography along the Cuesta Grade plays an important role in higher rainfall anomalies.

Santa Lucia Mountains force moisture-laden winds blowing horizontally from the Pacific Ocean to turn vertical or upward. As the air mass is lifted up over these mountains (upwind), it cools and eventually reaches its dew point temperature. When this occurs, either clouds, drizzle or rain will develop on the windward side of the mountain.

Like squeezing a wet sponge, moisture from this air mass is released in the form of precipitation. This is also called orographic enhancement, or uplift.

It can take several hours for rainwater along the Cuesta Grade to flow into the creek, providing ample time for warning of possible flooding.

Accurate weather forecasts are important to many businesses, especially for a utility company, which has to know about heat waves, heavy rains and winter storms that could affect the system. The spread of reliable and accurate weather stations that report in real time over the Internet has dramatically increased weather forecast accuracy overall.

These weather stations are particularly suited to areas such as San Luis Obispo County, which has an abundance of microclimates. For weather watchers, it is fascinating to compare their community’s rainfall totals and temperature ranges with those in other parts of the Central Coast. For many, it’s a source of pride that their location recorded more rain than somebody else’s.

People with orchards, vineyards and gardens can tell whether the air temperature is dropping toward freezing and can take measures to protect their plants. More notably, weather station data can be used to keep firefighters safe.

“The primary factors that influence the spread of wildfires are fuels — dry grass, brush and trees — topography, ‘lay of the land’ and weather,” said Robert Lewin, fire chief for Cal Fire in San Luis Obispo. “Out of these, weather is the most unpredictable. Real-time weather information on the fire lines from these stations allows us to determine if we need to move firefighters out of harm’s way when the winds shift or increase.”

PG&E’s Diablo Canyon Power Plant relies on accurate weather and marine forecasts. Besides the new station on Black Butte, PG&E uses 12 meteorological towers that have anamoters to measure the winds and resistance thermometers to report temperatures. PG&E also has three SODAR (sonic detection and ranging) systems to produce vertical wind profiles along with a Waverider buoy to record ocean wave heights. These units are stationed throughout the Central Coast to gather data.

And, systemwide, PG&E has a team of meteorologists who use weather forecasts to populate tools that can predict outage locations and severity.

If you would like to participate in a “Weather Watchers” tour of Diablo Canyon Power Plant and lands, which will include atmospheric and oceanographic instrumentation used for weather forecasting and other interesting weather information, please email me at to register.

These tours will be offered Oct. 22 and 29. The tour will start at 9 a.m. at the PG&E Energy Education Center and will finish by noon.