Davis | Weather E-news

MARCH 2009
In This Issue:

WEATHER IN ACTION
• Vantage Pro2 Flying High in Bogota
• Vantage Pro2 Enlists in the CAP Cadet Program
• When Vantage Pro2s Take a Vacation...

WEATHER 101
• Sweet April Showers Could Bring Ugly Flash Floods

TECH TIPS
• How High Should My Anemometer Be?

MAILBAG
• There's No "Jay" In Rain Collector
• Vantage Pro2 Tries Out For Role in Haunted House
• What You Thought of Our New Format

YOU'RE BRILLIANT!
• Quiz Question #1
• Quiz Question #2
• Quiz Question #3
• Quiz Question #4
• Quiz Question #5
• Answers to Quiz Questions

Who You Gonna Call?

Canal Clima has installed a Davis Vantage Pro2 at the El Dorado International Airport in Bogota Colombia as part of a weather station network.

Guillermo Jaramillo of Canal Clima, in Bogota, Colombia, wrote to tell us about an exciting new project that will bring weather data directly to Colombians.

"We are implementing the first online meteorological weather service in the country. Fifty Davis Vantage Pro2 weather stations will be placed in principal Colombian cities and international airports, in the biggest and most innovative private weather project in our country yet conceived. We have created an Internet portal were our users can view in real-time the Davis weather stations' data on our Canal Clima web site. The Vantage Pro2 is the chosen one for this project because of its great performance and easy integration. We have developed a great web application based on .NET, JAVA and FLASH in order to publish the Vantage Pro 2 and other Davis weather station information on the web."

This story was contributed by Dave Wait, Unit Commander of the Offutt Composite Squadron of the Civil Air Patrol. The Civil Air Patrol is a non-profit auxiliary of the United States Airforce. Volunteers share a passion for aviation and help support their communities by working in emergency services, disaster relief, aerospace education, and providing youth cadet programs. Cadets range in age from 12 to 20 years old.

To help the cadets of the Offutt Composite Squadron of the Civil Air Patrol, in Bellevue, Nebraska, learn about the weather, the unit recently purchased and installed a Davis Vantage Pro2 weather station at their headquarters.

Weather is one of six aerospace areas that are taught to the members of the organization as part of the Civil Air Patrol aerospace education program. The unit found itself struggling to find a way to teach the cadets about weather that would be both fun and interactive. They determined that a weather station with which the members could interact would help with this education.

The cadet members held a fundraiser to earn enough money to purchase the weather station. During an aerospace education meeting in December, the Aerospace Education Officer, Lt. Col. Robert Whelan, led the cadets in putting the station together. The station was installed on the roof of the building and data started to flow into the system.

The Vantage Pro2 is now used by the cadets to log current temperature conditions and forecasts. The station is used also used each week to determine if conditions are appropriate for the cadets' outside activities. The cadets enjoy seeing how wind and temperature changes vary throughout the day, and how the console forecasts the weather.

.. they might go to the Turks & Caicos Islands. This lucky one belongs to Seamus Day and sits "on the very edge of the island, sited on Grand Turk in the Turks & Caicos Islands, just pure ocean until you hit Africa to the east 2,500 miles (4,200 km) away."

The Vantage Pro2 enjoys the same view as Seamus does when he looks out his home's back window. "We are right next to the ocean, but elevated about 110 feet (35 m) on a cliff with a path to the beach below."

Seamus got his station for use in his helicopter company. The company has since been sold, but the weather station stayed with Seamus.

While the weather is generally, well, fantastic on Grand Turk (some restaurants require that gentlemen wear "dress shorts" for dinner, and one time someone needed a sweater in the evening), Seamus' station has seen some weather action. "We occasionally get hurricanes here, last year being the worst in fifty years with Hanna and Ike back to back, in a single week. Hurricane Ike came barreling in from the northeast in this exact position, with winds at 145 mph (233 kph). We are in the trade winds so we get high average wind speeds year-round, mainly from the east, with lots of sunshine and very little rain, allegedly only 27 inches (686 mm) per year; I will confirm if this is true next year!"

Back in 1557, an American colonist named Thomas Tusser wrote: "Sweet April showers, do spring May flowers." We think he was trying to get his fellow colonists to look on the bright side of things and realize that "bad" things sometimes lead to "good" things.

As weather buffs we don't know how pleased we are to have rain lumped into the bad category! Rain, well all precipitation, really, is one of our favorite weather phenomena along with wind, atmospheric pressure, humidity, and temperature.

Rain does indeed bring forth May flowers, but also, sometimes it brings flash floods. (Where's the proverb in that Mr. Tusser?)

In the last ten years, flash floods and river floods have killed almost 100 Americans every year. (Heat is the only weather phenomenon that kills more people each year.)

Flash floods happen suddenly (hence the name), forming in less than six hours. This sets them apart from "regular" floods, such as river floods, which can often be predicted days in advance. They are caused when a heavy rain falls over low-lying areas, especially when the soil is already saturated. They happen when rainfall intensity and duration match up, in a very bad way.

More than half the fatalities happen when people try to cross flooded intersections in their cars. This is because people are generally not very good at judging the depth and danger of flooded streets. (And can't actually see the roadway surface, which might be a big deep hole.) While two feet of water doesn't seem like much at all, especially if you are safely inside a big, heavy car, it is enough to carry you and the car away. (Another fact we tend to forget: cars are buoyant.)

According to the NOAA , "Water weighs 62.4 lbs. per cubic foot [1,010 kg per cubic meter] and typically flows downstream at 6 to 12 miles an hour [10 to 20 kph]. When a vehicle stalls in the water, the water's momentum is transferred to the car. For each foot the water rises, 500 lbs. [226 kg] of lateral force are applied to the car. But the biggest factor is buoyancy. For each foot the water rises up the side of the car, the car displaces 1,500 lbs. of water. [For each meter the water rise up the side of the car, the car displaces 2,040 kgs of water.] In effect, the car weighs 1,500 lbs. [2,040 kg] less for each foot [meter] the water rises."

So this spring, know the flood dangers of your community before "sweet April showers" become too intense and too long to be sweet. If asked to evacuate, do it. Get out of low lying areas such as canyons. Do not be tempted to drive across a flooded roadway.("Don't drown; turn around.") If you find your vehicle stalled in a flooded road way, leave it and seek higher ground. ("Better wet than dead.")

You can see how much rainfall would be enough to cause a flash flood in your area on the National Weather Service's Flash Flood Guidance page. The NOAA web site can also show you if any national flash flood warnings are in effect.

Harry T. Thames of Gulfport, Mississippi, was interested in the pretty photo of Ivan and Susan Cross's Vantage Pro2 up in Washington. He asked a good question: Is the wind speed accurate or within acceptable range on top of a pole like this?

Many of our weather station owners mount their integrated sensor suite (or ISS, which is the outdoor part of the station: the rain collector, outside temp/hum sensors, anemometer, etc.) on the same pole, with the anemometer just above the rain collector. That's how it is pictured on the box and in our catalog, and it is the fastest and simplest way to set it up. Such an installation is fine for most uses, but it really isn't the optimal installation for the most precise wind data. If you are a real stickler for accuracy, then the Crosses have it right!

When you choose a location for your weather station, called "siting," you will look for one that best suits all the sensors.

Optimal siting for the temperature sensors is about 5 feet (1.5 m) from the ground. The best surface under the sensor is grass, or dirt. (If you live in a snowy locale, the temperature sensors should be about two feet from the average high snow level.) Second best is a rooftop location, at a height of 5 feet (1.5 m) from the roof surface. This is a good height for your rain collector, as long as you have been careful to avoid "rain shadow" caused by nearby obstructions, such as a wall. (Rule of thumb: the top edge of the rain collector should be no less than twice the height away from an obstruction such as a fence, tree, or building.) At this height, you can perform routine maintenance and cleaning of your rain collector and tipping bucket without a trip to the roof.

However, optimal siting for the anemometer is not five feet off the ground. The most accurate data is captured at about 33 feet (10 meters) from the ground! While this may be impractical in some home installations, it is a good rule of thumb to mount the anemometer about 6 feet (1.8 m) higher than any trees or buildings within 65 feet (20 meters). (Airport anemometers are sited at 10 meters high.)

So the absolute best way to site your station is do as the Crosses did and put the anemometer up high, either on a pole or on the roof, while the rest of the sensors are mounted at 5 feet (1.5 m) . That is why your Vantage Pro2 anemometer came with a 40 foot (12 m) cable. (If you have mounted your anemometer on the same pole as your rain collector, that cable is probably coiled up and tucked out of the way.)

For most home users, the accuracy may be "good enough" if the anemometer is mounted with the rain collector and other sensors, especially if you can site it far from buildings and trees, and a high as possible.

But if you want to separate the anemometer, and the 40 foot (12 m) cable is not quite long enough, you can order a 100-foot (30 m) cable. Even better, you can order an Anemometer Transmitter Kit , which will make your anemometer wireless. Then it can be quite a distance from the rest of your ISS.

Our Weather Club E-Newsletter readers seem to have a love/hate relationship with birds. They hate 'em because they uh, drop stuff, into their rain collectors. But they love them because that gives them a chance to design the ultimate bird proofing system!

Craig Correll of Carlsbad, California, is the perfect example. "All the birds in the neighborhood like the high location of our weather station," he wrote. "They think it's a 'dump station.' At least one cup of guano accumulated in a six-month period, effectively reducing our measured rainfall in Carlsbad (near San Diego) to zero. While San Diego is known for a very arid climate, we do get rain. However in our case all we got was doo.... and I really don't want to measure it. Solution: two fairly long hose clamps (6 inches [15 cm] each or a bit more) and five welding rods cut to 5-inch [13 cm] lengths. Connect the hose clamps together to make a 'crown' large enough to fit the rain collector. Then weld or solder (theoretically even glue) the welding rod sections to the hose clamp crown at one-inch intervals. Bend every other rod out a bit. Place the crown on the rain collector, tighten up the hose clamps and you are done."

An elegant solution, Craig. Even the blue jays agree, in fact, here's one stopping by for a closer inspection of Craig's welds.

"I'm not sure if they have bombed an anemometer cup yet. I'm thinking of a way to put a spike on the pivot point of the wind vane now, but I'm concerned that it may throw off its accuracy. Any ideas? The culprit: Aphelocoma californica (Western Scrub Jay) also, Mimus polyglottos (Northern Mockingbird) -- not pictured."

Our tech support team says your rain collector solution is fine, but they are going wild with head shaking and hand wringing over Craig's ideas to accessorize the wind vane, that marvel of perfect weight and balance. They suggest mylar streamers or tape, starting a feral feline rescue operation, instituting dawn cymbal-band practice... anything but screwing up the delicate balance and motion of that wind vane!! NO SPIKE, Craig!

Iridescent bird tape, such as this product from drillspot.com or BIRD-X.com, might be just what Craig needs to keep feathered friends at bay.

Dannie Fox, of Ventura, California, sent this creepy photo of a poor old web-tied Vantage Pro2.

"I read with interest your article about Jerry MacFarland," Dannie Wrote, "and his problem solver for birds. I am hoping someone will have a solution for my problem which is spiders. They get inside the rain bucket and actually build webs strong enough that the tipping buckets cannot move; so it can be raining cats and dogs out side and the console shows no precipitation. I can clean out the bucket of all webs and after a day or two they are back and my rain gauge is inoperative again. If anyone has a solution for this problem it would be much appreciated."

Another photo Dannie sent shows the anemometer on a separate pole mounted on a higher peak above the rain collector and radiation shield. So our first suggestion would be that Dannie moves the rain collector down on the ground where it is easier to access, and maybe not on the spider migration path. (See the Tech Tip story above.)

Also, when Vantage Pro2 was brand new, we quickly learned that some of the cable access holes are big enough to be inviting to bugs. On later models, we corrected this. But if you have one of the earlier ones, we can send you a plug to cover those holes and keep the bugs out. You can email support@davisnet.com or give them a call (510 732-7814) for details.

Oh, and the one thing our Tech Team finds more frightening than spiders is pesticides on the rain collector, so don't you dare! (But we have heard that some of our bugged users had good luck with hanging a pet flea collar on their station. Be sure to follow the directions in handling a flea collar.)

We got a lot of great feedback on our new e-newsletter format, and every response was much appreciated. Most of you were happy with the new design (except for our error on the index links), but enough of you said that you liked to see the whole newsletter in the email to make us make that change. Now you can see it all in the email, with working links, but if it does look strange in anyway you can click over to the online version.

Our favorite response was from storm chaser Chris Caldwell (who's no stranger to our e-newsletter), of FAST UNIT 55, First Alert Storm Team: "You already make the perfect weather station and I'm sure with time the NEW email version of the newsletter will be perfect as well."

Runner-up favorite was from John Menart, of Glendora, California:"5 words. I think it is terrific."

Our least favorite came from a reader in Chattanooga, Tennessee, who must have been having a very cranky day and suggested whoever made the changes ought to be "taken out back and whipped." Yikes. We're going to avoid any unnecessary trips to Chattanooga for the foreseeable future.

We appreciate all your comments, even our Tennessee friend's. It was really fun to hear from those of you who did respond. So much that we leaving the "tell us what you think" link right here on the bottom of the page!

What Do You Think of the E-Newsletter?
How can we improve? How do you use your Davis weather products? Email us at news@davisnet.com.

Question 1: What weather extreme is Colombia famous for?

Constant rain! Lloro, Colombia has the arguable first place record of an average annual rainfall of 523.6 inches (13,300 mm). But this is an estimate, and not considered "official." But no worries, Colombia. We just have to go a little south and a little lower to Quibdo to get an official record of 354.0 inches (8,992 mm). (Only Mawsynram, India, and Mt. Waialeale, Kauai average more than Quibdo.)

At 550 miles (885 km) southeast of Florida, just east of Cuba, that calm aquamarine water off Grand Turk may seem like the Caribbean Sea, but it's the Atlantic Ocean.

Question 3: When is a drop of liquid water falling from the clouds to earth not rain?

When it is less than .5 mm in diameter. Then it is drizzle. (Source: Meteorology Today, by C. Donald Ahrens)

Extra Credit: Joe: "We had had a ton of rain yesterday." How much rain would it take to make this true?

Not that much, Joe. A mere .01 inches would do it. (It takes 325,851 gallons to cover a one acre surface to a depth of one foot. At 8.34 pounds per gallon, that's 1213 tons per foot, or 101 tons per inch.)

Question 4: What is the first and most important thing to consider when siting your weather station?

Safety. If you fall off the roof or ladder or electrocute yourself by touching a power line or getting hit by lightning, your weather data could become irrelevant.

Question 5: We pilots know to give Virga a wide berth because the air around it is quite turbulent. Do you know why?

Here's Ward's answer: "In the presence of virga, the evaporation process takes in latent heat from the drier air. The resulting cool air, surrounded by warmer air, often causes severe turbulence at the boundary. Also, so-called dry thunderstorms are those that produce virga. This type of thunderstorm, which produces no ground level precipitation and frequently extensive lightning, can be the cause of massive wildfires when they occur during the dry season and don't contribute fire-dousing rain. Virga can be either snow or rain, which changes to the vapor state before hitting the ground. Pretty to look at; good to stay away from."

Davis!
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Well, that’s it for this edition. You’ll be hearing from us again next month!
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