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Davis Instruments Weather Club
July 2008
In This Issue:
NEW PRODUCT ANNOUNCEMENT:
WeatherLinkIP
WeatherLinkIP lets you automatically upload your data to the web.
The latest member of our Davis weather family,
WeatherLinkIP has been eagerly awaited by many not-so-technically inclined weather buffs. It takes all the trouble out of uploading your data to the Internet – you don’t need a website, or even a computer. You don’t need to speak HTML, or even know what HTML is! Your data goes from your console right to the Internet, without you so much as typing a single forward slash. (You will, however, need a PC to view your data online, and you will need Internet service and a DSL/router or hub.)
WeatherLinkIP comes with a special datalogger that you plug into the back of your Vantage Pro console, Vantage Pro2 console, or Weather Envoy and connect to your cable or DSL router/hub. WeatherLinkIP instantly starts uploading your data to www.weatherlink.com — without you doing anything else. Leave the data logger plugged in to your console or Weather Envoy and it will upload to your account on www.weatherlink.com automatically. Because WeatherLinkIP is simply connected to your router/hub and console/Envoy, you'll have the full features of WeatherLink software at your fingertips throughout your computer network. Once your data is uploaded, you and other users can view your current data directly at weatherlink.com.
Are you a current owner of WeatherLink? We don’t want you to be left out of the ease and fun of WeatherLinkIP, so we’re offering you a $165 rebate if you upgrade now. Call Davis customer service (510 732-9229) for details.
WeatherLinkIP lets you:
- Automatically upload data to third-party weather sites including CWOP (Citizen Weather Observer Program), the GLOBE Program, and more.
- Get e-mail alerts of current weather conditions or simple alarm conditions.
- Download the data to your PC for all the powerful charting, graphing, and analysis as our standard WeatherLink.
You can order your WeatherLinkIP directly from our website. If you have questions, please check the FAQs or contact our customer support team.
WEATHER STATIONS IN ACTION:
Weather Wizard III Hovers Over Hovercraft Ferry
A Davis Weather Wizard III stands guard over the Hovercraft ferry in Southsea in the United Kingdom.
.Our UK distributor,
McMurdo, wrote to let us know that they had installed a Weather Wizard III and WeatherLink at the
Hovertravel waterfront in Southsea, on Great Britain’s south coast. This is cool, first, because it is a Davis weather station, of course, and second, because it is helping folks get from Southsea to Ryde on the Isle of Wight via hovercraft ferry! The 70-metric-ton vessel whisks 130 folks across the Solent in just 10 minutes. It is the world’s longest running commercial hovercraft operation.
Hovercraft are amazing amphibious vehicles. Fans pull air into a flexible structure under the hull that traps it between the hull and the surface. As soon as the air pressure underneath the craft exceeds the force of gravity, the craft rises and hovers. This means almost no friction and very little power needed to move the craft forward. It also means that the surface is almost irrelevant. No piers are needed, because the ferry can just glide up over the beach. Hovercraft cause no wake, don’t damage plants, can cruise over shallow or rocky water, and are quiet.
The Isle of Wight has its own
weather station network, featuring, of course, Vantage Pro2
data.
Weather Check Quiz Question 1: Hovercraft technology has NOT been applied to:
A. Trains
B. Lawn Mowers
C. Wheelchairs
(Click here for answers.)
“Stratus Stations” Use Vantage Pro2s to Keep TV, 9-1-1 Updated on Severe Weather
Justin Gentry (CW6353), is a Skywatcher for ABC 33/40 in Jemison, Alabama, and he thought you’d like to see our Vantage Pro2s as they are being used to help television stations, emergency management organizations, Homeland Security and other agencies to keep track of important weather data. Stratus Stations combine a Vantage Pro2 with remote-controlled camera and custom computer server to provide real-time monitoring of weather conditions via the internet. Justin included a link to aYouTube example of severe weather coverage using the Stratus Station Skycam network. It is pretty amazing to see weatherman James Spann in front of real time images of the problem areas, with weather data scrolling by at the bottom of the page.
Besides being a Skywatcher, Justin also reports daily highs, lows, and rain totals for ABC 33/40’s 10 p.m. news. He uses a Vantage Pro2, of course. You can see the data from his station online here.
Justin says the ABC 33/40 Skycams,as well as WAKA Channel 8 Skycams use Stratus Stations.
Justin adds, in friendly Alabamese, “Also y’all might like ABC 33/40’s blog. ” (We recommend you scroll down to see a scary photo of the skeletal remains of a jeep that was hit by lightening, while cars on the each side are only charred. Yikes.)
Weather Check Quiz Question 2: True or false: It never snows in Alabama. (Click here for answers.)
WEATHER 101:
We’ve Got the Foggiest
The fog comes
on little cat feet.
It sits looking
over harbor and city
on silent haunches
and then moves on.
Carl Sandburg wrote that, but in his San Francisco version he added a verse about it coming right back again tomorrow. Well, not really, but those of us who live along this part of the Pacific Coast know that in the summertime, fog is a repeat visitor. And we like it that way!
The beautiful, cooling fog that rolls in through the Golden Gate on many summer mornings is just one of the visible manifestations of what happens when temperature and dew point meet. (Quick review: Lowering the temperature of air, with no change in actual water vapor, increases its relative humidity, and when relative humidity reaches 100%, the air is saturated. The dew point is the temperature at which the air reaches 100% relative humidity. Adding water vapor, with no change in temperature, also increases the relative humidity and raises the dew point.)
E-News reader and engineer Peter Belch wondered if there was a formula for predicting fog, much like the dew point and overnight low trick.
“I have a 20-acre farm in central Florida, and on a rare morning will sometimes see a beautiful layer of fog about two meters thick laying about one meter above the ground in the north pasture. I have read multiple web sites' offerings while trying to understand what data I need to predict when fog will occur. The explanations seem somewhat contradictory and are not at all explicit. Perhaps there is a conversion [similar to the dew point and low overnight temperature], a ‘caloric hill’ that must be climbed before fog is formed? Please provide a technical explanation of how I may be able to use my Vantage Pro2 to predict when I can next expect to see that layer of fog.”
While fog depends not only on weather but on geography, Peter, you may be able to develop a pretty good record of fog forecasting using your Vantage Pro2 and your knowledge of your farm’s terrain.
Fog happens (but not always) when moist air is cooled to its dew point and below, and/or when water vapor is added by evaporation, bringing the air to saturation. If that saturation is maintained by continual cooling or by continuous addition of water vapor by evaporation and mixing, you are likely to see fog. As the vapor condenses onto available condensation nuclei, it becomes visible, and the road in front of your car or the hand in front of your face become less visible. When visibility is reduced to less than 1 km (.62 miles) we call it fog. The more nuclei available, the thicker the fog. Nuclei occur naturally, but human-made air pollution also provides nuclei - the famous London fogs from coal burning are an example of "smog" - the combination of smoke and fog. Air pollution can even cause dangerous acid fog, much like acid rain.
Unlike our coastal San Francisco fog, most fog over land is caused when the ground cools overnight. Called radiation fog, this kind of fog results when a shallow layer of moist air is cooled by the earth – and is probably what Peter is seeing on his inland Florida farm. The perfect conditions for radiation fog include an afternoon rain so the ground is saturated, clear night skies to speed up cooling, a long winter night, and a light breeze of less than 5 knots to bring more moist air into contact with the ground. (If there is no wind, you end up with a thick layer of dew because only the air closest to the ground cools.) Radiation fog tends to form most thickly in low lying valleys, so Peter can make a more accurate forecast for his lower-lying pasture.
Just a few miles to the San Francisco Bay Area’s south and east, the conditions for radiation fog are frequently beyond perfect. The central valley of California often finds itself socked in with thick, persistent Tule fog. That wide and fertile valley is hemmed in on both sides by mountain ranges. Cold mountain air flows in during the night, pooling in the valley. The air in the valley has little drainage, except through mountain passes. The high pressure warmer air above the mountains presses down on the trapped cold air, and you get the very dense and dangerous Tule fog. While most radiation fog dissipates as the air is mixed on the edges and more and more sunlight gets through to evaporate the moisture, the fog in the central valley can last for days, rising a bit in the afternoon as the low sun hits only the top of the fog, and then settling again by morning. (This thick fog is not as pretty and well-loved as our San Francisco fog. In fact, it is deadly. Fog has led to many accidents on the main route between northern and southern California, including one near Fresno in 2002, in which 87 vehicles piled into each other, killing three people.)
Our San Francisco fog is advection fog, the formation of which is a bit different. In our summertime, the ocean's surface near the coast is much cooler than farther out to sea. Strong westerly winds bring the warm moist air inland over the cold coastal water, and it is cooled from below. Advection fog always requires the movement of air. (Hence the name: advection refers to the horizontal transport of air; convection is vertical transport.) Add to the mix the ample nuclei of salt from breaking waves, and you get our famous foggy summers. (The San Francisco Chronicle offers a fog forecast on its website. You can see in the animation the fog coming in under the Golden Gate Bridge, and out again like a slow wave.)
Some of our favorite coastal denizens, the spectacular redwood trees, use fog to water themselves. Redwoods collect water by condensing it out of fog onto their needles, then dripping it down to their shallow roots. Scientists in the Atacama Desert in Chile seem to have taken a hint from our redwoods, and have devised a fog collection system of polypropylene netting to capture water drops from the Camanchacas cloud banks that form near the coast and move inland. These cloud banks have always been notoriously stingy with water, never offering a drop of rain to the parched desert below. Human ingenuity won out, and the system now provides running water for several villages.
Point Reyes, just north of San Francisco, is one of the foggiest land areas in the world. But if you count places over water, then the foggiest place of all is in the Grand Bank, in the Atlantic off Newfoundland. There, a cold southward-flowing current lies alongside a warm northward flowing current. Southerly winds move the warm air over the cold current, and voila, fog. Lots and lots of fog.
A bit to the south of the Grand Bank, this same advection fog was the cause of a terrible sea tragedy in 1956, when two passenger liners collided near Nantucket. The Italian liner Andrea Doria was struck by the Swedish liner Stockholm in thick fog, killing 46 people.
Other famous foggy places include England, where the warm Gulf Stream sends moist warm air over the cool isles, and Argentina. The central United States is often fogged by warm air flowing up from the Gulf of Mexico over cooler land – so advection fog is not always over water or coastal areas. (Since the land is cooled by radiation it is actually radiation-advection fog.)
Would-be fog forecasters can check out the Weather Prediction in Education website for a list of weather conditions that indicate fog.
Fog can make for some strange 3-D shadows. Click here for a Wikipedia image of our Sutro Towers, which are often the only part of San Francisco we can see across the bay, rising out of a cloud.
Weather Check Quiz Question 3: Which of the following are fog co-creators?
A. Kelp
B. Phytoplankton
C. Caribou
D. Volcanoes
E. Wildfires
F. All of the above
G. None of the above
Extra Credit: True or false: After the Stockholm buried her prow into the side of the Andrea Doria, the crew was able to pull back and disentangle the ships. A few hours later, a girl was found on the deck of the Stockholm, relatively unhurt, and said she had been asleep in her bunk on the Andrea Doria and asking where she was now.
(Click here for answers.)
MAILBAG:
Dan Uses His Vantage Pro2 to Avoid Windshield Scraping
Dan Hamson, of Lovettsville, Virginia, uses his Vantage Pro2
to amaze and awe his friends and family. Using the powers of the mind (and the Vantage Pro2
) Dan uncannily knows on which winter nights to cover his windshield!
“If it's a calm, clear night with no approaching fronts, I use my Vantage Pro2
to tell me whether to cover the windshield or not,” Dan wrote. “As you know the air temperature can fall well below freezing overnight, but if the atmosphere is very dry - as indicated by a very low dew point - then frost won't form and I don't worry. At other times the temperature may barely reach freezing (or even a degree or two above since the glass and metal surfaces of the car can cool faster than the air) and you can get heavy frost on the car overnight. The trick, as you indicated, is judging if the air temperature will fall lower than anticipated causing the air temp and dew point to move closer together and surprise you with frost in the morning.”
They don’t call him “Dan the Amazing” for nothing.
Maybe Dew Point Doesn’t Point to Accurate Low Temperatures?
Ned Kauffman liked the idea of using the dew point/overnight low temperature correlation we mentioned in a recent issue in his garden in Dornsife, Pennsylvania (about three miles inland from the east bank of the Susquehanna River). But in reviewing old data, he was less than impressed with the accuracy.
“Our frost date here is considered May 15 so that's when we set out seedlings and keep a close eye on the weather. I took a quick look at my data for the week around that time this year. Low temperature in the morning deviated from the dew point at 6:00 p.m. the day before on the average of 5.8ºF, varying from -14.3ºF to 8.8ºF above. That 8.8 was the only deviation above for those seven days and I noted there was a trace of rain recorded indicating a front had moved in. Maybe these are within the ranges you are talking about and I am just expecting too much?”
Ned, temperature isn’t the only part of this rule of thumb. Relative humidity also plays a crucial role. The lower the relative humidity, the less accurate this system is. In fact, it goes right out the window if afternoon humidity is below 50%.
And, it is a rule of thumb, which makes us wonder where that idiom came from? Whose thumb is it anyway?
Pretty Sunset Thanks to Pollution, or Just Good Sunset Conditions?
Ric Werme, of Penacook New Hampshire, hated to see a beautiful sunset blamed on air pollution.
“I think what you're seeing is the ideal sort of sunset,” Ric opined. “I bet the sky to the west was clear and sunlight was illuminating the bottom of the clouds. This means the sunlight is going the greatest distance it can through the atmosphere giving it the most opportunity to scatter short wavelength colors (blue and green) off of dust (and pollution).”
Ric ought to know as he and his Dad have been shooting sunsets for many years.
“My father shot a couple sunsets like that when he was at CalTech in the 1940s, and I got one in the Canadian prairies in 1974. Here's one:
Check out Ric’s Penacook Weather website which is powered by Linux and Python.
Weather Check Quiz Question 4: One of these dirty little statements is false. The other two are true. Find the fib.
1. There are about 10 million tons of solid particles in our atmosphere today.
2. Air pollution can alter a person’s heart rhythm.
3. Air pollution is, by definition, caused by man.
(Click here for answers.)
Vantage Pro2s Make the News:
Blogger Recommends Vantage Pro2
Jesse Ferrell in his terrific
WeatherMatrix Blog,
says he missed a day of blogging recently because he was helping AccuWeather.com Professional Joe Bastardi install a new Vantage Pro2 at his home in
Boalsburg, PA.
Of course Jesse recommended a Vantage Pro2 and WeatherLinkIP!
YOU'RE BRILLIANT!:
Answers to Quiz Questions
Question 1: C. So far, no one is gliding up those unramped steps on a hoverchair, but it seems like a good idea to us. The French got quite a way into creating the Aerotrain, and the British and Americans were not far behind. However, the development of other high speed land transport kind of cooled the Aerotrain fervor. And you can mow you lawn with Flymo, the hover mower. You can also build your own hovercraft! Click here for plans. (Back to stories.)
Question 2: False, but not by much. Northern parts of the state receive occasional short-lived snowfalls. Alabama enjoys year-round mild conditions with average temperatures near 80ºF (27ºC) in summer and above 45 ºF (7ºC) in winter. Highs do reach the mid 90sºF (mid 30sºC). This isn’t to say that Alabama doesn’t get more than its share of severe weather. Hurricanes, thunderstorms, high winds, and tornadoes are all repeated and uninvited visitors to the “mild” weather state. (Back to stories.)
Question 3: F, all of them. In order to form a cloud or fog, water vapor must condense on particles, called condensation nuclei. A recent study at the University of Manchester has shown that kelp under stress (too much sunlight, desiccation, high ozone at low tides) emit an iodide to “detox” the ozone. This in turn produces molecular iodine which is a great condensation nuclei. Kelp plays an important role in the removal of ozone close to the earth. Phytoplankton blooms also create condensation nuclei, as do volcanoes (every Hawaiian knows what vog is) and fires. And there is such a thing as "Caribou Fog," caused by a herd of caribou breathing and perspiring enough to increase the water vapor in the cold air around them to raise the dew point.
Extra Credit 3: It’s true; even we couldn’t make up a story like that. 14-year old Linda Morgan, a passenger on the Andrea Doria was somehow picked up from her cabin and deposited on the deck of the Stockholm. Her half-sister in the next bed was killed, and on the Andrea Doria, Linda was also presumed dead. To add even more weirdness to this story, Linda's father, Edward P. Morgan, was the newscaster for ABC Radio Network, who reported the story as it was happening, in true cool journalistic style, without mentioning that his daughter was among the presumed dead. (Back to stories.)
Question 4:
1. You betcha. In the worst areas, a sugar-cube sized volume of air can contain 200,000 nasty bits.
2. Yes, and it is dangerous, especially for those with existing cardiac problems. It is estimated that as many as 10,000 people die every year from heart attacks caused by air pollution.
3. Fib alert! Natural sources of air pollution include volcanoes, forest fires, dust storms, ocean waves, vegetation, and hot springs. But we are the real villains in the creation of air pollution. Almost half the air pollution, by weight, in the United States comes from fuel combustion by motor vehicles. From there the list extends through mills and manufacturing, power plants and refineries, refuse burning, and more. (Back to stories.)
WHO YOU GONNA CALL?
Davis!
Each month after the E-News goes out, we receive messages back. Sometimes the messages are in response to a story we shared; other times they are a request for help of some kind. We read all the emails, answer those we can, and pass the rest on to the appropriate departments.We think you should know, though, that if you're interested in the fastest possible reply, news@davisnet.com may not be the best place to send your message. Questions about how things work should be addressed to tech support directly at support@davisnet.com. For general information about the products contact sales@davisnet.com. To request a catalog, you’ll find links for catalog requests on our web site at www.davisnet.com/contact/catalog.asp.
Please continue to send your comments, weather URL's, and story suggestions to news@davisnet.com. We look forward to getting your comments and any responses you have to the Davis E-News. Member participation is what keeps the Davis E-News alive and kicking.
Well, that’s it for this edition. You’ll be hearing from us again next month!
The Davis Weather Club E-Newsletter is published by Davis Instruments.
© 2008 Davis Instruments Corp. All rights reserved.
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