|
|
|
The CBS4 Weather team will answer selected viewer e-mail questions during CBS4 News and right here on this page of cbs4denver.com.
Please try to keep your emails as brief and generic as possible. Be sure to include your name and hometown. 
Email The CBS4 Weather Experts
Weather Section
Lynn Zenner from Broomfield asks: Since we didn't have any 100 degree days this year, how many days did we reach 90 degrees?
Meteorologist Jennifer Zeppelin: May only had one 90-degree temperature and June didn't see the mercury rise to 90 degrees once. The last time that happened was in 2003. On average July sees the most 90-degree days with 15. This July we only had seven days that reached 90 degrees, the least number of days in 10 years. Temperatures in August have been much warmer Sunday, August 23- DIA hit 98 degrees the hottest temperature so far this year. In August, there were only nine days that reached 90 degrees or higher.
Ed Spencer from Fort Collins asks: We moved here from KC 10 years ago. We have gotten more precipitation this year, than "several" of the other years combined, (at least in Ft. Collins). I believe this is due to Pacific El Nino conditions. Do you anticipate that we will have a "wet" (snowy) Winter, as well?
Meteorologist Dave Aguilera:Typically, in strong El Nino years the Front Range and adjacent Plains have interesting winter weather patterns. In past El Nino years we have seen fewer snow storms, but, stronger snow storms. Some of these years have delivered big, blizzard producing storms early in the season and dry mid winter patterns. Meaning January and Febuary may turn out to be fairly dry. Then March, which is our snowiest month on average, March may come through with heavy snows and maybe even a blizzard or two. That being said however, the problem in forecasting for a whole season is more than just El Nino occuring. If we only had blizzards during an Nino event that would make forecasting a lot easier. There are several other factors that produce big snows in Colorado. El Nino maybe one of those factors, but, not the only one.
Anne Hudson from Brighton asks: How unusual has this Spring and Summer's weather been, considering how mild and rainy it has been?
Meteorologist Dave Aguilera:Your right this summer has been above normal for rainfall and slightly below normal for temperature. This past July was not a record setter for rain, but, was the 8th wettest on record for Denver. With 3.30 inches above normal or average for rainfall. June was also above normal for rainfall by almost an inch and a half, 1.40". As of August 27th, August 2009 is behind in normal precipitation,
Denver is .43 inches below normal. And slightly cooler than normal for temperature. Looks like we need a little more rain in August to keep this wet summer going.
Lynn Zenner from Broomfield asked: Have we ever had a summer that hasn't reached 100?
Meteorologist Jennifer Zeppelin:The answer is yes, you're probably asking because we haven't recorded one 100 degree temperature in 2009. The latest date in the year we've ever seen the thermometer reach 100 degrees was August 16, 2002. Since that date has come and gone the chances we will hit 100 this year isn't likely. Over the past 10 years there have been two other years that the triple digits stayed away 1999 and 2005.
Scott Halliday from Denver asks: Was reading your article about the rainfall in June. I've been here 40 years and it is by far the wettest June I've seen. You mention that in the first 6 months we only got a bit more than 3" of rain. Where do they measure? In April and May between the pounding wet snow and rains we got, it had to be more than 3" of moisture. In places in Lakewood where friends measured moisture it was alot more, closer to 8-10 inches. Is there any web site that records overall moisture for the year? And breaks it out by areas? If moisture is measured officially at DIA wouldn't that skew the numbers as that seems to be a pretty dry area? Thanks.
Meterologist Dave Aguilera: The official measurement is taken at DIA. This can skew, everything from temperatures, rainfall and snowfall. However, the National Weather Service measurement is the "offical Measure for Denver Records." This is the standard used in all cities that have a main airport.This is why we at CBS4 are the only station in town that does a forecast for Downtown and DIA. But, back to the rainfall question, yes due to the nature of thunderstorm rain, one area of the city can get two to three times as much rain in any given storm or season. A great website to get rainfall amounts around the city is www.cocorahs.org This has rainfall, hail and snowfall amounts from cities in Colorado and across the country.
Andrea Crawford from Johnstown asked: Last year my granddaughter, 9 yrs old, was in school in Milliken when the tornado blew through in May that hit Windsor so bad. It came near their school and the kids spent the after noon out in the hall ways listening to the noise of the wind and rocks hitting the windows. She's been very scared of windy days and dark skies, and if there's a tornado watch or warning she's literally going to pieces. I thought if she had information about weather happenings, tornadoes and such, she might me less frightened. Do you have any suggestions I sure would appreciate it.
Meteorologist Dave Aguilera: One of the things I tell my kids is that being safe in severe weather is kind of like crossing the street. Crossing the street can be very dangerous, but, if you know what to do you will be safe. When you cross the street you have to look both ways and make sure there are no cars coming. In a severe storm you have to know what to do to be safe. Stay inside, stay away from windows, those types of things.
You might also, try reading a book from the bookstore or library about how tornadoes form and what types of storms produce tornadoes. There are several good ones out there. There is also, a Weather for kids section on our weatherpage at cbs4denver.com. I don't know if you have checked that out yet. I have heard the more kids know about how storms form and what has to happen to make these storms, the less the mystery and fearfullness occurs when big storms actually happen. You may be able to turn that fear into an interest and have a future meteorologist on your hands.
Sandy Roerig from Fort Collins asks: What is the main difference between "isolated thunderstorms" and "scattered thunderstorms". How do you determine when to use one description over another?
Meteorologist Jennifer Zeppelin: Forecasters use the terms "isolated" and "scattered" to describe the coverage and chance of showers or thunderstorms in their forecast area. "Isolated" means a low risk of showers and storms, while "scattered" means a moderate risk. After looking at all the data we determine it's isolated only if we feel 10% to 20% of our coverage area will see showers or storms. For it to be scattered that means 30% to 50% of the forecast area will receive showers and thunderstorms.
Samantha Stiffler from Denver asks: whats the difference between a tornado warning and a tornado watch?
Meteorologist Jennifer Zeppelin: First of all you need to know that a watch means severe weather is possible during the next few hours, on the other hand a warning means that severe weather has been spotted, or is expected soon.
When a Tornado watch is issued the outlined area is expected see large hail, damaging winds and multiple tornadoes during the next three to eight hours. When a Tornado warning is issued that means a tornado has been spotted or detected on radar over a specific county or area.
Andi from Denver asks: You used to have the air quality during your morning weather reports and then you stopped, what happened.
Meteorologist Jennifer Zeppelin: The season ended for the high pollution advisory program March 31st. Starting June 1st Ozone action alerts will be issued for the summer months. During ozone action alert days, here are some simple things you do: do not overfill gas tanks when refueling, keep vehicles regularly maintained, tighten gas caps after refueling, mow in the evening, refuel in the evening, use new earth friendly lawn equipment. Between June 1 and August 31, the Regional Air Quality Council will issue daily ozone advisories at 4:00 p.m., the CBS4 weather department will provide the information during our weathercasts. From November 1 through March 31, at 4:00 p.m., the Air Pollution Control Division at the Colorado Department of Public Health and Environment issues daily air pollution advisories for the seven-county Denver metropolitan area.
Ted from Commerce City asks: weather people talk about this a lot what is VIRGA?
Meteorologist Jennifer Zeppelin: Virga is a form of precipitation that falls from a cloud but evaporates before hitting the ground. It's pretty common to see this kind of activity in our semi-arid climate, especially during the spring and summer. Low relative humidity and warm temperatures can cause the rain to dry up after it leaves the cloud. Virga can form some interesting patterns-the visible streaks of liquid look like feathers coming from the cloud before they evaporating.
Bill from Aurora Asks: Is there a summary of studies available that show the full spectrum of changes in Colorado due to global warming? For example, is the average temperature rising or falling? Are different species of flora/fauna invading/predominating or no longer able to live here? Has the tree line elevation changed? Are the few year round snowfields/glaciers disappearing or growing?
Dave Aguilera did some research and this what he found out from Colorado State Climatologist, Nolan Doesken: Two recent publications
(October 2008) are a good start to answering that. One is the Citizens Guide to Colorado Climate Change published and available from the Colorado Foundation for Water Education. A second and more technically oriented publication came out from the Western Water Assessment in collaboration with the Colorado Water Conservation Board. I don't remember the title and I think they may be
out of copies, but I bet it is accessible online. Contact 'Veva Deheza ' veva.deheza@state.co.us Climate data do show a small warming trend that has become a little more pronounced since the late 1990s but the change has not yet been enough to cause profound ecological changes. There are ecologists who's research show changes in elevation ranges and population dynamics of
various plants and animals -- and I can't discount them. However, the actual observed changes in climate so far have been small. We have had retreat of Colorado's few small glaciers and snow fields. This had been happening even before the recent warming trend, though. I am a climatologist and not an ecologist, but having worked with many ecologists over the years, it is obvious that climate is
important but it is usually one of many variables that affect plant and animal populations. Our world is beautifully complex.
Tom from Sidney, Nebraska asks: For the last week I have seen a very bright light (star??) in the western sky around 8 p.m. I'm sure it's there later but can't say for sure. What is it??? A satellite. It is fairly low in the sky.
Dave Aguilera: It's not a satellite, but, the planet Venus. And this year it is shining bright. The magnitude is -4.5 or even higher that's about 7 times brighter than the brightest star: Sirius. Venus was at it's brightest last week, it's now getting dimmer and dimmer every night. There are two reason for the brilliance of Venus this month. The first, is it's orbit around the sun. Last fall it's orbit was farthest from earth so, the planet looked small, now it is closer to earth in it's orbit around the sun. So it looks bigger. The second reason is planets act much in the way the moon does in reflecting sunlight and looking full. So over the last few weeks you might say Venus has been a "full Venus."
Cheryl of Denver asks: Out of curiosity, where was the official temperature taken in 1901? Was it downtown someplace? Now it is -15 degrees at DIA, but downtown it is only -3. Although this may ?officially? go down as a record, do you think that it was actually colder back in 1901?
Dave Aguilera: Denver weather observations from November 20, 1871 to January 1st, 1916 were recorded downtown from an office at Larimer and G streets(now 16th Street). After 1916, The Weather Bureau then moved to the Post Office at 19th and Stout until 1931, at which time it moved to Stapleton Airport. From 1931 to 1950 observations were kept both Downtown and at Stapleton. In 1950, on New Year's Day, Stapleton International Airport became the official Denver observing location. In March 1995, official observations for Denver began being taken at Denver International Airport. The National Weather Service is the official last word on official highs and lows, typically, their observations are taken at the given city's official airport for the sake of uniformity. In 1901, it may have been colder in the spot where DIA is now. But, we can really never know, because consistent records where not kept or we don't know of a consistent weather record kept at that site.
Gaye from Boulder asks: My father used to say that it won't snow because "it's too cold to snow". Is it true that there is a temperature where it would be too cold to snow? What correlation is there between cold temps and possibility (or not) of snow?
Ed Greene: The short answer is: not really. Warmer air does have the ability to hold more moisture so with somewhat milder temperatures (but still below freezing) we tend to see higher snow amounts. The air holds less moisture the colder it gets - so when it is very cold we usually don't see much in the way of snow - and in extremely cold weather the snow is more like little snow or ice crystals. Air always holds some moisture regardless of temperature, and the fact that snow piles up in very cold Arctic regions year after year shows that it is never really "too cold to snow".
Johnny asks: What is the deal with a thunderstorms producing snow?
Jennifer Zeppelin: We typically think of thunderstorms occurring during the spring and summer but they can develop in the winter too. This type of storm is known as thundersnow. Winter thunderstorms are considered rare however Colorado can experience this kind of weather phenomenon more often because of the mountains. When a strong upward motion or lift occurs and you add a cold air mass thundersnow can develop. When you hear the thunder you can expect a strong burst of snow sometimes storms like this can produce 1" in less than an hour.
