By ALTHEA PETERSON Staff Writer on Jan 9, 2013, at 12:53 PM Updated on 1/09 at 12:58 PM
WEATHER WORLD
It's not a Tulsa urban legend, myth or a running joke: It really does rain every year (since 2008) at downtown's Mayfest.
And ...
There is a lot to digest on the drought front, so I'll try to cover as much ground as I can.
Before showing this week's ...
Bad news this week, Oklahoma: Your drought situation was either unchanged or got worse.
If this comes as a surprise, ...
In this Jan. 12, 2012 file photo, Janet Kellogg scrapes snow and ice from her car window. MIKE SIMONS/Tulsa World File
In this Jan. 12, 2012 file photo, snow covers a group of taxicabs near Sixth Street and Peoria Avenue in Tulsa. MATT BARNARD/Tulsa World File
Elisha Green, of Tulsa, but who grew up in Chicago, clears snow from her windshield, near Country Club Drive and West Edison Street, amidst cold and snowy conditions in Owen Park, on Feb. 13, 2012. "Look at the streets. They are clear," she said. "I don't know why they cancelled school today. This wouldn't happen in Chicago." CORY YOUNG/Tulsa World File
In this Feb. 11, 2011 file photo, Larry Smith, lead jailer at the Delaware County Sheriff's Office, in Jay, shovels vehicles out from two snow storms that left approximately 50 inches of snow over a two week period in the area. CORY YOUNG/Tulsa World File
will never be a Christmas carol. However, for many of the days in the past week before our recent uptick in temperatures, I found myself getting out the ice scraper before the morning commute.
What causes this? A Q&A with Tulsa National Weather Service meteorologist Karen Hatfield:
Q: What weather conditions are necessary for windshield ice/frost?Hatfield: Windshield ice can come in two forms, the most common being "normal" frost and the other coming from freezing rain or drizzle.
Frost forms at night when the relative humidity is high, winds are light or calm, and the temperature of a surface is below the frost point.
The most typical scenario is when surface high pressure is overhead, providing lighter winds and usually, clear skies.
Windshield frost can form in this manner. It can also form via the same concepts but in a little more unique fashion. When the outside of the windshield gets cold, but the interior of the vehicle is relatively moist (from your breath, etc.), the water vapor can condense and freeze on the outside of the window. Think about what happens if you get
in the car when it's very cold and begin to drive before letting the
vehicle heat up; your breath fogs up the window. It's that concept.Q: What causes some sides of a vehicle to be free of ice/frost, and other sides not? The west side of my car this morning was ice-free, the east side had light ice.Hatfield: As far as your vehicle goes, something as simple as one side of the vehicle being exposed and others closer to a building (likely providing warmer air) could affect it. The wind direction (even if the wind was light) could affect it, as well.Q: Why do vehicles parked inside garages not get ice/frost, even if it's just as cold outside as it is inside the garage? Do carports prevent ice/frost also?Hatfield: Any kind of covering (i.e. - parking garage, carport) keeps radiation frost from forming because heat is trapped closer to the ground (even if it doesn't feel like it). The roof over the vehicle will also keep ice
crystals from depositing on the vehicle, causing windshield frost.Q: Are there any materials/products that will prevent windshield ice/frost, besides garage parking?Hatfield: When I lived in Minnesota, I had a physical covering for the windshield that would collect any frost rather than it depositing on the windshield.
All I had to do was remove the cover when I wanted to drive. There are other things like de-icers that will remove the frost easily.Althought it was unrelated to windshields, I also noticed my breath in the air late last night, so a follow-up question:
Q: In what weather conditions can you see your breath in the air, almost making it look like you're smoking?Hatfield: Usually, it's when temperatures are colder because the air can hold less water vapor at colder temperatures. Therefore, the moisture in your breath can saturate easier at lower temperatures.Tulsa is forecast to nearly hit 70 in a few days, but will likely be back to the 20s for overnight lows by the weekend. You can check Tulsa's latest forecast information, courtesy of the National Weather Service, at
tulsaworld.com/weather.
--Althea Peterson
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