News - Blogs - The radar image might be deceiving you

The radar image might be deceiving you
Published: 7/22/2011 7:00 AM
Last Modified: 7/25/2011 9:52 AM

The Tulsa National Weather Service radar (which can be viewed at tulsaworld.com/weather) is not showing rain in this screenshot from Thursday afternoon. I'm sorry.

I hate to be the bearer of bad news, but you have the right to know, especially with the entire state hoping and praying for rain:

That's likely not rain that you see on the Tulsa National Weather Service radar.

Upon seeing light blue and light green images on the local radar once again, just as many times before, I just had to ask Tulsa NWS meteorologist Karen Hatfield:

"You're looking at either ground clutter or the returns you get from the radar because of 'thermals' and density differences," Hatfield explained.

The radar's equations converting radar energy to reflectivity assumed that it was liquid water. In turn, I assumed that the radar was showing liquid water too.

"However, not everything that the radar intercepts is liquid water; it intercepts bugs, birds, buildings, chaff, etc.," Hatfield continued. "The density differences that I referred to and the 'thermals' on a really hot day are seen by the radar through the same concept that fronts and outflow boundaries are seen by the radar.

"When the radar energy passes from air with one density into air with another density, it causes the energy in the radar beam to change how it is transmitted through that air. That causes a 'line' of radar echo to show up."

But wait, I thought, holding out remote hope. This "ground clutter" doesn't cover the entire radar area. Surely it's picking up some form of precipitation. Please? Pretty please?

Nope, Hatfield said. More thermals.

"Those typically occur in the lower levels of the atmosphere, and because the earth curves away from the radar, the radar beam gains in elevation the farther you get from the radar site," Hatfield wrote. "Eventually, the beam gets high enough above the ground that it cannot see the lower level thermals and resultant density differences in the air.

"Except in areas with very rough terrain (mountainous areas), this will occur at the same distance from the radar no matter which direction from the radar you're talking about."

If you look closely, you can apparently see the reflectivity over and downwind from the major lakes, because the lake water is cooler than the surrounding land and vegetation, according to Hatfield.

So, I am a sucker for the radar's little thermal teasing, fooling me into believing that maybe some of those hurricanes (read more on this Jerry's entry here) had moved really fast and brought rain to Oklahoma early, or something.

But, Hatfield admitted that the weather equipment has been playing games with meteorologists lately too.

"No really good sign that the pattern will significantly change anytime soon," Hatfield wrote. "The models have teased us every so often with cold fronts a week or more out, but they usually disappear on the next model run."

--Althea Peterson

PS: The last time Tulsa had highs in the 90s and precipitation was July 13. That makes eight days in a row of both triple-digit heat and no rain as of Thursday.

Reader Comments

Show: Newest First

Learn About Our Comment Policy

To post comments on tulsaworld.com, you must be an active Tulsa World print or digital subscriber and signed into your account.

To sign in to your account, go to tulsaworld.com/signin.
To activate your print subscription for unlimited digital access and to post comments, go to tulsaworld.com/activate.
To purchase a subscription, go to tulsaworld.com/subscribe.

Almanac

Jan	Feb	Mar	Apr	May	Jun
Jul	Aug	Sep	Oct	Nov	Dec

	Temperature		Precipitation
Date	High Temp	Low Temp	Total	Month to date	Historical average
1	44°	16°	0	0.00	0.05
2	59°	24°	0	0.00	0.11
3	57°	33°	0	0.00	0.16
4	68°	37°	Trace	0.00	0.21
5	69°	29°	0	0.00	0.26
6	66°	33°	0	0.00	0.32
7	59°	38°	0.05	0.05	0.38
8	51°	34°	0	0.05	0.44
9	44°	36°	0.01	0.06	0.51
10	62°	37°	0.07	0.13	0.57
11	54°	28°	0	0.13	0.64
12	44°	30°	0.25	0.38	0.70
13	55°	40°	0.01	0.39	0.76
14	°	°			0.83
15	°	°			0.89
16	°	°			0.95
17	°	°			1.02
18	°	°			1.09
19	°	°			1.16
20	°	°			1.23
21	°	°			1.31
22	°	°			1.38
23	°	°			1.46
24	°	°			1.53
25	°	°			1.61
26	°	°			1.69
27	°	°			1.77
28	°	°			1.85

TEMPERATURE

RAINFALL

SNOWFALL

Weather World

Follow Jerry Wofford on Twitter for updates during severe weather conditions.

Tulsa weather milestones of 2013 (as of Feb. 12)

Highest temperature: 70 on Jan. 11 (Record: 115 on Aug. 15, 1936)
Lowest temperature: 15 on Jan. 16 (Record: Minus-16 on Jan. 22, 1930)
Hottest month (average): 40.5 degrees in January (Record: 91.7 degrees on July 1980)
Coldest month (average): 40. 5 degrees in January (Record: 21.7 in January 1918)
Most snowfall (day): 0.1 of an inch on Feb. 12(Record: 13.2 inches on Feb. 1, 2011)
Most snowfall (month): 0.1 of an inch in February(Record: 22.5 inches in February 2011)
Most rainfall (day): 0.91 of an inch on Jan. 29 (Record: 9.27 inches on May 26-27, 1984)
Most rainfall (month): 1.54 of an inch in January (Record: 18.18 inches on September 1971)
Highest wind speed: 30 mph on Jan. 30
Previous day with any rain: Feb. 12
Previous day with 1 inch or more of rain: Oct. 17, 2012
Previous day with any snow: Feb. 12
Previous day with freezing temperatures: Feb. 12
Read regular updates on Oklahoma's unpredictable weather and learn more about meteorology from the Tulsa office of the National Weather Service.

>> Visit the main weather page
>> Send us your weather photos
>> Meet the forecasters

Contributors
Staff Writer Althea Peterson started writing for the Tulsa World in March 2007 after previous stops at the Norman Transcript in 2006 and the Oklahoma Gazette in 2005. She followed her older brother from rural Wisconsin (with a public school that never seemed to call snow days) to the University of Oklahoma, but did not follow his pursuit to study meteorology. However, she tries to find as many opportunities to report on the weather as possible.

Staff Writer Jerry Wofford came to the Tulsa World in 2010 from The Manhattan Mercury in Manhattan, Kan. Originally from western Arkansas and a graduate of the University of Oklahoma, Jerry has lived in Tornado Alley his entire life and is one of those people who goes outside when the sirens go off.

Subscribe to this blog

Temperature
High Temp:	(Example: 45)
Low Temp:	(Example: 45)
Temperature Date:	(Example: 1/1/2011)

Precipitation
Total:	(Example: '.01)
Month to date:	(Example: '.01)
Normal month to date:	(Example: '.01)

2/2013	1/2013	12/2012	11/2012	10/2012	9/2012
8/2012	7/2012	6/2012	5/2012	4/2012	3/2012
2/2012	1/2012	12/2011	11/2011	10/2011	9/2011
8/2011	7/2011	6/2011

Your bookmark will appear on your Profile page. Please give it a title, and short description so that visitors to your page will understand where the bookmark leads.
Bookmark Title :

Bookmark Text :