Columbia's Extreme Rain Event

A complex of heavy thunderstorms formed over the Columbia, SC area last Sunday, July 21, 2012.  The heavy rains resulted in what is known as an extreme rain event.  That means that rainfall for the day had to equal or exceed 2.52 inches to be in the top 1% (99^th percentile) based on the current climate statistics.  The official total at the National Weather Service Forecast Office was 2.55 inches, thus an extreme rainfall day.

The slow moving thunderstorms unleashed a torrent of rain producing two to five inches of rain in a couple of hours.  The highest rainfall totals stretched from Lexington to Forest Acres on the east side of Columbia.  Reports of 4.89 inches came in from west of Lexington, 4.56 inches from West Columbia, and 3.48 inches from Forest Acres.

As one can imagine with all of the rain this summer the heavy rains led to flooding.  All of the usual spots flooded, but there were areas not prone to seeing so much water.  Flooding was reported in parts of Forest Acres.  Rain was so heavy in West Columbia that motorists on I-26 had to slow down and pull over in some cases.

A graph of the water levels for Rocky Branch Creek for July 17-24, 2013.  Note that a previous flood occurred on the 17th with bigger flood on the 24th.  Click on the image for a larger view.  Image Credit: USGS.

  

Water rushed into Rocky Branch Creek that flows through the Five Points Area.  By the time it reached Whaley Street it was the third highest flood on record.  The water level reached 11.46 feet, whereas flood stage is at 7.2 feet.  Roads were closed and cars were flooded.

A Drought Worth Having

Droughts can be quite nasty with it comes to rainfall.  However, droughts can be a good thing when it comes to severe weather.  The U.S. is currently experiencing such a drought for tornadoes.

The monthly number of tornadoes for 2013 compared to the 1981-2010 average. Click on the image for a larger version.  Image Credit: Climate Central.

The year started off looking above normal, but that quickly turned in February.  Significantly fewer tornadoes were observed in March and April.  May is normally the peak of tornado season for much of the country.  The drought has continued and will likely continue into the middle of May.  It is hard to say if it will continue beyond that, but it is likely.

Weather Advances Do Not Happen Overnight

Dusan Zrnic. Image Credit: NSSL.

This is a repost of a story written by Bob Henson, who works at the National Center for Atmospheric Research (NCAR).  The original story can be found here and it has information about other advances in radar technology.  What is posted here is an excerpt of the history of dual-polarization with permission from the author.

By Bob Henson

The path to polarization

After years of development, the concept of polarizing radar signals for meteorology took root in the fertile soil of Canada’s Prairie provinces. NSSL’s Richard Doviak and Dusan Zrnić traveled to Alberta in 1979 to check out a circularly polarized radar pioneered by McGill University. “Dick had been interested in doing polarization research as early as 1971, but NSSL was deeply immersed in Doppler work at the time,” recalls Zrnić.

Once the lab decided to build its own polarized radar, it went for a dual-pol approach, with signals oriented in the horizontal or vertical rather than circularly. “We made this choice for good reason,” says Zrnić. Research by Thomas Seliga and Viswanathan Bringi, then both at Ohio State University, had shown how signals from the two orientations might yield critical data on the character of precipitation.

This hypothesis was confirmed through measurements in a 1977 Oklahoma field project using the CHILL dual-pol radar under the leadership of Gene Mueller. Now based at CSU, CHILL—the first university-based dual-pol radar—was named after Chicago, Illinois, where it was launched by the University of Chicago and the Illinois State Water Survey. NCAR was another dual-pol pioneer, converting its CP-2 radar and creating the first real-time displays of differential reflectivity (relating horizontal to vertical returns).

Starting in the mid-1980s, Zrnić teamed with postdoctoral fellows Mangalore Sachidananda (now at the Indian Institute of Technology) and Narasimha Balakrishnan (now at the Indian Institute of Science) to work out the details of distinguishing rain from hail and other hydrometeors using dual-pol data, with contributions from Jerry Straka (University of Oklahoma). By 1996, Zrnić had written a paper for the Bulletin of the American Meteorological Society pondering the eventual role of dual-pol in operational settings.

Pigs Can't Fly, But Mobile Homes Can

This is a repost of a blog I did 4 years ago.  It is as important today as it was then and maybe more so.

Daniel Bonds is working on his master's degree and his thesis work involves mobile home parks and tornado safety.  His preliminary work shows that most do not have a safe place to go in the event of a tornado here in the Midlands.

Furthermore, many living in such places do not know the different between a tornado and a hurricane.  They believe that they can simply evacuate to the local school or some other shelter when a tornado approaches which is a mistake.  Experience and the science has confirmed that in a tornado situation a mobile home must be abandon even if it is tied down.  The risk of being killed in a mobile home is significantly higher than in a traditionally built home.

Mobile home lifted off its blocks (foreground) with what is left of the home up against the trees along with an overturned vehicle.  Image Credit: NOAA.