Sunday, July 1, 2012

An Unprecedented Heat Wave

Image Credit: WLTX-TV.
Columbia, South Carolina markets itself as being “Famously Hot” and this weekend it lived up to that billing in ways never imagined.  The heat wave that hit the area was unprecedented in speed and intensity.  Fortunately everyone knew it was coming, but it was still under forecast.

It took only one day to be in the heat wave.  The high temperature on Wednesday was 89 F, but it reached 100 F on Thursday, the start of the heat wave.  However, the peak of the heat wave intensity was on Friday when the temperature soared to an all-time record high of 109 F at the Columbia Metropolitan Airport and 110 F at Hamilton-Owens Field, just south of downtown Columbia.  The temperature at the airport had never been above 107 F.

High temperatures for Friday, June 29, 2012, in South Carolina.  Image Credit: WLTX-TV.

In addition, it was not until Saturday when the co-op reports came into the National Weather Service that it was discovered that the all-time record high for the state of South Carolina was broken.  The previous all-time high was 111 F set at Calhoun Falls and Blackville in 1925 and in Camden in 1954.  It reached 113 F in Johnston and the campus of the University of South Carolina in Columbia, Friday afternoon.  This still has to be confirmed by the state climatology office, but it is very likely that one or both will stand as the new all-time record high for the state of South Carolina.

Here is a listing of the high temperatures Friday from the National Weather Service Forecast Office in Columbia, South Carolina:



AUGUSTA BUSH APT  GA              106
AUGUSTA DANIEL APT GA             107
COLUMBIA METRO APT SC             109
COLUMBIA OWENS APT SC             110


BAMBERG SC                        106
BARNWELL SC                       105
BATESBURG SC                      106
BISHOPVILLE SC                    106
CEDAR CREEK SC                    107
CHERAW WATER PLANT SC             104
CHESTERFIELD SC                   107
JOHNSTON SC                       113
LITTLE MOUNTAIN SC                107
LONGTOWN SC                       102
LUGOFF SC                         105
MANNING SC                        100
MCCORMICK SC                      108
NEWBERRY SC                       104
PELION SC                         104
USC, COLUMBIA SC                  113 
WIER TOWER, FORT JACKSON SC       108            


CAROLINA SANDHILL SC              106
JACKSON SC                        105

Why did the heat wave hit so fast and with such intensity?

The 500 mb heights for 18z Friday, June 29, 2012.  This comes from the GFS Operational model.  Note the height centers over the Southwest and the Tennessee River Valley.  This helped produce triple digit temperatures from the Southwest to he East coast.  Image Credit: WSI.

A large high pressure center that had been stationary over the central U.S. split in two with one center retrograding to the Southwest and the other moving to be centered over the Southeast.  The southeastern center was over the Tennessee River Valley by Friday afternoon.  As was mentioned in the previous blog post this is usually an ideal pattern for extreme heat in South Carolina during the summer.  This creates subsidence of the air mass and downslope slope flows from the Appalachians as winds aloft are from the northwest.

It was apparent to any meteorologist on Friday what was going on.  I drove to Irmo that morning and other than the fire in Cayce there was not a cloud in the sky.  This made me quite concerned about the day ahead while most others were focused on the blaze at a recycling plant (with good reason).

I knew that the day before the sky was cloudless as a thermal cap had formed from the subsidence.  The noontime temperature was 90 F with the eventual high reaching 100 F.  The same thing was happening on Friday, but now temperatures at the 850 mb level were higher (26 – 27C).  In the previous blog post I mentioned that a temperature of 27 C relates to a potential surface temperature of 110 F.  When the noontime temperature of 100 F occurred on Friday, I knew the all-time record high temperature for Columbia would be broken.  It was just a matter of when and that occurred at 3 p.m. with a temperature of 108 degrees F.

Friday night the heat wave was changed by an extraordinary event to our north.  A line of thunderstorms formed in Indiana and raced to the east coast passing through the Washington, DC, area.  The line produced considerable damage from the high winds.  The southern end of the line sent debris clouds south into South Carolina for Saturday morning.  My first thought was that the temperature would have a hard time reaching my forecast of 107 F due to the reduced solar insolation of the morning.  It was hot enough during the WLTX e-cycle event at the State Fairgrounds (a huge success in spite of the heat).  However, the skies clear in the early afternoon and the temperature soared to 109 F for the second day in a row at the Columbia Metropolitan Airport.  This tied the all-time record high set the previous day and was an event that had never happened in the 125 years of record keeping once a climatological set of temperatures had been established.  In addition, the humidity was higher and heat indices were in the range of 110 to 115 F.

The heat wave continued to change into Sunday.  Dew point temperatures soared into the upper 70s and the low in Columbia was 80 F.  By 1 p.m. the temperature at Hamilton-Owens Field was just 99 F, but with a dew point temperature of 77 F the heat index was 114 F.  The heat was stiffing and would become excessive in the afternoon.

Again, the heat wave was unprecedented in the speed in which it arrived and the speed with which the character changed.  It was also unprecedented in magnitude.

A meteorologist stated that if it were not for global warming we would not be seeing this.  He is right in that this is consistent with the projection scientist have made using the computer models.  I presented the findings for our area again Thursday night in a segment of Climate Matters and will have a post on extreme heat soon.