Feb 9-11 1973 SC Superstorm Study



Updated 5/23/05

Overview of the Storm


This was a very interesting storm, as it brought the highest snowfall on record to portions of Georgia and South Carolina, and brought snow to some places that do not regularly see snow. The heaviest snow fall focused across central portions of South Carolina, Georgia, and south-central Alabama. It brought snowfall to locations in Florida and heavy snow and blizzard conditions to eastern NC as well. But the main focus of the storm's fury was definitely central Georgia and South Carolina. Below is a snowfall accumulation map for Georgia and South Carolina courtesy of Augustaweather.com

Snowfall in Georgia and South Carolina


Below is a table with selected snow accumulations for part of the south. These data were gathered from NCDC.

Snowfall for some SE cities
City, State Snow (inches) City, State Snow (inches) City, State Snow (inches) City, State Snow (inches) City, State Snow (inches)
Whiteville, NC 16.5 Rimini, SC 24 Thomaston, GA 19.3 Hattiesburg, MS 2.5 Union Springs, AL 13
Morehead City, NC 16.5 Bamberg, SC 22 Butler, GA 18.5 Leakesville, MS 2 Clayton, AL 12
Hamlet, NC 14 Manning, SC 21 Macon, GA 16

Louisville, Al 10
New Bern, NC 13 Lake City, SC 17.5 Augusta, GA 14 Milton Exp Stn, FL 3.3 Abbeville, AL 10
Wilmington, NC 12.5 Florence, SC 17 Columbus, GA 14 Quincy, FL 2 Opelika, AL 8.6
Elizabeth City, NC 12 Columbia, SC 16 Forsyth, GA 10 De Funiak Springs, FL 2 Eufuala Wildlife Refuge, AL 8
Lauringburg, NC 11 Summerville, SC 15 Americus, GA 8 Pensacola, FL 1.9 Wallace, AL 8
Lumberton, NC 10.2 McColl, SC 15 Savannah, GA 3.2 Jasper, FL 1 Brewton, AL 6
Goldsboro, NC 10 Aiken, SC 15 Albany, GA 3 Fountain, FL 1 Headland, AL 4
Wadesboro, NC 9 Kingstree, SC 13 Athens, GA 1.7 Niceville, FL 1 Claiborne, AL 4
Fayetteville, NC 8 Conway, SC 12

Monticello, FL 0.5 Mobile Airport, AL 3.6
Pinehurst, NC 8 Murrels Inlet, SC 9.5 Beaumont, TX 3 Panama City, FL 0.5 Montgomery, AL 3.1
Clinton, NC 8 Charleston, SC 7.1 San Antonio, TX 2.1 Tallahassee, FL 0.4 Frisco City, AL 3
Kinston, NC 7.9 Beaufort, SC 6 Houstn, TX 1.4
 Fernandina Beach, FL 0.1 Coden, AL 2.5
Edenton, NC 7.5 Rock Hill, SC 4 Victoria, TX
 1

Geneva, AL 2
Smithfield, NC 7 Hilton Head, SC 2 Austin, TX
 0.9

Lafayette, AL 2
Cedar Island, NC 6.5







Southport, NC 6

Lafayette, LA
 2



Greenville, NC 6

Baton Rouge, LA
 1.8



Monroe, NC 5

New Orleans, LA
 0.6



Fort Bragg, NC 5







Rocky Mount, NC 5







Raleigh, NC 4.5







Albemarle, NC 4.5







Cape Hatteras, NC 3.3







Durham, NC 3







Charlotte, NC 1









For starters, here are the NOAA Central Library maps.
2/9/73 2/10/73
Now for the following discussions, keep in mind that NARR data which is 32km reanalysis data was not available for this year. So I had to use the more coarse NCEP reanalysis data which has a horizontal resolution of 2.5 degrees longitude. First we will take a look at the NH 500mb pattern from Feb 5th to Feb 10th. As you see here, and will see later in the 250mb winds, there is a very active subtropical jet associated with a split flow pattern in the eastern Pacific. Notice the closed 500mb positive anomaly, (block), over the Alaska/Yukon border near Dawson. You can see the jet stream splits around 165W, with a strong northern branch and a noticeable southern branch coming into the southwest US. Also notice that as of the 5th, the strongest PV in the hemisphere is just on the other side of the North Pole. Thru time, the block progresses into British Columbia while the strong PV begins to move to this side of the pole as a deep cold trough carves out across eastern Canada and the NE US. Notice the flow on the 500mb map is from Siberia into Hudson Bay, which provided plenty of available cold air for the storm to tap into.
2/5/73 12z 2/6/73 12z 2/7/73 12z 2/8/73 12z
2/9/73 12z 2/10/73 12z

Below are the 500mb Absolute Vorticity vs Height maps for Feb 5th thru 11th. You can follow the main s/w (white line) as it moves in from the southern branch of the jet onshore into Baja California by the 8th then into the southern plains by the 9th. The s/w trough deepens slightly across the SE US, but never closes off or becomes significantly negatively tilted. Notice also the strong trough moving thru the Great Lakes and NE US as it lower heights dramatically across the southeast US just ahead of the southern stream system. The timing of these s/w's along with their associated jet structures, (which will be discussed later), were perfect for a heavy winter event across the SE states.
2/5/73 12z 2/6/73 12z 2/7/73 12z 2/8/73 12z
2/9/73 12z 2/10/73 00z 2/10/73 06z 2/10/73 12z
2/10/73 18z 2/11/73 00z 2/11/73 12z

Below are maps with 850mb Temperature, surface pressure, and my drawings of surface features, no laughing please. As you can see, at 00z on the 6th, an arctic air mass with an estimated 1039mb surface high is moving into the northern plains. Keep in mind the coarse nature of the data means that the surface high was probably stronger. You can see from the progression of images that the core of the coldest air stays up in southeast Canada but a formidable chunk sinks pretty far to the south, as the front drops into the Gulf and just off the Carolina coast. Then we see the classic recipe take place for a southern storm. With the arctic front draped across the gulf, the southern stream s/w, recall above, begins to advect higher vorticity across this baroclinic zone on the 9th, and thus upward motion commences and pressures begin to fall as a surface low forms in the gulf early on the 9th. This is the classic route to a major southern winter storm. The surface low develops pretty far south and east, hence the more eastern and southern displacement to the snow area. The low moves ENE across central Florida and parallels the southeast coast as it moves NE on the 10th, and then eventually moves ENE out to sea. Notice how far south the 850 0 line is during the storm.
2/6/73 00z 2/7/73 00z 2/8/73 00z 2/8/73 12z
2/8/73 18z 2/9/73 00z 2/9/73 06z 2/9/73 12z
2/9/73 18z 2/10/73 00z 2/10/73 06z 2/10/73 12z
2/10/73 18z 2/11/73 00z 2/11/73 06z

Below are maps of the southeast US with surface pressure, surface temperature, and surface winds beginning at 6z on the 9th. Notice the surface freezing line gets all the way down to the immediate coastal areas of the Gulf region and Carolina coastal regions. And again keep in mind that this coarse data is underestimating the actual temperatures, as for most of the storm the immediate coastal areas of the Carolinas were right at or below freezing. Also notice the tight pressure gradient along the southeast coast, where the winds are 30 to 40kt, which produced blizzard conditions across the Carolina coastal regions.
2/9/73 06z 2/9/73 12z 2/9/73 18z 2/10/73 00z
2/10/73 06z 2/10/73 12z 2/10/73 18z 2/11/73 00z
2/11/73 06z

Below are the surface observations for RDU during the time of precipitation.
Storm Observations for RDU for Feb 10th
Time Weather Temp (F) Winds Visibility
4am Light Snow 27 NE 14kt 7 miles
5am Light Snow 28 NE 17kt 1.5 miles
6am Light Snow 25 NE 14kt 1 mile
7am Moderate Snow 23 NE 14kt 0.5 miles
8am Moderate Snow 23 NNE 14kt 0.5 miles
9am Light Snow 23 NE 17kt 0.3 miles
10am Heavy Snow 22 NNE 18kt 0.1 miles
11am Heavy Snow 22 N 13kt 0.12 miles
Noon Light Snow 22 N 24kt 0.5 miles
1pm Light Snow 22 N 17kt 1 miles


Now I will look at two factors I see that lead to the enhanced snowfall over the central Alabama, Georgia, SC, eastern NC corridor. First let's look at the 250mb winds from 00z on the 9th to 12z on the 10th. Now there are two things to notice on these maps, the two jet axes. I have drawn in a white arrow to highlight the two distinct and in my opinion separate jet cores. The one over the NE US is associated with the northern branch of the jet, and jet axis over the southern US is associated with the southern branch. Now for a short intro into jet streak dynamics please review this link. Straight Jets
So favorable regions for upper level divergence and hence upward motion are the right rear entrance region and the left front exit region. Now notice on the 250mb maps that the areas in the white circles are regions located in the right rear entrance region of the polar jet streak, and in the left front exit region of the southern stream jet streak. This is a region of enhanced ascent, and locally heavier precip. This can be seen by the accompanying 250mb divergence maps which show divergence in those regions.

250mb Winds

2/9/73 00z 2/9/73 06z 2/9/73 12z 2/9/73 18z
2/10/73 00z 2/10/73 06z 2/10/73 12z


250mb Divergence
2/9/73 12z 2/9/73 18z 2/10/73 00z 2/10/73 06z
2/10/73 12z 2/10/73 18z


Next lets look at the 850mb maps. These maps show that an 850mb low develops across the Florida panhandle on the evening of the 9th, and then traverses just offshore of the Georgia and SC coastal regions. The enhanced convergence north of this 850mb low also was part of the heavy snow equation in those regions.

2/9/73 12z 2/10/73 00z 2/10/73 06z 2/10/73 12z
2/10/73 18z 2/11/73 00z 2/11/73 06z

So in summary, this storm was a major snowstorm for many parts of the southeast. It left snow from Mississippi to NC with some all time record snows for some parts of the area. The area that saw the best snows was an area that lied in an area of strong upper level divergence created by a favorable location in relation to the jet structure, and also in the area just north of the 850mb low, where low level convergence was maximized.