The Climatological Factors That Shape
Rainfall Patterns in the Upstate
Hope Mizzell
SC State Climatologist
November 2
Watershed Leaders Forum 1
SC State Climatology Office
• Represent the State in all climatological and
meteorological matters
• Archive, process, and disseminate climate and
weather information
– 150 Weather Stations
– 1899 Oldest Record
• Prepare and disseminate regular climatic
information (Publications, Web pages)
• Conduct research
– Hurricane Climatology
– Drought Monitoring
• Service (15 calls daily, 20,000 web retrievals)
– Lawyers, Insurance, Construction, Agriculture, State
Agencies, Educators, Researchers, Forestry
South Carolina Precipitation Distribution
Varies geographically, seasonally, and annually
Heaviest rainfall occurs in northwest higher elevations
Least amounts fall in the central part of the state
Mountains
70 to 80 inches at highest elevations
Highest annual total at Caesars Head
(79.29")
Foothills
60 to more than 70 inches
Eastern and southern Piedmont
45 to 50 inches
Midlands
42 to 47 inches
Coastal Plain
50 to 52 inches
Secondary statewide maximum occurs parallel to coast and about 10 to
20 miles inland. Maxima is a result of sea-breeze front thunderstorms
prevalent during summer
Monthly Total Precipitation (inches)
(1971-2000)
8
7
Precip.
6
Charleston
Columbia
Florence
5
4
Greenville-Spart.
Caesars Head
3
2
1
0
Jan Feb
Mar
Apr
May Jun
Jul
Aug Sep
Oct
Nov Dec
South Carolina Monthly and Annual Precipitation Extremes
1890-2004
MONTH
January
Februay
March
April
May
June
July
August
September
October
November
December
AMOUNT (”)
17.32
15.58
17.77
15.00
17.65
27.24
31.13
22.49
27.06
25.81
17.85
20.00
YEAR
1946
1938
1975
1977
1976
1976
1916
1940
1928
1994
1948
1932
STATION
Caesars Head
Caesars Head
Caesars Head
Charleston
Long Creek
Charleston
Kingstree
Long Creek
Marion
Hilton Head Island
Caesars Head
Caesars Head
Annual Total
120.21
1979
Hogback Mountain
South Carolina Maximum 24-Hour Precipitation
1890-2004
MONTH
AMOUNT (”)
YEAR
STATION
January
5.15
1926
Caesars Head
Februay
6.50
1973
Bamberg
March
9.50
1977
Blair 1 NE
April
9.68
1969
Aiken
May
7.25
1969
Yemassee
June
10.50
1945
Georgetown
July
13.25
1916
Effingham
August
17.00
1995
Antreville
September
14.80
1999
Myrtle Beach
October
12.30
1990
St. Matthews
November
11.64
1969
Edisto Island
December
7.70
1994
Darlington #2
South Carolina Floods
Several variations of flood hazards occur due to the different effects of
Severe thunderstorms
Hurricanes
Seasonal rains
Other weather-related conditions
State's topography combined with its humid subtropical climate,
makes it highly vulnerable to inland or riverine flooding.
Riverine Floods is a high flow or overflow of water from a river or similar body
of water, occurring over a period of time too long to be considered a flash flood.
Riverine flooding occurs when the flow of rainwater runoff is greater than the carrying
capacities of the natural drainage systems.
Flash Floods are quick-rising floods usually occurring as the result of heavy
rains over a short period of time, often only several hours or even less.
Coastal Flooding occurs when strong onshore winds push water from an
ocean, bay or inlet onto land. This can take the form of storm surges
associated with tropical storms and hurricanes, or can be associated with nontropical storms such as “coastal gales."
South Carolina Notable Floods
June 1903 the highest number of people killed in floods in SC, on the Pacolet River, a tributary of
the Broad River, when 60 to 80 people drowned in a flash flood.
August 1908 the most extensive flooding occurred. All the major rivers of the state rose from 9 to
22 feet above flood stage.
October 10-13, and October 22, 1990 - remnants of Hurricane Klaus and Tropical Storm Marco
moving northward along a stationary front. As a result of the flooding, Aiken, Calhoun, Cherokee,
Darlington, Edgefield, Florence, Kershaw, Lee, Orangeburg, Spartanburg, Sumter, and Union
counties were declared federal disaster areas.
August 1995 – During the third week of August 1995 Tropical Storm Jerry moved into SC from
Florida with record rains. Deadly flooding occurred across the upstate. Antreville measured a state
24-hour record 17.00 inches, most of which fell in 8 hours. Dams failed, roadways and bridges
were swept away. Abner Creek in Spartanburg County normally flowing at one foot peaked at 20
feet. The Reedy River at Greenville exceeded 16 feet.
September 16 1999 – Hurricane Floyd Cat 3 made landfall just across our border into NC near
Cape Fear. Winds gusted to 85 mph on the peninsula of Charleston. Between 15 and 20 inches of
rain was measured in Horry County. Street flooding was reported as three feet deep along Ocean
Blvd. The drainage basin within the Waccamaw River received the bulk of tropical rainfall. Not until
Wednesday November 10 would the Waccamaw fall below flood stage. More than 1700 residential
properties along the Waccamaw experienced extensive flood damage.
The Great Pacolet Flood - 1903
The greatest loss of life from river flooding this century in SC occurred along the Pacolet River
near Pacolet during the early morning of June 6th. Strong convergence plus upslope flow of
warm moist air associated with low pressure which tracked across northwestern SC produced
the heavy rain that caused the flooding. Sixty-five people were drowned by the raging flood
waters. According to the NWS Monthly Weather Review, the water rose so rapidly that the
land near the river was covered by 40 feet of water within one hour. Railway traffic was
disrupted. There was complete loss of houses, churches, industrial plants and corn and flour
mills along the river. The textile communities of Clifton and Pacolet were hit the hardest by the
flood, but flood damage also occurred along other streams in northwest SC. The economy
was devastated by The economy was devastated by $5 million (1903 dollars) in damage.
(Source: Clifton: A River of Memories and Herald Journal)
Number of Reported Flood Events: 1993 – 2005
20
31
82
82
33
48
18
23
30
# of Reported Flood Events
0 - 15
16 - 30
31 - 45
46 - 60
61 - 75
76 - 90
*Data from NCDC Storm Events Database
25
35
16
N
Seasonal Distribution of Reported Flooding Events: 1993- 2005
Fall
Winter
Spring
Tropical
Summer
Total
21
89
104
154
221
589
Thunderstorms
Flooding occurs when too much rain falls over a given time period for the ground
surface to support. The flooding potential will be greater when storms move over
previously saturated land or rain falls over land that has a low permeability.
- Flash flood potential from isolated thunderstorms are limited unless it is slow moving
- Squall lines can deposit large quantities of rain over a large area, but unless they are
slow moving there is not a high chance of flash flooding
+ Consistent rain- especially heavy rain falling over an extended period of time
+ Very intense slow moving thunderstorms- a single slow moving thunderstorm can
produce several inches of rainfall per hour
+ Training thunderstorms- thunderstorms developing and moving over the same areas
that previously had thunderstorms
*Source-USA Today
Radar is an important nowcasting tool for recognizing flooding potential.
Orographic Influence
Upslope Flow
Same as Orographic Lifting; air that flows toward higher terrain, and hence
is forced to rise. The added lift often results in widespread low cloudiness
and stratiform precipitation if the air is stable, or an increased chance of
thunderstorm development if the air is unstable.
(*Debris-flow landslide triggered by rain
from Frances and Ivan)
2004 Debris-Flow Landslide
Hurricane Storm Surge
While high winds cause significant structural and environmental damage, storm
surges are frequently the most devastating element of a hurricane.
Storm Surges
The strong winds blowing towards the shore help
push water towards shore on the right side of the
hurricane's direction of motion. This piling up
contributes to most of the coastal flooding.
Hurricane Storm Surge
The mound of water is then influenced by the slope of the coastline as the hurricane
approaches land. If the coastline is shallow, water cannot flow away from the mound and the
mound grows. If the coastline is deep, water can disperse and the mound may grow slowly or
disperse depending on hurricane strength. An example of a shallow-water coastline is the
Gulf Coast while an example of a deep-water coastline is found in New England.
Shallow-water Coastline
Deep-water Coastline
Tropical Induced Rainfall a problem of any tropical disturbance
Heavy rainfall causes both flash and long term flooding.
-Produce as much as 2 feet of rain
-Creating problems for residents who believe they are safe just
because they do not live on or near the coast.
-Flooding kills more people than the strong winds do
Even as a hurricane weakens over land it still produces a lot of rainfall.
Record Season of 2005
2005 Hurricane Season
M aximum
The 2005 Atlantic season was unusually active from the very start,
with development of two Category 4 hurricanes, Dennis and Emily, in
July. Warm ocean surface water in the Gulf of Mexico and weak
tropical winds are two of the primary factors contributing to this
exceptionally harsh season.
23 named storms makes it most active on record.
13 hurricanes exceeds 1969 for record number of hurricanes.
15 landfalling systems (including tropical depressions) sets
new record
First hurricane season, Atlantic or Pacific, to exhaust list of
names and resort to Greek letters for naming.
First hurricane season to see three Category 5 storms Katrina, Rita, and Wilma are among six most intense tropical
cyclones ever to form in Atlantic basin.
Vince was the first tropical cyclone in recorded history to
make landfall in Spain.
Lowest pressures:
1. Wilma (2005): 882 mb
2. Gilbert (1988): 888 mb
3. Hurricane #2 (1935)“Labor Day” 892 mb
4. Rita (2005): 897 mb
5. Allen (1980): 899 mb
6. Katrina (2005): 902 mb
7. Camille (1969): 905 mb
Intensity
Storm Name
Arlene
Bret
Cindy
Dennis
Emily
Franklin
Gert
Harvey
Irene
Jose
Katrina
Lee
Maria
Nate
Ophelia
Philippe
Rita
Stan
Tammy
Vince
Wilma
Alpha
Beta
Main Development Region
SST anomalies
ACTIVE
INACTIVE
ACTIVE
INACTIVE
ACTIVE
?
South Carolina Statewide Average Annual Temperature
1895-2003
66
Temperature (F)
65
64
Ann Tmp
63
Normal
62
61
60
1895 1905 1915 1925 1935 1945 1955 1965 1975 1985 1995
Linear
(Ann Tmp)
Poly. (Ann
Tmp)
South Carolina Statewide Average Annual Precipitation
1895-2003
75
Precipitation (inches)
70
65
60
Ann. Pcp.
55
50
Normal
45
40
35
30
1895 1905 1915 1925 1935 1945 1955 1965 1975 1985 1995
Linear
(Ann.
Pcp.)
Poly.
(Ann.
Pcp.)
Recontructed Palmer Drought Severity Index
Based on Tree-Rings
4
3
1
0
-1
-2
NOAA Paleoclimatology Program
Dr. Edward Cook,
Dr. David Meko,
Dr. David Stahle
Dr. Malcolm Cleaveland
1897
1887
1877
1867
1857
1847
1837
1827
1817
1807
1797
1787
1777
1767
1757
1747
1737
1727
1717
1707
1697
1687
-3
1677
PDSI
2
http://www.dnr.state.sc.us/climate/sco/
*SC Flood Mitigation Program
The Climatological Factors That Shape
Rainfall Patterns in the Upstate
Hope Mizzell
SC State Climatologist