The Climatological Factors That Shape Rainfall Patterns in the Upstate. Hope Mizzell SC State Climatologist. November 2 Watershed Leaders Forum 1

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1 The Climatological Factors That Shape Rainfall Patterns in the Upstate Hope Mizzell SC State Climatologist November 2 Watershed Leaders Forum 1

2 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

3 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

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5 8 Monthly Total Precipitation (inches) ( ) Precip Charleston Columbia Florence Greenville-Spart. Caesars Head 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

6 South Carolina Monthly and Annual Precipitation Extremes MONTH AMOUNT ( ) YEAR STATION January Caesars Head Februay Caesars Head March Caesars Head April Charleston May Long Creek June Charleston July Kingstree August Long Creek September Marion October Hilton Head Island November Caesars Head December Caesars Head Annual Total Hogback Mountain

7 South Carolina Maximum 24-Hour Precipitation MONTH AMOUNT ( ) YEAR STATION January Caesars Head Februay Bamberg March Blair 1 NE April Aiken May Yemassee June Georgetown July Effingham August Antreville September Myrtle Beach October St. Matthews November Edisto Island December Darlington #2

8 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."

9 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, 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 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 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.

10 The Great Pacolet Flood 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)

11 Number of Reported Flood Events: # of Reported Flood Events *Data from NCDC Storm Events Database 16 N

12 Seasonal Distribution of Reported Flooding Events: Fall 21 Winter 89 Spring 104 Tropical 154 Summer 221 Total 589

13 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

14 Radar is an important nowcasting tool for recognizing flooding potential.

15 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)

16 2004 Debris-Flow Landslide

17 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.

18 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

19 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.

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25 Record Season of 2005 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 2005 Hurricane Season Maximum 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

26 SST anomalies Main Development Region

27 ACTIVE INACTIVE ACTIVE INACTIVE ACTIVE?

28 South Carolina Statewide Average Annual Temperature Temperature (F) Ann Tmp Normal Linear (Ann Tmp) Poly. (Ann Tmp)

29 South Carolina Statewide Average Annual Precipitation Precipitation (inches) Ann. Pcp. Normal Linear (Ann. Pcp.) Poly. (Ann. Pcp.)

30 Recontructed Palmer Drought Severity Index Based on Tree-Rings PDSI NOAA Paleoclimatology Program Dr. Edward Cook, Dr. David Meko, Dr. David Stahle Dr. Malcolm Cleaveland

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33 *SC Flood Mitigation Program

34 The Climatological Factors That Shape Rainfall Patterns in the Upstate Hope Mizzell SC State Climatologist