SLIDE 1
Western North Carolina Sets Record in May 2018 for Wettest Month
Ward Seguin George Smith Riverside Technology
SLIDE 2 Meteorological Situation – May 2018
- Large broad-scale/long-wave ridge dominated CONUS
- Two low pressure systems brought above
normal precipitation to the southeast.
- May 15-19
- May 28-30, TS Alberto
(Source: https://www.ncdc.noaa.gov/sotc/synoptic/201805)
SLIDE 3 Asheville, North Carolina
SLIDE 4
SLIDE 5
May 18, 12Z Surface Analysis (Source: https://www.ncdc.noaa.gov/sotc/synoptic/201805)
SLIDE 6 May 18, 12Z 500-mb Heights Source: https://www.ncdc.noaa.gov/sotc/synoptic/201805
SLIDE 7
May 29, 12Z Surface Analysis (showing Tropical Storm Alberto) Source: https://www.ncdc.noaa.gov/sotc/synoptic/201805
SLIDE 8
Subtropical Storm Alberto
(Source: National Hurricane Center Tropical Storm Alberto Report, Oct. 18, 2018)
SLIDE 9 Average May 2018 Precipitation by County
18.9 (10) 7.0 (4) 8.3 (9) 8.7 (3) 15 (1) 12 (4) 18.4 (3) 10.1 (14) 10.4 (1) 11.9 (2) 12.3 (1) (CoCoRaHS Stations with 31 days of observations. Number of stations with 31 days shown in parenthesis.)
SLIDE 10 Source: https://www.weather.gov/gsp/avlcli
Individually, these are not record setting daily events for AVL.
Duration Record Rainfalls Maximum Rainfall (Short wave low pressure system) Maximum Rainfall Alberto One Day 6.40 - Oct. 18,1879 2.92 – May 18 1.77 – May 29 Two Day 7.94 - Oct 24-25, 1918 3.99 – May 17-18 2.93 – May 29-30 Three Day 8.49 - Oct 24-26, 1918 6.78 - May 16-18 3.96 – May 28-30 Four Day 8.51 - Oct 24-27, 1918 Five Day 8.54 – Oct 24-28, 1918 8.21 - May 15-19 http://scacis.rcc-acis.org/
SLIDE 11
SLIDE 12 French Broad River Response
Hydrograph at Blantyre May 8-22, 2018 (Note: Blantyre is 30 miles south of Asheville.)
SLIDE 13 French Broad River Response
Hydrograph at Blantyre May 21 – June 4, 2018
SLIDE 14 Inundation along the French Broad River from Tropical Storm Alberto as Depicted by Riverside’s “RiverTrak” Model
Blantyre Bridge and River Gauge
SLIDE 15 June 1st Flooding
Looking west Blantyre Bridge Looking east toward bridge Parking lot by Bridge Saturated soils from the first storm enabled TS Alberto to cause significant flooding and mud slides.
SLIDE 16 Summary of Impacts
- More than 50 roads across 13 counties were closed at some
point due to flooding and mudslides
- Five people perished
- Extensive agricultural losses
- Thousands without power
- Two thousand residences evacuated below the Tahoma
dam* because of a mud slide and a potential dam failure
- Businesses and residents flooded in Asheville
* - The Tahoma dam is approximately 40 miles northeast of Asheville.
SLIDE 17
County Land Slides Storm Date Polk Over 80* May 18th Rutherford 1 7 May 19, 2018 May 28-30, 2018 (Alberto) McDowell 7 4 May 18-30, 2018 May 30, 2018 (Alberto) Henderson 1 1+ May 19, 2018 June 6, 2018 Watauga 1# May 30, 2018 (Alberto) * -This number includes at least 18 major debris flows and one fatality + - Landslide over NC route #9 # - Landslide damaged propane gas supply to house causing an explosion, 2 fatalities
Land Slides
SLIDE 18 Source: Times-News August 1, 2018
Tryon, NC Mudslide 50 Miles South of Asheville
5-6 Inches of Rain in Three Hours on May 18, 2018
SLIDE 19 Tryon Fatality Debris Flows
Source UAV Image Broad River Fire Dept.
SLIDE 20 Source: Times-News May 20, 2018
U.S. 176 Closed
SLIDE 21
Source: Times-News June 12, 2018
SLIDE 22 Natural Disaster Declared
U.S. Agriculture Secretary Sonny Perdue declared for four North Carolina counties: Buncombe, Henderson, Madison and Transylvania natural disasters.
Crop losses
- Strawberries -60%
- Squash, cucumbers – 50%
- Sod – 40-60%
Fertilizer leeched out
SLIDE 23 Summary
Meteorological situation
- Two slow-moving weather systems including tropical storm Alberto
contributed to a record amount of rainfall in May. Impact
- Five people perished
- More than 50 roads across 13 counties were closed at some point
- One County experienced over 80 landslides
- U.S. Dept. of Agriculture declared four North Carolina counties as
natural disaster areas Observing, forecasting and communicating the event
- NWS forecast and guidance was good
- WFO Greenville provide e-mails to emergency managers during the
first event and held morning briefings for Tropical Storm Alberto
SLIDE 24 Month Rainfall in Inches Year January 9.95 1989 February 9.60 1873 March 9.86 1975 April 8.70 1989 May 14.68 2018 June 10.73 1989 July 13.69 2013 August 13.75 1940 September 13.71 2004 October 11.32 1918 November 7.82 2015 December 9.16 2009
Wettest Months
https://www.weather.gov/media/gsp/Climate/AVL/newAVLwetdrymonths.pdf
Note the number
in the last 30 years.
SLIDE 25
Questions?
