1 / 23

(treehugger) ‏

Synoptic-Scale Conditions Leading to Flooding in South Carolina: A Case Study of October 22-23, 1990. (www.treehugger.com) ‏. Erik D. Kabela Joanne Stevenson Mini Tech 2009. Objectives.

theresaa
Télécharger la présentation

(treehugger) ‏

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Synoptic-Scale Conditions Leading to Flooding in South Carolina: A Case Study of October 22-23, 1990 (www.treehugger.com)‏ Erik D. Kabela Joanne Stevenson Mini Tech 2009

  2. Objectives Illustrate the effects on society (public/private property damage, evacuations, loss of life, etc) of this event. Link Maddox's (1979)* definition of a synoptic flash flooding event with October 22-23, 1990 event Determine which of the 5 heavy rain event set-ups identified by Konrad (1997)** fits with this event Enhance the understanding and application of pattern recognition in heavy rain and flood forecasting *Maddox, R. A., Chappell, C. F. and L. R. Hoxit, 1979. Synoptic and Meso-α Scale Aspects of Flash Flood Events. Bull. of the Amer. Meteor. Soc. , 60 (2), 115-123. **Konrad II, C. E., 1997. Synoptic-Scale Features Associated with Warm Season Heavy Rainfall over the Interior Southeastern United States. Wea. Forcasting, 12, 557-571.

  3. Methods • Archives • The State, Greenville News, Aiken County Standard, The New York Times • SHELDUS • Web interfaces: • NCDC - NOMADS • Plymouth State University -Plot generation interface • NOAA - National Severe Storms Laboratory • NOAA – Daily Weather Maps • USGS – Water Resources Data (Maddox et al., 1979)‏

  4. Flooding Impacts • SC hit by disintegrating Hurricane Klaus and Tropical Storm Marco (Oct. 8-14)‏ • Up to 15” of rain • Damage of $3-8 million, several thousand evacuations, 120 dam failures, 5 deaths • Cold front moved through (Oct.22)‏ • Day and a half of nearly continuous rainfall on already stressed hydro system • 11 counties receive Presidential Disaster Declarations (PDDs)‏ • >1,400 registrations for temporary housing, recovery of lost property, or repairs • >$10 m of aid administered by federal government (NOAA,http://www.hpc.ncep.noaa.gov/tropical/rain/marcoklaus1990.html)‏

  5. Pre-Exisiting Conditions Flood Stage

  6. Heavy Rain/Flood Definition • According to Konrad (1997)‏ • At least 2 inches in a 6 hour period • Break in between hourly precipitation could not exceed 2 hours

  7. 36-Hour Total Precipitation

  8. Components of a Maddox Synoptic-Type Flood Event • Quasi-stationary or slow moving weak cold front • Ample low-level moisture • Usually greater than 60°F surface dew point • 500mb strong short-wave trough • Ample mid-level moisture • Dew point depression of <= 6°C

  9. Surface Map – Oct. 22, 1990

  10. 500mb – Oct. 22, 1990

  11. Maddox Ideal vs. Oct 23 00Z Surface Map Td = 70 Td = 70

  12. Maddox Ideal vs. Oct 23 00Z 500mb Map

  13. Comparison to Konrad – Type 2 Key Contributions Include: • Slow moving cold front • Type 2 typically occurs during the transition season • Ample low- and mid-level moisture • Low-level convergence • Located NW of heavy rain • Upper-level divergence • Strong 500mb Vorticity Max • Strong mean 850-200mb winds (>21 m/s) from the SW • Strong instability using the K-Index • 850mb warm-air advection • Rain cells develop in “echo train” pattern

  14. Ample Mid and Low-Level Moisture • 700Mb mixing ratio of greater than 7 g/kg • Surface precipitable water of greater than 1.5 inches (38.1 mm)‏

  15. Low-level Convergence • Low-level convergence max to the NW of the heavy precipitation

  16. 200mb Divergence • Upper-level divergence promotes upward motion • Heavy Rain area located over the left exit region of jet

  17. 500mb Vorticity Maximum • Heavy rain located to the right of vorticity max

  18. 850 – 200mb Winds • Mean 850 to 200mb winds blowing parallel to surface boundary • Mean 850 to 200mb wind speed ≈24m/s

  19. Instability with the K-Index • K-Index between 28 and 32 • Corresponds to roughly 40-60% chance of showers and thunderstorms

  20. 850mb Warm-Air Advection • 850mb WWA promotes low-level rising motion

  21. Conclusions • Pre-existing stream conditions lead to increased potential for flooding on Oct 22-23 • Flooding event of Oct. 22-23, 1990 fits classification of Maddox synoptic-type flood • Flooding event further broken down into a Konrad Pattern 2 heavy rain event • Provides a basis for using climatological studies for use in everyday forecasting • Can prove useful for operational forecasters as well as emergency managers

More Related