1. Introduction
2. Data and Analysis
3. Topography
4. Normal Precipitation Distribution
5. Flash Flood Statistics
6. Frequency of Heavy Rain
7. Synoptic Patterns of Heavy Rainfall
8. Sounding Parameters of Heavy Rainfall
9. Conclusions
Acknowledgments
References
IN SOUTHWEST VIRGINIA:
IN EAST TENNESSEE:
IN SOUTHWEST NORTH CAROLINA:
RETURN PERIOD | |||||||
---|---|---|---|---|---|---|---|
RAIN DURATION | 1 Year | 2 Year | 5 Year | 10 Year | 25 Year | 50 Year | 100 Year |
3 Hour | 1.5-2.0 | 1.8-2.5 | 2.3-3.0 | 2.7-3.6 | 3.2-4.0 | 3.4-4.5 | 3.7-5.0 |
6 Hour | 1.8-2.8 | 2.2-3.2 | 2.7-4.0 | 3.2-4.8 | 3.7-5.3 | 4.0-5.8 | 4.6-6.8 |
12 Hour | 2.2-3.4 | 2.5-3.7 | 3.2-5.2 | 3.7-5.5 | 4.3-6.8 | 4.7-6.8 | 5.4-7.8 |
24 Hour | 2.4-3.8 | 2.7-4.7 | 3.7-5.7 | 4.2-7.2 | 4.8-7.8 | 5.5-8.5 | 5.8-9.8 |
Source: 'Rainfall Frequency Atlas of the United States', Technical Paper #40, Weather Bureau, May 1961.
Date of Events | Surface Features | 500-mb Pattern | Classification |
---|---|---|---|
March 11-12, 1963 (Nighttime event) |
Warm front (W-E) over TN valley w/ approaching low pressure and associated cold front (N-S) | Strong southwest flow (70 knots) ahead of trough over Plains states | Synoptic |
October 4, 1964 (Daytime event) |
Slow moving cold front (SW-NE) w/ strong tropical low pressure ('Milda') over lower MS valley | Weak southwest flow (20 knots) | Synoptic |
July 27, 1969 (Daytime event) |
Outflow boundaries located over southern Appalachians | Weak southwest flow (20 knots) w/ closed low over Great Lakes region | Meso-high |
August 4, 1969 (Nighttime event) |
Weak stationary front (SW-NE) over southern Appalachians | Trough over TN valley w/ weak southwest flow (20 knots) | Frontal |
May 27-28, 1973 (Nighttime event) |
Quasi-stationary front (N-S) over southern Appalachians w/ prefrontal squall line approaching from west | Closed low over Plains states w/ strong southwest flow (60 knots) | Synoptic |
August 13, 1973 (Daytime event) |
Outflow boundaries over southern Appalachians w/ stationary front (W-E) over Ohio valley | Weak short wave over southern Appalachians w/ west flow (30 knots) | Meso-high |
September 13, 1973 (Daytime event) |
Weak stationary front (W-E) w/ weak tropical low pressure over lower MS valley | Weak southwest flow (20 knots) w/ weak ridge over Mid Atlantic states | Frontal |
May 22-23, 1974 (Nighttime event) |
Prefrontal trough (SW-NE) w/ weakening cold front (SW-NE) over Ohio valley | Deepening trough over TN valley w/ southwest flow (30 knots) | Synoptic |
May 28-29, 1976 (Nighttime event) |
Strong, slow moving low pressure over west TN w/ occluded front (NW-SE) extending over southern Appalachians | Closed low over mid MS valley w/ south flow (30 knots) | Synoptic |
July 27, 1976 (Daytime event) |
Outflow boundaries located over southern Appalachians w/ prefrontal trough (W-E) over the Ohio valley | Weak southwest flow (15 knots) w/ weak ridge over Mid Atlantic states | Meso-high |
September 7, 1977 (Daytime event) |
Weakening tropical low pressure over AL approaching stationary front (W-E) over southern Appalachians | Weak trough w/ southwest flow (25 knots) | Tropical ('Babe') |
November 5-6, 1977 (Nighttime event) |
Weakening tropical low pressure over GA w/ trough (NW-SE) over southern Appalachians | Closed low over AL w/ strong southeast flow (40 knots) | Tropical (Unnamed) |
July 20, 1979 (Daytime event) |
Weak stationary front (W-E) over TN valley | Weak trough over mid MS valley w/ weak southwest flow (20 knots) | Frontal |
March 20, 1980 (Daytime event) |
Warm front (W-E) moving north w/ approaching low pressure and associated cold front (N-S) | Deepening trough over Plains w/ strong southwest flow (40 knots) and weak ridge over Mid Atlantic states | Synoptic |
June 1, 1987 (Daytime event) |
Outflow boundaries over southern Appalachians | Weak short wave trough over mid MS valley w/ southwest flow (25 knots) and ridge over Mid Atlantic states | Meso-high |
August 21-22, 1990 (Daytime event) |
Outflow boundary (W-E) located near quasi-stationary front (N-S) over southern Appalachians | Weak trough w/ weak west flow (15 knots) | Meso-high |
March 27, 1994 (Nighttime event) |
Surface trough (W-E) located ahead of approaching strong cold front (SW-NE) | Strong southwest flow (75 knots) ahead of strong trough over Plains | Synoptic |
June 26, 1994 (Nighttime event) |
Prefrontal trough (SW-NE) over TN and Ohio valleys ahead of approaching cold front (N-S) | Deepening trough over TN valley w/ strong southwest flow (50 knots) | Synoptic |
October 4-5, 1995 (Nighttime event) |
Strong tropical low pressure approaching stationary front (SW-NE) over TN valley | Closed low over AL w/ strong south flow (50 knots) | Tropical ('Opal') |