Climatology of Boundary Layer Winds in the Southeast United States and its Relationship to Nocturnal Tornado Episodes Alicia C. Wasula and Lance F. Bosart University at Albany/SUNY, Albany, NY Russell Schneider, Steven J. Weiss, and Robert H. Johns Storm Prediction Center, Norman, OK Geoffrey S. Manikin NOAA/NWS/NCEP/EMC, Camp Springs, MD Patrick Welsh NOAA/NWSFO Jacksonville, FL Research Supported by COMET grant #S99-19133
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Alicia C. Wasula and Lance F. Bosart University at Albany/SUNY, Albany, NY
The Structure and Climatology of Boundary Layer Winds in the Southeast United States and its Relationship to Nocturnal Tornado Episodes. Alicia C. Wasula and Lance F. Bosart University at Albany/SUNY, Albany, NY Russell Schneider, Steven J. Weiss, and Robert H. Johns - PowerPoint PPT Presentation
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The Structure and Climatology of Boundary Layer Winds in
the Southeast United States and its Relationship to Nocturnal
Tornado EpisodesAlicia C. Wasula and Lance F. Bosart
University at Albany/SUNY, Albany, NY
Russell Schneider, Steven J. Weiss, and Robert H. JohnsStorm Prediction Center, Norman, OK
Geoffrey S. ManikinNOAA/NWS/NCEP/EMC, Camp Springs, MD
Patrick WelshNOAA/NWSFO Jacksonville, FL
Research Supported byCOMET grant#S99-19133
• High frequency of overnight/early morning tornadoes in southeast US
• Particularly strong signal near Gulf Coast• Relatively high number of fatalities at night
32 N
F2 or Greater 1950-2001East of 94 W, South of 36.5 N
Month
Tim
e (U
TC
)
20
20
5040
30
4030
20
20
20
30
6050
20
10
2010
10
10
10
20
10
20
40
30
3020
60
50
8070
40
40
50
10090
60
30
20
20
4030
20
50
APR MAY JUN JUL AUG SEP OCT DEC JANNOVFEB MARJAN
6-9
6-9
9-12
12-15
18-21
15-18
0-3
21-0
3-6
• High frequency of overnight/early morning tornadoes in southeast US
• Particularly strong signal near Gulf Coast• Relatively high number of fatalities at night
32 N
9
9
12
12
129
99
12
1212
12
99
9
18 15
18159
9
66
6
6
12
15
3
9
3
6
6
6
9
3
3
3
3 39
9
9
3
12
12
12
12
2118
18
15
15
15
1518
91212
18
2124
12
15
18
15
15
1215
96
15
15
9
96
12
15
12
9
9
F2 or Greater 1950-2001East of 94 W, South of 32 N
Month
Tim
e (U
TC
)
APR MAY JUN JUL AUG SEP OCT DEC JANNOVFEB MARJAN
6-9
6-9
9-12
12-15
18-21
15-18
0-3
21-0
3-6
Motivation
1. What is the climatology of surface and boundary layer winds in the southeast US?
2. How do they vary diurnally?
3. What does the boundary layer wind structure look like during tornado episodes?
Data Sources
• Historical pilot balloon (pibal) wind data– 1948-1957, 4x/day, wind data for lowest ~3km
• Hourly surface data (1995-2000)
• Eta regional reanalysis (32 km)
Pibal Stations
1000 m Wind Climatology
0900-2100 UTC Meridional Wind (1000 m) vs. Latitude