CASE STUDY OF THE MAY 7, 2002
GREAT PLAINS OUTBREAK
Illustrated Abstract. See also Full PowerPoint HTML Presentation
I.
| 00 UTC SYNOPTIC ANALYSIS OF SURFACE PLOT |
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| Moist Gulf air spread into Oklahoma, Arkansas and Kansas (green polygon on map), with the dryline stretching near the edge of the Texas panhandle...and the trough situated just west of the tornadic outbreak in central Kansas.
Surface winds over central Kansas and western Missouri are SSE. |
II.
| 2200 UTC 500 mb CHART |
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| A longwave trough extending through the Pacific NW and Nevada approaches the Southwest and, ultimately, the Great Plains region. There is also a weak shortwave trough over the Sangre de Christo mountains of New Mexico.
The upper air flow here is the strongest over the Great Plains region, suggesting a good shear environment with the surface winds in that area. |
III.
| 00 UTC Norman, Oklahoma Sounding |
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| This is a classic Miller Type I ("loaded gun") sounding, with three air masses. The lowest of the masses is the deep moist layer (DML), from the surface to 850 mb; moist Gulf air provides the elevated mixed layer (EML), from 775 to roughly 500 mb. Above 500 mb is the dry third layer, the Pacific air mass (P).
The CAPE is absolutely huge (4892 J kg^-1); also, the area of CINH is so small (and the LFC is close to the ground) that deep convection explodes through the troposphere. Compare the 500 mb and surface winds: Note the difference in speeds and direction, both providing an excellent shear environment. |
IV.
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| Indeed, the 0-6km shear environment is especially highest over central Kansas and western Missouri. (Recall that the tornado cluster occurred over Kansas.) |