A winter storm will impact the central Appalachians to the Northeast through the night. Accumulating snow is expected for interior New England and the northern Mid-Atlantic. Scattered showers and occasional thunderstorms will persist across Florida and the Southeast coast. Locally heavy mountain snow is expected in the Great Basin and Rockies over the next couple of days. Read More >
Overview
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Several powerful supercell thunderstorms moved through southeast Colorado July 29th, 2009. One brought hail up to the size of tennis balls in the Pueblo area, causing millions of dollars worth of damage.
There was one confirmed tornado in west-central Baca County. It was ironic with all the supercell thunderstorms acrsoss southeast Colorado, with their twisting, powerful updrafts, the lone tornado was a relatively weak landspout spawned by a quickly developing non-rotating thunderstorm cell. Opposing currently of air at the boundary were pulled up , as the thunderstorm cell developed upward. The \circulation was stretched upward and the diameter of the circulation decreased. Much like what happens when an ice skater draws their arms in towards their body, when spinning. The rotation increased and a short-lived tornado spawned. Tom Magnuson, Warning Coordination Meteorologist |
 Courtesy of Laura Ming |
Radar:
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| Base Reflectivity and Base Velocity of the Tornadic Event | Circled Location of Where the Tornado Spawned 4:57 PM MDT |
Circled Location of Where the Tornado Spawned 4:59 PM MDT |
Environment
The dew point temperature in Pueblo at 6:00 AM MDT was 60ºF, which illustrates that there is low-level moisture to help initiate supercell thunderstorms. The primary lifting mechanism is visible on the 6:00 AM MDT, 700-hPa analysis, which illustrates an upper-level low located over Ontario, Canada, and two shortwave troughs embedded in the upper-level flow. The second shortwave trough, located over Wyoming, is likely the shortwave that helped initiate the thunderstorms. Another notable lifting mechanism is an upper-level divergence maximum analyzed on the 300-hPa (contoured in yellow) located over Baca County, in response to ageostrophic circulations around an analyzed weak jet streak. Located in the "Additional Environmental Data" section, a 700-hPa analysis of theta-e is shown to illustrate that there was also a moisture boundary in place. What was interesting about this case, was that there wasn't much for CAPE or shear analyzed in the sounding profiles from KDNR and KDDC for both the 6:00 AM and 6:00 PM MDT soundings. The 6:00 AM MDT KDNR sounding did indicate 559 J/kg*K of CAPE. The 2100 UTC METAR observation from Springfield, Colorado (located in Baca County) is as followed, KSPD 2056 79 65 62 150 16 20 993 074, which indicates that there was an air temperature of 79ºF and a dew point temperature of 65ºF. Assuming that the upper-level characteristics of the 6:00 AM MDT KDNR sounding did not change too much, a 79ºF air temperature and a 65ºF dew point temperature would be sufficient to create enough CAPE for supercell thunderstorms. The low-level shear likely came from a westerly propagating outflow boundary associated with a supercell that developed east of where tornadogenesis occurred (see radar volume scan animated gif).
SPC Upper-Air Maps:
July 29th, 2009 at 6:00 AM MDT
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| Surface Analysis | 850-hPa Analysis | 700-hPa Analysis |
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| 500-hPa Analysis | 300-hPa Analysis |
July 29th, 2009 at 6:00 PM MDT (After the Tornado)
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| Surface Analysis | 850-hPa Analysis | 700-hPa Analysis |
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| 500-hPa Analysis | 300-hPa Analysis |
Upper-Air Soundings (Skew-T log P Diagrams; Taken from Plymouth State University):
July 29th, 2009 at 6:00 AM MDT
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| Sounding from KDNR | Sounding from KDDC |
July 29th, 2009 at 6:00 PM MDT (After the Tornado)
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| Sounding from KDNR | Sounding from KDDC |
Additional environmental data:
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| Theta-E Analysis from 6PM MDT |
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