010421 Hoisington, KS F4 Tornado

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ABSTRACT

On April 21st, 2001 a supercell thunderstorm produced a tornado which moved through the town of Hoisington, KS during the evening hours. Investigation of the observed data for this event indicated a possible contributor to the storm environment may have been a meso-scale stratospheric intrusion which nearly escaped measurement by the existing synoptic scale sounding and wind profiler network. The 0000 UTC Dodge City upper air sounding which ascended just upstream of the supercell and in its immediate wake exhibited a substantial lowering of the tropopause and a distinct layer of weakened and backed wind flow at that level. We suggest that this may show a narrow ribbon of stratospheric air injected into the troposphere in close proximity to the upstream side of the storm. GOES water vapor imagery of the event also suggests this finding. Some discussion is offered as to the possible significance of this feature and its relation to the synoptic scale and meso-scale environment of the storm.

 

Loose comments

Synoptically at the surface, cyclogenesis occurred during the afternoon hours along the Front Range of Colorado while the attendant east-west oriented warm front lifted north into central Kansas. Relatively deep moisture (~100 mb) advected northward south of the front, with the moisture axis into south-central Kansas. A dryline developed, extending south from the warm front through southwest Kansas.

Deep moist convection initiated shortly after 23Z. At that time the front extended from the surface low in SE CO, to just north (quantify with LVL-II data) of Hoisington, KS, and continued through NE KS. Initiation occurred along a diffuse, rapidly retreating dryline, ~30 km south of the warm front over northwest Edwards and southeastern Hodgeman counties; theta-e axis immediately east of activity. The warm front continued to move slowly northward as the cells matured.

  • Fig. 1. 0200 UTC Surface Map. Standard station model used: temperature and dewpoint (F), pressure (mb), sky conditions, and precipitation. Winds in knots with one pennant, one full barb, and one half barb equal to 50, 10, and 5 knots, respectively. Pertinent surface features depicted; MSLP contoured every 2 mb, dewpoints >50F every 5 degrees. Note, ASOS/AWOS specials were utilized in the subjective analysis but removed for image clarity. If subjective analysis suggested stations were generating erroneous variables, those variables were then omitted from analysis. Surface data 14 hours prior to 0200 UTC were analyzed to minimize feature(s) error.
  • Fig. 2. Qc'd skew T-log p diagram depicting the 0000 UTC 22 April DDC sounding. Pressure are in mb, and temperatures are in Celsius. Winds as in Fig. 1. The parcel process curve is for a lifted surface parcel (no parcel dilution). Values of CAPE and CIN were computed based on the virtual temperature buoyancy.
  • Fig. 2a. As in Fig. 2 but for the raw Sngd. Note the upper level warming.
  • Fig. 3. As in Fig. 2. but for OUN.
  • Fig. 4. DDC Tilt-1 NIDS BREF 2-hr animation, 2232-0131 UTC (through initiation). ~1 Meg download. Excuse the wobble as the amimation was created through screen captures.
  • Fig. 5. 0212 UTC tilit-1 mosaic REF/VEL/SRVEL for DDC and ICT with sfc obs as in Fig. 1. and geography. To view this, you'll need to install a pluggin. You'll need to know how to use the pluggin to toggle, turn on/off the products.