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Storm Development in an Unfavorable Environment...Part II Mark Cunningham NWSFO Jackson Peter Wolf NWSO Wichita, KS Synoptic Composite Chart at 00 UTC on 5/15/97 Large, thick arrows are upper level jets Large thin arrows is the low level jet Small arrows indicate surface flow The 16 degree Celcius surface dew point contour May 15, 1997, 00 UTC Jackson, MS modified sounding Cape = 1426 JK/g 500 mb LI= -6 K-index = 26 SWEAT Index= 328 700-500mb lapse rate = 7.2 deg/Ckm WBZ level = 10,026 ft May 15, 1997 00 UTC Jackson, MS hodograph 0-3km SR Hel=33 m2/s2 0-6km shear vector= 22 m/s 0-1km swise vort= 5/s storm motion from 281 degrees at 31 knots May 15, 1997, 00 UTC, Jackson, MS modified hodographs Top hodograph observed storm motion 305 degrees at 29 knots 0-3km SRH=126 m2/s2 Bottom hodograph 0-3km SRH = 261 m2/s2 0-6km Shr vector = 30 m/s 0-1km swise vort = 32/s 0.5 degree reflectivity at 2131Z on 5/14/97 Hail size= 2.25 in Vil= 56 68 DBZ to 11,000 ft Cell located at azran 359 degrees at a range of 57 nm or over northern Holmes county. 0.5 degree reflectivity at 2152Z Hail size > 3.00 in Vil = 63 69 DBZ at 10,000 ft cell located at azran 5 deg at range 52 nm or over northeast Holmes county Cell has a bounded weak echo region and greater than 65 DBZ up to 26,000 ft 0.5 degree storm relative velocity at 2212Z Cell has a defined TLS TLS has a base of 4000 ft and a top of 23,000 ft Max low altitude gate to gate rotational velocity is 32 knots 0.5 deg reflectivity at 2217Z Cell has a hook Hail size > 3.00 in Vil = 59 72 DBZ at 18,000 ft Cell located at azran 19 degrees at a range of 47 nm or over western Attala county 0.5 degree reflectivity at 2232Z Hail size = 3.00 in Vil = 55 70 DBZ at 18000 ft Cell located at azran 29 degrees at a range of 46 nm or over Attala county Time-height series plot of rotational velocity Height is from 2 km to 9 km Time is from 2132Z to 2232Z A thin 12m/s contour is drawn Bold numbers indicate rotational velocities greater than 15m/s Conclusion On May 14, 1997 a thunderstorm became supercellular as it tracked southeast along an apparent outflow boundary produced by organized convection to the east. As this cell interacted with the boundary, strong horizontal streamwise vorticity was ingested into the updraft, leading to the formation of a strong low level mesocyclone. KJAN WSR 88-D indicated supercell signatures, including a bounded weak echo region, strong low level mesocyclone, and low level hook echo in the reflectivity pattern.

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