Tornadoes with Cold Core 500-mb Lows

Jonathan M. Davies Wichita, Kansas

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Abstract

Tornadoes that occur in close proximity to midlevel closed lows with a core of cold temperatures aloft are not uncommon, particularly in the central United States. Although several informal studies have shown that severe weather and tornadoes can occur with these midlevel lows, little in the way of formal work has been published documenting features and ingredients of such systems, especially those that produce what are sometimes called cold core tornadoes. Of particular concern is that these tornadoes can be associated with surface and low-level moisture that appears deceptively small or marginal regarding severe weather potential, yet on occasion tornadoes of F2 or greater intensity can develop. In other cases, vertical shear may appear relatively weak at locations close to the midlevel low, suggesting little potential for tornadoes. These “atypical” characteristics can result in poor anticipation by forecasters of tornado events associated with closed 500-mb lows. This note documents some synoptic and mesoscale features commonly associated with tornado events in close proximity to cold core 500-mb lows using four tornadic cases in Kansas as examples, including photographs to show the small nature of storms associated with such systems. Recognition of surface patterns with a particular organization of boundaries and surface heating positioned near midlevel lows, along with the presence of some amount of buoyancy, can help with the operational awareness of the potential for tornadoes in many 500-mb closed low settings.

Corresponding author address: Jonathan M. Davies, 3206 N. Westwind Bay, Wichita, KS 67205-2528. Email: jdavies1@cox.net

Abstract

Tornadoes that occur in close proximity to midlevel closed lows with a core of cold temperatures aloft are not uncommon, particularly in the central United States. Although several informal studies have shown that severe weather and tornadoes can occur with these midlevel lows, little in the way of formal work has been published documenting features and ingredients of such systems, especially those that produce what are sometimes called cold core tornadoes. Of particular concern is that these tornadoes can be associated with surface and low-level moisture that appears deceptively small or marginal regarding severe weather potential, yet on occasion tornadoes of F2 or greater intensity can develop. In other cases, vertical shear may appear relatively weak at locations close to the midlevel low, suggesting little potential for tornadoes. These “atypical” characteristics can result in poor anticipation by forecasters of tornado events associated with closed 500-mb lows. This note documents some synoptic and mesoscale features commonly associated with tornado events in close proximity to cold core 500-mb lows using four tornadic cases in Kansas as examples, including photographs to show the small nature of storms associated with such systems. Recognition of surface patterns with a particular organization of boundaries and surface heating positioned near midlevel lows, along with the presence of some amount of buoyancy, can help with the operational awareness of the potential for tornadoes in many 500-mb closed low settings.

Corresponding author address: Jonathan M. Davies, 3206 N. Westwind Bay, Wichita, KS 67205-2528. Email: jdavies1@cox.net

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