STORM TRACK: January 31, 1982 (Volume 5 Issue 2)

On May 30, 1978, an isolated severe thunderstorm developed ahead of a dry line, northeast of Garden City, Kansas. It moved slowly east and southeast, dropping 1-3" hail for over an hour (one reported to 9" near Spearville), 1-2" rains, several small tornadoes and many small microbursts radiating southwesterly from the storm's base. The last feature was of special interest. to the ST Editor, who is unaware of any other accounts in the literature on downbursts or microbursts extending primarily in a southwesterly direction. Fujita's Manual of Downburst Identification for Project Nimrod and other recent papers show many examples of easterly radiating downbursts. The Garden City storm is the first one in my experience to show predominantly westerly and southwesterly microbursts. Also, and equally interesting, was the repeated recovery and regeneration of these events within a comparatively small area, as if the storm was going through some kind of cycle of limited venting.

Figure 1. Surface analysis.

At 1200 CDT, a 1003.5 mb low was located in southeastern Colorado with a preceding dry line between Trinidad 33 deg F, La Junta 42 deg F, and Dodge City 62 deg F (Fig. 1). A thermal ridge extended from southeastern Colorado through western Kansas, and a moist ridge from central Oklahoma through central Kansas turning westerly through southwestern Nebraska and northeastern Colorado.

An isolated pocket of tcu and small CBs were noted by 2:45 CDT within 25-50 miles north to northeast of Garden City. The NWS issued a tornado watch from 4:00-10:00 PM CDT for southwestern Kansas to northeastern Nebraska. The Garden City storm developed in the extreme southwest corner of the watch. By 4:00 PM CDT, except for small, turbulent but weak CBs about 50 miles northeast of the city, the only significant cell was one small, isolated CB base building slowly 20 miles north-northeast, with an enormous anvil vis-a-vis the base diameter (Fig. 2). The first severe weather was a microburst at 4:53 PM CDT (Shown as "M-1" in Fig. 3. No visible rain was seen and the first hail (pea size) wasn't encountered until 5:04 PM CDT (Hereafter all times are given as PM CDT) at the location of F-18. Subsequently, a proliferation of microbursts, rotating wall clouds and small short-lived funnels and tornadoes sprinkled themselves across the plains northeast, of Garden City. Fig. 3 plots these in numbered sequential order by nature of occurrence (M = microburst, RC=rotating cloud base, RD=rotating dust on ground, RW=rotating wall cloud, F=funnel and T = tornado). The double-line on the highway/farm road indicates the chase route. A few numbered spots are designated on this chase route, which locate photographic sites at the time of and corresponding to each numbered severe weather event in Fig. 3. Additionally, a time scale is given below this Figure, to time-spot each sighting.

Figure 2. Looking SW from 15.9 mi N of Site A on highway. Illustration fron from slide.

Figure 3. #Filming site for F-14, M-15, M-16 and T-17.

An approximate outline of the cell base is shown by lines extending from circlet "A, B, 19, 21" and "24," which are coincident. with the approximate base location within visual range at the time of the severe event, numbered for that time (e.g. RC-24 = cloud base outline 24, F-19 = 19, etc.). One prominent CM area was noted southeast of the storm and was photographed from site F-18 at 5:01.

Fifty one slides were taken of the storm, and most had specific odometer/time notations separately recorded. Of course, all distance estimates from road-side to observed events in Fig. 3 are approximate, based on the photographer's many years of experience (This suggests the need for a future ST article on how accurately we estimate cloud base distance; a key ability for training spotters, who should have a passing knowledge of whether the tornado is 5 miles away or 1 mile away!! -Probably should be Phase II of Spotter training by NWS, after learning what to look for).

Figure 4. Illustration from slide.

Fig. 4 shows a characteristic microburst from this storm, as it moves southwesterly from the CB base. After the dust, reaches its highest altitude, it dissipated and gradually was swept back into the storm's base on returning inflow. Two specific encounters further characterize these events. Microourst M-13 developed about 500 feet northeast of the photographer and moved ominously toward him. It appeared to be like some of the other larger ones in the area but developed far enough away to allow time to enter the car and turn it into the approaching wind(5-7 seconds). He emerged,just after the peak gust, with difficulty, and estimated wind speed at 60-70 MPH in warm outflow. This flow changed after a minute or so into inflow. Apparently, the photographer was sited and sighting along an outflow/inflow boundary, where at least 20-30 similar microbursts occurred (too many to photograph economically). There appeared to be no clear pattern, except for a late developing trend to begin occurring further southeast as the cell base began intensifying ance drifting in that direction.

Figure 5. Illustration from slide.

If the previous wind estimate was correct, then the initial touchdown 500 feet northeast probably involved higher winds -perhaps 80-90 MPH, This high side estimate tends to be supported by the second detailed event, the overturning of a semi-trailer truck (Fig. 5) at location F-18 (6:40 CDT). The estimated truck location prior to overturning (unfortunately no record was taken from the tense and excitable witnesses) was perpendicular to US 156, facing north on a farm road. Assuming an empty trailer and a 45 deg wind angle (characteristic of most microbursts this day), an 80-90 MPH wind might, have been sufficient to turn this rig. What do you think? The photographer was reasonably certain that no tornado had done this work, since he was continuously alert to and observing all parts of the storm, and the trucks distance from him of 3.4 miles at the time of overturning was not obscured by rain. In summary, 20-30 microbursts occurred over a two hour period from 4:53 to at least 6:51, while the storm was in its organizing stage and either stationary or drifting slowly east-southeast. From about 7:44 to 8:10, at least one more was observed, associated with a brief tornado north of Ingalls (Fig. 6). There may have been more microbursts throughout this second stage of the storm (since about 7:00), when it began to move more rapidly to the southeast and raining; heavily, but the viewing angle to the east provided poor contrast for observation.

Figure 6. Illustration from slide.

In its final, and apparently most wind-destructive stage north of Cimarron, a dramatic onion ring shaped cloud base was observed. Blowing dust obscured all visibility from the lower, inner ring to the ground (Fig. 7). In fact, visibility within this core area was likely to have been near zero, with only a reddish opaque tint through windshields or windows. The photographer took two wide angle pictures of the rings but dispaired of encompassing all all of this formation, even in a dozen pictures (he was located under the outermost ring). The diameter of the largest ring appeared comparatively small vis-a-vis the overall storm and may have been less than five miles in diameter. Noteworthy during its maximum organization, about 8:45, was that all rings were -apparently- perfectly circular. The photographer was unable to see any irregularity in this formation in any of the rings for several minutes, as if they had been drawn by an architect's protractor. Figure 7 attempts to capture this occasion, partly based on slides taken at the time. Figures 8 and 9 show two tornadoes observed, respectively, at T-17 and T-23 in Fig. 3. Figure 10 illustrates one interesting, additional insight of the photographer, which may not bB original to others but was new to him. Tornado damage was reported from this small vortex, near the dust on the ground. It may be that downburst triggering of small events like this are the real producers of damage and not the weak vortex that, results. There- fore, even though visible funnels are present (and may be reported by police or trained spotters), they may not be the actual instruments of destruction.

Figure 7. Illustration partly from two slides and partly from memory.

Figures 8 (T-17), 9 (T-23), and 10 (T-20). Illustration from slide.

In summary, a small complex but destructive storm developed northeast of Garden City, Kansas. It developed slowly, ahead of a dryline, and produced numerous microbursts (some damaging) which outflowed southwesterly from the storm's base. At least two tornadoes, three tornadic suction vortices and several funnels were photographed, all short lived and none exceeding 15 seconds. Over a million dollars damage was done in sparsely settled farmland (farm buildings, drainage pipes, crops). In its final stage, a striking onion ring cloud base capped a swirling dust wall that prevented observation, even with clear back lighting from a setting sun. The author briefly considered entering this maelstrom to record what was going on inside, but reconsidered (and survived to write this account). Was Fig. 7 the actual structural outline of a highly organized meso-low? What explains a pulsing microburst (or is it something else), which doesn't vent a substantial mass of the cell at one time but, repeats itself again and again? I'd be interested in your comments.