UW-Madison AOS 453 - In Like a Lion - The March 8th, 2000 Tornado

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In Like a Lion: The March 8th, 2000 Tornado Theodore Lyons University of Wisconsin-Madison Abstract The tornado that struck Milwaukee, WI on March 8, 2000 was the earliest on record. Unlike most tornadoes, this particular tornado was not associated with a supercell or any form of a mesocyclone. The author argues that a lake breeze circulation created a misocyclone in the region, which was elongated vertically by a rapidly deepening convective thunderstorm in the region, producing the tornado.I. Introduction March has always been a month of transition for Wisconsin weather. Today’s rain will give way to tomorrow’s blizzard; today’s mild temperatures will plunge to a wind chill advisory. Hence, even the 77-degree highs that occurred in Milwaukee on March 7-8 were unusual but not extraordinary. Such is the nature of Wisconsin weather. What are not expected in March are severe thunderstorms, much less tornadic activity. According to the National Severe Storms Laboratory, Southern Wisconsin has only a one percent chance of suffering a severe thunderstorm on a given day by late April, and only a .25 percent chance of a tornado in the same period. The ingredients are rarely in place for significant convective activity (except, perhaps for thundersnow), considering temperatures typically peak around 40 degrees and dewpoints only occasionally break the freezing point. March 8, 2000 was not your typical dreary March day. Insolation coupled with strong warm air advection boosted temperatures to a record 77 degrees Fahrenheit. Imbedded in the warm flow was unusually moist air from the Gulf of Mexico, bringing dewpoints to near 60 degrees and destabilizing the atmosphere. Additionally, several synoptic features in the area aided ascent. Nor was the tornado that touched down around 6 pm local time your typical tornado. According to the NWS, it was the earliest recorded tornado in Milwaukee’s recorded history, which stretches back to 1840. Fueled by perhaps as little as a lake breeze or a preceding storm’s out flow, this F1 tornado had a path 75 yards wide and 2.5 miles long. Several persons were injured, and many buildings suffered structural damage. In total, the tornado caused 4.6 million dollars in damage. Considering the storm was so exceptional and unusual, some may question the usefulness in analyzing its genesis. There are two critical reasons to come to a basic understanding as to how this storm developed. First, the tornado was largely a surprise event, and even an unexpected weak tornado can wreak havoc. Even though such a situation may never occur again in a forecaster’s lifetime, it is important to stay vigilant of even the most unusual situations. Secondly, the recent IPCC report on global climate change has suggested that Wisconsin winters may become much milder in the future. In fact, IPCC reports indicate that it is likely Wisconsin winters will bear a closer resemblance in the future to the winters that Arkansas experiences in the present. Although it is ludicrous to assign mesoscale features to global climate change patterns, it is reasonable to expect that warmer winters may allow for earlier severe weather seasons. This case study will contend that several unique mesoscale features contributed to this storm. Initially, a dryline through south centralWisconsin and north central Illinois most likely played a significant role in the early development of this storm. Later, as the convective thunderstorm approached lakeshore, a lake breeze near the surface likely created the vorticity necessary to produce a misocyclone and the tornado. II. Data Sources Data collection for this event was exceedingly difficult. Radar, satellite, and radiosonde data each had several errors or data missing that hampered proper investigation of this event. Though none of the problems proved fatal, it is worth noting each issue. In a terrible irony, the Milwaukee/Sullivan radar station was down during the entire event. In its place, data from Chicago/Romeoville was used. However, distance issues with this data make this selection not ideal. This storm developed and moved on the fringes of Romeoville’s radial velocity range, a critical tool in the analysis of tornadic events. As will be shown, outflow from a previous thunderstorm and/or a lake breeze probably contributed to the development, but the lack of radial velocity data in the region makes each possibility more conjectural than demonstrable. Additionally, the distance also prohibits the radar from getting any returns within the boundary layer, another serious impediment to proper analysis. Satellite data also suffered from unavailable data. Between 23:45z on March 8 and 00:45z on March 9, there is neither visible nor IR data available. Typically, this would be a minor issue, but this is exactly when the tornado is touching down. However, the satellite after this time shifted to rapid scan operation, which allowed for analysis of the later stages of the tornado. Radiosonde data also was rendered less meaningful by missing data. For whatever reason, the key sounding (00z on March 9) from Green Bay provided no wind data above 675 millibars, precluding the creation of a hodograph or having a true measurement of shear. Though data can be extrapolated from upper air reanalysis, it is unfortunate that the radiosonde could not provide hard evidence. Fortunately, much of the data was quite useable. As previously mentioned, Level II radar data, provided by the NCDC, from Romeoville, IL was used, and ingested using IDV. Satellite data (used for reference, not in the final form) was from GOES-East, primarily using the longwave IR and WV bands, provided by the NCDC’s CLASS data service. Model data from the NAM 00z run on March 8th was used to provide context and further analysis. Finally, radiosonde data from the University of Wyoming, coupled with North American Regional Reanalysis from Plymouth State allowed for additional investigation.III. Synoptic Overview Such an unusual storm requires very unusual conditions. Although conditions would generally only be considered merely adequate for strong thunderstorms during warmer months, their very presence was highly anomalous for the late winter/early spring. In many regards, this storm was the product of a violent clash between two sharply different air parcels. The most readily apparent synoptic feature of this day was the


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