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Why is Spring Time Severe Weather
So Severe in Eastern Kansas?

GENE VIALLE

Introduction

This paper will cover some of the specifics that shape the severe weather patterns in the Eastern Kansas area. Much of the unique severe weather is driven by the topography of the middle portion of the North American continental landscape. Additionally, there are smaller scale physical features of Eastern Kansas which modulate the more general weather patterns. After the dynamic weather processes that are driven by the plains landscape are brought to light and transformed to scientific method a useful forecast may be derived. After the forecast is complete, the job of a broadcast meteorologist is not done until this information is acted upon by the public.

Central United States Regional Topography

The central region of the United States east of the Rocky Mountains is unique regarding warm season severe weather. No other place on earth has the intensity and frequency of severe convective outbreaks. There are many physical geographic features in the plains states that collectively cumulate into this massive collection of energy.

The Rocky Mountains range is a north south orientation which is counter to most others on earth with an east west perspective. This accomplishes two processes: first the mountains block a moderating oceanic air mass from the Pacific; and second they induce a semi permanent lee side wave over the plains states. This is the largest standing wave on earth and a consistent source of cyclogenesis. To the east of the Rockies exists an expanse of topography extending from cold and dry northern Canada to the hot and humid Gulf of Mexico. This region has minimal variation in relief in the north south axis and allows a free flow of air and energy. These two air masses are in constant juxtaposition to each other with no restricting topography. The density gradient setup by these two contrasting air masses forms the polar front at their approximation. This front circulates over the plains states from Texas to southern Canada year round. No other continent in the world occupies the polar front year round. The front in effect adds low level convergence, upper level divergence and wind shear to the system.2

A dry, hot air mass originating in the desert of southwestern United States and northern Mexico layers over the plains lower atmosphere and caps the system keeping it in check. All the while, the energy and momentum is building only to be released when maximally energized. Various processes which are difficult to forecast cause the erosion of the above described capping air layer.2

A warm and humid lower level southerly stream of air builds in a nocturnal cycle. This low level jet brings momentum, shear, heat and moisture to the convective process. This low level jet potentates the system in the night time hours when vision is poor and people are off guard adding additional hazards to already dangerous situations.2

Forecasting Implications

These atmospheric processes as related to the plains states are at their optimal energy level during the springtime of each year. Any weakness in depicting the intensity, location and timing of any of the processes will in effect invalidate an accurate forecast of severe weather in eastern Kansas. Lift, moisture advection, instability and shear must all be forecast accurately through time and space. The above mentioned synoptic and sub-synoptic processes need to be delineated and understood before smaller mesoscale processes can be added to the forecast equation.

Forecast models are highly relied upon and unfortunately have many intrinsic weaknesses in forecasting severe weather of the eastern plains states. Depicting the short-waves as they cross the Rocky Mountains or as they redevelop in the lee of the mountains can be poorly resolved by the forecast models. Springtime cold fronts can be shallow or weak. These fronts can also be poorly timed by the various models. Return flow of warm, humid air can be inaccurately initialized due to sparse reporting station data. Eastern Kansas has a much more diverse topography than the stereotypic "Wizard of Oz" perception. Flat, monotonous territory is more accurately depicted in the westerly sections of Kansas. To the north of Kansas City lies a heavily glaciated and carved landscape with a limestone base. The Missouri River Valley which bisects this terrain can also set up areas of low level convergence and accelerations of wind. Trending east-west north of my area in the southern Kansas City region lays the Kansas River Valley. South of us, also trending east-west, lays the Arkansas River Valley. Both of these valleys, depending on wind direction, may set up significant low level convergence and lift. There is a gradual increase in elevation going north from the Gulf of Mexico as well as traveling west from the Mississippi River Valley in eastern Missouri. This increase relief is accentuated rather acutely immediately west of the Missouri River Valley in the Kansas City area. Orographic lifting must be accounted for when the wind directions are from the east through the southerly corridor. Kansas has a rich agricultural history. The farms are smaller and more diverse in crop composition than the vast wheat fields of western Kansas. The sharp contrast in albedo and specific heats of the various crops can set up density boundaries of infinite possibilities. The immense wheat fields covering a large area of western Kansas can add a large amount of humidity as an air mass advects over the fields and before reaching the Kansas City area. The extent of this evapotranspiration can be followed by the satellite images which resolve chlorophyll using Landsat technology.

All of these processes can be accurately described both in time and space; however, severe weather outbreaks can still be inaccurately described if the trigger mechanism for convection is poorly resolved. Resolving mechanisms which set off the chain of reactions continues to challenge meteorologists. These processes can be on a very small scale and therefore difficult to depict. Mesoscale models such as the MM5, Rapid Update Cycle, and meso Eta have more layers, increased resolution and are updated more frequently than synoptic models. Theta E ridges also may be helpful in pinpointing a potential trigger location. Making an accurate forecast in our area consists of evaluation of the analysis charts and the various synoptic models as well as the radar and satellite images. One should also read the analysis of the NWS forecaster in their various forecast discussions and SPC discussions and outlooks. After a forecast has been made and the time has passed, a critical analysis of the accuracy is in order. Only after a long period of scientific analysis and re-evaluation of a particular area's daily results, forecast accuracy can be optimized.

Beyond Forecasting - Public Safety

It would seem that after a meteorologist developed consistently accurate severe weather forecasts that the job would be accomplished. However, the job is not done until accurately depicted data, delivered in a timely manner, has been consistently acted upon by the public, therefore keeping the community out of harms way.

The public can be divided into a few main sub groups:
Those unaware of a threat;
Those aware of a threat but do not act upon it;
Those aware of a threat, wish to act upon it, but do not know what to do;
Those who are dependent upon others such as children, hospitalized patients and the elderly; and
Those aware of a threat, act upon it appropriately but have bad luck.3

The public can be educated with the most consistent, dependable, communication technologies. The chosen technology varies from individual to individual from AM/FM radio, television, weather radio with SAME technology and the internet. More importantly, people should be made aware of some of the basic terminology as defined by the National Weather Service from the meaning of warnings, watches or outlooks etc.

People should have a basic knowledge of the most common severe weather threats to their local area. Weather warnings specific to an area frequently mention threats in relationship to nearby towns, rivers or valleys. Having knowledge of various locations in a local radius around their community better equips people to act in an appropriate manner. It helps individuals to run through worst-case, what if scenarios and plan escapes, automobile preparations and home protection . There are excellent sources for methods and materials to fortify your home structure designed for optimal protection in severe weather events.

Conclusion

This paper has brought to light the physical features that drive severe weather patterns in eastern Kansas. These features start on the global scale and are modulated by the signature landscape of Eastern Kansas and the local topography. Each meteorologist serving the community has a difficult job in devising a plan that connects this information to an extremely eclectic public in a useful, yet positive way.

References

1 Vasquez,Tim. Storm Chasing Handbook First Edition. Austin TX,:Weather-Graphics Technologies. 2004.
2 Lydolph, Paul E. The Climate of the Earth. Rowman and Littlefield Publishers, Inc. 1989
3 Faidley, Warren. The Ultimate Storm Survival Handbook. Nashville, TN: Rutledge Hill Press. 2006.