"Tornado Alley Shifts East This Spring"
I expect the spring of 2013 to bring the heart of severe weather into the Midwest and eastern Plains, away from its usual spot in the central and southern Plains. It's time to review the logistics behind this forecast.
This drought plays a significant role in severe weather (and storms in general). When storms go over land, they drop moisture as precipitation and ingest moisture as evaporation, pretty much a give-and-take. However, if the area the storm is going over is in a drought, there is no evaporation to pump more moisture into the system. As a result, precipitation output is reduced, and the storm weakens overall. This does pose a problem as far as getting storms going for the upcoming spring, and this is the basis of something called a baroclinic zone. The term baroclinic zone defines an area of temperature gradient across an area, commonly a zone where storm formation is enhanced. If we apply the baroclinic zone to this situation, we find that the zone would most likely attempt to form in the Midwest, particularly in Wisconsin, Iowa, Illinois, Missouri and Arkansas. This baroclinic zone will form as a result of warmer temperatures in response to a lack of moisture from the drought- the lack of evaporation from the drought-stricken land refuses development of clouds and precipitation, continuing a vicious cycle that enhances the drought and baroclinic zone.
Now, I personally believe this baroclinic zone does not apply to temperatures. While the term 'baroclinic' may only refer to temperatures, there is no doubt that a moisture gradient is another, equally significant piece in the puzzle. This moisture gradient would form in the same states mentioned in the above paragraph, again in response to very dry land versus relatively dry/average precipitation land. This new moisture baroclinic zone is essentially a synoptic-scale dryline. For those unfamiliar with the term, a dryline is the separation of dry air and humid air. It is commonly found in west Texas, along the desert lands and non-desert lands. This is commonly a focal point for intense thunderstorms as well. I have little doubt that, unless several weeks of persistent rains strike the Plains, these two gradient zones will become key players in the formation and development of thunderstorms and severe weather in the Midwest and southeast Plains.
Here is my forecast for the 2013 Severe Weather Season:
Any questions you have can be asked below. No guarantees I will answer the long ones, so try to keep them brief.