Why Hurricane Dennis failed to save the beans. | DocWeather: New Climate Research

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Why Hurricane Dennis failed to save the beans. - 08.03.05

The failure of rains in the Corn Belt will have a strong effect on corn and soybean harvests this year.

A dominating feature of summer rain events in the Midwest is the Low Level Jet. The jet is a flow of air that comes northward from the Gulf of Mexico into the Midwest bringing moist warm air into the Corn Belt. The warm moist air mixes with cooler air from western Canada and produces thunderstorms that keep the corn and soybeans growing. The Low Level Jet (LLJ) is part of the American monsoon, a summer rainfall pattern that is unique to the United States. The failure of this monsoon is the cause of drought for the High Plains , the Corn Belt and the Central States.

Fig.1

This year, an unusual event promised to break a drought pattern for what are known as the three I's of the Corn Belt. The three I's are Iowa, Illinois, and Indiana. These three states have been the focus of a strong drought going back to May of 2005. The current status of the drought is focused on these states as well as parts of Missouri. The weather pattern that has supported this drought is the placement of a persistent blocking ridge over the southern High Plains (figure 1) that squeezes up into the Northern High Plains and blocks the passage of storms from the northwest into the three I's. The LLJ in this case does not bring up moisture because the ridge blocks the necessary south to north circulation from the western Gulf of Mexico.

Fig.2

This year hurricane Dennis got past the ridge during the passage of a low across the northern sections of the three I's. The trough moved across the Great Lakes as the hurricane approached the Gulf coast. This was a break in the ridge that the storm used to track up into the Midwest. However, as the storm rose into the Midwest on the 10th it ran into a strong surge in high-pressure on the continent. The storm quickly dwindled into a tropical depression but it had brought a lot of moisture northward with it. The hopes for Midwest farmers were that the storm would trigger widespread rains. Unfortunately the rains fell to the east of the drought area. This was because on the 12th a strong high-pressure surge built up the ridge over the southern High Plains. The high was linked to a motion in arc event for the lunar node at 23�° Pisces. This event put high-pressure values on the 45�° jet curve(green) from that point. A high grew over the eastern Gulf of Mexico that blocked the eastward motion of the slowly diminishing storm. Unfortunately on the same day Jupiter was active on the Pacific eclipse points also to high-pressure values. This put strong high-pressure on the 72�° jet curve (blue) from the Pacific pair of points. This surged the high over the High Plains. The surging high pushed eastward to block the entrance of the LLJ from the western Gulf of Mexico. The decaying hurricane was then locked into an area between the ridge to the west, and block off of the southeast coast. With no input of fresh moisture from the south, the storm circulated over parched fields in the Central States building thunderheads but very little precipitation fell over the Corn Belt. Most of the moisture ended up in the Ohio Valley.

The lack of rain has now become critical for the three I's states and Missouri. This does not look like it will abate in the near future since the nearest weather producing planetary influence will be around the 12th or 14th of August. This will probably be too late for the heat stressing of the crops that is now taking place.