Friday, July 27, 2012

How Could the Drought Be Broken?

click to enlarge
From the USDA and National Weather Service the above map depicts the amount of rain needed to break the drought in a given climatological district.

Is there any short term (i.e., next ten days) hope for widespread relief? Unfortunately, no. While there will be periodic thunderstorms, they are not expected to cause widespread soaking rains. Here's why.

We have been dominated by a high pressure system in the upper atmosphere above the Plains and Midwest all summer. That is not unusual. What has been unusual is the strength of the high. There is no indication of the high breaking down in the next eight days. It might scoot a little farther west weekend after next which would allow some relief in the Midwest but it would be temporary.

So, what might cause widespread relief in the medium term?

Our best hope is for a Pacific hurricane or tropical storm to come ashore along Mexico's west coast and have its moisture transported into the Plains and interact with a cold front or existing low pressure center.
In the scenario above, widespread three to seven inch rains would be typical. If the system were to stall, amounts would be even heavier. These rains would be of the soaking variety.

There is nothing like this on the horizon. If it were to occur, it would be sometime from the last week of August to about the first week of November. This is something that occurs in the Plains about once every eight to ten years.

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