Monday, July 9, 2012

How Dry I Am...

That loud sound this weekend was that of the heat wave breaking in the eastern half of the U.S.  After days of triple digit record high temperatures in many locations, the upper level ridge shifted west and allowed cooler air to spill south into the nation’s midsection behind a relatively weak cold front. That is the good news. The bad news is that although there were some showers and thunderstorms associated with the front, there were not nearly enough to break the expanding and intensifying drought that grips much of the country.

The map on the left is the 500 millibar map upper air map (about 18000 to 20000 feet up) for the morning July 6 showing the upper level ridge planted over the middle of the country. The map on the right shows the 500 millibar map for this morning.  The axis of the ridge has retreated to the west, and cooler air from Canada is flowing into the central and eastern U.S.
 The July 3rd U.S. Drought Monitor depicted an astounding 76 percent of the lower 48 states in Abnormal Dryness, and 36 percent in Severe Drought or worse.  This is a critical time for agriculture in the corn and soybean belt, as corn is in or approaching the pollination stage. The lack of water and the heat will take a toll on corn yields, and grain prices are already rising as the condition of the crop worsens.  Soybeans can tolerate more heat and have some more time before they reach a critical period of development in August.

In an ironic twist, the High Park fire area west of Fort Collins, CO received two to four inches of rain this weekend, resulting in flash flooding. Debris from the fire was washing into piles creating debris dams, further exacerbating the flooding.  Two weeks ago firefighters were dealing with the wildfire. This weekend they were pumping basements flooded by the rain.

With drought so dominant at this time, we need and appreciate your daily rainfall reports, especially those reports of ZERO. The spotty nature of showers and thunderstorms mean that some locations can receive inches of rain, while a few miles away there's not enough to settle the dust.  

Davidson County, TN rainfall for the morning of July 9, 2012.  Nashville is located near the red dot.
 "0.00" is a measurement- it explicitly states that you measured no rain. No report, on the other hand, leaves everyone guessing.  There have been an impressive number of CoCoRaHS observers regularly reporting rainfall, zero and otherwise.  Below is the map from June 26 when the central U.S. was dry as a bone.

On June 26 there were 9,561 total reports, of which 7,061 were zeroes (gray dots).

So remember, "Be a Hero - Report Your Zero!"

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