It
has been a brutally hot summer from the Midwest to the southern Plains. Add to this the lack of rainfall and you have
the recipe for a devastating drought.
What was expected to be a record year for corn is likely to be the worst
in decades. The drought expanded quickly
as all-time record highs were being set; some dating back to the Dust Bowl.
Look
at two cities caught in the heat wave and drought. Oklahoma City has endured 28 days from late
June to mid August of 100 degree temperatures.
St. Louis has recorded 21 days during the same period. Both cities tied their all-time record high
temperatures at some point during the heat wave.
Now
Mother Nature is about to give the central and eastern parts of the country a
break from the heat. A low pressure is
going to develop aloft and become centered just south of Hudson Bay by early
next week. As the map below shows winds
in the upper atmosphere will dip south into the U.S. bringing a cooler Canadian
air mass. If this were winter there
would be talk of a cold wave, but this is summer and we will call it
refreshing.
The forecast for winds at 500 mb (about 18,000 ft) for Monday, August 20, at 18z. Click on the image for a larger view for all of the graphics. Image Credit: NOAA/NCEP. |
The
6 to 10 day outlook from the Climate Prediction Center shows a rather high
chance of cooler than normal temperatures for this time of year for the period
of August 19th through the 23rd. The coolest air will be centered over the
upper Midwest.
The 6 to 10 day temperature outlook for August 19-23. Image Credit: NOAA/CPC. |
This
will be welcome relief from the heat, but there will only be a limited amount
of rain. Thus, the drought which now
covers about 70% of the contiguous U.S. will likely continue unabated. About 52% or about half of the country is
rated in a moderate drought or worse.
US Drought Monitor as of August 7, 2012. Drought classes are incipient, moderate, severe, extreme, and exceptional. Image Credit: USDA. |
Record
heat helped drive moisture out of the ground and the evaporative stress index
showed the areas of greatest water needs.
It has been persistent over the past three months leading to the flash
drought over much of the Midwest. Much
of Oklahoma and western Texas were still recovering from last year’s heat wave and
drought. Their drought never ended, but
persisted for a second year.
Image Credit: USDA. |
There
has been more rain over parts of the Southeast during the past couple of
months. In fact two tropical storms
brought much of northern Florida and southeast Georgia out of drought. This has been replaced with heat, humidity,
and lots of mosquitoes in those areas.