America’s Heat Wave

National Outlook:

Figure 1. 12Z 8/6/2011 position of 500mb ridge across the southern U.S.

Much of the south and southeast continues to bake underneath a strong ridge of high pressure that has stayed pretty much stagnant over the past few weeks.  See my “Terms & Concepts” to get a better understanding of what a ridge is.  Basically, a ridge is a broad region of sinking air or a deep warm air mass that caps off chances of precipitation. This phenomenon is actually common in the summer time.  However, this year the ridge is exceptionally stronger that previous years.  As the seasons chance, so does the jet stream.  During the summer time, the jet stream is usually located across the Northwest, Northern Plains, and the Northeast.  This usually leaves a ridge of high pressure for the central and southern U.S.   At one point this summer, the highest height at 500mb was about 600+ decameters (dam)!  That is quite rare.  Right now, though, the highest height at 500mb seems to be around 594dam (image above).

There is some relief for some people living in the south as this mid-level ridge begins to weaken and shift further west over the next few days.  The closer December gets, the further south the jet stream will dip, thus cooler temperatures.  Here is a general view of the location of the jet stream for both summer time and winter time, respectively, in the northern hemisphere:

Figure 2. Looking down at the north pole showing general location of the jet stream during the summer in NH. Courtesy of NOAA

Figure 3. Looking down at the north pole. Jet stream shifts south and intensifies during the winter time in the NH. Courtesy of NOAA

Figure 4. General idea of what the ridge has been doing this summer. Provided by the NWS.

Facts So Far This Summer (As of 8/6/2011):

Oklahoma City, Oklahoma:

  • 8/6/2011 marks the 12th day of this year that OKC has reached at least 109°F.
  • 67th consecutive days of 90+°F, only 5 days shy of breaking a record.
  • 7 straight days of 105°F for daytime highs in OKC (record).

Dallas, Texas:

  • 43 days of 100°F this year, 36 consecutive days.
  • Average temperature in the last 30 days:  102.8°F.
  • Have broken the record high temperature for the first 5 days of August.

Waco, Texas:

  • 54 days of 100°F this year, 37 consecutive days.
  • Average temperature in the last 30 days:  103.7°F.
  • Have broken the record high temperature for the first 5 days of August.

Wichita, Kansas:

  • 24 days in July with 100+°F, 36 total days in 2011.
  • Average high temperature in July: 102.5°F.

Fort Smith, Arkansas:

  • July 2011 was the warmest (91.2°F) and the 7th driest (.22″) July since records began in 1883.  July 2011 was the warmest month ever on record.
  • Fort Smith reached or exceeded 100 degrees on 30 out of 31 days in July 2011, which sets the record for the total number of 100 degree days in the month of July. Fort Smith ended July having reached or exceeded 100 degrees for 27 straight days, smashing the previous consecutive 100 degrees record of 17 that ended 7/26/1934.

A few of the record highs of 110+ degrees on Friday, 8/5/2011: Oklahoma City, 110; Tulsa, OK, 112; Fort Smith, AR, 113; Wichita Falls, TX, 110.

The list goes on and on with these record shattering statistics.

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About Brian

University of Oklahoma graduate with a degree in Meteorology. Follow me on Twitter: @WeatherInformer
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