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LocaL Weather History: July 1875 & the Pattern Behind It

July 1875 saw historic flooding in the area with rounds & rounds of heavy rainfall & severe storms. This gives you an idea of the pattern behind it.

Posted: Jul 25, 2018 4:12 PM
Updated: Oct 9, 2018 2:38 PM

For more information on the unusual weather of July 1875:

Check out the rainfall totals for the historically wet month of July 1875:

Here is a brief statement regarding the excess rainfall in our region (from the U.S. Weather Bureau at the time) in their monthly review:

Omega is vertical motion in the lower atmosphere.  Here, we can see at upper levels, a band of anomalous lift occurred in July 1875 from Colorado & northern Indiana to Michigan.  A band of anomalous LACK of vertical motion or lift occurred south & southeast of the area.

Mid-level omega is more pronounced & farther south, while there is an unusual LACK of vertical lift or Omega in the mid levels in the Tennessee Valley.

Low-level lift is plotted in a band from northern Texas to northern Indiana & Michigan.  Lower than normal vertical motion was found Texas to Kentucky to New Jersey.

Omega near the surface was focused in the same general zone of vertical motion elsewhere in the lower atmosphere:  across our region & southwestward with a bulls-eye of lack of surface Omega in the Tennessee Valley.

An anomalous area of CAPE (storm energy) was found over & near the zone of strong vertical motion in the region, in general.

Above normal precipitable water (water to wring out like a sponge) was found feeding northward, in general.

Anomalous band of unusually higher rainfall rates were in a band over numerous state near/in the area, in general.

Flow overall is very, very bunched up & extremely loopy in reviewing July 1875, as a whole.  All the colors indicate unusual, anomalous trough & ridges, compared to modern-day averages for July.

Note the big red bulls-eye in the Atlantic & the large area of yellow & orange with it & then the yellow/orange in eastern Canada.  This is a large, significant blocking ridge that acted as a bottleneck on a stream & stall the pattern & keep the same areas getting the heavy rainfall. 

Also, that red bullseye was near the center of the Bermuda high.  This subtropical high is permanent in the summer & acts as a humidity/moisture pump to bring tropical air & daily storms to the southeastern U.S.  It also feeds storms in the Midwest.  HOWEVER, it should NOT be that far north & west.  That is unusually far north & west for it & it is stronger than normal according to July 1875 reconstuctions.  In the great Flood of 1993 in the Central & Northern Plains & parts of the Corn Belt, a key to the historic event was the misplaced & stronger than normal Bermuda high, in addition to similar blocking.  If it is too far to the west, it can bring drought to the southeastern U.S.

In it being very expansive & strong in July 1875, it led to a record-dry July in Mississippi, Alabama to Georgia & even the Carolinas (less than 1" of rainfall in the wettest month of the year [some areas <0.30" rainfall]).

So, bottom line is that a block allowed front to stall over the area as the center storm systems pass to our north & northwest.  The position of the Bermuda high allowed higher amounts of moisture to be pulled northward.  The loopy jet pattern led to cores of strong winds aloft that helped to organized severe storms.

This pattern occurred after an overall wet April to June, resulting in a culmination of historic flooding by late July to early August.

Blocking also shows up in the surface temperature pattern.  Notice the above normal temperatures to our northwest & northeast with ridging & the southeastern U.S. ridging resulting in the hot, dry weather there.  Notice the bottleneck of below normal to normal temperatures in the middle where more continuous rain fell.

Surface low tracks in July 1875 are below.  Storm systems would pass to our northwest & their front would constantly get hung up here in our region of the country, resulting in heavy rainfall & overall stormy weather.


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