Summer 2011 Climate Summary

Central Indiana
Summer 2011 Summary
 
As we begin the month of September, we mark the conclusion of meteorological summer and welcome meteorological fall. The summer of 2011 will go down as one of the hotter summers in recent memory across central Indiana. Indianapolis International Airport reached 100 degrees for the first time in 23 years on July 21st, in the middle of a record 23 consecutive days of 90 degrees or warmer experienced from July 17th through August 8th. The following is a summary of weather conditions experienced in Central Indiana during the months of June, July, and August 2011.
 
A record high temperature of 95 degrees was reached at Indianapolis on June 4. Record high minimum temperatures of 79 degrees occurred on July 19th, 22nd and 23rd. A new daily record rainfall of 2.03 inches occurred on June 20.  Indianapolis experienced its driest July on record with a mere 0.47 inches of rainfall throughout the month.
 
 
Temperatures
 
The summer of 2011 was the 5th warmest summer ever at Indianapolis, with an average temperature of 77.6 degrees. The normal summer average temperature is 73.9 degrees, making this summer above normal by 3.7 degrees. The average temperature of 77.6 degrees was also just 0.5 degrees cooler than the average temperature experienced during the summer of 2010.
 
June
 
June started out quite warm with the first third of the month well above normal as a series of high pressure systems built into the area. Much of the area experienced highs ranging from the 80s to mid 90s and average temperatures more than 10 degrees above normal.  The peak of the heat came on the 4th as temperatures surged into the middle 90s across much of central Indiana. Lafayette, Muncie, and Shelbyville all reached 97 degrees during the afternoon.  Indianapolis had the 6th warmest start to June on record. 
 
The remainder of the month was primarily marked by either below normal or near normal temperatures. Highs predominately remained in the 70s and 80s with lows in the mid 50s and 60s. The coolest periods occurred from the 12th-15th and the 23rd-26th after cold fronts pushed southeastward across the region associated with northeastward-tracking low pressure systems.
 
 
July
 
July 2011 will go down in history at Indianapolis as the hottest month in 75 years since July of 1936 and the 2nd hottest since weather records began in 1871. During the summer of 1936, the Midwest and much of the nation was in the middle of the epic Dust Bowl. A persistent upper level ridge of high pressure is to blame for the prolonged period of heat this July. Every day of the month was above normal for temperatures. Much of the second half of the month was near 10 degrees above normal, when the most intense heat waves impacted the area. Combined with relatively high amounts of moisture in the air, conditions became dangerous and posed a clear threat for those exposed to the excessive heat.  Heat index values consistently ranged from the 100s to 110s across central Indiana during several periods in the second half of the month.
 
Several locations broke into the triple digits on the 21st. Indianapolis reached 100 on this day, which was the first time since August 16th, 1988 (102 degrees). Many locations had impressive strings of consecutive days with maximum temperatures of at least 90 degrees. Shelbyville and Eagle Creek both finished the month with 16 straight days of highs at or above 90 degrees, and Indianapolis had 15. 
 
August
 
The first third of August started out similar to the vast majority of the previous month, which was characterized by above normal temperatures due to a persistent upper level ridge of high pressure. This allowed much of central Indiana to have highs in the upper 80s to mid 90s and lows near 70. On the 8th, Indianapolis International Airport experienced the 23rd straight day with a high temperature of 90 degrees or higher, which topped the previous string of 19 consecutive days of 90 degrees or higher set back in August of 1936. The upper ridge finally broke down and allowed for the first extended period of below normal temperatures in a long time during the middle part of the month. A series of cold fronts pushed southeastward across the area from the 10th to the 17th and resulted in several days where highs dipped into the 70s and low 80s across much of central Indiana.  Lows in the 50s were also a welcomed cool-off.
 
More frequent variations in temperature occurred over the last 10 days of the month as the upper level ridge stayed positioned to the west over the Rockies and multiple rounds of upper level disturbances tracked southeastward across the region. The 26th to the 30th saw temperatures near or below normal before the month ended with a warm note on the 31st as the 90s returned to the majority of the area.
 
 
 
 
Temperature Data for Other Sites in Central Indiana
 
Site
Summer 2011 Temperature
Normal Temperature
Diff. From Normal
Indianapolis Int’l Arpt
77.6
73.9
+3.7
Lafayette
75.8
73.1
+2.7
Muncie
74.4
72.8
+1.6
Terre Haute
75.6
73.4
+2.2
Bloomington
75.0
72.8
+2.2
Shelbyville
75.8
72.7
+3.1
Indianapolis – Eagle Creek
76.4
73.9
+2.5
 
 
Summer Extremes Across Central Indiana
 
Site
Warmest Temperature
Coldest Temperature
Indianapolis Int’l Airport
100 on 7/21
58 on 6/25 and 8/11
Lafayette
101 on 7/21
53 on 6/12
Muncie
97 on 6/4 and 7/21
48 on 8/30
Terre Haute
99 on 7/21
52 on 8/11
Bloomington
96 on 7/21
50 on 8/30
Shelbyville
97 on 6/4, 7/20 and 7/21
49 on 8/30
Indianapolis-Eagle Creek
98 on 7/21
54 on 8/30
 
 
 
Rainfall
 
Overall this was the 22nd driest summer on record at Indianapolis. The total rainfall for Indianapolis this summer was 7.34 inches. The normal rainfall total for summer is 11.93 inches, which made this summer below normal by 4.59 inches.  
 
June
 
Rainfall for June 2011 was above normal in many central and southern areas for the third consecutive month. June rainfall totals ranged from less than two inches to nearly 12 inches. The heaviest rainfall occurred in portions of central, south central, and southwest Indiana. The driest areas were across northeast and east central Indiana.  
Most of the rain activity during the first nine days of June was concentrated around the I-70 corridor and northward. Rainfall of two to more than six inches occurred in several areas across the northern half of Indiana. Lowland river flooding returned to the Wabash River as a result. In contrast, much of southern Indiana received little or no rainfall for the two week period ending at 8 a.m. EDT June 10th and, except for the Wabash River, rivers in central and southern Indiana remained low.
 
During the middle of June, storm activity was frequent in both central and southern Indiana. One of the heaviest rainfalls of the month occurred on the 20th when the Lafayette and Indianapolis areas received two to nearly six inches of rain in less than six hours. Significant flash flooding occurred in the eastern portions of the Indianapolis metropolitan area. Widespread lowland river flooding returned to western and southern Indiana following the rains on the 20th.
 
After the 20th the heavier rainfall activity moved south of I-70. Storms continued nearly each day in southern Indiana. Significant flash flooding occurred in portions of southern Indiana on the 26th when three to possibly more than six inches of rain fell along much of the U.S. Highway 50 corridor. Many areas of southern Indiana south of a line from Terre Haute to Cincinnati received four to 10 inches of rainfall from June 14th through June 27th. The remainder of the month was mostly dry except for during the night of the 30th when storms brought rain to northern portions of central Indiana.
The continuing wet weather during June hampered efforts of Indiana’s agricultural community. Farmers had a difficult time trying to make hay, harvest wheat, and tend emerging crops. Some river bottom farmers replanted some fields at least once and possibly even a second time.
 
July
 
The pattern across the region shifted to a persistent upper ridge of high pressure that prevailed over the central United States for the vast majority of the month. This caused a quick transition from the very wet conditions of the spring to much warmer and drier conditions during the month, with storms being deflected from much of central Indiana all month. Any chances for precipitation usually accompanied a weak frontal passage or stationary front, and any development typically was not widespread across the area. With generally weak wind shear in place, there were not many opportunities for storms to become well-organized or longer-lived.  Indianapolis experienced the driest July on record, with only 0.47 inches of rainfall recorded during the month.
 
As a result of the lack of widespread shower and thunderstorm development, the monthly total precipitation across central Indiana included some notable variation. While most locations were below normal, including much of the central and eastern portions having less than half an inch, some areas to the west and southwest had 5 to 8 inches.
 
 
August
 
The dry rainfall pattern from July continued in many areas through August. Monthly rainfall ranged from a quarter of an inch in portions Sullivan, Knox, and Daviess Counties in southwest Indiana to near 7 inches in Warren, Tippecanoe, Cass and Wabash Counties in north central Indiana.    About one half of the area north of I-74 received normal to above normal rainfall while most areas south of I-74 received much below normal rainfall.   The last time the Indianapolis airport was in a longer and drier period was from July 29 through October 12, 2010.
 
Abnormally dry to moderate drought conditions continued throughout August in much of central Indiana.   After receiving abundant rainfall in July, portions of southwest Indiana saw virtually no rain in August. Significant rainfall continued to fall in portions of Tippecanoe County, an area favored with rain this summer.
 
 
Rainfall Data for Other Sites in Central Indiana
 
Site
Summer 2011 Rainfall
Normal Rainfall
Diff. From Normal
Indianapolis Int’l Arpt.
7.34
11.93
-4.59
Lafayette
14.76
11.53
+3.23
Muncie
9.33
12.34
-3.01
Terre Haute
8.02
12.84
-4.82
Bloomington
9.93
13.30
-3.37
Shelbyville
7.98
12.50
-4.52
Indianapolis – Eagle Creek
9.54
11.84
-2.30
 
 
Major Weather Events
 
The frequency of severe weather events in June diminished to some degree from the number of events experienced across central Indiana during the spring. There were, however, several notable events throughout the month. A squall line developed over northern Indiana on the evening of the 4th and quickly spread southward into the northern portions of central Indiana. These thunderstorms produced hail and damaging winds. These storms caused a tree to fall on a vehicle at Mounds State Park near Anderson causing one fatality and three injuries. Several rounds of storms during the early afternoon of the 10th and the overnight hours produced damaging winds up to 70 mph resulting in downed trees, power lines, and tree limbs. The damage associated with the storm development occurred along the northern portion of central Indiana near a stationary front. The last notable severe weather event of the month occurred during the early morning of the 20th as thunderstorms developed along a weak boundary across the region. The storms continued to redevelop and impact areas from Lafayette southeast through the Indianapolis metropolitan area, Columbus, and Shelbyville for several hours, producing damaging winds, large hail, and flooding rainfall.
 
July proved to be quite inactive with severe weather, as there were only a few occurrences during the entire month. While storm development on the 2nd and 20th resulted in isolated hail and wind damage including some downed trees, the most significant event occurred on the 11th. During the evening of the 11th, a line of scattered thunderstorms developed along a stationary front draped across the northern portion of central Indiana. The storms caused multiple downed trees and power lines along with hail up to 1.75 inches in diameter across some of the northern counties.
 
The most significant severe weather event occurred on the 13th of the month as several lines of scattered thunderstorms pushed southeastward across central Indiana ahead of an approaching cold front. While multiple reports of hail up to 1.75 inches resulted from these storms, the gusty winds were the main impact. Wind gusts over 60 mph brought multiple trees down across the area, and unfortunately caused a stage collapse at the Indiana State Fair Grounds, which tragically resulted in 7 fatalities and over 40 injuries. A review of the severe thunderstorms that occurred on August 13th can be found at http://www.crh.noaa.gov/ind/?n=aug132011svr.
 
For information on severe weather in other areas throughout the summer, visit the Storm Prediction Center “Severe Weather Event Summaries” website at http://www.spc.noaa.gov/climo/online/.
 
 
Fall 2011 Outlook for Central Indiana
 
The official outlook for the 2011 fall season (September-November) from the Climate Prediction Center, indicates a greater chance of above normal temperatures across central Indiana. At Indianapolis, the average temperature for the fall season is 55.2 degrees. An equal chance of above, below or near normal precipitation exists across central Indiana through the summer. At Indianapolis, the average precipitation for the fall season is 9.94” and 1.1” of snowfall.
 
 
 
 
Data prepared by the NWS Indianapolis Climate Team
Questions should be referred to w-ind.webmaster@noaa.gov


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