July 2004 - a Review of Weather, Temperatures, and Precipitation for the Quad State Region.

 

Weather Summary for July 2004

 

A series of upper level disturbances combined with a couple of weak surface cold fronts to produce several rounds of showers and thunderstorms during the first week of July. Many of these thunderstorms produced brief heavy rainfall with hourly rates in excess of 2 inches per hour. Numerous Flash Flood Warnings and Urban and Small Stream Flood Advisories were issued. Average rainfall amounts were between 1 and 3 inches between the 1st and the 7th but several cooperative observer sites reported in excess of 4 inches.

 

A stationary front across central Illinois and Indiana was the focus for several rounds of showers and thunderstorms between the 10th and 13th. Slow moving thunderstorms produced brief heavy rainfall to parts of the northern half of the area. Again, many of these storms had estimated rainfall rates in excess of 2 inches per hour. The next storm system moved east out of the Central Plains and directly over the area providing a focus for showers and thunderstorms on the 16th and 17th. Many of these storms regenerated and trained over the same areas Friday night into Saturday. Numerous warnings and advisories were issued. Expansive flooding was reported in Vanderburgh County in parts of the city of Evansville. Radar estimated between 8 and 10 inches of rain fell across portions of southwest Indiana during a 12-hour period.

 

More quiet and dry weather settled over the lower Ohio Valley for a few days before a strong cold front approached from the Northern Plains. Several rounds of showers and thunderstorms broke out ahead of the front and in the unstable air behind the front between the 22nd and 26th. Rainfall amounts during this time averaged between 1 and 2 inches. Cold Canadian high pressure then settled over the region providing an early taste of fall. Daily average temperatures between the 25th and 28th were over 10 degrees below normal. A quick moving storm system out of the Southern Plains brought the last round of showers and thunderstorms to the region on the 29th and 30th. Rainfall amounts during this time were less than one inch.

 

July Temperatures Across the Quad State Region

 

The following table (Figure 1) displays average July 2004 temperatures at five locations across the Quad State Region where this information is consistently collected. For comparison, historical average daily temperatures for July are also given for these locations. The Normal period used to calculate normal high, low, and average daily temperatures and rainfall is currently 1971 through 2000.

 

The high, low and average daily temperatures are averaged for all days of July 2004. Column 5 allows a comparison of the July 2004 average temperature to the highest and lowest July average temperatures recorded during the Normal Period (1971 through 2000). High and Low daily temperatures were not compared.

 

The last column indicates the difference of the July 2004 average temperature from the average temperature observed during the Normal Period, and the percentile of the July 2004 mean temperature compared to July mean temperatures during the Normal Period.

 

Percentile is the percentage of years during the Normal Period that had mean July temperatures equal to or below the 2004 mean temperature. In most cases, this is based on the entire 30-year Normal Period, but in some cases data was missing that only allowed comparison to 28 or 29 years of the Normal Period.

 

Figure 1. July Average Daily Temperature Summaries (Degrees F) for Several Quad State Region Locations.

 

 

Location

 

Temp >

 

High

 

Low

 

Mean

 

Range of

Mean Temperatures*

 

Degrees from Mean

/percentile

 

Carbondale

IL

 

Normal >

2004 >

 

88.4

86.5

 

66.4

66.6

 

77.7

76.6

 

max: 81.3 in 1980

min: 74.6 in 1984

 

-1.1

41%-ile

 

Cape Girardeau

MO

 

Normal >

2004 >

 

90.1

86.3

 

69.5

66.7

 

80.1

76.5

 

max: 83.6 in 1993

min: 76.0 in 2000

 

-3.6

9%-ile

 

Evansville

IN

 

Normal >

2004 >

 

88.8

84.3

 

68.3

66.5

 

78.6

75.4

 

max: 83.1 in 1993

min: 75.1 in 1996

 

-3.2

8%-ile

 

Paducah

KY

 

Normal >

2004 >

 

89.4

85.7

 

69.1

66.5

 

79.5

76.3

 

max: 84.2 in 1993

min: 75.7 in 1971

 

-3.2

8%-ile

 

Poplar Bluff

MO

 

Normal >

2004 >

 

91.2

86.3

 

69.4

68.8

 

80.6

77.9

 

max: 74.0 in 1980

min: 73.0 in 1992

 

-2.7

7%-ile

* Range of averages is taken from the range used to calculate normals: 1971-2000.

 

As this Figure 1 indicates, temperatures across the Quad State Region for the month of July were all below normal. Carbondale was the warmest of the five, at 1.1 degrees below normal ranking in the 41st percentile.

 

The other four locations ranged from 2.7 degrees below normal at Poplar Bluff to 3.6 degrees below normal at Cape Girardeau. The temperatures at all four locations ranked below the 10th percentile. Overall, July 2004 was near record low temperatures at most locations.

 

July Precipitation Across the Quad State Region

 


The next table (Figure 2) displays normal precipitation and the observed precipitation for July 2004. The historical time periods are the same as those in Figure 1. Frozen precipitation if any is not available from this data except as liquid equivalent, which is included in the total precipitation for the month.

 

Figure 2. July 2004 Observed Precipitation and Normal July Precipitation (inches) for Several Quad State Region Locations

 

 

Location

 

 

Total

Precip.

 

2004

diff

 

Range*

(within normal period)

 

%-ile

 

 

Carbondale, IL

(well above normal)

 

Normal > 2004 >

 

3.29

4.31

 

 

1.02

 

max: 7.34 in 1981

min: 0.54 in 1974

 

79

 

Cape Girardeau, MO

(well above normal)

 

Normal > 2004 >

 

3.50

3.84

 

 

0.34

 

max: 8.39 in 1971

min: 0.63 in 1999

 

73

 

Evansville, IN

(well above normal)

 

Normal >

2004 >

 

3.75

7.56

 

 

3.84

 

max: 8.40 in 1992

min: 0.18 in 1974

 

92

 

Paducah, KY

(well below normal)

 

Normal >

2004 >

 

4.45

1.75

 

 

-2.88

 

max: 12.47 in 1972

min: 0.28 in 1999

 

18

 

 

Poplar Bluff, MO

(well above normal)

 

Normal >

2004 >

 

3.82

6.37

 

 

2.55

 

max: 11.97 in 1988

min: 0.57 in 1983

 

92

* Range is the highest and lowest July precipitation observed within the Normal Period

(1971-2000).

 

As Figure 2 indicates, rainfall for July was well above normal for all locations except Paducah. Precipitation at these locations ranged from 0.34 inches above normal at Cape Girardeau to 3.84 inches above normal at Evansville. Percentiles ranged from 73 to 92, respectively.

 

At Paducah, precipitation was 2.88 inches below normal, ranking in the 18th percentile.

 

Overall, July 2004 was relatively wetter than normal.


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