xt74mw28bb96 https://exploreuk.uky.edu/dips/xt74mw28bb96/data/mets.xml   Kentucky Agricultural Experiment Station. 1965 journals 157 English Lexington : Agricultural Experiment Station, University of Kentucky Contact the Special Collections Research Center for information regarding rights and use of this collection. Kentucky Agricultural Experiment Station Progress report (Kentucky Agricultural Experiment Station) n.157 text Progress report (Kentucky Agricultural Experiment Station) n.157 1965 2014 true xt74mw28bb96 section xt74mw28bb96 _ LONG-TIME PRECIPITATION PATTERNS: A GUIDE FOR OUTDOOR PLANNING
1. VICINITY OF HOPKINSVILLE, KENTUCKY
By A. B. Elam, Jr.,1 and T. H. Taylor2
Farmers, building and road contractors, homeowners, and others consider
probability information concerning rainfall, temperature and other weather elements
since they remember in a general way what happened in the past. Those who wish
to give closer attention to scheduling field and other outside operations to take
' advantage of rainfall patterns may find the information in this report very helpful.
On the average, the Hopkinsville area receives the smallest amount of pre-
cipitation in the months of August through October and the largest amounts in January
and March (Fig. 1). It is apparent, however, that, in planning some kinds of outdoor
work, weekly data would be more useful than seasonal or monthly averages. By
studying statistically many years of precipitation data for this area, we can estimate
the chances of receiving certain amounts of rainfall in a given weekly period.
Left of the dividing line in Table 1 are figures showing, for each week of the “
year, the average weekly precipitation and the maximum precipitation that has
occurred for that week. The precipitation average for any week is an arithmetic
average of 60 weeks for the period 1901-60. For example, the week of January 17-23
gets an average of 1.57 inches of precipitation, and there has been as much as 13. 59
inches during these 7 days. In the 60 years of record, there were 6 times that
precipitation was less than 0.01 inch (trace or 0), and for the remaining 54 weeks,
the measurable weekly totals were from 0.01 to 13.59 inches.
Barger and Thom's (1) method of obtaining estimates of probabilities of pre-
cipitation has been used in this study. The probabilities obtained are listed on the
right-hand portion of Table 1 under "Percent Chance." Listed for each week are
the probabilities of having less than specified amounts of precipitation. For example,
for the week of March 1-7, the probability is 62 percent that the amount of precipitation
will be less than 1.00 inch and 10 percent, or 1 chance in 10, that there will be no
measurable rainfall (trace or 0), To state it another way, the probability is 38 per-
cent (100-62) that the precipitation will be 1. 00 inch or more.
Data from the 0.60 inch and 1. 00 inch columns in Table 1 were plotted in Fig.
2. In this case, the probabilities are for 0.60 or more,_ and 1.00 inch or more. The
. curves were drawn for 3—week running means to minimize the effect of random variations
from week to week and to present the longer period pattern. This method smooths short
period singularities -- wet or dry periods which tend to occur during or near a partic-
ular week more frequently than chance would indicate.
The precipitation probabilities have a number of possible applications. The
relatively drier period in late January and early February could be used for prepara-
tion of tobacco plant beds; for seeding clovers and grasses; and for the timely appli-
cation of fertilizers. The probable occurrence of a dry period in April would indicate
ll/Veather Bureau State Climatologist.
2Associate Professor, Agronomy Department, University of Kentucky.
- Progress Report 157
UNIVERSITY OF KENTUCKY zz AGRICULTURAL EXPERIMENT STATION
· Department of Agronomy
Lexington

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AVERAGE TEMPERATURE
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JAN.EE1s. MAR. APR. MAY JUN. JUL. AUG. sER. OCT. NOV. 0Ec. ‘·
5
AVERAGE PRECIPITATION
Q 5 Annual: 47.52 inches
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JAN.EEs. MAR. APR. MAY JUN. JUL. AUG. SEP. OCT. NOV. DEC.
Fig. 1. -- Average monthly temperature and precipitation for Hopkinsville, Ky.,
iszi-00.

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Table 1 — Weekly precipitation (inches) at Hopkinsville, Kentucky, 1901-60
WEEK év `$@°Q §~ PERCENT CHANCE
· BEGINNING Q'? O. C‘$2° 9 TRACE LESS THAN
MO. DAY {§b '§g§  €§& 0 0.20 0.40 0.60 0.80 1.00 1.50 2.00
Mar. 1 .93 6 4.47 10 22 34 46 55 62 80 86
8 1.26 3 4.60 5 13 26 35 45 53 69 81 ‘
15 1.04 4 5.27 7 21 32 46 56 62 76 85
22 1.13 5 3.81 8 17 31 40 50 56 72 83
29 1.05 3 6.45 5 19 31 43 53 59 76 86
Apr. 5 1.14 4 5.28 7 18 28 40 49 58 72 84
12 1.03 5 4.53 8 21 34 42 54 61 76 85
19 .71 2 2.47 3 22 40 54 67 76 90 96
26 1.05 6 6.00 10 21 30 39 50 56 72 83
May 3 1.01 8 4.30 13 24 36 46 54 63 76 85
10 .84 8 3.35 13 26 38 51 59 68 82 90
17 .99 3 8.15 5 28 45 50 58 65 78 86
24 .92 10 4.66 17 29 41 49 57 67 78 87
31 1.03 8 5.45 13 27 39 49 55 62 74 84
June 7 .83 9 3.45 15 28 42 52 62 71 83 90
14 .95 9 5.47 15 28 38 46 55 64 78 87
21 .90 8 5.77 13 28 39 51 59 65 81 87
28 1.02 12 5.57 20 32 40 48 56 62 75 83
July 5 .79 11 5.39 18 39 51 62 66 75 84 89
12 .96 13 3.80 22 29 37 47 57 63 77 87
19 .69 9 4.78 15 38 52 60 70 75 86 92
26 1.05 10 6.52 17 27 41 48 53 60 74 83
Aug. 2 .84 8 4.20 13 26 39 53 60 67 81 89 .
9 .95 11 3.62 18 32 42 52 60 65 78 85
16 .86 10 4.25 17 39 50 60 64 70 79 86
23 .55 16 2.53 27 45 54 66 72 81 90 95
30 .72 14 3.98 23 40 51 61 66 73 84 90
Sept. 6 .70 11 2.90 18 34 47 59 65 72 85 91
13 .53 19 3.83 32 52 62 70 76 81 89 95
20 .71 18 3.80 30 42 52 60 66 72 83 91
27 .70 19 5.30 32 47 56 66 70 74 85 91
Oct. 4 .86 13 6.05 22 41 50 57 63 69 79 88
11 .56 20 3.57 33 49 59 68 72 79 88 93
18 .66 19 3.17 32 45 51 61 69 75 86 92
25 .59 17 3.51 28 42 55 66 74 79 90 95
Nov. 1 .84 14 4.07 23 35 43 52 60 65 80 88
8 .89 12 6.28 20 32 44 53 61 68 80 88
15 1.07 14 10.47 23 39 47 51 59 65 75 81
22 .79 7 4.70 12 28 43 54 63 71 83 90
29 .77 12 4.05 20 33 46 55 64 71 83 90
Dec. 6 1.02 10 4.82 17 27 36 45 53 61 75 86
13 1.17 10 6.92 17 30 39 47 54 61 71 80
20 .95 11 6.20 18 33 44 53 62 65 78 86
27 1.11 2 3.98 3 17 29 38 49 58 75 84
Jan. 3 1.07 12 6.33 20 31 41 48 55 60 74 81
10 1.04 9 6.33 15 28 36 46 55 62 75 85
17 1.57 6 13.59 10 24 33 37 43 51 61 70
24 .93 8 6.19 13 31 45 54 60 65 77 85
31 .92 6 4.82 10 30 39 51 57 65 78 87
Feb. 7 .76 10 2.69 17 23 35 50 60 69 87 93
14 1.09 6 6.29 10 22 34 42 52 60 74 84
21 1.02 5 4.78 8 24 35 45 53 61 77 85

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that seeding of legumes well in advance of this period would enhance the chances n
of success. The April dry spell would also be a good time for planting corn since
the ground would be in shape for operation of machinery. Experience and experi-
mental evidence indicate that higher yields often come from earlier planted corn.
One of the farmer's problems is the competition for available labor in May.
By taking care of the tasks noted above in April he would be free to use available
labor to accomplish in May those tasks which should be done then for best results.
For example, the highest quality grass hay may be obtained from a cutting in early
" May; and the best quality and heaviest crop of alfalfa and clover hay may be
obtained from a cutting in mid-May; tobacco transplanting from beds to fields —
usually takes place between May 15 and June 1. _
It is apparent that some of the drier weeks of the year occur during late `
August to late September. This indicates that seeding of alfalfa immediately prior ·
to, or during this period, would have less chance of success unless supplemental
irrigation is available.
The foregoing are a few of the possible applications of precipitation proba-
bilities. Others will become apparent to those who inspect the table and graphs -
with particular problems in mind.
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152212 261024 721 519 216301327
JAN eee MAR APR MAY JUN JUL AUG sep Ibc;5 Bmog been
DATE EACH WEEK seems
Fig. 2. -- Percent chance of weekly precipitation of 0.6 and 1.0 inch or more,
Hopkinsville, Ky., 1901-60.

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R The probabilities listed in this report are based on past data but are the
best estimate of what the rainfall will be for use in long-range planning several
months or years ahead. Five-day outlooks and the daily forecasts should be used
when short—range plans are of concern.
l REFERENCE
1. Barger, G. L., and Thom, H. C. S., "Evaluation of Drought Hazard," Agron. ·
Journal 41:519-526. 1949. ‘
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