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Group Title: Mimeographed report - University of Florida Sub-Tropical Research and Education Center ; no. 71-1
Title: Preparation and use of hourly predicted temperatures on cold nights
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Permanent Link: http://ufdc.ufl.edu/UF00067782/00001
 Material Information
Title: Preparation and use of hourly predicted temperatures on cold nights
Series Title: Mimeographed report
Physical Description: 5 leaves : ; 28 cm.
Language: English
Creator: Orth, Paul G
Sub-Tropical Experiment Station
Publisher: University of Florida, Institute of Food and Agricultural Sciences
Place of Publication: Homestead Fla
Publication Date: 1971
 Subjects
Subject: Crops -- Effect of temperature on   ( lcsh )
Climate -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: Paul G. Orth
General Note: "November 30, 1971."
Funding: Mimeographed report (Sub-Tropical Experiment Station) ;
 Record Information
Bibliographic ID: UF00067782
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 72438461

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HISTORIC NOTE


The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
(EDIS)

site maintained by the Florida
Cooperative Extension Service.






Copyright 2005, Board of Trustees, University
of Florida




n27


".- -


MIMEOGRAPHED REPORT SU


I


'G P 7'K Al


371-1


nstiti
r icu


November 30, 1971


University of Florida
ute of Food and Agricultural Sciences
Itural Research and Education Center


18905 S. W. 280 Street UNIVERSITY OF FLORIDA
Homestead, Florida 33030 AGRICULTURAL RESEARCH
AND EDUCATION CENTER
Preparation and Use of Hourly Predicted 18905 S. '. 280th STREET
Temperatures on Cold Nights HOMESTEAD, FLORIDA 33030


Paul G. Orth

Introduction

Two ways of observing the temperature drop on cold nights are described. The first
method requires preparation of a set of predicted hourly temperatures for each cold
night. It should be useful as a supplement to information available in the Lakeland
forecast. The second method uses hourly temperatures for a typical cold night as a
basis for comparison with temperatures during the night being observed. Both methods
can be used in individual fields, groves, and dooryards.

Method 1

Information necessary before using the first method is:
(1) the maximum temperature in the afternoon preceding the cold night,
(2) the forecast minimum temperature, and
(3) a table of departures.
The maximum temperature can be read from one's own thermometer or it can be obtained
from the Agricultural Research and Education Center, Homestead after 4 PM. The
forecast minimum can be taken from the Agricultural Weather Forecast from Lakeland.
(Use the middle of the forecast range; that is, if the Lakeland forecast is for 30
to 340 use 320 as the predicted minimum temperature.) Table 1 is the needed table
of departures.

Example 1 shows how a table of predicted hourly temperatures is prepared. First,
the difference (C) between the afternoon maximum temperature (A) and the Lakeland
forecasted minimum temperature (B) is calculated. (A minus B equals C.) In Example
this difference is 280F.


Second, the
is located.
next to the


column in Table 1 headed 28 (maximum minus forecasted minimum temperature)
The numbers in this column are copied (to give column 2 in Example 1)
column of hours from 5 PM to 7 AM (column 1).


Third, the Lakeland forecasted minimum is added in turn to each of these departures
to give a column of temperatures predicted for each hour during the night (Column 2
plus Lakeland forecasted minimum gives Column 3 in Example 1). These are the hourly
temperatures likely to occur if the minimum temperature will be the same as that
forecast by Lakeland.

Temperatures read from a thermometer each hour (column 4, Example 1) should be com-
pared with the predicted hourly temperatures. This is done by subtracting the pre-
dicted temperature in column 3 from the actual temperature in column 4 and writing
* the answer in column 5. If the predicted temperature is higher than the thermometer
reading the difference is negative meaning that the air is cooling more rapidly than
predicted, and the trend is toward a minimum lower than the forecast.





-2 -


EXAMPLE 1

Maximum temperature (A:
Forecasted Minimum (B:
difference (C)

CHART


Column 1
Time


5 PM
6
7
8
9
10
11
12
1 AM
2
3
4
5
6
7


2
Departure


25
21
17
13
11
9
8
7
6
6
4
3
2
2
1


3
Predicted
Temperature

54
50
46
42
40
38
37
36
35
35
33
32
31
31
30


4
Observed
Temperature

49
46
44
42
41
41
40
40
39
38
38
37
35
33
35


5
Difference


-5
-4
-2
0
1
3
3
4
4
3
5
5
4
2
5


GRAPH


Difference


8 10 12


2 4 6


TIME


57
29
28 = A-B


8o


















.1 __________________.


4 6


I





- 3 -


In Example 1 the early trend was for a minimum colder than the 290 forecast by
Lakeland. After midnight the trend was fora minimum warmer than the 290 forecast.
* The average trend after midnight was about 4 warmer. Adding 40to 290 shows the
trend was for a minimum temperature of 330. (The minimum during the night at the
observation site was 330.)

The numbers in column 5 can be plotted as shown on the bottom of Example 1 to help
one see the trend.

Not only can the numbers in column 5 be used to update the forecast minimum as shown
above, but they can be used also to determine approximately what time some higher
temperature will be reached. Perhaps a grove owner will want to start sprinkler
irrigation when the temperature reaches 370F. In Example 1 this temperature was
predicted to be reached at 11 PM. At 10 PM the temperature was 30 warmer than
predicted. Adding 30 to the predicted temperatures gives a new prediction of 370
between 2 and 3 AM. The slight warming trend continued and 370 was reached by 4 AM.

Method 2

The second method requires no preparation ahead of time. The only information needed
before temperature readings are made is the "Alert" temperatures given in Example 2.
These Alert temperatures are the hourly temperatures on a typical cold night with a
minimum of 350F. Each air temperature reading made in the yard, field, or grove can
be turned into a prediction of the minimum temperature for the next morning. The
temperature in column 2 is subtracted from the actual temperature (column 3), and the
difference is recorded in column 4. These numbers show the temperature trend relative
to a minimum of 35. After midnight the trend was fairly steady and indicated a
Minimum temperature 2 or 30 less than 350, namely, 32 to 330.

This method can also be used to predict the time when a temperature higher than the
minimum will be reached. For example, try to predict when 370 will be reached by
using the difference temperatures in column 4. From the trend during the early
evening one might predict a minimum 60 less than 350. (The difference started at
100 but declined slowly as time went on, and -6 is a conservative estimate of the
future trend.) Add 60 to the temperature, 370, for which we want to predict the
time of occurrence. The total is 430 which in the Alert temperature column (#2)
should occur at midnight. Therefore, midnight becomes the time predicted for a
temperature of 37. By 11 PM one can see the numbers in the difference column have
continued to decrease. One can revise his time prediction as follows: 35 plus 4
equals 39, and 370 will be reached about 4 AM (the time 390 appears in column 2).

The procedure is:
(1) add the trend shown in the difference column to the temperature for which
you want to predict the time of occurrence, (if the difference has a minus
sign, the number should be added, if it does not have a minus sign it
should be subtracted) and,
(2) look for the temperature given by this addition in the Alert temperature
column. The time next to this temperature is a conservative estimate of
the time you wish to predict.

The trend shown in the example of a typical cold night is fairly easy to see. The
trend will be more difficult to determine on cold nights when the weather changes
* because of the passage of a cold front or a shift in the wind. As a result it will
be harder.to predict temperatures several hours in advance. Forecasts from the
National Weather Service should help one anticipate such changes and compensate
for them.






-E 4 -




EXAMPLE 2


Column 1
Time


5 PM
6
7
8
9.'
10
11
12
1 AM
2
3
4
5
6
7


2
Alert
Temperature

59
56
52
49
46
45
44
43
42
41
40
39
38
37
35


3
Observed
Temperature

49
46
44
42
41
41
40
40
39
38
38
37
35
33
35


4
Difference


-10
-10
8
7
5
-4
4
3
3
3
2
2
3
4
0


(This report is based on "Prediction of Hourly Temperatures
on Cold Nights for Inland Dade County, Florida" by P. G. Orth
and J. T. Bradley in Proceedings of the Florida State
Horticultural Society Vol. 84, 1971.)


. i






-5-


TABLE 1

Hourly Departures from the Minimum Temperature for Cold Nights
Inland Dade Co., Florida (OF)


Tin


7


i0

12
1
2



L
E


Tin




1I
iC
11
12


3t
4t


7


Max-Min* 25 26 27
ie
PM 22 23 24
S19 20 21
16 16 17
12 12 13
S10 10 11
8 9 9
7 8 8
6 7 7
AM 6 6 6
5 5 5
4 4 4
3 3 3
S2 2 2
S2 2 2
1 1 1



Max-Min* 36 37 38
se
5 PM 32 33 33
6 27 28 29
22 23 24
17 18 18
S14 15 15
S12 12 13
i 10 11 11
9 10 10
AM 8 8 9
7 7 8
6 6 6
S4 4 5
5 3 3 3
6 2 2 2
2 2 2


28 29 30

25 26 26
21 22 23
17 18 19
13 14 14
11 12 12
9 10 10
8 8 9
7 8 8
6 7 7
6 6 6
4 5 5
3 3 4
2 2 2
2 2 2
1 1 1



39 40 41

34 35 36
30 30 31
24 25 25
19 19 20
16 16 16
13 13 14
11 12 12
10 10 11
9 9 9
8 8 8
6 6 7
5 5 5
3 3 3
2 2 2
2 2 2


31 32 33 34 35

27 28 29 30 31
24 24 25 26 27
19 20 20 21 22
15 15 16 16 17
12 13 13 14 14
10 11 11 11 12
9 9 10 10 10
8 8 9 9 9
7 7 8 8 8
6 6 7 7 7
5 5 5 5 6
4 4 4 4 4
2 3 3 3 3
2 2 2 2 2
2 2 2 2 2



42 43 44 45 46

37 38 39 40 40
32 33 33 34 35
26 27 27 28 29
20 21 21 22 22
17 17 18 18 18
14 14 15 15 15
12 12 13 13 13
11 11 11 12 12
10 10 10 10 11
8 9 9 9 9
7 7 7 7 7
5 5 5 5 6
3 3 4 4 4
3 3 3 3 3
2 2 2 2 2


* Afternoon maximum temperature minus forecast minimum temperature
(Lakeland forecast).




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