Willim's Page 253

253 Weather in the Philippine Islands ,P.I., π

This website provides very good details of the weather in the PI.

https://weatherspark.com/averages/33316/Lapu-Lapu-City-Bicol-Philippines

For Cebu it can be seen that the minimums are 24^C - 26^C and the highs 30^C -33^C. The web site also shows the humidity which is one on the main reasons air conditioning is likely to be required.

Further investigation in January, 2017 produced this spreadsheet showing the maximum, tab 01_Max and minimum, tab 02_Min and  temperatures on each day of the year.

Tab 03 plots maximum and minimum Temperature versus Dew Point Temperature with the Relative Humidity shown in each appropriate cell. 

Cells with 70%+ RH are filled to show mould/ mold/ mildew risk, cell with 60%+ are filled to show asthmatic risks.

Link to Temp_Min_Max_Cebu_01.ods [118kb] approx. ODS Calc icon

The data source was Weather Underground - https://www.wunderground.com/history/airport/RPVM/2016/6/1/DailyHistory.html?req_city=Mactan-Cebu+International&req_state=&req_statename=Philippines&reqdb.zip=00000&reqdb.magic=207&reqdb.wmo=WRPVM

In May or June, especially, highs of 35,36 or 38 can occur and sometimes in other months. No month seems to be totally immune to an occasional high.

Similarly most lows occur in January, February and March with occasional lows in other months.

Two record equaling dew point temperatures have occurred according to the records but I believe them to be "typographical errors"

 Link to High_Td_01.pdf [78kb] approx. Spreadsheet Acrobat PDF icon

The METAR data extracted from the site is shown on each row. 24/22 the only data with "/" on each row shown the temperature / dew point temperature.

These two values are used to determine the relative humidity for 24/22 the relative humidity is 88% and 24/23 is 94%. At high relative humidity the value calculated is only to the nearest 6%.   At lower relative humidity 34/26 62% and 34/27 66% The values differ by 4%.

There is little value in doing any cooling calculations better than the closest 1% or so using temperature, dew point temperature or relative humidity as initial data.

On other websites I noticed that mould/ mold/ mildew is an issue in the Philippines and set out to combat the issue.

From the minimum temperatures only about six days have had a dew point temperature less than 20^C. From this I believe that if we air condition such that the dew point temperature is 18 or less say we should have few(er) mildew issues (in future). 30/19 RH 51,  27/16 RH 50 and 24/13 RH 50.

From browsing on the web 50% RH seems to be the closest thing to an "ideal" RH although the range varies from 30 - 60% RH.

Inside buildings above 27^C there maybe issues with static electricity - see 604 Air Con.

When the humidity is high, high air speeds are required for there to be “wind chill.”  To demonstrate this I developed this table from the Australian Apparent Temperature formula given at https://en.wikipedia.org/wiki/Wind_chill as it included terms for the Humidity unlike the Canada, UK and US “Wind Chill” formulae.

The Dew Point Temperatures, Td, Absolute Humidity, AH g/m3, and Percentage Moisure Vapour, %Mv, in the upper table are "average" values for the temperature range shown in the lower table. There will be little cooling effect at air velocities less than that shown in the column headers. A worked example showing the Australian Apparent Temperaures, AAT, for T=33, RH%=32.8 at the velocities in the column header is provided.

Fans might not be effective in providing a "wind chill" effect. However fans are better than nothing as can be seen in the worked example but AAT for 0m/s is 34.7^C and the AAT at 1m/s is 33.7^C so the fan is providing a 1^C  reduction in the AAT.

Air Velocity m/s 0
1
2
5
10
15
20
25
30
Td ^C 9.9
12.4
14.5
19.5
25.9
30.6
34.5
37.7
40.5
AH g/m3 8.3
9.8
11.3
15.5
22.9
30.1
37.4
44.6
52.4
%Mv 1.2
1.4
1.6
2.2
3.3
4.3
5.4
6.5
7.5
e.g. T=33
RH%
=32.8






AAT ^C
34.4
33.7
33.0
30.9
27.4
23.9
20.4
16.9
13.4

Max Dew Point Temperatures and Absolute Humidities for Cooling Effect.

If the Relative Humidity, RH% is greater than that shown in the table below there will be little cooling effect at air velociities less than that shown in the column headers.

Air Velocity m/s

0

1

2

5

10

15

30

T ^C



Relative

Humidity

RH%



18

60

69

80





21

49

57

66

92




24

41

48

55

76




27

34

40

46

64

94



30

29

34

39

54

79



33

24

29

33

45

66

88


36

20

24

28

38

56

74


39

17

20

23

33

48

63


42

15

18

20

28

41

54

93

45

13

15

17

24

35

46

79

Max RH for Cooling Effect at Temperatures and Air Velocities Shown.

18^C - This is about the temperature in a UK workshop
45^C - Kuwait reaches over 46^C. The table should cover most hot cities in the world as Kuwait is one of the hottest cities, if not the hottest on Earth.

At 1m/s a sheet of paper is blown around. The 15m/s velocity is approximately 50km/hr / 30mi/hr and is for those on motorcycles or open vehicles.

For other temperatures and velocities see … http://planetcalc.com/2089/

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