How to Use cmsWxCalcIII
Latest revision: January 10, 2018
Browser Requirements
This program has been tested mainly on W3C-compliant browsers (Safari, primarily). The program is written in JavaScript 1.2+, so you need to have JavaScript enabled and a recent enough browser to support version 1.2 or later of JavaScript (any modern browser should work).
What's New with Versions 1.0 through 3.1
Version 3.6.2 (2018-05-02) fixed some issues with the heat index calculation.
Version 3.1.1/CmsWxCalc v 3.6.1 (1/10/18) modified the input boxes to expect numeric input and changed one label to prefer the higher-level version number (3.6.1).
Version 3.1/CmsWxCalc v. 3.6 (3/31/11) slants the application defaults more toward the Système International and improves labeling with more-correct names/abbreviations. Most (all?) options were alphabetized. Added recent modifications to the heat index calculation.
Version 3.0/CmsWxCalc v. 3.5 (?/?/09) made cmsWxCalc a universal script (usable on both cmsharpe.com and office Intranet).
Version 2.0 (8/17/01) adds the National Weather Service's "new" wind chill equation (see the JavaScript code for the equation) and displays both the old and the new Wind Chill Equivalent Temperatures - if the given temperature is 10°C/50°F/283 K or colder.
Version 1.3.1 (2/24/01) involves some cosmetic changes, including a new color scheme, more along the lines of the original plan (blue/pink tones replacing the red/yellow version).
Version 1.3 (2/2/01) fixes a subtle bug (in the HTML!) that prevented the program from working with Netscape Navigator. Added a tab index and alt-key support (works only with Explorer at this point), so you can tab in a more convenient order - and use Alt-C for "Calculate!" and Alt-R for "Reset." On non-Windows computers, the key commands may be different. Also added an error message that is displayed when JavaScript is absent or not enabled.
Version 1.2.1 (1/25/01) corrects a minor error in the form format. I intended the text boxes (where you enter the values) to be 7 characters wide. This version reduces the size to the 7 characters I originally wanted. Another change was on the Dew Point/Wet Bulb/Relative Humidity line in the input table. The table cells were filled in as blank cells, connecting the yellow (now pink) pattern on the right.
Version 1.2 (1/4/01) includes mostly minor enhancements. The form page now has a marble background (like my main page), and the output window's table now has values centered within the table cells.
Version 1.0 was published on December 25, 2000. Just two days later came version 1.1. That version introduced the "Reset" button and fixed a problem with the output window's failure to clear before updating. It also included a few minor bug fixes.
Units Selection
You can select various groups of input units by using the "drop-down" box at the bottom of the table. When you release the mouse button, the changes will be made (unless you didn't change the selection). You may also change each individual item by accessing its drop-down box (input units) or check boxes (output units). The "Reset" button resets the units according to the current selection in the drop-down selector box.
Selecting Input Data Types
For humidity entities, you can select relative humidity, dew point, or wet-bulb temperature. cmsWxCalcIII will compute the other two.
For pressure entities, you can select either station pressure or altimeter setting. cmsWxCalcIII will compute the other, based on the elevation provided. Note that "altimeter setting" is the same thing as "pressure reduced to sea level." This value, however, is not temperature-corrected, so it will not necessarily match the "sea level pressure" value in official weather observations.
Entering Data
Simply type the appropriate values in the text boxes provided. Changing the units values will not change the numbers in the text boxes. If you enter a bad or otherwise inappropriate value, you will probably see an alert window pop up after you click on "Calculate!". If you are using a mobile device, a numeric keyboard (or at least a keyboard with numbers on it) should appear for these entries, while on a full-size browser, there should be a spin box on the side to allow +1/-1 changes with a mouse click (hold button to spin through many numbers).
If you leave a text box blank, cmsWxCalcIII uses an appropriate value as follows:
- Temperature = freezing point of water
- Relative Humidity = 100%
- Wind Speed = 0
- Altimeter Setting = standard pressure
- Elevation = 0
Note that these defaults are used without regard to which humidity entity or pressure type you have selected.
You may also use the [Tab] (and [Shift-Tab]) key to navigate through the text-entry boxes and drop-down lists.
Calculate! Button
The "Calculate!" button causes the program to compute all the various weather elements that it can. As it does so, it creates a new window for display. The output is arranged in a table format.
For example:
|
Results:
|
|
| Temperature | 32°F |
|---|---|
| Wet Bulb | 32°F |
| Dew Point | 32°F |
| Relative Humidity | 100% |
| Old Wind Chill | 32°F |
| New Wind Chill | 32°F |
| Wind | 0 mph |
| Station Pressure | 29.92 in |
| Altimeter | 29.92 in |
| Elevation | 0 ft |
cmsWxCalcIII computes, as appropriate, the following values:
- Dew Point
- Relative Humidity
- Wet Bulb Temperature
- Old Wind Chill Equivalent Temperature (if the temperature is 10°C or colder)
- New Wind Chill Equivalent Temperature (if the temperature is 10°C or colder)
- Heat Index (if the temperature is at least 25°C)
- Station Pressure
- Altimeter Setting
If you prefer to use the keyboard, [Alt-C] (or your operating system's equivalent to this Windows key combination) does the same thing as clicking the button. Note that this does not yet appear to work with Netscape Navigator 4.x.
Reset Button
New with version 1.1, the Reset button may be used to set all the "values" to blanks, set the input units drop-down boxes to those associated with the currently-selected "input units," set the output units (the checkboxes) to those associated with the currently-selected "output units," and set all the "extra decimals" drop-down boxes to zero.
Like the Calculate! button above, you may use [Alt-R] for the same effect as clicking the Reset button. Again, this feature doesn't seem to work with Navigator 4.x.
Uses for This Program
- Fire Weather - Enter the projected temperature and dew point. cmsWxCalcIII will compute the relative humidity for you.
- Indoor Humidity - You can get an idea of indoor humidity by entering the indoor temperature and outdoor dew point. The calculated relative humidity represents the indoor relative humidity, assuming no additional moisture is added.
- Units Conversion - Although there are several other programs and Web sites where unit conversion is provided (including another "WxCalc!"), few - if any - others provide as many conversions as cmsWxCalcIII.
- Wind Chill & Heat Index - Enter temperature and wind - or temperature and humidity - and find out approximately how it feels outside (or inside!).
- Psychrometry - If you have a psychrometer, just enter the dry-bulb and wet-bulb temperatures and your approximate elevation (or approximate station pressure) and let this program figure out the rest.
- Wet-bulb zero - The height of "wet-bulb zero" is significant for predicting hail, among other things. To obtain the wet-bulb temperature at 850 mb, for example, enter the temperature and dew point at 850 mb, enter 850 mb as the station pressure, and calculate the rest.
- Whatever - I'm sure there must be more uses.... :-)
Happy weather calculating -
Cheryl Sharpe
