Pasha, here are the information about the pressure trend as used in one of the JavaScript (for the Weather Display software):
- the original (Ken True) trend words: Steady, Rising Slowly, Rising Rapidly, Falling Slowly, Falling Rapidly
- the original (Ken True) JavaScript code associated with those words:
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if ((btrnd >= -0.7) && (btrnd <= 0.7)) { return(langBaroTrend[0]); } // Steady
if ((btrnd > 0.7) && (btrnd < 2.0)) { return(langBaroTrend[1]); } // Rising Slowly
if (btrnd >= 2.0) { return(langBaroTrend[2]); } // Rising Rapidly
if ((btrnd < -0.7) && (btrnd > -2.0)) { return(langBaroTrend[3]); } // Falling Slowly
if (btrnd <= -2.0) { return(langBaroTrend[4]); } // Falling Rapidly
return(btrnd);
The above code was designed using the following rate of change information:
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Change Rates
Rapidly =.06 inHg; 1.5 mm Hg; 2 hPa; 2 mb
Slowly =.02 inHg; 0.5 mm Hg; 0.7 hPa; 0.7 mb
But I was not satisfied with the trend results so I made some changes to the pressure trend (added 2 trend levels):
- Ray's new trend words: Steady, Gently Rising, Rising Slowly, Rising Rapidly, Gently Falling, Falling Slowly, Falling Rapidly
- Ray's JavaScript code associated with those words:
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switch (true) {
case ((btrnd == 0.0) || (btrnd == -0.0)) : barotrend = langBaroTrend[0]; break; // Steady
case ((btrnd > 0.0) && (btrnd < 0.7)) : barotrend = langBaroTrend[1]; break; // Gently Rising
case ((btrnd >= 0.7) && (btrnd < 2.0)) : barotrend = langBaroTrend[2]; break; // Rising Slowly
case ((btrnd >= 2.0)) : barotrend = langBaroTrend[3]; break; // Rising Rapidly
case ((btrnd < -0.0) && (btrnd > -0.7)) : barotrend = langBaroTrend[4]; break; // Gently Falling
case ((btrnd <= -0.7) && (btrnd > -2.0)) : barotrend = langBaroTrend[5]; break; // Falling Slowly
case ((btrnd <= -2.0)) : barotrend = langBaroTrend[6]; break; // Falling Rapidly
default : barotrend = langBaroTrend[0]; break; // Steady
}
return(barotrend);
My code was redesigned using the following rate of change information:
Code: Select all
Change Rates
Rapidly = 2 hPa; 2 mb; 0.06 inHg; 1.5 mm Hg;
Slowly = 0.7 hPa; 0.7 mb; 0.02 inHg; 0.5 mm Hg
Gently = < 0.7 hPa; < 0.7 mb; < 0.02 inHg; < 0.5 mm Hg
The pressure trend numeric value, which can be positive, zero, or negative is produced by Weather Display and is based on a 3-hour pressure change - the trend value is in hPa or millibars.
The JavaScript also produces 2 icons:
- a green up arrow
- a red down arrow
Obviously, I had to modify that limited display, so I added an additional icon:
- a green up arrow - pressure going up
- a red and green horizontal bar - pressure steady (not changing)
- a red down arrow - pressure going down
Now to answer your questions...
Question 1: If you have only the pressure trend for the past hour, you should include that value until it can be replaced with the pressure trend for the past 3 hours.
Question 2: I am not too sure I understand what you meant when you wrote "Does it make sense to display pressure trend for the weather forecast?". The pressure trend is a very big part of the immediate forecast and can tell what is happening even if a new and complete forecast from some other source is only provided every 6 to 12 hours. For example, if there is a big drop of pressure, then I can expect some really bad weather and I do not have to be told every 6 to 12 hours that bad weather is coming, I can see it by just looking at the pressure change.
Question 3: Pasha, remember the expression "KISS" (almost meaning keep it simply simple ...
). Only 3 icons should be used for the 3 states: raising, falling, and steady. I think and feel that the arctangent approach might and will make thing too complicated for the average user. Again, "KISS"...
Please, help me to find the value when steady trend turnes into raising one.
Do you think any of the information provided above could be useful?
