Cumulus Support

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// ------- Variable Wind check -------------------------
/* from METAR coding
* if direction varies by 60 deg or more and speed greater than 6 knots,
* a Variable wind direction group is reported (eg. 180V240), otherwise omitted.
* If wind direction is variable and speed 6 knots or less, 
* replace wind direction with VRB followed by wind speed in knots.
*
* This emulates that to provide 'degFrom', 'degTo', and 'vectorSize' variables
*
* METAR wind degrees are rounded to nearest 10 - we work 'normal'
* I am assuming the last 10 min. although some dialogues suggest 2 min.
* 
* Also I can find no info on the ORDER of the 180V240 deg. ie. 60 deg clockwise or 300 deg anti-clockwise ?
* So I am assuming (and coded) to read 'clockwise' (ie. 1st figure could be larger than 2nd.)
* eg 330V030 would be 60 deg 'around' North, 150V240 would be 90 deg 'around' South.
* 
*/

/* Philosophy
*  Get last 10 mins worth of CURRENT wind direction degrees
*  Compare each with CURRENT AVG wind direction degrees to get a + / - 'offset'
*  add (absolutely) the max 'offsets' to get wind 'vector' size
*/
 
/* Prerequisites: - names are for easy reference / substitution
* 
* windDeg10 - an array containing the last 10 minutes of current / now wind DIRECTIONS in degrees
* windVarAvg - the CURRENT 10 minute average wind DIRECTION in degrees
*
* wind_kts_ave - could be any CURRENT AVERAGE SPEED unit, used (or maybe not) to give alternate output
*/

 
				windVar_temp_degDiff = new Array(); // new array to store deviation from CURRENT average
				windVarCount = windDeg10.length; 


				// step through 10min values, calculate the differences to CURRENT avg and populate a new array
				y = 0; // initialise windVar_temp_degDiff[] pointer
				for(x = 0; x < windVarCount; x++) { // go through 10min values
					// work out difference between 'then' current and 'now' 10 min average
// Cumulus, in common with some other softwares, returns 0 degrees if zero wind speed 
// if this is true for the 10min array then at this point you need to do a check and 'jump' to next 'x' to be safe
// if required - if(windDeg10[x] == 0) 'jump' check here
					degDiff_temp = windDeg10[x] - windVarAvg;

					if(degDiff_temp >= 180) {
						degDiff_temp = degDiff_temp -360;
					} else {
						if(degDiff_temp <= -180){
							degDiff_temp = degDiff_temp +360;
						}
					}

					windVar_temp_degDiff[y] = degDiff_temp;
					y++; // increment new array pointer
// if required - END 'jump' check

				} // END 10min step through, new Array windVar_temp_degDiff has been populated with difference to average
				
				// find (plus / minus) deviation extremes - arrayMax() and arrayMin() are 'invented' functions
				degHi = arrayMax(windVar_degDiff); // positive values, might NOT be initially, if the (wx) avg period has not been completed ;-)
				degLo = arrayMin(windVar_degDiff); // negative values, might NOT be initially, if the (wx) avg period has not been completed ;-)

				// Belts 'n' Braces - Lo must be lower or equal to avg, Hi must be higher or equal to avg
				if(degLo > 0) {degLo = 0;}
				if(degHi < 0) {degHi = 0;}

// so now we have the max +/- deviation with respect to CURRENT average direction 

				// Now workout max 'vector' size !!
				vectorSize = degHi + Math.abs(degLo);

// FINALLY - workout logical from > to values eg. 350 15 would be straddling North
// average SPEED check is optional, you may also decide eg. a vectorSize < 10 is irrelevant ? - upto you
				if(wind_kts_ave > 0) { // need to build output as [from to]
					degFrom = windVarAvg + degLo; 
					if(degFrom < 0){degFrom = 360 + degFrom;} 
					degTo = windVarAvg + degHi; // 
					if(degTo > 360){degTo=degTo-360;}
				}else{ // NORMAL - I choose to o/p ave, but it could be null or current
					// *** PUT ALTERNATIVE VALUES HERE !!! *************
				}// END if average SPEED 

// END Variable Wind

// So now you have degFrom, degTo, and vectorSize all in integer degrees available for 'output'