// beteljuice.com - near enough Zambretti Algorhithm // June 2008 - v1.0 // tweak added so decision # can be output /* Negretti and Zambras 'slide rule' is supposed to be better than 90% accurate for a local forecast upto 12 hrs, it is most accurate in the temperate zones and about 09:00 hrs local solar time. I hope I have been able to 'tweak it' a little better ;-) This code is free to use and redistribute as long as NO CHARGE is EVER made for its use or output */ // ---- 'environment' variables ------------ var z_where = 1; // Northern = 1 or Southern = 2 hemisphere var z_baro_top = 1050; // upper limits of your local 'weather window' (1050.0 hPa for UK) var z_baro_bottom = 950; // lower limits of your local 'weather window' (950.0 hPa for UK) // usage: forecast = betel_cast( z_hpa, z_month, z_wind, z_trend [, z_where] [, z_baro_top] [, z_baro_bottom])[0]; // z_hpa is Sea Level Adjusted (Relative) barometer in hPa or mB // z_month is current month as a number between 1 to 12 // z_wind is English windrose cardinal eg. N, NNW, NW etc. // NB. if calm a 'nonsense' value should be sent as z_wind (direction) eg. 1 or calm ! // z_trend is barometer trend: 0 = no change, 1= rise, 2 = fall // z_where - OPTIONAL for posting with form // z_baro_top - OPTIONAL for posting with form // z_baro_bottom - OPTIONAL for posting with form // [0] a short forecast text is returned // [1] zambretti severity number (0 - 25) is returned ie. betel_cast() returns a two deep array var z_forecast = new Array("Settled fine", "Fine weather", "Becoming fine", "Fine, becoming less settled", "Fine, possible showers", "Fairly fine, improving", "Fairly fine, possible showers early", "Fairly fine, showery later", "Showery early, improving", "Changeable, mending", "Fairly fine, showers likely", "Rather unsettled clearing later", "Unsettled, probably improving", "Showery, bright intervals", "Showery, becoming less settled", "Changeable, some rain", "Unsettled, short fine intervals", "Unsettled, rain later", "Unsettled, some rain", "Mostly very unsettled", "Occasional rain, worsening", "Rain at times, very unsettled", "Rain at frequent intervals", "Rain, very unsettled", "Stormy, may improve", "Stormy, much rain"); // equivalents of Zambretti 'dial window' letters A - Z var rise_options = new Array(25,25,25,24,24,19,16,12,11,9,8,6,5,2,1,1,0,0,0,0,0,0) ; var steady_options = new Array(25,25,25,25,25,25,23,23,22,18,15,13,10,4,1,1,0,0,0,0,0,0) ; var fall_options = new Array(25,25,25,25,25,25,25,25,23,23,21,20,17,14,7,3,1,1,1,0,0,0) ; var z_test = new Array(); // ---- MAIN FUNCTION -------------------------------------------------- function betel_cast( z_hpa, z_month, z_wind, z_trend, z_hemisphere, z_upper, z_lower) { if(z_hemisphere) z_where = z_hemisphere; // used by input form if(z_upper) z_baro_top = z_upper; // used by input form if(z_lower) z_baro_bottom = z_lower; // used by input form z_range = z_baro_top - z_baro_bottom; z_constant = (z_range / 22).toFixed(3); z_season = (z_month >= 4 && z_month <= 9) ; // true if 'Summer' if (z_where == 1) { // North hemisphere if (z_wind == "N") { z_hpa += 6 / 100 * z_range ; } else if (z_wind == "NNE") { z_hpa += 5 / 100 * z_range ; } else if (z_wind == "NE") { // z_hpa += 4 ; z_hpa += 5 / 100 * z_range ; } else if (z_wind == "ENE") { z_hpa += 2 / 100 * z_range ; } else if (z_wind == "E") { z_hpa -= 0.5 / 100 * z_range ; } else if (z_wind == "ESE") { // z_hpa -= 3 ; z_hpa -= 2 / 100 * z_range ; } else if (z_wind == "SE") { z_hpa -= 5 / 100 * z_range ; } else if (z_wind == "SSE") { z_hpa -= 8.5 / 100 * z_range ; } else if (z_wind == "S") { // z_hpa -= 11 ; z_hpa -= 12 / 100 * z_range ; } else if (z_wind == "SSW") { z_hpa -= 10 / 100 * z_range ; // } else if (z_wind == "SW") { z_hpa -= 6 / 100 * z_range ; } else if (z_wind == "WSW") { z_hpa -= 4.5 / 100 * z_range ; // } else if (z_wind == "W") { z_hpa -= 3 / 100 * z_range ; } else if (z_wind == "WNW") { z_hpa -= 0.5 / 100 * z_range ; }else if (z_wind == "NW") { z_hpa += 1.5 / 100 * z_range ; } else if (z_wind == "NNW") { z_hpa += 3 / 100 * z_range ; } if (z_season == 1) { // if Summer if (z_trend == 1) { // rising z_hpa += 7 / 100 * z_range; } else if (z_trend == 2) { // falling z_hpa -= 7 / 100 * z_range; } } } else { // must be South hemisphere if (z_wind == "S") { z_hpa += 6 / 100 * z_range ; } else if (z_wind == "SSW") { z_hpa += 5 / 100 * z_range ; } else if (z_wind == "SW") { // z_hpa += 4 ; z_hpa += 5 / 100 * z_range ; } else if (z_wind == "WSW") { z_hpa += 2 / 100 * z_range ; } else if (z_wind == "W") { z_hpa -= 0.5 / 100 * z_range ; } else if (z_wind == "WNW") { // z_hpa -= 3 ; z_hpa -= 2 / 100 * z_range ; } else if (z_wind == "NW") { z_hpa -= 5 / 100 * z_range ; } else if (z_wind == "NNW") { z_hpa -= 8.5 / 100 * z_range ; } else if (z_wind == "N") { // z_hpa -= 11 ; z_hpa -= 12 / 100 * z_range ; } else if (z_wind == "NNE") { z_hpa -= 10 / 100 * z_range ; // } else if (z_wind == "NE") { z_hpa -= 6 / 100 * z_range ; } else if (z_wind == "ENE") { z_hpa -= 4.5 / 100 * z_range ; // } else if (z_wind == "E") { z_hpa -= 3 / 100 * z_range ; } else if (z_wind == "ESE") { z_hpa -= 0.5 / 100 * z_range ; }else if (z_wind == "SE") { z_hpa += 1.5 / 100 * z_range ; } else if (z_wind == "SSE") { z_hpa += 3 / 100 * z_range ; } if (z_season == 0) { // if Winter if (z_trend == 1) { // rising z_hpa += 7 / 100 * z_range; } else if (z_trend == 2) { // falling z_hpa -= 7 / 100 * z_range; } } } // END North / South if(z_hpa == z_baro_top) z_hpa = z_baro_top - 1; z_option = Math.floor((z_hpa - z_baro_bottom) / z_constant); z_output = ""; if(z_option < 0) { z_option = 0; z_output = "Exceptional Weather, "; } if(z_option > 21) { z_option = 21; z_output = "Exceptional Weather, "; } if (z_trend == 1) { // rising z_output += z_forecast[rise_options[z_option]] ; z_test[1] = rise_options[z_option]; } else if (z_trend == 2) { // falling z_output += z_forecast[fall_options[z_option]] ; z_test[1] = fall_options[z_option]; } else { // must be 'steady' z_output += z_forecast[steady_options[z_option]] ; z_test[1] = steady_options[z_option]; } // return z_output ; z_test[0] = z_output ; return z_test ; } // END function