Northwest Oregon Dry Easterlies
"NODE" Index

The NODE Index is designed to give people a “heads up,” when dry east winds are likely to occur in northwestern Oregon.
It is dimensionless with an arbitrary scale from 0 to 100 (higher indices indicate stronger east winds and/or lower humidities).

The NODE index is computed as follows:

```    function compute_node(\$wind_dir, \$wind_speed, \$rh){

\$wind_component = 0;

if(\$wind_dir>180){
\$wind_component = 0;
}elseif(\$wind_dir>0 and \$wind_dir<=90){
\$wind_component = .3333*\$wind_dir + min(2*\$wind_speed, 30);
}elseif(\$wind_dir>90 and \$wind_dir<180){
\$wind_component = .3333*(180-\$wind_dir) + min(2*\$wind_speed, 30);
}

if(trim(\$rh)==''){
\$rh_component=0;
}else{
\$rh_component=(100-\$rh)*.4;
}

if(1*\$wind_component==0){
\$node=0;
}else{
\$node= \$wind_component + \$rh_component;
}

if(\$wind_dir>0 and \$wind_dir<=90){
\$node = \$node*(\$wind_dir/90);
}elseif(\$wind_dir>90 and \$wind_dir<180){
\$node = \$node*((180-\$wind_dir)/90);
}

return round(\$node);
}

```

The NODE matrix uses forecasts from the National Weather Service’s National Digital Forecast Database (NDFD).
A server script downloads values of wind direction, speed, and relative humidity for each location in the matrix.
Hourly values are examined from 18Z (11am PDT) to 03Z (8pm PDT).
Daily NODE Indices are computed using the highest hourly values for wind component and the lowest hourly values for relative humidity.