How Weather Radar Covers Kirksville

Kirksville does not have its own WSR-88D NEXRAD weather-radar site.

The area is viewed from regional radars, and that distance matters because a radar beam gets higher and wider as it travels away from the antenna.

That is one reason radar cannot tell you everything happening at ground level in Northeast Missouri.

The nearest major radar is still far away

Using current NOAA site coordinates and Kirksville's location, the Kansas City/Pleasant Hill radar KEAX is roughly 130 miles from Kirksville.

The Quad Cities radar KDVN is roughly 140 miles away.

Other regional radars can also contribute views of Northeast Missouri, but Kirksville sits well away from a WSR-88D tower.

This is not the same thing as saying Kirksville has "no radar coverage."

It means the regional radars are looking at the atmosphere over Kirksville from a long distance.

The beam rises with distance

The lowest standard WSR-88D scan begins at about 0.5 degrees above horizontal.

That sounds nearly flat, but Earth curves away underneath the beam, and normal atmospheric refraction only partially bends the radio energy back toward the surface.

Using standard-atmosphere beam geometry, the center of the 0.5-degree beam is roughly:

• 14,000–15,000 feet above radar level by the time KEAX reaches Kirksville;
• roughly 16,000–17,000 feet above radar level from KDVN.

These are approximate geometric values, not fixed real-world heights. Atmospheric refraction changes from day to day, and terrain/elevation affect height above local ground.

The important point is the scale: distant radar is sampling thousands of feet above Kirksville even on its lowest scan.

Why low-level weather can be harder to see

A storm may have important features near the surface that are below the center of a distant radar beam.

This is called beam overshoot when the beam passes above low-level precipitation or storm structure.

NWS training material specifically warns that distant radar can underestimate or fail to sample weather near the surface because the beam becomes elevated with range.

That can matter with:

• shallow winter precipitation;
• low cloud layers;
• low-level rotation;
• localized wind damage;
• rainfall near the ground.

Radar is still extremely useful. It is simply not a camera looking horizontally across town.

The beam also gets wider

NEXRAD's beam is about one degree wide.

As distance increases, that angle covers a larger physical area.

NWS material notes that the beam width reaches roughly two kilometers by about 111 kilometers from the radar and continues widening beyond that.

At Kirksville's distance from regional sites, each radar sample represents a much larger atmospheric volume than it would close to the radar.

That reduces fine detail.

Comparing more than one radar can help

A storm far from KEAX may be viewed from a somewhat different angle by KDVN or another regional radar.

One site may sample a feature at a different height or have fewer obstructions in that direction.

Weather professionals use mosaics and multiple-radar products partly for this reason.

For a resident, the practical lesson is not to obsessively switch sites during every storm. It is to understand that the smooth national radar mosaic is built from multiple radars with different viewing geometry.

Radar is not ground truth

Radar can estimate precipitation and motion aloft.

It cannot directly tell you everything that is happening at a house, road or field.

That is why the weather-observation system also includes:

• surface stations;
• rain gauges;
• trained spotters;
• satellite data;
• lightning networks;
• forecasts and warnings.

For the broader measurement system, see Weather Monitoring Around Kirksville.

For warnings rather than radar interpretation, see Severe Weather Alerts in Kirksville.

Use radar for what it does well

Radar is excellent for seeing precipitation structure, storm motion and broad storm evolution.

Use it as one layer.

Do not interpret a weak-looking low-level radar return 130 miles from the radar as proof that nothing significant is happening at the surface.

When conditions are dangerous, official warnings and local observations matter more than trying to reverse-engineer one radar pixel.