Live/Radar/Every radar/PACG
Single radar / Alaska
Sitka radar PACG
The weather service radar at Sitka, Alaska, alone: each picture it makes from its own scans, at four tilts from its lowest up, every few minutes. Reflectivity, velocity, storm relative velocity, correlation coefficient and differential reflectivity, the storms it tracks and where they are headed, and how high its beam passes. How to read them.
- Latest scan
- Scanning
- Clear air mode, pattern 35
- Tilts
- 0.5°, 1.3°, 2.4°, 3.1°
- Stands at
- 56.853°N 135.529°W, 207 ft above sea level
- Reaches
- 286 mi with reflectivity, 186 mi with velocity, 143 mi with storm relative velocity
Storms it tracks
The radar follows each storm cell from scan to scan, measures the way it is moving, and puts it ahead 15 to 60 minutes. Each is drawn on the map above, its track to the hour ahead marked each quarter hour.
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How high it sees
The beam leaves the radar tilted up and the earth curves away under it, so the farther from the radar, the higher it passes. Rain or snow falling under the lowest beam is not seen: far from the radar, shallow snow and drizzle can fall unseen. The heights are the standard ones, the air bending the beam as the weather service’s own rule takes it.
| Tilt | 25 mi | 50 mi | 100 mi | 150 mi | 200 mi |
|---|---|---|---|---|---|
| 0.5° | 1,500 ft | 3,600 ft | 9,600 ft | 18,200 ft | 29,200 ft |
| 1.3° | 3,300 ft | 7,200 ft | 17,000 ft | 29,300 ft | 44,000 ft |
| 2.4° | 5,800 ft | 12,300 ft | 27,200 ft | 44,500 ft | 64,400 ft |
| 3.1° | 7,500 ft | 15,600 ft | 33,600 ft | 54,200 ft | 77,400 ft |
| Width | 2,200 ft | 4,400 ft | 8,800 ft | 13,100 ft | 17,500 ft |
How to read the pictures
- Reflectivity
- How strongly rain, snow and hail send the pulse back, in dBZ: the stronger, the heavier.
- Velocity
- The wind along the beam, in mph: green toward the radar, red away. Where the two meet tightly, the wind turns.
- Storm relative velocity
- The same wind with the storms’ own motion taken away, so a storm’s turning stands out: a tight pair of green and red is a rotating storm.
- Correlation coefficient
- How alike the returns of one pulse are, 0 to 1: rain and snow near 1, hail and melting snow lower, and debris a tornado lifts well below 0.8.
- Differential reflectivity
- How much wider than tall what falls is, in dB: large flat raindrops read high, hail and dry snow near 0.
Each picture is one tilt of one scan, as the radar sent it: its lowest tilt first, then three above it, the angles its scan pattern sets. A picture at a higher tilt sees higher into a storm, and farther over the ground at each distance. Press a point on the map to read the value there.
As data: /radar/now.json?show=sref&site=PACG, the times of its frames, and /radar/s/PACG/storms.json, the storms it tracks.