Single radar / California

San Diego radar KNKX

The weather service radar at San Diego, California, 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: 6:26 AM UTC
Scanning: Precipitation mode, pattern 215
Tilts: 0.5°, 1.3°, 2.4°, 3.1°
Stands at: 32.919°N 117.042°W, 955 ft above sea level
Reaches: 286 mi with reflectivity, 186 mi with velocity, 143 mi with storm relative velocity

KNKX on the map

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.

Storm cells KNKX tracks, from its scan of 6:20 AM UTC
Storm	Where	Moving	In 30 minutes	In 60 minutes	Last forecast off by
U6	59 mi east southeast of the radar59 mi from the radar, bearing 118°	Toward the north at 36 mph	54 mi east of the radar	-	1.7 mi
K5	2 mi west of Ramona, CA12 mi from the radar, bearing 46°	Toward the north northwest at 31 mph	4 mi east northeast of Valley Center, CA	5 mi east of Temecula, CA	0.3 mi
G7	3 mi north northwest of Escondido, CA17 mi from the radar, bearing 352°	Toward the northwest at 26 mph	-	-	4.9 mi
N0	55 mi southeast of the radar55 mi from the radar, bearing 145°	Toward the northwest at 56 mph	-	-	2.9 mi
D0	62 mi southeast of the radar62 mi from the radar, bearing 125°	First seen this scan	-	-	0 mi
Y7	11 mi west southwest of Del Mar, CA23 mi from the radar, bearing 267°	Toward the south at 20 mph	-	-	4 mi
H0	1 mi north northeast of Pala, CA32 mi from the radar, bearing 358°	First seen this scan	-	-	0 mi
A7	5 mi east of San Diego Country Estates, CA20 mi from the radar, bearing 72°	First seen this scan	-	-	0 mi
O9	2 mi north of Eucalyptus Hills, CA6 mi from the radar, bearing 94°	Toward the north at 28 mph	7 mi east southeast of Escondido, CA	4 mi north northeast of Valley Center, CA	0.9 mi
X0	7 mi north northwest of San Diego, CA13 mi from the radar, bearing 231°	First seen this scan	-	-	0 mi
U8	12 mi southeast of Chula Vista, CA30 mi from the radar, bearing 159°	Toward the north northeast at 16 mph	8 mi south southeast of Jamul, CA	-	2.2 mi
V9	68 mi east southeast of the radar68 mi from the radar, bearing 107°	Toward the north northwest at 63 mph	59 mi east of the radar	3 mi west of Oasis, CA	0.7 mi
D7	3 mi north northeast of Green Acres, CA59 mi from the radar, bearing 359°	Toward the west northwest at 39 mph	-	-	2.5 mi
L7	7 mi north of Pine Valley, CA31 mi from the radar, bearing 88°	First seen this scan	-	-	0 mi
W6	9 mi south southeast of Alpine, CA24 mi from the radar, bearing 126°	First seen this scan	-	-	0 mi
W9	14 mi south of Borrego Springs, CA41 mi from the radar, bearing 77°	Toward the north northwest at 59 mph	11 mi south southeast of Anza, CA	-	1.5 mi
P8	44 mi west northwest of the radar44 mi from the radar, bearing 299°	Toward the south southwest at 33 mph	-	-	5.6 mi
D9	58 mi south southeast of the radar58 mi from the radar, bearing 152°	First seen this scan	-	-	0 mi
C1	7 mi southwest of San Clemente, CA50 mi from the radar, bearing 309°	First seen this scan	-	-	0 mi
E0	10 mi south of Borrego Springs, CA40 mi from the radar, bearing 71°	First seen this scan	-	-	0 mi
E9	3 mi north of Valley Center, CA25 mi from the radar, bearing 3°	Toward the west at 33 mph	2 mi north of Oceanside, CA	-	2.1 mi
I0	32 mi northeast of the radar32 mi from the radar, bearing 38°	First seen this scan	-	-	0 mi
Y6	41 mi south southwest of the radar41 mi from the radar, bearing 192°	First seen this scan	-	-	0 mi
H6	40 mi south southwest of the radar40 mi from the radar, bearing 212°	Toward the north northeast at 23 mph	13 mi southwest of Coronado, CA	-	2.2 mi
S0	2 mi north northeast of Poway, CA6 mi from the radar, bearing 8°	First seen this scan	-	-	0 mi

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.

The middle of each tilt’s beam, in feet above the radar’s antenna, and how wide the beam has grown
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=KNKX, the times of its frames, and /radar/s/KNKX/storms.json, the storms it tracks.