Single radar / Florida

Jacksonville radar KJAX

The weather service radar at Jacksonville, Florida, 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: 6:31 AM UTC
Scanning: Precipitation mode, pattern 212
Tilts: 0.5°, 1.3°, 2.4°, 3.1°
Stands at: 30.485°N 81.702°W, 62 ft above sea level
Reaches: 286 mi with reflectivity, 186 mi with velocity, 143 mi with storm relative velocity

KJAX 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 KJAX tracks, from its scan of 6:23 AM UTC
Storm	Where	Moving	In 30 minutes	In 60 minutes	Last forecast off by
S9	At Tarpon Springs, FL174 mi from the radar, bearing 202°	Toward the north northeast at 37 mph	4 mi north northwest of Hudson, FL	-	1.8 mi
E9	157 mi east northeast of the radar157 mi from the radar, bearing 76°	Toward the north northeast at 38 mph	169 mi east northeast of the radar	183 mi east northeast of the radar	0.8 mi
U5	142 mi east southeast of the radar142 mi from the radar, bearing 120°	Toward the north northeast at 30 mph	137 mi east southeast of the radar	136 mi east southeast of the radar	0.2 mi
C9	140 mi east southeast of the radar140 mi from the radar, bearing 103°	Toward the north northeast at 33 mph	144 mi east of the radar	150 mi east of the radar	0.6 mi
F0	142 mi east southeast of the radar142 mi from the radar, bearing 115°	Toward the north northeast at 33 mph	142 mi east southeast of the radar	144 mi east of the radar	0.6 mi
W7	137 mi southwest of the radar137 mi from the radar, bearing 221°	Toward the northeast at 38 mph	119 mi southwest of the radar	7 mi southeast of Chiefland, FL	0.7 mi
N5	142 mi east southeast of the radar142 mi from the radar, bearing 112°	First seen this scan	-	-	0 mi
X2	168 mi east northeast of the radar168 mi from the radar, bearing 69°	Toward the north northeast at 26 mph	177 mi east northeast of the radar	-	1.2 mi
V1	1 mi west northwest of Chiefland, FL99 mi from the radar, bearing 226°	Toward the northeast at 25 mph	4 mi east southeast of Trenton, FL	6 mi south southwest of High Springs, FL	0.5 mi
J9	142 mi southeast of the radar142 mi from the radar, bearing 132°	Toward the north northeast at 31 mph	136 mi southeast of the radar	131 mi east southeast of the radar	0.8 mi
G1	224 mi northeast of the radar224 mi from the radar, bearing 50°	Toward the north northeast at 35 mph	241 mi northeast of the radar	-	1.4 mi
O9	125 mi southwest of the radar125 mi from the radar, bearing 221°	Toward the northeast at 32 mph	14 mi south of Chiefland, FL	-	1.5 mi
C8	55 mi west of the radar55 mi from the radar, bearing 274°	Toward the north northeast at 37 mph	51 mi west northwest of the radar	15 mi south of Waycross, GA	0.3 mi
O6	58 mi west northwest of the radar58 mi from the radar, bearing 289°	Toward the north northeast at 41 mph	14 mi south southwest of Waycross, GA	5 mi north of Sunnyside, GA	1 mi
V5	11 mi east northeast of Five Points, FL48 mi from the radar, bearing 255°	Toward the north northeast at 68 mph	-	-	3.2 mi
J8	2 mi east northeast of Jesup, GA78 mi from the radar, bearing 353°	Toward the north northeast at 44 mph	4 mi northwest of Hinesville, GA	-	1.4 mi
V4	11 mi north northwest of High Springs, FL67 mi from the radar, bearing 238°	Toward the north northeast at 51 mph	-	-	4.8 mi
N0	9 mi southeast of Watertown, FL55 mi from the radar, bearing 240°	First seen this scan	-	-	0 mi
E1	3 mi north northwest of High Springs, FL69 mi from the radar, bearing 232°	First seen this scan	-	-	0 mi
I7	6 mi southeast of Alachua, FL68 mi from the radar, bearing 219°	Toward the north northeast at 47 mph	7 mi east of Lake Butler, FL	5 mi east northeast of Macclenny, FL	0.7 mi
H2	9 mi east of Watertown, FL50 mi from the radar, bearing 247°	Toward the north northeast at 91 mph	9 mi south southwest of Folkston, GA	-	1.7 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=KJAX, the times of its frames, and /radar/s/KJAX/storms.json, the storms it tracks.