Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
807
UXUS97 KBOU 210142
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1941 MDT Thursday, June 20, 2024
This forecast is for Friday, June 21, 2024:
If the trigger temperature of 77.4 F/25.2 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 914 ft/min (4.6 m/s)
Maximum height of thermals.................. 16013 ft MSL (10733 ft AGL)
Forecast maximum temperature................... 88.0 F/31.6 C
Time of trigger temperature.................... 1045 MDT
Time of overdevelopment........................ 1800 MDT
Middle/high clouds during soaring window....... Broken/overcast thin middle
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 12512 ft MSL (7232 ft AGL)
Thermal soaring outlook for Saturday 06/22..... Good
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1800 MDT)......... No change
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1800 MDT)................ Weak PVA
Potential height of wave....................... 14373 ft MSL (9093 ft AGL)
Wave soaring outlook for Saturday 06/22........ Fair
Remarks...
Sunrise/Sunset.................... 05:31:48 / 20:31:08 MDT
Total possible sunshine........... 14 hr 59 min 21 sec (899 min 21 sec)
Altitude of sun at 13:01:28 MDT... 73.66 degrees
Upper air data from numerical model forecast valid on 06/21/2024 at 0600 MDT
Freezing level.................. 15354 ft MSL (10074 ft AGL)
Convective condensation level... 13126 ft MSL (7846 ft AGL)
Lifted condensation level....... 14305 ft MSL (9025 ft AGL)
Lifted index.................... -3.3
K index......................... +29.9
Height Temperature Wind Wind Spd Lapse Rate ConvectionT Thermal Lift Rate
ft MSL deg C deg F Dir kt m/s C/km F/kft deg C deg F Index fpm m/s
--------------------------------------------------------------------------------
50000 -61.7 -79.1 240 53 27 4.0 2.2 M M M M M
45000 -55.8 -68.4 245 73 37 3.9 2.1 M M M M M
40000 -49.3 -56.7 240 87 45 5.5 3.0 M M M M M
38000 -46.0 -50.8 230 73 38 5.5 3.0 M M M M M
36000 -42.7 -44.9 220 62 32 6.0 3.3 M M M M M
34000 -37.7 -35.9 220 54 28 8.5 4.7 M M M M M
32000 -32.7 -26.9 215 47 24 8.3 4.6 M M M M M
30000 -27.9 -18.2 215 41 21 8.0 4.4 49.3 120.7 13.7 M M
29000 -25.5 -13.9 215 38 20 8.0 4.4 48.6 119.6 13.4 M M
28000 -22.7 -8.9 215 35 18 6.2 3.4 47.8 118.0 12.8 M M
27000 -20.8 -5.4 215 31 16 6.3 3.5 46.3 115.4 11.8 M M
26000 -19.0 -2.2 215 28 14 6.4 3.5 45.1 113.1 10.9 M M
25000 -17.1 1.2 220 25 13 6.1 3.3 43.9 111.1 10.1 M M
24000 -15.5 4.1 220 20 10 5.4 3.0 42.3 108.1 8.8 M M
23000 -13.9 7.0 220 15 8 5.4 3.0 40.7 105.2 7.5 M M
22000 -12.4 9.7 225 10 5 5.8 3.2 39.2 102.6 6.3 M M
21000 -10.4 13.3 235 8 4 6.7 3.7 38.0 100.4 5.3 M M
20000 -8.5 16.7 250 7 4 6.7 3.7 36.9 98.5 4.4 M M
19500 -7.5 18.5 255 7 3 6.8 3.7 36.5 97.6 4.0 M M
19000 -6.6 20.1 265 6 3 6.2 3.4 35.9 96.7 3.5 M M
18500 -5.7 21.7 265 7 3 6.2 3.4 35.3 95.5 2.9 M M
18000 -4.8 23.4 270 7 4 6.3 3.4 34.7 94.5 2.4 M M
17500 -3.9 25.0 265 7 4 6.4 3.5 34.1 93.4 1.9 M M
17000 -3.0 26.6 265 8 4 6.4 3.5 33.5 92.4 1.3 M M
16500 -2.1 28.2 260 8 4 5.8 3.2 32.9 91.3 0.7 M M
16000 -1.3 29.7 260 8 4 5.8 3.2 32.3 90.1 0.1 M M
15500 -0.5 31.1 260 8 4 6.2 3.4 31.6 88.9 -0.5 881 4.5
15000 0.5 32.9 255 9 5 6.4 3.5 31.1 87.9 -1.1 838 4.3
14500 1.4 34.5 255 10 5 6.8 3.7 30.5 86.9 -1.6 796 4.0
14000 3.1 37.6 245 11 6 8.0 4.4 30.0 86.0 -2.1 723 3.7
13500 4.3 39.7 240 12 6 7.8 4.3 29.7 85.5 -2.4 673 3.4
13000 5.4 41.7 240 14 7 7.7 4.2 29.4 84.9 -2.7 624 3.2
12500 6.5 43.7 235 16 8 7.6 4.2 29.1 84.3 -3.1 576 2.9
12000 7.6 45.7 235 18 9 7.4 4.1 28.7 83.7 -3.5 528 2.7
11500 8.7 47.7 230 20 11 7.4 4.1 28.3 83.0 -3.8 481 2.4
11000 9.8 49.6 230 23 12 7.2 3.9 28.0 82.3 -4.2 433 2.2
10500 10.9 51.6 230 25 13 4.2 2.3 27.6 81.7 -4.6 386 2.0
10250 11.0 51.8 230 26 13 4.4 2.4 27.0 80.7 -5.2 374 1.9
10000 11.6 52.9 230 27 14 9.5 5.2 26.9 80.4 -5.3 349 1.8
9750 12.3 54.1 225 28 15 9.6 5.2 26.9 80.3 -5.4 321 1.6
9500 13.0 55.4 225 30 15 7.8 4.3 26.8 80.3 -5.4 293 1.5
9250 13.4 56.1 225 31 16 5.0 2.8 26.5 79.8 -5.7 273 1.4
9000 13.8 56.8 225 32 16 6.5 3.5 26.2 79.2 -6.1 253 1.3
8750 14.4 57.9 225 32 17 8.1 4.5 26.0 78.9 -6.3 230 1.2
8500 14.9 58.8 225 33 17 6.5 3.6 25.9 78.6 -6.5 206 1.0
8250 15.3 59.5 225 33 17 5.3 2.9 25.6 78.0 -6.8 187 1.0
8000 15.7 60.3 225 33 17 5.4 3.0 25.2 77.4 -7.2 169 0.9
7750 16.0 60.8 220 32 17 5.3 2.9 24.9 76.8 -7.6 150 0.8
7500 16.4 61.5 220 32 16 5.1 2.8 24.5 76.2 -8.0 132 0.7
7250 16.7 62.1 220 32 17 4.9 2.7 24.2 75.5 -8.4 115 0.6
7000 17.0 62.6 220 33 17 5.4 3.0 23.8 74.9 -8.8 97 0.5
6750 17.4 63.3 220 34 18 4.6 2.5 23.5 74.3 -9.2 79 0.4
6500 17.6 63.7 215 32 17 1.4 0.8 23.0 73.4 -9.8 67 0.3
6250 17.6 63.7 215 29 15 0.7 0.4 22.3 72.1 -10.5 60 0.3
6000 17.6 63.7 210 26 13 -0.1 -0.0 21.6 70.9 -11.3 53 0.3
5750 17.5 63.5 205 22 11 2.3 1.2 20.9 69.6 -12.1 46 0.2
5500 17.9 64.2 205 16 8 9.4 5.2 20.6 69.1 -12.4 27 0.1
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
06/21/2024 at 0900 MDT | 06/21/2024 at 1200 MDT
|
CAPE... +121.8 LI... -1.0 | CAPE... +319.3 LI... -0.8
CINH... -79.7 K Index... +25.7 | CINH... -40.2 K Index... +24.8
|
Height Temperature Wnd WndSpd Lapse Rate | Temperature Wnd WndSpd Lapse Rate
ft MSL deg C deg F Dir kt m/s C/km F/kft | deg C deg F Dir kt m/s C/km F/kft
--------------------------------------------------------------------------------
50000 -63.2 -81.8 240 56 29 3.0 1.7 | -62.1 -79.8 235 55 28 3.9 2.1
45000 -57.5 -71.5 245 76 39 5.2 2.9 | -55.9 -68.6 240 72 37 4.5 2.5
40000 -48.8 -55.8 240 83 43 6.9 3.8 | -48.4 -55.1 240 90 47 6.4 3.5
38000 -44.7 -48.5 235 77 40 6.9 3.8 | -44.6 -48.3 235 88 45 6.4 3.5
36000 -40.5 -40.9 230 71 37 6.9 3.8 | -40.8 -41.4 230 85 44 6.3 3.5
34000 -36.4 -33.5 225 66 34 6.9 3.8 | -37.4 -35.3 230 79 41 5.7 3.1
32000 -32.3 -26.1 220 62 32 6.8 3.7 | -33.9 -29.0 225 72 37 5.6 3.1
30000 -28.3 -18.9 220 57 29 6.8 3.7 | -29.2 -20.6 230 61 31 7.3 4.0
29000 -25.8 -14.4 220 54 28 6.9 3.8 | -27.0 -16.6 230 55 29 7.4 4.1
28000 -23.9 -11.0 220 51 26 6.6 3.6 | -24.9 -12.8 230 51 26 7.4 4.0
27000 -21.9 -7.4 230 46 23 6.6 3.6 | -22.7 -8.9 230 49 25 7.4 4.1
26000 -20.0 -4.0 240 41 21 6.6 3.6 | -20.5 -4.9 235 47 24 7.5 4.1
25000 -18.0 -0.4 250 38 20 6.9 3.8 | -18.4 -1.1 235 45 23 7.2 3.9
24000 -15.8 3.6 255 35 18 7.6 4.1 | -16.3 2.7 240 41 21 6.5 3.5
23000 -13.6 7.5 265 31 16 7.6 4.1 | -14.3 6.3 245 38 19 6.5 3.6
22000 -11.3 11.7 270 29 15 7.1 3.9 | -12.3 9.9 250 35 18 7.1 3.9
21000 -9.5 14.9 270 23 12 6.1 3.4 | -10.0 14.0 250 30 15 8.1 4.5
20000 -7.8 18.0 270 17 9 6.2 3.4 | -7.7 18.1 250 24 13 8.3 4.5
19500 -6.9 19.6 270 14 7 6.3 3.5 | -6.5 20.3 245 22 11 8.7 4.8
19000 -6.1 21.0 275 12 6 4.9 2.7 | -5.5 22.1 245 20 10 5.3 2.9
18500 -5.3 22.5 280 11 6 5.0 2.7 | -4.7 23.5 250 20 10 5.5 3.0
18000 -4.6 23.7 285 10 5 5.7 3.1 | -3.9 25.0 255 20 10 5.5 3.0
17500 -3.5 25.7 290 10 5 7.2 3.9 | -3.1 26.4 255 20 10 5.4 2.9
17000 -2.5 27.5 295 9 5 7.2 3.9 | -2.3 27.9 255 19 10 5.3 2.9
16500 -1.4 29.5 300 8 4 7.2 3.9 | -1.5 29.3 255 19 10 6.0 3.3
16000 -0.4 31.3 305 7 4 7.2 4.0 | -0.7 30.7 255 18 9 6.0 3.3
15500 0.6 33.1 315 6 3 6.6 3.6 | 0.7 33.3 260 17 8 7.5 4.1
15000 1.8 35.2 325 5 3 6.1 3.4 | 1.8 35.2 260 16 8 7.3 4.0
14500 2.7 36.9 325 5 3 6.9 3.8 | 2.8 37.0 265 15 8 7.7 4.3
14000 3.7 38.7 325 5 3 7.0 3.9 | 4.0 39.2 265 14 7 7.8 4.3
13500 4.7 40.5 320 5 3 7.6 4.2 | 5.1 41.2 270 13 7 8.1 4.5
13000 5.9 42.6 315 5 3 8.0 4.4 | 6.3 43.3 275 13 7 8.3 4.6
12500 7.0 44.6 315 6 3 7.9 4.3 | 7.5 45.5 280 12 6 8.6 4.7
12000 8.1 46.6 310 7 4 7.5 4.1 | 8.8 47.8 285 13 7 8.9 4.9
11500 9.2 48.6 305 8 4 7.6 4.2 | 10.1 50.2 290 13 7 8.7 4.8
11000 10.4 50.7 305 10 5 7.7 4.2 | 11.3 52.3 300 14 7 7.7 4.2
10500 11.5 52.7 305 11 6 4.4 2.4 | 12.5 54.5 305 15 8 3.9 2.1
10250 11.7 53.1 305 12 6 5.4 3.0 | 12.6 54.7 305 16 8 4.3 2.3
10000 12.4 54.3 310 13 7 10.5 5.8 | 13.2 55.8 305 16 8 9.8 5.4
9750 13.1 55.6 310 14 7 9.4 5.2 | 13.8 56.8 310 16 8 8.5 4.7
9500 13.8 56.8 310 15 8 8.6 4.7 | 14.4 57.9 310 16 8 8.2 4.5
9250 14.3 57.7 310 16 8 6.4 3.5 | 14.9 58.8 315 15 8 6.9 3.8
9000 14.8 58.6 310 17 9 7.5 4.1 | 15.4 59.7 315 13 7 7.0 3.8
8750 15.4 59.7 310 18 9 8.7 4.8 | 15.8 60.4 320 11 6 6.9 3.8
8500 16.0 60.8 310 19 10 7.7 4.2 | 16.3 61.3 325 9 4 7.9 4.3
8250 16.5 61.7 310 20 10 6.6 3.6 | 16.9 62.4 330 7 4 9.3 5.1
8000 17.0 62.6 310 20 10 6.9 3.8 | 17.6 63.7 335 6 3 9.2 5.1
7750 17.5 63.5 310 20 10 7.7 4.2 | 18.3 64.9 340 6 3 9.0 4.9
7500 18.0 64.4 310 20 10 6.8 3.7 | 19.0 66.2 340 6 3 10.0 5.5
7250 18.5 65.3 310 19 10 6.1 3.3 | 19.8 67.6 340 6 3 11.1 6.1
7000 18.9 66.0 310 18 10 5.9 3.3 | 20.6 69.1 340 5 3 10.4 5.7
6750 19.3 66.7 310 17 9 5.5 3.0 | 21.3 70.3 340 5 3 9.6 5.3
6500 19.7 67.5 310 16 8 7.5 4.1 | 22.0 71.6 340 5 3 10.3 5.7
6250 20.3 68.5 305 13 7 9.2 5.1 | 22.8 73.0 345 5 3 11.6 6.4
6000 20.9 69.6 305 10 5 7.4 4.1 | 23.7 74.7 345 5 3 9.7 5.3
5750 21.5 70.7 300 8 4 11.7 6.4 | 24.4 75.9 345 5 2 13.8 7.6
5500 22.8 73.0 300 7 4 23.2 12.8 | 25.9 78.6 345 5 2 26.3 14.4
06/21/2024 at 1500 MDT | 06/21/2024 at 1800 MDT
|
CAPE... +534.5 LI... -2.9 | CAPE... +476.4 LI... -1.9
CINH... -16.9 K Index... +27.9 | CINH... -171.5 K Index... +32.2
|
Height Temperature Wnd WndSpd Lapse Rate | Temperature Wnd WndSpd Lapse Rate
ft MSL deg C deg F Dir kt m/s C/km F/kft | deg C deg F Dir kt m/s C/km F/kft
--------------------------------------------------------------------------------
50000 -61.7 -79.1 235 53 27 4.5 2.5 | -62.4 -80.3 245 56 29 3.2 1.8
45000 -54.7 -66.5 240 71 37 4.3 2.4 | -56.0 -68.8 245 76 39 5.5 3.0
40000 -47.8 -54.0 240 89 46 6.1 3.3 | -47.7 -53.9 245 84 43 6.1 3.3
38000 -44.1 -47.4 240 86 44 6.1 3.3 | -44.1 -47.4 245 77 40 6.1 3.3
36000 -40.5 -40.9 235 83 43 6.1 3.3 | -40.4 -40.7 245 70 36 6.1 3.3
34000 -37.0 -34.6 235 76 39 5.8 3.2 | -36.8 -34.2 245 64 33 6.1 3.4
32000 -33.5 -28.3 240 68 35 5.8 3.2 | -32.6 -26.7 250 57 29 6.3 3.5
30000 -29.5 -21.1 240 63 33 6.8 3.8 | -28.4 -19.1 255 48 25 7.1 3.9
29000 -26.9 -16.4 240 61 32 6.8 3.8 | -26.3 -15.3 255 44 23 7.1 3.9
28000 -24.8 -12.6 240 59 30 7.4 4.1 | -24.1 -11.4 260 40 21 7.8 4.3
27000 -22.6 -8.7 240 54 28 7.5 4.1 | -21.8 -7.2 260 39 20 7.9 4.3
26000 -20.4 -4.7 235 49 25 7.5 4.1 | -19.5 -3.1 260 38 19 7.9 4.4
25000 -18.2 -0.8 235 45 23 7.4 4.0 | -17.2 1.0 265 37 19 7.8 4.3
24000 -16.2 2.8 235 42 21 6.8 3.7 | -15.1 4.8 260 36 18 7.2 3.9
23000 -14.2 6.4 235 39 20 6.8 3.8 | -13.0 8.6 255 35 18 7.3 4.0
22000 -12.3 9.9 230 36 18 6.7 3.7 | -10.9 12.4 250 34 18 7.0 3.9
21000 -10.4 13.3 230 31 16 6.3 3.5 | -9.1 15.6 245 33 17 6.1 3.4
20000 -8.5 16.7 235 26 13 6.3 3.5 | -7.4 18.7 240 32 17 6.2 3.4
19500 -7.6 18.3 235 24 12 6.3 3.4 | -6.0 21.2 235 32 16 6.1 3.3
19000 -6.6 20.1 235 21 11 7.3 4.0 | -5.2 22.6 230 31 16 5.7 3.2
18500 -5.6 21.9 235 19 10 7.2 4.0 | -4.4 24.1 225 31 16 5.8 3.2
18000 -4.5 23.9 240 17 9 7.3 4.0 | -3.6 25.5 220 30 16 5.9 3.2
17500 -3.5 25.7 245 17 9 7.4 4.1 | -2.7 27.1 210 29 15 5.9 3.3
17000 -2.4 27.7 250 16 8 7.4 4.0 | -1.9 28.6 205 29 15 6.2 3.4
16500 -1.3 29.7 255 15 8 7.7 4.3 | -0.9 30.4 200 28 14 7.3 4.0
16000 -0.2 31.6 255 14 7 7.7 4.2 | 0.1 32.2 195 26 13 7.3 4.0
15500 1.0 33.8 260 14 7 8.0 4.4 | 1.2 34.2 195 24 13 7.1 3.9
15000 2.2 36.0 260 13 7 8.1 4.5 | 2.2 36.0 190 22 11 7.1 3.9
14500 3.3 37.9 265 12 6 8.2 4.5 | 3.2 37.8 185 20 10 7.6 4.2
14000 5.1 41.2 260 11 6 8.4 4.6 | 4.3 39.7 185 18 9 7.8 4.3
13500 6.3 43.3 255 10 5 8.0 4.4 | 5.5 41.9 180 16 8 8.1 4.5
13000 7.4 45.3 255 9 5 7.8 4.3 | 6.7 44.1 175 14 7 8.6 4.7
12500 8.6 47.5 250 8 4 8.1 4.4 | 8.0 46.4 175 12 6 8.5 4.6
12000 9.8 49.6 240 7 4 8.4 4.6 | 9.1 48.4 170 10 5 7.9 4.3
11500 11.0 51.8 230 6 3 8.2 4.5 | 10.3 50.5 165 9 4 7.9 4.3
11000 12.1 53.8 205 4 2 7.5 4.1 | 11.4 52.5 165 7 3 7.5 4.1
10500 13.3 55.9 165 4 2 3.4 1.9 | 12.5 54.5 160 5 2 6.6 3.6
10250 13.4 56.1 165 4 2 5.3 2.9 | 13.0 55.4 160 4 2 6.1 3.3
10000 14.2 57.6 160 4 2 12.2 6.7 | 13.5 56.3 165 2 1 7.0 3.8
9750 14.9 58.8 155 4 2 10.8 5.9 | 13.9 57.0 180 1 1 6.7 3.7
9500 15.7 60.3 150 4 2 9.6 5.3 | 14.4 57.9 290 1 0 6.9 3.8
9250 16.3 61.3 150 4 2 8.2 4.5 | 14.9 58.8 315 2 1 7.2 3.9
9000 17.0 62.6 150 4 2 10.5 5.8 | 15.4 59.7 315 4 2 5.7 3.1
8750 17.8 64.0 150 4 2 11.6 6.4 | 15.7 60.3 315 5 3 4.5 2.5
8500 18.6 65.5 145 4 2 10.4 5.7 | 16.1 61.0 315 7 3 4.8 2.7
8250 19.3 66.7 145 4 2 9.1 5.0 | 16.4 61.5 315 8 4 5.3 2.9
8000 20.0 68.0 145 4 2 9.9 5.5 | 16.8 62.2 315 10 5 4.3 2.4
7750 20.8 69.4 145 4 2 10.8 5.9 | 17.0 62.6 310 12 6 2.6 1.4
7500 21.6 70.9 145 4 2 10.1 5.5 | 17.1 62.8 310 13 7 2.2 1.2
7250 22.3 72.1 145 4 2 9.7 5.3 | 17.2 63.0 305 15 8 1.7 0.9
7000 23.1 73.6 145 3 2 9.7 5.3 | 17.3 63.1 305 17 9 1.5 0.8
6750 23.8 74.8 145 3 2 10.0 5.5 | 17.3 63.1 305 19 10 -0.5 -0.3
6500 24.6 76.3 145 3 2 10.5 5.8 | 17.3 63.1 300 20 10 1.2 0.6
6250 25.4 77.7 145 3 2 11.2 6.1 | 17.4 63.3 300 21 11 4.2 2.3
6000 26.2 79.2 145 3 2 9.7 5.3 | 17.6 63.7 295 22 11 2.4 1.3
5750 27.0 80.6 145 3 2 15.4 8.5 | 17.7 63.9 295 23 12 5.0 2.8
5500 28.6 83.5 145 3 2 29.7 16.3 | 18.4 65.1 295 21 11 16.8 9.2
________________________________________________________________________________
This product is issued twice per day, once by approximately 0630 MST/0730 MDT
(1330 UTC) and again by approximately 1830 MST/1930 MDT (0130 UTC). It is not
continuously monitored nor updated after its initial issuance.
The information contained herein is based on rawinsonde observation and/or
numerical weather prediction model data taken near the old Stapleton
Airport site in Denver, Colorado at
North Latitude: 39 deg 46 min 5.016 sec
West Longitude: 104 deg 52 min 9.984 sec
Elevation: 5285 feet (1611 meters)
and may not be representative of other areas along the Front Range of the
Colorado Rocky Mountains. Note that some elevations in numerical weather
prediction models differ from actual station elevations, which can lead to
data which appear to be below ground. Erroneous data such as these should
not be used.
The content and format of this report as well as the issuance times are subject
to change without prior notice. Comments and suggestions are welcome and should
be directed to one of the addresses or phone numbers shown at the bottom of this
page. To expedite a response to comments, be sure to mention your interest in
the soaring forecast.
DEFINITIONS:
CAPE (Convective Available Potential Energy) - An integrated measure of the
energy available for convective development, also known as the positive
area on a thermodynamic diagram. Units are Joules per kilogram. Larger
values are indicative of greater instability and the possibility of
stronger convective activity, including thunderstorms. Values around or
greater than 1000 suggest the possibility of severe weather should
convective activity develop.
CINH (Convective Inhibition) - An integrated measure of the amount of energy
needed to initiate convective activity, also known as the negative area on
a thermodynamic diagram. Units are Joules per kilogram. The more negative
this number, the more energy is required to initiate convection. This
inhibitive energy can be overcome through surface heating, cooling aloft,
lifting mechanisms (orographic, frontal, gravity waves, etc.)
Convective Condensation Level - The height to which an air parcel possessing the
average saturation mixing ratio in the lowest 4000 feet of the airmass,
if heated sufficiently from below, will rise dry adiabatically until it
just becomes saturated. It estimates the base of cumulus clouds that are
produced by surface heating only.
Convection Temperature (ConvectionT) - The surface temperature required to make
the airmass dry adiabatic up to the given level. It can be considered a
"trigger temperature" for that level.
Freezing Level - The height where the temperature is zero degrees Celsius.
Height of Stable Layer - The height (between 12,000 and 18,000 feet above
mean sea level) where the smallest lapse rate exists. The location and
existence of this feature is important in the generation of mountain
waves.
K Index - A measure of stability which combines the temperature difference
between approximately 5,000 and 18,000 feet above the surface, the amount
of moisture at approximately 5,000 feet above the surface, and a measure
of the dryness at approximately 10,000 feet above the surface. Larger
positive numbers indicate more instability and a greater likelihood of
thunderstorm development. One interpretation of K index values regarding
soaring in the western United States is given in WMO Technical Note 158
and is reproduced in the following table:
below -10 no or weak thermals
-10 to 5 dry thermals or 1/8 cumulus with moderate thermals
5 to 15 good soaring conditions
15 to 20 good soaring conditions with occasional showers
20 to 30 excellent soaring conditions, but increasing
probability of showers and thunderstorms
above 30 more than 60 percent probability of thunderstorms
Lapse Rate - The change with height of the temperature. Negative values indicate
inversions.
Lifted Condensation Level - The height to which an air parcel possessing the
average dew point in the lowest 4000 feet of the airmass and the forecast
maximum temperature must be lifted dry adiabatically to attain saturation.
Lifted Index (LI) - The difference between the environmental temperature at a
level approximately 18,000 feet above the surface and the temperature of
an air parcel lifted dry adiabatically from the surface to its lifted
condensation level and then pseudoadiabatically thereafter to this same
level. The parcel`s initial temperature is the forecast maximum
temperature and its dew point is the average dew point in the lowest 4000
feet of the airmass. Negative values are indicative of instability with
positive values showing stable conditions.
Lift Rate - An experimental estimate of the strength of thermals. It is
computed the same way as the maximum rate of lift but uses the actual
level rather than the maximum height of thermals in the calculation.
Also, none of the empirical adjustments based on cloudiness and K-index
are applied to these calculations.
Maximum Height of Thermals - The height where the dry adiabat through the
forecast maximum temperature intersects the environmental temperature.
Maximum Rate of Lift - An estimate of the maximum strength of thermals. It
is computed from an empirical formula which combines the expected maximum
height of thermals with the difference in the environmental temperatures
between the maximum height of thermals and the temperature 4,000 feet
above the ground. After this computation, further empirical adjustments
are made based on the value of the K-index and the amount and opacity of
middle and high level cloudiness expected between the time of trigger
temperature and the time of overdevelopment.
Middle/High Clouds - The amount and opacity of middle (altostratus, altocumulus)
or high (cirrus, cirrostratus, cirrocumulus) clouds. Broken means that
between 60% and 90% of the sky is covered by the cloud, with overcast
conditions occurring when more than 90% of the sky is covered by the cloud.
Thin implies that the clouds are predominantly transparent, meaning that
some sunlight is reaching the ground, in contrast to opaque which suggests
that little sunlight is reaching the ground.
Potential Height of Wave - The minimum of the following two heights:
1. Level above the height of stable layer (or 14,000 feet if none exists)
where the wind direction changes by 30 degrees or more
2. Level above the height of stable layer (or 14,000 feet if none exists)
where the wind speed no longer increases with height
PVA/NVA - Positive vorticity advection (PVA)/negative vorticity advection (NVA)
on the 500 millibar isobaric surface (approximately 18,000 feet above mean
sea level). Weak PVA has been shown to assist in mountain wave soaring.
Soaring Window - The time between the time the trigger temperature is reached
and the time of overdevelopment.
Thermal Index - The difference between the environmental temperature and the
temperature at a particular level determined by following the dry adiabat
through the forecast maximum temperature up to that level. Negative values
are indicative of thermal lift.
Thermal Soaring Index - An adjective rating (for sailplanes) based on the
computed maximum rate of lift, and the wind speed and middle and high
cloud cover expected during the soaring window (the time of the trigger
temperature and the time of overdevelopment) according to the following:
Maximum rate of lift Adjective Rating
>= 800 fpm Excellent
>= 400 and < 800 fpm Good
>= 200 and < 400 fpm Fair
< 200 fpm Poor
Time of Overdevelopment - The time one or more of the following phenomena,
which essentially shut off thermal lift, is expected to occur:
1. formation of broken to overcast convective cloud cover
2. formation of scattered to numerous downbursts
3. initiation of widespread precipitation
Time of Trigger Temperature - The time the surface temperature is expected to
reach the trigger temperature.
Trigger Temperature - The surface temperature required to make the first 4000
feet of the atmosphere dry adiabatic.
Wave Soaring Index - An empirical, adjective rating (for sailplanes) which
attempts to combine a variety of phenomena important in mountain wave
soaring into a single index number. Objective points are assigned to
these phenomena: wind speed and direction at 14,000 ft MSL, the static
stability in the 12,000-18,000 ft MSL layer, the wind speed gradient above
the stable layer, jet stream location and frontal and upper trough
movements.
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