Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
663
UXUS97 KBOU 131232
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0631 MDT Wednesday, August 13, 2025
This forecast is for Wednesday, August 13, 2025:
If the trigger temperature of 87.1 F/30.6 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1418 ft/min (7.2 m/s)
Maximum height of thermals.................. 20101 ft MSL (14819 ft AGL)
Forecast maximum temperature................... 97.0 F/36.6 C
Time of trigger temperature.................... 1045 MDT
Time of overdevelopment........................ 1500 MDT
Middle/high clouds during soaring window....... None
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 17592 ft MSL (12310 ft AGL)
Thermal soaring outlook for Thursday 08/14..... Excellent
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)................ Neither
Potential height of wave....................... 16132 ft MSL (10850 ft AGL)
Wave soaring outlook for Thursday 08/14........ Poor
Remarks... Scattered virga with microbusts after 1500 MDT
Sunrise/Sunset.................... 06:10:17 / 19:58:14 MDT
Total possible sunshine........... 13 hr 47 min 57 sec (827 min 57 sec)
Altitude of sun at 13:04:16 MDT... 64.62 degrees
Upper air data from numerical model forecast valid on 08/13/2025 at 0600 MDT
Freezing level.................. 16116 ft MSL (10834 ft AGL)
Convective condensation level... 17548 ft MSL (12266 ft AGL)
Lifted condensation level....... 18968 ft MSL (13686 ft AGL)
Lifted index.................... -1.8
K index......................... +19.5
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 -62.9 -81.2 290 12 6 -0.0 -0.0 M M M M M
45000 -61.5 -78.7 295 18 9 3.3 1.8 M M M M M
40000 -55.8 -68.4 295 24 12 7.4 4.1 M M M M M
38000 -51.2 -60.2 300 23 12 7.6 4.2 M M M M M
36000 -46.7 -52.1 305 22 11 7.5 4.1 M M M M M
34000 -41.0 -41.8 300 20 10 8.6 4.7 M M M M M
32000 -35.8 -32.4 295 19 10 8.8 4.8 M M M M M
30000 -30.7 -23.3 295 17 9 8.4 4.6 44.6 112.2 6.4 M M
29000 -28.2 -18.8 295 16 8 8.4 4.6 44.1 111.4 6.2 M M
28000 -25.7 -14.3 300 16 8 7.8 4.3 43.6 110.6 5.9 M M
27000 -23.4 -10.1 300 15 7 7.8 4.3 42.8 109.0 5.3 M M
26000 -21.1 -6.0 305 14 7 7.8 4.3 42.0 107.7 4.7 M M
25000 -18.7 -1.7 310 13 7 7.8 4.3 41.4 106.6 4.3 M M
24000 -16.4 2.5 310 13 7 7.7 4.3 40.6 105.1 3.6 M M
23000 -14.1 6.6 305 14 7 7.7 4.2 39.9 103.8 3.1 M M
22000 -11.7 10.9 305 15 8 6.8 3.7 39.2 102.6 2.6 M M
21000 -10.1 13.8 305 15 8 5.5 3.0 37.7 99.8 1.3 M M
20000 -8.5 16.7 300 15 8 5.6 3.1 36.2 97.1 -0.0 1416 7.2
19500 -7.6 18.3 300 15 8 5.6 3.1 35.5 95.9 -0.6 1377 7.0
19000 -6.9 19.6 300 15 8 5.6 3.1 34.8 94.6 -1.3 1339 6.8
18500 -6.1 21.0 305 15 8 5.8 3.2 34.1 93.3 -2.0 1300 6.6
18000 -5.3 22.5 305 16 8 7.2 3.9 33.4 92.1 -2.7 1262 6.4
17500 -4.1 24.6 310 16 8 8.5 4.7 33.2 91.7 -3.0 1211 6.2
17000 -2.8 27.0 310 16 8 8.6 4.7 33.0 91.4 -3.2 1159 5.9
16500 -0.8 30.6 315 17 9 9.8 5.4 32.9 91.3 -3.4 1075 5.5
16000 0.7 33.3 320 18 9 9.8 5.4 32.9 91.3 -3.4 1017 5.2
15500 2.1 35.8 320 18 9 9.4 5.1 32.9 91.2 -3.5 959 4.9
15000 3.5 38.3 320 18 9 9.4 5.1 32.8 91.1 -3.6 903 4.6
14500 4.9 40.8 325 18 9 9.9 5.4 32.8 91.1 -3.6 845 4.3
14000 6.4 43.5 325 18 9 9.9 5.4 32.8 91.1 -3.6 786 4.0
13500 7.8 46.0 325 18 9 9.5 5.2 32.9 91.1 -3.7 728 3.7
13000 9.2 48.6 330 18 9 9.3 5.1 32.8 91.0 -3.8 671 3.4
12500 10.6 51.1 330 18 10 9.2 5.1 32.7 90.9 -3.8 615 3.1
12000 12.0 53.6 330 18 9 9.2 5.0 32.6 90.7 -4.0 559 2.8
11500 13.3 55.9 330 18 9 8.9 4.9 32.5 90.5 -4.1 503 2.6
11000 14.6 58.3 330 18 9 8.3 4.6 32.3 90.2 -4.3 451 2.3
10500 15.9 60.6 330 17 9 4.7 2.6 32.2 89.9 -4.5 398 2.0
10250 16.1 61.0 330 17 9 5.7 3.1 31.6 88.9 -5.1 384 2.0
10000 16.8 62.2 325 16 8 11.1 6.1 31.6 89.0 -5.1 355 1.8
9750 17.5 63.5 325 16 8 10.1 5.5 31.7 89.0 -5.1 326 1.7
9500 18.3 64.9 325 15 8 8.8 4.8 31.7 89.0 -5.1 297 1.5
9250 18.8 65.8 325 15 8 6.8 3.7 31.5 88.7 -5.3 273 1.4
9000 19.3 66.7 325 15 7 8.1 4.4 31.3 88.4 -5.5 250 1.3
8750 20.0 68.0 320 14 7 9.0 4.9 31.2 88.2 -5.6 223 1.1
8500 20.6 69.1 320 14 7 8.0 4.4 31.1 88.1 -5.7 197 1.0
8250 21.1 70.0 315 14 7 7.3 4.0 31.0 87.7 -5.9 173 0.9
8000 21.7 71.1 315 14 7 6.5 3.6 30.8 87.4 -6.2 150 0.8
7750 22.1 71.8 310 14 7 5.4 3.0 30.5 86.8 -6.5 130 0.7
7500 22.5 72.5 310 13 7 5.1 2.8 30.1 86.2 -6.8 110 0.6
7250 22.8 73.0 305 13 7 4.6 2.5 29.7 85.5 -7.2 93 0.5
7000 23.2 73.8 300 13 6 4.9 2.7 29.4 84.8 -7.6 75 0.4
6750 23.5 74.3 295 12 6 1.8 1.0 28.9 84.0 -8.1 59 0.3
6500 23.3 73.9 285 12 6 -5.5 -3.0 28.0 82.5 -9.0 56 0.3
6250 22.7 72.9 275 11 6 -8.7 -4.8 26.7 80.0 -10.4 68 0.3
6000 22.0 71.6 265 10 5 -6.5 -3.6 25.4 77.7 -11.8 80 0.4
5750 21.4 70.5 250 11 6 -11.8 -6.5 24.1 75.3 -13.2 92 0.5
5500 19.9 67.8 235 9 5 -24.2 -13.3 21.9 71.5 -15.4 128 0.7
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
08/13/2025 at 0900 MDT | 08/13/2025 at 1200 MDT
|
CAPE... 0.0 LI... +0.9 | CAPE... +1.1 LI... +0.7
CINH... 0.0 K Index... +20.4 | CINH... -10.4 K Index... +18.5
|
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 -81.8 305 9 5 -0.4 -0.2 | -62.7 -80.9 270 5 3 -0.4 -0.2
45000 -61.9 -79.4 305 16 8 4.0 2.2 | -61.6 -78.9 295 13 6 3.5 1.9
40000 -55.4 -67.7 300 24 13 7.6 4.2 | -55.3 -67.5 295 30 15 7.8 4.3
38000 -50.7 -59.3 295 24 12 7.7 4.2 | -50.6 -59.1 295 30 15 7.8 4.3
36000 -46.1 -51.0 295 23 12 7.7 4.2 | -46.0 -50.8 295 29 15 7.9 4.3
34000 -40.6 -41.1 290 21 11 8.2 4.5 | -41.0 -41.8 290 27 14 8.3 4.5
32000 -35.7 -32.3 280 19 10 8.3 4.6 | -36.1 -33.0 285 24 13 8.2 4.5
30000 -30.7 -23.3 285 17 9 8.2 4.5 | -31.1 -24.0 285 22 11 8.2 4.5
29000 -28.2 -18.8 285 16 8 8.2 4.5 | -28.7 -19.7 280 21 11 8.2 4.5
28000 -25.8 -14.4 290 15 8 7.9 4.3 | -26.2 -15.2 280 19 10 8.1 4.4
27000 -23.4 -10.1 290 14 7 7.9 4.3 | -23.2 -9.8 285 17 9 8.0 4.4
26000 -21.1 -6.0 295 14 7 7.9 4.3 | -20.8 -5.4 290 15 8 8.0 4.4
25000 -18.7 -1.7 300 13 7 7.9 4.3 | -18.4 -1.1 295 13 7 7.8 4.3
24000 -16.3 2.7 305 12 6 7.9 4.3 | -16.2 2.8 300 12 6 7.7 4.2
23000 -13.9 7.0 310 11 6 7.9 4.3 | -13.9 7.0 310 11 6 7.8 4.3
22000 -11.6 11.1 315 11 6 6.5 3.6 | -11.6 11.1 320 11 6 6.3 3.5
21000 -10.1 13.8 310 11 6 5.1 2.8 | -9.9 14.2 325 11 6 5.7 3.1
20000 -8.6 16.5 305 12 6 5.1 2.8 | -8.2 17.2 325 10 5 5.7 3.1
19500 -7.9 17.8 300 12 6 5.1 2.8 | -7.4 18.7 325 10 5 5.7 3.1
19000 -7.1 19.2 300 12 6 5.3 2.9 | -6.6 20.1 325 10 5 5.6 3.1
18500 -6.4 20.5 300 12 6 5.5 3.0 | -5.8 21.6 325 10 5 5.8 3.2
18000 -5.7 21.7 305 12 6 7.4 4.1 | -5.0 23.0 325 10 5 7.5 4.1
17500 -4.4 24.1 310 13 7 8.7 4.8 | -3.8 25.2 325 10 5 8.0 4.4
17000 -3.1 26.4 315 14 7 8.9 4.9 | -2.7 27.1 330 9 5 8.3 4.6
16500 -1.8 28.8 320 15 8 9.3 5.1 | -1.4 29.5 330 10 5 9.5 5.2
16000 0.2 32.4 325 16 8 9.3 5.1 | 0.0 32.0 330 10 5 9.5 5.2
15500 1.6 34.9 325 16 8 9.6 5.3 | 1.4 34.5 330 11 6 9.4 5.1
15000 3.1 37.6 325 16 8 9.6 5.3 | 2.8 37.0 330 11 6 9.4 5.1
14500 4.5 40.1 325 16 8 9.7 5.3 | 4.2 39.6 325 11 6 9.4 5.1
14000 6.0 42.8 325 16 8 9.7 5.3 | 6.3 43.3 325 11 6 9.3 5.1
13500 7.4 45.3 330 16 8 9.6 5.3 | 7.7 45.9 325 11 6 9.6 5.3
13000 8.8 47.8 330 16 8 9.6 5.3 | 9.1 48.4 325 11 6 9.6 5.3
12500 10.3 50.5 330 16 8 9.6 5.3 | 10.5 50.9 320 11 6 9.7 5.3
12000 11.7 53.1 330 16 8 9.6 5.3 | 12.0 53.6 320 11 6 9.7 5.3
11500 13.1 55.6 330 15 8 9.6 5.2 | 13.4 56.1 315 11 6 9.5 5.2
11000 14.6 58.3 325 15 8 9.2 5.0 | 14.8 58.6 315 11 5 9.1 5.0
10500 16.0 60.8 325 15 8 3.8 2.1 | 16.2 61.2 315 10 5 4.9 2.7
10250 16.1 61.0 325 15 7 4.9 2.7 | 16.4 61.5 315 10 5 6.4 3.5
10000 16.9 62.4 320 14 7 13.0 7.1 | 17.2 63.0 310 10 5 13.1 7.2
9750 17.8 64.0 320 14 7 11.5 6.3 | 18.1 64.6 310 10 5 11.9 6.5
9500 18.6 65.5 320 14 7 9.2 5.0 | 19.0 66.2 310 10 5 10.0 5.5
9250 19.1 66.4 320 13 7 6.9 3.8 | 19.6 67.3 310 10 5 8.6 4.7
9000 19.7 67.5 315 13 7 9.7 5.3 | 20.3 68.5 310 10 5 10.7 5.9
8750 20.5 68.9 315 13 7 10.6 5.8 | 21.1 70.0 310 10 5 10.9 6.0
8500 21.3 70.3 315 13 7 9.4 5.2 | 21.9 71.4 310 10 5 10.1 5.5
8250 21.9 71.4 310 13 7 8.6 4.7 | 22.6 72.7 310 10 5 9.2 5.0
8000 22.6 72.7 310 13 7 8.6 4.7 | 23.3 73.9 310 10 5 9.9 5.4
7750 23.2 73.8 310 13 7 8.2 4.5 | 24.1 75.4 305 10 5 10.3 5.7
7500 23.8 74.8 305 13 7 8.0 4.4 | 24.9 76.8 305 10 5 10.1 5.6
7250 24.4 75.9 305 13 7 7.5 4.1 | 25.6 78.1 305 10 5 10.1 5.6
7000 24.9 76.8 305 14 7 8.3 4.5 | 26.4 79.5 305 10 5 10.1 5.5
6750 25.5 77.9 305 14 7 6.2 3.4 | 27.1 80.8 305 9 5 10.3 5.6
6500 25.7 78.3 300 14 7 0.1 0.1 | 27.9 82.2 305 9 5 10.6 5.8
6250 25.7 78.3 295 12 6 0.8 0.4 | 28.7 83.7 305 9 5 11.2 6.1
6000 25.6 78.1 290 11 6 -7.4 -4.1 | 29.5 85.1 305 9 5 9.4 5.2
5750 24.7 76.5 275 8 4 -4.5 -2.5 | 30.3 86.5 305 9 5 15.0 8.2
5500 25.5 77.9 260 6 3 27.7 15.2 | 32.0 89.6 305 9 4 29.7 16.3
08/13/2025 at 1500 MDT | 08/13/2025 at 1800 MDT
|
CAPE... +3.1 LI... +0.6 | CAPE... +61.0 LI... -0.1
CINH... -9.4 K Index... +20.1 | CINH... -41.8 K Index... +22.6
|
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 -63.0 -81.4 250 11 6 -0.3 -0.2 | -63.2 -81.8 265 14 7 -0.9 -0.5
45000 -61.7 -79.1 265 17 9 3.7 2.0 | -62.4 -80.3 275 22 11 4.0 2.2
40000 -55.1 -67.2 290 26 14 7.8 4.3 | -55.3 -67.5 285 31 16 8.0 4.4
38000 -50.4 -58.7 290 28 14 7.8 4.3 | -50.5 -58.9 285 33 17 8.0 4.4
36000 -45.8 -50.4 285 30 15 7.8 4.3 | -45.7 -50.3 285 35 18 8.0 4.4
34000 -40.9 -41.6 280 28 15 8.1 4.5 | -40.9 -41.6 285 34 18 8.0 4.4
32000 -36.1 -33.0 275 27 14 8.1 4.4 | -36.1 -33.0 290 32 17 7.9 4.4
30000 -31.2 -24.2 280 25 13 8.1 4.5 | -31.2 -24.2 290 28 15 8.2 4.5
29000 -28.7 -19.7 285 24 12 8.1 4.5 | -28.8 -19.8 290 26 13 8.2 4.5
28000 -25.7 -14.3 290 22 11 7.9 4.3 | -25.8 -14.4 285 24 12 7.5 4.1
27000 -23.4 -10.1 285 20 10 7.9 4.3 | -23.5 -10.3 285 22 12 7.6 4.2
26000 -21.0 -5.8 285 18 9 7.9 4.3 | -21.2 -6.2 280 22 11 7.6 4.2
25000 -18.6 -1.5 280 16 8 7.7 4.2 | -19.0 -2.2 275 21 11 7.0 3.9
24000 -16.4 2.5 280 15 8 7.7 4.2 | -17.0 1.4 280 19 10 6.7 3.7
23000 -14.1 6.6 280 14 7 7.7 4.2 | -15.1 4.8 285 18 9 6.8 3.7
22000 -11.9 10.6 285 13 7 6.7 3.7 | -13.1 8.4 290 16 8 7.9 4.3
21000 -10.1 13.8 300 14 7 6.4 3.5 | -10.7 12.7 295 18 9 8.3 4.6
20000 -8.2 17.2 315 16 8 6.4 3.5 | -8.3 17.1 305 19 10 8.5 4.6
19500 -7.3 18.9 320 17 9 6.9 3.8 | -7.1 19.2 305 20 10 8.7 4.8
19000 -6.0 21.2 320 18 9 9.6 5.3 | -5.8 21.6 305 19 10 9.4 5.2
18500 -4.7 23.5 320 18 10 9.5 5.2 | -4.4 24.1 310 18 9 9.4 5.2
18000 -3.4 25.9 325 19 10 8.4 4.6 | -3.0 26.6 310 17 9 8.8 4.8
17500 -2.2 28.0 320 18 9 8.0 4.4 | -1.8 28.8 310 17 9 8.6 4.7
17000 -1.1 30.0 320 17 9 8.1 4.5 | -0.5 31.1 310 16 8 8.7 4.8
16500 0.1 32.2 320 16 8 8.8 4.9 | 0.8 33.4 310 15 8 9.2 5.0
16000 1.4 34.5 320 16 8 8.8 4.8 | 2.2 36.0 310 13 7 9.1 5.0
15500 2.8 37.0 315 15 8 9.0 5.0 | 3.6 38.5 315 12 6 9.3 5.1
15000 4.1 39.4 320 13 7 9.1 5.0 | 5.0 41.0 315 10 5 9.3 5.1
14500 6.2 43.2 320 12 6 9.2 5.0 | 6.3 43.3 320 9 5 9.2 5.0
14000 7.5 45.5 320 11 6 9.2 5.0 | 8.3 46.9 320 7 3 9.0 4.9
13500 8.9 48.0 320 10 5 9.0 4.9 | 9.7 49.5 320 5 3 9.0 4.9
13000 10.3 50.5 315 8 4 9.0 4.9 | 11.0 51.8 320 4 2 9.0 4.9
12500 11.6 52.9 315 7 4 9.0 4.9 | 12.3 54.1 315 2 1 9.1 5.0
12000 12.9 55.2 315 7 3 9.0 4.9 | 13.7 56.7 310 2 1 9.1 5.0
11500 14.3 57.7 310 6 3 9.2 5.0 | 15.1 59.2 290 1 1 8.9 4.9
11000 15.7 60.3 310 5 3 9.1 5.0 | 16.4 61.5 260 1 1 8.5 4.6
10500 17.0 62.6 305 4 2 5.5 3.0 | 17.7 63.9 235 1 1 4.6 2.6
10250 17.3 63.1 305 4 2 6.6 3.6 | 17.9 64.2 235 1 1 5.9 3.2
10000 18.1 64.6 305 4 2 12.1 6.7 | 18.7 65.7 230 2 1 11.8 6.5
9750 19.0 66.2 300 4 2 11.0 6.0 | 19.5 67.1 230 2 1 10.6 5.8
9500 19.8 67.6 300 4 2 9.9 5.4 | 20.3 68.5 230 2 1 9.4 5.2
9250 20.4 68.7 300 4 2 9.2 5.1 | 20.9 69.6 230 2 1 8.9 4.9
9000 21.2 70.2 300 4 2 10.7 5.9 | 21.7 71.1 230 2 1 10.6 5.8
8750 22.0 71.6 300 4 2 10.9 6.0 | 22.5 72.5 235 3 1 10.7 5.9
8500 22.8 73.0 295 4 2 10.3 5.7 | 23.3 73.9 235 3 1 10.1 5.6
8250 23.5 74.3 295 4 2 9.8 5.4 | 24.0 75.2 235 3 1 9.4 5.1
8000 24.3 75.7 295 4 2 9.6 5.3 | 24.7 76.5 235 3 2 9.8 5.4
7750 25.0 77.0 295 4 2 9.1 5.0 | 25.4 77.7 240 3 2 10.1 5.5
7500 25.7 78.3 290 4 2 10.1 5.5 | 26.2 79.2 240 3 2 10.0 5.5
7250 26.5 79.7 290 4 2 11.0 6.0 | 26.9 80.4 240 3 2 10.0 5.5
7000 27.3 81.1 290 4 2 10.3 5.7 | 27.7 81.9 240 3 2 10.0 5.5
6750 28.0 82.4 290 4 2 9.8 5.4 | 28.4 83.1 240 3 2 10.1 5.5
6500 28.8 83.8 290 4 2 10.5 5.8 | 29.2 84.6 240 3 2 10.3 5.7
6250 29.6 85.3 285 4 2 11.7 6.4 | 30.0 86.0 240 3 2 10.6 5.8
6000 30.4 86.7 285 4 2 9.6 5.3 | 30.7 87.3 245 4 2 9.9 5.5
5750 31.2 88.2 285 4 2 13.6 7.5 | 31.5 88.7 245 4 2 11.6 6.4
5500 32.7 90.9 285 4 2 28.0 15.4 | 32.5 90.5 245 4 2 17.4 9.5
________________________________________________________________________________
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.
042613