Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
542
UXUS97 KBOU 091345
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0744 MDT Thursday, October 9, 2025
This forecast is for Thursday, October 9, 2025:
If the trigger temperature of 77.2 F/25.1 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1068 ft/min (5.4 m/s)
Maximum height of thermals.................. 16689 ft MSL (11358 ft AGL)
Forecast maximum temperature................... 83.0 F/28.8 C
Time of trigger temperature.................... 1145 MDT
Time of overdevelopment........................ None
Middle/high clouds during soaring window....... None
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 10336 ft MSL (5006 ft AGL)
Thermal soaring outlook for Friday 10/10....... Fair
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1800 MDT)......... Trending the same
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1800 MDT)................ Weak PVA
Potential height of wave....................... 14455 ft MSL (9124 ft AGL)
Wave soaring outlook for Friday 10/10.......... Fair
Remarks...
Sunrise/Sunset.................... 07:04:14 / 18:28:56 MDT
Total possible sunshine........... 11 hr 24 min 42 sec (684 min 42 sec)
Altitude of sun at 12:46:35 MDT... 43.55 degrees
Upper air data from numerical model forecast valid on 10/09/2025 at 0600 MDT
Freezing level.................. 14293 ft MSL (8962 ft AGL)
Convective condensation level... 18615 ft MSL (13284 ft AGL)
Lifted condensation level....... 18072 ft MSL (12742 ft AGL)
Lifted index.................... +2.2
K index......................... +8.9
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 -66.2 -87.2 265 51 26 3.6 2.0 M M M M M
45000 -59.4 -74.9 265 74 38 6.9 3.8 M M M M M
40000 -49.2 -56.6 265 92 47 3.8 2.1 M M M M M
38000 -46.5 -51.7 265 80 41 4.1 2.2 M M M M M
36000 -44.0 -47.2 265 69 36 4.0 2.2 M M M M M
34000 -41.1 -42.0 265 58 30 5.1 2.8 M M M M M
32000 -38.0 -36.4 260 46 24 5.1 2.8 M M M M M
30000 -34.0 -29.2 260 38 20 7.3 4.0 41.8 107.2 10.2 M M
29000 -31.8 -25.2 260 35 18 7.3 4.0 40.8 105.5 9.6 M M
28000 -29.6 -21.3 260 32 17 7.5 4.1 40.0 104.1 9.1 M M
27000 -27.2 -17.0 255 30 15 8.0 4.4 39.2 102.6 8.6 M M
26000 -24.8 -12.6 255 27 14 8.0 4.4 38.5 101.4 8.1 M M
25000 -22.4 -8.3 250 25 13 8.1 4.5 38.0 100.4 7.8 M M
24000 -20.2 -4.4 245 23 12 7.1 3.9 37.1 98.7 7.1 M M
23000 -18.1 -0.6 245 21 11 7.1 3.9 36.0 96.9 6.3 M M
22000 -16.0 3.2 245 20 10 7.1 3.9 35.2 95.3 5.7 M M
21000 -14.2 6.4 250 18 9 5.5 3.0 33.7 92.7 4.5 M M
20000 -12.1 10.2 265 16 8 5.6 3.1 31.9 89.3 3.0 M M
19500 -11.3 11.7 270 15 8 5.7 3.1 31.2 88.1 2.4 M M
19000 -10.4 13.3 280 15 8 6.6 3.6 30.6 87.0 1.9 M M
18500 -9.4 15.1 285 16 8 6.6 3.6 30.0 86.0 1.4 M M
18000 -8.4 16.9 290 17 9 7.2 3.9 29.5 85.1 0.9 M M
17500 -7.3 18.9 295 18 9 7.4 4.0 29.1 84.4 0.5 M M
17000 -6.2 20.8 295 19 10 7.5 4.1 28.7 83.7 0.2 M M
16500 -5.1 22.8 300 20 10 7.7 4.2 28.3 83.0 -0.2 1042 5.3
16000 -4.0 24.8 300 22 11 7.7 4.2 28.0 82.4 -0.5 993 5.0
15500 -2.8 27.0 300 23 12 8.2 4.5 27.7 81.9 -0.8 943 4.8
15000 -1.6 29.1 300 24 12 8.2 4.5 27.4 81.4 -1.1 893 4.5
14500 -0.4 31.3 295 25 13 8.4 4.6 27.2 81.0 -1.4 842 4.3
14000 0.8 33.4 295 25 13 8.5 4.7 27.0 80.6 -1.6 790 4.0
13500 2.1 35.8 295 26 13 8.7 4.8 26.8 80.2 -1.8 738 3.7
13000 3.4 38.1 295 25 13 8.8 4.8 26.6 79.9 -2.0 684 3.5
12500 4.7 40.5 295 24 13 9.0 4.9 26.5 79.7 -2.2 631 3.2
12000 6.0 42.8 295 24 12 9.1 5.0 26.4 79.5 -2.3 576 2.9
11500 7.3 45.1 295 23 12 9.2 5.0 26.3 79.3 -2.4 520 2.6
11000 8.7 47.7 295 22 11 9.0 4.9 26.2 79.2 -2.6 464 2.4
10500 10.1 50.2 290 21 11 5.5 3.0 26.1 79.1 -2.7 408 2.1
10250 10.3 50.5 290 20 11 5.1 2.8 25.6 78.1 -3.1 394 2.0
10000 11.0 51.8 290 20 10 11.5 6.3 25.6 78.1 -3.2 366 1.9
9750 11.9 53.4 290 20 10 12.7 7.0 25.8 78.4 -3.0 332 1.7
9500 12.8 55.0 290 19 10 9.5 5.2 25.9 78.7 -2.9 298 1.5
9250 13.3 55.9 290 19 10 5.5 3.0 25.7 78.3 -3.1 275 1.4
9000 13.8 56.8 290 18 9 9.1 5.0 25.5 77.9 -3.4 252 1.3
8750 14.6 58.3 290 18 9 11.9 6.5 25.6 78.1 -3.3 220 1.1
8500 15.5 59.9 290 17 9 9.1 5.0 25.7 78.2 -3.2 189 1.0
8250 16.0 60.8 290 16 8 7.0 3.8 25.5 77.9 -3.4 164 0.8
8000 16.6 61.9 290 15 8 8.7 4.8 25.3 77.6 -3.6 140 0.7
7750 17.3 63.1 285 15 8 10.1 5.5 25.3 77.6 -3.6 111 0.6
7500 18.0 64.4 285 14 7 8.1 4.4 25.3 77.6 -3.6 82 0.4
7250 18.5 65.3 285 13 6 6.2 3.4 25.1 77.1 -3.8 60 0.3
7000 19.0 66.2 285 11 6 8.3 4.5 24.9 76.8 -4.1 37 0.2
6750 19.6 67.3 280 11 5 4.4 2.4 24.7 76.5 -4.2 12 0.1
6500 19.6 67.3 275 10 5 -2.4 -1.3 24.0 75.2 -5.0 5 0.0
6250 19.4 66.9 265 9 5 -2.2 -1.2 23.0 73.5 -5.9 4 0.0
6000 19.2 66.6 260 8 4 -4.3 -2.4 22.1 71.8 -6.9 3 0.0
5750 18.2 64.8 250 8 4 -27.3 -15.0 20.4 68.7 -8.6 25 0.1
5500 14.8 58.6 230 6 3 -58.3 -32.0 16.3 61.3 -12.8 119 0.6
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
10/09/2025 at 0900 MDT | 10/09/2025 at 1200 MDT
|
CAPE... 0.0 LI... +1.2 | CAPE... +3.5 LI... +0.5
CINH... -0.1 K Index... +13.1 | CINH... -14.6 K Index... +15.9
|
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 -66.5 -87.7 265 52 27 3.9 2.1 | -66.4 -87.5 265 50 25 4.1 2.2
45000 -59.4 -74.9 265 76 39 7.0 3.8 | -59.4 -74.9 265 73 38 6.4 3.5
40000 -48.8 -55.8 265 90 46 4.1 2.2 | -49.6 -57.3 265 89 46 4.3 2.4
38000 -46.5 -51.7 265 82 42 4.0 2.2 | -47.0 -52.6 265 80 41 4.3 2.3
36000 -44.1 -47.4 265 74 38 3.9 2.2 | -44.4 -47.9 265 71 37 4.3 2.3
34000 -41.4 -42.5 265 63 32 4.7 2.6 | -41.2 -42.2 265 64 33 5.7 3.1
32000 -38.6 -37.5 260 51 26 4.8 2.6 | -37.8 -36.0 265 58 30 5.7 3.1
30000 -33.7 -28.7 260 42 22 8.0 4.4 | -33.4 -28.1 265 49 25 6.9 3.8
29000 -31.4 -24.5 260 39 20 8.0 4.4 | -31.3 -24.3 265 44 23 6.9 3.8
28000 -29.0 -20.2 260 36 18 7.8 4.3 | -29.3 -20.7 265 40 21 7.4 4.0
27000 -26.6 -15.9 260 33 17 7.8 4.3 | -27.0 -16.6 265 37 19 7.6 4.2
26000 -24.3 -11.7 260 30 16 7.8 4.3 | -24.7 -12.5 265 34 17 7.6 4.2
25000 -22.0 -7.6 255 28 14 7.7 4.2 | -22.4 -8.3 265 31 16 7.5 4.1
24000 -20.2 -4.4 255 26 13 5.8 3.2 | -20.5 -4.9 265 29 15 6.3 3.5
23000 -18.4 -1.1 250 24 12 5.9 3.2 | -18.6 -1.5 270 28 14 6.4 3.5
22000 -16.7 1.9 250 22 11 5.9 3.2 | -16.7 1.9 270 26 14 6.4 3.5
21000 -15.0 5.0 250 20 10 5.8 3.2 | -14.9 5.2 270 24 13 6.3 3.5
20000 -13.2 8.2 255 17 9 5.8 3.2 | -13.1 8.4 265 22 12 6.3 3.5
19500 -12.4 9.7 255 16 8 5.8 3.2 | -12.1 10.2 265 21 11 6.4 3.5
19000 -11.5 11.3 260 15 8 7.1 3.9 | -11.2 11.8 265 20 10 6.4 3.5
18500 -10.4 13.3 270 14 7 7.0 3.8 | -10.3 13.5 265 19 10 6.4 3.5
18000 -9.4 15.1 275 13 7 7.1 3.9 | -9.3 15.3 265 18 9 6.8 3.7
17500 -8.3 17.1 285 12 6 7.3 4.0 | -8.2 17.2 270 16 8 7.2 4.0
17000 -7.3 18.9 295 13 7 7.2 3.9 | -7.2 19.0 275 15 8 7.2 4.0
16500 -5.5 22.1 300 14 7 8.4 4.6 | -6.0 21.2 275 14 7 8.1 4.4
16000 -4.2 24.4 305 15 7 8.4 4.6 | -4.3 24.3 285 12 6 8.1 4.4
15500 -3.0 26.6 305 15 8 8.6 4.7 | -3.0 26.6 290 11 6 8.7 4.8
15000 -1.7 28.9 310 16 8 8.6 4.7 | -1.8 28.8 290 10 5 8.6 4.7
14500 -0.5 31.1 310 16 8 8.8 4.8 | -0.5 31.1 295 9 5 9.1 5.0
14000 0.8 33.4 310 16 8 8.8 4.8 | 0.9 33.6 295 9 4 9.1 5.0
13500 2.1 35.8 310 16 8 9.2 5.0 | 2.2 36.0 295 8 4 9.2 5.1
13000 3.5 38.3 310 16 8 9.3 5.1 | 3.6 38.5 295 8 4 9.3 5.1
12500 4.8 40.6 310 16 8 9.2 5.0 | 5.0 41.0 295 8 4 9.4 5.2
12000 6.2 43.2 310 16 8 9.1 5.0 | 6.3 43.3 295 8 4 9.4 5.2
11500 7.5 45.5 305 15 8 9.0 5.0 | 7.7 45.9 295 7 4 9.2 5.1
11000 8.8 47.8 305 15 8 8.9 4.9 | 9.1 48.4 295 7 4 9.1 5.0
10500 10.1 50.2 305 15 8 4.4 2.4 | 10.3 50.5 295 7 4 4.2 2.3
10250 10.3 50.5 305 14 7 5.7 3.1 | 10.5 50.9 290 7 4 6.3 3.5
10000 11.1 52.0 305 14 7 12.5 6.9 | 11.4 52.5 290 7 3 13.1 7.2
9750 12.0 53.6 300 14 7 12.1 6.7 | 12.3 54.1 290 6 3 11.8 6.5
9500 12.8 55.0 300 13 7 8.3 4.6 | 13.0 55.4 290 6 3 8.5 4.7
9250 13.2 55.8 300 13 7 5.2 2.8 | 13.5 56.3 290 6 3 6.3 3.5
9000 13.7 56.7 300 12 6 9.9 5.5 | 14.1 57.4 290 6 3 10.6 5.8
8750 14.6 58.3 300 12 6 11.9 6.5 | 15.0 59.0 290 5 3 11.7 6.4
8500 15.4 59.7 295 12 6 8.1 4.5 | 15.7 60.3 290 5 2 8.4 4.6
8250 15.9 60.6 295 11 5 6.3 3.4 | 16.3 61.3 290 5 2 6.5 3.6
8000 16.4 61.5 295 10 5 8.9 4.9 | 16.8 62.2 285 4 2 10.2 5.6
7750 17.2 63.0 295 9 5 9.5 5.2 | 17.7 63.9 285 4 2 11.1 6.1
7500 17.7 63.9 290 9 4 6.5 3.5 | 18.4 65.1 280 3 2 7.4 4.1
7250 18.2 64.8 285 8 4 5.3 2.9 | 18.9 66.0 275 3 2 5.8 3.2
7000 18.6 65.5 280 7 3 7.7 4.2 | 19.4 66.9 265 3 1 10.8 5.9
6750 19.2 66.6 275 7 4 4.6 2.5 | 20.4 68.7 255 2 1 12.0 6.6
6500 19.2 66.6 265 6 3 -0.3 -0.2 | 21.0 69.8 245 2 1 7.9 4.3
6250 19.3 66.7 255 6 3 2.1 1.2 | 21.7 71.1 235 2 1 9.2 5.1
6000 19.4 66.9 245 6 3 -2.8 -1.5 | 22.4 72.3 220 2 1 7.9 4.3
5750 18.7 65.7 230 6 3 -12.3 -6.7 | 23.0 73.4 215 2 1 11.8 6.5
5500 17.6 63.7 220 6 3 -14.4 -7.9 | 24.2 75.6 215 2 1 21.1 11.6
10/09/2025 at 1500 MDT | 10/09/2025 at 1800 MDT
|
CAPE... +4.1 LI... +0.3 | CAPE... +4.3 LI... +0.2
CINH... -13.7 K Index... +19.4 | CINH... -31.3 K Index... +21.9
|
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 -66.9 -88.4 270 55 28 3.9 2.1 | -66.9 -88.4 270 58 30 3.7 2.0
45000 -59.9 -75.8 270 80 41 6.7 3.7 | -60.1 -76.2 275 80 41 6.5 3.6
40000 -49.9 -57.8 265 91 47 4.3 2.4 | -50.2 -58.4 270 89 46 4.8 2.6
38000 -47.3 -53.1 265 80 41 4.2 2.3 | -47.4 -53.3 270 82 42 4.7 2.6
36000 -44.8 -48.6 265 69 35 4.1 2.2 | -44.5 -48.1 270 76 39 4.6 2.5
34000 -40.9 -41.6 270 62 32 7.1 3.9 | -40.6 -41.1 270 67 34 6.9 3.8
32000 -36.6 -33.9 270 56 29 7.0 3.9 | -36.5 -33.7 275 58 30 6.8 3.7
30000 -32.4 -26.3 270 49 25 6.0 3.3 | -32.6 -26.7 275 50 26 6.5 3.6
29000 -30.6 -23.1 270 47 24 6.1 3.3 | -30.1 -22.2 280 46 24 6.5 3.6
28000 -28.8 -19.8 270 44 22 7.3 4.0 | -28.2 -18.8 280 43 22 6.9 3.8
27000 -26.5 -15.7 270 39 20 7.7 4.2 | -26.1 -15.0 275 37 19 7.0 3.8
26000 -24.2 -11.6 270 35 18 7.7 4.2 | -24.0 -11.2 275 32 17 7.1 3.9
25000 -21.9 -7.4 270 31 16 7.6 4.1 | -22.0 -7.6 270 27 14 7.0 3.9
24000 -19.9 -3.8 270 30 15 6.7 3.7 | -20.0 -4.0 265 24 12 6.7 3.6
23000 -17.9 -0.2 270 29 15 6.7 3.7 | -18.1 -0.6 260 21 11 6.7 3.7
22000 -15.9 3.4 270 28 15 6.4 3.5 | -16.1 3.0 255 19 10 6.6 3.6
21000 -14.3 6.3 270 26 14 5.6 3.1 | -14.3 6.3 250 18 9 6.3 3.5
20000 -12.7 9.1 265 24 12 5.6 3.1 | -12.4 9.7 245 17 9 6.3 3.5
19500 -11.9 10.6 265 23 12 5.5 3.0 | -11.5 11.3 245 17 9 6.3 3.5
19000 -11.0 12.2 265 22 11 7.6 4.2 | -10.6 12.9 245 16 8 6.4 3.5
18500 -9.9 14.2 260 21 11 7.4 4.1 | -9.7 14.5 240 16 8 6.4 3.5
18000 -8.8 16.2 260 19 10 7.2 4.0 | -8.7 16.3 240 16 8 6.7 3.7
17500 -7.8 18.0 255 18 9 7.1 3.9 | -7.7 18.1 235 15 8 6.9 3.8
17000 -6.8 19.8 255 16 8 7.0 3.9 | -6.7 19.9 230 13 7 6.9 3.8
16500 -5.7 21.7 250 15 7 7.9 4.3 | -5.6 21.9 225 12 6 7.9 4.3
16000 -3.9 25.0 245 12 6 8.0 4.4 | -4.5 23.9 220 10 5 7.7 4.2
15500 -2.6 27.3 245 11 6 9.1 5.0 | -2.6 27.3 210 9 5 9.0 4.9
15000 -1.3 29.7 245 10 5 9.0 5.0 | -1.3 29.7 210 8 4 8.9 4.9
14500 0.1 32.2 240 9 5 9.1 5.0 | 0.1 32.2 205 7 4 9.5 5.2
14000 1.5 34.7 240 8 4 9.1 5.0 | 1.5 34.7 200 7 3 9.4 5.2
13500 2.8 37.0 240 7 4 9.2 5.0 | 2.9 37.2 195 6 3 9.2 5.1
13000 4.2 39.6 240 6 3 9.2 5.0 | 4.3 39.7 190 5 3 9.2 5.1
12500 5.6 42.1 235 5 3 9.4 5.2 | 5.7 42.3 180 5 2 9.3 5.1
12000 7.0 44.6 235 4 2 9.5 5.2 | 7.1 44.8 175 4 2 9.3 5.1
11500 8.4 47.1 230 3 2 9.4 5.1 | 8.5 47.3 170 3 2 9.2 5.0
11000 9.8 49.6 220 2 1 9.1 5.0 | 9.9 49.8 160 3 1 9.1 5.0
10500 11.1 52.0 210 2 1 3.8 2.1 | 11.1 52.0 150 2 1 4.4 2.4
10250 11.3 52.3 205 2 1 6.6 3.6 | 11.4 52.5 140 2 1 6.8 3.8
10000 12.2 54.0 195 2 1 14.1 7.7 | 12.2 54.0 140 2 1 13.2 7.2
9750 13.2 55.8 185 1 1 12.1 6.7 | 13.1 55.6 140 2 1 11.5 6.3
9500 14.0 57.2 170 1 1 8.9 4.9 | 13.9 57.0 140 1 1 8.4 4.6
9250 14.5 58.1 165 1 1 6.5 3.6 | 14.4 57.9 130 1 1 6.4 3.5
9000 15.1 59.2 155 2 1 10.6 5.8 | 15.0 59.0 115 1 0 10.5 5.7
8750 16.0 60.8 140 1 1 11.7 6.4 | 15.8 60.4 000 0 0 11.5 6.3
8500 16.8 62.2 135 1 1 9.2 5.0 | 16.6 61.9 000 0 0 8.6 4.7
8250 17.4 63.3 135 2 1 7.3 4.0 | 17.2 63.0 295 1 0 7.1 3.9
8000 18.0 64.4 135 2 1 10.5 5.8 | 17.7 63.9 305 1 1 9.7 5.3
7750 18.8 65.8 125 2 1 11.8 6.5 | 18.5 65.3 295 1 1 10.4 5.7
7500 19.6 67.3 120 2 1 9.0 4.9 | 19.2 66.6 290 2 1 8.0 4.4
7250 20.2 68.4 125 2 1 7.2 4.0 | 19.7 67.5 290 3 1 6.8 3.7
7000 20.8 69.4 125 2 1 11.7 6.4 | 20.3 68.5 290 3 2 10.5 5.8
6750 21.9 71.4 110 2 1 12.9 7.1 | 21.2 70.2 290 3 2 10.7 5.9
6500 22.6 72.7 110 2 1 9.3 5.1 | 21.8 71.2 285 4 2 7.3 4.0
6250 23.4 74.1 110 2 1 10.4 5.7 | 22.3 72.1 285 5 2 8.1 4.5
6000 24.1 75.4 105 2 1 9.0 4.9 | 22.9 73.2 285 5 3 8.2 4.5
5750 24.8 76.6 115 2 1 12.5 6.9 | 23.5 74.3 285 6 3 5.4 2.9
5500 26.1 79.0 110 2 1 21.5 11.8 | 23.7 74.7 290 4 2 -0.2 -0.1
________________________________________________________________________________
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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