Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
643
UXUS97 KBOU 281214
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0613 MDT Friday, June 28, 2024
This forecast is for Friday, June 28, 2024:
If the trigger temperature of 82.8 F/28.2 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1309 ft/min (6.7 m/s)
Maximum height of thermals.................. 19268 ft MSL (13962 ft AGL)
Forecast maximum temperature................... 93.0 F/34.3 C
Time of trigger temperature.................... 1045 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................. 14035 ft MSL (8729 ft AGL)
Thermal soaring outlook for Saturday 06/29..... 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....................... 18823 ft MSL (13517 ft AGL)
Wave soaring outlook for Saturday 06/29........ Fair
Remarks... None
Sunrise/Sunset.................... 05:34:11 / 20:31:42 MDT
Total possible sunshine........... 14 hr 57 min 31 sec (897 min 31 sec)
Altitude of sun at 13:02:56 MDT... 73.44 degrees
Upper air data from numerical model forecast valid on 06/28/2024 at 0600 MDT
Freezing level.................. 15787 ft MSL (10481 ft AGL)
Convective condensation level... 16200 ft MSL (10894 ft AGL)
Lifted condensation level....... 17232 ft MSL (11926 ft AGL)
Lifted index.................... -3.0
K index......................... +24.2
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 -81.2 250 52 27 3.3 1.8 M M M M M
45000 -57.0 -70.6 245 70 36 5.6 3.1 M M M M M
40000 -48.1 -54.6 240 80 41 6.1 3.3 M M M M M
38000 -44.4 -47.9 245 76 39 6.1 3.3 M M M M M
36000 -40.8 -41.4 245 73 37 6.1 3.3 M M M M M
34000 -37.2 -35.0 245 64 33 5.9 3.2 M M M M M
32000 -33.7 -28.7 250 54 28 5.9 3.2 M M M M M
30000 -29.5 -21.1 250 48 25 6.5 3.6 46.2 115.2 9.4 M M
29000 -27.5 -17.5 255 47 24 6.5 3.6 45.0 113.0 8.6 M M
28000 -25.6 -14.1 255 45 23 6.8 3.7 43.9 111.0 7.8 M M
27000 -23.5 -10.3 250 41 21 7.2 4.0 42.8 109.0 7.0 M M
26000 -21.3 -6.3 250 37 19 7.3 4.0 41.8 107.3 6.3 M M
25000 -19.2 -2.6 250 34 17 7.4 4.0 41.0 105.8 5.6 M M
24000 -17.1 1.2 250 31 16 6.8 3.7 39.9 103.8 4.8 M M
23000 -15.1 4.8 250 28 14 6.8 3.8 38.8 101.9 3.9 M M
22000 -13.1 8.4 250 25 13 7.0 3.8 37.9 100.2 3.1 M M
21000 -11.3 11.7 255 22 11 6.2 3.4 36.6 97.9 2.0 M M
20000 -9.5 14.9 260 17 9 6.2 3.4 35.3 95.6 0.8 M M
19500 -8.6 16.5 265 15 8 6.2 3.4 34.7 94.5 0.3 M M
19000 -7.7 18.1 270 13 7 7.0 3.8 34.2 93.6 -0.2 1292 6.6
18500 -6.6 20.1 275 12 6 7.5 4.1 33.8 92.8 -0.6 1244 6.3
18000 -5.5 22.1 285 10 5 7.6 4.2 33.4 92.2 -0.9 1197 6.1
17500 -4.4 24.1 290 9 5 7.6 4.2 33.1 91.5 -1.3 1149 5.8
17000 -3.3 26.1 300 8 4 7.7 4.2 32.7 90.9 -1.7 1101 5.6
16500 -2.2 28.0 310 8 4 8.3 4.6 32.4 90.3 -2.0 1052 5.3
16000 -0.9 30.4 310 7 4 8.8 4.8 32.2 90.0 -2.2 999 5.1
15500 1.1 34.0 310 6 3 8.7 4.8 32.0 89.5 -2.4 919 4.7
15000 2.3 36.1 305 5 3 8.7 4.8 31.8 89.2 -2.7 866 4.4
14500 3.6 38.5 305 4 2 8.6 4.7 31.6 88.9 -2.8 813 4.1
14000 4.9 40.8 305 4 2 8.5 4.6 31.4 88.5 -3.1 760 3.9
13500 6.1 43.0 305 4 2 8.5 4.7 31.2 88.2 -3.3 707 3.6
13000 7.4 45.3 305 4 2 8.6 4.7 31.0 87.8 -3.5 655 3.3
12500 8.7 47.7 310 5 3 8.6 4.7 30.8 87.5 -3.7 602 3.1
12000 9.9 49.8 310 6 3 8.1 4.5 30.6 87.1 -3.9 550 2.8
11500 11.1 52.0 305 7 4 8.4 4.6 30.3 86.6 -4.2 499 2.5
11000 12.2 54.0 305 8 4 6.0 3.3 29.9 85.9 -4.6 453 2.3
10500 13.0 55.4 300 9 5 7.9 4.3 29.3 84.8 -5.2 412 2.1
10250 13.8 56.8 300 11 6 12.3 6.7 29.4 84.9 -5.2 383 1.9
10000 14.6 58.3 300 13 7 10.2 5.6 29.6 85.2 -5.1 349 1.8
9750 15.2 59.4 300 14 7 7.8 4.3 29.5 85.0 -5.2 324 1.6
9500 15.8 60.4 300 16 8 8.8 4.8 29.3 84.8 -5.4 298 1.5
9250 16.5 61.7 300 17 9 7.2 4.0 29.2 84.6 -5.5 272 1.4
9000 16.9 62.4 300 18 9 7.2 3.9 29.0 84.2 -5.7 250 1.3
8750 17.5 63.5 295 20 10 8.4 4.6 28.9 84.0 -5.9 225 1.1
8500 18.1 64.6 295 22 11 8.5 4.7 28.8 83.8 -6.1 200 1.0
8250 18.7 65.7 295 23 12 6.9 3.8 28.6 83.6 -6.2 175 0.9
8000 19.1 66.4 290 27 14 5.5 3.0 28.3 83.0 -6.5 156 0.8
7750 19.5 67.1 290 27 14 6.1 3.4 28.0 82.5 -6.9 136 0.7
7500 20.0 68.0 290 27 14 6.2 3.4 27.8 82.0 -7.2 115 0.6
7250 20.4 68.7 285 27 14 4.2 2.3 27.5 81.4 -7.5 96 0.5
7000 20.6 69.1 285 27 14 3.2 1.8 26.9 80.5 -8.1 82 0.4
6750 20.9 69.6 285 25 13 6.1 3.4 26.6 79.8 -8.5 65 0.3
6500 21.4 70.5 280 21 11 6.0 3.3 26.3 79.4 -8.8 43 0.2
6250 21.7 71.1 275 17 9 2.8 1.5 25.9 78.6 -9.2 27 0.1
6000 21.8 71.2 270 14 7 1.5 0.8 25.3 77.6 -9.8 16 0.1
5750 21.9 71.4 260 11 6 0.9 0.5 24.7 76.4 -10.5 6 0.0
5500 21.6 70.9 245 8 4 -9.8 -5.4 23.7 74.7 -11.5 7 0.0
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
06/28/2024 at 0900 MDT | 06/28/2024 at 1200 MDT
|
CAPE... +37.1 LI... -0.2 | CAPE... +240.7 LI... -1.1
CINH... -68.3 K Index... +23.5 | CINH... -28.0 K Index... +18.2
|
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 -63.7 -82.7 250 61 31 2.5 1.4 | -62.9 -81.2 245 65 34 2.9 1.6
45000 -58.2 -72.8 250 81 42 6.5 3.6 | -57.5 -71.5 250 86 44 5.5 3.0
40000 -48.1 -54.6 245 85 44 5.8 3.2 | -48.8 -55.8 250 91 47 5.0 2.8
38000 -44.7 -48.5 250 78 40 5.8 3.2 | -45.8 -50.4 250 79 41 5.0 2.7
36000 -41.2 -42.2 250 71 37 5.8 3.2 | -42.8 -45.0 255 68 35 5.0 2.7
34000 -37.8 -36.0 255 60 31 5.8 3.2 | -39.1 -38.4 255 62 32 6.4 3.5
32000 -34.3 -29.7 255 48 25 5.8 3.2 | -35.3 -31.5 260 57 30 6.5 3.5
30000 -29.9 -21.8 260 43 22 6.9 3.8 | -31.1 -24.0 260 52 27 7.2 3.9
29000 -27.9 -18.2 260 42 21 6.9 3.8 | -28.5 -19.3 265 48 24 7.2 3.9
28000 -25.8 -14.4 260 41 21 7.0 3.9 | -26.3 -15.3 265 44 23 7.2 3.9
27000 -23.7 -10.7 260 39 20 7.1 3.9 | -24.2 -11.6 265 42 21 7.2 3.9
26000 -21.6 -6.9 260 37 19 7.2 3.9 | -22.1 -7.8 265 39 20 7.2 3.9
25000 -19.5 -3.1 260 35 18 7.3 4.0 | -19.9 -3.8 265 36 18 7.3 4.0
24000 -17.6 0.3 260 34 17 6.4 3.5 | -18.0 -0.4 265 33 17 6.5 3.6
23000 -15.7 3.7 260 33 17 6.4 3.5 | -16.0 3.2 260 31 16 6.6 3.6
22000 -13.8 7.2 260 31 16 6.4 3.5 | -14.1 6.6 260 28 15 6.6 3.6
21000 -11.9 10.6 260 30 15 6.8 3.7 | -11.9 10.6 265 27 14 7.7 4.2
20000 -9.9 14.2 255 27 14 6.8 3.7 | -9.6 14.7 270 26 13 7.7 4.2
19500 -8.9 16.0 255 26 14 6.8 3.7 | -8.5 16.7 270 25 13 7.7 4.2
19000 -7.9 17.8 255 25 13 7.0 3.8 | -7.4 18.7 270 25 13 7.7 4.3
18500 -6.8 19.8 255 24 12 7.1 3.9 | -6.2 20.8 275 25 13 7.8 4.3
18000 -5.8 21.6 250 22 12 7.1 3.9 | -5.1 22.8 275 25 13 7.8 4.3
17500 -4.7 23.5 250 21 11 7.9 4.3 | -3.9 25.0 280 25 13 8.0 4.4
17000 -3.6 25.5 245 20 10 7.8 4.3 | -2.7 27.1 280 25 13 8.0 4.4
16500 -1.8 28.8 240 18 9 8.4 4.6 | -1.6 29.1 280 25 13 8.1 4.4
16000 -0.6 30.9 240 17 9 8.4 4.6 | -0.4 31.3 280 25 13 8.1 4.4
15500 0.7 33.3 240 16 8 8.2 4.5 | 1.4 34.5 280 25 13 8.3 4.5
15000 1.9 35.4 240 15 8 8.2 4.5 | 2.6 36.7 280 25 13 8.3 4.6
14500 3.1 37.6 240 14 7 8.2 4.5 | 3.8 38.8 280 25 13 8.2 4.5
14000 4.3 39.7 240 14 7 8.3 4.5 | 5.0 41.0 285 24 13 8.1 4.4
13500 5.5 41.9 240 13 7 8.3 4.6 | 6.2 43.2 285 24 12 8.2 4.5
13000 6.7 44.1 245 13 7 8.4 4.6 | 7.5 45.5 285 22 11 8.8 4.8
12500 8.0 46.4 245 13 7 8.4 4.6 | 8.8 47.8 285 20 10 8.8 4.8
12000 9.2 48.6 250 13 7 8.4 4.6 | 10.1 50.2 285 19 10 9.2 5.1
11500 10.4 50.7 260 13 7 8.6 4.7 | 11.4 52.5 285 19 10 9.4 5.2
11000 11.5 52.7 265 14 7 6.6 3.6 | 12.6 54.7 285 19 10 7.3 4.0
10500 12.5 54.5 270 15 7 8.2 4.5 | 13.7 56.7 285 18 9 10.3 5.6
10250 13.2 55.8 275 15 8 9.9 5.5 | 14.5 58.1 285 18 9 11.4 6.2
10000 13.9 57.0 275 16 8 7.8 4.3 | 15.2 59.4 285 17 9 8.1 4.4
9750 14.4 57.9 280 17 9 6.8 3.7 | 15.7 60.3 285 16 8 8.6 4.7
9500 14.9 58.8 280 17 9 7.3 4.0 | 16.3 61.3 280 16 8 8.6 4.7
9250 15.4 59.7 280 18 9 6.0 3.3 | 16.9 62.4 280 15 8 8.4 4.6
9000 15.8 60.4 285 19 10 6.3 3.4 | 17.5 63.5 280 15 8 9.4 5.1
8750 16.3 61.3 285 19 10 7.6 4.2 | 18.3 64.9 280 14 7 10.3 5.7
8500 16.9 62.4 285 18 9 7.6 4.2 | 19.0 66.2 280 14 7 10.1 5.6
8250 17.4 63.3 285 18 9 6.3 3.5 | 19.8 67.6 280 13 7 9.8 5.4
8000 17.8 64.0 285 19 10 6.8 3.7 | 20.5 68.9 285 14 7 9.8 5.4
7750 18.4 65.1 285 19 10 8.8 4.9 | 21.2 70.2 285 13 7 10.2 5.6
7500 19.0 66.2 285 18 9 8.3 4.6 | 22.0 71.6 285 13 7 10.0 5.5
7250 19.6 67.3 285 17 9 5.4 2.9 | 22.7 72.9 285 12 6 8.6 4.7
7000 19.9 67.8 285 17 9 4.4 2.4 | 23.3 73.9 285 13 7 8.9 4.9
6750 20.3 68.5 285 17 9 8.8 4.8 | 24.1 75.4 285 12 6 11.6 6.4
6500 21.0 69.8 280 16 8 8.4 4.6 | 25.0 77.0 285 12 6 12.0 6.6
6250 21.4 70.5 280 14 7 4.6 2.5 | 25.8 78.4 285 11 6 11.0 6.0
6000 21.7 71.1 285 13 7 4.0 2.2 | 26.6 79.9 285 11 6 11.4 6.2
5750 22.0 71.6 285 11 6 4.8 2.6 | 27.5 81.5 290 11 6 9.2 5.0
5500 22.4 72.3 280 9 5 10.4 5.7 | 28.2 82.8 285 10 5 15.6 8.5
06/28/2024 at 1500 MDT | 06/28/2024 at 1800 MDT
|
CAPE... +286.5 LI... -1.6 | CAPE... +428.4 LI... -2.1
CINH... -12.4 K Index... +28.8 | CINH... -15.2 K Index... +30.7
|
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 -62.7 -80.9 250 70 36 2.3 1.3 | -62.6 -80.7 255 69 35 1.6 0.9
45000 -58.0 -72.4 255 91 47 5.1 2.8 | -58.4 -73.1 255 87 45 5.1 2.8
40000 -49.9 -57.8 250 94 48 5.4 3.0 | -50.8 -59.4 255 85 44 5.2 2.9
38000 -46.7 -52.1 250 84 43 5.4 3.0 | -47.7 -53.9 260 72 37 5.2 2.9
36000 -43.4 -46.1 255 74 38 5.4 3.0 | -44.5 -48.1 265 60 31 5.1 2.8
34000 -39.7 -39.5 255 66 34 6.4 3.5 | -40.3 -40.5 270 53 27 7.5 4.1
32000 -35.8 -32.4 260 58 30 6.5 3.6 | -35.8 -32.4 270 47 24 7.5 4.1
30000 -31.1 -24.0 260 49 25 7.3 4.0 | -30.8 -23.4 270 43 22 7.5 4.1
29000 -29.0 -20.2 260 45 23 7.3 4.0 | -28.5 -19.3 270 41 21 7.5 4.1
28000 -26.8 -16.2 260 41 21 7.5 4.1 | -26.3 -15.3 265 40 20 7.7 4.2
27000 -24.5 -12.1 260 37 19 7.7 4.2 | -24.0 -11.2 265 37 19 7.8 4.3
26000 -22.2 -8.0 260 34 18 7.7 4.2 | -21.7 -7.1 260 35 18 7.8 4.3
25000 -19.9 -3.8 260 31 16 7.8 4.3 | -19.4 -2.9 260 33 17 7.9 4.3
24000 -17.8 -0.0 260 30 15 7.1 3.9 | -17.4 0.7 260 32 16 6.5 3.6
23000 -15.7 3.7 265 29 15 7.1 3.9 | -15.5 4.1 260 31 16 6.5 3.6
22000 -13.6 7.5 265 28 14 7.2 3.9 | -13.6 7.5 260 30 15 6.6 3.6
21000 -11.6 11.1 265 28 14 6.8 3.7 | -11.6 11.1 260 29 15 7.2 4.0
20000 -9.6 14.7 265 28 14 6.8 3.7 | -9.5 14.9 260 28 14 7.3 4.0
19500 -8.7 16.3 265 28 15 6.8 3.7 | -8.4 16.9 260 27 14 7.3 4.0
19000 -7.7 18.1 265 29 15 7.4 4.0 | -7.4 18.7 260 27 14 7.8 4.3
18500 -6.6 20.1 265 29 15 7.5 4.1 | -6.2 20.8 260 26 13 7.9 4.3
18000 -5.5 22.1 270 29 15 7.6 4.2 | -5.1 22.8 265 25 13 7.9 4.3
17500 -4.3 24.3 270 29 15 8.1 4.5 | -4.0 24.8 265 24 13 7.8 4.3
17000 -2.6 27.3 270 28 14 8.1 4.5 | -2.3 27.9 265 24 12 7.9 4.4
16500 -1.4 29.5 270 27 14 8.5 4.7 | -1.1 30.0 265 23 12 8.5 4.7
16000 -0.1 31.8 270 26 14 8.5 4.6 | 0.2 32.4 265 22 11 8.5 4.7
15500 1.1 34.0 270 26 13 9.1 5.0 | 1.4 34.5 265 21 11 8.7 4.8
15000 2.5 36.5 270 25 13 9.1 5.0 | 2.7 36.9 265 20 10 8.7 4.8
14500 3.8 38.8 270 24 12 9.1 5.0 | 4.0 39.2 265 19 10 8.9 4.9
14000 5.1 41.2 270 22 12 9.1 5.0 | 5.3 41.5 265 19 10 9.0 4.9
13500 6.5 43.7 270 21 11 9.2 5.0 | 6.6 43.9 270 18 9 9.1 5.0
13000 7.8 46.0 270 20 10 9.3 5.1 | 8.0 46.4 270 18 9 9.4 5.1
12500 9.2 48.6 275 19 10 9.3 5.1 | 9.4 48.9 270 18 9 9.4 5.1
12000 10.6 51.1 275 17 9 9.5 5.2 | 10.8 51.4 275 17 9 9.4 5.1
11500 12.0 53.6 280 16 8 9.6 5.3 | 12.2 54.0 280 16 8 9.4 5.2
11000 13.3 55.9 280 16 8 8.5 4.6 | 13.4 56.1 280 16 8 7.8 4.3
10500 14.6 58.3 280 16 8 11.6 6.4 | 14.5 58.1 285 16 8 12.2 6.7
10250 15.6 60.1 280 15 8 12.8 7.0 | 15.6 60.1 290 16 8 13.5 7.4
10000 16.4 61.5 280 15 8 9.3 5.1 | 16.4 61.5 290 16 8 8.6 4.7
9750 17.1 62.8 280 15 8 9.9 5.4 | 17.1 62.8 290 15 8 10.0 5.5
9500 17.8 64.0 285 15 8 9.8 5.4 | 17.8 64.0 290 15 8 9.5 5.2
9250 18.6 65.5 285 15 8 9.7 5.3 | 18.5 65.3 295 16 8 8.6 4.7
9000 19.3 66.7 285 15 8 9.9 5.5 | 19.1 66.4 295 16 8 9.5 5.2
8750 20.0 68.0 285 15 8 10.3 5.7 | 19.9 67.8 295 16 8 10.7 5.9
8500 20.8 69.4 285 15 7 10.3 5.6 | 20.7 69.3 295 15 8 10.5 5.7
8250 21.6 70.9 285 14 7 10.0 5.5 | 21.4 70.5 300 15 8 9.0 4.9
8000 22.3 72.1 285 14 7 9.6 5.3 | 22.0 71.6 300 16 8 9.1 5.0
7750 23.0 73.4 285 14 7 9.7 5.3 | 22.8 73.0 300 16 8 10.5 5.7
7500 23.7 74.7 285 14 7 9.7 5.3 | 23.6 74.5 300 15 8 9.9 5.4
7250 24.4 75.9 290 14 7 8.6 4.7 | 24.2 75.6 300 15 8 8.3 4.5
7000 25.1 77.2 290 14 7 9.0 4.9 | 24.8 76.6 305 16 8 8.6 4.7
6750 25.8 78.4 290 14 7 11.2 6.1 | 25.6 78.1 305 15 8 11.6 6.4
6500 26.7 80.1 290 13 7 11.4 6.3 | 26.5 79.7 305 14 7 11.4 6.3
6250 27.5 81.5 290 13 7 10.5 5.7 | 27.2 81.0 305 14 7 9.7 5.3
6000 28.2 82.8 290 13 7 10.6 5.8 | 28.0 82.4 310 15 7 9.6 5.3
5750 29.0 84.2 290 12 6 9.2 5.1 | 28.7 83.7 310 14 7 9.8 5.4
5500 29.7 85.5 290 12 6 12.7 7.0 | 29.5 85.1 305 12 6 13.2 7.3
________________________________________________________________________________
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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