Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
350
UXUS97 KBOU 261309
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0707 MDT Friday, July 26, 2024
This forecast is for Friday, July 26, 2024:
If the trigger temperature of 87.1 F/30.6 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 945 ft/min (4.8 m/s)
Maximum height of thermals.................. 13873 ft MSL (8574 ft AGL)
Forecast maximum temperature................... 92.0 F/33.8 C
Time of trigger temperature.................... 1130 MDT
Time of overdevelopment........................ 1400 MDT
Middle/high clouds during soaring window....... None
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 8549 ft MSL (3250 ft AGL)
Thermal soaring outlook for Saturday 07/27..... 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....................... 14401 ft MSL (9102 ft AGL)
Wave soaring outlook for Saturday 07/27........ Fair
Remarks...
Sunrise/Sunset.................... 05:53:52 / 20:18:12 MDT
Total possible sunshine........... 14 hr 24 min 19 sec (864 min 19 sec)
Altitude of sun at 13:06:02 MDT... 69.38 degrees
Upper air data from numerical model forecast valid on 07/26/2024 at 0600 MDT
Freezing level.................. 16776 ft MSL (11477 ft AGL)
Convective condensation level... 16267 ft MSL (10968 ft AGL)
Lifted condensation level....... 15981 ft MSL (10682 ft AGL)
Lifted index.................... -2.9
K index......................... +27.8
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 -81.2 335 9 5 0.9 0.5 M M M M M
45000 -58.3 -72.9 315 17 9 6.3 3.4 M M M M M
40000 -49.1 -56.4 320 24 12 5.4 3.7 M M M M M
38000 -45.9 -50.6 315 24 12 5.4 3.0 M M M M M
36000 -42.7 -44.9 310 24 12 6.7 3.7 M M M M M
34000 -37.8 -36.0 310 18 9 8.1 4.5 M M M M M
32000 -32.9 -27.2 305 12 6 8.8 4.8 M M M M M
30000 -27.7 -17.9 305 7 4 7.7 4.2 47.9 118.3 11.1 M M
29000 -25.4 -13.7 300 5 3 7.7 4.2 47.2 117.0 10.6 M M
28000 -23.3 -9.9 295 3 2 6.1 3.4 46.3 115.4 10.0 M M
27000 -21.4 -6.5 260 2 1 6.2 3.4 44.9 112.8 9.0 M M
26000 -19.6 -3.3 200 2 1 6.3 3.4 43.6 110.5 8.0 M M
25000 -17.7 0.1 180 4 2 7.0 3.9 42.4 108.4 7.2 M M
24000 -15.5 4.1 205 3 2 7.4 4.1 41.5 106.6 6.5 M M
23000 -13.3 8.1 240 3 2 7.4 4.1 40.6 105.1 5.8 M M
22000 -11.1 12.0 265 4 2 6.7 3.7 39.8 103.7 5.2 M M
21000 -9.2 15.4 235 3 2 6.4 3.5 38.5 101.4 4.2 M M
20000 -7.3 18.9 205 3 2 6.4 3.5 37.4 99.3 3.2 M M
19500 -6.3 20.7 190 4 2 6.5 3.6 36.9 98.4 2.8 M M
19000 -5.4 22.3 185 4 2 7.2 3.9 36.4 97.5 2.3 M M
18500 -4.4 24.1 185 5 2 7.2 4.0 35.9 96.6 1.8 M M
18000 -3.3 26.1 185 5 3 8.3 4.5 35.5 96.0 1.4 M M
17500 -2.1 28.2 185 5 3 8.6 4.7 35.3 95.6 1.2 M M
17000 -0.9 30.4 190 6 3 8.8 4.8 35.2 95.3 1.0 M M
16500 0.5 32.9 190 6 3 9.6 5.3 35.1 95.1 0.8 M M
16000 2.5 36.5 195 6 3 9.4 5.2 35.0 95.1 0.7 M M
15500 3.9 39.0 200 5 3 9.1 5.0 34.9 94.9 0.6 M M
15000 5.2 41.4 205 4 2 9.2 5.0 34.8 94.7 0.5 M M
14500 6.5 43.7 225 3 2 8.2 4.5 34.6 94.4 0.3 M M
14000 7.6 45.7 260 2 1 8.4 4.6 34.4 93.9 0.0 M M
13500 8.8 47.8 305 3 2 7.6 4.2 34.1 93.5 -0.3 699 3.6
13000 9.9 49.8 330 5 3 7.5 4.1 33.8 92.8 -0.7 652 3.3
12500 11.0 51.8 345 7 4 8.0 4.4 33.5 92.2 -1.0 604 3.1
12000 12.2 54.0 350 10 5 8.3 4.5 33.2 91.8 -1.3 553 2.8
11500 13.4 56.1 350 12 6 8.2 4.5 33.0 91.4 -1.5 502 2.5
11000 14.6 58.3 350 14 7 8.0 4.4 32.7 90.9 -1.8 451 2.3
10500 15.8 60.4 350 15 8 5.2 2.9 32.5 90.5 -2.0 401 2.0
10250 16.1 61.0 345 15 8 6.7 3.7 32.0 89.7 -2.5 385 2.0
10000 16.8 62.2 345 16 8 11.4 6.3 32.1 89.8 -2.5 355 1.8
9750 17.6 63.7 345 16 8 10.9 6.0 32.2 89.9 -2.4 325 1.6
9500 18.4 65.1 345 16 8 8.3 4.6 32.2 90.0 -2.4 295 1.5
9250 18.8 65.8 345 16 8 5.9 3.2 32.0 89.5 -2.7 274 1.4
9000 19.4 66.9 340 16 8 8.5 4.6 31.8 89.2 -2.9 250 1.3
8750 20.0 68.0 340 17 9 9.3 5.1 31.7 89.1 -3.0 222 1.1
8500 20.7 69.3 340 17 9 8.3 4.6 31.7 89.0 -3.0 195 1.0
8250 21.3 70.3 340 17 9 7.6 4.2 31.5 88.7 -3.2 170 0.9
8000 21.9 71.4 335 17 9 7.8 4.3 31.4 88.4 -3.3 145 0.7
7750 22.4 72.3 335 17 9 7.6 4.2 31.2 88.2 -3.5 121 0.6
7500 22.9 73.2 335 16 8 5.3 2.9 31.0 87.8 -3.7 98 0.5
7250 23.2 73.8 335 16 8 3.7 2.0 30.5 87.0 -4.2 82 0.4
7000 23.5 74.3 330 15 8 4.0 2.2 30.1 86.2 -4.6 66 0.3
6750 23.8 74.8 330 14 7 0.6 0.3 29.6 85.2 -5.1 51 0.3
6500 23.6 74.5 330 13 7 -3.2 -1.8 28.7 83.7 -6.0 48 0.2
6250 23.3 73.9 325 11 6 -4.8 -2.6 27.7 81.8 -7.1 51 0.3
6000 23.0 73.4 315 10 5 -1.4 -0.8 26.6 79.9 -8.1 53 0.3
5750 22.8 73.0 310 9 5 -4.8 -2.6 25.8 78.5 -9.0 50 0.3
5500 21.8 71.2 285 5 2 -20.1 -11.0 24.1 75.5 -10.8 73 0.4
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
07/26/2024 at 0900 MDT | 07/26/2024 at 1200 MDT
|
CAPE... +274.1 LI... -1.6 | CAPE... +577.0 LI... -1.5
CINH... -145.7 K Index... +28.0 | CINH... -18.1 K Index... +28.9
|
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 -63.2 -81.8 310 9 4 1.2 0.7 | -63.2 -81.8 290 10 5 1.3 0.7
45000 -58.3 -72.9 315 16 8 6.3 3.4 | -58.0 -72.4 300 20 10 6.6 3.6
40000 -49.2 -56.6 320 20 11 5.3 2.9 | -48.6 -55.5 305 23 12 5.0 2.7
38000 -46.0 -50.8 315 19 10 5.3 2.9 | -45.6 -50.1 305 17 9 5.0 2.7
36000 -42.8 -45.0 305 18 9 6.5 3.6 | -42.6 -44.7 305 11 6 6.1 3.4
34000 -38.0 -36.4 300 15 8 8.0 4.4 | -38.0 -36.4 290 11 6 7.7 4.2
32000 -33.2 -27.8 290 12 6 8.8 4.8 | -33.4 -28.1 275 12 6 8.4 4.6
30000 -27.9 -18.2 290 8 4 7.9 4.3 | -28.0 -18.4 265 8 4 8.0 4.4
29000 -25.6 -14.1 285 6 3 7.9 4.3 | -25.6 -14.1 255 6 3 8.0 4.4
28000 -23.4 -10.1 275 5 2 6.3 3.5 | -23.4 -10.1 240 5 3 6.2 3.4
27000 -21.5 -6.7 245 4 2 6.4 3.5 | -21.5 -6.7 225 6 3 6.3 3.5
26000 -19.6 -3.3 210 4 2 6.4 3.5 | -19.6 -3.3 215 7 4 6.3 3.5
25000 -17.6 0.3 190 6 3 7.0 3.9 | -17.7 0.1 210 9 4 7.2 3.9
24000 -15.5 4.1 200 5 2 7.3 4.0 | -15.4 4.3 205 7 4 7.6 4.2
23000 -13.3 8.1 205 3 2 7.3 4.0 | -13.2 8.2 205 6 3 7.6 4.2
22000 -11.2 11.8 220 2 1 7.1 3.9 | -10.9 12.4 200 5 2 7.3 4.0
21000 -8.9 16.0 210 4 2 7.1 3.9 | -8.7 16.3 215 5 2 7.3 4.0
20000 -6.7 19.9 200 5 2 7.2 3.9 | -6.5 20.3 225 5 3 7.3 4.0
19500 -5.6 21.9 200 5 3 7.1 3.9 | -5.4 22.3 230 5 3 7.1 3.9
19000 -4.7 23.5 205 6 3 6.6 3.6 | -4.4 24.1 235 6 3 6.4 3.5
18500 -3.7 25.3 205 7 3 6.7 3.7 | -3.5 25.7 240 6 3 6.5 3.6
18000 -2.8 27.0 210 7 4 7.2 4.0 | -2.6 27.3 240 7 3 6.9 3.8
17500 -1.7 28.9 205 7 4 7.5 4.1 | -1.6 29.1 235 7 3 7.2 3.9
17000 -0.7 30.7 200 8 4 7.9 4.3 | -0.6 30.9 230 7 4 7.4 4.1
16500 0.5 32.9 200 7 4 9.0 4.9 | 0.4 32.7 230 7 3 8.0 4.4
16000 1.7 35.1 195 6 3 9.0 4.9 | 1.6 34.9 230 6 3 8.0 4.4
15500 3.0 37.4 195 5 3 8.5 4.7 | 2.7 36.9 230 5 3 7.8 4.3
15000 4.8 40.6 195 3 2 8.7 4.7 | 4.2 39.6 250 3 2 8.0 4.4
14500 5.9 42.6 195 1 0 7.0 3.9 | 5.3 41.5 275 3 1 7.2 4.0
14000 6.9 44.4 020 2 1 7.2 3.9 | 6.3 43.3 320 3 1 7.3 4.0
13500 7.9 46.2 015 5 2 7.7 4.2 | 7.4 45.3 345 4 2 8.2 4.5
13000 8.9 48.0 015 8 4 7.7 4.2 | 8.6 47.5 345 4 2 8.3 4.6
12500 10.0 50.0 015 10 5 8.5 4.7 | 9.8 49.6 350 5 3 8.5 4.7
12000 11.3 52.3 005 11 6 8.9 4.9 | 11.2 52.2 355 6 3 8.6 4.7
11500 12.6 54.7 355 12 6 8.7 4.8 | 12.5 54.5 360 7 3 8.7 4.8
11000 14.0 57.2 350 12 6 8.2 4.5 | 13.7 56.7 005 7 4 8.6 4.7
10500 15.3 59.5 345 13 7 4.2 2.3 | 15.0 59.0 005 8 4 4.1 2.2
10250 15.4 59.7 345 13 7 6.2 3.4 | 15.2 59.4 005 8 4 6.2 3.4
10000 16.3 61.3 345 13 7 12.8 7.0 | 16.0 60.8 005 8 4 13.6 7.4
9750 17.1 62.8 340 13 7 11.8 6.5 | 16.9 62.4 005 8 4 12.4 6.8
9500 18.0 64.4 340 13 7 9.1 5.0 | 17.8 64.0 005 7 4 9.6 5.3
9250 18.5 65.3 340 13 7 6.6 3.6 | 18.4 65.1 005 7 4 7.6 4.2
9000 19.1 66.4 340 13 7 8.9 4.9 | 19.1 66.4 005 7 4 10.9 6.0
8750 19.8 67.6 340 13 7 9.4 5.2 | 19.9 67.8 005 7 4 11.3 6.2
8500 20.4 68.7 335 13 7 7.8 4.3 | 20.7 69.3 005 7 4 10.7 5.8
8250 21.0 69.8 335 12 6 6.6 3.6 | 21.5 70.7 005 7 4 10.4 5.7
8000 21.5 70.7 335 12 6 7.1 3.9 | 22.3 72.1 005 7 4 9.8 5.4
7750 22.0 71.6 335 11 6 7.2 3.9 | 23.0 73.4 005 7 4 9.2 5.0
7500 22.5 72.5 330 11 6 6.7 3.7 | 23.7 74.7 005 7 4 10.0 5.5
7250 23.0 73.4 330 11 6 6.3 3.5 | 24.5 76.1 005 7 4 10.3 5.7
7000 23.5 74.3 330 11 5 6.8 3.7 | 25.2 77.4 005 7 3 10.4 5.7
6750 23.9 75.0 325 10 5 6.0 3.3 | 26.0 78.8 005 7 3 10.9 6.0
6500 24.3 75.7 325 9 5 3.7 2.0 | 26.8 80.2 005 7 3 10.8 5.9
6250 24.5 76.1 320 8 4 4.1 2.3 | 27.6 81.7 005 6 3 11.5 6.3
6000 24.7 76.5 315 6 3 1.3 0.7 | 28.5 83.3 005 6 3 8.7 4.8
5750 24.8 76.6 300 3 2 7.5 4.1 | 29.2 84.6 005 6 3 14.5 8.0
5500 26.1 79.0 300 3 2 26.5 14.5 | 30.9 87.6 005 6 3 32.9 18.1
07/26/2024 at 1500 MDT | 07/26/2024 at 1800 MDT
|
CAPE... +564.1 LI... -2.9 | CAPE... +1.2 LI... +0.1
CINH... -3.8 K Index... +34.1 | CINH... -20.0 K Index... +30.0
|
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 -63.1 -81.6 285 12 6 0.9 0.5 | -61.8 -79.2 290 19 10 1.6 0.9
45000 -59.2 -74.6 290 23 12 5.2 2.8 | -58.5 -73.3 285 24 12 2.9 1.6
40000 -50.7 -59.3 280 32 17 8.1 4.5 | -52.6 -62.7 270 19 10 9.1 5.0
38000 -45.8 -50.4 275 28 15 8.1 4.5 | -47.1 -52.8 270 19 10 9.1 5.0
36000 -40.9 -41.6 270 24 13 7.8 4.3 | -41.7 -43.1 270 19 10 8.8 4.8
34000 -36.5 -33.7 270 19 10 7.4 4.1 | -36.1 -33.0 260 20 10 8.2 4.5
32000 -32.1 -25.8 275 14 7 8.2 4.5 | -31.2 -24.2 250 21 11 9.0 4.9
30000 -27.1 -16.8 260 9 5 7.4 4.1 | -26.5 -15.7 245 18 9 7.9 4.3
29000 -24.9 -12.8 250 8 4 7.4 4.1 | -24.2 -11.6 240 17 9 7.9 4.3
28000 -22.8 -9.0 235 7 4 6.2 3.4 | -21.9 -7.4 230 16 8 7.2 3.9
27000 -21.0 -5.8 225 7 4 6.3 3.5 | -19.8 -3.6 225 14 7 7.3 4.0
26000 -19.1 -2.4 215 8 4 6.3 3.5 | -17.6 0.3 215 12 6 7.3 4.0
25000 -17.2 1.0 205 9 5 6.5 3.6 | -15.5 4.1 205 10 5 7.0 3.9
24000 -15.1 4.8 200 8 4 6.8 3.7 | -13.6 7.5 195 10 5 6.6 3.6
23000 -13.0 8.6 190 7 4 6.9 3.8 | -11.7 10.9 180 9 5 6.6 3.6
22000 -10.9 12.4 180 7 3 6.5 3.6 | -9.8 14.4 165 9 5 6.3 3.5
21000 -9.1 15.6 180 5 3 6.4 3.5 | -8.1 17.4 160 9 5 5.8 3.2
20000 -7.2 19.0 175 4 2 6.5 3.6 | -6.4 20.5 155 9 4 5.9 3.2
19500 -6.3 20.7 175 3 2 6.6 3.6 | -5.2 22.6 150 9 4 5.7 3.1
19000 -5.4 22.3 175 3 2 6.7 3.7 | -4.4 24.1 150 8 4 5.5 3.0
18500 -4.5 23.9 180 4 2 6.9 3.8 | -3.6 25.5 150 8 4 5.5 3.0
18000 -3.6 25.5 185 4 2 7.3 4.0 | -2.8 27.0 150 8 4 5.1 2.8
17500 -2.5 27.5 185 4 2 7.5 4.1 | -2.1 28.2 155 7 4 5.1 2.8
17000 -1.5 29.3 185 4 2 7.6 4.2 | -1.4 29.5 155 7 3 5.0 2.8
16500 -0.4 31.3 175 3 2 7.8 4.3 | -0.7 30.7 160 6 3 5.0 2.7
16000 1.2 34.2 150 2 1 7.9 4.4 | 0.0 32.0 170 5 3 4.9 2.7
15500 2.4 36.3 110 2 1 8.3 4.5 | 0.8 33.4 185 5 3 6.1 3.4
15000 3.5 38.3 070 2 1 8.2 4.5 | 1.7 35.1 195 5 3 5.9 3.3
14500 4.7 40.5 055 2 1 9.4 5.2 | 2.7 36.9 210 5 3 7.5 4.1
14000 6.1 43.0 050 2 1 9.4 5.2 | 3.8 38.8 220 6 3 8.0 4.4
13500 7.4 45.3 040 2 1 9.4 5.1 | 5.0 41.0 225 6 3 8.0 4.4
13000 8.8 47.8 035 2 1 9.4 5.1 | 6.1 43.0 230 7 4 7.9 4.4
12500 10.2 50.4 030 2 1 9.5 5.2 | 7.3 45.1 235 8 4 8.0 4.4
12000 11.7 53.1 025 2 1 9.6 5.3 | 8.5 47.3 235 9 5 8.2 4.5
11500 13.1 55.6 015 2 1 9.7 5.3 | 9.7 49.5 235 10 5 8.1 4.5
11000 14.5 58.1 360 1 1 9.6 5.3 | 10.8 51.4 235 11 6 7.5 4.1
10500 16.0 60.8 345 1 1 6.8 3.7 | 11.9 53.4 235 13 6 6.2 3.4
10250 16.4 61.5 345 2 1 7.9 4.3 | 12.3 54.1 235 13 7 6.5 3.6
10000 17.3 63.1 335 2 1 12.3 6.7 | 12.9 55.2 235 13 7 8.4 4.6
9750 18.1 64.6 330 2 1 11.6 6.3 | 13.5 56.3 235 14 7 8.0 4.4
9500 19.0 66.2 325 2 1 10.1 5.5 | 14.1 57.4 235 14 7 7.7 4.2
9250 19.6 67.3 315 2 1 8.7 4.7 | 14.7 58.5 235 15 8 6.4 3.5
9000 20.3 68.5 315 2 1 10.1 5.5 | 15.2 59.4 235 15 8 6.0 3.3
8750 21.1 70.0 310 2 1 10.2 5.6 | 15.6 60.1 230 15 8 6.1 3.3
8500 21.9 71.4 305 2 1 10.2 5.6 | 16.1 61.0 230 15 8 6.2 3.4
8250 22.6 72.7 300 2 1 10.4 5.7 | 16.6 61.9 230 16 8 6.8 3.7
8000 23.4 74.1 300 3 1 9.9 5.5 | 17.1 62.8 225 16 8 6.2 3.4
7750 24.1 75.4 295 3 1 9.4 5.2 | 17.4 63.3 225 16 8 4.8 2.6
7500 24.8 76.6 295 3 2 10.0 5.5 | 17.8 64.0 225 16 8 6.2 3.4
7250 25.6 78.1 290 3 2 10.5 5.8 | 18.3 64.9 220 16 8 7.9 4.3
7000 26.4 79.5 290 3 2 9.9 5.4 | 18.9 66.0 215 16 8 7.2 3.9
6750 27.1 80.8 290 4 2 9.1 5.0 | 19.3 66.7 215 16 8 5.1 2.8
6500 27.8 82.0 285 4 2 9.9 5.4 | 19.6 67.3 210 16 8 6.4 3.5
6250 28.5 83.3 285 4 2 11.0 6.0 | 20.2 68.4 210 15 8 8.7 4.8
6000 29.3 84.7 285 4 2 9.6 5.3 | 20.7 69.3 205 14 7 7.2 4.0
5750 30.1 86.2 285 4 2 12.9 7.1 | 21.2 70.2 200 13 7 9.7 5.3
5500 31.4 88.5 285 4 2 23.5 12.9 | 23.5 74.3 205 10 5 12.9 7.1
________________________________________________________________________________
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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