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Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
000
UXUS97 KBOU 161317
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0717 MDT Wednesday, June 16, 2021
This forecast is for Wednesday, June 16, 2021:
If the trigger temperature of 94.9 F/34.9 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1683 ft/min (8.6 m/s)
Maximum height of thermals.................. 21740 ft MSL (16455 ft AGL)
Forecast maximum temperature................... 100.0 F/38.2 C
Time of trigger temperature.................... 1045 MDT
Time of overdevelopment........................ 1700 MDT
Middle/high clouds during soaring window....... None
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 8542 ft MSL (3256 ft AGL)
Thermal soaring outlook for Thursday 06/17..... 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....................... 40681 ft MSL (35396 ft AGL)
Wave soaring outlook for Thursday 06/17........ Poor
Remarks...
Sunrise/Sunset.................... 05:30:55 / 20:29:42 MDT
Total possible sunshine........... 14 hr 58 min 47 sec (898 min 47 sec)
Altitude of sun at 13:00:18 MDT... 73.60 degrees
Upper air data from rawinsonde observation taken on 06/16/2021 at 0600 MDT
Freezing level.................. 17408 ft MSL (12123 ft AGL)
Convective condensation level... 20605 ft MSL (15320 ft AGL)
Lifted condensation level....... 21283 ft MSL (15998 ft AGL)
Lifted index.................... -1.0
K index......................... +9.6
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 -68.1 -90.6 270 22 11 1.2 0.6 78.7 173.7 23.9 M M
45000 -60.4 -76.7 305 25 13 0.6 0.3 67.2 152.9 18.4 M M
40000 -54.9 -66.8 295 31 16 8.0 4.4 51.7 125.1 9.4 M M
38000 -50.1 -58.2 300 31 16 8.0 4.4 50.0 122.1 8.5 M M
36000 -45.3 -49.5 305 31 16 7.7 4.3 49.0 120.1 7.9 M M
34000 -40.8 -41.4 300 24 12 7.7 4.2 47.1 116.8 6.8 M M
32000 -36.7 -34.1 320 21 11 9.6 5.3 44.7 112.5 5.2 M M
30000 -31.4 -24.5 320 19 10 9.2 5.0 43.9 111.1 4.7 M M
29000 -28.5 -19.3 315 15 8 7.3 4.0 43.1 109.5 4.0 M M
28000 -25.8 -14.4 320 15 8 9.0 4.9 42.6 108.6 3.7 M M
27000 -23.1 -9.6 320 15 8 9.0 4.9 42.3 108.1 3.5 M M
26000 -20.4 -4.7 325 15 8 7.9 4.3 42.1 107.7 3.4 M M
25000 -18.9 -2.0 330 14 7 8.7 4.8 40.4 104.7 2.0 M M
24000 -16.5 2.3 330 12 6 8.1 4.4 39.7 103.5 1.5 M M
23000 -14.1 6.6 335 11 6 8.0 4.4 39.2 102.5 1.0 M M
22000 -11.7 10.9 320 11 6 6.7 3.7 38.5 101.4 0.4 M M
21000 -10.6 12.9 310 11 6 9.0 4.9 36.7 98.0 -1.4 1638 8.3
20000 -7.9 17.8 295 12 6 9.3 5.1 36.5 97.7 -1.5 1526 7.8
19500 -6.5 20.3 295 12 6 9.6 5.3 36.4 97.6 -1.6 1469 7.5
19000 -5.0 23.0 300 12 6 9.8 5.4 36.4 97.5 -1.6 1410 7.2
18500 -3.5 25.7 300 12 6 9.8 5.4 36.4 97.4 -1.6 1350 6.9
18000 -2.0 28.4 305 12 6 9.8 5.4 36.4 97.5 -1.6 1291 6.6
17500 -0.5 31.1 305 12 6 9.8 5.4 36.4 97.5 -1.6 1231 6.3
17000 1.0 33.8 310 13 6 9.8 5.4 36.4 97.6 -1.5 1172 6.0
16500 2.5 36.5 310 13 7 9.6 5.3 36.5 97.7 -1.5 1113 5.7
16000 3.9 39.0 315 13 7 9.4 5.2 36.5 97.7 -1.5 1056 5.4
15500 5.3 41.5 315 13 7 9.4 5.2 36.5 97.6 -1.6 999 5.1
15000 6.7 44.1 315 13 7 9.4 5.2 36.4 97.5 -1.6 943 4.8
14500 8.8 47.8 320 14 7 9.4 5.2 36.4 97.5 -1.7 858 4.4
14000 10.1 50.2 320 14 7 9.4 5.2 36.4 97.5 -1.7 801 4.1
13500 11.5 52.7 325 15 7 9.4 5.2 36.3 97.3 -1.8 744 3.8
13000 12.9 55.2 325 15 8 9.4 5.2 36.2 97.2 -1.9 688 3.5
12500 14.3 57.7 330 16 8 9.4 5.2 36.2 97.1 -2.0 631 3.2
12000 15.7 60.3 330 16 8 9.5 5.2 36.1 97.0 -2.0 575 2.9
11500 17.1 62.8 335 16 8 9.5 5.2 36.0 96.9 -2.2 518 2.6
11000 18.5 65.3 335 16 8 9.5 5.2 36.0 96.7 -2.3 461 2.3
10500 19.9 67.8 340 16 8 8.9 4.9 35.9 96.6 -2.4 405 2.1
10250 20.5 68.9 340 16 8 8.8 4.8 35.8 96.5 -2.4 378 1.9
10000 21.2 70.2 340 16 8 8.8 4.8 35.8 96.4 -2.5 352 1.8
9750 21.8 71.2 340 15 8 8.8 4.8 35.7 96.2 -2.6 325 1.7
9500 22.5 72.5 335 14 7 8.8 4.8 35.6 96.1 -2.7 298 1.5
9250 23.1 73.6 335 13 7 8.8 4.8 35.5 96.0 -2.8 271 1.4
9000 23.8 74.8 330 12 6 8.8 4.8 35.5 95.9 -2.8 244 1.2
8750 24.4 75.9 330 12 6 8.8 4.8 35.4 95.7 -2.9 218 1.1
8500 25.1 77.2 330 11 6 8.8 4.8 35.3 95.6 -3.0 191 1.0
8250 25.7 78.3 330 11 6 8.8 4.8 35.3 95.5 -3.1 164 0.8
8000 26.4 79.5 330 11 6 8.8 4.8 35.2 95.3 -3.2 137 0.7
7750 27.0 80.6 330 11 6 8.8 4.8 35.1 95.2 -3.3 110 0.6
7500 27.7 81.9 335 11 6 8.9 4.9 35.0 95.0 -3.4 84 0.4
7250 28.3 82.9 335 11 6 8.5 4.6 35.0 94.9 -3.5 57 0.3
7000 29.0 84.2 335 11 6 10.1 5.6 34.9 94.8 -3.6 30 0.2
6750 29.6 85.3 330 11 6 3.6 2.0 34.8 94.6 -3.7 3 0.0
6500 29.2 84.6 325 11 6 -13.7 -7.5 33.7 92.6 -4.8 8 0.0
6250 27.8 82.0 320 11 6 -16.8 -9.2 31.6 88.9 -6.9 42 0.2
6000 27.1 80.8 315 11 6 1.3 0.7 30.2 86.3 -8.4 56 0.3
5750 27.4 81.3 310 7 4 -2.7 -1.5 29.8 85.6 -8.9 40 0.2
5500 25.5 77.9 285 3 1 -51.8 -28.4 27.2 80.9 -11.6 91 0.5
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
06/16/2021 at 0900 MDT | 06/16/2021 at 1200 MDT
|
CAPE... +92.2 LI... +0.2 | CAPE... +96.4 LI... +0.5
CINH... -67.3 K Index... +12.1 | CINH... -34.1 K Index... +14.3
|
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 -64.2 -83.6 280 8 4 1.8 1.0 | -64.4 -83.9 260 9 5 1.7 0.9
45000 -60.9 -77.6 290 9 5 3.0 1.7 | -61.0 -77.8 275 10 5 3.3 1.8
40000 -54.8 -66.6 305 16 8 8.0 4.4 | -54.7 -66.5 310 17 9 7.8 4.3
38000 -50.0 -58.0 305 16 8 8.0 4.4 | -50.0 -58.0 310 16 8 7.8 4.3
36000 -45.2 -49.4 310 16 8 7.8 4.3 | -45.3 -49.5 305 15 8 7.9 4.3
34000 -40.6 -41.1 305 14 7 7.7 4.2 | -40.6 -41.1 300 14 7 7.9 4.4
32000 -35.9 -32.6 305 11 6 8.1 4.4 | -35.8 -32.4 295 13 7 8.3 4.5
30000 -31.3 -24.3 305 9 4 7.8 4.3 | -30.8 -23.4 290 10 5 7.5 4.1
29000 -29.0 -20.2 305 7 4 7.8 4.3 | -28.6 -19.5 280 8 4 7.5 4.1
28000 -26.7 -16.1 310 6 3 7.6 4.2 | -26.3 -15.3 275 7 4 7.7 4.2
27000 -24.4 -11.9 305 5 3 7.7 4.2 | -24.1 -11.4 275 7 4 7.7 4.2
26000 -22.1 -7.8 305 4 2 7.7 4.2 | -21.8 -7.2 275 8 4 7.7 4.2
25000 -19.8 -3.6 300 4 2 7.2 3.9 | -19.5 -3.1 275 8 4 7.6 4.1
24000 -17.8 -0.0 305 4 2 7.0 3.8 | -17.3 0.9 285 8 4 7.6 4.2
23000 -15.7 3.7 305 5 3 7.0 3.9 | -15.1 4.8 290 8 4 7.6 4.2
22000 -13.0 8.6 310 6 3 9.0 4.9 | -12.8 9.0 295 7 4 8.5 4.7
21000 -10.3 13.5 310 7 4 8.9 4.9 | -10.3 13.5 305 7 4 8.5 4.6
20000 -7.7 18.1 315 8 4 8.9 4.9 | -7.8 18.0 310 7 4 8.5 4.7
19500 -6.3 20.7 315 8 4 9.5 5.2 | -6.5 20.3 315 7 4 8.7 4.8
19000 -4.9 23.2 315 8 4 9.5 5.2 | -5.2 22.6 315 7 4 8.9 4.9
18500 -3.5 25.7 315 8 4 9.5 5.2 | -3.9 25.0 320 7 4 8.9 4.9
18000 -2.1 28.2 320 8 4 9.4 5.2 | -2.5 27.5 320 7 3 9.3 5.1
17500 -0.6 30.9 320 8 4 9.4 5.2 | -1.2 29.8 320 7 3 9.3 5.1
17000 0.8 33.4 320 7 4 9.5 5.2 | 0.9 33.6 325 6 3 9.5 5.2
16500 2.2 36.0 325 7 4 9.6 5.2 | 2.4 36.3 325 6 3 9.5 5.2
16000 3.6 38.5 325 7 4 9.5 5.2 | 3.8 38.8 325 6 3 9.5 5.2
15500 5.1 41.2 325 7 3 9.5 5.2 | 5.2 41.4 330 5 3 9.4 5.2
15000 6.5 43.7 330 6 3 9.5 5.2 | 6.6 43.9 330 5 3 9.4 5.2
14500 7.9 46.2 330 6 3 9.5 5.2 | 8.0 46.4 335 5 3 9.4 5.1
14000 9.4 48.9 330 6 3 9.5 5.2 | 9.4 48.9 335 5 3 9.4 5.1
13500 10.8 51.4 335 6 3 9.4 5.1 | 10.8 51.4 340 5 2 9.3 5.1
13000 12.2 54.0 335 6 3 9.4 5.1 | 12.2 54.0 340 5 3 9.3 5.1
12500 13.6 56.5 340 6 3 9.2 5.1 | 13.6 56.5 340 5 3 9.4 5.2
12000 14.9 58.8 340 6 3 9.2 5.0 | 15.0 59.0 345 5 3 9.4 5.2
11500 16.3 61.3 345 6 3 9.1 5.0 | 16.4 61.5 345 5 3 9.3 5.1
11000 17.7 63.9 345 6 3 9.1 5.0 | 17.7 63.9 350 5 3 9.6 5.3
10500 19.0 66.2 350 7 3 4.8 2.7 | 18.9 66.0 350 5 3 5.2 2.9
10250 19.3 66.7 350 7 4 7.1 3.9 | 19.4 66.9 350 5 3 9.0 4.9
10000 20.1 68.2 350 7 4 12.1 6.6 | 20.2 68.4 350 5 3 12.1 6.6
9750 20.9 69.6 350 7 4 11.2 6.2 | 21.0 69.8 350 5 2 11.4 6.2
9500 21.7 71.1 350 7 4 8.3 4.6 | 21.8 71.2 355 5 2 7.7 4.2
9250 22.2 72.0 350 7 4 7.0 3.9 | 22.3 72.1 355 5 2 7.6 4.2
9000 22.9 73.2 350 7 4 10.2 5.6 | 23.0 73.4 355 5 2 11.5 6.3
8750 23.6 74.5 345 7 3 10.5 5.7 | 23.9 75.0 355 5 2 11.0 6.0
8500 24.4 75.9 345 7 3 8.9 4.9 | 24.6 76.3 355 5 2 9.2 5.1
8250 25.0 77.0 345 7 3 7.5 4.1 | 25.2 77.4 360 5 2 7.8 4.3
8000 25.6 78.1 340 7 3 8.5 4.7 | 25.9 78.6 360 5 2 10.4 5.7
7750 26.2 79.2 340 6 3 8.7 4.8 | 26.7 80.1 360 5 2 11.4 6.2
7500 26.8 80.2 335 6 3 6.7 3.7 | 27.5 81.5 360 5 2 9.1 5.0
7250 27.3 81.1 330 6 3 5.6 3.1 | 28.1 82.6 360 5 2 7.7 4.2
7000 27.7 81.9 330 6 3 6.4 3.5 | 28.7 83.7 360 5 2 10.4 5.7
6750 28.1 82.6 325 6 3 5.4 2.9 | 29.6 85.3 360 5 2 12.8 7.0
6500 28.4 83.1 320 5 3 3.1 1.7 | 30.5 86.9 005 5 2 10.7 5.9
6250 28.5 83.3 315 4 2 2.4 1.3 | 31.3 88.3 005 5 2 10.5 5.8
6000 28.7 83.7 315 4 2 3.1 1.7 | 32.0 89.6 005 5 2 9.1 5.0
5750 29.0 84.2 305 4 2 7.5 4.1 | 32.8 91.0 005 4 2 15.1 8.3
5500 29.7 85.5 300 3 1 13.2 7.2 | 34.5 94.1 005 4 2 29.5 16.2
06/16/2021 at 1500 MDT | 06/16/2021 at 1800 MDT
|
CAPE... +150.4 LI... +0.1 | CAPE... +225.9 LI... -0.2
CINH... -18.1 K Index... +19.1 | CINH... -60.6 K Index... +22.1
|
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 -64.6 -84.3 280 12 6 1.2 0.7 | -65.1 -85.2 285 13 7 1.0 0.6
45000 -61.5 -78.7 290 15 8 3.5 1.9 | -62.2 -80.0 295 18 9 4.0 2.2
40000 -55.0 -67.0 310 18 9 8.2 4.5 | -54.7 -66.5 305 16 8 8.2 4.5
38000 -50.2 -58.4 305 16 8 8.2 4.5 | -49.8 -57.6 300 15 8 8.2 4.5
36000 -45.3 -49.5 305 15 8 8.2 4.5 | -44.8 -48.6 295 13 7 8.2 4.5
34000 -40.3 -40.5 300 14 7 8.3 4.6 | -39.9 -39.8 295 13 6 8.2 4.5
32000 -35.3 -31.5 295 13 7 8.7 4.8 | -34.9 -30.8 295 12 6 8.5 4.7
30000 -30.1 -22.2 285 12 6 7.7 4.2 | -30.3 -22.5 290 12 6 7.8 4.3
29000 -27.8 -18.0 280 12 6 7.7 4.2 | -27.9 -18.2 290 12 6 7.8 4.3
28000 -25.6 -14.1 275 12 6 7.2 4.0 | -25.6 -14.1 285 11 6 7.3 4.0
27000 -23.4 -10.1 275 12 6 7.2 4.0 | -23.4 -10.1 285 11 6 7.4 4.1
26000 -21.3 -6.3 275 12 6 7.2 4.0 | -21.2 -6.2 280 10 5 7.4 4.1
25000 -19.2 -2.6 275 12 6 7.3 4.0 | -19.0 -2.2 280 10 5 7.5 4.1
24000 -17.0 1.4 280 11 5 7.4 4.0 | -16.8 1.8 280 9 5 7.5 4.1
23000 -14.9 5.2 280 10 5 7.4 4.1 | -14.0 6.8 280 8 4 7.5 4.1
22000 -12.7 9.1 285 8 4 8.4 4.6 | -11.8 10.8 280 6 3 7.8 4.3
21000 -10.2 13.6 290 6 3 8.3 4.6 | -9.5 14.9 270 5 3 7.8 4.3
20000 -7.8 18.0 295 4 2 8.4 4.6 | -7.3 18.9 260 4 2 7.8 4.3
19500 -6.6 20.1 300 3 2 8.7 4.8 | -6.1 21.0 250 3 1 8.1 4.5
19000 -5.3 22.5 310 3 2 8.9 4.9 | -4.9 23.2 240 2 1 8.2 4.5
18500 -3.9 25.0 320 2 1 8.9 4.9 | -3.7 25.3 215 2 1 8.3 4.5
18000 -2.6 27.3 330 2 1 9.4 5.2 | -2.4 27.7 190 1 1 8.9 4.9
17500 -0.5 31.1 345 2 1 9.4 5.1 | -1.1 30.0 160 1 1 8.9 4.9
17000 0.9 33.6 360 2 1 9.5 5.2 | 0.2 32.4 135 1 1 9.0 4.9
16500 2.3 36.1 010 2 1 9.5 5.2 | 1.6 34.9 115 2 1 9.0 4.9
16000 3.7 38.7 015 2 1 9.6 5.3 | 2.9 37.2 100 2 1 9.0 5.0
15500 5.2 41.4 025 2 1 9.7 5.3 | 4.2 39.6 090 2 1 9.0 5.0
15000 6.6 43.9 025 3 1 9.6 5.3 | 5.6 42.1 080 2 1 9.0 5.0
14500 8.0 46.4 030 3 1 9.4 5.2 | 7.0 44.6 070 3 1 9.3 5.1
14000 9.4 48.9 030 3 2 9.4 5.2 | 8.4 47.1 060 3 2 9.3 5.1
13500 10.8 51.4 030 3 2 9.3 5.1 | 9.8 49.6 055 3 2 9.3 5.1
13000 12.2 54.0 030 4 2 9.3 5.1 | 11.1 52.0 050 4 2 9.3 5.1
12500 13.6 56.5 030 4 2 9.5 5.2 | 12.5 54.5 040 4 2 9.2 5.1
12000 15.0 59.0 025 4 2 9.5 5.2 | 13.9 57.0 035 4 2 9.2 5.0
11500 16.4 61.5 025 5 2 9.4 5.2 | 15.3 59.5 030 4 2 9.1 5.0
11000 17.8 64.0 025 5 3 9.6 5.3 | 16.6 61.9 025 5 2 8.9 4.9
10500 19.0 66.2 020 5 3 5.6 3.1 | 18.0 64.4 020 5 3 6.0 3.3
10250 19.5 67.1 020 5 3 9.0 4.9 | 18.3 64.9 020 6 3 6.9 3.8
10000 20.4 68.7 015 6 3 12.1 6.7 | 19.1 66.4 015 6 3 11.0 6.1
9750 21.2 70.2 015 6 3 11.6 6.4 | 19.8 67.6 015 6 3 10.4 5.7
9500 22.0 71.6 015 6 3 7.9 4.4 | 20.6 69.1 015 6 3 8.7 4.8
9250 22.5 72.5 010 6 3 7.5 4.1 | 21.1 70.0 015 7 3 7.6 4.1
9000 23.2 73.8 010 6 3 11.1 6.1 | 21.8 71.2 010 7 4 9.3 5.1
8750 24.0 75.2 010 7 3 10.7 5.9 | 22.5 72.5 010 7 4 9.6 5.3
8500 24.8 76.6 005 7 4 9.1 5.0 | 23.2 73.8 010 7 4 8.2 4.5
8250 25.4 77.7 005 7 4 7.7 4.2 | 23.7 74.7 010 8 4 6.8 3.7
8000 26.0 78.8 005 7 4 9.8 5.4 | 24.2 75.6 005 8 4 7.9 4.3
7750 26.8 80.2 005 8 4 10.6 5.8 | 24.8 76.6 005 8 4 8.4 4.6
7500 27.5 81.5 360 8 4 8.9 4.9 | 25.4 77.7 360 8 4 7.7 4.2
7250 28.1 82.6 360 8 4 7.6 4.2 | 25.9 78.6 360 8 4 7.1 3.9
7000 28.8 83.8 360 8 4 9.8 5.4 | 26.5 79.7 355 9 4 8.2 4.5
6750 29.6 85.3 360 8 4 12.0 6.6 | 27.1 80.8 355 9 4 10.3 5.7
6500 30.4 86.7 355 9 4 10.5 5.8 | 27.9 82.2 355 8 4 10.3 5.6
6250 31.2 88.2 355 9 4 10.2 5.6 | 28.6 83.5 350 8 4 10.2 5.6
6000 31.9 89.4 355 9 4 9.1 5.0 | 29.4 84.9 350 8 4 8.8 4.8
5750 32.7 90.9 355 9 4 15.0 8.3 | 30.0 86.0 350 8 4 11.2 6.2
5500 34.3 93.7 355 8 4 29.1 16.0 | 32.4 90.3 350 6 3 4.7 2.6
________________________________________________________________________________
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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