Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
077
UXUS97 KBOU 270029
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1828 MDT Thursday, September 26, 2024
This forecast is for Friday, September 27, 2024:
If the trigger temperature of 81.8 F/27.7 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 765 ft/min (3.9 m/s)
Maximum height of thermals.................. 13697 ft MSL (8383 ft AGL)
Forecast maximum temperature................... 84.0 F/29.3 C
Time of trigger temperature.................... 1345 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................. 7649 ft MSL (2336 ft AGL)
Thermal soaring outlook for Saturday 09/28..... 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)................ Neither
Potential height of wave....................... 14417 ft MSL (9103 ft AGL)
Wave soaring outlook for Saturday 09/28........ Poor
Remarks...
Sunrise/Sunset.................... 06:52:42 / 18:47:44 MDT
Total possible sunshine........... 11 hr 55 min 1 sec (715 min 1 sec)
Altitude of sun at 12:50:13 MDT... 48.12 degrees
Upper air data from numerical model forecast valid on 09/27/2024 at 0600 MDT
Freezing level.................. 15070 ft MSL (9756 ft AGL)
Convective condensation level... 17737 ft MSL (12423 ft AGL)
Lifted condensation level....... 17477 ft MSL (12164 ft AGL)
Lifted index.................... +1.2
K index......................... +19.0
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 -63.0 -81.4 335 23 12 4.2 2.3 M M M M M
45000 -55.8 -68.4 335 25 13 5.2 2.9 M M M M M
40000 -47.9 -54.2 340 22 11 5.8 3.2 M M M M M
38000 -44.4 -47.9 340 22 11 5.9 3.2 M M M M M
36000 -40.8 -41.4 340 21 11 5.9 3.3 M M M M M
34000 -38.2 -36.8 340 18 9 4.1 2.2 M M M M M
32000 -35.4 -31.7 330 15 7 4.0 2.2 M M M M M
30000 -32.9 -27.2 320 13 7 4.3 2.3 42.6 108.7 10.4 M M
29000 -31.6 -24.9 315 13 7 4.3 2.3 40.5 104.9 8.9 M M
28000 -30.3 -22.5 310 13 7 7.3 4.0 38.6 101.5 7.6 M M
27000 -27.5 -17.5 310 13 7 9.2 5.0 38.3 100.9 7.4 M M
26000 -24.8 -12.6 305 13 7 9.2 5.0 38.0 100.5 7.3 M M
25000 -22.0 -7.6 300 14 7 9.1 5.0 37.9 100.3 7.3 M M
24000 -19.6 -3.3 305 13 7 8.0 4.4 37.3 99.1 6.8 M M
23000 -17.2 1.0 310 13 7 8.0 4.4 36.6 97.9 6.4 M M
22000 -14.8 5.4 315 13 7 7.3 4.0 36.1 96.9 6.0 M M
21000 -13.3 8.1 310 13 7 5.0 2.8 34.4 93.9 4.6 M M
20000 -11.9 10.6 305 13 7 5.3 2.9 32.8 91.0 3.1 M M
19500 -11.1 12.0 300 14 7 5.3 2.9 32.0 89.7 2.4 M M
19000 -10.3 13.5 300 13 7 7.2 4.0 31.4 88.6 1.8 M M
18500 -9.3 15.3 295 11 6 7.2 4.0 31.0 87.8 1.4 M M
18000 -8.3 17.1 290 9 5 7.7 4.2 30.6 87.0 0.9 M M
17500 -7.1 19.2 300 7 3 8.4 4.6 30.3 86.5 0.7 M M
17000 -5.3 22.5 335 4 2 9.0 4.9 30.0 85.9 0.3 M M
16500 -3.8 25.2 340 4 2 9.6 5.2 29.9 85.9 0.3 M M
16000 -2.4 27.7 345 4 2 9.6 5.3 29.9 85.8 0.3 M M
15500 -1.0 30.2 355 4 2 9.4 5.1 29.9 85.7 0.2 M M
15000 0.5 32.9 005 5 3 9.4 5.2 29.8 85.6 0.2 M M
14500 1.9 35.4 010 6 3 9.1 5.0 29.7 85.5 0.1 M M
14000 3.2 37.8 020 8 4 9.1 5.0 29.6 85.3 0.0 M M
13500 4.6 40.3 020 9 5 9.2 5.1 29.5 85.1 -0.0 735 3.7
13000 6.0 42.8 025 11 6 9.3 5.1 29.4 85.0 -0.1 679 3.4
12500 7.4 45.3 025 13 6 9.0 4.9 29.4 84.9 -0.2 622 3.2
12000 8.7 47.7 025 14 7 8.7 4.8 29.2 84.6 -0.3 568 2.9
11500 10.0 50.0 020 15 8 8.9 4.9 29.0 84.3 -0.4 514 2.6
11000 11.4 52.5 020 16 8 8.9 4.9 29.0 84.1 -0.5 457 2.3
10500 12.8 55.0 015 16 8 5.0 2.7 28.9 84.0 -0.6 401 2.0
10250 13.0 55.4 015 16 8 5.2 2.8 28.3 83.0 -1.1 388 2.0
10000 13.7 56.7 015 17 9 11.3 6.2 28.3 83.0 -1.1 359 1.8
9750 14.5 58.1 015 17 9 11.1 6.1 28.4 83.1 -1.1 327 1.7
9500 15.3 59.5 015 17 9 8.6 4.7 28.5 83.2 -1.0 296 1.5
9250 15.8 60.4 015 17 9 5.7 3.1 28.2 82.8 -1.2 274 1.4
9000 16.3 61.3 010 17 9 7.3 4.0 28.0 82.3 -1.5 252 1.3
8750 16.9 62.4 010 18 9 8.1 4.4 27.8 82.1 -1.6 227 1.2
8500 17.4 63.3 010 18 9 7.0 3.8 27.7 81.8 -1.8 202 1.0
8250 17.9 64.2 010 17 9 6.3 3.4 27.4 81.3 -2.1 182 0.9
8000 18.3 64.9 010 16 8 6.5 3.6 27.1 80.9 -2.4 161 0.8
7750 18.7 65.7 010 16 8 5.2 2.8 26.9 80.3 -2.7 141 0.7
7500 18.9 66.0 015 16 8 0.8 0.4 26.4 79.4 -3.3 129 0.7
7250 18.8 65.8 015 18 9 -1.0 -0.6 25.5 78.0 -4.2 125 0.6
7000 18.6 65.5 020 19 10 -1.5 -0.8 24.7 76.5 -5.0 122 0.6
6750 18.3 64.9 020 21 11 -2.0 -1.1 23.8 74.9 -6.1 124 0.6
6500 18.3 64.9 015 21 11 0.6 0.3 23.0 73.5 -6.9 117 0.6
6250 18.5 65.3 005 21 11 1.8 1.0 22.4 72.3 -7.4 104 0.5
6000 18.7 65.7 355 22 11 0.7 0.4 21.8 71.2 -8.0 91 0.5
5750 18.7 65.7 345 20 10 -1.6 -0.9 21.0 69.8 -8.7 83 0.4
5500 18.6 65.5 340 14 7 -2.5 -1.4 20.1 68.2 -9.6 79 0.4
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
09/27/2024 at 0900 MDT | 09/27/2024 at 1200 MDT
|
CAPE... 0.0 LI... -2.0 | CAPE... +50.6 LI... -1.7
CINH... 0.0 K Index... +21.3 | CINH... -134.8 K Index... +21.2
|
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 -63.1 -81.6 350 18 9 3.6 2.0 | -62.5 -80.5 355 12 6 4.0 2.2
45000 -56.2 -69.2 340 20 10 5.9 3.2 | -56.0 -68.8 330 14 7 5.0 2.8
40000 -47.5 -53.5 330 19 10 5.5 3.0 | -48.2 -54.8 310 16 8 6.2 3.4
38000 -44.2 -47.6 340 20 10 5.5 3.0 | -44.5 -48.1 325 18 9 6.2 3.4
36000 -40.9 -41.6 345 21 11 5.5 3.0 | -40.7 -41.3 340 21 11 6.3 3.5
34000 -37.6 -35.7 350 20 10 5.4 3.0 | -36.9 -34.4 355 18 10 5.5 3.0
32000 -34.0 -29.2 355 18 9 5.5 3.0 | -33.7 -28.7 015 17 9 5.6 3.1
30000 -31.5 -24.7 350 15 8 3.9 2.1 | -31.3 -24.3 015 13 7 3.7 2.0
29000 -30.4 -22.7 345 14 7 3.9 2.1 | -30.1 -22.2 005 11 6 3.7 2.0
28000 -29.1 -20.4 340 12 6 6.3 3.5 | -29.0 -20.2 360 10 5 6.2 3.4
27000 -26.8 -16.2 335 12 6 7.8 4.3 | -26.7 -16.1 355 9 5 7.6 4.2
26000 -24.5 -12.1 330 12 6 7.8 4.3 | -24.4 -11.9 345 9 5 7.6 4.2
25000 -22.2 -8.0 325 12 6 7.8 4.3 | -22.1 -7.8 335 9 5 7.6 4.2
24000 -19.9 -3.8 325 12 6 7.7 4.2 | -19.8 -3.6 340 9 5 7.8 4.3
23000 -17.6 0.3 325 12 6 7.7 4.2 | -17.5 0.5 340 9 5 7.8 4.3
22000 -15.3 4.5 325 12 6 7.0 3.8 | -15.1 4.8 340 9 5 7.1 3.9
21000 -13.7 7.3 325 11 6 5.1 2.8 | -13.5 7.7 335 8 4 5.4 3.0
20000 -12.3 9.9 320 11 6 5.3 2.9 | -11.9 10.6 325 8 4 5.6 3.1
19500 -11.6 11.1 320 11 5 5.2 2.9 | -11.1 12.0 320 7 4 5.5 3.0
19000 -10.6 12.9 320 10 5 8.4 4.6 | -10.2 13.6 315 8 4 8.3 4.6
18500 -9.4 15.1 315 9 5 8.2 4.5 | -9.0 15.8 305 10 5 8.1 4.5
18000 -8.2 17.2 310 9 4 7.9 4.3 | -7.8 18.0 305 12 6 7.9 4.3
17500 -7.1 19.2 315 6 3 7.6 4.2 | -6.7 19.9 300 9 5 7.6 4.2
17000 -5.5 22.1 335 3 1 8.2 4.5 | -5.1 22.8 295 5 2 8.0 4.4
16500 -4.3 24.3 345 3 2 8.6 4.7 | -3.9 25.0 290 3 2 8.4 4.6
16000 -3.0 26.6 350 4 2 8.7 4.8 | -2.7 27.1 275 2 1 8.5 4.7
15500 -1.6 29.1 360 5 2 9.8 5.4 | -1.3 29.7 285 1 1 9.3 5.1
15000 -0.1 31.8 010 6 3 9.7 5.3 | 0.1 32.2 340 1 1 9.2 5.1
14500 1.3 34.3 020 7 4 9.6 5.3 | 1.5 34.7 020 2 1 9.8 5.4
14000 2.8 37.0 025 9 4 9.6 5.3 | 3.0 37.4 035 3 2 9.8 5.4
13500 4.3 39.7 030 10 5 9.6 5.3 | 4.4 39.9 045 5 3 9.4 5.1
13000 5.7 42.3 035 12 6 9.7 5.3 | 5.8 42.4 050 7 3 9.3 5.1
12500 7.2 45.0 035 13 7 9.2 5.0 | 7.2 45.0 050 8 4 9.3 5.1
12000 8.5 47.3 030 14 7 8.9 4.9 | 8.6 47.5 045 9 5 9.3 5.1
11500 9.9 49.8 030 14 7 8.7 4.8 | 10.1 50.2 045 10 5 8.7 4.8
11000 11.1 52.0 030 14 7 8.3 4.6 | 11.3 52.3 040 10 5 8.1 4.4
10500 12.4 54.3 025 14 7 5.1 2.8 | 12.5 54.5 035 11 6 4.4 2.4
10250 12.6 54.7 025 14 7 4.3 2.4 | 12.6 54.7 035 11 5 4.8 2.6
10000 13.1 55.6 020 13 7 9.3 5.1 | 13.2 55.8 030 10 5 10.5 5.7
9750 13.8 56.8 020 13 6 9.9 5.4 | 13.9 57.0 025 10 5 10.6 5.8
9500 14.4 57.9 015 12 6 7.2 4.0 | 14.6 58.3 025 10 5 6.7 3.7
9250 14.7 58.5 020 11 6 4.8 2.6 | 14.8 58.6 025 9 5 3.1 1.7
9000 15.0 59.0 025 11 5 5.6 3.1 | 15.0 59.0 025 8 4 5.6 3.1
8750 15.3 59.5 035 10 5 5.4 3.0 | 15.4 59.7 025 7 4 6.2 3.4
8500 15.6 60.1 045 11 5 2.2 1.2 | 15.7 60.3 025 7 3 2.4 1.3
8250 15.6 60.1 050 11 6 0.3 0.2 | 15.7 60.3 015 7 3 1.0 0.5
8000 15.6 60.1 050 12 6 -0.5 -0.3 | 15.8 60.4 005 7 3 -0.9 -0.5
7750 15.5 59.9 055 13 7 -1.7 -0.9 | 15.6 60.1 350 8 4 0.4 0.2
7500 15.4 59.7 045 13 6 0.8 0.4 | 16.0 60.8 345 9 4 7.8 4.3
7250 15.6 60.1 030 13 7 2.4 1.3 | 16.7 62.1 345 9 4 9.6 5.3
7000 15.7 60.3 015 14 7 0.3 0.2 | 17.4 63.3 345 9 4 9.7 5.3
6750 15.9 60.6 005 17 8 4.7 2.6 | 18.2 64.8 345 9 4 10.5 5.7
6500 16.5 61.7 360 17 8 10.1 5.6 | 18.9 66.0 345 9 4 10.4 5.7
6250 17.2 63.0 355 16 8 8.6 4.7 | 19.7 67.5 345 9 4 10.1 5.5
6000 17.9 64.2 350 16 8 10.8 5.9 | 20.5 68.9 345 8 4 11.2 6.1
5750 18.9 66.0 345 14 7 13.4 7.3 | 21.5 70.7 345 8 4 17.5 9.6
5500 19.9 67.8 340 11 6 12.3 6.8 | 23.1 73.6 345 8 4 24.4 13.4
09/27/2024 at 1500 MDT | 09/27/2024 at 1800 MDT
|
CAPE... +363.1 LI... -2.8 | CAPE... +299.5 LI... -2.3
CINH... -33.8 K Index... +20.6 | CINH... -30.5 K Index... +25.7
|
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 -61.9 -79.4 320 8 4 4.3 2.4 | -62.1 -79.8 335 13 7 4.3 2.4
45000 -55.2 -67.4 315 14 7 4.6 2.5 | -55.5 -67.9 335 15 8 4.7 2.6
40000 -48.1 -54.6 310 23 12 5.5 3.0 | -48.0 -54.4 355 20 10 5.3 2.9
38000 -44.8 -48.6 330 18 9 5.5 3.0 | -44.9 -48.8 360 17 9 5.3 2.9
36000 -41.5 -42.7 355 16 8 5.5 3.0 | -41.7 -43.1 015 16 8 5.3 2.9
34000 -37.5 -35.5 025 21 11 5.9 3.3 | -38.1 -36.6 030 23 12 6.0 3.3
32000 -34.0 -29.2 035 27 14 6.0 3.3 | -34.5 -30.1 040 32 16 6.0 3.3
30000 -30.9 -23.6 035 23 12 4.9 2.7 | -30.9 -23.6 040 31 16 6.1 3.3
29000 -29.5 -21.1 030 20 10 4.9 2.7 | -29.1 -20.4 040 29 15 6.1 3.3
28000 -28.0 -18.4 025 16 8 5.9 3.2 | -27.2 -17.0 040 28 14 6.0 3.3
27000 -26.1 -15.0 020 13 7 6.5 3.5 | -25.1 -13.2 035 23 12 5.8 3.2
26000 -24.1 -11.4 010 11 5 6.5 3.5 | -23.3 -9.9 030 20 10 5.8 3.2
25000 -22.2 -8.0 350 9 4 6.5 3.6 | -21.6 -6.9 020 17 9 6.3 3.5
24000 -20.0 -4.0 345 8 4 7.5 4.1 | -19.4 -2.9 015 15 8 7.3 4.0
23000 -17.7 0.1 345 8 4 7.5 4.1 | -17.3 0.9 005 13 7 7.3 4.0
22000 -15.5 4.1 345 8 4 7.2 4.0 | -15.1 4.8 355 11 6 7.1 3.9
21000 -13.5 7.7 330 8 4 6.4 3.5 | -13.0 8.6 345 12 6 7.0 3.8
20000 -11.6 11.1 315 8 4 6.5 3.6 | -11.0 12.2 335 12 6 7.0 3.8
19500 -10.7 12.7 310 8 4 6.4 3.5 | -9.9 14.2 330 13 7 7.0 3.9
19000 -9.7 14.5 300 10 5 8.4 4.6 | -8.8 16.2 325 14 7 8.8 4.8
18500 -8.5 16.7 295 14 7 8.3 4.5 | -7.5 18.5 320 15 8 8.9 4.9
18000 -7.3 18.9 295 17 9 8.4 4.6 | -6.3 20.7 320 16 8 7.8 4.3
17500 -6.1 21.0 295 15 8 8.5 4.6 | -5.4 22.3 310 15 8 7.2 4.0
17000 -4.3 24.3 290 11 6 8.3 4.6 | -4.4 24.1 305 15 8 7.3 4.0
16500 -3.1 26.4 290 9 5 8.1 4.4 | -3.4 25.9 300 12 6 7.5 4.1
16000 -1.9 28.6 285 7 4 8.1 4.5 | -2.3 27.9 295 9 5 7.5 4.1
15500 -0.7 30.7 280 5 3 8.3 4.6 | -1.2 29.8 285 6 3 8.2 4.5
15000 0.5 32.9 270 4 2 8.2 4.5 | 0.1 32.2 275 5 2 8.3 4.6
14500 1.8 35.2 265 3 1 9.2 5.1 | 1.4 34.5 260 3 2 8.3 4.6
14000 3.2 37.8 260 1 1 9.2 5.0 | 3.3 37.9 210 2 1 8.3 4.5
13500 4.6 40.3 000 0 0 9.2 5.0 | 4.6 40.3 165 2 1 9.2 5.0
13000 6.0 42.8 080 2 1 9.2 5.0 | 6.0 42.8 125 3 2 9.3 5.1
12500 7.4 45.3 080 4 2 9.2 5.0 | 7.4 45.3 110 5 3 9.2 5.0
12000 8.8 47.8 075 6 3 9.2 5.0 | 8.7 47.7 100 6 3 9.2 5.0
11500 10.2 50.4 075 7 4 8.9 4.9 | 10.1 50.2 095 7 4 8.7 4.8
11000 11.5 52.7 065 8 4 8.4 4.6 | 11.3 52.3 090 8 4 8.4 4.6
10500 12.7 54.9 060 9 5 4.5 2.5 | 12.4 54.3 085 8 4 2.8 1.5
10250 12.9 55.2 060 9 5 5.7 3.1 | 12.4 54.3 085 8 4 5.1 2.8
10000 13.6 56.5 055 9 5 11.5 6.3 | 13.1 55.6 075 7 4 12.3 6.8
9750 14.4 57.9 055 9 5 10.8 5.9 | 13.8 56.8 060 6 3 10.7 5.9
9500 15.1 59.2 050 9 5 7.5 4.1 | 14.5 58.1 050 6 3 8.5 4.7
9250 15.4 59.7 050 9 5 4.3 2.4 | 15.0 59.0 045 6 3 6.9 3.8
9000 15.7 60.3 045 8 4 7.0 3.9 | 15.6 60.1 045 6 3 9.9 5.4
8750 16.2 61.2 040 7 4 7.9 4.4 | 16.3 61.3 045 6 3 10.7 5.9
8500 16.7 62.1 030 7 4 7.3 4.0 | 17.1 62.8 040 6 3 9.9 5.4
8250 17.2 63.0 025 7 4 6.7 3.7 | 17.8 64.0 040 6 3 9.4 5.2
8000 17.6 63.7 015 7 4 8.1 4.5 | 18.5 65.3 040 5 3 10.2 5.6
7750 18.3 64.9 015 7 4 10.0 5.5 | 19.3 66.7 035 5 3 10.5 5.8
7500 19.1 66.4 015 7 3 10.0 5.5 | 20.1 68.2 035 5 3 9.8 5.4
7250 19.8 67.6 015 7 3 10.1 5.6 | 20.8 69.4 035 5 3 9.6 5.3
7000 20.6 69.1 010 7 3 9.8 5.4 | 21.5 70.7 030 5 3 10.0 5.5
6750 21.3 70.3 010 7 3 10.0 5.5 | 22.3 72.1 030 5 3 10.0 5.5
6500 22.1 71.8 010 7 3 10.7 5.9 | 23.0 73.4 030 5 3 9.7 5.3
6250 22.9 73.2 010 6 3 10.2 5.6 | 23.7 74.7 025 5 3 9.6 5.3
6000 23.7 74.7 010 6 3 12.0 6.6 | 24.5 76.1 025 5 2 10.1 5.6
5750 24.7 76.5 010 6 3 17.3 9.5 | 25.2 77.4 025 5 2 10.4 5.7
5500 26.2 79.2 010 6 3 20.7 11.4 | 26.0 78.8 020 4 2 9.3 5.1
________________________________________________________________________________
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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