Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
782
UXUS97 KBOU 081227
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0525 MST Sunday, December 8, 2024
This forecast is for Sunday, December 8, 2024:
If the trigger temperature of 66.5 F/19.2 C is reached...then
Thermal Soaring Index....................... Poor
Maximum rate of lift........................ 0 ft/min (0.0 m/s)
Maximum height of thermals.................. 6270 ft MSL (960 ft AGL)
Forecast maximum temperature................... 59.0 F/15.5 C
Time of trigger temperature.................... None
Time of overdevelopment........................ 1100 MST
Middle/high clouds during soaring window....... Broken/overcast opaque middle
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 6022 ft MSL (712 ft AGL)
Thermal soaring outlook for Monday 12/09....... Poor
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1700 MST)......... No change
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1700 MST)................ Weak NVA
Potential height of wave....................... 21320 ft MSL (16010 ft AGL)
Wave soaring outlook for Monday 12/09.......... Poor
Remarks...
Sunrise/Sunset.................... 07:08:43 / 16:34:43 MST
Total possible sunshine........... 9 hr 26 min 0 sec (566 min 0 sec)
Altitude of sun at 11:51:43 MST... 27.38 degrees
Upper air data from numerical model forecast valid on 12/08/2024 at 0500 MST
Freezing level.................. 12941 ft MSL (7631 ft AGL)
Convective condensation level... 19985 ft MSL (14675 ft AGL)
Lifted condensation level....... 14855 ft MSL (9545 ft AGL)
Lifted index.................... +9.5
K index......................... +8.6
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 -62.7 -80.9 275 32 17 1.4 0.8 M M M M M
45000 -60.7 -77.3 285 32 16 -0.9 -0.5 M M M M M
40000 -62.2 -80.0 295 32 16 -1.0 -0.5 M M M M M
38000 -59.2 -74.6 295 28 14 8.0 4.4 M M M M M
36000 -54.4 -65.9 290 22 11 8.0 4.4 M M M M M
34000 -48.8 -55.8 280 17 9 8.5 4.7 M M M M M
32000 -43.7 -46.7 280 16 8 8.5 4.7 M M M M M
30000 -38.7 -37.7 280 14 7 8.2 4.5 36.9 98.5 16.6 M M
29000 -36.2 -33.2 280 14 7 8.3 4.5 36.3 97.4 16.3 M M
28000 -33.7 -28.7 285 14 7 8.3 4.5 35.8 96.4 16.1 M M
27000 -31.3 -24.3 290 14 7 7.2 4.0 35.2 95.4 15.8 M M
26000 -29.2 -20.6 295 13 7 7.3 4.0 34.2 93.5 15.2 M M
25000 -27.0 -16.6 300 13 6 7.4 4.0 33.3 92.0 14.6 M M
24000 -24.8 -12.6 310 12 6 7.4 4.1 32.5 90.5 14.2 M M
23000 -22.6 -8.7 315 14 7 7.4 4.1 31.6 88.8 13.5 M M
22000 -20.4 -4.7 315 15 8 7.4 4.1 30.7 87.3 13.0 M M
21000 -18.2 -0.8 320 16 8 7.4 4.0 29.9 85.9 12.4 M M
20000 -16.0 3.2 320 17 9 7.4 4.0 29.0 84.3 11.8 M M
19500 -14.9 5.2 320 17 9 7.4 4.0 28.6 83.5 11.5 M M
19000 -13.8 7.2 320 18 9 7.4 4.0 28.2 82.8 11.2 M M
18500 -12.7 9.1 320 18 9 7.5 4.1 27.9 82.2 11.0 M M
18000 -11.5 11.3 320 18 9 7.6 4.2 27.5 81.5 10.7 M M
17500 -9.8 14.4 320 18 9 7.8 4.3 27.0 80.5 10.3 M M
17000 -8.7 16.3 320 18 9 7.9 4.3 26.6 79.9 10.0 M M
16500 -7.5 18.5 315 18 9 7.8 4.3 26.3 79.4 9.8 M M
16000 -6.4 20.5 315 17 9 7.3 4.0 25.9 78.7 9.5 M M
15500 -5.3 22.5 315 17 9 7.4 4.0 25.5 77.9 9.1 M M
15000 -4.3 24.3 310 16 8 6.9 3.8 25.1 77.2 8.8 M M
14500 -3.2 26.2 310 15 8 6.9 3.8 24.6 76.3 8.4 M M
14000 -2.2 28.0 310 14 7 7.3 4.0 24.2 75.5 8.0 M M
13500 -1.1 30.0 310 14 7 7.4 4.0 23.8 74.8 7.7 M M
13000 -0.0 32.0 310 13 7 7.2 3.9 23.4 74.2 7.4 M M
12500 1.0 33.8 310 12 6 7.0 3.8 23.0 73.3 7.0 M M
12000 2.1 35.8 305 12 6 6.8 3.7 22.5 72.5 6.6 M M
11500 3.1 37.6 305 11 5 6.5 3.5 22.0 71.6 6.2 M M
11000 4.0 39.2 305 10 5 6.3 3.5 21.5 70.6 5.7 M M
10500 4.9 40.8 300 9 5 5.8 3.2 20.9 69.6 5.2 M M
10250 5.4 41.7 300 8 4 7.3 4.0 20.6 69.1 4.9 M M
10000 6.0 42.8 295 8 4 7.4 4.0 20.5 68.9 4.8 M M
9750 6.4 43.5 295 8 4 5.6 3.1 20.2 68.3 4.5 M M
9500 6.9 44.4 290 8 4 5.6 3.1 19.9 67.7 4.2 M M
9250 7.3 45.1 290 8 4 5.6 3.1 19.5 67.2 3.9 M M
9000 7.7 45.9 285 8 4 7.1 3.9 19.3 66.7 3.7 M M
8750 8.3 46.9 285 8 4 7.5 4.1 19.1 66.4 3.5 M M
8500 8.8 47.8 285 9 4 6.5 3.5 18.9 66.0 3.3 M M
8250 9.3 48.7 285 9 5 7.2 3.9 18.6 65.5 3.1 M M
8000 9.9 49.8 285 10 5 9.0 4.9 18.5 65.3 3.0 M M
7750 10.6 51.1 290 11 6 8.4 4.6 18.5 65.2 2.9 M M
7500 11.2 52.2 295 13 7 7.5 4.1 18.3 64.9 2.8 M M
7250 11.7 53.1 300 14 7 6.6 3.6 18.1 64.6 2.6 M M
7000 12.1 53.8 300 17 9 4.7 2.6 17.8 64.0 2.3 M M
6750 12.4 54.3 300 21 11 1.9 1.0 17.3 63.2 1.9 M M
6500 12.5 54.5 295 24 12 2.7 1.5 16.7 62.0 1.2 M M
6250 12.3 54.1 290 26 13 -16.7 -9.2 15.7 60.3 0.3 M M
6000 10.1 50.2 285 22 11 -33.3 -18.3 12.7 54.9 -2.7 94 0.5
5750 7.9 46.2 275 19 10 -29.5 -16.2 9.7 49.5 -5.6 154 0.8
5500 5.2 41.4 250 13 7 -44.3 -24.3 6.3 43.4 -9.1 227 1.2
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
12/08/2024 at 0800 MST | 12/08/2024 at 1100 MST
|
CAPE... 0.0 LI... +4.3 | CAPE... 0.0 LI... +4.2
CINH... 0.0 K Index... +9.7 | CINH... 0.0 K Index... +9.9
|
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 -61.4 -78.5 265 42 21 1.9 1.1 | -61.3 -78.3 255 49 25 2.7 1.5
45000 -58.7 -73.7 265 44 23 -1.6 -0.9 | -57.2 -71.0 260 58 30 -1.3 -0.7
40000 -62.5 -80.5 275 38 20 -2.6 -1.4 | -63.1 -81.6 260 57 29 -4.0 -2.2
38000 -60.0 -76.0 270 37 19 8.1 4.5 | -61.3 -78.3 260 57 29 8.3 4.6
36000 -55.2 -67.4 270 37 19 8.1 4.4 | -56.3 -69.3 265 58 30 8.3 4.6
34000 -50.1 -58.2 270 36 19 8.9 4.9 | -51.3 -60.3 265 58 30 8.4 4.6
32000 -44.1 -47.4 270 36 19 8.9 4.9 | -46.3 -51.3 270 55 28 8.4 4.6
30000 -39.0 -38.2 275 35 18 8.1 4.4 | -40.7 -41.3 275 50 26 8.1 4.5
29000 -36.5 -33.7 275 33 17 8.1 4.4 | -38.3 -36.9 275 48 25 8.1 4.5
28000 -34.1 -29.4 270 31 16 8.1 4.4 | -35.8 -32.4 275 46 23 8.1 4.5
27000 -31.8 -25.2 275 29 15 6.9 3.8 | -33.4 -28.1 275 43 22 7.4 4.1
26000 -29.7 -21.5 275 26 14 7.0 3.9 | -31.3 -24.3 275 40 21 7.3 4.0
25000 -27.6 -17.7 280 24 12 7.1 3.9 | -29.1 -20.4 275 38 19 7.3 4.0
24000 -25.5 -13.9 285 22 11 7.5 4.1 | -26.9 -16.4 275 35 18 7.4 4.1
23000 -23.2 -9.8 290 21 11 7.7 4.2 | -24.7 -12.5 275 33 17 7.6 4.2
22000 -20.9 -5.6 295 20 10 7.7 4.2 | -22.4 -8.3 275 32 16 7.6 4.2
21000 -18.6 -1.5 300 19 10 8.0 4.4 | -20.1 -4.2 280 30 16 8.2 4.5
20000 -16.2 2.8 300 19 10 8.0 4.4 | -17.7 0.1 280 29 15 8.3 4.6
19500 -15.1 4.8 300 19 10 8.0 4.4 | -16.4 2.5 285 28 14 8.3 4.6
19000 -13.9 7.0 305 19 10 8.0 4.4 | -15.2 4.6 285 27 14 8.3 4.6
18500 -12.7 9.1 305 19 10 7.8 4.3 | -13.9 7.0 285 26 13 8.0 4.4
18000 -11.5 11.3 305 18 9 7.6 4.2 | -12.8 9.0 285 25 13 7.7 4.2
17500 -10.4 13.3 305 18 9 7.6 4.2 | -11.7 10.9 290 23 12 7.8 4.3
17000 -9.3 15.3 305 17 9 7.3 4.0 | -10.6 12.9 290 21 11 6.5 3.6
16500 -8.2 17.2 305 17 9 7.4 4.1 | -9.6 14.7 290 19 10 6.7 3.7
16000 -6.6 20.1 310 16 8 6.9 3.8 | -8.1 17.4 285 15 8 6.6 3.6
15500 -5.6 21.9 310 15 8 6.9 3.8 | -7.2 19.0 285 11 6 6.6 3.6
15000 -4.6 23.7 315 14 7 6.9 3.8 | -6.2 20.8 280 8 4 6.7 3.7
14500 -3.6 25.5 315 14 7 7.0 3.8 | -5.2 22.6 270 6 3 6.7 3.7
14000 -2.5 27.5 320 13 7 6.7 3.7 | -4.2 24.4 255 4 2 6.8 3.8
13500 -1.6 29.1 325 12 6 6.6 3.6 | -3.2 26.2 230 3 1 6.9 3.8
13000 -0.6 30.9 330 12 6 6.8 3.7 | -2.2 28.0 195 3 1 7.0 3.8
12500 0.5 32.9 330 11 6 7.0 3.8 | -1.1 30.0 175 3 1 7.1 3.9
12000 1.5 34.7 335 10 5 6.9 3.8 | -0.1 31.8 160 3 2 6.9 3.8
11500 2.5 36.5 335 10 5 6.8 3.7 | 0.9 33.6 145 3 1 6.6 3.6
11000 3.5 38.3 330 10 5 6.6 3.6 | 1.9 35.4 125 2 1 6.8 3.7
10500 4.5 40.1 330 9 4 6.1 3.3 | 3.0 37.4 070 2 1 7.3 4.0
10250 4.9 40.8 330 8 4 6.0 3.3 | 3.6 38.5 040 2 1 8.3 4.5
10000 5.4 41.7 330 8 4 6.9 3.8 | 4.3 39.7 020 3 2 10.2 5.6
9750 5.9 42.6 325 8 4 8.0 4.4 | 5.1 41.2 355 4 2 10.3 5.7
9500 6.5 43.7 325 9 5 8.0 4.4 | 5.9 42.6 340 6 3 9.8 5.4
9250 7.1 44.8 325 10 5 7.8 4.3 | 6.6 43.9 330 8 4 10.6 5.8
9000 7.7 45.9 325 10 5 8.5 4.7 | 7.4 45.3 325 10 5 8.0 4.4
8750 8.4 47.1 325 11 6 9.4 5.1 | 7.8 46.0 320 13 7 5.3 2.9
8500 9.1 48.4 325 11 6 9.2 5.1 | 8.3 46.9 310 17 9 5.6 3.1
8250 9.8 49.6 330 12 6 9.5 5.2 | 8.7 47.7 310 21 11 6.1 3.4
8000 10.5 50.9 325 13 7 9.7 5.3 | 9.0 48.2 305 25 13 -2.2 -1.2
7750 11.2 52.2 320 16 8 7.9 4.3 | 8.4 47.1 300 28 14 -7.1 -3.9
7500 11.8 53.2 315 18 9 7.4 4.1 | 8.1 46.6 300 28 15 -4.8 -2.7
7250 12.3 54.1 315 20 11 5.2 2.9 | 7.7 45.9 295 28 15 -3.0 -1.7
7000 12.5 54.5 310 23 12 0.2 0.1 | 7.7 45.9 295 26 14 3.6 2.0
6750 12.3 54.1 300 25 13 -4.5 -2.4 | 8.1 46.6 300 23 12 6.0 3.3
6500 12.0 53.6 295 27 14 -3.0 -1.7 | 8.5 47.3 300 20 10 6.2 3.4
6250 11.5 52.7 290 28 15 -15.9 -8.7 | 9.0 48.2 305 17 9 4.6 2.5
6000 9.6 49.3 285 23 12 -27.9 -15.3 | 9.2 48.6 305 13 7 3.0 1.7
5750 7.7 45.9 275 17 9 -26.8 -14.7 | 9.4 48.9 310 8 4 3.4 1.9
5500 5.2 41.4 250 11 5 -37.7 -20.7 | 9.7 49.5 315 5 2 4.8 2.6
12/08/2024 at 1400 MST | 12/08/2024 at 1700 MST
|
CAPE... 0.0 LI... +3.7 | CAPE... 0.0 LI... +6.5
CINH... 0.0 K Index... +8.9 | CINH... 0.0 K Index... -17.7
|
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 -60.0 -76.0 255 54 28 2.6 1.4 | -58.6 -73.5 255 50 26 1.0 0.6
45000 -56.1 -69.0 265 71 37 3.4 1.9 | -57.0 -70.6 270 87 45 1.2 0.7
40000 -62.5 -80.5 260 74 38 -4.5 -2.4 | -62.8 -81.0 265 80 41 -4.0 -2.2
38000 -61.5 -78.7 260 74 38 7.9 4.3 | -62.2 -80.0 260 76 39 7.0 3.8
36000 -56.8 -70.2 260 74 38 7.9 4.3 | -58.0 -72.4 260 74 38 7.0 3.8
34000 -52.0 -61.6 265 73 37 7.7 4.2 | -53.8 -64.8 260 71 36 8.1 4.5
32000 -47.4 -53.3 265 66 34 7.7 4.2 | -49.0 -56.2 265 63 33 8.0 4.4
30000 -42.3 -44.1 270 59 30 7.2 3.9 | -44.2 -47.6 265 56 29 8.3 4.6
29000 -40.2 -40.4 270 55 28 7.1 3.9 | -41.7 -43.1 265 55 28 8.3 4.6
28000 -38.0 -36.4 275 51 26 7.1 3.9 | -39.2 -38.6 265 53 28 8.3 4.6
27000 -35.9 -32.6 275 47 24 7.8 4.3 | -36.1 -33.0 270 52 27 8.3 4.5
26000 -33.4 -28.1 275 45 23 8.2 4.5 | -33.6 -28.5 270 51 26 8.3 4.5
25000 -31.0 -23.8 275 44 22 8.2 4.5 | -31.2 -24.2 270 51 26 8.3 4.5
24000 -28.5 -19.3 275 42 22 8.1 4.5 | -28.7 -19.7 270 50 26 8.2 4.5
23000 -26.1 -15.0 275 41 21 8.1 4.4 | -26.3 -15.3 275 49 25 7.9 4.4
22000 -23.7 -10.7 275 40 20 8.1 4.4 | -23.9 -11.0 275 48 25 7.9 4.4
21000 -21.3 -6.3 275 38 20 7.7 4.2 | -21.6 -6.9 275 46 24 7.7 4.2
20000 -19.0 -2.2 275 36 19 7.5 4.1 | -19.3 -2.7 275 44 23 7.5 4.1
19500 -17.9 -0.2 270 35 18 7.5 4.1 | -18.2 -0.8 280 43 22 7.5 4.1
19000 -16.8 1.8 270 34 17 7.5 4.1 | -17.1 1.2 280 42 22 7.5 4.1
18500 -15.7 3.7 270 33 17 7.4 4.1 | -15.9 3.4 280 41 21 7.5 4.1
18000 -14.7 5.5 270 31 16 7.1 3.9 | -14.8 5.4 280 39 20 7.3 4.0
17500 -13.6 7.5 270 30 15 7.1 3.9 | -13.7 7.3 280 37 19 7.3 4.0
17000 -12.6 9.3 270 28 14 7.2 3.9 | -12.6 9.3 285 36 18 7.2 4.0
16500 -11.5 11.3 270 26 14 7.2 4.0 | -11.6 11.1 285 35 18 7.2 3.9
16000 -10.5 13.1 265 25 13 7.4 4.0 | -10.5 13.1 285 33 17 7.0 3.8
15500 -8.8 16.2 265 22 11 7.5 4.1 | -9.5 14.9 285 32 16 6.7 3.7
15000 -7.7 18.1 265 20 10 7.7 4.2 | -8.5 16.7 285 30 16 6.7 3.7
14500 -6.6 20.1 265 19 10 7.7 4.2 | -7.5 18.5 290 29 15 6.3 3.5
14000 -5.4 22.3 265 17 9 7.8 4.3 | -6.1 21.0 290 28 14 6.3 3.5
13500 -4.3 24.3 265 16 8 7.9 4.3 | -5.1 22.8 290 27 14 6.3 3.5
13000 -3.1 26.4 265 15 8 8.1 4.4 | -4.2 24.4 290 27 14 6.1 3.3
12500 -1.8 28.8 265 15 8 8.6 4.7 | -3.4 25.9 290 27 14 5.1 2.8
12000 -0.5 31.1 270 16 8 8.3 4.6 | -2.7 27.1 285 27 14 5.1 2.8
11500 0.6 33.1 270 17 9 7.2 3.9 | -2.1 28.2 280 26 14 3.8 2.1
11000 1.7 35.1 275 18 9 6.8 3.7 | -1.5 29.3 275 25 13 4.1 2.3
10500 2.4 36.3 275 20 10 4.5 2.5 | -0.9 30.4 270 24 12 4.7 2.6
10250 2.8 37.0 280 21 11 4.7 2.6 | -0.6 30.9 265 23 12 5.2 2.9
10000 3.1 37.6 280 22 12 4.0 2.2 | -0.1 31.8 260 22 11 8.0 4.4
9750 3.4 38.1 280 23 12 3.1 1.7 | 0.5 32.9 255 20 10 8.5 4.7
9500 3.6 38.5 285 23 12 2.9 1.6 | 1.0 33.8 255 19 10 7.4 4.1
9250 3.8 38.8 285 23 12 3.0 1.6 | 1.6 34.9 255 18 9 7.9 4.3
9000 4.0 39.2 285 23 12 2.9 1.6 | 2.2 36.0 250 17 9 7.1 3.9
8750 4.2 39.6 290 23 12 2.2 1.2 | 2.6 36.7 250 15 8 6.2 3.4
8500 4.3 39.7 290 22 11 1.8 1.0 | 3.1 37.6 250 13 7 6.3 3.4
8250 4.5 40.1 290 22 11 1.5 0.8 | 3.5 38.3 255 12 6 6.3 3.5
8000 4.6 40.3 290 21 11 4.6 2.5 | 4.0 39.2 255 11 6 6.2 3.4
7750 5.1 41.2 295 19 10 6.4 3.5 | 4.4 39.9 265 9 5 4.9 2.7
7500 5.5 41.9 300 18 9 4.8 2.7 | 4.8 40.6 270 8 4 4.0 2.2
7250 5.9 42.6 305 16 8 5.6 3.1 | 5.1 41.2 280 7 3 4.8 2.6
7000 6.3 43.3 310 14 7 6.6 3.6 | 5.5 41.9 285 5 3 6.3 3.5
6750 6.8 44.2 315 12 6 6.1 3.3 | 6.0 42.8 295 4 2 6.7 3.7
6500 7.2 45.0 325 9 5 4.7 2.6 | 6.5 43.7 300 2 1 6.2 3.4
6250 7.6 45.7 340 7 3 6.7 3.7 | 6.9 44.4 000 0 0 7.2 3.9
6000 8.2 46.8 350 5 2 8.2 4.5 | 7.5 45.5 135 1 0 8.0 4.4
5750 8.7 47.7 010 3 2 8.2 4.5 | 8.1 46.6 140 2 1 7.5 4.1
5500 9.4 48.9 030 3 1 10.8 5.9 | 8.4 47.1 140 3 1 0.8 0.4
________________________________________________________________________________
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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