Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
097
UXUS97 KBOU 220123
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1822 MST Thursday, November 21, 2024
This forecast is for Friday, November 22, 2024:
If the trigger temperature of 68.2 F/20.1 C is reached...then
Thermal Soaring Index....................... Poor
Maximum rate of lift........................ 23 ft/min (0.1 m/s)
Maximum height of thermals.................. 7012 ft MSL (1721 ft AGL)
Forecast maximum temperature................... 61.0 F/16.6 C
Time of trigger temperature.................... None
Time of overdevelopment........................ None
Middle/high clouds during soaring window....... Overcast thin high
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 6211 ft MSL (921 ft AGL)
Thermal soaring outlook for Saturday 11/23..... 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)................ Neither
Potential height of wave....................... 45610 ft MSL (40319 ft AGL)
Wave soaring outlook for Saturday 11/23........ Poor
Remarks...
Sunrise/Sunset.................... 06:52:53 / 16:38:43 MST
Total possible sunshine........... 9 hr 45 min 50 sec (585 min 50 sec)
Altitude of sun at 11:45:48 MST... 29.79 degrees
Upper air data from numerical model forecast valid on 11/22/2024 at 0500 MST
Freezing level.................. 13095 ft MSL (7804 ft AGL)
Convective condensation level... 23061 ft MSL (17770 ft AGL)
Lifted condensation level....... 17520 ft MSL (12229 ft AGL)
Lifted index.................... +10.4
K index......................... -4.5
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 -65.4 -85.7 290 54 28 0.8 0.5 M M M M M
45000 -64.1 -83.4 280 65 34 1.4 0.8 M M M M M
40000 -62.0 -79.6 275 56 29 1.0 0.6 M M M M M
38000 -58.5 -73.3 280 53 27 7.0 3.8 M M M M M
36000 -54.3 -65.7 280 50 26 7.0 3.8 M M M M M
34000 -49.7 -57.5 285 46 24 8.3 4.6 M M M M M
32000 -44.7 -48.5 285 42 22 8.3 4.6 M M M M M
30000 -39.8 -39.6 285 38 20 7.9 4.3 36.3 97.3 15.2 M M
29000 -36.9 -34.4 285 36 18 7.9 4.3 35.3 95.6 14.7 M M
28000 -34.5 -30.1 285 33 17 7.9 4.3 34.7 94.5 14.4 M M
27000 -32.1 -25.8 280 32 17 8.1 4.5 34.1 93.3 14.0 M M
26000 -29.7 -21.5 280 31 16 8.1 4.5 33.4 92.1 13.6 M M
25000 -27.2 -17.0 280 30 16 8.1 4.5 32.9 91.1 13.4 M M
24000 -24.9 -12.8 275 29 15 7.8 4.3 32.2 90.0 13.0 M M
23000 -22.5 -8.5 275 28 14 7.8 4.3 31.5 88.7 12.5 M M
22000 -20.2 -4.4 275 26 14 7.8 4.3 30.8 87.5 12.2 M M
21000 -17.9 -0.2 280 25 13 7.6 4.2 30.1 86.2 11.7 M M
20000 -15.6 3.9 280 23 12 7.6 4.2 29.3 84.8 11.1 M M
19500 -14.4 6.1 280 23 12 7.6 4.2 29.0 84.2 10.9 M M
19000 -13.3 8.1 280 22 11 7.6 4.2 28.7 83.6 10.7 M M
18500 -12.2 10.0 280 21 11 7.6 4.1 28.3 82.9 10.4 M M
18000 -11.1 12.0 280 20 11 7.6 4.1 27.9 82.2 10.1 M M
17500 -9.9 14.2 285 20 10 7.6 4.2 27.5 81.6 9.8 M M
17000 -8.8 16.2 285 19 10 7.6 4.2 27.2 80.9 9.6 M M
16500 -7.7 18.1 285 19 10 7.6 4.1 26.8 80.3 9.3 M M
16000 -6.5 20.3 285 18 9 7.5 4.1 26.4 79.6 9.0 M M
15500 -5.4 22.3 290 18 9 7.5 4.1 26.1 78.9 8.7 M M
15000 -3.8 25.2 290 17 9 7.2 4.0 25.4 77.8 8.2 M M
14500 -2.7 27.1 290 16 8 7.1 3.9 25.0 77.0 7.9 M M
14000 -1.7 28.9 290 16 8 7.0 3.8 24.6 76.2 7.5 M M
13500 -0.6 30.9 290 15 8 6.9 3.8 24.1 75.4 7.1 M M
13000 0.4 32.7 285 14 7 6.8 3.7 23.6 74.5 6.7 M M
12500 1.4 34.5 285 13 7 6.8 3.7 23.2 73.7 6.3 M M
12000 2.4 36.3 285 12 6 7.1 3.9 22.7 72.9 5.9 M M
11500 3.5 38.3 280 11 6 7.0 3.9 22.3 72.1 5.6 M M
11000 4.6 40.3 280 10 5 7.2 3.9 21.9 71.3 5.2 M M
10500 5.7 42.3 275 9 4 7.1 3.9 21.4 70.6 4.8 M M
10250 6.1 43.0 270 8 4 3.6 2.0 21.2 70.1 4.6 M M
10000 6.3 43.3 270 8 4 5.5 3.0 20.6 69.1 4.1 M M
9750 7.0 44.6 270 7 4 9.7 5.3 20.5 69.0 4.0 M M
9500 7.6 45.7 265 7 3 8.2 4.5 20.5 68.8 4.0 M M
9250 8.2 46.8 260 6 3 4.7 2.6 20.2 68.4 3.8 M M
9000 8.4 47.1 260 6 3 4.1 2.2 19.7 67.5 3.3 M M
8750 8.9 48.0 255 6 3 7.2 3.9 19.5 67.0 3.0 M M
8500 9.4 48.9 245 5 3 6.1 3.3 19.2 66.6 2.8 M M
8250 9.7 49.5 245 5 3 3.9 2.1 18.9 65.9 2.4 M M
8000 10.0 50.0 240 5 2 3.4 1.8 18.4 65.1 2.0 M M
7750 10.3 50.5 240 5 2 5.2 2.8 17.9 64.3 1.5 M M
7500 10.7 51.3 240 4 2 3.7 2.0 17.6 63.7 1.2 M M
7250 10.8 51.4 245 4 2 1.3 0.7 17.0 62.6 0.6 M M
7000 10.9 51.6 245 4 2 2.3 1.2 16.4 61.5 -0.0 123 0.6
6750 11.0 51.8 250 4 2 -0.1 -0.0 15.8 60.4 -0.6 112 0.6
6500 10.8 51.4 250 4 2 -4.3 -2.3 14.8 58.7 -1.5 111 0.6
6250 10.4 50.7 250 5 2 -6.3 -3.4 13.7 56.6 -2.7 116 0.6
6000 10.0 50.0 250 5 3 -3.0 -1.7 12.5 54.6 -3.9 121 0.6
5750 9.3 48.7 245 5 3 -27.4 -15.0 11.1 51.9 -5.4 137 0.7
5500 5.3 41.5 220 5 2 -73.0 -40.0 6.4 43.6 -10.1 249 1.3
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
11/22/2024 at 0800 MST | 11/22/2024 at 1100 MST
|
CAPE... 0.0 LI... +6.1 | CAPE... 0.0 LI... +5.9
CINH... -0.2 K Index... -5.4 | CINH... 0.0 K Index... -7.5
|
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 -65.8 -86.4 290 50 26 0.7 0.4 | -66.2 -87.2 285 51 26 0.9 0.5
45000 -64.7 -84.5 285 62 32 1.5 0.8 | -64.7 -84.5 285 64 33 1.8 1.0
40000 -62.5 -80.5 280 48 25 1.1 0.6 | -62.1 -79.8 285 47 24 1.4 0.7
38000 -58.9 -74.0 280 46 24 7.1 3.9 | -58.6 -73.5 285 43 22 6.8 3.7
36000 -54.7 -66.5 285 44 23 7.1 3.9 | -54.6 -66.3 290 39 20 6.8 3.7
34000 -50.0 -58.0 285 42 21 8.4 4.6 | -50.1 -58.2 290 36 19 8.2 4.5
32000 -45.0 -49.0 285 38 20 8.4 4.6 | -45.2 -49.4 285 35 18 8.2 4.5
30000 -39.5 -39.1 285 35 18 8.1 4.4 | -40.2 -40.4 285 33 17 8.4 4.6
29000 -37.1 -34.8 285 34 17 8.1 4.4 | -37.1 -34.8 280 33 17 8.4 4.6
28000 -34.6 -30.3 285 32 17 8.1 4.5 | -34.5 -30.1 280 33 17 8.5 4.7
27000 -32.2 -26.0 280 32 17 8.1 4.4 | -32.1 -25.8 280 33 17 7.9 4.3
26000 -29.8 -21.6 280 32 17 8.1 4.4 | -29.8 -21.6 280 33 17 7.9 4.3
25000 -27.4 -17.3 280 32 17 8.1 4.4 | -27.4 -17.3 280 34 17 7.9 4.4
24000 -25.0 -13.0 280 32 16 8.0 4.4 | -25.0 -13.0 280 34 17 8.2 4.5
23000 -22.7 -8.9 280 31 16 8.0 4.4 | -22.5 -8.5 280 33 17 8.2 4.5
22000 -20.3 -4.5 285 30 15 8.0 4.4 | -20.1 -4.2 280 32 16 8.2 4.5
21000 -18.0 -0.4 285 28 15 7.8 4.3 | -17.8 -0.0 280 30 16 7.6 4.2
20000 -15.6 3.9 285 26 14 7.8 4.3 | -15.5 4.1 280 29 15 7.6 4.1
19500 -14.5 5.9 285 26 13 7.8 4.3 | -14.4 6.1 280 28 14 7.6 4.2
19000 -13.3 8.1 285 25 13 7.6 4.2 | -13.3 8.1 280 27 14 7.5 4.1
18500 -12.2 10.0 285 24 12 7.0 3.8 | -12.2 10.0 280 26 13 7.4 4.1
18000 -11.2 11.8 285 22 12 7.0 3.8 | -11.1 12.0 280 25 13 7.4 4.1
17500 -10.1 13.8 285 21 11 7.0 3.9 | -10.0 14.0 285 24 12 7.2 4.0
17000 -9.1 15.6 285 20 10 7.0 3.9 | -8.9 16.0 285 23 12 7.2 3.9
16500 -8.1 17.4 285 19 10 7.0 3.9 | -7.8 18.0 285 22 11 7.1 3.9
16000 -6.5 20.3 285 17 9 7.0 3.8 | -6.8 19.8 285 21 11 7.0 3.8
15500 -5.4 22.3 285 16 8 7.0 3.8 | -5.2 22.6 285 20 10 7.0 3.8
15000 -4.4 24.1 285 15 8 7.0 3.8 | -4.2 24.4 285 19 10 7.0 3.8
14500 -3.4 25.9 285 14 7 7.0 3.8 | -3.1 26.4 280 18 9 7.0 3.8
14000 -2.3 27.9 280 13 7 7.0 3.8 | -2.1 28.2 280 17 9 7.0 3.8
13500 -1.3 29.7 280 13 7 7.0 3.8 | -1.1 30.0 280 16 8 7.0 3.8
13000 -0.2 31.6 280 12 6 7.0 3.8 | -0.0 32.0 280 16 8 7.0 3.9
12500 0.8 33.4 275 11 6 7.0 3.8 | 1.0 33.8 280 15 8 7.0 3.9
12000 1.9 35.4 275 10 5 7.1 3.9 | 2.1 35.8 275 14 7 7.1 3.9
11500 2.9 37.2 270 9 5 7.1 3.9 | 3.2 37.8 275 13 7 7.1 3.9
11000 4.0 39.2 270 8 4 7.0 3.8 | 4.2 39.6 275 12 6 7.3 4.0
10500 5.0 41.0 265 7 4 6.8 3.8 | 5.3 41.5 270 10 5 7.2 3.9
10250 5.5 41.9 260 7 4 3.2 1.7 | 5.7 42.3 270 10 5 3.5 1.9
10000 5.7 42.3 255 8 4 5.6 3.1 | 6.0 42.8 270 10 5 5.8 3.2
9750 6.3 43.3 255 7 4 10.1 5.5 | 6.7 44.1 265 9 5 10.1 5.5
9500 7.0 44.6 255 6 3 8.4 4.6 | 7.3 45.1 265 8 4 8.7 4.8
9250 7.6 45.7 250 6 3 4.9 2.7 | 7.9 46.2 265 7 4 5.7 3.1
9000 7.8 46.0 245 6 3 4.8 2.6 | 8.3 46.9 255 7 4 5.4 3.0
8750 8.4 47.1 240 5 3 8.1 4.5 | 8.8 47.8 255 7 3 8.1 4.4
8500 8.9 48.0 235 5 2 6.9 3.8 | 9.4 48.9 255 6 3 7.0 3.9
8250 9.4 48.9 230 5 2 4.8 2.6 | 9.8 49.6 255 6 3 5.5 3.0
8000 9.7 49.5 225 5 2 4.4 2.4 | 10.2 50.4 255 5 3 4.9 2.7
7750 10.1 50.2 220 4 2 5.5 3.0 | 10.6 51.1 250 5 3 5.4 2.9
7500 10.5 50.9 225 4 2 4.1 2.3 | 11.0 51.8 245 5 2 4.0 2.2
7250 10.6 51.1 220 4 2 2.2 1.2 | 11.2 52.2 245 5 2 2.6 1.4
7000 10.8 51.4 220 4 2 3.1 1.7 | 11.4 52.5 245 4 2 3.0 1.6
6750 11.0 51.8 220 4 2 1.3 0.7 | 11.6 52.9 240 4 2 2.7 1.5
6500 11.0 51.8 225 4 2 -2.4 -1.3 | 11.7 53.1 225 4 2 0.5 0.3
6250 10.7 51.3 225 5 2 -3.9 -2.1 | 11.7 53.1 220 4 2 -0.8 -0.5
6000 10.4 50.7 230 5 2 -2.3 -1.3 | 11.6 52.9 210 4 2 -0.6 -0.3
5750 9.7 49.5 225 5 3 -26.1 -14.3 | 11.5 52.7 205 4 2 0.4 0.2
5500 6.0 42.8 210 5 3 -67.2 -36.8 | 11.5 52.7 195 4 2 2.5 1.4
11/22/2024 at 1400 MST | 11/22/2024 at 1700 MST
|
CAPE... 0.0 LI... +4.9 | CAPE... 0.0 LI... +5.1
CINH... -0.2 K Index... -8.6 | CINH... 0.0 K Index... -6.5
|
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 -66.5 -87.7 280 52 27 1.3 0.7 | -66.1 -87.0 280 54 28 0.9 0.5
45000 -64.5 -84.1 285 67 34 1.7 0.9 | -64.6 -84.3 285 74 38 1.1 0.6
40000 -62.0 -79.6 285 53 27 1.8 1.0 | -63.0 -81.4 290 60 31 1.2 0.7
38000 -58.9 -74.0 285 48 25 6.6 3.6 | -59.5 -75.1 290 56 29 7.7 4.2
36000 -54.9 -66.8 285 43 22 6.6 3.6 | -54.9 -66.8 285 52 27 7.7 4.2
34000 -50.0 -58.0 280 39 20 8.1 4.4 | -49.6 -57.3 280 48 24 7.9 4.3
32000 -45.2 -49.4 275 36 19 8.1 4.4 | -44.9 -48.8 280 43 22 7.8 4.3
30000 -40.1 -40.2 275 35 18 8.7 4.8 | -40.0 -40.0 275 39 20 8.3 4.6
29000 -37.5 -35.5 275 35 18 8.7 4.8 | -37.5 -35.5 275 37 19 8.4 4.6
28000 -34.9 -30.8 280 35 18 8.7 4.8 | -35.0 -31.0 275 35 18 8.3 4.6
27000 -32.4 -26.3 280 34 18 8.0 4.4 | -32.6 -26.7 275 34 17 7.6 4.2
26000 -30.0 -22.0 285 34 17 8.0 4.4 | -30.4 -22.7 275 32 17 7.6 4.2
25000 -27.6 -17.7 285 34 17 8.0 4.4 | -28.1 -18.6 280 31 16 7.6 4.2
24000 -25.2 -13.4 290 33 17 8.3 4.5 | -25.7 -14.3 280 30 15 8.8 4.9
23000 -22.7 -8.9 290 31 16 8.2 4.5 | -23.1 -9.6 285 28 15 8.8 4.8
22000 -20.2 -4.4 290 30 15 8.2 4.5 | -20.4 -4.7 285 27 14 8.7 4.8
21000 -17.8 -0.0 290 29 15 7.6 4.2 | -17.9 -0.2 290 25 13 7.9 4.4
20000 -15.6 3.9 290 27 14 7.6 4.2 | -15.5 4.1 290 24 13 7.9 4.4
19500 -14.4 6.1 290 27 14 7.6 4.2 | -14.3 6.3 290 24 12 7.9 4.4
19000 -13.3 8.1 290 26 13 7.6 4.1 | -13.1 8.4 290 23 12 7.9 4.4
18500 -12.2 10.0 290 25 13 7.3 4.0 | -12.0 10.4 290 23 12 7.6 4.2
18000 -11.1 12.0 290 25 13 7.3 4.0 | -10.8 12.6 295 23 12 7.7 4.2
17500 -10.0 14.0 290 24 12 7.5 4.1 | -9.7 14.5 295 23 12 7.7 4.2
17000 -8.3 17.1 285 24 12 7.6 4.1 | -8.0 17.6 295 23 12 7.8 4.3
16500 -7.2 19.0 285 24 12 7.4 4.1 | -6.8 19.8 295 23 12 7.6 4.2
16000 -6.1 21.0 285 23 12 7.4 4.0 | -5.7 21.7 295 23 12 7.5 4.1
15500 -5.0 23.0 285 23 12 7.4 4.1 | -4.6 23.7 295 23 12 7.4 4.0
15000 -3.8 25.2 285 22 12 7.5 4.1 | -3.5 25.7 295 23 12 7.1 3.9
14500 -2.7 27.1 285 22 11 7.5 4.1 | -2.5 27.5 295 23 12 7.1 3.9
14000 -1.6 29.1 285 21 11 7.3 4.0 | -1.4 29.5 295 22 12 7.0 3.8
13500 -0.5 31.1 290 20 11 7.3 4.0 | -0.3 31.5 295 22 11 7.0 3.8
13000 0.6 33.1 290 19 10 7.7 4.2 | 0.7 33.3 290 21 11 7.2 3.9
12500 1.8 35.2 290 18 9 7.6 4.2 | 1.8 35.2 290 20 10 7.1 3.9
12000 2.9 37.2 290 17 9 7.5 4.1 | 2.9 37.2 290 19 10 7.4 4.0
11500 4.0 39.2 290 16 8 7.5 4.1 | 4.0 39.2 290 18 9 7.4 4.1
11000 5.2 41.4 290 15 8 7.6 4.2 | 5.1 41.2 285 17 9 6.6 3.6
10500 6.3 43.3 290 15 7 8.5 4.7 | 6.0 42.8 285 16 8 7.4 4.1
10250 6.9 44.4 290 14 7 4.1 2.2 | 6.5 43.7 285 15 8 3.4 1.9
10000 7.0 44.6 290 14 7 4.5 2.5 | 6.7 44.1 280 14 7 4.0 2.2
9750 7.7 45.9 290 14 7 9.1 5.0 | 7.2 45.0 280 13 7 8.3 4.5
9500 8.3 46.9 290 13 7 8.3 4.6 | 7.8 46.0 280 12 6 7.9 4.3
9250 8.8 47.8 290 13 7 5.2 2.9 | 8.3 46.9 275 11 6 5.2 2.9
9000 9.1 48.4 290 12 6 4.2 2.3 | 8.6 47.5 275 10 5 4.4 2.4
8750 9.6 49.3 295 11 6 7.2 3.9 | 9.1 48.4 275 9 5 7.4 4.1
8500 10.1 50.2 295 11 5 6.5 3.6 | 9.6 49.3 275 8 4 6.9 3.8
8250 10.5 50.9 295 10 5 4.7 2.6 | 10.1 50.2 270 8 4 5.1 2.8
8000 10.8 51.4 300 9 4 3.9 2.2 | 10.4 50.7 270 7 3 3.9 2.1
7750 11.1 52.0 300 7 4 6.0 3.3 | 10.7 51.3 270 6 3 5.2 2.9
7500 11.6 52.9 300 6 3 5.1 2.8 | 11.1 52.0 275 5 3 4.6 2.5
7250 11.9 53.4 305 5 3 2.7 1.5 | 11.4 52.5 275 5 2 3.0 1.6
7000 12.0 53.6 305 4 2 2.6 1.4 | 11.6 52.9 275 4 2 2.6 1.4
6750 12.2 54.0 310 3 2 2.8 1.5 | 11.8 53.2 280 3 2 3.0 1.6
6500 12.4 54.3 315 2 1 1.6 0.9 | 12.0 53.6 285 3 1 2.8 1.5
6250 12.4 54.3 310 1 0 0.7 0.4 | 12.1 53.8 275 2 1 1.8 1.0
6000 12.5 54.5 000 0 0 0.9 0.5 | 12.3 54.1 265 2 1 3.9 2.1
5750 12.5 54.5 145 1 1 1.7 0.9 | 12.4 54.3 245 1 1 -3.0 -1.7
5500 12.6 54.7 140 2 1 3.6 2.0 | 11.3 52.3 220 1 1 -24.6 -13.5
________________________________________________________________________________
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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