Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
755
UXUS97 KBOU 310023
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1722 MST Thursday, January 30, 2025
This forecast is for Friday, January 31, 2025:
If the trigger temperature of 53.8 F/12.1 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 424 ft/min (2.2 m/s)
Maximum height of thermals.................. 10944 ft MSL (5638 ft AGL)
Forecast maximum temperature................... 57.0 F/14.3 C
Time of trigger temperature.................... 1145 MST
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................. 8056 ft MSL (2750 ft AGL)
Thermal soaring outlook for Saturday 02/01..... Good
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....................... 34413 ft MSL (29107 ft AGL)
Wave soaring outlook for Saturday 02/01........ Good
Remarks...
Sunrise/Sunset.................... 07:07:50 / 17:18:09 MST
Total possible sunshine........... 10 hr 10 min 19 sec (610 min 19 sec)
Altitude of sun at 12:13:00 MST... 33.00 degrees
Upper air data from numerical model forecast valid on 01/31/2025 at 0500 MST
Freezing level.................. 5653 ft MSL (347 ft AGL)
Additional freezing level....... 9346 ft MSL (4040 ft AGL)
Convective condensation level... 23016 ft MSL (17710 ft AGL)
Lifted condensation level....... 18680 ft MSL (13374 ft AGL)
Lifted index.................... +9.0
K index......................... -18.1
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 -56.2 -69.2 270 27 14 2.5 1.4 M M M M M
45000 -52.4 -62.3 270 25 13 0.5 0.3 M M M M M
40000 -57.7 -71.9 345 23 12 -3.6 -2.0 M M M M M
38000 -58.5 -73.3 350 31 16 2.3 1.3 M M M M M
36000 -56.9 -70.4 350 39 20 2.3 1.2 M M M M M
34000 -54.8 -66.6 345 45 23 8.7 4.8 M M M M M
32000 -49.7 -57.5 345 44 22 8.5 4.6 M M M M M
30000 -44.7 -48.5 350 42 22 8.2 4.5 31.2 88.2 13.0 M M
29000 -42.2 -44.0 350 41 21 8.2 4.5 30.5 86.9 12.6 M M
28000 -39.8 -39.6 355 40 20 8.2 4.5 29.9 85.8 12.3 M M
27000 -37.3 -35.1 360 39 20 8.0 4.4 29.5 85.0 12.1 M M
26000 -35.0 -31.0 360 37 19 7.7 4.2 28.5 83.4 11.6 M M
25000 -32.7 -26.9 360 35 18 7.7 4.2 27.8 82.0 11.1 M M
24000 -30.4 -22.7 360 32 17 7.8 4.3 27.1 80.8 10.7 M M
23000 -27.9 -18.2 360 32 16 8.3 4.5 26.5 79.6 10.3 M M
22000 -25.4 -13.7 355 31 16 8.3 4.5 25.9 78.6 9.9 M M
21000 -23.0 -9.4 355 31 16 7.6 4.2 25.4 77.8 9.6 M M
20000 -20.8 -5.4 355 31 16 7.2 4.0 24.5 76.0 8.9 M M
19500 -19.7 -3.5 360 31 16 7.2 4.0 24.0 75.2 8.6 M M
19000 -18.7 -1.7 360 30 16 7.2 4.0 23.6 74.5 8.2 M M
18500 -17.1 1.2 360 30 15 7.1 3.9 23.0 73.4 7.8 M M
18000 -16.0 3.2 360 30 15 7.1 3.9 22.5 72.5 7.4 M M
17500 -14.9 5.2 005 29 15 7.2 3.9 22.1 71.7 7.0 M M
17000 -13.8 7.2 005 28 15 7.3 4.0 21.6 70.9 6.7 M M
16500 -12.7 9.1 360 28 14 7.3 4.0 21.2 70.2 6.4 M M
16000 -11.7 10.9 360 27 14 5.8 3.2 20.7 69.2 5.9 M M
15500 -10.8 12.6 360 26 13 6.0 3.3 20.0 68.0 5.4 M M
15000 -10.0 14.0 355 25 13 5.4 3.0 19.3 66.8 4.8 M M
14500 -9.2 15.4 350 24 12 5.4 2.9 18.6 65.5 4.2 M M
14000 -8.4 16.9 345 23 12 5.3 2.9 17.9 64.2 3.6 M M
13500 -7.5 18.5 340 23 12 5.3 2.9 17.2 62.9 2.9 M M
13000 -6.7 19.9 340 23 12 5.6 3.1 16.4 61.6 2.3 M M
12500 -5.9 21.4 340 23 12 5.9 3.2 15.8 60.4 1.7 M M
12000 -5.0 23.0 340 23 12 6.0 3.3 15.2 59.3 1.1 M M
11500 -4.1 24.6 340 23 12 6.1 3.4 14.6 58.3 0.6 M M
11000 -3.2 26.2 340 23 12 6.4 3.5 14.0 57.2 0.0 M M
10500 -2.2 28.0 345 23 12 6.9 3.8 13.5 56.3 -0.5 383 1.9
10250 -1.7 28.9 345 23 12 5.1 2.8 13.2 55.8 -0.7 361 1.8
10000 -1.4 29.5 345 23 12 4.6 2.5 12.8 55.0 -1.1 344 1.7
9750 -0.9 30.4 345 23 12 7.3 4.0 12.5 54.5 -1.4 323 1.6
9500 -0.4 31.3 345 22 11 8.0 4.4 12.4 54.2 -1.6 299 1.5
9250 0.2 32.4 345 21 11 7.1 3.9 12.2 54.0 -1.7 274 1.4
9000 0.7 33.3 345 20 10 5.6 3.1 11.9 53.5 -2.0 252 1.3
8750 1.1 34.0 345 18 9 6.2 3.4 11.6 52.9 -2.3 232 1.2
8500 1.6 34.9 345 16 8 6.9 3.8 11.4 52.5 -2.6 210 1.1
8250 2.1 35.8 345 15 7 6.7 3.7 11.1 52.1 -2.8 187 1.0
8000 2.6 36.7 340 13 7 6.8 3.7 10.9 51.6 -3.0 165 0.8
7750 3.1 37.6 340 11 6 7.1 3.9 10.7 51.2 -3.3 142 0.7
7500 3.7 38.7 335 9 5 7.6 4.2 10.5 50.9 -3.4 118 0.6
7250 4.3 39.7 330 9 4 9.4 5.2 10.4 50.7 -3.6 92 0.5
7000 5.1 41.2 325 8 4 9.4 5.2 10.4 50.7 -3.6 62 0.3
6750 5.8 42.4 320 8 4 12.5 6.9 10.4 50.8 -3.6 32 0.2
6500 6.4 43.5 320 9 4 -4.5 -2.5 10.3 50.6 -3.7 6 0.0
6250 5.0 41.0 300 9 5 -23.6 -12.9 8.2 46.7 -5.8 40 0.2
6000 3.4 38.1 285 11 6 -18.3 -10.0 5.9 42.6 -8.2 81 0.4
5750 1.8 35.2 275 13 7 -28.5 -15.6 3.6 38.4 -10.5 122 0.6
5500 -1.2 29.8 260 13 7 -50.9 -27.9 -0.2 31.6 -14.4 207 1.1
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
01/31/2025 at 0800 MST | 01/31/2025 at 1100 MST
|
CAPE... 0.0 LI... +7.5 | CAPE... 0.0 LI... +6.2
CINH... 0.0 K Index... -22.2 | CINH... 0.0 K Index... -23.9
|
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 -56.1 -69.0 275 25 13 2.3 1.3 | -56.8 -70.2 265 28 14 2.2 1.2
45000 -52.7 -62.9 285 29 15 -0.8 -0.4 | -53.4 -64.1 270 34 18 -0.4 -0.2
40000 -61.4 -78.5 330 33 17 -5.9 -3.2 | -61.7 -79.1 305 38 19 -5.4 -2.9
38000 -61.8 -79.2 335 37 19 6.0 3.3 | -61.3 -78.3 315 38 20 5.7 3.1
36000 -57.8 -72.0 335 37 19 5.9 3.3 | -57.9 -72.2 320 36 19 5.7 3.1
34000 -53.9 -65.0 340 39 20 8.0 4.4 | -54.2 -65.6 325 35 18 8.3 4.6
32000 -49.0 -56.2 340 41 21 8.1 4.4 | -49.2 -56.6 325 34 18 8.3 4.6
30000 -44.2 -47.6 345 42 22 8.0 4.4 | -43.5 -46.3 325 33 17 8.3 4.5
29000 -41.8 -43.2 345 40 20 8.0 4.4 | -41.1 -42.0 325 32 17 8.3 4.5
28000 -39.4 -38.9 340 37 19 8.0 4.4 | -38.6 -37.5 325 32 16 8.3 4.5
27000 -37.0 -34.6 340 35 18 8.1 4.4 | -36.1 -33.0 325 30 16 8.4 4.6
26000 -34.5 -30.1 340 31 16 8.2 4.5 | -33.6 -28.5 315 28 14 8.4 4.6
25000 -32.1 -25.8 340 26 14 8.2 4.5 | -31.1 -24.0 310 26 13 8.4 4.6
24000 -29.6 -21.3 335 22 11 8.0 4.4 | -28.7 -19.7 305 24 12 7.6 4.2
23000 -27.3 -17.1 335 23 12 7.7 4.2 | -26.5 -15.7 305 24 12 7.4 4.1
22000 -25.0 -13.0 335 25 13 7.7 4.3 | -24.2 -11.6 305 24 13 7.4 4.1
21000 -22.7 -8.9 335 26 13 7.4 4.1 | -22.0 -7.6 305 25 13 7.7 4.2
20000 -20.5 -4.9 335 26 13 7.4 4.0 | -19.7 -3.5 305 24 12 7.7 4.2
19500 -18.9 -2.0 340 26 13 7.4 4.0 | -18.6 -1.5 305 24 12 7.7 4.2
19000 -17.8 -0.0 340 26 13 7.3 4.0 | -17.4 0.7 305 24 12 7.7 4.2
18500 -16.6 2.1 340 26 13 7.5 4.1 | -16.3 2.7 305 24 12 7.1 3.9
18000 -15.5 4.1 340 25 13 7.5 4.1 | -15.3 4.5 305 23 12 7.0 3.8
17500 -14.3 6.3 340 25 13 7.2 3.9 | -14.2 6.4 305 22 12 7.2 3.9
17000 -13.3 8.1 340 24 12 7.0 3.8 | -13.1 8.4 305 22 11 7.8 4.3
16500 -12.2 10.0 340 23 12 7.0 3.8 | -11.9 10.6 305 21 11 7.8 4.3
16000 -11.2 11.8 340 22 11 7.0 3.9 | -10.1 13.8 305 21 11 8.1 4.4
15500 -10.1 13.8 340 20 10 7.1 3.9 | -8.9 16.0 305 20 10 8.0 4.4
15000 -9.1 15.6 340 19 10 6.1 3.3 | -7.8 18.0 305 20 10 7.2 4.0
14500 -8.2 17.2 340 19 10 6.2 3.4 | -6.7 19.9 305 19 10 7.4 4.0
14000 -7.3 18.9 335 19 10 5.7 3.1 | -5.6 21.9 305 19 10 6.6 3.6
13500 -6.5 20.3 335 18 10 5.6 3.1 | -4.6 23.7 300 18 9 6.7 3.7
13000 -5.7 21.7 330 18 9 5.3 2.9 | -3.7 25.3 300 17 9 5.7 3.1
12500 -4.9 23.2 330 18 9 5.2 2.8 | -2.9 26.8 295 16 8 5.7 3.1
12000 -4.2 24.4 330 17 9 5.3 2.9 | -2.0 28.4 290 15 8 5.6 3.1
11500 -3.3 26.1 330 16 8 5.4 3.0 | -1.2 29.8 285 14 7 5.7 3.1
11000 -2.5 27.5 330 14 7 5.5 3.0 | -0.4 31.3 280 13 7 4.4 2.4
10500 -1.7 28.9 330 13 6 5.8 3.2 | 0.2 32.4 270 12 6 4.6 2.5
10250 -1.3 29.7 335 12 6 4.4 2.4 | 0.5 32.9 265 12 6 2.2 1.2
10000 -1.0 30.2 335 11 6 4.5 2.5 | 0.6 33.1 265 12 6 2.7 1.5
9750 -0.5 31.1 335 11 5 6.5 3.6 | 1.0 33.8 255 11 6 5.5 3.0
9500 -0.1 31.8 340 10 5 6.4 3.5 | 1.3 34.3 250 11 5 4.6 2.5
9250 0.4 32.7 345 9 5 6.3 3.5 | 1.7 35.1 245 10 5 5.2 2.9
9000 0.9 33.6 350 8 4 6.5 3.6 | 2.1 35.8 240 10 5 5.5 3.0
8750 1.4 34.5 350 8 4 7.3 4.0 | 2.5 36.5 230 9 5 5.2 2.8
8500 2.0 35.6 355 7 3 7.6 4.2 | 2.9 37.2 225 9 5 5.0 2.8
8250 2.5 36.5 355 6 3 7.4 4.1 | 3.3 37.9 215 9 5 6.6 3.6
8000 3.1 37.6 350 4 2 7.3 4.0 | 3.8 38.8 210 9 5 7.8 4.3
7750 3.6 38.5 330 2 1 7.3 4.0 | 4.4 39.9 205 10 5 7.2 3.9
7500 4.2 39.6 295 2 1 7.7 4.2 | 4.9 40.8 200 10 5 7.8 4.3
7250 4.8 40.6 265 2 1 9.2 5.0 | 5.6 42.1 205 10 5 9.2 5.1
7000 5.5 41.9 260 3 2 8.6 4.7 | 6.3 43.3 215 9 5 9.2 5.1
6750 6.2 43.2 255 5 2 12.1 6.6 | 7.0 44.6 220 8 4 10.2 5.6
6500 6.8 44.2 270 7 3 -5.3 -2.9 | 7.5 45.5 240 8 4 0.2 0.1
6250 5.4 41.7 265 8 4 -22.1 -12.1 | 7.0 44.6 230 8 4 -8.1 -4.5
6000 4.0 39.2 260 10 5 -16.4 -9.0 | 6.5 43.7 225 8 4 -5.9 -3.2
5750 2.6 36.7 260 12 6 -22.1 -12.1 | 6.0 42.8 220 8 4 -5.7 -3.1
5500 0.3 32.5 250 12 6 -40.6 -22.3 | 5.4 41.7 215 9 5 -9.2 -5.0
01/31/2025 at 1400 MST | 01/31/2025 at 1700 MST
|
CAPE... 0.0 LI... +4.6 | CAPE... 0.0 LI... +4.3
CINH... 0.0 K Index... -14.3 | CINH... 0.0 K Index... -9.5
|
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 -57.2 -71.0 265 34 17 2.2 1.2 | -58.0 -72.4 270 36 19 1.1 0.6
45000 -53.9 -65.0 275 33 17 -0.1 -0.0 | -56.3 -69.3 275 38 19 -0.5 -0.3
40000 -60.6 -77.1 305 36 18 -4.4 -2.4 | -60.7 -77.3 290 41 21 -2.8 -1.6
38000 -60.1 -76.2 310 36 19 4.8 2.6 | -59.7 -75.5 295 43 22 4.6 2.5
36000 -57.2 -71.0 305 35 18 4.8 2.6 | -56.9 -70.4 295 45 23 4.6 2.5
34000 -53.9 -65.0 305 34 18 8.1 4.4 | -53.5 -64.3 295 46 23 8.4 4.6
32000 -49.0 -56.2 300 34 18 8.1 4.5 | -48.4 -55.1 290 42 22 8.6 4.7
30000 -44.0 -47.2 300 34 17 8.7 4.8 | -43.3 -45.9 285 39 20 8.4 4.6
29000 -40.8 -41.4 295 31 16 8.7 4.8 | -40.8 -41.4 285 37 19 8.4 4.6
28000 -38.2 -36.8 295 29 15 8.7 4.8 | -37.7 -35.9 280 35 18 8.4 4.6
27000 -35.6 -32.1 295 28 14 8.1 4.5 | -35.2 -31.4 275 34 17 8.0 4.4
26000 -33.2 -27.8 290 28 14 8.2 4.5 | -32.8 -27.0 270 34 17 8.1 4.4
25000 -30.7 -23.3 290 28 15 8.2 4.5 | -30.4 -22.7 270 34 18 8.1 4.4
24000 -28.3 -18.9 285 29 15 8.2 4.5 | -28.0 -18.4 265 34 18 8.0 4.4
23000 -25.8 -14.4 285 29 15 8.2 4.5 | -25.6 -14.1 265 32 17 8.0 4.4
22000 -23.4 -10.1 280 30 16 8.2 4.5 | -23.2 -9.8 260 31 16 8.0 4.4
21000 -21.1 -6.0 280 30 15 6.9 3.8 | -20.9 -5.6 260 29 15 7.4 4.0
20000 -19.0 -2.2 275 27 14 7.0 3.8 | -18.7 -1.7 260 28 14 7.4 4.1
19500 -17.9 -0.2 275 26 13 7.0 3.9 | -17.6 0.3 260 27 14 7.4 4.1
19000 -16.9 1.6 275 25 13 7.0 3.8 | -16.4 2.5 260 26 14 7.4 4.1
18500 -15.8 3.6 270 24 12 7.4 4.0 | -15.3 4.5 260 26 14 7.6 4.2
18000 -14.7 5.5 270 25 13 7.4 4.1 | -14.2 6.4 260 27 14 7.6 4.2
17500 -13.6 7.5 270 26 13 7.5 4.1 | -13.1 8.4 260 28 14 7.6 4.2
17000 -12.5 9.5 270 25 13 7.8 4.3 | -11.9 10.6 260 27 14 7.5 4.1
16500 -11.3 11.7 270 25 13 7.8 4.3 | -10.8 12.6 255 27 14 7.4 4.0
16000 -10.1 13.8 270 24 12 7.9 4.3 | -9.6 14.7 255 26 13 8.7 4.8
15500 -8.3 17.1 270 24 12 7.9 4.3 | -8.3 17.1 255 26 13 8.7 4.7
15000 -7.1 19.2 275 24 12 8.4 4.6 | -6.4 20.5 255 25 13 8.1 4.4
14500 -5.9 21.4 275 23 12 8.5 4.6 | -5.2 22.6 255 25 13 8.1 4.5
14000 -4.7 23.5 275 23 12 7.3 4.0 | -4.0 24.8 260 25 13 8.0 4.4
13500 -3.6 25.5 275 22 11 7.4 4.0 | -2.8 27.0 260 25 13 8.1 4.4
13000 -2.5 27.5 275 22 11 7.2 3.9 | -1.7 28.9 260 25 13 7.2 4.0
12500 -1.4 29.5 280 21 11 7.2 3.9 | -0.6 30.9 260 25 13 7.1 3.9
12000 -0.3 31.5 280 21 11 7.0 3.9 | 0.4 32.7 260 25 13 6.6 3.6
11500 0.7 33.3 280 20 10 7.0 3.9 | 1.3 34.3 260 24 12 6.4 3.5
11000 1.7 35.1 280 19 10 6.2 3.4 | 2.3 36.1 260 24 12 5.9 3.2
10500 2.6 36.7 280 18 9 6.3 3.5 | 3.1 37.6 260 22 11 6.0 3.3
10250 3.0 37.4 280 17 9 4.6 2.5 | 3.5 38.3 260 21 11 4.3 2.4
10000 3.3 37.9 275 17 9 4.8 2.7 | 3.7 38.7 260 20 10 4.6 2.5
9750 3.8 38.8 275 16 8 6.6 3.6 | 4.2 39.6 260 19 10 6.4 3.5
9500 4.3 39.7 275 15 8 6.3 3.4 | 4.6 40.3 260 17 9 6.1 3.3
9250 4.7 40.5 275 14 7 5.7 3.1 | 5.0 41.0 260 16 8 5.5 3.0
9000 5.1 41.2 270 13 7 4.7 2.6 | 5.4 41.7 255 14 7 5.6 3.1
8750 5.4 41.7 270 12 6 4.7 2.6 | 5.9 42.6 255 12 6 6.8 3.7
8500 5.8 42.4 265 11 6 4.7 2.6 | 6.4 43.5 255 11 5 6.9 3.8
8250 6.1 43.0 260 10 5 4.6 2.5 | 6.9 44.4 250 9 5 6.8 3.7
8000 6.5 43.7 250 8 4 4.4 2.4 | 7.4 45.3 250 7 4 6.6 3.6
7750 6.8 44.2 240 8 4 4.4 2.4 | 7.9 46.2 245 6 3 6.3 3.5
7500 7.1 44.8 225 7 4 4.7 2.6 | 8.4 47.1 245 5 3 6.1 3.4
7250 7.5 45.5 215 8 4 5.8 3.2 | 8.8 47.8 245 4 2 6.2 3.4
7000 8.0 46.4 205 8 4 6.3 3.4 | 9.3 48.7 245 4 2 6.0 3.3
6750 8.5 47.3 195 9 5 6.1 3.3 | 9.7 49.5 245 4 2 6.7 3.6
6500 8.9 48.0 185 11 5 3.7 2.0 | 10.1 50.2 240 4 2 3.4 1.8
6250 9.0 48.2 180 10 5 1.6 0.9 | 10.1 50.2 230 4 2 -1.4 -0.8
6000 9.1 48.4 175 10 5 3.0 1.7 | 9.9 49.8 220 5 2 -0.1 -0.1
5750 9.1 48.4 165 10 5 1.2 0.6 | 9.7 49.5 215 5 3 -4.3 -2.4
5500 8.9 48.0 160 9 5 -3.7 -2.0 | 8.7 47.7 200 6 3 -21.6 -11.9
________________________________________________________________________________
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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