Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
993
UXUS97 KBOU 071320
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0619 MST Friday, February 7, 2025
This forecast is for Friday, February 7, 2025:
If the trigger temperature of 61.2 F/16.2 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 437 ft/min (2.2 m/s)
Maximum height of thermals.................. 11010 ft MSL (5699 ft AGL)
Forecast maximum temperature................... 64.0 F/18.2 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................. 7868 ft MSL (2557 ft AGL)
Thermal soaring outlook for Saturday 02/08..... Poor
Wave Soaring Index............................. Good
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 PVA
Potential height of wave....................... 39599 ft MSL (34288 ft AGL)
Wave soaring outlook for Saturday 02/08........ Poor
Remarks...
Sunrise/Sunset.................... 07:00:45 / 17:26:31 MST
Total possible sunshine........... 10 hr 25 min 46 sec (625 min 46 sec)
Altitude of sun at 12:13:38 MST... 35.09 degrees
Upper air data from numerical model forecast valid on 02/07/2025 at 0500 MST
Freezing level.................. 5351 ft MSL (40 ft AGL)
Additional freezing level....... 11346 ft MSL (6035 ft AGL)
Convective condensation level... 21106 ft MSL (15795 ft AGL)
Lifted condensation level....... 17107 ft MSL (11796 ft AGL)
Lifted index.................... +7.5
K index......................... +0.2
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 -63.6 -82.5 265 95 49 3.7 2.0 M M M M M
45000 -58.1 -72.6 265 106 54 2.3 1.2 M M M M M
40000 -54.6 -66.3 265 117 60 2.4 1.3 M M M M M
38000 -53.4 -64.1 270 115 59 1.6 0.9 M M M M M
36000 -52.3 -62.1 270 108 56 1.6 0.9 M M M M M
34000 -50.2 -58.4 270 102 52 7.4 4.0 M M M M M
32000 -45.7 -50.3 270 96 49 7.4 4.1 M M M M M
30000 -41.1 -42.0 270 91 47 8.1 4.4 34.6 94.4 12.7 M M
29000 -38.7 -37.7 270 89 46 8.1 4.4 33.9 93.0 12.3 M M
28000 -36.3 -33.3 270 87 45 8.1 4.4 33.3 91.9 12.0 M M
27000 -33.8 -28.8 270 85 44 8.3 4.5 32.8 91.0 11.7 M M
26000 -31.3 -24.3 270 83 43 8.3 4.6 32.1 89.9 11.3 M M
25000 -28.8 -19.8 270 81 42 8.4 4.6 31.6 88.9 11.0 M M
24000 -26.3 -15.3 270 79 41 8.2 4.5 31.2 88.2 10.8 M M
23000 -23.9 -11.0 270 76 39 8.0 4.4 30.5 86.9 10.3 M M
22000 -21.5 -6.7 270 74 38 8.0 4.4 29.9 85.7 9.9 M M
21000 -19.1 -2.4 270 71 36 7.8 4.3 29.3 84.7 9.6 M M
20000 -16.8 1.8 270 66 34 7.7 4.2 28.5 83.3 9.0 M M
19500 -15.7 3.7 270 64 33 7.7 4.2 28.1 82.6 8.8 M M
19000 -13.9 7.0 265 61 31 7.8 4.3 27.6 81.8 8.4 M M
18500 -12.8 9.0 265 59 30 6.8 3.7 27.3 81.1 8.1 M M
18000 -11.8 10.8 265 57 29 6.7 3.7 26.7 80.1 7.7 M M
17500 -10.8 12.6 265 55 28 6.3 3.5 26.2 79.2 7.3 M M
17000 -10.0 14.0 265 52 27 5.5 3.0 25.5 77.9 6.7 M M
16500 -9.2 15.4 265 49 25 5.5 3.0 24.8 76.6 6.1 M M
16000 -8.4 16.9 265 47 24 5.0 2.8 24.0 75.3 5.4 M M
15500 -7.6 18.3 265 46 24 5.1 2.8 23.2 73.8 4.7 M M
15000 -6.9 19.6 265 45 23 5.7 3.1 22.5 72.5 4.1 M M
14500 -6.0 21.2 265 43 22 5.9 3.3 21.9 71.3 3.5 M M
14000 -5.1 22.8 265 40 21 6.3 3.5 21.2 70.2 2.9 M M
13500 -4.1 24.6 265 39 20 6.7 3.7 20.7 69.3 2.4 M M
13000 -3.1 26.4 265 38 20 6.7 3.7 20.2 68.4 2.0 M M
12500 -2.2 28.0 265 38 20 6.5 3.6 19.7 67.5 1.5 M M
12000 -1.2 29.8 265 38 20 6.5 3.5 19.2 66.6 1.0 M M
11500 -0.2 31.6 265 38 19 6.2 3.4 18.6 65.5 0.5 M M
11000 0.7 33.3 265 36 19 6.2 3.4 18.1 64.6 -0.0 435 2.2
10500 1.6 34.9 265 37 19 6.1 3.4 17.5 63.5 -0.6 392 2.0
10250 2.1 35.8 265 38 19 6.7 3.7 17.3 63.1 -0.8 370 1.9
10000 2.7 36.9 265 38 19 8.3 4.5 17.1 62.7 -1.0 346 1.8
9750 3.3 37.9 265 36 19 7.6 4.2 17.0 62.5 -1.1 320 1.6
9500 3.8 38.8 265 36 18 6.5 3.6 16.7 62.1 -1.3 297 1.5
9250 4.3 39.7 265 35 18 7.1 3.9 16.5 61.7 -1.6 274 1.4
9000 4.8 40.6 265 34 17 5.8 3.2 16.3 61.3 -1.8 252 1.3
8750 5.2 41.4 265 33 17 6.2 3.4 15.9 60.7 -2.1 232 1.2
8500 5.8 42.4 265 31 16 7.6 4.2 15.7 60.3 -2.3 208 1.1
8250 6.3 43.3 265 30 15 7.3 4.0 15.5 60.0 -2.5 184 0.9
8000 6.8 44.2 265 28 14 5.2 2.8 15.3 59.6 -2.7 162 0.8
7750 7.1 44.8 265 26 13 3.9 2.1 14.9 58.8 -3.2 145 0.7
7500 7.5 45.5 265 23 12 5.4 3.0 14.5 58.1 -3.5 127 0.6
7250 7.8 46.0 265 20 11 3.4 1.9 14.1 57.4 -3.9 109 0.6
7000 7.9 46.2 265 18 9 -0.3 -0.2 13.5 56.2 -4.6 98 0.5
6750 7.8 46.0 265 16 8 -2.1 -1.2 12.6 54.7 -5.4 94 0.5
6500 7.7 45.9 260 12 6 -1.1 -0.6 11.7 53.1 -6.3 91 0.5
6250 7.5 45.5 255 9 4 -7.5 -4.1 10.8 51.4 -7.3 90 0.5
6000 6.5 43.7 245 7 3 -13.8 -7.6 9.1 48.4 -9.0 111 0.6
5750 5.6 42.1 235 5 3 -10.4 -5.7 7.5 45.4 -10.7 132 0.7
5500 4.4 39.9 210 3 2 -28.9 -15.8 5.5 41.9 -12.6 161 0.8
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
02/07/2025 at 0800 MST | 02/07/2025 at 1100 MST
|
CAPE... 0.0 LI... +6.1 | CAPE... 0.0 LI... +6.9
CINH... -0.1 K Index... -1.3 | CINH... -0.1 K Index... -1.9
|
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 -63.9 -83.0 265 95 49 3.2 1.8 | -64.5 -84.1 265 94 49 2.7 1.5
45000 -59.2 -74.6 260 105 54 2.2 1.2 | -60.4 -76.7 260 106 54 3.5 1.9
40000 -55.6 -68.1 265 111 57 2.3 1.3 | -55.0 -67.0 265 108 56 3.4 1.9
38000 -54.0 -65.2 270 107 55 2.4 1.3 | -53.4 -64.1 265 102 52 2.2 1.2
36000 -52.6 -62.7 270 100 52 2.4 1.3 | -52.1 -61.8 265 91 47 2.2 1.2
34000 -50.0 -58.0 270 94 49 8.2 4.5 | -49.7 -57.5 265 83 43 7.9 4.4
32000 -45.0 -49.0 270 91 47 8.2 4.5 | -44.9 -48.8 265 82 42 8.0 4.4
30000 -40.1 -40.2 270 87 45 8.2 4.5 | -40.0 -40.0 265 81 41 8.9 4.9
29000 -37.7 -35.9 270 85 44 8.2 4.5 | -36.6 -33.9 265 81 42 8.9 4.9
28000 -35.2 -31.4 270 83 42 8.2 4.5 | -33.9 -29.0 265 82 42 9.0 4.9
27000 -32.8 -27.0 265 80 41 7.7 4.2 | -31.4 -24.5 265 82 42 7.7 4.2
26000 -30.5 -22.9 265 78 40 7.7 4.2 | -29.0 -20.2 265 80 41 7.9 4.3
25000 -28.2 -18.8 265 76 39 7.7 4.2 | -26.7 -16.1 265 79 41 7.9 4.3
24000 -25.9 -14.6 265 74 38 7.8 4.3 | -24.3 -11.7 265 77 40 7.6 4.2
23000 -23.6 -10.5 265 71 37 7.9 4.3 | -22.1 -7.8 265 75 39 7.5 4.1
22000 -21.2 -6.2 265 68 35 7.9 4.3 | -19.9 -3.8 265 73 38 7.5 4.1
21000 -18.8 -1.8 265 65 34 7.6 4.2 | -17.7 0.1 260 71 37 7.2 4.0
20000 -16.6 2.1 265 62 32 7.4 4.1 | -15.6 3.9 260 69 36 7.2 4.0
19500 -14.9 5.2 265 60 31 7.4 4.1 | -14.5 5.9 260 68 35 7.2 4.0
19000 -13.8 7.2 265 58 30 7.4 4.1 | -13.4 7.9 260 67 34 7.2 4.0
18500 -12.7 9.1 265 56 29 7.8 4.3 | -12.3 9.9 260 66 34 7.1 3.9
18000 -11.5 11.3 265 54 28 7.7 4.2 | -11.3 11.7 260 64 33 7.0 3.9
17500 -10.3 13.5 265 52 27 7.4 4.1 | -10.3 13.5 260 63 32 7.0 3.9
17000 -9.3 15.3 265 51 26 7.0 3.8 | -9.2 15.4 260 61 31 6.9 3.8
16500 -8.2 17.2 265 50 26 7.1 3.9 | -8.2 17.2 260 60 31 6.9 3.8
16000 -7.3 18.9 265 49 25 5.9 3.3 | -7.1 19.2 260 58 30 6.9 3.8
15500 -6.4 20.5 265 48 25 6.1 3.3 | -5.6 21.9 260 55 28 6.9 3.8
15000 -5.5 22.1 265 47 24 5.6 3.1 | -4.6 23.7 260 54 28 6.0 3.3
14500 -4.7 23.5 265 45 23 5.5 3.0 | -3.7 25.3 260 53 27 5.9 3.2
14000 -3.9 25.0 265 43 22 5.7 3.1 | -2.9 26.8 265 51 26 5.2 2.9
13500 -3.0 26.6 265 41 21 5.9 3.2 | -2.2 28.0 260 47 24 4.7 2.6
13000 -2.1 28.2 265 39 20 5.9 3.2 | -1.5 29.3 260 43 22 4.9 2.7
12500 -1.3 29.7 265 38 20 5.8 3.2 | -0.7 30.7 260 41 21 5.4 3.0
12000 -0.4 31.3 265 37 19 5.6 3.1 | 0.0 32.0 260 39 20 5.5 3.0
11500 0.3 32.5 260 35 18 4.5 2.5 | 0.8 33.4 260 36 18 5.6 3.1
11000 0.9 33.6 260 32 17 4.7 2.6 | 1.6 34.9 260 32 16 5.5 3.0
10500 1.7 35.1 260 32 17 5.2 2.8 | 2.4 36.3 260 31 16 5.2 2.9
10250 2.1 35.8 260 33 17 5.5 3.0 | 2.8 37.0 265 31 16 6.4 3.5
10000 2.5 36.5 260 33 17 6.9 3.8 | 3.4 38.1 265 31 16 7.5 4.1
9750 3.0 37.4 260 33 17 6.9 3.8 | 3.9 39.0 265 31 16 6.0 3.3
9500 3.5 38.3 260 33 17 6.2 3.4 | 4.3 39.7 265 32 16 5.5 3.0
9250 4.0 39.2 260 34 17 6.8 3.7 | 4.7 40.5 265 32 16 5.2 2.8
9000 4.5 40.1 260 34 18 5.3 2.9 | 5.1 41.2 265 32 17 7.0 3.8
8750 4.8 40.6 260 33 17 5.0 2.7 | 5.7 42.3 265 32 16 7.4 4.1
8500 5.3 41.5 260 32 16 6.2 3.4 | 6.1 43.0 265 31 16 5.8 3.2
8250 5.7 42.3 260 31 16 6.0 3.3 | 6.6 43.9 265 29 15 6.2 3.4
8000 6.2 43.2 260 29 15 4.5 2.5 | 7.0 44.6 265 28 15 5.9 3.3
7750 6.5 43.7 260 27 14 4.5 2.5 | 7.5 45.5 265 26 13 7.1 3.9
7500 6.9 44.4 260 24 12 6.1 3.4 | 8.0 46.4 265 24 12 8.2 4.5
7250 7.3 45.1 260 21 11 4.8 2.6 | 8.6 47.5 260 22 12 7.2 3.9
7000 7.6 45.7 255 19 10 2.7 1.5 | 9.1 48.4 260 21 11 4.8 2.6
6750 7.8 46.0 255 16 8 1.6 0.9 | 9.4 48.9 260 19 10 5.9 3.2
6500 7.9 46.2 250 13 7 2.2 1.2 | 10.0 50.0 260 17 9 8.3 4.6
6250 8.0 46.4 240 9 5 -1.9 -1.1 | 10.6 51.1 260 14 7 6.2 3.4
6000 7.6 45.7 230 8 4 -6.1 -3.3 | 11.0 51.8 260 12 6 4.3 2.3
5750 7.3 45.1 210 8 4 -3.7 -2.0 | 11.3 52.3 255 10 5 5.7 3.1
5500 6.5 43.7 200 7 3 -22.5 -12.3 | 11.9 53.4 255 8 4 11.0 6.0
02/07/2025 at 1400 MST | 02/07/2025 at 1700 MST
|
CAPE... 0.0 LI... +6.5 | CAPE... 0.0 LI... +6.6
CINH... -0.1 K Index... +1.0 | CINH... -0.2 K Index... +2.7
|
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 -64.5 -84.1 265 91 47 2.6 1.4 | -64.6 -84.3 265 84 43 2.9 1.6
45000 -60.5 -76.9 260 101 52 4.1 2.3 | -59.8 -75.6 260 95 49 4.4 2.4
40000 -54.3 -65.7 260 105 54 3.9 2.1 | -53.2 -63.8 265 99 51 4.4 2.4
38000 -52.3 -62.1 260 100 51 3.0 1.7 | -51.1 -60.0 265 98 51 3.0 1.7
36000 -50.5 -58.9 260 92 47 3.0 1.7 | -49.3 -56.7 265 96 49 3.0 1.7
34000 -48.1 -54.6 260 85 44 6.4 3.5 | -47.0 -52.6 265 93 48 6.0 3.3
32000 -44.2 -47.6 260 81 42 6.5 3.5 | -43.3 -45.9 260 85 44 6.1 3.3
30000 -40.0 -40.0 260 78 40 8.2 4.5 | -39.0 -38.2 260 78 40 7.2 4.0
29000 -36.9 -34.4 260 78 40 8.3 4.5 | -36.8 -34.2 260 77 40 7.2 4.0
28000 -34.4 -29.9 260 78 40 8.3 4.5 | -34.6 -30.3 260 75 39 7.2 4.0
27000 -31.9 -25.4 260 78 40 8.8 4.8 | -32.4 -26.3 260 74 38 8.3 4.6
26000 -29.3 -20.7 260 77 40 8.8 4.8 | -29.9 -21.8 260 72 37 8.4 4.6
25000 -26.7 -16.1 260 77 39 8.8 4.8 | -27.4 -17.3 260 71 37 8.4 4.6
24000 -24.1 -11.4 260 76 39 8.1 4.4 | -24.9 -12.8 255 70 36 8.2 4.5
23000 -21.8 -7.2 260 76 39 7.6 4.2 | -22.5 -8.5 255 69 35 8.0 4.4
22000 -19.5 -3.1 260 76 39 7.6 4.2 | -20.1 -4.2 255 67 35 8.1 4.4
21000 -17.3 0.9 260 76 39 7.2 3.9 | -17.7 0.1 255 67 34 7.4 4.0
20000 -15.2 4.6 260 73 38 7.1 3.9 | -15.6 3.9 260 67 35 7.1 3.9
19500 -14.1 6.6 260 72 37 7.1 3.9 | -14.6 5.7 260 68 35 7.1 3.9
19000 -13.1 8.4 260 71 36 7.2 3.9 | -13.5 7.7 260 68 35 7.1 3.9
18500 -12.0 10.4 260 70 36 7.0 3.8 | -12.4 9.7 260 69 35 6.8 3.8
18000 -11.0 12.2 260 68 35 6.7 3.7 | -11.5 11.3 260 68 35 6.2 3.4
17500 -10.1 13.8 260 67 35 6.7 3.7 | -10.6 12.9 260 67 35 6.3 3.5
17000 -9.1 15.6 260 66 34 6.2 3.4 | -9.7 14.5 265 66 34 5.9 3.2
16500 -8.2 17.2 260 65 33 6.2 3.4 | -8.8 16.2 265 65 33 5.9 3.2
16000 -7.3 18.9 260 63 33 6.0 3.3 | -7.9 17.8 265 64 33 5.6 3.1
15500 -6.0 21.2 260 60 31 5.8 3.2 | -6.8 19.8 265 61 32 5.3 2.9
15000 -5.1 22.8 260 57 30 5.8 3.2 | -6.0 21.2 265 59 31 5.4 3.6
14500 -4.2 24.4 260 54 28 5.8 3.2 | -5.2 22.6 260 56 29 5.4 3.0
14000 -3.4 25.9 260 51 26 6.2 3.4 | -4.4 24.1 260 53 27 5.7 3.1
13500 -2.4 27.7 260 50 26 6.5 3.6 | -3.5 25.7 260 49 25 6.0 3.3
13000 -1.4 29.5 260 48 25 6.4 3.5 | -2.6 27.3 260 46 24 6.0 3.3
12500 -0.5 31.1 260 44 23 5.9 3.2 | -1.7 28.9 260 42 22 5.9 3.2
12000 0.3 32.5 260 40 21 6.0 3.3 | -0.9 30.4 255 37 19 6.1 3.3
11500 1.3 34.3 255 38 19 6.6 3.6 | 0.1 32.2 255 35 18 7.3 4.0
11000 2.2 36.0 255 37 19 6.3 3.5 | 1.2 34.2 255 33 17 7.0 3.8
10500 3.0 37.4 255 35 18 3.8 2.1 | 2.1 35.8 250 30 15 5.3 2.9
10250 3.3 37.9 255 33 17 6.3 3.4 | 2.5 36.5 250 29 15 7.3 4.0
10000 3.9 39.0 255 33 17 9.1 5.0 | 3.1 37.6 250 27 14 9.7 5.3
9750 4.5 40.1 255 32 16 7.7 4.2 | 3.8 38.8 250 26 14 8.8 4.9
9500 5.0 41.0 255 30 15 6.8 3.8 | 4.5 40.1 245 25 13 8.2 4.5
9250 5.5 41.9 255 27 14 7.0 3.8 | 5.1 41.2 245 23 12 8.3 4.5
9000 6.1 43.0 250 26 13 8.4 4.6 | 5.7 42.3 245 22 12 9.3 5.1
8750 6.7 44.1 250 25 13 8.5 4.7 | 6.4 43.5 245 23 12 9.6 5.3
8500 7.3 45.1 250 23 12 7.4 4.1 | 7.1 44.8 245 22 11 8.8 4.8
8250 7.9 46.2 250 21 11 7.6 4.2 | 7.8 46.0 240 20 10 9.3 5.1
8000 8.4 47.1 250 20 10 7.9 4.3 | 8.4 47.1 240 19 10 8.1 4.4
7750 9.0 48.2 250 18 9 8.4 4.6 | 9.0 48.2 240 17 9 8.3 4.6
7500 9.7 49.5 250 16 8 8.4 4.6 | 9.7 49.5 235 16 8 9.8 5.4
7250 10.3 50.5 250 15 8 8.2 4.5 | 10.4 50.7 235 15 8 9.0 5.0
7000 10.8 51.4 250 14 7 6.8 3.7 | 11.0 51.8 235 14 7 6.7 3.7
6750 11.4 52.5 250 13 6 8.7 4.8 | 11.5 52.7 230 12 6 7.8 4.3
6500 12.2 54.0 255 12 6 11.1 6.1 | 12.2 54.0 230 10 5 10.5 5.7
6250 12.9 55.2 255 10 5 10.0 5.5 | 12.9 55.2 230 8 4 8.6 4.7
6000 13.7 56.7 255 10 5 9.5 5.2 | 13.5 56.3 225 7 4 7.0 3.8
5750 14.4 57.9 255 9 5 9.2 5.1 | 14.0 57.2 220 6 3 6.7 3.7
5500 15.1 59.2 255 8 4 12.5 6.9 | 14.3 57.7 220 4 2 1.2 0.7
________________________________________________________________________________
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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