Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
100
UXUS97 KBOU 050125
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1815 MST Tuesday, February 4, 2025
This forecast is for Wednesday, February 5, 2025:
If the trigger temperature of 61.2 F/16.2 C is reached...then
Thermal Soaring Index....................... Fair
Maximum rate of lift........................ 638 ft/min (3.2 m/s)
Maximum height of thermals.................. 13355 ft MSL (8031 ft AGL)
Forecast maximum temperature................... 69.0 F/21.0 C
Time of trigger temperature.................... 1045 MST
Time of overdevelopment........................ None
Middle/high clouds during soaring window....... None
Surface winds during soaring window............ Between 20 mph and 30 mph
Height of the -3 thermal index................. 10340 ft MSL (5016 ft AGL)
Thermal soaring outlook for Thursday 02/06..... Fair
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1700 MST)......... Little change
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1700 MST)................ Weak NVA
Potential height of wave....................... 14441 ft MSL (9117 ft AGL)
Wave soaring outlook for Thursday 02/06........ Fair
Remarks... Gusty winds likely late morning and early afternoon
Sunrise/Sunset.................... 07:02:54 / 17:24:08 MST
Total possible sunshine........... 10 hr 21 min 14 sec (621 min 14 sec)
Altitude of sun at 12:13:31 MST... 34.47 degrees
Upper air data from numerical model forecast valid on 02/05/2025 at 0500 MST
Freezing level.................. 11603 ft MSL (6279 ft AGL)
Convective condensation level... 17575 ft MSL (12251 ft AGL)
Lifted condensation level....... 16733 ft MSL (11409 ft AGL)
Lifted index.................... -1.0
K index......................... -11.4
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 -63.5 -82.3 270 87 45 3.7 2.0 M M M M M
45000 -57.6 -71.7 275 105 54 5.8 3.2 M M M M M
40000 -48.7 -55.7 275 108 56 5.9 3.2 M M M M M
38000 -45.8 -50.4 275 105 54 4.4 2.4 M M M M M
36000 -42.8 -45.0 275 99 51 4.4 2.4 M M M M M
34000 -40.6 -41.1 275 90 46 1.5 0.8 M M M M M
32000 -39.7 -39.5 275 76 39 1.5 0.8 M M M M M
30000 -38.7 -37.7 270 64 33 2.7 1.5 38.4 101.1 13.4 M M
29000 -37.8 -36.0 270 61 32 2.8 1.5 35.5 95.9 11.4 M M
28000 -37.0 -34.6 265 59 31 2.8 1.5 32.8 91.0 9.4 M M
27000 -36.2 -33.2 265 58 30 3.4 1.9 30.3 86.5 7.6 M M
26000 -34.7 -30.5 260 55 28 5.2 2.8 28.3 82.9 6.1 M M
25000 -33.2 -27.8 260 51 26 5.1 2.8 26.5 79.8 4.8 M M
24000 -31.6 -24.9 260 48 25 5.1 2.8 24.9 76.9 3.5 M M
23000 -29.1 -20.4 260 46 24 9.2 5.1 24.4 75.9 3.1 M M
22000 -26.3 -15.3 260 45 23 9.2 5.0 24.1 75.5 3.0 M M
21000 -23.6 -10.5 260 43 22 9.2 5.1 24.0 75.3 2.9 M M
20000 -20.8 -5.4 260 40 20 9.2 5.1 23.8 74.8 2.7 M M
19500 -19.4 -2.9 260 38 20 9.2 5.1 23.7 74.6 2.7 M M
19000 -18.0 -0.4 255 36 19 9.2 5.1 23.6 74.5 2.6 M M
18500 -16.0 3.2 255 34 17 8.9 4.9 23.5 74.3 2.5 M M
18000 -14.7 5.5 250 32 17 8.9 4.9 23.4 74.0 2.4 M M
17500 -13.3 8.1 250 31 16 8.8 4.8 23.2 73.8 2.3 M M
17000 -12.0 10.4 250 31 16 8.4 4.6 23.0 73.4 2.1 M M
16500 -10.8 12.6 250 32 16 8.5 4.6 22.8 73.0 1.9 M M
16000 -9.5 14.9 255 33 17 8.2 4.5 22.5 72.6 1.7 M M
15500 -8.3 17.1 255 33 17 8.2 4.5 22.3 72.1 1.5 M M
15000 -7.1 19.2 255 34 17 7.9 4.3 22.0 71.6 1.3 M M
14500 -6.0 21.2 260 34 18 7.7 4.2 21.6 71.0 0.9 M M
14000 -4.8 23.4 260 35 18 7.1 3.9 21.3 70.4 0.6 M M
13500 -3.9 25.0 260 33 17 6.3 3.5 20.8 69.4 0.1 M M
13000 -2.9 26.8 260 31 16 6.6 3.6 20.2 68.4 -0.4 604 3.1
12500 -1.9 28.6 260 31 16 7.5 4.1 19.8 67.6 -0.8 557 2.8
12000 -0.8 30.6 260 32 16 7.4 4.0 19.4 67.0 -1.2 509 2.6
11500 0.2 32.4 260 31 16 6.2 3.4 18.9 66.0 -1.7 465 2.4
11000 1.1 34.0 260 30 16 6.3 3.5 18.4 65.1 -2.2 423 2.1
10500 2.0 35.6 260 31 16 6.1 3.4 17.8 64.1 -2.8 381 1.9
10250 2.5 36.5 260 32 17 6.3 3.5 17.5 63.6 -3.1 360 1.8
10000 3.0 37.4 260 33 17 6.7 3.7 17.3 63.1 -3.4 338 1.7
9750 3.4 38.1 260 33 17 6.5 3.6 17.0 62.7 -3.6 317 1.6
9500 3.9 39.0 260 34 17 6.3 3.5 16.8 62.2 -3.9 296 1.5
9250 4.3 39.7 260 34 17 6.2 3.4 16.5 61.7 -4.2 275 1.4
9000 4.8 40.6 260 34 18 6.9 3.8 16.2 61.2 -4.5 254 1.3
8750 5.3 41.5 260 33 17 7.4 4.0 16.1 60.9 -4.7 231 1.2
8500 5.8 42.4 255 33 17 6.9 3.8 15.8 60.5 -5.0 208 1.1
8250 6.3 43.3 255 32 16 7.4 4.1 15.6 60.1 -5.2 185 0.9
8000 6.8 44.2 255 31 16 5.8 3.2 15.4 59.8 -5.4 163 0.8
7750 7.2 45.0 255 29 15 6.0 3.3 15.1 59.1 -5.8 144 0.7
7500 7.8 46.0 255 27 14 8.0 4.4 14.9 58.8 -6.0 120 0.6
7250 8.3 46.9 255 26 13 6.7 3.7 14.7 58.5 -6.2 96 0.5
7000 8.7 47.7 255 24 12 3.4 1.8 14.4 57.9 -6.6 77 0.4
6750 8.8 47.8 255 22 11 1.0 0.5 13.8 56.8 -7.2 66 0.3
6500 9.0 48.2 255 19 10 4.1 2.2 13.2 55.7 -7.8 54 0.3
6250 9.1 48.4 250 17 9 -5.1 -2.8 12.6 54.7 -8.4 42 0.2
6000 8.2 46.8 245 14 7 -14.6 -8.0 10.9 51.7 -10.1 63 0.3
5750 7.1 44.8 240 12 6 -16.7 -9.2 9.1 48.4 -11.9 88 0.4
5500 5.1 41.2 225 8 4 -40.0 -21.9 6.4 43.5 -14.7 141 0.7
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
02/05/2025 at 0800 MST | 02/05/2025 at 1100 MST
|
CAPE... 0.0 LI... +4.5 | CAPE... 0.0 LI... +5.6
CINH... -0.1 K Index... -10.4 | CINH... -0.3 K Index... -3.1
|
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 -63.5 -82.3 270 87 45 3.1 1.7 | -64.7 -84.5 265 80 41 4.2 2.3
45000 -58.5 -73.3 270 105 54 6.0 3.3 | -58.1 -72.6 270 100 51 5.4 3.0
40000 -49.2 -56.6 275 109 56 6.1 3.4 | -50.0 -58.0 275 111 57 5.4 3.0
38000 -46.3 -51.3 275 108 56 4.4 2.4 | -46.6 -51.9 275 113 58 4.9 2.7
36000 -43.7 -46.7 280 107 55 4.4 2.4 | -43.6 -46.5 280 113 58 4.9 2.7
34000 -41.1 -42.0 285 104 53 2.4 1.3 | -41.3 -42.3 280 112 58 1.8 1.0
32000 -39.6 -39.3 285 98 50 2.4 1.3 | -40.2 -40.4 285 107 55 1.8 1.0
30000 -37.9 -36.2 290 92 47 4.2 2.3 | -38.7 -37.7 285 103 53 4.7 2.6
29000 -36.6 -33.9 290 89 46 4.2 2.3 | -37.2 -35.0 285 101 52 4.8 2.6
28000 -35.4 -31.7 290 86 44 4.2 2.3 | -35.8 -32.4 280 99 51 4.8 2.6
27000 -34.1 -29.4 290 83 43 5.0 2.7 | -34.4 -29.9 280 97 50 6.2 3.4
26000 -32.2 -26.0 290 78 40 6.4 3.5 | -32.1 -25.8 280 94 48 7.7 4.2
25000 -30.3 -22.5 290 72 37 6.4 3.5 | -29.7 -21.5 280 90 46 7.7 4.2
24000 -28.4 -19.1 290 67 34 6.4 3.5 | -27.4 -17.3 285 87 45 7.7 4.2
23000 -26.3 -15.3 285 64 33 7.0 3.8 | -25.1 -13.2 285 82 42 7.9 4.3
22000 -24.2 -11.6 285 61 32 7.0 3.8 | -22.7 -8.9 285 77 40 7.9 4.3
21000 -22.2 -8.0 280 59 30 7.0 3.8 | -20.4 -4.7 290 73 37 7.6 4.2
20000 -20.1 -4.2 275 54 28 7.0 3.8 | -17.6 0.3 285 68 35 7.2 4.0
19500 -19.0 -2.2 275 52 27 7.0 3.8 | -16.5 2.3 285 66 34 7.2 4.0
19000 -18.0 -0.4 275 50 26 7.0 3.8 | -15.5 4.1 285 64 33 7.3 4.0
18500 -16.4 2.5 270 47 24 7.3 4.0 | -14.4 6.1 285 62 32 6.8 3.7
18000 -15.3 4.5 270 45 23 7.4 4.1 | -13.4 7.9 280 60 31 6.7 3.7
17500 -14.2 6.4 265 43 22 7.3 4.0 | -12.4 9.7 280 59 30 6.7 3.7
17000 -13.1 8.4 265 42 22 6.9 3.8 | -11.4 11.5 280 57 30 6.6 3.6
16500 -12.1 10.2 265 41 21 6.9 3.8 | -10.5 13.1 280 56 29 6.6 3.6
16000 -11.0 12.2 265 41 21 7.5 4.1 | -9.5 14.9 280 55 28 6.0 3.3
15500 -9.9 14.2 265 42 22 7.5 4.1 | -8.6 16.5 275 54 28 6.0 3.3
15000 -8.8 16.2 265 43 22 7.7 4.2 | -7.8 18.0 275 54 28 6.5 3.6
14500 -7.6 18.3 270 44 23 7.7 4.2 | -6.8 19.8 275 53 27 6.9 3.8
14000 -6.4 20.5 270 45 23 7.7 4.2 | -5.7 21.7 275 52 27 7.0 3.9
13500 -5.3 22.5 270 45 23 7.6 4.2 | -4.7 23.5 275 52 27 7.3 4.0
13000 -4.2 24.4 270 46 24 7.6 4.2 | -3.6 25.5 275 51 26 7.2 4.0
12500 -3.0 26.6 270 46 24 7.6 4.2 | -2.6 27.3 275 50 26 6.8 3.7
12000 -1.9 28.6 270 46 24 7.6 4.2 | -1.6 29.1 275 49 25 6.8 3.7
11500 -0.8 30.6 270 46 23 7.2 3.9 | -0.5 31.1 275 47 24 6.7 3.7
11000 0.3 32.5 270 44 23 7.1 3.9 | 0.5 32.9 275 43 22 6.7 3.6
10500 1.2 34.2 270 43 22 5.9 3.3 | 1.4 34.5 275 41 21 5.8 3.2
10250 1.7 35.1 270 43 22 6.6 3.6 | 1.8 35.2 275 41 21 6.5 3.5
10000 2.2 36.0 265 42 21 8.3 4.5 | 2.4 36.3 275 39 20 7.5 4.1
9750 2.8 37.0 265 40 21 7.7 4.2 | 2.9 37.2 270 39 20 6.6 3.6
9500 3.3 37.9 265 39 20 6.6 3.6 | 3.3 37.9 270 40 20 5.7 3.1
9250 3.8 38.8 265 39 20 6.9 3.8 | 3.8 38.8 270 41 21 5.9 3.2
9000 4.3 39.7 265 38 20 6.8 3.7 | 4.2 39.6 270 41 21 6.1 3.3
8750 4.8 40.6 265 36 19 6.5 3.6 | 4.7 40.5 270 40 21 6.6 3.6
8500 5.3 41.5 265 35 18 6.2 3.4 | 5.1 41.2 270 39 20 6.8 3.7
8250 5.7 42.3 260 34 18 6.6 3.6 | 5.6 42.1 265 38 20 6.6 3.6
8000 6.2 43.2 260 33 17 5.3 2.9 | 6.1 43.0 265 37 19 7.2 4.3
7750 6.5 43.7 260 33 17 5.3 2.9 | 6.7 44.1 265 36 19 8.5 4.6
7500 7.0 44.6 260 32 16 6.6 3.6 | 7.4 45.3 265 35 18 8.9 4.9
7250 7.4 45.3 260 30 16 5.9 3.3 | 8.0 46.4 265 34 17 8.5 4.7
7000 7.8 46.0 255 29 15 4.5 2.5 | 8.6 47.5 265 32 17 7.5 4.1
6750 8.1 46.6 255 28 14 4.7 2.6 | 9.2 48.6 265 32 16 8.8 4.8
6500 8.6 47.5 250 25 13 7.9 4.3 | 9.9 49.8 260 30 15 10.8 5.9
6250 9.0 48.2 250 22 11 0.4 0.2 | 10.7 51.3 260 28 14 8.8 4.8
6000 8.6 47.5 245 20 10 -6.4 -3.5 | 11.3 52.3 260 26 13 7.2 4.0
5750 8.2 46.8 240 18 9 -8.1 -4.4 | 11.8 53.2 260 23 12 7.1 3.9
5500 6.7 44.1 230 13 7 -33.3 -18.3 | 12.3 54.1 260 19 10 7.7 4.2
02/05/2025 at 1400 MST | 02/05/2025 at 1700 MST
|
CAPE... 0.0 LI... +4.1 | CAPE... 0.0 LI... +4.0
CINH... 0.0 K Index... -5.9 | CINH... 0.0 K Index... -11.1
|
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 -65.0 -85.0 260 83 43 4.3 2.4 | -64.9 -84.8 260 82 42 4.3 2.3
45000 -58.3 -72.9 265 102 53 5.6 3.1 | -58.2 -72.8 265 100 51 6.0 3.3
40000 -49.9 -57.8 275 115 59 5.6 3.1 | -49.1 -56.4 275 115 59 6.1 3.3
38000 -46.9 -52.4 275 118 61 4.7 2.6 | -46.1 -51.0 275 120 62 4.5 2.5
36000 -44.0 -47.2 280 121 62 4.7 2.6 | -43.4 -46.1 275 123 63 4.5 2.5
34000 -41.3 -42.3 280 121 62 2.4 1.3 | -40.7 -41.3 275 124 64 2.6 1.4
32000 -39.8 -39.6 280 115 59 2.4 1.3 | -39.2 -38.6 275 120 62 2.5 1.4
30000 -38.0 -36.4 280 108 55 4.4 2.4 | -37.5 -35.5 275 112 58 4.0 2.2
29000 -36.7 -34.1 275 102 53 4.5 2.5 | -36.2 -33.2 275 105 54 4.1 2.2
28000 -35.3 -31.5 275 97 50 4.5 2.5 | -35.0 -31.0 270 97 50 4.1 2.2
27000 -34.0 -29.2 270 92 47 5.7 3.1 | -33.8 -28.8 270 90 46 4.7 2.6
26000 -31.9 -25.4 275 89 46 6.9 3.8 | -32.1 -25.8 270 85 44 5.6 3.1
25000 -29.8 -21.6 275 86 44 6.9 3.8 | -30.4 -22.7 270 79 41 5.6 3.1
24000 -27.8 -18.0 275 83 43 7.0 3.8 | -28.7 -19.7 270 74 38 5.6 3.1
23000 -25.6 -14.1 275 75 39 7.4 4.1 | -26.8 -16.2 270 71 36 6.8 3.7
22000 -23.4 -10.1 280 67 34 7.4 4.1 | -24.7 -12.5 270 68 35 6.8 3.7
21000 -21.1 -6.0 280 58 30 7.4 4.0 | -22.7 -8.9 275 65 33 7.4 4.0
20000 -18.9 -2.0 280 57 30 7.4 4.0 | -20.3 -4.5 275 63 32 8.2 4.5
19500 -17.8 -0.0 280 57 29 7.4 4.0 | -19.0 -2.2 275 62 32 8.2 4.5
19000 -16.7 1.9 280 56 29 7.4 4.0 | -17.8 -0.0 275 61 31 8.2 4.5
18500 -15.6 3.9 280 56 29 7.5 4.1 | -16.6 2.1 275 60 31 8.2 4.5
18000 -14.4 6.1 280 54 28 8.1 4.4 | -15.3 4.5 275 59 30 8.3 4.5
17500 -12.6 9.3 275 52 27 7.8 4.3 | -13.5 7.7 270 57 29 8.0 4.4
17000 -11.5 11.3 275 52 27 6.8 3.7 | -12.3 9.9 270 56 29 7.3 4.0
16500 -10.5 13.1 275 53 27 6.9 3.8 | -11.2 11.8 270 55 28 7.4 4.0
16000 -9.6 14.7 275 52 27 5.5 3.0 | -10.2 13.6 270 55 28 7.0 3.9
15500 -8.8 16.2 275 49 25 5.6 3.1 | -9.1 15.6 270 55 28 7.1 3.9
15000 -8.0 17.6 275 45 23 6.7 3.7 | -8.1 17.4 270 54 28 6.9 3.8
14500 -6.9 19.6 270 42 21 7.2 4.0 | -7.0 19.4 270 51 26 6.9 3.8
14000 -5.8 21.6 270 38 20 7.6 4.2 | -6.0 21.2 270 47 24 6.9 3.8
13500 -4.6 23.7 270 37 19 8.2 4.5 | -5.0 23.0 270 43 22 6.9 3.8
13000 -3.4 25.9 270 36 18 8.2 4.5 | -4.0 24.8 265 38 20 7.0 3.8
12500 -2.2 28.0 270 36 19 8.1 4.5 | -3.0 26.6 265 38 19 7.1 3.9
12000 -1.0 30.2 265 37 19 8.2 4.5 | -1.9 28.6 265 38 20 7.3 4.0
11500 0.3 32.5 265 37 19 8.8 4.8 | -0.7 30.7 265 36 18 8.8 4.8
11000 1.6 34.9 265 36 19 8.5 4.7 | 0.6 33.1 265 32 17 8.5 4.7
10500 2.7 36.9 265 37 19 6.6 3.6 | 1.7 35.1 265 32 16 6.8 3.7
10250 3.2 37.8 265 37 19 8.2 4.5 | 2.2 36.0 265 32 16 8.2 4.5
10000 3.9 39.0 265 37 19 9.8 5.4 | 2.9 37.2 265 32 17 9.5 5.2
9750 4.6 40.3 265 37 19 7.4 4.1 | 3.6 38.5 265 33 17 7.1 3.9
9500 5.1 41.2 265 38 19 6.2 3.4 | 4.0 39.2 265 34 18 5.9 3.2
9250 5.6 42.1 265 38 20 6.0 3.3 | 4.4 39.9 265 35 18 5.8 3.2
9000 6.0 42.8 265 39 20 8.2 4.5 | 4.9 40.8 265 36 19 7.6 4.2
8750 6.7 44.1 265 38 20 7.9 4.4 | 5.5 41.9 265 36 18 8.4 4.6
8500 7.1 44.8 265 37 19 5.4 3.0 | 6.1 43.0 265 35 18 7.1 3.9
8250 7.6 45.7 265 35 18 6.1 3.4 | 6.6 43.9 265 33 17 7.4 4.1
8000 8.0 46.4 260 34 17 6.0 3.3 | 7.1 44.8 265 32 17 7.4 4.1
7750 8.5 47.3 260 32 17 8.2 4.5 | 7.7 45.9 265 31 16 9.0 4.9
7500 9.2 48.6 260 31 16 9.7 5.3 | 8.4 47.1 265 30 16 10.2 5.6
7250 9.8 49.6 260 30 15 9.0 5.0 | 9.2 48.6 265 30 15 9.4 5.2
7000 10.5 50.9 260 29 15 7.9 4.3 | 9.8 49.6 265 29 15 7.9 4.3
6750 11.1 52.0 260 28 14 9.1 5.0 | 10.4 50.7 265 28 14 8.7 4.8
6500 11.9 53.4 260 26 14 11.2 6.1 | 11.1 52.0 270 26 14 10.9 6.0
6250 12.7 54.9 260 25 13 9.6 5.3 | 11.9 53.4 270 25 13 7.8 4.3
6000 13.3 55.9 260 23 12 7.9 4.4 | 12.3 54.1 270 23 12 4.6 2.5
5750 13.9 57.0 260 22 11 9.6 5.2 | 12.7 54.9 270 20 10 5.5 3.0
5500 14.7 58.5 260 18 9 12.8 7.0 | 12.9 55.2 270 16 8 0.6 0.3
________________________________________________________________________________
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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