Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
282
UXUS97 KBOU 211306
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0705 MDT Saturday, September 21, 2024
This forecast is for Saturday, September 21, 2024:
If the trigger temperature of 77.8 F/25.5 C is reached...then
Thermal Soaring Index....................... Poor
Maximum rate of lift........................ 24 ft/min (0.1 m/s)
Maximum height of thermals.................. 6226 ft MSL (927 ft AGL)
Forecast maximum temperature................... 71.0 F/22.1 C
Time of trigger temperature.................... None
Time of overdevelopment........................ 1500 MDT
Middle/high clouds during soaring window....... None
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 5536 ft MSL (237 ft AGL)
Thermal soaring outlook for Sunday 09/22....... Poor
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1800 MDT)......... No change
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1800 MDT)................ Weak PVA
Potential height of wave....................... 40174 ft MSL (34875 ft AGL)
Wave soaring outlook for Sunday 09/22.......... Poor
Remarks...
Sunrise/Sunset.................... 06:47:01 / 18:57:35 MDT
Total possible sunshine........... 12 hr 10 min 34 sec (730 min 34 sec)
Altitude of sun at 12:52:18 MDT... 50.48 degrees
Upper air data from numerical model forecast valid on 09/21/2024 at 0600 MDT
Freezing level.................. 14595 ft MSL (9296 ft AGL)
Convective condensation level... 19617 ft MSL (14318 ft AGL)
Lifted condensation level....... 15614 ft MSL (10315 ft AGL)
Lifted index.................... +6.2
K index......................... +15.1
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 -62.3 -80.1 240 51 26 1.8 1.0 M M M M M
45000 -58.4 -73.1 230 73 38 5.0 2.8 M M M M M
40000 -50.5 -58.9 230 86 44 5.2 2.9 M M M M M
38000 -47.4 -53.3 230 86 44 5.2 2.9 M M M M M
36000 -44.2 -47.6 230 86 44 5.3 2.9 M M M M M
34000 -40.5 -40.9 230 80 41 6.7 3.7 M M M M M
32000 -36.5 -33.7 230 71 37 6.7 3.7 M M M M M
30000 -32.7 -26.9 230 61 32 6.1 3.3 43.9 111.1 16.9 M M
29000 -30.9 -23.6 230 56 29 6.1 3.3 42.5 108.5 16.0 M M
28000 -28.6 -19.5 230 50 26 6.1 3.4 40.9 105.6 15.0 M M
27000 -26.7 -16.1 230 46 24 6.4 3.5 39.5 103.1 14.1 M M
26000 -24.8 -12.6 230 43 22 6.4 3.5 38.2 100.8 13.2 M M
25000 -22.8 -9.0 225 39 20 6.3 3.5 37.1 98.7 12.4 M M
24000 -20.6 -5.1 225 36 19 8.2 4.5 36.2 97.2 11.9 M M
23000 -18.1 -0.6 225 34 17 8.2 4.5 35.6 96.2 11.5 M M
22000 -15.7 3.7 225 31 16 8.4 4.6 35.2 95.3 11.2 M M
21000 -13.6 7.5 225 28 15 6.4 3.5 34.1 93.4 10.5 M M
20000 -11.7 10.9 220 25 13 6.4 3.5 32.9 91.3 9.6 M M
19500 -10.7 12.7 220 24 12 6.4 3.5 32.4 90.3 9.2 M M
19000 -9.8 14.4 220 23 12 5.8 3.2 31.9 89.4 8.7 M M
18500 -9.0 15.8 215 22 12 5.4 3.0 31.1 87.9 8.1 M M
18000 -8.3 17.1 215 22 11 5.2 2.9 30.3 86.6 7.4 M M
17500 -7.3 18.9 215 21 11 8.2 4.5 29.8 85.7 6.9 M M
17000 -6.2 20.8 215 20 10 8.1 4.4 29.5 85.1 6.6 M M
16500 -5.0 23.0 215 19 10 8.5 4.7 29.3 84.7 6.4 M M
16000 -3.8 25.2 215 16 8 8.7 4.8 29.1 84.3 6.2 M M
15500 -2.5 27.5 210 14 7 8.6 4.7 28.9 84.0 6.1 M M
15000 -1.3 29.7 210 11 5 8.0 4.4 28.6 83.6 5.8 M M
14500 0.5 32.9 210 6 3 8.4 4.6 28.2 82.8 5.5 M M
14000 1.8 35.2 215 4 2 8.8 4.8 28.1 82.5 5.3 M M
13500 3.1 37.6 235 2 1 8.5 4.7 27.9 82.2 5.2 M M
13000 4.2 39.6 340 1 0 7.5 4.1 27.6 81.7 4.9 M M
12500 5.3 41.5 020 3 2 7.6 4.2 27.2 81.0 4.6 M M
12000 6.6 43.9 025 5 3 9.0 4.9 27.0 80.7 4.4 M M
11500 7.8 46.0 025 7 4 8.9 4.9 26.9 80.4 4.2 M M
11000 9.2 48.6 025 9 5 8.7 4.7 26.8 80.2 4.1 M M
10500 10.5 50.9 020 10 5 6.9 3.8 26.6 79.9 4.1 M M
10250 11.0 51.8 020 11 5 6.2 3.4 26.3 79.3 3.8 M M
10000 11.6 52.9 020 11 6 9.2 5.0 26.2 79.1 3.7 M M
9750 12.3 54.1 020 11 6 9.4 5.2 26.1 79.0 3.7 M M
9500 13.0 55.4 020 12 6 9.3 5.1 26.1 79.0 3.7 M M
9250 13.7 56.7 020 12 6 6.9 3.8 26.0 78.8 3.6 M M
9000 14.1 57.4 020 13 7 5.3 2.9 25.7 78.2 3.3 M M
8750 14.5 58.1 015 15 8 5.9 3.2 25.4 77.7 3.0 M M
8500 14.9 58.8 015 17 8 5.7 3.1 25.1 77.1 2.7 M M
8250 15.3 59.5 010 18 9 5.4 2.9 24.7 76.5 2.4 M M
8000 15.7 60.3 010 21 11 5.4 2.9 24.4 75.9 2.0 M M
7750 16.1 61.0 010 22 12 5.3 2.9 24.1 75.3 1.7 M M
7500 16.5 61.7 010 24 12 6.2 3.4 23.7 74.7 1.4 M M
7250 17.0 62.6 010 25 13 7.8 4.3 23.5 74.4 1.2 M M
7000 17.6 63.7 010 25 13 7.8 4.3 23.4 74.1 1.1 M M
6750 18.2 64.8 010 26 13 8.1 4.5 23.3 73.9 0.9 M M
6500 18.7 65.7 010 25 13 4.7 2.6 23.1 73.5 0.7 M M
6250 18.9 66.0 005 21 11 0.8 0.5 22.5 72.5 0.1 M M
6000 19.0 66.2 005 17 9 4.6 2.5 21.9 71.4 -0.4 15 0.1
5750 19.3 66.7 360 13 7 -2.3 -1.3 21.5 70.6 -0.9 M M
5500 18.1 64.6 355 7 4 -33.3 -18.3 19.5 67.1 -2.8 29 0.1
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
09/21/2024 at 0900 MDT | 09/21/2024 at 1200 MDT
|
CAPE... 0.0 LI... +3.8 | CAPE... 0.0 LI... +4.8
CINH... 0.0 K Index... +17.4 | CINH... 0.0 K Index... +13.2
|
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 -60.9 -77.6 240 48 24 1.1 0.6 | -60.2 -76.4 230 39 20 1.6 0.9
45000 -58.0 -72.4 230 74 38 4.5 2.5 | -57.2 -71.0 225 70 36 3.6 2.0
40000 -51.2 -60.2 225 86 45 4.8 2.7 | -51.5 -60.7 220 97 50 4.6 2.5
38000 -47.9 -54.2 225 87 45 4.9 2.7 | -48.8 -55.8 215 92 47 4.5 2.5
36000 -44.9 -48.8 225 87 45 5.0 2.7 | -46.1 -51.0 215 86 44 4.5 2.5
34000 -41.4 -42.5 225 80 41 6.1 3.4 | -42.7 -44.9 215 80 41 6.3 3.5
32000 -37.7 -35.9 225 71 37 6.2 3.4 | -38.9 -38.0 215 74 38 6.3 3.5
30000 -34.0 -29.2 225 58 30 6.3 3.5 | -34.8 -30.6 215 64 33 7.1 3.9
29000 -32.1 -25.8 225 51 26 6.3 3.5 | -32.1 -25.8 215 57 29 7.1 3.9
28000 -30.2 -22.4 225 43 22 6.2 3.4 | -30.0 -22.0 210 51 26 7.3 4.0
27000 -28.0 -18.4 225 39 20 7.7 4.2 | -27.6 -17.7 210 48 24 8.3 4.6
26000 -25.7 -14.3 220 36 19 7.6 4.2 | -25.1 -13.2 210 45 23 8.3 4.5
25000 -23.4 -10.1 220 34 17 7.7 4.2 | -22.6 -8.7 215 42 22 8.3 4.6
24000 -21.0 -5.8 215 31 16 8.0 4.4 | -20.3 -4.5 210 38 20 7.5 4.1
23000 -18.6 -1.5 215 29 15 8.0 4.4 | -18.0 -0.4 210 33 17 7.5 4.1
22000 -16.2 2.8 215 26 13 8.0 4.4 | -15.8 3.6 210 28 14 7.6 4.2
21000 -13.6 7.5 210 25 13 6.7 3.7 | -13.6 7.5 205 26 13 7.1 3.9
20000 -11.6 11.1 205 26 13 6.7 3.7 | -11.5 11.3 205 24 13 7.1 3.9
19500 -10.6 12.9 205 26 13 6.8 3.7 | -10.4 13.3 205 24 12 7.1 3.9
19000 -9.7 14.5 205 26 13 5.6 3.1 | -9.3 15.3 205 23 12 6.1 3.4
18500 -8.9 16.0 205 26 13 5.7 3.1 | -8.6 16.5 205 24 12 5.3 2.9
18000 -8.1 17.4 205 26 13 6.4 3.5 | -7.8 18.0 205 25 13 5.2 2.8
17500 -7.0 19.4 205 25 13 7.9 4.3 | -6.9 19.6 210 24 13 7.3 4.0
17000 -5.9 21.4 210 23 12 7.9 4.3 | -5.9 21.4 210 23 12 7.2 3.9
16500 -4.8 23.4 210 21 11 8.1 4.5 | -4.9 23.2 210 22 11 7.7 4.2
16000 -3.7 25.3 210 20 10 8.3 4.5 | -3.8 25.2 205 20 10 8.1 4.4
15500 -2.5 27.5 215 18 9 8.3 4.6 | -2.6 27.3 205 17 9 8.1 4.4
15000 -1.3 29.7 210 15 8 8.2 4.5 | -1.5 29.3 200 14 7 7.6 4.2
14500 0.0 32.0 205 11 6 7.9 4.3 | 0.1 32.2 175 9 4 7.5 4.1
14000 1.1 34.0 195 8 4 6.9 3.8 | 1.2 34.2 145 8 4 7.2 4.0
13500 2.1 35.8 165 5 2 6.9 3.8 | 2.2 36.0 115 9 5 7.3 4.0
13000 3.3 37.9 130 4 2 8.1 4.5 | 3.4 38.1 105 10 5 7.7 4.2
12500 4.5 40.1 095 4 2 8.1 4.4 | 4.6 40.3 100 11 5 7.7 4.2
12000 5.6 42.1 075 5 3 7.6 4.2 | 5.6 42.1 095 11 5 5.9 3.2
11500 6.8 44.2 065 5 3 8.1 4.5 | 6.5 43.7 090 10 5 6.2 3.4
11000 7.7 45.9 055 6 3 3.3 1.8 | 7.0 44.6 080 10 5 1.4 0.8
10500 8.2 46.8 045 8 4 4.1 2.2 | 7.3 45.1 065 10 5 2.0 1.1
10250 8.5 47.3 040 8 4 2.2 1.2 | 7.4 45.3 060 10 5 0.4 0.2
10000 8.5 47.3 035 9 5 -0.2 -0.1 | 7.3 45.1 060 11 5 -2.2 -1.2
9750 8.5 47.3 035 10 5 -0.1 -0.1 | 7.0 44.6 055 12 6 -2.7 -1.5
9500 8.5 47.3 030 12 6 0.2 0.1 | 6.8 44.2 055 13 7 -2.7 -1.5
9250 8.4 47.1 030 13 7 -1.9 -1.1 | 6.4 43.5 050 14 7 -7.2 -3.9
9000 8.1 46.6 035 16 8 -4.2 -2.3 | 5.8 42.4 035 12 6 -5.6 -3.1
8750 7.7 45.9 035 18 9 -4.2 -2.3 | 5.6 42.1 020 11 6 -1.2 -0.7
8500 7.3 45.1 040 21 11 -4.3 -2.3 | 5.5 41.9 010 11 6 1.9 1.1
8250 7.0 44.6 040 23 12 -4.0 -2.2 | 5.9 42.6 005 11 6 8.2 4.5
8000 6.6 43.9 040 24 12 -3.5 -1.9 | 6.6 43.9 005 11 6 9.8 5.4
7750 6.4 43.5 040 24 12 -1.0 -0.6 | 7.3 45.1 005 11 6 10.2 5.6
7500 6.5 43.7 035 23 12 2.5 1.4 | 8.1 46.6 005 11 6 10.3 5.6
7250 6.8 44.2 030 21 11 4.5 2.5 | 8.8 47.8 005 11 6 9.8 5.4
7000 7.1 44.8 020 18 9 4.4 2.4 | 9.6 49.3 360 11 6 9.9 5.4
6750 7.5 45.5 010 15 8 5.3 2.9 | 10.3 50.5 360 11 6 9.9 5.4
6500 8.0 46.4 005 13 7 9.5 5.2 | 11.1 52.0 360 11 5 10.3 5.7
6250 8.8 47.8 005 13 7 12.0 6.6 | 11.9 53.4 360 10 5 10.4 5.7
6000 9.7 49.5 005 12 6 10.6 5.8 | 12.6 54.7 360 10 5 11.0 6.0
5750 10.5 50.9 005 11 6 12.8 7.0 | 13.7 56.7 360 10 5 18.5 10.2
5500 11.7 53.1 005 10 5 19.5 10.7 | 15.5 59.9 360 10 5 28.7 15.7
09/21/2024 at 1500 MDT | 09/21/2024 at 1800 MDT
|
CAPE... 0.0 LI... +1.7 | CAPE... +0.7 LI... +1.1
CINH... 0.0 K Index... +21.0 | CINH... 0.0 K Index... +22.7
|
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 -58.4 -73.1 225 34 17 3.8 2.1 | -58.7 -73.7 220 37 19 5.1 2.8
45000 -53.8 -64.8 230 58 30 0.3 0.2 | -52.8 -63.0 220 52 27 -0.6 -0.3
40000 -53.2 -63.8 205 101 52 3.2 1.7 | -53.8 -64.8 205 80 41 -0.0 -0.0
38000 -50.9 -59.6 205 92 48 3.8 2.1 | -51.7 -61.1 200 78 40 3.8 2.1
36000 -48.7 -55.7 205 84 43 3.8 2.1 | -49.2 -56.6 200 75 39 3.8 2.1
34000 -44.4 -47.9 205 82 42 9.0 4.9 | -45.4 -49.7 200 67 35 7.7 4.2
32000 -39.0 -38.2 205 83 43 9.0 4.9 | -40.7 -41.3 195 57 29 7.7 4.2
30000 -34.0 -29.2 205 80 41 7.8 4.3 | -35.5 -31.9 190 49 25 9.3 5.1
29000 -31.7 -25.1 205 77 40 7.8 4.3 | -32.8 -27.0 190 45 23 9.3 5.1
28000 -28.8 -19.8 205 73 38 7.9 4.3 | -30.0 -22.0 190 41 21 9.4 5.1
27000 -26.6 -15.9 200 63 32 7.3 4.0 | -27.4 -17.3 190 37 19 8.3 4.6
26000 -24.5 -12.1 200 51 26 7.4 4.0 | -24.9 -12.8 190 32 16 8.3 4.6
25000 -22.3 -8.1 195 39 20 7.4 4.0 | -22.5 -8.5 185 27 14 8.3 4.6
24000 -20.6 -5.1 190 29 15 4.3 2.4 | -20.3 -4.5 180 23 12 6.2 3.4
23000 -19.4 -2.9 190 19 10 4.2 2.3 | -18.4 -1.1 170 20 10 6.3 3.4
22000 -18.1 -0.6 200 10 5 4.1 2.2 | -16.6 2.1 160 19 10 6.3 3.4
21000 -16.3 2.7 205 6 3 7.4 4.1 | -14.8 5.4 150 18 9 5.8 3.2
20000 -14.1 6.6 200 4 2 7.5 4.1 | -13.1 8.4 140 18 9 5.8 3.2
19500 -13.0 8.6 195 4 2 7.5 4.1 | -12.2 10.0 135 18 9 5.8 3.2
19000 -11.9 10.6 185 3 2 7.5 4.1 | -11.0 12.2 125 19 10 6.0 3.3
18500 -10.9 12.4 150 4 2 7.4 4.1 | -10.1 13.8 125 19 10 6.0 3.3
18000 -9.8 14.4 135 6 3 7.5 4.1 | -9.2 15.4 125 20 10 6.1 3.3
17500 -8.7 16.3 125 9 5 7.2 4.0 | -8.3 17.1 120 20 10 6.5 3.6
17000 -7.7 18.1 120 12 6 7.2 4.0 | -7.4 18.7 120 21 11 6.5 3.6
16500 -6.6 20.1 115 15 8 6.2 3.4 | -6.4 20.5 120 22 11 6.2 3.4
16000 -5.9 21.4 115 17 9 5.2 2.9 | -5.6 21.9 120 22 11 6.1 3.3
15500 -5.2 22.6 115 18 9 5.3 2.9 | -4.7 23.5 115 22 11 5.9 3.3
15000 -4.3 24.3 115 19 10 6.7 3.7 | -3.9 25.0 115 21 11 5.7 3.1
14500 -3.3 26.1 115 20 10 6.4 3.5 | -3.0 26.6 115 21 11 5.8 3.2
14000 -1.6 29.1 115 20 10 8.7 4.8 | -2.1 28.2 115 21 11 6.9 3.8
13500 -0.3 31.5 115 19 10 8.8 4.8 | -1.1 30.0 110 21 11 6.9 3.8
13000 1.1 34.0 115 18 9 9.1 5.0 | -0.2 31.6 110 21 11 6.4 3.5
12500 2.5 36.5 115 16 8 9.0 4.9 | 0.7 33.3 105 22 11 6.7 3.7
12000 3.8 38.8 115 15 8 7.6 4.2 | 1.5 34.7 100 22 11 4.0 2.2
11500 4.9 40.8 110 14 7 7.8 4.3 | 2.2 36.0 095 22 11 4.3 2.4
11000 5.2 41.4 105 12 6 -2.6 -1.4 | 2.7 36.9 090 21 11 2.5 1.3
10500 5.0 41.0 095 10 5 -1.7 -0.9 | 3.1 37.6 080 19 10 2.6 1.4
10250 4.9 40.8 090 9 5 0.1 0.0 | 3.3 37.9 075 19 10 1.9 1.0
10000 4.9 40.8 085 8 4 1.8 1.0 | 3.4 38.1 075 18 9 2.5 1.4
9750 5.0 41.0 075 6 3 1.6 0.9 | 3.7 38.7 065 17 9 3.8 2.1
9500 5.1 41.2 060 5 2 2.5 1.4 | 3.9 39.0 060 16 8 3.2 1.8
9250 5.4 41.7 045 4 2 5.0 2.8 | 4.2 39.6 050 15 8 4.7 2.6
9000 5.8 42.4 040 4 2 8.6 4.7 | 4.6 40.3 045 15 8 6.0 3.3
8750 6.6 43.9 040 3 2 10.7 5.9 | 5.0 41.0 045 14 7 5.8 3.2
8500 7.4 45.3 035 3 2 10.2 5.6 | 5.4 41.7 040 13 7 5.9 3.2
8250 8.1 46.6 035 3 2 9.9 5.4 | 5.8 42.4 035 12 6 5.9 3.2
8000 8.9 48.0 030 3 2 9.9 5.4 | 6.3 43.3 035 11 5 5.8 3.2
7750 9.6 49.3 030 3 1 9.9 5.4 | 6.7 44.1 030 9 5 4.9 2.7
7500 10.3 50.5 025 3 1 10.0 5.5 | 7.0 44.6 030 8 4 4.1 2.3
7250 11.1 52.0 025 3 1 10.1 5.5 | 7.3 45.1 020 6 3 4.1 2.2
7000 11.8 53.2 020 3 1 10.1 5.5 | 7.5 45.5 005 4 2 4.0 2.2
6750 12.6 54.7 020 2 1 10.2 5.6 | 7.8 46.0 340 3 2 3.9 2.1
6500 13.4 56.1 015 2 1 10.0 5.5 | 8.1 46.6 300 3 2 6.3 3.4
6250 14.1 57.4 010 2 1 9.6 5.3 | 8.7 47.7 280 4 2 8.4 4.6
6000 14.8 58.6 010 2 1 10.1 5.6 | 9.2 48.6 265 5 2 7.1 3.9
5750 15.7 60.3 005 2 1 13.4 7.4 | 9.8 49.6 260 6 3 10.2 5.6
5500 16.8 62.2 005 2 1 17.5 9.6 | 10.8 51.4 255 5 3 17.9 9.8
________________________________________________________________________________
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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