Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
395
UXUS97 KBOU 191321
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0720 MDT Thursday, September 19, 2024
This forecast is for Thursday, September 19, 2024:
If the trigger temperature of 72.6 F/22.6 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 950 ft/min (4.8 m/s)
Maximum height of thermals.................. 16668 ft MSL (11349 ft AGL)
Forecast maximum temperature................... 86.0 F/30.5 C
Time of trigger temperature.................... 1030 MDT
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................. 14342 ft MSL (9023 ft AGL)
Thermal soaring outlook for Friday 09/20....... Excellent
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)................ Neither
Potential height of wave....................... 40717 ft MSL (35398 ft AGL)
Wave soaring outlook for Friday 09/20.......... Fair
Remarks...
Sunrise/Sunset.................... 06:45:08 / 19:00:53 MDT
Total possible sunshine........... 12 hr 15 min 45 sec (735 min 45 sec)
Altitude of sun at 12:53:00 MDT... 51.26 degrees
Upper air data from numerical model forecast valid on 09/19/2024 at 0600 MDT
Freezing level.................. 14127 ft MSL (8808 ft AGL)
Convective condensation level... 21182 ft MSL (15863 ft AGL)
Lifted condensation level....... 19223 ft MSL (13904 ft AGL)
Lifted index.................... +3.6
K index......................... -0.7
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 -62.0 -79.6 250 59 31 1.3 0.7 M M M M M
45000 -58.3 -72.9 255 87 45 5.1 2.8 M M M M M
40000 -50.6 -59.1 255 98 50 5.6 3.1 M M M M M
38000 -47.2 -53.0 255 93 48 5.6 3.1 M M M M M
36000 -43.9 -47.0 255 88 45 5.6 3.1 M M M M M
34000 -40.1 -40.2 255 79 41 6.5 3.6 M M M M M
32000 -36.2 -33.2 255 69 36 6.5 3.6 M M M M M
30000 -31.5 -24.7 255 61 31 7.2 4.0 44.6 112.2 11.1 M M
29000 -29.3 -20.7 255 58 30 7.3 4.0 43.6 110.5 10.5 M M
28000 -27.2 -17.0 250 54 28 7.3 4.0 42.8 109.0 9.9 M M
27000 -24.9 -12.8 250 53 27 7.6 4.2 41.8 107.3 9.3 M M
26000 -22.6 -8.7 250 52 27 7.6 4.2 41.0 105.8 8.7 M M
25000 -20.3 -4.5 250 52 27 7.6 4.2 40.3 104.5 8.3 M M
24000 -18.2 -0.8 250 50 26 7.0 3.8 39.4 102.8 7.6 M M
23000 -16.1 3.0 245 47 24 7.0 3.8 38.3 100.9 6.8 M M
22000 -14.0 6.8 245 45 23 7.1 3.9 37.4 99.3 6.1 M M
21000 -12.1 10.2 250 42 21 6.0 3.3 36.1 97.0 5.1 M M
20000 -10.4 13.3 250 38 19 6.0 3.3 34.8 94.6 4.0 M M
19500 -9.5 14.9 250 36 18 6.0 3.3 34.2 93.5 3.4 M M
19000 -8.6 16.5 250 34 18 6.0 3.3 33.6 92.4 2.9 M M
18500 -7.7 18.1 250 32 17 6.0 3.3 32.9 91.2 2.4 M M
18000 -6.8 19.8 255 30 16 6.1 3.3 32.3 90.1 1.8 M M
17500 -5.9 21.4 255 29 15 5.4 3.0 31.6 88.8 1.2 M M
17000 -5.1 22.8 255 27 14 5.4 3.0 30.8 87.5 0.6 M M
16500 -3.9 25.0 255 24 12 5.4 2.9 29.7 85.5 -0.4 928 4.7
16000 -3.1 26.4 260 22 11 5.4 3.6 29.0 84.2 -1.1 889 4.5
15500 -2.3 27.9 260 20 10 5.8 3.2 28.3 82.9 -1.7 850 4.3
15000 -1.5 29.3 260 18 9 6.0 3.3 27.6 81.8 -2.3 809 4.1
14500 -0.6 30.9 265 16 8 6.3 3.5 27.0 80.7 -2.9 768 3.9
14000 0.4 32.7 265 15 8 7.1 3.9 26.6 79.8 -3.4 723 3.7
13500 1.5 34.7 265 14 7 7.1 3.9 26.1 79.0 -3.8 678 3.4
13000 2.5 36.5 265 14 7 7.5 4.1 25.7 78.3 -4.3 631 3.2
12500 3.6 38.5 270 14 7 7.5 4.1 25.3 77.6 -4.7 584 3.0
12000 4.7 40.5 270 14 7 7.4 4.0 25.0 76.9 -5.1 537 2.7
11500 5.8 42.4 270 14 7 7.4 4.1 24.6 76.3 -5.5 490 2.5
11000 6.8 44.2 270 13 7 7.4 4.0 24.2 75.6 -5.9 443 2.3
10500 7.9 46.2 270 12 6 8.1 4.4 23.8 74.9 -6.4 397 2.0
10250 8.4 47.1 270 12 6 4.8 2.6 23.6 74.6 -6.6 373 1.9
10000 8.7 47.7 270 12 6 6.3 3.5 23.2 73.7 -7.0 357 1.8
9750 9.4 48.9 270 11 6 10.6 5.8 23.2 73.7 -7.1 329 1.7
9500 10.1 50.2 270 10 5 10.0 5.5 23.2 73.7 -7.1 300 1.5
9250 10.8 51.4 270 10 5 6.5 3.6 23.1 73.6 -7.2 272 1.4
9000 11.2 52.2 270 9 5 6.7 3.7 22.8 73.0 -7.5 253 1.3
8750 11.9 53.4 270 8 4 10.4 5.7 22.8 73.0 -7.6 225 1.1
8500 12.6 54.7 265 8 4 9.2 5.1 22.7 72.9 -7.6 196 1.0
8250 13.3 55.9 265 7 4 7.9 4.3 22.7 72.8 -7.7 169 0.9
8000 13.8 56.8 265 7 3 6.9 3.8 22.5 72.4 -7.9 146 0.7
7750 14.3 57.7 260 6 3 7.5 4.1 22.3 72.1 -8.1 122 0.6
7500 14.9 58.8 260 6 3 6.7 3.7 22.1 71.8 -8.3 99 0.5
7250 15.3 59.5 255 5 3 5.3 2.9 21.8 71.2 -8.6 78 0.4
7000 15.7 60.3 250 5 2 4.8 2.7 21.4 70.6 -9.0 59 0.3
6750 16.0 60.8 245 4 2 4.8 2.6 21.1 69.9 -9.4 41 0.2
6500 16.3 61.3 240 3 1 1.1 0.6 20.6 69.1 -9.9 26 0.1
6250 16.2 61.2 210 3 2 -2.3 -1.3 19.8 67.6 -10.8 22 0.1
6000 16.1 61.0 195 5 2 0.4 0.2 18.9 66.1 -11.6 18 0.1
5750 16.0 60.8 185 6 3 -6.8 -3.7 18.1 64.6 -12.5 13 0.1
5500 14.7 58.5 180 5 2 -28.6 -15.7 16.1 60.9 -14.6 45 0.2
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
09/19/2024 at 0900 MDT | 09/19/2024 at 1200 MDT
|
CAPE... 0.0 LI... +7.2 | CAPE... 0.0 LI... +6.9
CINH... -0.2 K Index... +0.9 | CINH... -0.0 K Index... +0.9
|
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 -62.3 -80.1 255 58 30 1.7 0.9 | -62.9 -81.2 255 54 28 1.9 1.1
45000 -58.1 -72.6 255 83 43 5.0 2.8 | -58.3 -72.9 255 79 41 5.3 2.9
40000 -50.5 -58.9 255 97 50 5.7 3.1 | -50.3 -58.5 255 93 48 5.8 3.2
38000 -47.1 -52.8 255 93 48 5.7 3.1 | -46.8 -52.2 255 92 47 5.8 3.2
36000 -43.7 -46.7 255 89 46 5.7 3.1 | -43.4 -46.1 255 90 47 5.8 3.2
34000 -39.9 -39.8 255 82 42 6.5 3.5 | -39.7 -39.5 255 86 44 6.2 3.4
32000 -35.6 -32.1 255 74 38 6.4 3.5 | -35.5 -31.9 255 79 41 6.1 3.4
30000 -31.3 -24.3 255 65 34 7.4 4.0 | -31.0 -23.8 255 70 36 7.9 4.3
29000 -29.1 -20.4 255 61 31 7.4 4.0 | -28.7 -19.7 255 66 34 7.9 4.3
28000 -26.9 -16.4 250 56 29 7.5 4.1 | -26.3 -15.3 255 61 31 7.8 4.3
27000 -24.5 -12.1 250 55 28 7.8 4.3 | -24.0 -11.2 255 58 30 7.5 4.1
26000 -22.2 -8.0 250 54 28 7.8 4.3 | -21.8 -7.2 255 55 29 7.5 4.1
25000 -19.9 -3.8 250 53 27 7.8 4.3 | -19.6 -3.3 255 53 27 7.5 4.1
24000 -17.7 0.1 250 52 27 6.8 3.7 | -17.4 0.7 255 51 26 7.2 3.9
23000 -15.7 3.7 250 49 25 6.8 3.7 | -15.2 4.6 255 50 26 7.2 3.9
22000 -13.7 7.3 250 47 24 6.9 3.8 | -13.1 8.4 250 48 25 7.3 4.0
21000 -11.9 10.6 245 44 22 5.7 3.2 | -11.2 11.8 250 46 24 5.8 3.2
20000 -10.2 13.6 250 40 20 5.8 3.2 | -9.5 14.9 250 43 22 5.9 3.2
19500 -9.3 15.3 250 38 19 5.8 3.2 | -8.6 16.5 250 42 21 5.8 3.2
19000 -8.5 16.7 250 36 18 5.8 3.2 | -7.7 18.1 250 40 21 5.5 3.0
18500 -7.6 18.3 250 34 17 5.9 3.2 | -7.0 19.4 250 38 20 5.1 2.8
18000 -6.7 19.9 250 31 16 5.9 3.2 | -6.2 20.8 245 36 18 5.0 2.8
17500 -5.9 21.4 250 29 15 5.4 3.0 | -5.5 22.1 245 33 17 5.1 2.8
17000 -5.1 22.8 250 27 14 5.5 3.0 | -4.3 24.3 250 29 15 5.2 2.9
16500 -4.2 24.4 255 25 13 5.1 2.8 | -3.7 25.3 250 27 14 4.2 2.3
16000 -3.2 26.2 255 22 11 4.8 2.6 | -3.0 26.6 250 24 12 4.3 2.4
15500 -2.5 27.5 260 20 10 5.2 2.8 | -2.4 27.7 250 21 11 5.2 2.9
15000 -1.7 28.9 260 18 9 5.3 2.9 | -1.6 29.1 250 19 10 5.5 3.0
14500 -1.0 30.2 265 16 8 5.7 3.1 | -0.8 30.6 250 17 9 6.0 3.3
14000 -0.0 32.0 265 15 8 6.4 3.5 | 0.2 32.4 250 16 8 6.7 3.7
13500 0.9 33.6 270 13 7 6.5 3.6 | 1.2 34.2 250 14 7 6.9 3.8
13000 1.9 35.4 270 13 7 7.1 3.9 | 2.3 36.1 250 13 7 7.8 4.3
12500 2.9 37.2 275 12 6 7.1 3.9 | 3.4 38.1 250 12 6 7.7 4.2
12000 4.0 39.2 275 12 6 7.3 4.0 | 4.5 40.1 250 11 6 7.8 4.3
11500 5.1 41.2 275 12 6 7.3 4.0 | 5.7 42.3 250 10 5 7.8 4.3
11000 6.1 43.0 270 11 6 7.3 4.0 | 6.8 44.2 250 9 5 8.0 4.4
10500 7.2 45.0 270 10 5 6.4 3.5 | 8.0 46.4 240 8 4 6.2 3.4
10250 7.6 45.7 270 9 5 3.7 2.1 | 8.4 47.1 240 8 4 4.6 2.5
10000 7.9 46.2 265 9 5 7.2 4.0 | 8.9 48.0 235 7 4 8.8 4.8
9750 8.6 47.5 265 8 4 10.6 5.8 | 9.6 49.3 230 7 3 10.7 5.9
9500 9.3 48.7 260 8 4 9.4 5.1 | 10.4 50.7 220 6 3 9.9 5.4
9250 9.9 49.8 255 7 4 5.5 3.0 | 11.0 51.8 215 5 3 6.6 3.6
9000 10.3 50.5 255 7 4 6.7 3.7 | 11.5 52.7 205 5 3 8.0 4.4
8750 11.0 51.8 245 7 3 10.7 5.9 | 12.2 54.0 205 5 2 11.4 6.2
8500 11.7 53.1 240 6 3 8.5 4.6 | 13.0 55.4 200 4 2 9.7 5.3
8250 12.2 54.0 235 6 3 5.9 3.3 | 13.7 56.7 195 4 2 7.2 4.0
8000 12.6 54.7 230 6 3 5.5 3.0 | 14.2 57.6 195 4 2 8.1 4.4
7750 13.1 55.6 225 5 3 7.7 4.2 | 14.9 58.8 190 4 2 11.7 6.4
7500 13.7 56.7 225 4 2 5.6 3.0 | 15.8 60.4 185 3 2 10.1 5.5
7250 13.9 57.0 215 3 2 2.6 1.5 | 16.4 61.5 185 3 2 7.3 4.0
7000 14.2 57.6 205 3 2 3.3 1.8 | 17.0 62.6 180 3 2 8.2 4.5
6750 14.5 58.1 195 3 1 6.0 3.3 | 17.7 63.9 180 3 2 12.5 6.8
6500 15.0 59.0 200 2 1 6.5 3.6 | 18.7 65.7 175 3 1 11.8 6.5
6250 15.4 59.7 190 2 1 5.1 2.8 | 19.4 66.9 175 3 1 9.3 5.1
6000 15.8 60.4 180 3 1 4.9 2.7 | 20.2 68.4 175 3 1 8.9 4.9
5750 16.2 61.2 180 3 2 8.3 4.5 | 20.9 69.6 170 3 1 14.3 7.9
5500 17.1 62.8 185 3 1 16.1 8.8 | 22.5 72.5 170 2 1 28.0 15.3
09/19/2024 at 1500 MDT | 09/19/2024 at 1800 MDT
|
CAPE... 0.0 LI... +5.6 | CAPE... 0.0 LI... +2.9
CINH... -0.0 K Index... +9.7 | CINH... -0.1 K Index... +15.1
|
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 -62.7 -80.9 255 55 28 1.8 1.0 | -63.6 -82.5 255 53 27 2.5 1.4
45000 -58.3 -72.9 255 77 40 5.5 3.0 | -58.5 -73.3 255 76 39 5.4 3.0
40000 -50.0 -58.0 255 92 48 5.6 3.1 | -50.3 -58.5 255 92 48 6.1 3.3
38000 -46.7 -52.1 255 93 48 5.6 3.1 | -46.7 -52.1 255 93 48 6.1 3.4
36000 -43.3 -45.9 255 94 48 5.6 3.1 | -43.0 -45.4 255 93 48 6.1 3.4
34000 -39.0 -38.2 255 86 44 6.5 3.6 | -38.4 -37.1 255 88 45 7.0 3.9
32000 -35.1 -31.2 255 77 40 6.5 3.5 | -34.1 -29.4 255 82 42 6.9 3.8
30000 -30.6 -23.1 255 69 35 7.8 4.3 | -29.8 -21.6 255 72 37 7.2 4.0
29000 -28.2 -18.8 255 65 33 7.8 4.3 | -27.6 -17.7 255 67 35 7.2 4.0
28000 -25.8 -14.4 255 61 31 7.7 4.3 | -25.5 -13.9 255 62 32 7.3 4.0
27000 -23.6 -10.5 255 57 29 7.6 4.2 | -23.3 -9.9 255 59 30 7.3 4.0
26000 -21.3 -6.3 255 54 28 7.6 4.2 | -21.1 -6.0 255 55 29 7.3 4.0
25000 -19.0 -2.2 255 51 26 7.6 4.2 | -18.9 -2.0 255 52 27 7.4 4.1
24000 -16.8 1.8 255 49 25 7.0 3.8 | -16.9 1.6 255 49 25 6.2 3.4
23000 -14.7 5.5 255 47 24 7.0 3.8 | -15.0 5.0 255 46 24 6.2 3.4
22000 -12.6 9.3 255 46 24 7.2 3.9 | -13.2 8.2 255 44 22 6.4 3.5
21000 -10.8 12.6 255 45 23 5.8 3.2 | -11.5 11.3 255 41 21 5.3 2.9
20000 -9.1 15.6 255 43 22 5.9 3.2 | -10.0 14.0 255 38 19 5.4 3.0
19500 -8.2 17.2 255 43 22 5.8 3.2 | -9.2 15.4 255 36 19 5.5 3.0
19000 -7.4 18.7 250 42 22 4.5 2.5 | -8.4 16.9 255 35 18 5.5 3.0
18500 -6.9 19.6 250 40 20 3.4 1.9 | -7.7 18.1 255 33 17 5.5 3.0
18000 -6.5 20.3 250 37 19 3.3 1.8 | -6.9 19.6 255 31 16 5.3 2.9
17500 -5.9 21.4 250 34 18 5.2 2.8 | -5.5 22.1 250 28 14 6.8 3.7
17000 -4.8 23.4 250 29 15 4.9 2.7 | -4.6 23.7 250 26 13 6.9 3.8
16500 -3.9 25.0 245 26 14 7.4 4.1 | -3.4 25.9 250 23 12 8.8 4.8
16000 -2.9 26.8 245 24 12 7.2 4.0 | -2.1 28.2 245 22 11 8.6 4.7
15500 -1.8 28.8 245 22 11 7.3 4.0 | -0.9 30.4 240 20 10 8.3 4.6
15000 -0.7 30.7 240 20 10 7.3 4.0 | 0.3 32.5 240 18 9 8.2 4.5
14500 0.3 32.5 240 18 9 7.5 4.1 | 1.6 34.9 235 16 8 8.3 4.6
14000 1.5 34.7 235 16 8 7.8 4.3 | 2.8 37.0 230 14 7 8.4 4.6
13500 2.6 36.7 225 14 7 7.9 4.3 | 4.1 39.4 220 12 6 8.4 4.6
13000 3.8 38.8 220 13 7 8.4 4.6 | 5.3 41.5 215 11 6 8.5 4.7
12500 5.1 41.2 215 12 6 8.4 4.6 | 6.6 43.9 205 10 5 8.5 4.7
12000 6.4 43.5 205 11 5 8.7 4.8 | 7.9 46.2 195 9 5 8.7 4.8
11500 7.7 45.9 200 9 5 8.7 4.7 | 9.2 48.6 185 9 4 8.9 4.9
11000 9.0 48.2 190 8 4 8.7 4.8 | 10.4 50.7 170 9 4 7.2 4.0
10500 10.4 50.7 185 8 4 4.2 2.3 | 11.4 52.5 155 9 5 11.2 6.1
10250 10.5 50.9 180 8 4 5.5 3.0 | 12.4 54.3 155 9 4 12.3 6.8
10000 11.3 52.3 175 7 4 12.5 6.9 | 13.1 55.6 150 9 5 8.0 4.4
9750 12.2 54.0 175 7 4 10.7 5.9 | 13.8 56.8 150 9 5 9.1 5.0
9500 13.0 55.4 170 7 3 11.0 6.0 | 14.4 57.9 145 9 5 8.9 4.9
9250 13.7 56.7 165 6 3 7.4 4.1 | 15.1 59.2 145 10 5 7.2 3.9
9000 14.2 57.6 160 6 3 8.5 4.7 | 15.6 60.1 135 10 5 8.2 4.5
8750 15.0 59.0 160 6 3 11.7 6.4 | 16.3 61.3 135 10 5 10.5 5.8
8500 15.8 60.4 155 6 3 10.5 5.8 | 17.1 62.8 135 10 5 9.9 5.4
8250 16.6 61.9 150 6 3 8.1 4.4 | 17.8 64.0 135 11 5 7.8 4.3
8000 17.1 62.8 145 6 3 8.8 4.8 | 18.3 64.9 125 11 6 8.4 4.6
7750 17.9 64.2 145 6 3 12.0 6.6 | 19.1 66.4 130 11 6 11.0 6.0
7500 18.8 65.8 140 6 3 10.3 5.7 | 19.9 67.8 130 11 6 9.9 5.4
7250 19.5 67.1 140 5 3 7.5 4.1 | 20.5 68.9 130 11 6 7.7 4.2
7000 20.0 68.0 135 5 3 8.1 4.4 | 21.1 70.0 125 12 6 7.8 4.3
6750 20.8 69.4 135 5 3 13.4 7.3 | 21.8 71.2 125 12 6 11.9 6.5
6500 21.9 71.4 135 5 3 12.3 6.7 | 22.7 72.9 125 11 6 11.3 6.2
6250 22.6 72.7 130 5 3 8.8 4.9 | 23.4 74.1 125 11 6 8.6 4.7
6000 23.3 73.9 130 5 3 9.1 5.0 | 24.1 75.4 120 11 6 8.8 4.8
5750 24.0 75.2 125 5 2 13.1 7.2 | 24.8 76.6 115 11 5 10.3 5.7
5500 25.4 77.7 130 4 2 25.1 13.8 | 25.7 78.3 120 9 5 13.2 7.2
________________________________________________________________________________
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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