Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
116
UXUS97 KBOU 171321
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0717 MDT Tuesday, September 17, 2024
This forecast is for Tuesday, September 17, 2024:
If the trigger temperature of 79.0 F/26.1 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1011 ft/min (5.1 m/s)
Maximum height of thermals.................. 14814 ft MSL (9521 ft AGL)
Forecast maximum temperature................... 87.0 F/31.0 C
Time of trigger temperature.................... 1030 MDT
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................. 10765 ft MSL (5472 ft AGL)
Thermal soaring outlook for Wednesday 09/18.... 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)................ Weak PVA
Potential height of wave....................... 45990 ft MSL (40697 ft AGL)
Wave soaring outlook for Wednesday 09/18....... Fair
Remarks...
Sunrise/Sunset.................... 06:43:15 / 19:04:11 MDT
Total possible sunshine........... 12 hr 20 min 56 sec (740 min 56 sec)
Altitude of sun at 12:53:43 MDT... 52.04 degrees
Upper air data from numerical model forecast valid on 09/17/2024 at 0600 MDT
Freezing level.................. 15697 ft MSL (10404 ft AGL)
Convective condensation level... 15820 ft MSL (10527 ft AGL)
Lifted condensation level....... 15625 ft MSL (10332 ft AGL)
Lifted index.................... -2.8
K index......................... +26.1
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 -62.6 -80.7 240 50 26 -0.2 -0.1 M M M M M
45000 -61.3 -78.3 245 68 35 4.2 2.3 M M M M M
40000 -54.8 -66.6 245 68 35 8.2 4.5 M M M M M
38000 -50.1 -58.2 240 65 34 7.9 4.3 M M M M M
36000 -44.8 -48.6 235 63 32 7.9 4.4 M M M M M
34000 -40.5 -40.9 230 58 30 6.9 3.8 M M M M M
32000 -36.3 -33.3 230 53 27 6.9 3.8 M M M M M
30000 -32.4 -26.3 225 49 25 6.6 3.6 43.2 109.7 9.6 M M
29000 -30.4 -22.7 225 46 24 6.6 3.6 42.0 107.5 8.8 M M
28000 -28.4 -19.1 225 44 23 6.8 3.7 40.9 105.6 8.0 M M
27000 -26.0 -14.8 225 42 22 8.2 4.5 40.1 104.2 7.5 M M
26000 -23.6 -10.5 225 40 21 8.3 4.5 39.5 103.1 7.1 M M
25000 -21.1 -6.0 220 39 20 8.3 4.5 39.1 102.3 6.8 M M
24000 -18.7 -1.7 220 37 19 7.9 4.3 38.4 101.1 6.3 M M
23000 -16.3 2.7 215 35 18 7.9 4.3 37.7 99.8 5.8 M M
22000 -14.0 6.8 210 33 17 8.0 4.4 37.1 98.7 5.3 M M
21000 -11.8 10.8 210 31 16 7.1 3.9 36.2 97.1 4.6 M M
20000 -9.8 14.4 205 29 15 7.3 4.0 35.3 95.5 3.7 M M
19500 -8.8 16.2 205 28 14 7.4 4.1 34.9 94.7 3.3 M M
19000 -7.8 18.0 205 27 14 7.8 4.3 34.5 94.1 2.9 M M
18500 -6.6 20.1 205 26 13 8.1 4.5 34.2 93.6 2.6 M M
18000 -5.4 22.3 210 25 13 8.3 4.6 33.9 93.1 2.3 M M
17500 -3.8 25.2 215 23 12 7.1 3.9 33.4 92.0 1.8 M M
17000 -2.7 27.1 220 22 11 7.0 3.8 32.9 91.2 1.4 M M
16500 -1.6 29.1 225 21 11 7.9 4.4 32.5 90.5 1.1 M M
16000 -0.5 31.1 225 20 10 7.9 4.3 32.2 90.0 0.7 M M
15500 0.7 33.3 230 18 9 7.5 4.1 31.9 89.4 0.4 M M
15000 1.8 35.2 230 17 9 7.4 4.1 31.5 88.7 0.1 M M
14500 2.9 37.2 230 15 8 7.4 4.0 31.1 88.0 -0.3 772 3.9
14000 4.0 39.2 225 13 7 7.3 4.0 30.7 87.2 -0.7 725 3.7
13500 5.1 41.2 225 12 6 7.3 4.0 30.3 86.5 -1.0 678 3.4
13000 6.2 43.2 225 11 6 8.0 4.4 30.0 85.9 -1.4 628 3.2
12500 7.4 45.3 225 10 5 8.0 4.4 29.7 85.4 -1.6 578 2.9
12000 8.5 47.3 225 9 4 7.7 4.2 29.4 84.9 -2.0 529 2.7
11500 9.6 49.3 230 8 4 7.8 4.3 29.0 84.3 -2.3 481 2.4
11000 10.7 51.3 235 7 4 6.4 3.5 28.6 83.5 -2.8 435 2.2
10500 11.6 52.9 240 7 3 6.0 3.3 28.1 82.6 -3.3 392 2.0
10250 12.1 53.8 240 6 3 9.3 5.1 27.9 82.2 -3.6 370 1.9
10000 12.9 55.2 245 6 3 9.2 5.1 28.0 82.3 -3.5 340 1.7
9750 13.3 55.9 250 6 3 6.1 3.3 27.7 81.9 -3.8 318 1.6
9500 13.8 56.8 250 6 3 6.7 3.7 27.5 81.5 -4.0 296 1.5
9250 14.3 57.7 255 6 3 7.3 4.0 27.3 81.1 -4.3 274 1.4
9000 14.9 58.8 255 6 3 7.7 4.2 27.1 80.8 -4.5 249 1.3
8750 15.4 59.7 255 7 4 7.2 3.9 26.9 80.4 -4.7 226 1.1
8500 15.9 60.6 255 7 4 7.1 3.9 26.7 80.1 -4.9 203 1.0
8250 16.5 61.7 255 8 4 8.2 4.5 26.5 79.8 -5.1 179 0.9
8000 17.1 62.8 255 8 4 8.3 4.5 26.5 79.6 -5.2 153 0.8
7750 17.6 63.7 255 9 5 6.9 3.8 26.3 79.3 -5.4 130 0.7
7500 18.1 64.6 250 10 5 6.7 3.7 26.0 78.9 -5.7 108 0.5
7250 18.6 65.5 250 10 5 5.0 2.7 25.8 78.4 -6.0 87 0.4
7000 18.9 66.0 250 10 5 3.5 1.9 25.3 77.6 -6.4 71 0.4
6750 19.1 66.4 250 10 5 3.6 2.0 24.8 76.7 -6.9 55 0.3
6500 19.3 66.7 250 9 5 -0.5 -0.3 24.3 75.7 -7.5 42 0.2
6250 19.0 66.2 250 9 5 -5.9 -3.3 23.3 73.9 -8.5 44 0.2
6000 18.5 65.3 245 9 5 -6.4 -3.5 22.0 71.7 -9.8 51 0.3
5750 18.0 64.4 240 9 5 -7.8 -4.3 20.8 69.4 -11.0 60 0.3
5500 17.2 63.0 225 8 4 -12.7 -7.0 19.3 66.7 -12.6 76 0.4
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
09/17/2024 at 0900 MDT | 09/17/2024 at 1200 MDT
|
CAPE... +2.9 LI... -0.2 | CAPE... +316.3 LI... -1.1
CINH... -137.3 K Index... +21.4 | CINH... -61.7 K Index... +16.1
|
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 -60.9 -77.6 240 53 27 -0.2 -0.1 | -60.6 -77.1 235 48 25 0.9 0.5
45000 -60.0 -76.0 240 68 35 3.2 1.8 | -58.5 -73.3 235 69 35 2.9 1.6
40000 -54.4 -65.9 240 68 35 8.0 4.4 | -53.7 -64.7 235 72 37 7.1 3.9
38000 -49.8 -57.6 235 65 33 7.8 4.3 | -49.6 -57.3 230 69 36 6.7 3.7
36000 -45.1 -49.2 230 62 32 7.7 4.2 | -45.6 -50.1 225 66 34 6.7 3.7
34000 -40.8 -41.4 225 60 31 7.0 3.9 | -41.2 -42.2 220 64 33 7.5 4.1
32000 -36.6 -33.9 225 57 29 7.0 3.9 | -36.8 -34.2 220 62 32 7.5 4.1
30000 -32.6 -26.7 220 53 27 6.4 3.5 | -32.8 -27.0 215 60 31 6.2 3.4
29000 -30.7 -23.3 220 50 26 6.4 3.5 | -30.5 -22.9 210 58 30 6.2 3.4
28000 -28.4 -19.1 220 47 24 7.2 3.9 | -28.6 -19.5 210 56 29 6.6 3.6
27000 -25.9 -14.6 215 46 24 8.5 4.7 | -26.2 -15.2 205 54 28 8.2 4.5
26000 -23.3 -9.9 210 46 24 8.5 4.7 | -23.7 -10.7 205 53 27 8.2 4.5
25000 -20.7 -5.3 210 45 23 8.7 4.8 | -21.3 -6.3 200 51 26 8.3 4.5
24000 -18.4 -1.1 205 44 23 7.4 4.1 | -19.0 -2.2 200 49 25 7.3 4.0
23000 -16.2 2.8 205 42 22 7.4 4.1 | -16.8 1.8 200 47 24 7.3 4.0
22000 -14.0 6.8 200 40 21 7.5 4.1 | -14.7 5.5 195 45 23 7.4 4.0
21000 -12.1 10.2 200 38 19 6.5 3.6 | -12.5 9.5 195 42 22 7.3 4.0
20000 -10.2 13.6 195 35 18 6.7 3.7 | -10.3 13.5 200 39 20 7.3 4.0
19500 -9.2 15.4 195 34 18 6.8 3.7 | -9.2 15.4 200 38 20 7.3 4.0
19000 -8.3 17.1 195 33 17 7.8 4.3 | -8.2 17.2 200 37 19 7.6 4.2
18500 -7.0 19.4 195 32 16 8.4 4.6 | -7.0 19.4 200 35 18 7.9 4.3
18000 -5.7 21.7 195 31 16 8.5 4.7 | -5.8 21.6 200 34 17 7.9 4.3
17500 -4.6 23.7 200 30 15 6.9 3.8 | -4.6 23.7 200 33 17 8.8 4.8
17000 -3.6 25.5 200 29 15 7.1 3.9 | -3.3 26.1 200 33 17 8.7 4.8
16500 -2.6 27.3 205 28 14 7.7 4.2 | -2.0 28.4 205 32 17 8.2 4.5
16000 -1.4 29.5 205 26 14 8.0 4.4 | -0.9 30.4 205 32 16 7.6 4.2
15500 -0.2 31.6 205 25 13 8.1 4.4 | 0.2 32.4 205 31 16 7.6 4.2
15000 1.0 33.8 210 24 13 8.3 4.5 | 1.7 35.1 210 30 15 7.0 3.8
14500 2.8 37.0 215 24 12 8.0 4.4 | 2.7 36.9 215 29 15 7.0 3.8
14000 3.9 39.0 220 23 12 7.7 4.2 | 3.7 38.7 215 28 15 7.1 3.9
13500 5.0 41.0 220 22 11 7.9 4.3 | 4.7 40.5 220 28 14 7.2 3.9
13000 6.2 43.2 220 21 11 8.8 4.8 | 5.6 42.1 225 27 14 6.6 3.6
12500 7.5 45.5 220 20 10 8.8 4.8 | 6.6 43.9 225 26 13 6.6 3.6
12000 8.7 47.7 220 18 9 8.5 4.7 | 7.6 45.7 225 24 12 8.0 4.4
11500 10.0 50.0 220 17 9 8.9 4.9 | 8.7 47.7 220 22 11 7.9 4.4
11000 11.0 51.8 215 15 8 5.5 3.0 | 9.9 49.8 215 20 10 8.3 4.6
10500 11.8 53.2 215 13 6 6.7 3.7 | 11.1 52.0 210 18 9 9.0 5.0
10250 12.4 54.3 215 11 6 9.1 5.0 | 11.9 53.4 205 17 9 10.3 5.7
10000 13.0 55.4 215 9 5 7.7 4.2 | 12.6 54.7 200 16 8 8.8 4.8
9750 13.5 56.3 215 8 4 6.3 3.4 | 13.2 55.8 200 15 8 7.7 4.2
9500 14.0 57.2 215 7 4 6.7 3.7 | 13.7 56.7 200 15 8 7.9 4.3
9250 14.4 57.9 215 6 3 6.4 3.5 | 14.3 57.7 200 14 7 8.1 4.5
9000 14.9 58.8 220 5 3 6.7 3.7 | 14.9 58.8 200 13 7 8.1 4.4
8750 15.4 59.7 220 5 2 7.1 3.9 | 15.4 59.7 200 12 6 8.0 4.4
8500 15.9 60.6 225 4 2 7.0 3.8 | 16.0 60.8 195 11 6 7.4 4.1
8250 16.4 61.5 225 4 2 6.6 3.6 | 16.5 61.7 195 10 5 9.9 5.4
8000 16.9 62.4 230 4 2 6.3 3.5 | 17.3 63.1 195 10 5 11.2 6.1
7750 17.3 63.1 235 4 2 6.7 3.7 | 18.0 64.4 195 10 5 9.5 5.2
7500 17.8 64.0 235 4 2 6.3 3.4 | 18.8 65.8 195 10 5 9.8 5.4
7250 18.2 64.8 235 4 2 4.5 2.5 | 19.5 67.1 195 9 5 10.3 5.6
7000 18.4 65.1 235 5 2 3.3 1.8 | 20.3 68.5 195 9 5 10.4 5.7
6750 18.7 65.7 235 5 3 2.6 1.4 | 21.0 69.8 195 9 5 9.1 5.0
6500 18.8 65.8 235 5 3 1.6 0.9 | 21.7 71.1 195 9 5 9.5 5.2
6250 18.9 66.0 230 6 3 1.3 0.7 | 22.5 72.5 195 9 4 11.2 6.1
6000 18.9 66.0 230 6 3 1.0 0.5 | 23.3 73.9 200 8 4 12.2 6.7
5750 19.0 66.2 225 6 3 2.0 1.1 | 24.2 75.6 200 8 4 9.5 5.2
5500 19.3 66.7 215 6 3 10.0 5.5 | 24.9 76.8 200 8 4 13.7 7.5
09/17/2024 at 1500 MDT | 09/17/2024 at 1800 MDT
|
CAPE... +260.4 LI... -1.1 | CAPE... +570.9 LI... -2.1
CINH... -25.5 K Index... +31.2 | CINH... -80.6 K Index... +12.0
|
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 -59.9 -75.8 235 46 24 2.3 1.3 | -60.7 -77.3 230 40 21 1.6 0.9
45000 -56.7 -70.1 240 69 36 1.5 0.8 | -57.7 -71.9 235 58 30 3.7 2.0
40000 -54.1 -65.4 235 94 49 6.3 3.4 | -51.8 -61.2 220 67 34 4.7 2.6
38000 -50.5 -58.9 230 90 46 6.0 3.3 | -49.0 -56.2 215 65 34 4.7 2.6
36000 -46.9 -52.4 225 86 44 6.0 3.3 | -46.1 -51.0 210 64 33 4.7 2.6
34000 -42.3 -44.1 220 81 42 8.3 4.6 | -42.3 -44.1 205 62 32 7.3 4.0
32000 -37.4 -35.3 220 75 39 8.3 4.6 | -37.9 -36.2 200 61 31 7.3 4.0
30000 -32.9 -27.2 215 69 35 7.0 3.9 | -33.3 -27.9 200 61 31 8.2 4.5
29000 -30.8 -23.4 210 66 34 7.0 3.9 | -30.8 -23.4 195 61 31 8.2 4.5
28000 -28.7 -19.7 205 63 32 7.0 3.8 | -27.7 -17.9 195 62 32 8.2 4.5
27000 -25.7 -14.3 205 59 31 8.5 4.7 | -25.2 -13.4 190 61 31 8.7 4.8
26000 -23.2 -9.8 200 56 29 8.6 4.7 | -22.7 -8.9 190 60 31 8.8 4.8
25000 -20.7 -5.3 200 53 27 8.6 4.7 | -20.1 -4.2 185 59 30 8.9 4.9
24000 -18.4 -1.1 200 50 26 7.3 4.0 | -17.8 -0.0 185 59 30 7.1 3.9
23000 -16.3 2.7 195 46 24 7.3 4.0 | -15.7 3.7 190 59 31 7.0 3.8
22000 -14.1 6.6 195 42 22 7.4 4.0 | -13.6 7.5 195 60 31 7.0 3.9
21000 -12.1 10.2 195 39 20 7.2 4.0 | -11.7 10.9 200 60 31 5.7 3.1
20000 -10.0 14.0 200 37 19 7.3 4.0 | -9.9 14.2 210 59 31 5.7 3.1
19500 -8.9 16.0 200 35 18 7.3 4.0 | -9.0 15.8 215 59 31 5.7 3.1
19000 -7.9 17.8 200 34 18 7.1 3.9 | -8.2 17.2 215 60 31 5.8 3.2
18500 -6.9 19.6 200 34 17 6.8 3.7 | -7.2 19.0 220 59 30 6.3 3.5
18000 -5.9 21.4 195 33 17 6.8 3.7 | -6.3 20.7 225 57 29 6.3 3.4
17500 -4.9 23.2 195 33 17 7.1 3.9 | -5.4 22.3 225 55 28 6.7 3.7
17000 -3.9 25.0 195 32 17 7.1 3.9 | -4.3 24.3 230 53 27 6.8 3.7
16500 -2.9 26.8 200 32 16 7.1 3.9 | -3.3 26.1 230 51 26 6.7 3.7
16000 -1.8 28.8 200 32 17 7.1 3.9 | -2.4 27.7 235 51 26 5.8 3.2
15500 -0.8 30.6 200 33 17 7.1 3.9 | -1.6 29.1 235 51 26 5.8 3.2
15000 0.3 32.5 200 33 17 7.4 4.1 | -0.7 30.7 240 51 26 7.0 3.9
14500 1.4 34.5 200 32 16 7.4 4.1 | 0.3 32.5 240 50 26 7.2 4.0
14000 2.4 36.3 200 31 16 7.0 3.8 | 1.9 35.4 245 48 25 9.1 5.0
13500 3.5 38.3 200 30 15 7.0 3.8 | 3.2 37.8 245 44 23 8.9 4.9
13000 4.6 40.3 195 28 15 7.8 4.3 | 4.5 40.1 245 40 21 9.6 5.3
12500 5.8 42.4 190 27 14 8.5 4.7 | 5.9 42.6 245 35 18 9.7 5.3
12000 7.7 45.9 185 25 13 9.3 5.1 | 7.2 45.0 245 31 16 8.5 4.7
11500 9.0 48.2 185 25 13 9.4 5.2 | 8.4 47.1 245 29 15 8.3 4.6
11000 10.3 50.5 185 24 13 8.4 4.6 | 9.5 49.1 250 28 14 5.8 3.2
10500 11.6 52.9 185 24 12 9.5 5.2 | 10.2 50.4 250 28 14 4.7 2.6
10250 12.4 54.3 185 24 12 12.6 6.9 | 10.5 50.9 250 28 14 6.6 3.6
10000 13.3 55.9 185 24 12 11.0 6.0 | 11.0 51.8 245 28 14 6.8 3.8
9750 14.0 57.2 185 24 12 9.2 5.1 | 11.4 52.5 245 27 14 5.3 2.9
9500 14.7 58.5 190 24 12 9.4 5.2 | 11.8 53.2 240 27 14 5.6 3.1
9250 15.5 59.9 190 23 12 10.5 5.8 | 12.1 53.8 240 27 14 5.9 3.2
9000 16.3 61.3 190 23 12 10.6 5.8 | 12.6 54.7 240 27 14 7.0 3.9
8750 17.0 62.6 190 23 12 9.5 5.2 | 13.1 55.6 235 27 14 7.6 4.2
8500 17.7 63.9 190 23 12 9.6 5.3 | 13.6 56.5 235 27 14 7.3 4.0
8250 18.5 65.3 190 23 12 10.1 5.5 | 14.2 57.6 230 27 14 8.2 4.5
8000 19.2 66.6 190 23 12 10.2 5.6 | 14.7 58.5 230 26 13 8.0 4.4
7750 20.0 68.0 190 23 12 9.7 5.3 | 15.2 59.4 230 26 13 6.4 3.5
7500 20.7 69.3 190 22 12 9.9 5.4 | 15.7 60.3 225 25 13 6.8 3.7
7250 21.4 70.5 190 22 11 9.6 5.3 | 16.1 61.0 225 25 13 5.4 2.9
7000 22.1 71.8 190 22 11 9.5 5.2 | 16.4 61.5 220 24 12 3.8 2.1
6750 22.8 73.0 190 22 11 9.9 5.4 | 16.6 61.9 215 22 11 4.5 2.5
6500 23.6 74.5 190 21 11 9.9 5.5 | 16.9 62.4 215 19 10 4.8 2.6
6250 24.3 75.7 190 21 11 9.8 5.4 | 17.2 63.0 210 17 9 8.1 4.4
6000 25.1 77.2 190 20 10 9.7 5.3 | 18.0 64.4 205 15 8 10.7 5.9
5750 25.8 78.4 190 19 10 10.9 6.0 | 18.7 65.7 205 14 7 9.7 5.3
5500 26.7 80.1 190 17 9 13.8 7.6 | 19.5 67.1 200 12 6 13.1 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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