Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
314
UXUS97 KBOU 201344
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0741 MDT Monday, May 20, 2024
This forecast is for Monday, May 20, 2024:
If the trigger temperature of 60.4 F/15.8 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 600 ft/min (3.1 m/s)
Maximum height of thermals.................. 14051 ft MSL (8750 ft AGL)
Forecast maximum temperature................... 76.0 F/24.9 C
Time of trigger temperature.................... 1030 MDT
Time of overdevelopment........................ 1400 MDT
Middle/high clouds during soaring window....... None
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 10961 ft MSL (5660 ft AGL)
Thermal soaring outlook for Tuesday 05/21...... Fair
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1800 MDT)......... Little change
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1800 MDT)................ Weak PVA
Potential height of wave....................... 17386 ft MSL (12085 ft AGL)
Wave soaring outlook for Tuesday 05/21......... Fair
Remarks...
Sunrise/Sunset.................... 05:39:53 / 20:12:16 MDT
Total possible sunshine........... 14 hr 32 min 23 sec (872 min 23 sec)
Altitude of sun at 12:56:05 MDT... 70.41 degrees
Upper air data from numerical model forecast valid on 05/20/2024 at 0600 MDT
Freezing level.................. 13023 ft MSL (7722 ft AGL)
Convective condensation level... 12645 ft MSL (7344 ft AGL)
Lifted condensation level....... 13389 ft MSL (8089 ft AGL)
Lifted index.................... -4.0
K index......................... +20.2
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 -55.5 -67.9 250 51 26 1.3 0.7 M M M M M
45000 -53.9 -65.0 255 62 32 -0.2 -0.1 M M M M M
40000 -54.1 -65.4 260 81 42 -0.0 -0.0 M M M M M
38000 -52.5 -62.5 260 78 40 3.8 2.1 M M M M M
36000 -49.9 -57.8 255 70 36 3.8 2.1 M M M M M
34000 -47.0 -52.6 250 61 31 6.2 3.4 M M M M M
32000 -43.2 -45.8 240 50 26 6.2 3.4 M M M M M
30000 -39.0 -38.2 235 43 22 8.1 4.4 36.9 98.5 9.4 M M
29000 -36.6 -33.9 235 42 22 8.1 4.4 36.2 97.2 9.0 M M
28000 -34.2 -29.6 235 40 21 8.1 4.4 35.7 96.2 8.7 M M
27000 -31.8 -25.2 235 39 20 7.9 4.3 35.0 95.1 8.3 M M
26000 -29.4 -20.9 240 39 20 7.9 4.3 34.2 93.6 7.8 M M
25000 -27.0 -16.6 240 39 20 7.9 4.3 33.6 92.4 7.3 M M
24000 -24.7 -12.5 245 39 20 6.6 3.6 32.9 91.2 6.8 M M
23000 -22.8 -9.0 245 38 19 6.5 3.6 31.6 88.8 5.8 M M
22000 -20.8 -5.4 245 37 19 6.5 3.6 30.4 86.8 4.9 M M
21000 -19.0 -2.2 245 35 18 6.0 3.3 29.3 84.7 4.0 M M
20000 -17.2 1.0 245 31 16 6.2 3.4 27.9 82.2 2.8 M M
19500 -16.3 2.7 245 29 15 6.2 3.4 27.3 81.1 2.3 M M
19000 -15.4 4.3 245 27 14 6.1 3.3 26.7 80.1 1.7 M M
18500 -14.3 6.3 245 26 14 9.1 5.0 26.3 79.4 1.3 M M
18000 -12.3 9.9 245 27 14 9.3 5.1 26.2 79.1 1.2 M M
17500 -11.0 12.2 245 27 14 9.2 5.0 26.1 79.0 1.1 M M
17000 -9.6 14.7 245 26 14 9.2 5.0 26.0 78.8 1.0 M M
16500 -8.2 17.2 240 26 13 9.1 5.0 25.9 78.6 0.9 M M
16000 -6.9 19.6 235 26 13 9.1 5.0 25.8 78.4 0.8 M M
15500 -5.5 22.1 235 26 14 9.0 4.9 25.7 78.2 0.7 M M
15000 -4.2 24.4 230 26 14 7.8 4.3 25.4 77.8 0.5 M M
14500 -3.0 26.6 220 26 13 8.0 4.4 25.1 77.2 0.2 M M
14000 -1.9 28.6 215 25 13 7.2 4.0 24.8 76.6 -0.1 589 3.0
13500 -0.9 30.4 210 24 12 7.3 4.0 24.4 75.8 -0.5 543 2.8
13000 0.2 32.4 200 23 12 6.7 3.7 23.9 75.1 -1.0 498 2.5
12500 1.1 34.0 190 23 12 6.7 3.7 23.4 74.2 -1.6 456 2.3
12000 2.0 35.6 180 22 11 7.5 4.1 23.0 73.3 -2.1 413 2.1
11500 3.1 37.6 175 20 10 7.8 4.3 22.6 72.7 -2.4 365 1.9
11000 4.1 39.4 170 18 9 2.8 1.6 22.1 71.8 -3.0 321 1.6
10500 4.1 39.4 170 12 6 0.8 0.4 20.7 69.2 -4.4 305 1.6
10250 4.1 39.4 175 10 5 1.2 0.7 20.0 68.0 -5.1 298 1.5
10000 4.2 39.6 175 8 4 -0.1 -0.0 19.3 66.8 -5.8 288 1.5
9750 4.0 39.2 175 6 3 -1.4 -0.8 18.4 65.2 -6.7 285 1.4
9500 3.9 39.0 185 4 2 -1.6 -0.9 17.6 63.6 -7.6 282 1.4
9250 3.8 38.8 215 1 1 0.7 0.4 16.7 62.1 -8.5 278 1.4
9000 4.0 39.2 000 0 0 6.4 3.5 16.2 61.2 -9.0 264 1.3
8750 4.5 40.1 100 2 1 7.7 4.2 16.1 60.9 -9.2 240 1.2
8500 5.1 41.2 095 5 2 9.7 5.3 15.9 60.7 -9.4 216 1.1
8250 5.7 42.3 095 8 4 1.1 0.6 15.8 60.4 -9.6 192 1.0
8000 5.2 41.4 080 10 5 -8.6 -4.7 14.6 58.2 -10.8 197 1.0
7750 4.8 40.6 070 12 6 -5.5 -3.0 13.3 55.9 -12.0 204 1.0
7500 4.5 40.1 065 12 6 -3.3 -1.8 12.2 54.0 -13.1 206 1.0
7250 4.4 39.9 055 12 6 3.5 1.9 11.4 52.5 -13.9 200 1.0
7000 4.9 40.8 050 11 6 8.4 4.6 11.2 52.1 -14.2 178 0.9
6750 5.4 41.7 040 10 5 4.1 2.3 11.0 51.7 -14.4 156 0.8
6500 5.6 42.1 030 10 5 5.2 2.9 10.5 50.8 -15.0 141 0.7
6250 6.3 43.3 025 9 5 9.3 5.1 10.3 50.6 -15.1 115 0.6
6000 6.9 44.4 015 8 4 8.5 4.7 10.3 50.5 -15.2 88 0.4
5750 7.6 45.7 005 8 4 9.7 5.3 10.2 50.4 -15.3 60 0.3
5500 8.4 47.1 360 7 4 12.9 7.1 10.3 50.6 -15.3 28 0.1
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
05/20/2024 at 0900 MDT | 05/20/2024 at 1200 MDT
|
CAPE... +1.7 LI... +0.1 | CAPE... 0.0 LI... +1.4
CINH... 0.0 K Index... +21.1 | CINH... 0.0 K Index... +5.3
|
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 -56.0 -68.8 240 47 24 1.4 0.8 | -55.5 -67.9 240 50 26 0.9 0.5
45000 -54.2 -65.6 245 61 31 0.1 0.0 | -54.3 -65.7 240 65 33 -0.1 -0.1
40000 -54.2 -65.6 255 75 39 0.2 0.1 | -54.5 -66.1 255 81 42 -0.0 -0.0
38000 -52.2 -62.0 255 79 41 4.3 2.4 | -52.4 -62.3 255 87 45 4.6 2.5
36000 -49.2 -56.6 255 82 42 4.4 2.4 | -49.3 -56.7 255 94 48 4.6 2.5
34000 -46.1 -51.0 255 80 41 6.0 3.3 | -46.0 -50.8 255 93 48 6.3 3.4
32000 -42.5 -44.5 255 71 36 6.0 3.3 | -42.3 -44.1 255 86 44 6.3 3.4
30000 -38.8 -37.8 250 61 31 6.3 3.5 | -38.3 -36.9 255 78 40 7.1 3.9
29000 -36.9 -34.4 245 55 28 6.3 3.5 | -36.1 -33.0 255 73 38 7.1 3.9
28000 -35.0 -31.0 245 49 25 6.3 3.5 | -34.0 -29.2 255 68 35 7.1 3.9
27000 -33.0 -27.4 240 46 23 7.9 4.4 | -31.9 -25.4 255 63 32 6.2 3.4
26000 -30.6 -23.1 240 45 23 7.8 4.3 | -30.1 -22.2 250 58 30 6.3 3.5
25000 -28.3 -18.9 240 44 22 7.8 4.3 | -28.2 -18.8 250 53 27 6.3 3.5
24000 -25.9 -14.6 245 43 22 8.1 4.4 | -26.2 -15.2 250 48 25 9.1 5.0
23000 -23.5 -10.3 245 42 22 8.1 4.4 | -23.4 -10.1 245 45 23 9.3 5.1
22000 -21.1 -6.0 245 41 21 8.1 4.4 | -20.5 -4.9 245 42 22 9.3 5.1
21000 -18.7 -1.7 245 40 21 7.4 4.0 | -17.9 -0.2 245 41 21 7.5 4.1
20000 -16.5 2.3 245 38 20 7.4 4.1 | -15.6 3.9 245 43 22 7.6 4.2
19500 -15.4 4.3 245 37 19 7.4 4.1 | -14.4 6.1 245 45 23 7.6 4.2
19000 -14.3 6.3 245 36 18 7.6 4.1 | -13.3 8.1 245 46 24 7.7 4.2
18500 -12.8 9.0 240 33 17 6.0 3.3 | -11.6 11.1 245 45 23 7.2 3.9
18000 -12.0 10.4 235 31 16 6.0 3.3 | -10.5 13.1 245 42 22 7.2 3.9
17500 -11.1 12.0 235 29 15 6.8 3.8 | -9.4 15.1 245 39 20 7.5 4.1
17000 -10.1 13.8 230 28 14 7.1 3.9 | -8.3 17.1 240 37 19 7.5 4.1
16500 -9.1 15.6 230 27 14 8.3 4.5 | -7.2 19.0 240 34 18 7.5 4.1
16000 -7.7 18.1 230 26 13 9.4 5.2 | -6.1 21.0 235 34 18 7.5 4.1
15500 -6.3 20.7 225 26 13 9.5 5.2 | -5.0 23.0 235 34 18 7.5 4.1
15000 -4.8 23.4 225 26 13 9.6 5.2 | -4.0 24.8 235 34 17 7.0 3.8
14500 -3.4 25.9 225 26 13 9.6 5.3 | -3.0 26.6 230 33 17 7.2 3.9
14000 -2.0 28.4 225 26 13 9.4 5.2 | -1.9 28.6 225 32 17 8.2 4.5
13500 -0.6 30.9 220 26 13 9.5 5.2 | -0.7 30.7 220 30 16 8.2 4.5
13000 0.8 33.4 215 26 14 8.2 4.5 | 0.5 32.9 220 29 15 9.3 5.1
12500 2.0 35.6 210 26 13 8.1 4.4 | 1.9 35.4 215 28 14 9.6 5.3
12000 3.1 37.6 200 26 14 7.4 4.1 | 3.4 38.1 215 26 14 9.0 5.0
11500 4.1 39.4 195 27 14 7.3 4.0 | 4.7 40.5 215 25 13 8.7 4.8
11000 5.1 41.2 190 27 14 7.0 3.8 | 5.9 42.6 215 24 13 7.8 4.3
10500 6.0 42.8 185 24 13 7.2 4.0 | 7.0 44.6 210 24 12 6.9 3.8
10250 6.5 43.7 180 23 12 5.2 2.8 | 7.5 45.5 210 23 12 8.7 4.8
10000 6.6 43.9 180 23 12 -4.3 -2.4 | 8.2 46.8 205 23 12 6.6 3.6
9750 5.9 42.6 180 20 10 -9.1 -5.0 | 8.4 47.1 205 22 11 3.2 1.7
9500 5.2 41.4 185 17 9 -8.1 -4.5 | 8.6 47.5 200 21 11 4.3 2.4
9250 4.6 40.3 190 15 7 -7.1 -3.9 | 8.8 47.8 195 20 10 3.8 2.1
9000 4.2 39.6 195 12 6 -2.0 -1.1 | 8.9 48.0 195 19 10 -4.3 -2.4
8750 4.1 39.4 200 10 5 0.9 0.5 | 8.1 46.6 190 16 8 -10.5 -5.8
8500 4.2 39.6 210 8 4 1.4 0.7 | 7.4 45.3 190 14 7 -9.2 -5.1
8250 4.2 39.6 220 6 3 -0.6 -0.3 | 6.6 43.9 185 11 6 -9.4 -5.2
8000 4.0 39.2 210 4 2 -3.1 -1.7 | 5.9 42.6 165 8 4 -6.3 -3.5
7750 3.9 39.0 175 3 1 -2.3 -1.3 | 5.7 42.3 135 7 4 2.2 1.2
7500 3.7 38.7 150 2 1 -1.3 -0.7 | 6.0 42.8 125 7 4 5.0 2.7
7250 3.8 38.8 115 2 1 4.6 2.5 | 6.4 43.5 115 8 4 7.8 4.3
7000 4.4 39.9 080 2 1 8.7 4.8 | 7.2 45.0 115 8 4 12.2 6.7
6750 4.9 40.8 055 3 1 7.1 3.9 | 8.1 46.6 110 8 4 9.7 5.3
6500 5.5 41.9 055 3 2 8.7 4.8 | 8.8 47.8 110 8 4 9.7 5.3
6250 6.2 43.2 050 3 2 10.7 5.8 | 9.6 49.3 110 8 4 11.4 6.2
6000 7.0 44.6 050 3 2 10.4 5.7 | 10.4 50.7 110 8 4 12.5 6.9
5750 7.8 46.0 050 3 2 11.1 6.1 | 11.3 52.3 105 7 4 9.8 5.4
5500 8.7 47.7 050 3 2 14.0 7.7 | 12.1 53.8 105 7 4 15.0 8.2
05/20/2024 at 1500 MDT | 05/20/2024 at 1800 MDT
|
CAPE... +376.1 LI... -2.2 | CAPE... +512.7 LI... -4.0
CINH... -144.0 K Index... +29.0 | CINH... -110.0 K Index... +34.6
|
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 -56.6 -69.9 240 47 24 1.6 0.9 | -55.5 -67.9 240 43 22 2.2 1.2
45000 -54.4 -65.9 240 66 34 0.7 0.4 | -52.4 -62.3 240 62 32 0.5 0.3
40000 -53.3 -63.9 250 81 42 0.8 0.4 | -51.7 -61.1 240 78 40 0.5 0.3
38000 -51.4 -60.5 250 89 46 3.9 2.1 | -51.0 -59.8 240 87 45 1.4 0.8
36000 -49.1 -56.4 245 96 50 3.9 2.1 | -50.2 -58.4 240 99 51 1.4 0.8
34000 -45.9 -50.6 245 100 51 6.0 3.3 | -48.0 -54.4 240 104 54 6.5 3.6
32000 -42.3 -44.1 245 96 50 5.9 3.3 | -44.1 -47.4 240 99 51 6.4 3.5
30000 -38.5 -37.3 245 89 46 6.8 3.7 | -39.8 -39.6 240 91 47 8.2 4.5
29000 -36.5 -33.7 245 83 42 6.8 3.7 | -37.4 -35.3 240 85 44 8.2 4.5
28000 -34.4 -29.9 245 76 39 6.8 3.7 | -34.9 -30.8 240 79 41 8.2 4.5
27000 -32.4 -26.3 245 70 36 6.6 3.6 | -32.5 -26.5 240 73 38 7.3 4.0
26000 -30.4 -22.7 245 65 33 6.7 3.7 | -30.3 -22.5 240 67 34 7.4 4.0
25000 -28.4 -19.1 245 59 31 6.7 3.7 | -28.1 -18.6 245 60 31 7.4 4.0
24000 -26.3 -15.3 240 54 28 8.7 4.8 | -25.9 -14.6 245 54 28 8.6 4.7
23000 -23.6 -10.5 240 51 26 9.1 5.0 | -23.2 -9.8 240 50 26 8.9 4.9
22000 -21.0 -5.8 240 48 24 9.1 5.0 | -20.6 -5.1 230 47 24 9.0 4.9
21000 -18.3 -0.9 235 45 23 7.8 4.3 | -18.0 -0.4 225 44 23 7.5 4.1
20000 -16.0 3.2 235 43 22 8.0 4.4 | -15.8 3.6 220 44 23 7.6 4.2
19500 -14.8 5.4 235 42 22 8.0 4.4 | -14.7 5.5 215 44 23 7.6 4.2
19000 -13.6 7.5 235 41 21 8.0 4.4 | -13.6 7.5 215 44 23 7.7 4.2
18500 -11.8 10.8 235 40 21 7.6 4.2 | -12.5 9.5 210 44 23 7.2 4.0
18000 -10.7 12.7 235 39 20 7.6 4.2 | -11.4 11.5 210 43 22 7.1 3.9
17500 -9.6 14.7 235 38 20 8.1 4.5 | -10.4 13.3 210 43 22 7.0 3.9
17000 -8.4 16.9 235 37 19 8.3 4.5 | -8.9 16.0 205 42 22 6.9 3.8
16500 -7.2 19.0 235 37 19 8.3 4.5 | -7.9 17.8 205 42 22 7.2 3.9
16000 -6.0 21.2 230 36 19 8.1 4.5 | -6.8 19.8 205 41 21 8.0 4.4
15500 -4.8 23.4 225 35 18 8.0 4.4 | -5.6 21.9 200 40 21 7.9 4.3
15000 -3.6 25.5 225 35 18 9.4 5.2 | -4.4 24.1 195 39 20 9.0 5.0
14500 -2.2 28.0 220 34 18 9.3 5.1 | -3.1 26.4 195 37 19 9.0 4.9
14000 -0.8 30.6 220 34 17 9.5 5.2 | -1.9 28.6 190 36 19 8.7 4.8
13500 0.6 33.1 215 33 17 9.5 5.2 | -0.6 30.9 185 35 18 8.7 4.7
13000 2.0 35.6 215 32 16 8.8 4.8 | 0.6 33.1 180 33 17 8.9 4.9
12500 3.2 37.8 210 31 16 8.4 4.6 | 1.9 35.4 180 32 16 9.1 5.0
12000 4.5 40.1 205 31 16 7.8 4.3 | 3.2 37.8 175 31 16 8.7 4.8
11500 5.5 41.9 200 29 15 7.2 4.0 | 4.4 39.9 170 27 14 8.1 4.5
11000 6.4 43.5 195 29 15 6.1 3.4 | 5.6 42.1 165 24 12 7.2 3.9
10500 7.0 44.6 190 28 14 4.2 2.3 | 6.4 43.5 155 20 10 5.5 3.0
10250 7.3 45.1 185 27 14 6.6 3.6 | 6.8 44.2 150 19 10 5.9 3.3
10000 7.7 45.9 180 27 14 3.6 2.0 | 7.2 45.0 145 17 9 5.8 3.2
9750 7.6 45.7 180 24 12 -2.3 -1.2 | 7.6 45.7 140 15 8 5.2 2.8
9500 7.5 45.5 175 20 10 -0.3 -0.2 | 8.0 46.4 130 13 7 5.3 2.9
9250 7.4 45.3 170 17 9 -5.1 -2.8 | 8.4 47.1 120 12 6 5.0 2.8
9000 6.9 44.4 165 14 7 0.2 0.1 | 8.8 47.8 115 11 6 4.9 2.7
8750 7.5 45.5 155 12 6 8.9 4.9 | 9.1 48.4 100 10 5 5.1 2.8
8500 8.0 46.4 140 11 5 6.2 3.4 | 9.5 49.1 090 10 5 5.0 2.7
8250 8.5 47.3 125 10 5 8.2 4.5 | 9.9 49.8 075 10 5 5.4 2.9
8000 9.2 48.6 110 10 5 11.2 6.1 | 10.4 50.7 060 11 5 6.7 3.7
7750 10.1 50.2 110 10 5 10.1 5.6 | 10.9 51.6 050 11 6 6.4 3.5
7500 10.7 51.3 105 9 5 7.9 4.4 | 11.3 52.3 040 11 6 5.4 3.0
7250 11.4 52.5 105 9 5 9.6 5.3 | 11.7 53.1 035 12 6 6.3 3.5
7000 12.2 54.0 100 9 5 11.3 6.2 | 12.3 54.1 025 13 7 7.7 4.3
6750 13.0 55.4 100 9 5 10.0 5.5 | 12.9 55.2 020 13 7 8.7 4.8
6500 13.7 56.7 095 9 5 8.6 4.7 | 13.5 56.3 015 14 7 8.8 4.8
6250 14.4 57.9 095 9 5 11.1 6.1 | 14.2 57.6 010 15 8 9.5 5.2
6000 15.3 59.5 095 9 5 13.6 7.5 | 15.0 59.0 010 15 7 10.3 5.6
5750 16.2 61.2 090 9 5 10.2 5.6 | 15.7 60.3 005 14 7 10.4 5.7
5500 17.0 62.6 090 8 4 14.6 8.0 | 16.6 61.9 005 14 7 14.3 7.8
________________________________________________________________________________
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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