Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
839
UXUS97 KBOU 010036
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1835 MDT Tuesday, April 30, 2024
This forecast is for Wednesday, May 1, 2024:
If the trigger temperature of 61.0 F/16.1 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 517 ft/min (2.6 m/s)
Maximum height of thermals.................. 12513 ft MSL (7185 ft AGL)
Forecast maximum temperature................... 70.0 F/21.6 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................. 10324 ft MSL (4996 ft AGL)
Thermal soaring outlook for Thursday 05/02..... Good
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....................... 16655 ft MSL (11327 ft AGL)
Wave soaring outlook for Thursday 05/02........ Fair
Remarks...
Sunrise/Sunset.................... 05:58:51 / 19:54:08 MDT
Total possible sunshine........... 13 hr 55 min 17 sec (835 min 17 sec)
Altitude of sun at 12:56:29 MDT... 65.62 degrees
Upper air data from numerical model forecast valid on 05/01/2024 at 0600 MDT
Freezing level.................. 12254 ft MSL (6926 ft AGL)
Convective condensation level... 14369 ft MSL (9041 ft AGL)
Lifted condensation level....... 14170 ft MSL (8842 ft AGL)
Lifted index.................... -0.6
K index......................... +20.7
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 -58.4 -73.1 250 45 23 1.7 0.9 M M M M M
45000 -56.0 -68.8 255 59 31 -1.5 -0.8 M M M M M
40000 -57.7 -71.9 255 61 32 -1.2 -0.7 M M M M M
38000 -56.2 -69.2 255 61 32 5.0 2.7 M M M M M
36000 -53.3 -63.9 250 61 31 5.0 2.7 M M M M M
34000 -49.4 -56.9 250 62 32 7.4 4.0 M M M M M
32000 -45.0 -49.0 245 64 33 7.4 4.0 M M M M M
30000 -40.4 -40.7 245 65 33 8.1 4.4 35.5 95.9 10.9 M M
29000 -38.0 -36.4 245 63 33 8.1 4.4 34.8 94.6 10.4 M M
28000 -35.5 -31.9 245 62 32 8.1 4.4 34.2 93.6 10.1 M M
27000 -33.2 -27.8 245 61 31 6.9 3.8 33.6 92.5 9.8 M M
26000 -31.1 -24.0 245 60 31 6.8 3.7 32.3 90.2 8.9 M M
25000 -29.1 -20.4 240 59 30 6.8 3.7 31.2 88.2 8.1 M M
24000 -27.1 -16.8 240 57 30 6.8 3.7 30.3 86.5 7.4 M M
23000 -25.1 -13.2 245 55 29 6.7 3.7 29.0 84.3 6.4 M M
22000 -23.1 -9.6 250 54 28 6.7 3.7 27.9 82.3 5.6 M M
21000 -21.1 -6.0 250 52 27 6.7 3.6 26.9 80.5 4.8 M M
20000 -19.2 -2.6 250 46 23 6.7 3.7 25.8 78.4 3.8 M M
19500 -18.2 -0.8 250 42 22 6.7 3.7 25.2 77.4 3.3 M M
19000 -17.2 1.0 250 39 20 6.7 3.7 24.7 76.5 2.9 M M
18500 -15.6 3.9 250 36 18 9.0 5.0 24.1 75.4 2.4 M M
18000 -14.3 6.3 245 34 18 8.8 4.8 24.0 75.1 2.2 M M
17500 -13.0 8.6 245 33 17 8.9 4.9 23.8 74.9 2.0 M M
17000 -11.7 10.9 245 35 18 9.0 4.9 23.7 74.6 1.9 M M
16500 -10.3 13.5 245 36 18 8.9 4.9 23.5 74.4 1.8 M M
16000 -9.2 15.4 245 34 18 7.7 4.2 23.3 73.9 1.5 M M
15500 -8.0 17.6 245 32 16 7.8 4.3 22.9 73.3 1.2 M M
15000 -6.8 19.8 240 30 15 8.8 4.8 22.7 72.8 1.0 M M
14500 -5.5 22.1 240 29 15 8.8 4.8 22.5 72.5 0.8 M M
14000 -4.2 24.4 240 28 14 8.6 4.7 22.4 72.3 0.7 M M
13500 -2.9 26.8 235 27 14 8.5 4.6 22.2 71.9 0.5 M M
13000 -1.7 28.9 235 26 14 8.0 4.4 22.0 71.5 0.3 M M
12500 -0.5 31.1 235 26 13 7.6 4.2 21.6 70.9 -0.0 513 2.6
12000 0.7 33.3 235 25 13 6.8 3.7 21.3 70.3 -0.3 464 2.4
11500 1.5 34.7 230 23 12 5.5 3.0 20.6 69.1 -1.0 424 2.2
11000 2.3 36.1 230 22 11 4.6 2.5 19.9 67.9 -1.6 385 2.0
10500 2.8 37.0 225 21 11 3.1 1.7 18.9 66.1 -2.6 356 1.8
10250 3.0 37.4 225 21 11 3.6 2.0 18.4 65.1 -3.2 342 1.7
10000 3.2 37.8 220 21 11 4.5 2.5 18.0 64.4 -3.6 327 1.7
9750 3.6 38.5 215 22 11 4.5 2.5 17.6 63.6 -4.0 309 1.6
9500 3.9 39.0 210 23 12 4.3 2.4 17.1 62.8 -4.5 293 1.5
9250 4.2 39.6 205 24 12 4.4 2.4 16.7 62.1 -4.9 276 1.4
9000 4.5 40.1 200 25 13 4.8 2.6 16.3 61.4 -5.3 258 1.3
8750 4.9 40.8 195 25 13 4.6 2.5 15.9 60.7 -5.7 241 1.2
8500 5.2 41.4 195 25 13 4.1 2.3 15.5 59.9 -6.1 224 1.1
8250 5.5 41.9 190 25 13 4.5 2.5 15.1 59.1 -6.6 207 1.1
8000 5.9 42.6 190 25 13 5.1 2.8 14.7 58.5 -7.0 189 1.0
7750 6.2 43.2 185 23 12 4.3 2.3 14.3 57.8 -7.4 171 0.9
7500 6.5 43.7 185 21 11 3.4 1.9 13.9 56.9 -7.9 156 0.8
7250 6.7 44.1 185 19 10 3.7 2.0 13.4 56.1 -8.3 141 0.7
7000 7.0 44.6 185 17 9 3.9 2.1 12.9 55.3 -8.8 126 0.6
6750 7.2 45.0 190 14 7 2.4 1.3 12.4 54.4 -9.3 111 0.6
6500 7.3 45.1 190 11 6 1.1 0.6 11.8 53.2 -10.0 101 0.5
6250 7.4 45.3 190 9 5 1.5 0.8 11.2 52.1 -10.7 91 0.5
6000 7.5 45.5 190 6 3 1.1 0.6 10.5 51.0 -11.4 82 0.4
5750 7.5 45.5 185 3 1 2.4 1.3 9.9 49.8 -12.1 73 0.4
5500 7.7 45.9 090 2 1 0.3 0.2 9.3 48.8 -12.7 62 0.3
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
05/01/2024 at 0900 MDT | 05/01/2024 at 1200 MDT
|
CAPE... 0.0 LI... +1.4 | CAPE... +2.8 LI... +0.2
CINH... 0.0 K Index... +19.3 | CINH... -26.3 K Index... +25.6
|
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 -58.1 -72.6 255 42 21 0.9 0.5 | -57.9 -72.2 255 39 20 -0.3 -0.2
45000 -56.9 -70.4 255 58 30 -0.7 -0.4 | -58.3 -72.9 250 66 34 0.0 0.0
40000 -57.7 -71.9 250 66 34 -0.6 -0.3 | -58.3 -72.9 245 76 39 -0.1 -0.0
38000 -56.0 -68.8 250 67 35 5.0 2.7 | -56.1 -69.0 245 77 40 6.1 3.3
36000 -53.1 -63.6 245 67 34 5.0 2.7 | -52.5 -62.5 240 76 39 6.1 3.3
34000 -49.2 -56.6 240 66 34 7.5 4.1 | -48.7 -55.7 240 74 38 6.8 3.7
32000 -44.7 -48.5 240 63 32 7.5 4.1 | -44.1 -47.4 235 69 36 6.8 3.7
30000 -40.2 -40.4 240 60 31 7.4 4.1 | -39.8 -39.6 235 65 33 7.8 4.3
29000 -38.0 -36.4 240 58 30 7.4 4.0 | -37.4 -35.3 235 63 32 7.8 4.3
28000 -35.8 -32.4 240 57 29 7.4 4.0 | -35.1 -31.2 235 60 31 7.8 4.3
27000 -33.6 -28.5 240 56 29 6.8 3.7 | -32.8 -27.0 235 58 30 6.6 3.6
26000 -31.6 -24.9 240 54 28 6.7 3.7 | -30.9 -23.6 235 57 29 6.3 3.5
25000 -29.6 -21.3 240 53 27 6.7 3.7 | -29.0 -20.2 235 56 29 6.3 3.5
24000 -27.6 -17.7 240 51 26 7.1 3.9 | -27.1 -16.8 240 54 28 6.7 3.7
23000 -25.4 -13.7 240 50 26 7.6 4.2 | -25.0 -13.0 240 53 27 7.2 4.0
22000 -23.1 -9.6 240 49 25 7.6 4.2 | -22.8 -9.0 240 51 26 7.2 4.0
21000 -20.8 -5.4 240 48 25 7.8 4.3 | -20.6 -5.1 240 49 25 7.6 4.2
20000 -18.5 -1.3 240 46 24 7.8 4.3 | -18.3 -0.9 240 45 23 7.7 4.3
19500 -17.3 0.9 240 45 23 7.8 4.3 | -17.2 1.0 235 43 22 7.7 4.3
19000 -16.1 3.0 240 44 23 7.8 4.3 | -16.0 3.2 235 41 21 7.7 4.2
18500 -14.5 5.9 240 43 22 6.2 3.4 | -14.8 5.4 235 39 20 7.5 4.1
18000 -13.5 7.7 240 43 22 6.4 3.5 | -13.8 7.2 235 38 20 7.4 4.0
17500 -12.6 9.3 245 43 22 6.8 3.7 | -12.7 9.1 235 37 19 7.5 4.1
17000 -11.6 11.1 245 41 21 7.1 3.9 | -11.7 10.9 240 36 18 6.9 3.8
16500 -10.6 12.9 250 40 20 7.3 4.0 | -10.7 12.7 240 35 18 7.1 3.9
16000 -9.4 15.1 250 38 19 8.6 4.7 | -9.2 15.4 245 33 17 7.6 4.2
15500 -8.2 17.2 245 35 18 8.5 4.7 | -8.1 17.4 250 30 15 7.6 4.2
15000 -6.9 19.6 245 33 17 9.1 5.0 | -7.0 19.4 255 27 14 8.5 4.6
14500 -5.6 21.9 245 31 16 9.2 5.1 | -5.7 21.7 255 25 13 8.5 4.7
14000 -4.2 24.4 245 29 15 9.2 5.0 | -4.4 24.1 255 22 11 8.8 4.8
13500 -2.9 26.8 245 28 14 9.1 5.0 | -3.1 26.4 250 20 10 8.9 4.9
13000 -1.5 29.3 240 27 14 8.8 4.8 | -1.8 28.8 250 19 10 9.0 4.9
12500 -0.3 31.5 240 26 13 8.3 4.6 | -0.4 31.3 250 18 9 9.1 5.0
12000 1.0 33.8 235 25 13 8.0 4.4 | 0.9 33.6 245 16 8 8.8 4.8
11500 2.1 35.8 235 24 13 7.3 4.0 | 2.2 36.0 245 15 8 8.2 4.5
11000 3.2 37.8 235 24 12 6.4 3.5 | 3.4 38.1 245 14 7 7.7 4.2
10500 3.9 39.0 235 22 11 4.0 2.2 | 4.4 39.9 240 13 7 6.2 3.4
10250 4.2 39.6 235 22 11 4.9 2.7 | 4.9 40.8 240 13 7 8.2 4.5
10000 4.6 40.3 230 21 11 4.4 2.4 | 5.6 42.1 235 12 6 7.6 4.2
9750 4.8 40.6 230 20 10 2.2 1.2 | 6.0 42.8 230 11 6 3.7 2.0
9500 4.9 40.8 230 19 10 1.9 1.0 | 6.2 43.2 215 9 5 3.5 1.9
9250 5.0 41.0 225 17 9 1.5 0.8 | 6.4 43.5 195 9 5 2.8 1.6
9000 5.2 41.4 225 16 8 3.2 1.7 | 6.6 43.9 175 9 5 3.6 2.0
8750 5.5 41.9 220 16 8 3.9 2.1 | 7.0 44.6 170 10 5 6.4 3.5
8500 5.7 42.3 215 16 8 2.7 1.5 | 7.5 45.5 165 10 5 7.0 3.8
8250 5.9 42.6 205 17 9 3.0 1.7 | 8.0 46.4 160 10 5 7.0 3.9
8000 6.1 43.0 200 17 9 2.6 1.4 | 8.6 47.5 155 10 5 10.0 5.5
7750 6.2 43.2 195 18 9 2.2 1.2 | 9.4 48.9 155 10 5 10.7 5.9
7500 6.4 43.5 190 18 9 2.1 1.2 | 10.1 50.2 155 10 5 9.1 5.0
7250 6.5 43.7 185 18 9 1.9 1.1 | 10.8 51.4 155 10 5 9.9 5.4
7000 6.6 43.9 180 17 9 1.4 0.8 | 11.6 52.9 155 10 5 10.6 5.8
6750 6.7 44.1 175 14 7 1.9 1.0 | 12.4 54.3 150 10 5 10.3 5.7
6500 6.9 44.4 170 11 6 2.1 1.1 | 13.1 55.6 150 10 5 9.7 5.3
6250 7.1 44.8 165 9 4 6.5 3.6 | 13.9 57.0 150 9 5 10.5 5.8
6000 7.8 46.0 165 7 4 10.8 5.9 | 14.7 58.5 150 9 5 11.4 6.3
5750 8.4 47.1 165 6 3 7.8 4.3 | 15.5 59.9 150 9 4 10.6 5.8
5500 9.1 48.4 165 6 3 11.7 6.4 | 16.4 61.5 150 8 4 16.5 9.0
05/01/2024 at 1500 MDT | 05/01/2024 at 1800 MDT
|
CAPE... +410.1 LI... -2.4 | CAPE... +595.8 LI... -2.6
CINH... -32.5 K Index... +27.6 | CINH... -69.7 K Index... +27.8
|
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 -56.7 -70.1 245 32 17 0.6 0.3 | -56.3 -69.3 245 33 17 2.0 1.1
45000 -55.9 -68.6 245 58 30 -0.7 -0.4 | -53.4 -64.1 245 56 29 -1.1 -0.6
40000 -57.2 -71.0 240 77 40 -0.9 -0.5 | -56.2 -69.2 245 75 39 -1.8 -1.0
38000 -55.4 -67.7 240 81 42 5.2 2.8 | -55.1 -67.2 240 80 41 4.2 2.3
36000 -52.3 -62.1 240 82 42 5.2 2.8 | -52.6 -62.7 240 83 43 4.2 2.3
34000 -49.0 -56.2 240 82 42 6.6 3.6 | -49.7 -57.5 240 84 43 6.3 3.5
32000 -45.0 -49.0 240 78 40 6.7 3.7 | -45.9 -50.6 240 79 40 6.4 3.5
30000 -40.9 -41.6 240 74 38 7.6 4.2 | -41.9 -43.4 240 73 38 7.6 4.1
29000 -38.6 -37.5 240 72 37 7.6 4.2 | -39.7 -39.5 240 71 36 7.6 4.2
28000 -36.3 -33.3 240 70 36 7.6 4.2 | -37.4 -35.3 240 68 35 7.6 4.2
27000 -34.0 -29.2 240 68 35 7.1 3.9 | -35.1 -31.2 240 65 34 7.3 4.0
26000 -31.7 -25.1 240 65 33 6.1 3.4 | -33.1 -27.6 245 62 32 6.7 3.7
25000 -29.9 -21.8 240 63 32 6.1 3.4 | -30.6 -23.1 245 58 30 6.8 3.7
24000 -28.0 -18.4 240 61 31 6.6 3.6 | -28.5 -19.3 245 54 28 7.7 4.2
23000 -26.0 -14.8 240 56 29 7.0 3.8 | -26.1 -15.0 245 52 27 8.3 4.5
22000 -23.9 -11.0 240 51 26 7.1 3.9 | -23.6 -10.5 240 49 25 8.3 4.6
21000 -21.7 -7.1 240 47 24 8.9 4.9 | -21.2 -6.2 240 47 24 8.4 4.6
20000 -19.1 -2.4 240 42 21 9.0 5.0 | -18.7 -1.7 235 45 23 8.4 4.6
19500 -17.8 -0.0 240 39 20 9.1 5.0 | -17.5 0.5 230 44 23 8.5 4.6
19000 -16.4 2.5 240 37 19 9.1 5.0 | -16.2 2.8 230 44 22 8.5 4.7
18500 -15.1 4.8 235 34 18 8.8 4.8 | -15.0 5.0 225 43 22 8.4 4.6
18000 -13.9 7.0 235 33 17 8.6 4.7 | -13.7 7.3 225 42 21 8.4 4.6
17500 -12.6 9.3 235 32 17 8.6 4.7 | -12.5 9.5 225 40 21 8.5 4.6
17000 -11.4 11.5 230 31 16 8.0 4.4 | -11.3 11.7 225 39 20 8.6 4.7
16500 -10.2 13.6 230 30 16 8.0 4.4 | -10.0 14.0 220 37 19 8.5 4.7
16000 -9.0 15.8 230 29 15 8.8 4.8 | -8.7 16.3 220 36 18 8.9 4.9
15500 -7.7 18.1 230 28 14 8.9 4.9 | -7.4 18.7 220 34 17 9.0 4.9
15000 -6.4 20.5 225 27 14 9.1 5.0 | -6.1 21.0 220 32 17 8.7 4.8
14500 -5.0 23.0 225 26 13 9.2 5.1 | -4.8 23.4 220 30 15 8.4 4.6
14000 -3.6 25.5 225 24 13 9.1 5.0 | -3.6 25.5 215 28 14 8.4 4.6
13500 -2.3 27.9 220 23 12 8.4 4.6 | -2.4 27.7 215 25 13 8.5 4.7
13000 -1.1 30.0 220 21 11 8.4 4.6 | -1.1 30.0 215 23 12 8.6 4.7
12500 0.1 32.2 215 19 10 8.3 4.6 | 0.1 32.2 215 20 10 7.4 4.0
12000 1.4 34.5 210 17 9 8.4 4.6 | 1.2 34.2 220 17 9 7.5 4.1
11500 3.1 37.6 200 14 7 7.9 4.4 | 2.2 36.0 220 14 7 6.9 3.8
11000 4.3 39.7 190 12 6 7.6 4.2 | 3.2 37.8 230 10 5 7.1 3.9
10500 5.3 41.5 180 11 6 6.5 3.6 | 4.1 39.4 245 8 4 5.7 3.1
10250 5.9 42.6 175 10 5 9.8 5.4 | 4.9 40.8 265 6 3 7.6 4.2
10000 6.7 44.1 170 10 5 10.9 6.0 | 5.6 42.1 295 7 3 8.7 4.7
9750 7.4 45.3 165 9 5 8.1 4.4 | 6.1 43.0 310 7 4 6.6 3.6
9500 8.0 46.4 160 8 4 8.2 4.5 | 6.6 43.9 320 8 4 6.7 3.7
9250 8.6 47.5 155 8 4 9.2 5.0 | 7.1 44.8 330 9 5 7.4 4.0
9000 9.3 48.7 150 7 4 9.7 5.3 | 7.7 45.9 335 11 6 8.1 4.4
8750 10.0 50.0 145 7 3 8.8 4.8 | 8.2 46.8 345 12 6 7.8 4.3
8500 10.6 51.1 140 6 3 9.1 5.0 | 8.8 47.8 350 14 7 8.0 4.4
8250 11.3 52.3 135 5 3 8.6 4.7 | 9.4 48.9 350 16 8 7.6 4.1
8000 11.9 53.4 135 5 3 8.6 4.7 | 9.9 49.8 355 18 9 6.8 3.8
7750 12.6 54.7 130 4 2 9.6 5.3 | 10.4 50.7 355 20 10 7.4 4.0
7500 13.3 55.9 125 4 2 10.2 5.6 | 11.0 51.8 360 21 11 8.2 4.5
7250 14.1 57.4 115 4 2 9.4 5.1 | 11.5 52.7 360 23 12 7.2 4.0
7000 14.7 58.5 110 3 2 8.4 4.6 | 12.0 53.6 360 24 12 6.2 3.4
6750 15.4 59.7 105 3 2 9.7 5.3 | 12.5 54.5 360 25 13 8.4 4.6
6500 16.2 61.2 095 3 1 11.0 6.0 | 13.2 55.8 360 25 13 10.4 5.7
6250 16.9 62.4 085 2 1 9.8 5.4 | 13.9 57.0 355 25 13 8.0 4.4
6000 17.6 63.7 070 2 1 9.0 4.9 | 14.4 57.9 355 24 12 5.8 3.2
5750 18.3 64.9 060 2 1 9.7 5.3 | 14.9 58.8 355 22 11 9.4 5.2
5500 19.1 66.4 045 2 1 13.1 7.2 | 15.7 60.3 350 18 9 15.0 8.2
________________________________________________________________________________
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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