Soaring Guidance Issued by NWS Denver/Boulder, CO
000
UXUS97 KBOU 250019
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1818 MDT Wednesday, April 24, 2024
This forecast is for Thursday, April 25, 2024:
If the trigger temperature of 71.0 F/21.7 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1213 ft/min (6.2 m/s)
Maximum height of thermals.................. 17904 ft MSL (12606 ft AGL)
Forecast maximum temperature................... 77.0 F/25.5 C
Time of trigger temperature.................... 1130 MDT
Time of overdevelopment........................ 1600 MDT
Middle/high clouds during soaring window....... None
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 10749 ft MSL (5450 ft AGL)
Thermal soaring outlook for Friday 04/26....... 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)................ Neither
Potential height of wave....................... 53876 ft MSL (48578 ft AGL)
Wave soaring outlook for Friday 04/26.......... Poor
Remarks... Isolated storms Thursday afternoon, mainly eastern plains.
Sunrise/Sunset.................... 06:06:31 / 19:48:07 MDT
Total possible sunshine........... 13 hr 41 min 36 sec (821 min 36 sec)
Altitude of sun at 12:57:19 MDT... 63.76 degrees
Upper air data from numerical model forecast valid on 04/25/2024 at 0600 MDT
Freezing level.................. 12744 ft MSL (7446 ft AGL)
Convective condensation level... 16181 ft MSL (10883 ft AGL)
Lifted condensation level....... 16880 ft MSL (11582 ft AGL)
Lifted index.................... -2.1
K index......................... +18.1
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 -55.5 -67.9 255 56 29 0.5 0.2 M M M M M
45000 -55.0 -67.0 245 60 31 -1.8 -1.0 M M M M M
40000 -57.5 -71.5 240 63 33 -1.7 -0.9 M M M M M
38000 -56.1 -69.0 240 65 33 4.8 2.6 M M M M M
36000 -53.2 -63.8 235 66 34 4.8 2.6 M M M M M
34000 -49.4 -56.9 235 66 34 7.4 4.1 M M M M M
32000 -44.9 -48.8 235 61 32 7.4 4.1 M M M M M
30000 -40.5 -40.9 235 56 29 7.2 4.0 35.0 95.0 7.5 M M
29000 -38.3 -36.9 235 52 27 7.2 4.0 33.9 93.1 6.8 M M
28000 -36.2 -33.2 230 48 25 7.2 4.0 33.0 91.4 6.2 M M
27000 -34.0 -29.2 230 44 23 7.2 4.0 32.1 89.8 5.6 M M
26000 -31.9 -25.4 225 41 21 7.2 4.0 31.0 87.9 4.8 M M
25000 -29.7 -21.5 225 38 20 7.2 4.0 30.1 86.2 4.1 M M
24000 -27.5 -17.5 220 35 18 7.9 4.3 29.3 84.8 3.4 M M
23000 -25.1 -13.2 220 35 18 8.2 4.5 28.6 83.5 2.9 M M
22000 -22.7 -8.9 220 35 18 8.2 4.5 28.1 82.5 2.4 M M
21000 -20.3 -4.5 220 35 18 7.9 4.3 27.5 81.6 2.0 M M
20000 -17.9 -0.2 220 33 17 7.9 4.3 26.8 80.3 1.4 M M
19500 -16.7 1.9 220 32 17 7.9 4.3 26.5 79.7 1.1 M M
19000 -15.6 3.9 225 32 16 7.9 4.4 26.2 79.2 0.8 M M
18500 -14.4 6.1 225 31 16 7.6 4.1 25.9 78.6 0.5 M M
18000 -13.3 8.1 225 30 15 7.5 4.1 25.5 77.9 0.2 M M
17500 -11.7 10.9 230 28 14 7.2 3.9 24.9 76.8 -0.4 1163 5.9
17000 -10.7 12.7 230 26 13 7.1 3.9 24.4 76.0 -0.8 1117 5.7
16500 -9.6 14.7 230 23 12 7.3 4.0 24.0 75.2 -1.2 1070 5.4
16000 -8.5 16.7 235 21 11 7.7 4.2 23.6 74.5 -1.6 1022 5.2
15500 -7.3 18.9 235 18 9 7.6 4.2 23.3 73.9 -1.9 973 4.9
15000 -6.1 21.0 235 16 8 9.3 5.1 23.1 73.6 -2.1 920 4.7
14500 -4.7 23.5 230 14 7 9.2 5.0 23.0 73.4 -2.2 864 4.4
14000 -3.3 26.1 230 12 6 9.2 5.1 22.9 73.2 -2.3 808 4.1
13500 -1.9 28.6 235 12 6 9.2 5.1 22.8 73.1 -2.4 752 3.8
13000 -0.5 31.1 235 11 6 9.1 5.0 22.7 72.9 -2.5 695 3.5
12500 0.8 33.4 240 11 6 9.1 5.0 22.6 72.7 -2.6 639 3.2
12000 2.2 36.0 240 10 5 9.3 5.1 22.5 72.5 -2.7 584 3.0
11500 3.6 38.5 245 11 5 9.4 5.2 22.5 72.4 -2.8 526 2.7
11000 5.0 41.0 245 11 6 8.4 4.6 22.4 72.3 -2.9 469 2.4
10500 6.2 43.2 245 10 5 6.7 3.7 22.1 71.8 -3.2 420 2.1
10250 6.8 44.2 245 10 5 12.1 6.6 21.9 71.5 -3.3 395 2.0
10000 7.9 46.2 240 10 5 12.8 7.0 22.3 72.2 -3.0 354 1.8
9750 8.5 47.3 240 9 5 7.7 4.2 22.3 72.1 -3.1 327 1.7
9500 9.2 48.6 235 9 5 9.5 5.2 22.2 71.9 -3.1 300 1.5
9250 9.8 49.6 235 9 4 7.3 4.0 22.1 71.8 -3.2 273 1.4
9000 10.3 50.5 235 8 4 7.4 4.1 21.9 71.4 -3.5 251 1.3
8750 11.0 51.8 230 8 4 9.1 5.0 21.8 71.2 -3.6 224 1.1
8500 11.6 52.9 230 7 4 9.0 5.0 21.7 71.1 -3.6 197 1.0
8250 12.3 54.1 225 7 4 7.8 4.3 21.7 71.0 -3.7 170 0.9
8000 12.7 54.9 225 7 3 5.0 2.8 21.4 70.5 -4.0 149 0.8
7750 13.0 55.4 225 6 3 4.5 2.5 21.0 69.8 -4.4 132 0.7
7500 13.4 56.1 225 6 3 6.0 3.3 20.6 69.2 -4.8 114 0.6
7250 13.8 56.8 230 5 3 2.5 1.4 20.3 68.5 -5.2 96 0.5
7000 13.7 56.7 235 5 3 -1.7 -0.9 19.5 67.1 -6.0 91 0.5
6750 13.5 56.3 245 4 2 -2.4 -1.3 18.6 65.5 -7.0 89 0.5
6500 13.2 55.8 255 4 2 -3.6 -2.0 17.7 63.8 -8.0 90 0.5
6250 12.8 55.0 265 4 2 -5.8 -3.2 16.6 61.8 -9.1 94 0.5
6000 12.2 54.0 265 4 2 -8.2 -4.5 15.3 59.5 -10.5 105 0.5
5750 11.6 52.9 270 4 2 -5.1 -2.8 14.0 57.2 -11.9 115 0.6
5500 11.1 52.0 265 4 2 -12.8 -7.0 12.8 55.0 -13.2 124 0.6
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
04/25/2024 at 0900 MDT | 04/25/2024 at 1200 MDT
|
CAPE... +14.9 LI... +1.6 | CAPE... +126.9 LI... -0.5
CINH... -48.8 K Index... +11.8 | CINH... -12.5 K Index... +10.4
|
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 -54.0 -65.2 255 55 29 0.7 0.4 | -52.6 -62.7 250 52 27 1.3 0.7
45000 -53.2 -63.8 240 59 30 -2.9 -1.6 | -51.0 -59.8 240 59 30 -3.5 -1.9
40000 -57.0 -70.6 235 60 31 -2.6 -1.4 | -55.9 -68.6 220 62 32 -3.2 -1.8
38000 -56.1 -69.0 235 63 32 4.3 2.4 | -55.5 -67.9 220 65 33 3.3 1.8
36000 -53.1 -63.6 235 67 35 4.3 2.4 | -53.5 -64.3 220 68 35 3.3 1.8
34000 -49.9 -57.8 235 68 35 7.3 4.0 | -50.7 -59.3 220 69 36 7.5 4.1
32000 -45.5 -49.9 230 64 33 7.3 4.0 | -46.2 -51.2 220 68 35 7.6 4.2
30000 -41.0 -41.8 230 59 30 7.7 4.2 | -41.6 -42.9 220 65 33 7.6 4.2
29000 -38.7 -37.7 230 56 29 7.7 4.2 | -39.3 -38.7 220 61 32 7.6 4.2
28000 -36.4 -33.5 230 53 27 7.7 4.2 | -37.0 -34.6 220 58 30 7.6 4.2
27000 -34.1 -29.4 225 50 26 7.2 4.0 | -34.7 -30.5 220 55 28 8.0 4.4
26000 -31.9 -25.4 225 47 24 7.2 4.0 | -32.3 -26.1 220 51 26 8.1 4.5
25000 -29.8 -21.6 225 44 23 7.2 4.0 | -29.9 -21.8 215 48 25 8.1 4.5
24000 -27.6 -17.7 220 41 21 7.3 4.0 | -27.4 -17.3 215 45 23 7.7 4.2
23000 -25.4 -13.7 220 39 20 7.3 4.0 | -25.3 -13.5 215 42 21 6.9 3.8
22000 -23.2 -9.8 220 37 19 7.3 4.0 | -23.3 -9.9 215 38 20 6.9 3.8
21000 -21.0 -5.8 220 35 18 8.0 4.4 | -21.2 -6.2 220 35 18 7.1 3.9
20000 -18.6 -1.5 220 33 17 8.1 4.4 | -18.5 -1.3 220 30 16 7.3 4.0
19500 -16.8 1.8 220 31 16 8.1 4.4 | -17.5 0.5 220 28 14 7.3 4.0
19000 -15.6 3.9 225 30 15 8.1 4.5 | -16.4 2.5 220 26 13 7.3 4.0
18500 -14.4 6.1 225 29 15 7.8 4.3 | -15.2 4.6 220 24 12 8.0 4.4
18000 -13.2 8.2 225 27 14 7.9 4.3 | -14.1 6.6 220 22 11 8.0 4.4
17500 -12.1 10.2 225 26 13 7.8 4.3 | -12.9 8.8 220 20 11 8.0 4.4
17000 -10.9 12.4 225 24 12 7.8 4.3 | -11.7 10.9 220 18 9 8.1 4.4
16500 -9.8 14.4 225 22 11 7.9 4.4 | -10.5 13.1 215 16 8 8.1 4.4
16000 -8.6 16.5 220 20 10 8.5 4.7 | -9.2 15.4 215 15 8 8.8 4.9
15500 -7.3 18.9 220 19 10 8.4 4.6 | -7.9 17.8 215 14 7 8.8 4.8
15000 -6.0 21.2 215 18 9 8.9 4.9 | -6.6 20.1 210 13 7 9.2 5.0
14500 -4.7 23.5 215 17 9 8.8 4.9 | -5.2 22.6 210 13 7 9.2 5.1
14000 -3.4 25.9 215 16 8 8.9 4.9 | -3.9 25.0 210 13 6 9.2 5.0
13500 -2.1 28.2 215 16 8 8.9 4.9 | -2.5 27.5 205 12 6 9.2 5.0
13000 -0.8 30.6 215 15 8 8.8 4.8 | -1.1 30.0 205 12 6 9.2 5.0
12500 0.5 32.9 215 14 7 8.8 4.8 | 0.2 32.4 205 12 6 9.3 5.1
12000 1.8 35.2 210 13 7 8.9 4.9 | 1.6 34.9 200 11 6 9.3 5.1
11500 3.2 37.8 215 12 6 8.9 4.9 | 3.0 37.4 200 11 5 9.3 5.1
11000 4.5 40.1 220 12 6 8.3 4.6 | 4.4 39.9 195 10 5 9.0 4.9
10500 5.7 42.3 225 11 6 6.8 3.8 | 5.7 42.3 190 9 5 7.9 4.4
10250 6.2 43.2 225 11 6 10.4 5.7 | 6.3 43.3 190 9 5 9.9 5.4
10000 7.2 45.0 230 11 5 11.3 6.2 | 7.1 44.8 190 9 5 11.1 6.1
9750 7.8 46.0 230 10 5 8.1 4.4 | 7.9 46.2 190 8 4 9.5 5.2
9500 8.5 47.3 235 10 5 8.5 4.7 | 8.6 47.5 190 8 4 9.3 5.1
9250 9.1 48.4 235 10 5 9.1 5.0 | 9.3 48.7 190 8 4 9.3 5.1
9000 9.8 49.6 235 10 5 9.1 5.0 | 9.9 49.8 190 7 4 9.1 5.0
8750 10.4 50.7 235 9 5 8.2 4.5 | 10.6 51.1 190 7 3 9.0 5.0
8500 11.1 52.0 235 9 5 8.5 4.7 | 11.3 52.3 190 6 3 9.1 5.0
8250 11.7 53.1 240 9 5 8.0 4.4 | 11.9 53.4 190 6 3 9.1 5.0
8000 12.2 54.0 240 9 4 6.2 3.4 | 12.6 54.7 190 5 3 8.8 4.9
7750 12.6 54.7 235 8 4 5.7 3.1 | 13.2 55.8 185 4 2 8.9 4.9
7500 13.1 55.6 235 8 4 6.9 3.8 | 13.9 57.0 185 4 2 9.4 5.1
7250 13.5 56.3 230 7 4 4.4 2.4 | 14.6 58.3 180 3 2 8.9 4.9
7000 13.7 56.7 230 6 3 0.6 0.3 | 15.2 59.4 175 3 1 7.8 4.3
6750 13.7 56.7 230 6 3 1.3 0.7 | 15.8 60.4 165 2 1 9.6 5.3
6500 13.8 56.8 230 5 2 2.5 1.4 | 16.6 61.9 160 2 1 11.3 6.2
6250 13.9 57.0 230 4 2 1.4 0.8 | 17.4 63.3 155 1 1 10.7 5.9
6000 13.9 57.0 220 3 2 0.3 0.2 | 18.2 64.8 150 1 1 11.0 6.1
5750 13.9 57.0 210 3 2 2.5 1.4 | 19.0 66.2 135 1 1 9.9 5.4
5500 14.2 57.6 220 2 1 10.1 5.6 | 19.8 67.6 140 1 0 15.4 8.4
04/25/2024 at 1500 MDT | 04/25/2024 at 1800 MDT
|
CAPE... +260.6 LI... -1.2 | CAPE... +220.6 LI... -1.1
CINH... -11.9 K Index... +21.3 | CINH... -106.8 K Index... +24.6
|
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 -52.3 -62.1 250 48 25 2.1 1.2 | -52.0 -61.6 245 46 24 2.2 1.2
45000 -49.4 -56.9 240 50 26 -2.5 -1.4 | -48.9 -56.0 240 42 21 -1.0 -0.6
40000 -53.0 -63.4 220 59 30 -2.4 -1.3 | -50.3 -58.5 225 41 21 -0.9 -0.5
38000 -53.2 -63.8 215 63 32 1.5 0.8 | -50.5 -58.9 220 40 21 0.0 0.0
36000 -52.3 -62.1 210 64 33 1.5 0.8 | -50.5 -58.9 210 37 19 0.0 0.0
34000 -50.7 -59.3 210 66 34 6.7 3.7 | -50.0 -58.0 205 34 18 4.7 2.6
32000 -46.6 -51.9 210 66 34 6.8 3.7 | -47.4 -53.3 205 26 13 4.4 2.4
30000 -42.5 -44.5 210 64 33 6.8 3.7 | -44.2 -47.6 200 19 10 8.8 4.8
29000 -40.5 -40.9 210 59 30 6.8 3.7 | -41.6 -42.9 200 17 9 8.7 4.8
28000 -38.4 -37.1 210 53 27 6.8 3.7 | -39.0 -38.2 200 15 8 8.7 4.8
27000 -36.4 -33.5 210 47 24 7.2 4.0 | -36.4 -33.5 200 13 7 8.6 4.7
26000 -34.0 -29.2 210 42 22 7.9 4.3 | -33.8 -28.8 195 14 7 8.5 4.7
25000 -31.7 -25.1 205 37 19 7.9 4.3 | -31.3 -24.3 195 15 8 8.5 4.7
24000 -29.3 -20.7 205 32 17 8.0 4.4 | -28.7 -19.7 190 16 8 8.6 4.7
23000 -26.8 -16.2 205 30 15 8.3 4.6 | -26.4 -15.5 195 18 9 7.6 4.2
22000 -24.4 -11.9 205 27 14 8.3 4.6 | -24.1 -11.4 200 21 11 7.6 4.2
21000 -21.9 -7.4 210 25 13 8.1 4.5 | -21.8 -7.2 200 24 12 7.8 4.3
20000 -18.9 -2.0 205 22 11 8.0 4.4 | -19.4 -2.9 200 24 12 8.1 4.5
19500 -17.7 0.1 205 21 11 8.0 4.4 | -18.2 -0.8 195 24 12 8.2 4.5
19000 -16.6 2.1 205 20 10 8.0 4.4 | -17.0 1.4 195 23 12 8.2 4.5
18500 -15.4 4.3 200 19 10 8.3 4.6 | -15.2 4.6 195 23 12 8.4 4.6
18000 -14.1 6.6 195 18 9 8.4 4.6 | -14.0 6.8 195 23 12 8.6 4.7
17500 -12.9 8.8 190 17 9 8.6 4.7 | -12.7 9.1 190 22 11 8.6 4.7
17000 -11.6 11.1 185 17 9 9.0 4.9 | -11.5 11.3 190 22 11 8.0 4.4
16500 -10.2 13.6 185 16 8 9.0 4.9 | -10.3 13.5 190 21 11 8.1 4.4
16000 -8.9 16.0 185 15 8 9.4 5.2 | -9.1 15.6 190 20 11 8.2 4.5
15500 -7.5 18.5 180 15 8 9.4 5.2 | -7.9 17.8 190 19 10 8.2 4.5
15000 -6.1 21.0 175 14 7 9.4 5.2 | -6.7 19.9 190 18 9 8.5 4.7
14500 -4.7 23.5 170 13 7 9.4 5.1 | -5.4 22.3 185 16 8 8.8 4.9
14000 -3.3 26.1 170 12 6 9.3 5.1 | -4.1 24.6 180 14 7 8.9 4.9
13500 -1.9 28.6 165 11 6 9.1 5.0 | -2.8 27.0 180 12 6 8.8 4.9
13000 -0.6 30.9 160 10 5 9.2 5.0 | -1.5 29.3 175 10 5 8.9 4.9
12500 0.8 33.4 155 10 5 9.3 5.1 | -0.2 31.6 170 8 4 8.5 4.6
12000 2.2 36.0 150 9 5 9.3 5.1 | 1.0 33.8 160 6 3 8.6 4.7
11500 3.6 38.5 145 9 4 9.3 5.1 | 2.2 36.0 145 4 2 7.7 4.2
11000 5.0 41.0 140 8 4 9.4 5.1 | 3.4 38.1 095 2 1 7.9 4.3
10500 6.3 43.3 135 8 4 9.1 5.0 | 4.4 39.9 040 3 1 6.8 3.7
10250 7.0 44.6 135 7 4 9.4 5.1 | 4.9 40.8 025 4 2 7.3 4.0
10000 7.7 45.9 130 7 4 9.6 5.3 | 5.5 41.9 015 5 2 8.1 4.4
9750 8.4 47.1 130 7 4 9.7 5.3 | 6.1 43.0 005 6 3 7.5 4.1
9500 9.2 48.6 130 7 4 10.0 5.5 | 6.6 43.9 355 7 3 6.9 3.8
9250 9.9 49.8 125 7 3 9.8 5.4 | 7.1 44.8 350 8 4 7.0 3.8
9000 10.6 51.1 125 7 3 9.2 5.1 | 7.7 45.9 340 9 5 6.9 3.8
8750 11.3 52.3 125 7 3 9.3 5.1 | 8.2 46.8 335 10 5 6.6 3.6
8500 12.0 53.6 120 6 3 9.6 5.3 | 8.6 47.5 330 12 6 6.3 3.5
8250 12.7 54.9 120 6 3 9.7 5.3 | 9.1 48.4 325 13 7 6.2 3.4
8000 13.5 56.3 115 6 3 9.1 5.0 | 9.6 49.3 320 15 8 6.9 3.8
7750 14.1 57.4 115 6 3 9.4 5.1 | 10.1 50.2 315 16 8 6.6 3.6
7500 14.9 58.8 110 6 3 9.9 5.4 | 10.5 50.9 315 17 9 5.7 3.1
7250 15.6 60.1 110 6 3 10.3 5.6 | 10.9 51.6 310 19 10 6.0 3.3
7000 16.3 61.3 105 6 3 8.3 4.6 | 11.4 52.5 305 20 10 5.9 3.3
6750 16.9 62.4 105 6 3 8.5 4.7 | 11.8 53.2 305 20 10 8.4 4.6
6500 17.7 63.9 100 5 3 10.6 5.8 | 12.6 54.7 305 20 10 10.2 5.6
6250 18.4 65.1 100 5 3 10.2 5.6 | 13.3 55.9 305 20 10 9.8 5.4
6000 19.2 66.6 095 5 3 10.3 5.6 | 14.0 57.2 305 20 10 9.0 4.9
5750 20.1 68.2 095 5 3 14.8 8.1 | 14.7 58.5 305 19 10 11.3 6.2
5500 21.5 70.7 090 5 2 22.8 12.5 | 15.7 60.3 305 17 9 17.7 9.7
________________________________________________________________________________
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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